TOXICOLOGICAL PROFILE FOR
 

HYDRAULIC FLUIDS
 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
 

Public Health Service
 

Agency for Toxic Substances and Disease Registry
 

September 1997 
HYDRAULIC FLUIDS ii 

DISCLAIMER 

The use of company or product name(s) is for identification only and does not imply endorsement by the 

Agency for Toxic Substances and Disease Registry. 
HYDRAULIC FLUIDS iii 

UPDATE STATEMENT 

A draft toxicological profile for hydraulic fluids was released in June 1994. This edition supersedes any 

previously released draft or final profile. 

Toxicological profiles are revised and republished as necessary, but no less than once every three years. For 

information regarding the update status of previously released profiles, contact ATSDR at: 

Agency for Toxic Substances and Disease Registry
 

Division of Toxicology/Toxicology Information Branch
 

1600 Clifton Road NE, E-29
 

Atlanta, Georgia 30333
 


vi 

*Legislative Background 

The toxicological profiles are developed in response to the Superfund Amendments and 

Reauthorization Act (SARA) of 1986 (Public Law 99-499) which amended the Comprehensive 

Environmental Response, Compensation, and Liability Act of 1980 (CERCLA or Superfund). Section 211 of 

SARA also amended Title 10 of the U. S . Code, creating the Defense Environmental Restoration Program. 

Section 2704(a) of Title 10 of the U. S. Code directs the Secretary of Defense to notify the Secretary of Health 

and Human Services of not less than 25 of the most commonly found unregulated hazardous substances at 

defense facilities. Section 2704(b) of Title 10 of the U. S. Code directs the Administrator of the Agency for 

Toxic Substances and Disease Registry (ATSDR) to prepare a toxicological profile for each substance on the list 

provided by the Secretary of Defense under subsection (b). 
HYDRAULIC FLUIDS vii 

CONTRIBUTORS 

CHEMICAL MANAGER(S)/AUTHORS(S): 

M. Olivia Harris, M.A.
 

ATSDR, Division of Toxicology, Atlanta, GA
 

Peter McClure, Ph.D.; Lisa Ingerman, Ph.D.
 

Syracuse Research Corporation, Syracuse, NY
 

Robert L. Chessin, M.S.P.H.
 

Research Triangle Institute, Research Triangle Park, NC
 

James J. Corcoran, Ph.D.
 

Research Triangle Institute, Research Triangle Park, NC
 

THE PROFILE HAS UNDERGONE THE FOLLOWING ATSDR INTERNAL REVIEWS: 

1. Green Border Review. Green Border review assures consistency with ATSDR policy. 

2 . Health Effects Review. The Health Effects Review Committee examines the health effects chapter of 

each profile for consistency and accuracy in interpreting health effects and classifying end points. 

3 . Minimal Risk Level Review. The Minimal Risk Level Workgroup considers issues relevant to 

substance-specific minimal risk levels (MRLs), reviews the health effects database of each profile, 

and makes recommendations for derivation of MRLs. 

4 . Data Needs Review. The Research Implementation Branch reviews data needs sections to assure 

consistency across profiles and adherence to instructions in the Guidance. 

HYDRAULIC FLUIDS ix 

PEER REVIEW 

A peer review panel was assembled for hydraulic fluids. The panel consisted of the following members: 

1. Dr. C. Carson Conaway, Research Scientist, Mahopac, NY; 

2. Dr. Arthur Gregory, Private Consultant, Techto Enterprises, Sterling, VA; 

3. Dr. James Hughes, Private Consultant, Piedmont, CA; 

4. Dr. Harlee Strauss, Private Consultant, H. Strauss Associates, Inc., Boston, MA; 

5. Mr. Edmond Kinkead, Research Scientist, Dayton, OH; and 

6. Dr. Charles Ward, Private Consultant, Pittsburgh, PA. 

These experts collectively have knowledge of hydraulic fluids’s physical and chemical properties, 

toxicokinetics, key health end points, mechanisms of action, human and animal exposure, and quantification of 

risk to humans. All reviewers were selected in conformity with the conditions for peer review specified in 

Section 104(1)( 13) of the Comprehensive Environmental Response, Compensation, and Liability Act, as 

amended. 

Scientists from the Agency for Toxic Substances and Disease Registry (ATSDR) have reviewed the peer 

reviewers’ comments and determined which comments will be included in the profile. A listing of the peer 

reviewers’ comments not incorporated in the profile, with a brief explanation of the rationale for their 

exclusion, exists as part of the administrative record for this compound. A list of databases reviewed and a 

list of unpublished documents cited are also included in the administrative record. 

The citation of the peer review panel should not be understood to imply its approval of the profile’s final 

content. The responsibility for the content of this profile lies with the ATSDR. 









HYDRAULIC FLUIDS 1 

1. PUBLIC HEALTH STATEMENT 

This public health statement tells you about hydraulic fluids and the effects of exposure. 

The Environmental Protection Agency (EPA) identifies the most serious hazardous waste sites in 

the nation. These sites make up the National Priorities List (NPL) and are the sites targeted for 

long-term federal cleanup. Hydraulic fluids have been found in at least 10 of the 1,428 current or 

former NPL sites. However, it’s unknown how many NPL sites have been evaluated for these 

substances. As more sites are evaluated, the sites with hydraulic fluids may increase. This is 

important because exposure to these substances may harm you and because these sites may be 

sources of exposure. 

When a substance is released from a large area, such as an industrial plant, or from a container, 

such as a drum or bottle, it enters the environment. This release does not always lead to 

exposure. You are exposed to a substance only when you come in contact with it. You may be 

exposed by breathing, eating, or drinking the substance or by skin contact. 

If you are exposed to hydraulic fluids, many factors determine whether you’ll be harmed. These 

factors include the dose (how much), the duration (how long), and how you come in contact with 

it. You must also consider the other chemicals you’re exposed to and your age, sex, diet, family 

traits, lifestyle, and state of health. 

1 .1 WHAT ARE HYDRAULIC FLUIDS? 

Hydraulic fluids are a very large class of materials that are used in machines and equipment to. 

transfer pressure from one point to another. They are used in many ways including all fluids for 

car automatic transmissions, brakes, and power steering. Hydraulic fluids are also used in many 

machines like tractors and other farm equipment, forklift trucks, bulldozers, and other 

construction equipment, and airplanes. In industry, hydraulic fluids are used in machines that 

push, lift, pull, turn, and hold things. This profile covers only three of the many types of hydraulic 
HYDRAULIC FLUIDS 2 

1. PUBLIC HEALTH STATEMENT 

fluids: (1) mineral oil, (2) organophosphate ester, and (3) polyalphaolefin. These types are 

among the most commonly used today. The trade names of typical hydraulic fluids covered in this 

profile include Durad®, Fyrquel®, Skydrol®, Houghton-Safe®, Pydraul®, Reofose, Reolube®, and 

Quintolubric®. Hydraulic fluids used in cars are not specifically covered in this profile. 

Some hydraulic fluids have a bland oily smell, while others have no smell. Mineral oil and 

polyalphaolefm hydraulic fluids are mixtures that have oil in them and will burn. Oil-in-water 

hydraulic fluids (a special type of mineral oil hydraulic fluid) do not burn because they contain 

water. Organophosphate ester hydraulic fluids are mostly made without oil and will not burn 

unless there is a flame directly on them; once the flame is removed, these fluids will stop burning. 

Because they do not burn, organophosphate ester hydraulic fluids are used in airplanes and other 

places where fues are very undesirable. 

Mineral oil hydraulic fluids are produced from crude oil. Organophosphate ester and 

polyalphaolefin hydraulic fluids are manufactured. All hydraulic fluids contain many ingredients 

which reduce wear, make the fluid flow better, and make it thinner when it is cold. More than 

200 million gallons of hydraulic fluids are sold each year in the United States. See Chapters 3 and 

4 for more information on hydraulic fluids. 

1.2 	 WHAT HAPPENS TO HYDRAULIC FLUIDS WHEN THEY ENTER THE 

ENVIRONMENT? 

Hydraulic fluids can enter the environment from spills and leaks in machines that use them and 

from leaky storage tanks. If spilled on soil, some of the ingredients in the hydraulic fluids mixture 

may stay on the top, while others may sink into the groundwater. How fast the ingredients move 

through soil depends on many things. These include how much is spilled, how much rain falls on 

the spill, and the type of soil (for example, hydraulic fluids will move quickly in sandy soil, but will 

move slower in heavy clay). In water, some ingredients of hydraulic fluids will transfer to the 

bottom and stay there. Fish may contain some hydraulic fluid ingredients if they live near places 

that make or use a lot of it. Eventually, the ingredients of hydraulic fluids are degraded in the 

environment, but complete degradation may take more than a year. Scientists know a little about 
HYDRAULIC FLUIDS 3 

1. PUBLIC HEALTH STATEMENT
 

how some of the ingredients in hydraulic fluids break down in the environment, but they know 

almost nothing about how toxic these breakdown products are. See Chapters 4 and 5 for more 

information on what happens to hydraulic fluids in the environment. 

1.3 HOW MIGHT I BE EXPOSED TO HYDRAULIC FLUIDS? 

Exposures to hydraulic fluids occur mainly in workers using hydraulic equipment and in people 

who work on cars or tractors that use the fluids. Most people are exposed when fluids spill or 

leak on the skin, when the fluid is changed, or when the fluid reservoirs are filled. Low levels of 

hydraulic fluids may occur in the air near machines that use them. Understanding environmental 

levels of hydraulic fluids is very difficult because the ingredients in hydraulic fluids are used in 

many products other than hydraulic fluids. For example, mineral oil is an ingredient in both motor 

oil and mineral oil hydraulic fluids. In the environment, mineral oil from both sources would 

appear to be the same. Polyalphaolefin hydraulic fluids have chemical components and potential 

applications similar to mineral oil hydraulic fluids. 

The ingredients in organophosphate ester hydraulic fluids also have many uses, but are usually not 

detected in the environment. They do not have as many uses as mineral oils and polyalphaoletins. 

When detected, concentrations of organophosphate esters range from 1 to 20 parts per billion 

(ppb) in water, 0.0002 to 1.31 ppb in drinking water, and less than 100 to greater than 

6,300,000 ppb in sediments. In general, organophosphate esters are found near places where they 

are manufactured. People most likely to be exposed to hydraulic fluids include car, truck, tractor, 

industrial equipment, and airplane mechanics and repair technicians, and maintenance workers in 

heavy industry like car assembly plants, foundries, steel mills, paper mills, and plants that 

manufacture appliances or other large or small household or commercial items. Polyalphaolefin 

hydraulic fluids are often used in military equipment. See Chapter 5 for more information on how 

you might be exposed to hydraulic fluids. 
HYDRAULIC FLUIDS 4 

1. PUBLIC HEALTH STATEMENT 

1.4 HOW CAN HYDRAULIC FLUIDS ENTER AND LEAVE MY BODY? 

Very little is known about how mineral oil hydraulic fluids, polyalphaolefin hydraulic fluids, and 

organophosphate ester hydraulic fluids enter and leave your body. Some information exists about 

how some of the chemical components in the organophosphate ester hydraulic fluids enter and 

leave your body. 

We know that chemical components of mineral oil hydraulic fluids can enter the body if you 

swallow them or they come in contact with your skin because health effects have occurred in 

people after they swallowed or had prolonged skin contact with certain mineral oil hydraulic 

fluids. Health effects have occurred in animals after they breathed, swallowed, or had skin 

contact with organophosphate ester hydraulic fluids. We do not know if mineral oil hydraulic 

fluids or polyalphaolefin hydraulic fluids will enter your body from your lungs if you breathe them 

as vapor or oil mist. 

We know that some chemical components of organophosphate ester hydraulic fluids can enter 

your body from your lungs if you breathe them. Some organophosphate esters rapidly enter your 

body. Certain components of organophosphate ester hydraulic fluids are found in blood and urine 

within 1 hour of having them on your skin. Within 6 hours after animals swallow large amounts 

of certain components of organophosphate ester hydraulic fluids, they enter the blood and are 

found throughout the body, especially in fat. Organophosphate esters leave the body in the urine 

and feces within several days. More information can be found in Chapter 2. 

1.5 HOW CAN HYDRAULIC FLUIDS AFFECT MY HEALTH? 

This toxicological profile discusses only three classes of hydraulic fluids: mineral oil hydraulic 

fluids, polyalphaolefin hydraulic fluids, and organophosphate ester hydraulic fluids. The classes 

are based on the major chemicals found in the hydraulic fluids. However, hydraulic fluids are 

often complex mixtures of many chemical components. A particular hydraulic fluid can differ in 
HYDRAULIC FLUIDS 5 

1. PUBLIC HEALTH STATEMENT 

its chemical components from another hydraulic fluid even if the two fluids are in the same class. 

Thus, effects of exposure may differ. 

Very little is known about how mineral oil hydraulic fluids and polyalphaolefin hydraulic fluids 

will affect your health. There are reports of health effects in people exposed to these classes of 

hydraulic fluids. After drinking mineral oil hydraulic fluid, a child developed pneumonia and 

bleeding in the intestines and then died. A man whose hands and forearms were heavily exposed 

to mineral oil hydraulic fluids in his job developed weakness in his hands. This effect was 

probably caused by one of the organophosphate ester additives of the mineral oil hydraulic fluid. 

The skin and eyes of animals were red and swollen after contact with certain mineral oil hydraulic 

fluids and polyalphaolefin hydraulic fluids. Animals breathing very high levels of polyalphaolefin 

hydraulic fluids became drowsy and had congested lungs and trouble breathing. We do not know 

if mineral oil hydraulic fluids or polyalphaolefin hydraulic fluids will cause birth defects, 

reproductive effects, or cancer. 

There have been reports of people being poisoned from swallowing cooking oil or medicines 

contaminated with organophosphate esters. Outbreaks of brain, nerve, and muscle problems due 

to organophosphate contamination have happened in the United States and other countries. If 

you get certain organophosphate ester hydraulic fluids on your skin, it may be irritated and turn 

red. There are no reports of people breathing or swallowing this type of fluid. Studies in animals 

suggest that if you breathe or swallow large amounts of certain organophosphate ester hydraulic 

fluids, you may have nervous system problems. Certain organophosphate ester hydraulic fluids 

affect the nervous system of animals in two different ways. The first type of effect occurs within a 

few hours of breathing, swallowing, or skin contact. The organophosphate ester part of the 

hydraulic fluid rapidly inhibits the activity of important enzymes in the nervous system causing 

multiple symptoms including tremors, sweating, diarrhea, and difficulty breathing. The second 

effect involves damage to nerves. The symptoms of this type of damage are general weakness, 

weakness of the arms and legs, and paralysis. These symptoms of nerve damage can occur 

several weeks after exposure has stopped. If you have been exposed once to organophosphate 

ester hydraulic fluids, the symptoms of enzyme inhibition will disappear before the weakness 
 

 

HYDRAULIC FLUIDS 6 

1. PUBLIC HEALTH STATEMENT
 

occurs. Not all types of these fluids cause both types of nervous system damage. In animal 

studies, not all animals that have symptoms of enzyme inhibition have nerve damage. Both of 

these types of nervous system damage can occur after one or several exposures. 

Cows eating grass containing organophosphate ester hydraulic fluid had difficulty producing milk 

for their young. We do not know if this will also occur in people. We do not know if 

organophosphate ester hydraulic fluids will cause birth defects, affect fertility, or cause cancer. 

The Department of Health and Human Services (DHHS), the International Agency for Research 

on Cancer (IARC), and EPA have not classified mineral oil hydraulic fluids, polyalphaolefin 

hydraulic fluids, and organophosphate ester hydraulic fluids for carcinogenic effects. 

1.6 	 IS THERE A MEDICAL TEST TO DETERMINE WHETHER I HAVE BEEN 

EXPOSED TO HYDRAULIC FLUIDS? 

Hydraulic fluids themselves cannot be measured in blood, urine, or feces, but certain chemicals in 

them can be measured. Aliphatic hydrocarbons, which are major components of mineral oil 

hydraulic fluids and polyalphaolefin hydraulic fluids, can be detected in the feces. Certain 

components of organophosphate ester hydraulic fluids leave the body in urine. Some of these 

fluids inhibit the enzyme cholinesterase. Cholinesterase activity in blood can be measured. 

Because many other chemicals also inhibit cholinesterase activity in blood, this test is not specific 

for organophosphate ester hydraulic fluids. This test is not available at most doctor’s offices, but 

can be arranged at any hospital laboratory. See Chapters 2 and 6 for more information. 
 

HYDRAULIC FLUIDS 7 

1. PUBLIC HEALTH STATEMENT
 

1.7	 WHAT RECOMMENDATIONS HAS THE FEDERAL GOVERNMENT MADE TO 

PROTECT HUMAN HEALTH? 

Federal government recommendations exist to protect people’s health from mineral oil hydraulic fluids. 

Mineral oil is the major chemical component of mineral oil hydraulic fluids. Mineral oil belongs to a 

larger class of chemicals called petroleum distillates. The Occupational Safety and Health 

Administration (OSHA) regulates petroleum distillate and mineral oil mist levels in workplace air. 

The occupational exposure limits for an 8-hour workday, 40-hour workweek are 2,000 milligrams per 

cubic meter (mg/m3

) in air for petroleum distillates and 5 mg/m3 for mineral oil mists. The National 

Institute for Occupational Safety and Health (NIOSH) recommends an exposure limit of 350 mg/m3

 of 

petroleum distillates for a 10-hour workday, 40-hour workweek. 

1.8 WHERE CAN I GET MORE INFORMATION? 

If you have any more questions or concerns, please contact your community or state health or 

environmental quality department or 

Agency for Toxic Substances and Disease Registry
 

Division of Toxicology
 

1600 Clifton Road NE, Mailstop E-29
 

Atlanta, GA 30333
 

This agency can also provide you with information on the location of occupational and environmental 

health clinics. These clinics specialize in the recognition, evaluation, and treatment of illness 

resulting from exposure to hazardous substances. 

HYDRAULIC FLUIDS 9 

2. HEALTH EFFECTS 

2.1 INTRODUCTION 

The primary purpose of this chapter is to provide public health officials, physicians, toxicologists, and other 

interested individuals and groups with an overall perspective of the toxicology of hydraulic fluids. It contains 

descriptions and evaluations of toxicological studies and epidemiological investigations and provides 

conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health. 

As discussed in Chapters 3,4, and 5 of this profile, hydraulic fluids are materials that transmit energy in 

fluid-filled, pressurized mechanical systems such as automotive automatic transmissions, vehicular brake 

equipment, power steering equipment, and hydrostatic drive systems used in agricultural, construction, 

mining, and aircraft equipment and machinery. Hydraulic fluids are defined primarily on an operational 

basis. Thus, any fluid, regardless of chemical composition, that is used to transmit pressure in a closed system is 

a hydraulic fluid. Based on chemical and functional properties, hydraulic fluids can be divided into 

sevenchemical classes: phosphate esters, mineral-oil-in-water and water- in-oil fluids, polyalphaolefin 

oligomers, polyhalohydrocarbons, polyglycols, silicate esters, and silicones. This profile focuses on three classes 

of hydraulic fluids: mineral-oil-based hydraulic fluids, polyalphaolefins, and organophosphate esters (Moller 

1989; U.S. Air Force 1989; Wills 1980). Some of these fluids have special applications in industry and the 

military and may be found at hazardous waste sites. Automobile hydraulic fluids (brake, transmission, or power 

steering fluids) are not specifically addressed in this profile. Some of the specific fluids discussed in this profile 

are no longer manufactured, but may nonetheless be at hazardous waste sites. 

Mineral-oil based hydraulic fluids (including fire-resistant mixtures of mineral oil and water) have been 

estimated to comprise 98% of the world demand for hydraulic fluids (Wills 1980). These fluids are made 

from dewaxed petroleum-based crude oils that are blended with additives such as corrosion inhibitors (e.g., 

fatty acids), oxidation inhibitors (e.g., phenols, amines, and sulfides), defoamers (e.g., silicone oils), and 

antiwear additives (e:g., organophosphate esters) (FMC 1991c, 1991d, 1992a, 1992b; Moller1989). Thus, 

mineral-oil-based hydraulic fluids are complex mixtures of aliphatic and aromatic hydrocarbons to which 

other compounds have been added. The chemical composition of these fluids varies with manufacturer and 

depends on the source of the crude oil, the degree and type of refining applied to the crude oil, and the amount 

and types of compounds added for operational purposes. Mineral-oil-based hydraulic fluids are widely used in 

hydrostatic machines, hydrodynamic couplings, automatic transmissions, and tractors. Hydraulic systems 
HYDRAULIC FLUIDS 10 

2. HEALTH EFFECTS 

used in situations where combustion is a danger (e.g., underground mining, foundries, and in welding 

equipment) often contain oil-in-water emulsions (>80% water) or water-in-oil emulsions (>40% water) as 

fire-resistant hydraulic fluids (Moller 1989). 

Organophosphate esters are among the most widely used classes of synthetic compounds in hydraulic fluids. 

They are used as anti-wear additives in mineral oil hydraulic fluids and are significant components in certain 

fire-resistant hydraulic fluids (FMC 1991c, 1991 d, 1992a, 1992b; Wills 1980). Organophosphate esters have 

better fire resistance than mineral oils and are much better lubricants than water. Common types of 

organophosphate esters include tricresyl phosphates, isopropylated phenyl phosphates, tributyl phosphates, and 

tertiary butylated phenyl phosphates (Moller 1989; Wills 1980; Henrich 1995). Organophosphate ester hydraulic 

fluids and additives often contain mixtures of organophosphate esters. The only other synthetic compounds 

likely to have a wider use in hydraulic fluids are the polyalkylene glycols, which are widely used in the 

hydraulic brake systems of motor vehicles (Moller 1989; Wills 1980). The toxicological properties of two 

important polyalkylene glycols are discussed in the ATSDR technical report on ethylene glycol and propylene 

glycol (ATSDR 1993a). The polyalkylene glycols are not discussed in this profile. 

The third class of hydraulic fluids discussed in this profile is the polyalphaolefins. Polyalphaolefins are 

synthetic hydrocarbons that are made by oligomerizing alphaolefins such as 1 -decene (see Chapters 3,4, 

and 5). Aliphatic hydrocarbons are the principal components of both mineral oils and polyalphaolefins, but 

the array of hydrocarbons with differing molecular weights is much narrower in polyalphaolefins than in 

mineral oils. Certain polyalphaolefins maintain good operational characteristics at low temperatures and have 

been proposed for use in hydraulic systems in U.S. military aircraft (Kinkead et al. 1992b). 

Hydraulic fluids are generally mixtures comprised of major and minor components whose presence may or 

may not be public information. Adverse health effects from exposure to mixtures can be caused by potent 

components, which may represent only minor portions of the whole mixture and whose presence may not be 

common knowledge. In the ensuing discussion of health effects from three classes of hydraulic fluids, 

attempts were made to identify tested hydraulic fluids by their commercial names and to focus-on what is 

known about the toxicological properties of the fluids themselves. Available information concerning the 

known chemical components of hydraulic fluids for which toxicological studies were located is discussed in 

Chapter 3. Information concerning the toxicological properties of major components expected to be found in 

hydraulic fluids discussed in this profile is discussed for tricresyl phosphate (TCP) and tributyl phosphate, 

because they comprise nearly 100% of some organophosphate ester hydraulic fluids (in the past and 
HYDRAULIC FLUIDS 11 

2. HEALTH EFFECTS
 

currently) and because they have important neurotoxic effects. Other individual components are discussed to a 

limited extent because of the uncertainty in extrapolating to effects caused by the complete mixture. The toxicity 

of these complex mixtures depends on interactions of all the components. Some components, when found 

together, may act additively or synergistically to enhance toxic effects. Other components may be antagonistic 

in combination, thus diminishing toxic effects. It cannot always be predicted how a mixture will behave based 

on the toxicity of its individual components. However, the toxic characteristics of the 

individual components may be an indicator of the potential toxicological responses of the mixture. 

A few case studies have reported neurological effects in humans following exposure to hydraulic fluids that 

probably contained organophosphorus compounds. Animal studies indicate that neurological effects are the 

most clearly identified health hazard associated with exposure to hydraulic fluids containing 

organophosphorus compounds. Because organophosphorus compounds are often added to fluids in which 

mineral oil or polyalphaolefins are the principal components, concern for the development of neurological 

effects is not restricted to fluids in which organophosphorus compounds are the principal components. 

Acute exposure to many organophosphorus compounds can cause at least one of two types of neurological 

effects: acute inhibition of acetylcholinesterase, an enzyme that controls transmission of nerve impulses at 

synapses, and organophosphorus-induced delayed neuropathy (OPIDN), a slowly developing axonal 

degeneration and demyelination in central and peripheral nerve tissues. Symptoms of acetylcholinesterase 

inhibition develop quickly (within hours of exposure) and include salivation, vomiting, diarrhea, muscle 

fasciculations, and general paralysis (see Table 2-10). OPIDN symptoms include weakness, ataxia, and 

paralysis, and are thought to develop through a mechanism distinct from acetylcholinesterase inhibition. 

Triaryl phosphates, particularly tri-ortho-cresyl phosphate (TOCP), are most closely associated with OPlDN, 

and studies of structure-activity relations of organophosphate esters that produce OPIDN have provided 

general relationships to predict neuropathy from chemical structure (Johanson 1977; Johnson 1990). It 

should be noted that chickens, cats, dogs, and ruminants are generally considered to be better models for 

human OPIDN than are rats, mice, and rabbits (see Section 2.3.5 for more details). 

The number of organophosphate esters and similar compounds used in hydraulic fluids is considerable. A 

core number (approximately 10) have been studied to some degree for toxicity. Though many hydraulic 

fluids are proprietary mixes of several organophosphate esters as originally formulated, environmental 

exposure to organophosphate esters is more complex because transformation to chemicals with greater or 

lesser toxicity than the original product may occur with time. Individual esters and whole hydraulic fluid 
HYDRAULIC FLUIDS 12 

2. HEALTH EFFECTS
 

product toxicity is presented in Sections 2.2 through 2.5, because toxicological research has involved both. 

Discussions on one closely related chemical, cyclotriphosphazene, are also provided because of structural and 

functional similarities. TOCP was a component of several triaryl organophosphate ester based hydraulic 

fluids, but was removed from formulations because of its toxicity. An attempt has been made to deemphasiz 

TOCP as a hydraulic fluid component, but it is included to illustrate toxicological properties. 

A glossary and list of acronyms, abbreviations, and symbols can be found at the end of this profile. 

2.2 DISCUSSION OF HEALTH EFFECTS BY ROUTE OF EXPOSURE 

To help public health professionals and others address the needs of persons living or working near hazardous
 

waste sites, the information in this section is organized first by route of exposure-inhalation, oral, and dermal;
 

and then by health effect-death, systemic, immunological, neurological, reproductive,
 

developmental, genotoxic, and carcinogenic effects. These data are discussed in terms of three exposure
 

periods-acute (14 days or less), intermediate (15-364 days), and chronic (365 days or more).
 

Levels of significant exposure for each route and duration are presented in tables and illustrated in figures.
 

The points in the figures showing no-observed-adverse-effect levels (NOAELs) or lowest-observedadverseeffect levels (LOAELs) reflect the actual doses (levels of exposure) used in the studies. LOAELS have
 

been classified into “less serious” or “serious” effects. “Serious” effects are those that evoke failure in a
 

biological system and can lead to morbidity or mortality (e.g., acute respiratory distress or death). “Less serious”
 

effects are those that are not expected to cause significant dysfunction or death, or those whose significance to
 

the organism is not entirely clear. ATSDR acknowledges that a considerable amount of judgment may be
 

required in establishing whether an end point should be classified as a NOAEL, “less serious” LOAEL, or
 

“serious” LOAEL, and that in some cases, there will be insufficient data to decide whether the effect is
 

indicative of significant dysfunction. However, the Agency has established guidelines and policies that are used
 

to classify these end points. ATSDR believes that there is sufficient merit in this approach to warrant an attempt
 

at distinguishing between “less serious” and “serious” effects. The distinction between “less serious” effects and
 

“serious” effects is considered to be important because it helps the users of the profiles to identify levels of
 

exposure at which major health effects start to appear. LOAELs or NOAELs should also help in determining
 

whether or not the effects vary with dose and/or duration, and place into perspective the possible significance of
 

these effects to human health.
 
HYDRAULIC FLUIDS 13 

2. HEALTH EFFECTS 

The significance of the exposure levels shown in the Levels of Significant Exposure (LSE) tables and figures 

may differ depending on the user’s perspective. Public health officials and others concerned with appropriate 

actions to take at hazardous waste sites may want information on levels of exposure associated with more subtle 

effects in humans or animals (LOAEL) or exposure levels below which no adverse effects (NOAELs) have been 

observed. Estimates of levels posing minimal risk to humans (Minimal Risk Levels or MRLs) may be of interest 

to health professionals and citizens alike. 

Although methods have been established to derive MRLs (Barnes and Dourson 1988; EPA 1990), 

uncertainties are associated with these techniques. Furthermore, ATSDR acknowledges additional 

uncertainties inherent in the application of the procedures to derive less than lifetime MRLs. As an example, 

acute inhalation MRLs may not be protective for health effects that are delayed in development or are 

acquired following repeated acute insults, such as hypersensitivity reactions, asthma, or chronic bronchitis. 

As these kinds of health effects data become available and methods to assess levels of significant human 

exposure improve, these MRLs will be revised. 

A User’s Guide has been provided at the end of this profile (see Appendix B). This guide should aid in the 

interpretation of the tables and figures for Levels of Significant Exposure and the MRLs. 

2.2.1 Inhalation Exposure 

The NOAEL and LOAEL values for each effect after inhalation exposure are shown in Tables 2-1,2-2, and 

2-3 and plotted in Figures 2-1,2-2, and 2-3 for mineral oil hydraulic fluids, organophosphate ester hydraulic 

fluids, and polyalphaolefin hydraulic fluids, respectively. 

2.2.1.1 Death 

Mineral Oil Hydraulic Fluids. No studies were located regarding death in humans after inhalation exposure 

to mineral oil hydraulic fluids. 

Several water-in-oil emulsion hydraulic fluids (Houghto-Safe 5047F, Sunsafe F, Pyroguard A-443, and 

Quintolubric 95830W) produced no deaths or clinical signs of toxicity in rats within 14 days of single 4-hour 

exposures to aerosol concentrations ranging from 110 to 210 mg/m3

 (Kinkead et al. 1987a, 1988). No deaths 

were reported in Fischer-344 rats during a 90-day continuous exposure (23 hours/day) to 1 .0 mg/m3 























HYDRAULIC FLUIDS 37 

2. HEALTH EFFECTS 

Houghto-Safe 5047F (Kinkead et al. 1991). A U.S. military fluid designated as MLH-5606 likewise 

produced no deaths in rats within 14 days of single 6-hour exposures to an aerosol concentration of 

1,148 mg/m3

 (Kinkead et al. 1985). Additional information on lethality of mineral oil hydraulic fluids in 

animals after inhalation exposure was not located. The available mineral oil hydraulic fluid studies 

(presented in Table 2-l and Figure 2-l) were not designed to examine lethality, and probably did not use high 

enough concentrations to cause death. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding death in humans after 

inhalation exposure to organophosphate ester hydraulic fluids. 

Single 4-hour exposures to aerosols of U.S. military fluids Durad MP280 and Fyrquel 220 produced no deaths in 

male rats at respective concentrations of 6,190 and 5,790 mg/m3

and female rats exposed to 6,350 and 6,310 

mg/m3

, respectively (Gaworski et al. 1986; Kinkead et al. 1992a). Daily 4-hour exposures over an 1 l-day period 

caused death to a single rabbit exposed to 2,000 mg/m3

 of Cellulube 220 (Carpenter et al. 1959). 

Intermediate-duration inhalation exposures to aerosols of a few organophosphate ester hydraulic fluids 

(Durad MP280 and trial phosphate ester”) produced lethal neurotoxic effects in chickens and rabbits 

(MacEwen and Vemot 1983; Siegel 1965). Rats and hamsters appear to be less susceptible to the neurotoxic 

action of organophosphate esters; tests of several organophosphate fluids produced no deaths in rats exposed to 

substantial aerosol concentrations. 

Aerosols of Cellulube 220 produced deaths associated with severe dyspnea and mild diarrhea in one of two 

rabbits exposed to 2,000 mg/m3

 for ≤4 hours/day, 5 days/week for 11 or 22 days (Carpenter et al. 1959). 

Continuous exposure for ~30-160 days to aerosols of a triaryl phosphate U.S. military hydraulic fluid (see 

Table 3-2), at concentrations ≤110 mg/m3

, produced no deaths in dogs or rats, but deaths associated with 

severe neurotoxic symptoms occurred in chickens exposed to concentrations ≥23 mg/m3

 and in rabbits 

exposed to 102 mg/m3

 (Siegel et al. 1965). Aerosols of Durad MP280 or Fyrquel 220 (continuous exposure 

for 90 days) produced no deaths in rats or hamsters exposed to 100 mg/m3

. Deaths associated with lethargy, 

cachexia, and head droop occurred in rabbits exposed to 101 mg/m3

 Durad MP280, but not in rabbits exposed to 

100 mg/m3

 Fyrquel 220 (MacEwen and Vemot 1983). Some of the Durad MP280-exposed 

rabbits were also infected with Pasteurella, which may have contributed to neurological symptoms. No 

deaths occurred in rats exposed to cyclotriphosphazene at 990 mg/m3

, 6 hours/day, 5 days/week for 21 days 
HYDRAULIC FLUIDS 38 

2. HEALTH EFFECTS
 

(Kinkead et al. 1989a, 1990) or in rats exposed to aerosols of Skydrol 500B-4 at concentrations ≤300 mg/m3

, 6 

hours/day, 5 days/week for 13 weeks (Healy et al. 1992; Monsanto 1987a, 1987b, 1989). The LOAEL values for 

death are presented in Table 2-2 and Figure 2-2. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding death in humans after inhalation 

exposure to polyalphaolefin hydraulic fluids. 

The LC50 values (single 4-hour exposures) for male and female rats, respectively, were determined for several 

U.S. military polyalphaolefin hydraulic fluids as follows: DTNSRDC N501, 2, 390 and 1,670 mg/m3 

(MacEwen and Vemot 1983); MIL-H-83282LT, 2,130 and 1,500 mg/m3 (Kinkead et al. 1992b); and 

B85-174, 1,620 and 1,390 mg/m3

 (Kinkead et al. 1987b). Kinkead et al. (1992b) speculated from 

observations of pulmonary edema in the dead rats that deaths were caused by acute respiratory irritation. 

Several other U.S. military fluids produced no deaths in rats within 14 days of single 4-hour exposures to the 

following aerosol concentrations: DTNSRDC N527, 5, 470 mg/m3

; DTNSRDC N448, 10, 720 mg/m3; 

DTNSRDC N518,5,350 mg/m3

; DTNSRDC N517, 5, 430 mg/m3; and DTNSRDC N525, 5, 470 mg/m3 

(MacEwen and Vemot 1983). These acute-duration LOAEL values for death are recorded in Table 2-3 and 

Figure 2-3. 

2.2.1.2 Systemic Effects 

The highest NOAEL values and all LOAEL values from each reliable study for systemic effects in each 

species and duration category are recorded in Tables 2-1,2-2, and 2-3 and plotted in Figures 2-1,2-2, and 

2-3 for mineral oil hydraulic fluids, organophosphate ester hydraulic fluids, and polyalphaolefin hydraulic 

fluids, respectively. Data for systemic effects (respiratory, cardiovascular, gastrointestinal, hematological, 

musculoskeletal, hepatic, renal, dermal, and ocular) from chicken studies were not presented in the LSE tables 

or figures because the appropriateness of nonmammalian models for human systemic effects is not known. 

However, chickens have been shown to be a sensitive species for neurological effects, and data from chickens 

are included in both the LSE tables and figures. 

Respiratory Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding respiratory effects in humans after 

inhalation exposure to mineral oil hydraulic fluids. 
HYDRAULIC FLUIDS 39 

2. HEALTH EFFECTS
 

Histopathological examination of the lungs from male and female Fischer 344 rats exposed to ≤1.0 mg/m3

 of the 

water-in-oil emulsion hydraulic fluid Houghto-Safe 5047F for 90 days, 23 hours/day, showed no 

treatment-related lesions (Kinkead et al. 1991). 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding respiratory effects in 

humans after inhalation exposure to organophosphate ester hydraulic fluids. 

Single 4-hour exposures to aerosols of U.S. military fluids Durad MP280 and Fyrquel220 produced no 

adverse respiratory effects in male Sprague-Dawley rats at respective concentrations of 6,190 and 

5,790 mg/m3

 and female Sprague-Dawley rats exposed to 6,350 and 6,310 mg/m3, respectively (Gaworski et al. 

1986; Kinkead et al. 1992a). Acute exposure to ≈6,300 mg/m3

 of Fyrquel 220 (Gaworski et al. 1986; 

Kinkead et al. 1992a) or Durad MP280 (Gaworski et al. 1986) did not result in respiratory tract damage in 

rats. 

Following intermediate-duration exposure to organophosphate ester hydraulic fluids, reversible rapid 

respirations were observed in rabbits exposed to 2,000 mg/m3

 of a triaryl phosphate hydraulic fluid 

(Cellulube 220) (Carpenter et al. 1959) and reddish nasal discharge (likely to be indicative of respiratory tract 

irritation) was observed in rats exposed to 100 mg/m3

 of Skydrol 500B-4 (Healy et al. 1992; Monsanto 

1987a, 1987b, 1989). The NOAEL for nasal discharge was 5.3 mg/m3

. Most studies that examined the 

respiratory tract did not find gross or histological alterations. Intermediate-duration exposure of rats, rabbits, 

dogs, hamsters, or monkeys to Fyrquel 220 (Gaworski et al. 1986; MacEwen and Vemot 1983), Durad 

MP280 (Gaworski et al. 1986; MacEwen and Vemot 1983), and triaryl phosphate (Siegel et al. 1965) also 

did not result in adverse respiratory tract effects. The NOAEL values following intermediate-duration 

exposure ranged from 100 to 260 mg/m3

 for rats, 50 to 260 mg/m3 for rabbits, 50 to 103 mg/m3 for dogs, 

100 to 260 mg/m3

 for hamsters, and 4.4 to 50 mg/m3 for monkeys. It should be noted that the 90-day 

NOAELs for Durad MP280 and Fyrquel 220 in rats, hamsters, and rabbits were based on gross pathology 

only (MacEwen and Vemot 1983). Intermediate-duration exposure to 990 mg/m3

 cyclotriphosphazene had 

no adverse respiratory effects on rats (Kinkead et al. 1989a, 1990). No chronic-duration inhalation studies 

examining the respiratory tract were located. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding respiratory effects in humans after 

inhalation exposure to polyalphaolefin hydraulic fluids. 
HYDRAULIC FLUIDS 40 

2. HEALTH EFFECTS
 

Certain polyalphaolefin hydraulic fluids appear to be respiratory tract irritants in animals. Bloody nasal 

discharge, rapid and shallow breathing, and lung congestion have been observed in rats exposed to 

880 mg/m3

 of a polyalphaolefin hydraulic fluid designated as B85-174 for 4 hours (Kinkead et al. 1987b). 

Exposure to a lethal concentration (1,120 mg/m3

) of a polyalphaolefin designated as MIL-H-83282LT 

resulted in perivascular and peribronchial edema in rats (Kinkead et al. 1992b). Labored breathing has also 

been observed in rats exposed for 4 hours to a lethal concentration (6,430 mg/m3

) of a polyalphaolefin 

hydraulic fluid designated as DTNSRDC N501 (MacEwen and Vet-not 1983). No longer-term studies 

examining respiratory effects were located. 

Cardiovascular Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding cardiovascular effects in humans after 

inhalation exposure to mineral oil hydraulic fluids. 

Histopathological examination of the heart from male and female Fischer 344 rats exposed to ≤1 .0 mg/m3

 of the 

water-in-oil emulsion hydraulic fluid Houghto-Safe 5047F for 90 days, 23 hours/day, showed no treatmentrelated lesions (Kinkead et al. 1991). 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding cardiovascular effects in 

humans after inhalation exposure to organophosphate ester hydraulic fluids. 

Following intermediate-duration exposure, no cardiovascular effects were observed in rats, rabbits, hamsters, 

dogs, or monkeys exposed to Durad MP280 (Gaworski et al. 1986; MacEwen and Vemot 1983), Fyrquel220 

(Gaworski et al. 1986; MacEwen and Vemot 1983), Skydrol 500B-4 (Healy et al. 1992; Monsanto 1987a, 

1987b, 1989), cyclotriphosphazene (Kinkead et al. 1989a, 1990), Cellulube 220 (Carpenter et al. 1959) or triaryl 

phosphate hydraulic fluids (Siegel et al. 1965). The ranges of NOAEL values were 100-260 mg/m3

 for rats, 251-

2,000 mg/m3

 for rabbits, 100-260 mg/m3 for hamsters, 50-103 mg/m3 for dogs, and 4.4-50 mg/m3 for monkeys. 

It should be noted that the 90-day NOAELs for Durad MP280 arid Fyrquel 220 in rats, hamsters, and rabbits 

were based on gross pathology only (MacEwen and Vemot 1983). Intermediate-duration exposure to 990 mg/m3 

cyclotriphosphazene had no adverse cardiovascular effects on rats (Kinkead et al. 1989a, 1990). No studies 

examining cardiovascular end points following acute-or chronic-duration inhalation exposure were located. 
HYDRAULIC FLUIDS 41 

2. HEALTH EFFECTS
 

Polyalphaolefm Hydraulic Fluids. No studies were located regarding cardiovascular effects in humans or 

animals after inhalation exposure to polyalphaolefin hydraulic fluids. 

Gastrointestinal Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding gastrointestinal effects in humans or 

animals after inhalation exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding gastrointestinal effects in 

humans after inhalation exposure to organophosphate ester hydraulic fluids. 

Mild diarrhea was reported for an acute-duration study on a single rabbit exposed to Cellulube 220 

(Carpenter et al. 1959), and transient diarrhea was reported in rabbits exposed to 26 mg/m3

 Fyrquel 220 for 

21 days for 6 hours a day (Gaworski et al. 1986; MacEwen and Vernot 1983). In most studies, diarrhea 

and/or gross or histological alterations in the gastrointestinal tract have not been observed in rats, rabbits, or 

hamsters exposed to organophosphate ester hydraulic fluids for an intermediate duration. NOAEL values of 

100-260 mg/m3

, l00-2,000 mg/m3, and 100-101 mg/m3 in rats, rabbits, and hamsters, respectively, exposed to 

Durad MP280 (Gaworski et al. 1986; MacEwen and Vemot 1983), Fyrquel220 (Gaworski et al. 1986; MacEwen 

and Vemot 1983), and Skydrol 500B-4 (Healy et al. 1992; Monsanto 1987a, 1987b, 1989). It should be noted 

that the 90-day NOAELs for Durad MP280 and Fyrquel 220 in rats, hamsters, and rabbits were based on gross 

pathology only (MacEwen and Vemot 1983). Cellulube 220 exposure in rabbits was associated with salivation, 

although this may have been a neurological response (Carpenter et al. 1959). Intermediate-duration exposure to 

990 mg/m3

 cyclotriphosphazene had no adverse gastrointestinal effects on rats (Kinkead et al. 1989a, 1990). No 

chronic-duration inhalation studies examining gastrointestinal end points were located. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding gastrointestinal effects in humans or 

animals after inhalation exposure to polyalphaolefin hydraulic fluids. 

Hematological Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding hematological effects in humans or 

animals after inhalation exposure to mineral oil hydraulic fluids. 
HYDRAULIC FLUIDS 42 

2. HEALTH EFFECTS
 

Organophosphate Ester Hydraulic Fluids. In a study of nonspecific monocyte esterase staining, humans 

who were exposed to aryl phosphates occupationally showed very slight esterase inhibition (Mandel et al. 

1959). 

Two studies reported hematological effects in animals exposed to organophosphate ester hydraulic fluids for 

an intermediate duration. Significant decreases in erythrocyte, hemoglobin, and hematocrit levels were 

observed in rats exposed to 300 mg/m3

 of Skydrol 500B-4 (Healy et al. 1992; Monsanto 1987a, 1987b, 

1989), and leukocytosis was observed in male rats exposed to 101 mg/m3

 Durad MP280 (MacEwen and 

Vemot 1983). The NOAEL values for these studies were 100 mg/m3

 for Skydrol 500B-4 and 10.3 mg/m3 for 

Durad MP280. 

A number of other animal studies have monitored hematological parameters, but have not found biologically 

significant alterations. The identified highest NOAEL values following intermediate exposure identified in 

other studies are 251 mg/m3

 for rats and rabbits exposed to Durad MP280 (Gaworski et al. 1986; MacEwen and 

Vemot 1983), 260 mg/m3

 for rats and rabbits exposed to Fyrquel 220 (Gaworski et al. 1986; MacEwen and 

Vemot 1983), and 990 mg/m3

 for rats exposed to cyclotriphosphazene (Kinkead et al. 1989a, 1990). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding hematological effects in humans or 

animals after inhalation exposure to polyalphaolefin hydraulic fluids. 

Musculoskeletal Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding musculoskeletal effects in humans or 

animals after inhalation exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding musculoskeletal effects in 

humans after inhalation exposure to organophosphate ester hydraulic fluids. 

In animals, the only musculoskeletal effect observed was kyphosis, a deformity of the spine characterized by 

extensive flexion. Kyphosis was observed in rats exposed to 100 mg/m3

 of Fyrquel 220 and 101 mg/m3 of 

Durad MP280 for an intermediate duration (MacEwen and Vemot 1983). The kyphosis was not observed at 

≈10 mg/m3

. It is not known whether the kyphosis was due to neurological or musculoskeletal damage. See 

Section 2.2.1.4 for more information on the neurological effects of organophosphate ester hydraulic fluids. 
HYDRAULIC FLUIDS 43 

2. HEALTH EFFECTS
 

Following intermediate-duration exposure, no histological damage was observed in the skeletal muscle of rats 

exposed to 990 mg/m3

 of cyclotriphosphazene (Kinkead et al. 1989a, 1990) or rabbits exposed to 

2,000 mg/m3

 of Cellulube 220 (Carpenter et al. 1959). Similar results were found in rats exposed to ≤300 mg/m3 

of Skydrol 500B-4 (Healy et al. 1992; Monsanto 1987a, 1987b, 1989). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding musculoskeletal effects in humans 

after inhalation exposure to polyalphaolefin hydraulic fluids.

 Kyphosis, a deformity of the spine characterized by extensive flexion, was observed in rats exposed to 880-

5030 mg/m3 of a polyalphaolefin hydraulic fluid designated as B85-174 for 4 hours (Kinkead et al. 1987b). The 

authors did not specify at which concentration the kyphosis occurred. It is not known whether the kyphosis was 

due to neurological or musculoskeletal damage. See Section 2.2.1.4 for more information on the neurological 

effects of polyalphaolefin hydraulic fluids. No longer-term inhalation exposure studies were located. 

Hepatic Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding hepatic effects in humans after inhalation 

exposure to mineral oil hydraulic fluids. 

Histopathological examination of the liver from male and female Fischer 344 rats exposed to ≤1.0 mg/m3

 of the 

water-in-oil emulsion hydraulic fluid Houghto-Safe 5047F for 90 days, 23 hours/day, showed no 

treatment-related lesions (Kinkead et al. 1991). 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding hepatic effects in humans 

after inhalation exposure to organophosphate ester hydraulic fluids. 

Following acute exposure, a NOAEL of 6,350 mg/m3

 has been identified in rats exposed to Durad MP280 

(Gaworski et al. 1986), and 6,310 mg/m3

 in rats exposed to Fyrquel 220 (Gaworski et al. 1986; Kinkead et 

al. 1992a). Significant increases in absolute and/or relative liver weights have been observed in rats exposed to 

100 or 260 mg/m3

 of Fyrquel220 (Gaworski et al. 1986; MacEwen and Vernot 1983) and 101 or 

25 1 mg/m3

 of Durad MP280 (Gaworski et al. 1986; MacEwen and Vernot 1983) for intermediate durations. 

However, histological alterations have not been observed in rats, rabbits, hamsters, dogs, monkeys, or 
HYDRAULIC FLUIDS 44 

2. HEALTH EFFECTS 

chickens exposed to Durad MP280 (Gaworski et al. 1986; MacEwen and Vemot 1983), Fyrquel 220 

(Gaworski et al. 1986; Kinkead et al. 1992a; MacEwen and Vemot 1983), Skydrol 500B-4 (Healy et al. 

1992; Monsanto 1987a, 1987b, 1989) Cellulube 220 (Carpenter et al. 1959) and triaryl phosphate (Siegel et 

al. 1965). Thus, the changes in liver weight were not considered adverse. Mild hepatocellular vacuolation 

and significant increases in absolute and relative liver weights were observed in rats exposed to 300 mg/m3 

Skydrol 500B-4 for 13 weeks; no hepatic effects were observed in the 100 mg/m3 group (Healy et al. 1992; 

Monsanto 1987a, 1987b, 1989). The authors noted that since there were no other histological alterations in 

the liver or changes in hepatic serum enzymes at any concentration, these effects were not considered adverse. 

No hepatic effects were observed in other intermediate-duration inhalation studies. The NOAEL values for liver 

effects following intermediate-duration exposure to organophosphate ester hydraulic fluids are 100-260 mg/m3 

for rats, 251-2,000 mg/m3 for rabbits, 100-260 mg/m3 for hamsters, 50-103 mg/m3 for dogs, and 4.4-50 mg/m3 

for monkeys. It should be noted that the 90-day NOAELs for Durad MP280 and Fyrquel220 in rats, hamsters, 

and rabbits were based on gross pathology only (MacEwen and Vemot 1983). Intermediate-duration exposure 

to 990 mg/m3

 cyclotriphosphazene had no adverse hepatic effects on rats (Kinkead et al. 1989a, 1990). No 

chronic exposure studies examining hepatic end points were located. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding hepatic effects in humans or animals 

after inhalation exposure to polyalphaolefin hydraulic fluids. 

Renal Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding renal effects in humans after inhalation 

exposure to mineral oil hydraulic fluids. 

Histopathological examination of the kidneys from male and female Fischer 344 rats exposed to ≤1.0 mg/m3

 of 

the water-in-oil emulsion hydraulic fluid Houghto-Safe 5047F for 90 days, 23 hours/day, showed no treatmentrelated lesions (Kinkead et al. 1991). 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding renal effects in humans after 

inhalation exposure to organophosphate ester hydraulic fluids. 
HYDRAULIC FLUIDS 45 

2. HEALTH EFFECTS
 

No gross or histological alterations were observed in the kidneys of rats exposed to 6,350 mg/m3

 of Durad 

MP280 (Gaworski et al. 1986) or to 6,310 mg/m3

 of Fyrquel 220 (Gaworski et al. 1986; Kinkead et al. 

1992a) for single 4-hour periods. Significant increases in absolute and relative kidney weights were observed in 

rats exposed to 100 mg/m3

 of Fyrquel 220 for an intermediate duration (MacEwen and Vemot 1983). However, 

no gross or histological lesions were observed at this or a higher concentration (260 mg/m3

) for a shorter 

duration (Gaworski et al. 1986; MacEwen and Vemot 1983). Thus, this change in kidney weight was not 

considered adverse. A number of intermediate-duration studies have identified NOAEL values in rats, rabbits, 

hamsters, dogs, monkeys, and chickens exposed to Durad MP280 (Gaworski et al. 1986; MacEwen and Vemot 

1983), Fyrquel 220 (Gaworski et al. 1986; MacEwen and Vemot 1983), Skydrol 500B-4 (Healy et al. 1992; 

Monsanto 1987a, 1987b, 1989), Cellulube 220 (Carpenter et al. 1959), and triaryl phosphate (Siegel et al. 1965). 

The NOAEL values for renal effects following intermediate-duration exposure to organophosphate ester 

hydraulic fluids are 100-260 mg/m3

 for rats, 251-2,000 mg/m3 for rabbits, 100-260 mg/m3 for hamsters, 50-103 

mg/m3

 for dogs, and 4.4-50 mg/m3 for monkeys. It should be noted that the 90-day NOAELs for Durad MP280 

and Fyrquel 220 in rats, hamsters, and rabbits were based on gross pathology only (MacEwen and Vemot 1983). 

An accumulation of hyaline droplets was observed in male and female rats exposed to ≥240 mg/m3 of 

cyclotriphosphazene for an intermediate duration (Kinkead et al. 1989a, 1990). The severity of the droplet 

accumulation was graded as minimal to mild. No changes in serum creatinine or urea nitrogen levels were 

observed in this study. No chronic exposure studies examining renal end points were located. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding renal effects in humans or animals 

after inhalation exposure to polyalphaolefin hydraulic fluids. 

Endocrine Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding endocrine effects in humans or animals 

after inhalation exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding endocrine effects in humans after 

inhalation exposure to organophosphate ester hydraulic fluids. 

No endocrine effects were seen in acute inhalation exposure to a triaryl phosphate mixture (Cellulube 220) 

for rabbits at 2,000 mg/m3

 (Carpenter et al. 1959). In studies on rats, hamsters and rabbits no endocrine 
HYDRAULIC FLUIDS 46 

2. HEALTH EFFECTS
 

effects are reported for intermediate-duration exposure to 300 mg/m3

 Skydrol 500B-4 (Healy et al. 1992; 

Monsanto 1987a, 1987b, 1989), 100 mg/m3

 Fyrquel 220 or 101 mg/m3 Durad MP280 (MacEwen and 

Vemot 1983), or 2,000 mg/m3

 of Cellulube 220 (Carpenter et al. 1959). It should be noted that the 90-day 

NOAELs for Durad MP280 and Fyrquel 220 in rats, hamsters, and rabbits were based on gross pathology 

only (MacEwen and Vemot 1983). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding endocrine effects in humans or 

animals after inhalation exposure to polyalphaolefin hydraulic fluids. 

Dermal Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding dermal effects in humans or animals after 

inhalation exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding dermal effects in humans 

after inhalation exposure to organophosphate ester hydraulic fluids. 

No gross or histological alterations were observed in the skin of rats, rabbits, or hamsters exposed to 

100 mg/m3

 of Fyrquel 220 or 101 mg/m3 of Durad MP280 (MacEwen and Vemot 1983), or G ≤300 mg/m3 

Skydrol 500B-4 (Healy et al. 1992; Monsanto 1987a, 1987b, 1989), or ≤990 mg/m3 cyclotriphosphazene 

(Kinkead et al. 1989a, 1990) for an intermediate duration, or in rabbits exposed to 2,000 mg/m3

 of Cellulube 

220 for acute and intermediate durations (Carpenter et al. 1959). It should be noted that the 90-day NOAELs for 

Durad MP280 and Fyrquel 220 in rats, hamsters, and rabbits were based on gross pathology only (MacEwen and 

Vemot 1983). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding dermal effects in humans after 

inhalation exposure to polyalphaolefin hydraulic fluids. 

Ocular Effects. 

Mineral Oil Hydraulic FLuids. No studies were located regarding ocular effects in humans or animals after 

inhalation exposure to mineral oil hydraulic fluids. 
HYDRAULIC FLUIDS 47 

2. HEALTH EFFECTS
 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding ocular effects in humans 

after inhalation exposure to organophosphate ester hydraulic fluids. 

No histological evidence of damage to the eye was observed in rats exposed to 990 mg/m3

 of 

cyclotriphosphazene for an intermediate duration (Kinkead et al. 1989a, 1990). 

Polyalphaolefm Hydraulic Fluids. No studies were located regarding ocular effects in humans after 

inhalation exposure to polyalphaolefin hydraulic fluids. Ocular effects in animals resulting from direct 

contact with aerosols of polyalphaolefin hydraulic fluids are discussed in Section 2.3, Dermal Effects. 

Body Weight Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding body weight effects in humans after 

inhalation exposure to mineral oil hydraulic fluids. In rats, no alterations in body weight gain were observed 

following 4-hour exposures to 180 mg/m3

 of Sunsafe F (Kinkead et al. 1987a, 1988), 180 mg/m3 of Quintolubric 

95830W (Kinkead et al. 1987a, 1988), 210 mg/m3

 of Houghto-Safe 5047F (Kinkead et al. 1987a, 1988), or 110 

mg/m3

 of Pyroguard A-443 (Kinkead et al. 1987a, 1988), or following a 6-hour exposure to 1,130 mg/m3 of a 

mineral oil hydraulic fluid meeting military specifications of MJL-5606 (Kinkead et al. 1985). Body weight was 

unaffected in male and female Fischer 344 rats exposed to ≤1.0 mg/m3

 of the water-in-oil emulsion hydraulic 

fluid Houghto- Safe 5047F for 90 days, 23 hours/day (Kinkead et al. 1991). 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding body weight effects in 

humans after inhalation exposure to organophosphate ester hydraulic fluids. 

No changes in body weight gain were observed in rats exposed for 4 hours to 6,350 mg/m3

 Durad MP280 

(Gaworski et al. 1986; Kinkead et al. 1992d), or for 4 hours to 6,3 10 mg/m3

 Fyrquel 220 (Gaworski et al. 

1986; Kinkead et al. 1992a). In intermediate-duration studies, an 11% loss of body weight occurred in 

squirrel monkeys exposed to 25 mg/m3

 of a triaryl phosphate mixture for 6 weeks (Siegel et al. 1965). In 

other studies, no adverse changes in body weight or weight gain were reported in monkeys, rats, rabbits, 

hamsters, and dogs exposed for intermediate durations to Fyrquel 220 (Gaworski et al. 1986; MacEwen and 

Vemot 1983), Durad MP280 (Gaworski et al. 1986; MacEwen and Vemot 1983), Skydrol 500B-4 (Healy et 
HYDRAULIC FLUIDS 48 

2. HEALTH EFFECTS
 

al. 1992; Monsanto 1987a, 1987b, 1989), or triaryl phosphate (Siegel et al. 1965). The identified NOAEL 

values ranged from 100 to 260 mg/m3

 for rats, 25 1 to 260 for rabbits, 100 to 260 mg/m3 for hamsters, and 

50 to 103 mg/m3

 for dogs, and 4.4 mg/m3 for monkeys. Intermediate-duration exposure to 990 mg/m3 

cyclotriphosphazene had no effect on body weight in rats (Kinkead et al. 1989a, 1990). No chronic-duration 

exposure studies examining body weight end points were located. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding body weight effects in humans after 

inhalation exposure to polyalphaolefin hydraulic fluids. 

No changes in body weight gain were observed in rats exposed for 4 hours to several polyalphaolefin 

hydraulic fluids at the following concentrations: 10,720 mg/m3

 - DTNSRDC N448; 5,430 mg/m3 -

DTNSRDC N517; 5,350 mg/m3

 - DTNSRDC N518; 5,330 mg/m3 - DTNSRDC N525; 5,470 mg/m3 -

DTNSRDC N527 (all fluids with a DTNSRDC number were tested by MacEwen and Vernot [1983]); 

1,130 mg/m3

 – MIL-H-83282 (Kinkead et al. 1985). In these experiments, rats were observed for 14 days 

after exposure. 

2.2.1.3 Immunological and Lymphoreticular Effects 

Mineral Oil Hydraulic Fluids. No studies were located regarding immunological effects in humans or 

animals after inhalation exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding immunological effects 

in humans after inhalation exposure to organophosphate ester hydraulic fluids. 

Information regarding immunological effects in animals is restricted to histopathological examination of 

organs with immune functions (thymus, spleen, lymph nodes) after intermediate-duration inhalation 

exposures of up to 90 days. No treatment-related lesions in these tissues was reported in rats exposed to 

≤900 mg/m3

 cyclotriphosphazene (Kinkead et al. 1989b, 1990). No lesions were seen in the spleen of rats 

exposed to 260 mg/m3

 Fyrquel 220 or 25 1 mg/m3 Durad MP280 (Gaworski et al. 1986; MacEwen and 

Vernot 1983), or 300 mg/m3

 Skydrol 500B-4 (Healy et al. 1992; Monsanto 1987a, 1987a, 1989). Similar 

results were reported for the spleen in both hamsters and rabbits exposed to ≤260 mg/m3

 Fyrquel220 or 

251 mg/m3

 Durad MP280 for 21 days (Gaworski et al. 1986; MacEwen and Vemot 1983). It should be 

noted that the 90-day NOAELs for Durad MP280 and Fyrquel 220 in rats, hamsters, and rabbits were based 
HYDRAULIC FLUIDS 49 

2. HEALTH EFFECTS
 

on gross pathology only (MacEwen and Vernot 1983). The NOAEL values for immunological effects are 

recorded in Table 2-2 and plotted in Figure 2-2. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding immunological effects in 

humans or animals after inhalation exposure to polyalphaolefin hydraulic fluids. 

2.2.1.4 Neurological Effects 

The highest NOAEL values and all LOAEL values from each reliable study for neurological effects in each 

species and duration category are recorded in Tables 2-1,2-2, and 2-3 and plotted in Figures 2-1, 2-2, and 

2-3 for mineral oil hydraulic fluids, organophosphate ester hydraulic fluids, and polyalphaolefin hydraulic 

fluids, respectively. 

Mineral Oil Hydraulic Fluids. No studies were located regarding neurological effects in humans after 

inhalation exposure to mineral oil hydraulic fluids. There are reports of neurological effects in humans 

occupationally exposed to mineral oil hydraulic fluids; however dermal contact was expected to have been the 

primary route of exposure (see Section 2.2.3.4). 

Information regarding neurological effects in animals after inhalation exposure to mineral oil hydraulic fluids 

is limited to two rat studies in which no symptoms of acute neurotoxicity or delayed neuropathy were seen in 

rats within 14 days of aerosol exposure. (These studies did not specifically look for neurological effects.) 

One study exposed Fischer 344 rats for 4 hours to water-in-oil emulsion hydraulic fluids at concentrations 

ranging from 110 to 210 mg/m3

 (Pyroguard A-443, Houghto-Safe 5047F, Quintolubric 9583OW, and 

Sunsafe F) (Kinkead et al. 1987a, 1988). The second study exposed rats to 1,148 mg/m3

 of MIL-H-5606 for 

6 hours (Kinkead et al. 1985). 

Organophosphate Ester Hydraulic Fluids. The principal adverse effect of exposure to 

organophosphate esters is neurotoxicity. Organophosphate esters have been synthesized that-are 

preferentially toxic to insects compared to mammals; these are widely used as insecticides (e.g., chlorpyrifos, 

diazinon). Acute toxicity to organophosphate esters is mediated by the inhibition of neural acetylcholinesterase. 

Neural acetylcholinesterase is present at cholinergic synapses throughout the central and peripheral nervous 

systems, and is responsible for hydrolyzing acetylcholine released from the pre-synaptic terminal. If this enzyme 

is inhibited, acetylcholine accumulates in the synapse, resulting in increased firing of the post­
HYDRAULIC FLUIDS 50 

2. HEALTH EFFECTS
 

synaptic neuron or increased neuroeffector activity. The consequences of increased cholinergic activity in the 

parasympathetic autonomic nervous system (muscarinic receptors) can include increased salivation, 

lacrimation, perspiration, miosis, nausea, vomiting, diarrhea, excessive bronchial secretions, bradycardia, 

frequent micturition, and incontinence. The effects of increased neuroeffector activity on skeletal muscles 

(nicotinic receptors) can include muscle fasciculations, cramps, muscle weakness, and depolarization-type 

paralysis. Effects on cholinergic synapses in the central nervous system (predominantly muscarinic) can 

result in drowsiness, fatigue, mental confusion, headache, convulsions, and coma (see Table 2-10). These 

classical symptoms of organophosphate ester neurotoxicity increase in severity and rapidity of onset in a 

dose-dependent manner (Ecobichon 1991). 

Acetylcholinesterase is also present in erythrocytes where it is known as erythrocyte acetylcholinesterase. 

Both forms of acetylcholinesterase are produced by the same gene (Taylor et al. 1993). In in vitro assays, 

erythrocyte and neural acetylcholinesterase are inhibited to roughly the same extent by exposure to many 

organophosphate esters. Measurement of erythrocyte acetylcholinesterase is used as a surrogate of the 

inhibition of neural acetylcholinesterase. A cholinesterase capable of hydrolyzing acetylcholine is also 

produced by the liver and circulates in the blood. This enzyme, called plasma cholinesterase or 

butyrylcholinesterase, can also be inhibited by organophosphate esters and is often used as a marker for 

exposure. The endogenous substrate of this enzyme is unknown. This enzyme is often inhibited by 

organophosphate esters at lower levels of exposure than required to inhibit neural or erythrocyte 

acetylcholinesterase. Erythrocyte acetylcholinesterase activity is located in the erythrocyte membrane and can 

be differentiated from plasma cholinesterase by sedimenting the erythrocytes from whole blood. Measurement 

of “whole blood cholinesterase” reflects both plasma and erythrocyte activity. 

Exposure to organophosphate esters can also cause a syndrome referred to as organophosphate-induced 

delayed neuropathy (OPIDN). This is a syndrome observed in humans and some animal models after 

exposure to certain organophosphate esters, for example tri-ortho-cresyl phosphate (Johnson 1981). The 

initial clinical signs are disturbances of gait, usually seen at least a week after exposure has begun. Severe 

cases can result in ataxia and paralysis. A characteristic “dying-back” type degeneration of motor fibers is 

seen upon histopathological examination. The biochemical mechanism of OPIDN is unknown at the present 

time. This syndrome does not appear to be closely correlated with neural acetylcholinesterase inhibition, but 

rather an enzyme activity referred to as “neurotoxic esterase” (NTE). The endogenous substrate of this 

enzyme activity is unknown. This syndrome can be reproduced in chickens, but not in rats or mice (AbouDonia and Lapadula 1990). 
HYDRAULIC FLUIDS 51 

2. HEALTH EFFECTS
 

One study was located regarding neurological effects in humans after inhalation exposure to organophosphate 

ester hydraulic fluids. Workers in an aryl phosphate manufacturing plant were not found to have neurological 

deficits even with decades of potential exposure (Reade 1982). 

Information regarding neurological effects in animals after acute inhalation exposure to organophosphate 

ester hydraulic fluids is limited to reports of a decrease in whole blood cholinesterase in mice exposed to 

757 mg/m3

 of triphenyl phosphate (Sutton et al. 1960) and of head droop, generalized weakness, and 

decreased whole blood cholinesterase activity in one of two rabbits exposed to aerosols of 2,000 mg/m3 

Cellulube 220,4 hours/day, 5 days/week for 11 days (Carpenter et al. 1959). Transient, mild lethargy after 

4-hour exposures to aerosols of Durad MP280 and Fyrquel 220 has been observed (Gaworski et al. 1986; 

Kinkead et al. 1992a). 

Several organophosphate ester hydraulic fluids have produced neurological effects in several animal species 

after intermediate inhalation exposure (see Table 2-2). 

Aerosols of Skydrol 500B-4 produced transient excessive salivation in rats exposed to 300 mg/m3

, 6 hours 

per day, 5 days per week for 6 or 13 weeks; this effect was not observed with exposure to 100 mg/m3

 by the 

same protocol (Healy et al. 1992; Monsanto 1987a, 1987b, 1989). Plasma cholinesterase activity (a marker 

for organophosphate ester exposure) was decreased 60% in this group; erythrocyte acetylcholinesterase was not 

measured in this study. Aerosols of Cellulube 220 produced decreased whole blood cholinesterase 

activity (13-57%) in rabbits exposed to 2,000 mg/m3 for 4 hours/day, 5 days/week for 22 days; exposure for 

2 hours/day produced no clinical signs of neurotoxicity in two rabbits (Carpenter et al. 1959). No overt signs 

of neurotoxicity or histological alterations of brain or sciatic nerve tissues were observed in rats exposed to 

cyclotriphosphazene at 990 mg/m3

, 6 hours/day, 5 days/week for 21 days (Kinkead et al. 1989a, 1990). 

Continuous exposure for ≈30-160 days to aerosols of a triaryl phosphate U.S. military hydraulic fluid, triaryl 

phosphate (see Table 3-l), produced paralysis in rabbits and chickens after exposure to 102 mg/m3

 and 

23 mg/m3

, respectively, but not after exposure to respective concentrations of 34 mg/m3 or 4.4 mg/m3 (Siegel 

et al. 1965). Continuous exposure to triaryl phosphate at 110, 103, or 4.4 mg/m3

, respectively, produced no 

signs of neurotoxicity in rats after 36 days, dogs after 99 days, or monkeys after 108 days (Siegel et al. 

1965). Intermittent exposure (8 hours/day, 5 days/week for 30 exposures) to 50 mg/m3

 triaryl phosphate 

produced no neurotoxic signs in squirrel monkeys (Siegel et al. 1965). Aerosols of Durad MP280 

(continuous exposure for 90 days) produced kyphosis (a deformity of the spine characterized by extensive 
HYDRAULIC FLUIDS 52 

2. HEALTH EFFECTS
 

flexion) and a decrease in the tail tip curl reflex in rats and anorexia, lethargy, cachexia, and head droop in 

rabbits after exposure to 101 mg/m3

; exposure to 10.3 mg/m3 produced no signs of neurotoxicity in these 

species (MacEwen and Vernot 1983). Hamsters similarly exposed to 101 mg/m3

 Durad MP280 showed no 

evidence of neurotoxicity in this study. Aerosols of Fyrquel 220 (continuous exposure for 90 days) likewise 

produced kyphosis in rats at 100 mg/m3

, but no clinical signs of neurotoxicity in rabbits or hamsters at 

100 mg/m3

 (MacEwen and Vernot 1983). Because of the uncertainty that the kyphosis observed in rats is a 

neurological or muscular effect, this effect has been discussed in both sections. 

The studies by Siegel et al. (1965) and MacEwen and Vemot (1983) also included intermittent exposure 

experiments (8 or 6 hours/day, respectively, for 5 days/week) for shorter durations (30 exposures or 21 days, 

respectively). Neither Fyrquel 220 (260 mg/m3

) nor Durad MP280 (251 mg/m3) produced signs of 

neurotoxicity in rats, rabbits, or hamsters with the intermittent exposure protocol (MacEwen and Vemot 

1983). No evidence of neurotoxicity was observed in rats exposed to ≤300 mg/m3

 Skydrol500B-4 

intermittently for 6 or 13 weeks (Healy et al. 1992; Monsanto 1987a, 1987b, 1989). The intermittent 

protocol used by Siegel et al. (1965) produced no signs of neurotoxicity in rabbits or dogs at 50 mg/m3

 triaryl 

phosphate. It produced delayed peripheral neuropathy in chickens at 50 mg/m3

 but not at 25 mg/m3. 

No information was located regarding neurological effects in animals after chronic inhalation exposure to 

organophosphate ester hydraulic fluids. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding neurological effects in humans 

after inhalation exposure to polyalphaolefin hydraulic fluids. 

In a series of acute lethality studies, lethargy and inactivity were noted in rats exposed for 4 hours to lethal 

concentrations of DTNSRDC N501 (6,430 mg/m3

) (MacEwen and Vemot 1983). Kyphosis was observed in 

rats exposed to 880-5,030 mg/m3

 of a polyalphaolefin hydraulic fluid designated as B85-174 (Kinkead et al. 

1987b). Because of the uncertainty of whether the kyphosis is a neurological or muscular effect, this effect is 

discussed in both-the Musculoskeletal Effects and Neurological Effects sections. No other information was 

located on neurological effects in animals after inhalation exposure to polyalphaolefin hydraulic fluids. 
HYDRAULIC FLUIDS 53 

2. HEALTH EFFECTS 

2.2.1.5 Reproductive Effects 

Mineral Oil Hydraulic Fluids. No studies were located regarding reproductive effects in humans or 

animals after inhalation exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding reproductive effects in 

humans after inhalation exposure to organophosphate ester hydraulic fluids. 

Testicular atrophy was observed upon gross necropsy after male rats were continuously exposed for 90 days to 

an aerosol concentration of 101 mg/m3

 Durad MP280, but not in rats exposed to 10.3 mg/m3 (MacEwen and 

Vemot 1983). Testicular atrophy was not observed in male rats continuously exposed for 90 days to an aerosol 

concentration of 100 mg/m3

 Fyrquel 220 (MacEwen and Vemot 1983). 

Male and female rats showed no treatment-related gross or histological reproductive tract alterations when 

exposed by inhalation 6 hours/day, 5 days/week for 3 weeks to a 990 mg/m3

 aerosol of cyclotriphosphazene 

(Kinkead et al. 1989a, 1990), or aerosol concentrations of Skydrol 500B-4 ≥300 mg/m3

, 6 hours/day, 

5 days/week for 13 weeks (Healy et al. 1992; Monsanto 1987a, 1987b, 1989). 

Likewise, no treatment-related gross reproductive tract alterations after intermediate-duration exposure were 

observed in male or female rabbits or in male hamsters continuously exposed to aerosols of Fyrquel220 at 

concentrations ≤100 mg/m3

 (MacEwen and Vemot 1983). Two male rabbits exposed for l-4 hours/day, 

4-5 days/week, for 11-26 days to 2,000 mg/m3

 aerosol of Cellulube 220 (Carpenter et al. 1959) showed no 

histological evidence for effects on reproductive tissues. No acute or chronic inhalation studies examining 

reproductive effects in animals were located. 

The highest NOAEL values and all LOAEL values from each reliable study for reproductive effects in each 

species and duration category are recorded in Table 2-2 and plotted in Figure 2-2. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding reproductive effects in humans 

or animals after inhalation exposure to polyalphaolefin hydraulic fluids. 
HYDRAULIC FLUIDS 54 

2. HEALTH EFFECTS 

2.2.1.6 Developmental Effects 

No studies were located regarding developmental effects in humans or animals after inhalation exposure to 

mineral oil hydraulic fluids, organophosphate ester hydraulic fluids, or polyalphaolefin hydraulic fluids. 

2.2.1.7 Genotoxic Effects 

Mineral Oil Hydraulic Fluids. No studies were located regarding genotoxic effects in humans or 

animals after inhalation exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding genotoxic effects in 

humans or animals after inhalation exposure to organophosphate ester hydraulic fluids. Genotoxicity studies 

for organophosphate ester hydraulic fluids are discussed in Section 2.5. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding genotoxic effects in humans or 

animals after inhalation exposure to polyalphaolefin hydraulic fluids. 

2.2.1.8 Cancer 

Mineral Oil Hydraulic Fluids. Studies regarding cancer in humans or animals after inhalation exposure to 

mineral oil hydraulic fluids were limited to a single case-control study that examined associations between 

subjectively reported occupational exposure to petroleum-derived liquids and cancer at particular sites among 

3,726 male cancer patients (Siemiatycki et al. 1987a). The study found no convincing associations between 

occupational exposure to hydraulic fluids and cancer at any site. This study is discussed in more detail in 

Section 2.2.3.8, because, while inhalation exposure was probable for the subject occupations, the authors 

reported that the exposure route was more often dermal contact. 

No studies were located regarding cancer in animals after inhalation exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding cancer in humans or 

animals after inhalation exposure to organophosphate ester hydraulic fluids. 
HYDRAULIC FLUIDS 55 

2. HEALTH EFFECTS
 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding cancer in humans or animals 

after inhalation exposure to polyalphaolefin hydraulic fluids. 

2.2.2 Oral Exposure 

The NOAEL and LOAEL values for each effect after oral exposure are shown in Tables 2-4,2-5, and 2-6 

and plotted in Figures 2-4,2-5, and 2-6 for mineral oil hydraulic fluids, organophosphate ester hydraulic 

fluids, and polyalphaolefin hydraulic fluids, respectively. 

2.2.2.1 Death 

Mineral Oil Hydraulic Fluids. A 14-month-old boy ingested ≈5-10 cc of automobile automatic 

transmission fluid thought to have been composed primarily (75-80%) of mineral oil (Perrot and Palmer 

1992). The child developed pneumonia, pneumothorax (presence of gas in the pleural cavity), hemorrhaging 

in the intestines, and a distended abdomen and eventually died 4 weeks after ingestion. Postmortem 

examination revealed scattered subserosal hemorrhage in the small and large intestine and the omentum, as well 

as focal edema, hemorrhage, and lipoid/oil droplets in the lung, and proliferation of alveolar 

macrophages. The presence of lipoid/oil droplets in the lung suggest that the transmission fluid was 

aspirated. Additional information was not located on lethality of mineral oil hydraulic fluids in humans after 

oral exposure. 

Several water-in-oil emulsion hydraulic fluids (Houghto-Safe 5047F, Sunsafe F, Pyroguard A-443, and 

Quintolubric 95830W) produced no deaths or clinical signs of toxicity at single gavage dosage levels of 

5,000 mg/kg in rats observed for 14 days (Kinkead et al. 1987a, 1988). Single gavage doses of a U.S. 

military fluid designated as MIL-H-5606 at 4,500 mg/kg (5 mL/kg) also produced no deaths in rats observed 

for 14 days (Kinkead et al. 1985). Additional information on lethality of mineral oil hydraulic fluids in 

animals after oral exposure was not located. No studies showing LOAEL values for lethality are shown in 

Table 2-4 or Figure 2-4. 







































HYDRAULIC FLUIDS 95 

2. HEALTH EFFECTS
 

Organophosphate Ester Hydraulic Fluids. Reports of organophosphate poisonings in the United 

States, India, and South Africa date back to the 1930s when tri-ortho-cresyl phosphate was either 

inadvertently mixed with cooking oils or was an adulterant of an alcohol-containing extract, Jamaica Ginger 

(Goldstein et al. 1988). Few deaths are reported, but polyneuritis and paralysis are common to these 

outbreaks. 

Acute oral exposure to several organophosphate ester hydraulic fluids produced deaths in rabbits, chickens, 

and cows. The deaths were associated with severe cholinergic symptoms or symptoms of organophosphorus 

induced delayed neuropathy (OPIDN). (See Section 2.2.2.4 for further details on the neurological effects.) 

Single oral gavage doses of several organophosphate ester hydraulic fluids produced deaths in rats. LD50 values 

are reported for rats at >8,400 mg/kg for triaryl phosphates, 2,400 mg/kg for dibutyl phenyl 

phosphate, and 1,400 mg/kg for tributyl phosphate (Johannsen et al. 1977). No deaths were reported for rats at 

the highest administered dosage levels which were: Durads 300, 550B, 116, and 220B, 5,000 mg/kg (FMC 

1990a); Durad MP280,5,775 mg/kg (Gaworski et al. 1986); and Cellulube 220 (two rats tested), 

20,000 mg/kg (Dollahite and Pierce 1969). Single gavage doses of 34,500 mg/kg Pydraul 50E produced 

deaths in 3 of 10 rats from unspecified causes, but a dosage level of 28,750 mg/kg produced no deaths (FMC 

1978a). No deaths were reported in rats orally exposed to a cyclotriphosphazene-based fluid at ≤5,000 mg/kg 

(Kinkead et al. 1992c; MacEwen and Vemot 1985). 

Cellulube 220 produced deaths (including animals killed due to morbidity) associated with severe cholinergic 

symptoms and paralysis that developed within 5 days in four of five rabbits after administration of single 

doses of 7,500 mg/kg, but no deaths were produced after two rabbits received doses of 6,000 mg/kg 

(Dollahite and Pierce 1969). Lethal cholinergic toxicity after 6 days was observed in one of two rabbits 

exposed daily to 120 mg/kg/day of Cellulube 220 for 2-14 days (Carpenter et al. 1959). 

The actual composition of the Cellulube 220 was not reported in either the Dollahite or Carpenter studies, so 

the large difference in doses causing death can not be explained. Deaths were also reported in 5 of 5 pregnant 

Wistar rats after 5-6 daily doses of 800 mg/kg tributyl phosphate beginning on gestation day 7 (Noda et al. 

1994). 

The acute oral LD50 values for Skydrol 500B-4, Skydrol LD-4, tributyl phosphate, and dibutyl phenyl 

phosphate in chickens were 2, 559, 2, 594, 1,500 or 1,800, and <2,000 mg/kg, respectively; deaths occurred 
HYDRAULIC FLUIDS 96 

2. HEALTH EFFECTS
 

within 1-3 days with severe cholinergic symptoms (Carrington et al. 1989; Johannsen et al. 1977; Monsanto 

1987c, 1987d). Lethal single gavage doses of 300 and 5,000 mg/kg were associated with severe 

neurotoxicity (paralysis, and inability to stand) in chickens treated with Fyrquel 150 (Stauffer Chemical Co. 

1971) and Fyrquel 220 (FMC 1977a), respectively. 

A single gavage dose of 5,000 mg/kg Fyrquel 150 produced lethal cholinergic symptoms in a calf; dosage 

levels of 500 and 1,000 mg/kg also produced cholinergic signs in adult cows. Death resulted from paralysis 

about 20 days after dosing (Beck et al. 1977). A calf died 30 days after a single dose of 7,700 mg/kg 

Cellulube 220; decreased erythrocyte acetylcholinesterase was observed (time of onset not reported) and 

axonal degeneration and demyelination in the peripheral and central nervous systems were observed 

beginning 19 days after dosing (Dollahite and Pierce 1969). 

Intermediate-duration oral exposure to Durad 110 produced deaths in chickens associated with the delayed 

development of neuropathy at dosage levels of 4,000 mg/kg/day in a 28-day study and 90 mg/kg/day in a 

90-day study (FMC 1986). At 100 mg/kg/day over a 13-week period, 2 of 12 male and 1 of 12 female rats 

died with exposure to tri-n-butyl phosphate (Healy et al. 1995). Dietary administration of Pydraul 90E for 

90 days providing daily doses of 50 mg/kg/day produced no chemical-related deaths in rats (Monsanto 1979). 

An organophosphate ester hydraulic fluid designated MIL-H-83306 also caused death in 4 of 4 rats exposed 

by gavage to 1,000 mg/kg over a 26-day period (Mattie et al. 1993). 

Gavage exposure to 2,900 mg/kg/day tricresyl phosphate for 16 days, 5 days a week, resulted in death in 5 of 10 

male and 7 of 10 female Fischer 344 rats (NTP 1994). Deaths occurred in 5 of 10 male and 10 of 10 

female B6C3F1 mice at 1,450 mg/kg/day in a parallel study. No deaths occurred in rats in 13-week feeding 

(≤770 mg/kg/day) or gavage studies (5 days a week, 5 800 mg/kg/day) or in 2-year feeding studies at 

≤15 mg/kg/day (NTP 1994). Similar results were obtained in mice where the highest doses were 

1,050 mg/kg/day (13-week feeding), 800 mg/kg/day (13-week gavage), and 37 mg/kg/day (2-year feeding). 

All LOAEL values for each reliable study for death in each species and duration category are recorded in 

Table 2-5 and plotted in Figure 2-5. 
HYDRAULIC FLUIDS 97 

2. HEALTH EFFECTS 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding death in humans after oral 

exposure to polyalphaolefin hydraulic fluids. 

A U.S. military polyalphaolefin hydraulic fluid, MIL-H-83282LT, produced no deaths in adult leghorn 

chickens when two gavage doses of 5,000 mg/kg were administered separated by 21 days; a 21 -day 

observation period followed the second dose administration (Kinkead et al. 1992b). Single gavage 5 ml/kg 

(≈4,250 mg/kg) doses of another U.S. military fluid, MIL-H-83282, produced no deaths in rats within 

14 days of dosing (Kinkead et al. 1985). No deaths occurred within 14 days of dosing in other groups of rats 

treated with one of several other U.S. military polyalphaolefin hydraulic fluids (designated as B85-174 and 

DTNSRDC Nos. N448, N501, N5 17, N5 18, N525, and N527) at single gavage dosage levels of 5 mL/kg 

(≈4,250 mg/kg) or 5,000 mg/kg (Kinkead et al. 1987b; MacEwen and Vemot 1983). No other information 

was located regarding deaths in animals after oral exposure to polyalphaolefin hydraulic fluids. 

2.2.2.2 Systemic Effects 

The highest NOAEL values and all LOAEL values from each reliable study for systemic effects in each 

species and duration category are recorded in Tables 2-4,2-5, and 2-6 and are plotted in Figures 2-4,2-5, and 2-6 

for mineral oil hydraulic fluids, organophosphate ester hydraulic fluids, and polyalphaolefin hydraulic 

fluids, respectively. Because of the uncertainty on whether chickens are a good model for human systemic 

effects (respiratory, cardiovascular, gastrointestinal, hematological, musculoskeletal, hepatic, renal, dermal, 

and ocular), these data are not listed in the LSE tables or figures. However, chickens have been shown to be 

sensitive models for neurotoxicity, and data from chickens are included in the LSE tables and figures. Some of 

the systemic effects resulting from oral exposure to the organophosphate ester hydraulic fluids are most likely 

secondary to their anticholinesterase activity. 

Respiratory Effects. 

Mineral Oil Hydraulic Fluids. Lipoid pneumonia with marked interstitial pneumonitis and pulmonary 

fibrosis was observed in a child accidentally ingesting a lethal dose of automotive transmission fluid (Perrot 

and Palmer 1992). Although the exact composition of the hydraulic fluid was not reported, it is assumed to 

be a mineral oil hydraulic fluid because automotive transmission fluids typically contain 75-80% mineral oil. 

The presence of lipoid/oil droplets in the lungs suggested that some of the hydraulic fluid was aspirated. 
HYDRAULIC FLUIDS 98 

2. HEALTH EFFECTS
 

Granulomatous perbroncholitis (1 of 4) and multifocal bronchiolar/alveolar pneumonia (1 of 4) were noted in 

rats orally exposed to 1,000 mg/kg/day MIL-H-5606 for 26 days (Mattie et al. 1993). It is uncertain if these 

effects were treatment related. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding respiratory effects in humans 

after oral exposure to organophosphate ester hydraulic fluids. 

A number of respiratory effects have been observed in animals acutely exposed to organophosphate ester 

hydraulic fluids by the oral route. Respiratory effects shortly after exposure to organophosphate ester 

hydraulic fluids may be due to acetylcholinesterase inhibition (see Neurological Effects sections for details). 

Rapid respirations were observed shortly after cows received a 500 mg/kg dose of Fyrquel 150 (Beck et al. 

1977). In addition to the acetylcholinesterase inhibition-related effects, histological alterations have been 

observed. Bronchopneumonia and pulmonary atelectasis were observed in rabbits exposed to 120 mg/kg of 

Cellulube 220 (Carpenter et al. 1959), and emphysema, intralobular fibrosis, rapid respiration, and coughing 

were observed in cows exposed to Fyrquel 150 contaminated grass (Beck et al. 1977). Dyspnea was 

observed in goats and cows exposed to 5,000 and 7,700 mg/kg of Cellulube 220, respectively (Dollahite and 

Pierce 1969). Because the symptoms did not occur until 19 days after dosing, it is not likely to be the result 

of acetylcholinesterase inhibition; however, the cause of the dyspnea is not known. In rats acutely exposed to 

5,000 mg/kg of Durad 110 or Durad 220B, chromorhinorrhea was observed. No respiratory effects were 

observed in rats exposed by gavage to ≤350 mg/kg of tributyl phosphate for 18 weeks (Laham et al. 1985). 

Histological examination of the lungs, nose, and trachea revealed no treatment-related lesions in Fischer 344 rats 

and B6C3F1 mice orally exposed to tricresyl phosphate (NTP 1994). Dosing regimens (highest doses in 

mg/kg/day in parenthesis) were as follows: 13-week feeding (rats 770, mice 1,050); 13-week gavage, 5 days a 

week (rats 800, mice 800); and 2-year feeding (rats 15, mice 37). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding respiratory effects in humans or 

animals after oral exposure to polyalphaolefin hydraulic fluids. 

Cardiovascular Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding cardiovascular effects in humans or 

animals after oral exposure to mineral oil hydraulic fluids. 
HYDRAULIC FLUIDS 99 

2. HEALTH EFFECTS
 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding cardiovascular effects in 

humans after oral exposure to organophosphate ester hydraulic fluids. 

No gross or histological alterations in the cardiovascular system or changes in heart weight were observed in 

rabbits acutely exposed to ≤480 mg/kg/day of Cellulube 220 (Carpenter et al. 1959), in chickens acutely 

exposed to ≤720 mg/kg/day of Cellulube 220 (Carpenter et al. 1959), or in rats exposed to 50 mg/kg/day of 

Pydraul90E (Monsanto 1979) for an intermediate duration. Similar results were seen in rats exposed to 

500 mg/kg of a fluid designated MIL-H-83306 (Mattie et al. 1993) for 26 days or to tributyl phosphate for 

18 weeks (Laham et al. 1985). Histological examination of the heart revealed no treatment-related lesions in 

Fischer 344 rats and B6C3F, mice orally exposed to tricresyl phosphate (NTP 1994). Dosing regimens 

(highest doses in mg/kg/day in parenthesis) were as follows: 13-week feeding (rats 770, mice 1,050); 

13-week gavage, 5 days a week (rats 800, mice 800); and 2-year feeding (rats 15, mice 37). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding cardiovascular effects in humans 

after oral exposure to polyalphaolefin hydraulic fluids. 

No cardiovascular effects were observed in rats exposed by gavage to 1,000 mg/kg of a polyalphaolefin fluid 

designated MIL-H-83282 (Mattie et al. 1993). 

Gastrointestinal Effects. 

Mineral Oil Hydraulic Fluids. Subserosal hemorrhaging was observed in the small and large intestine and 

the omentum of a child who accidentally ingested a lethal amount of automobile transmission fluid (Perrot 

and Palmer 1992). Focal gastritis with edema and necrosis were observed in 2 of 4 rats exposed by gavage to 

1,000 mg/kg MILH- 5606 for 26 days (Mattie et al. 1993). 

Organophosphate Ester Hydraulic Fluids. In a case report and in the report of an outbreak of 

organophosphate ester poisoning, vomiting, diarrhea, and gastric upset were found (Goldstein et al. 1988; 

Srivastava et al. 1990). Gastrointestinal effects may well have a neurological component, because of known 

anti-cholinesterase properties of organophosphate esters. Cholinesterase inhibition in the gastrointestinal 
HYDRAULIC FLUIDS 100 

2. HEALTH EFFECTS 

tract is commonly manifested as diarrhea. See Section 2.2.2.4 for a more complete discussion of 

cholinesterase inhibition. 

The most commonly reported gastrointestinal tract effect observed in animals orally exposed to 

organophosphate ester hydraulic fluids is diarrhea. Following acute exposure, diarrhea has been observed in rats 

exposed to 5,775 mg/kg of Durad MP280 (Gaworski et al. 1986) or 5,750 mg/kg Fyrquel 220 (Gaworski 500 

mg/kg/day of Fyrquel 150 (Beck et al. 1977). Diarrhea was also observed in a cow exposed to 8,333 mg/kg/day 

of Cellulube 220 for an intermediate duration (Dollahite and Pierce 1969). Other gastrointestinal effects reported 

in cows acutely exposed include abdominal pain at 500 mg/kg/day of Fyrquel 150 (Beck et al. 1977) and 

tympanitis at 7,700 mg/kg/day of Cellulube 220 (Dollahite and Pierce 1969). Hypersalivation is reported for rats 

exposed to a 325 mg/kg/day dose of tri-n-butyl phosphate (Healy et al. 1995) over 13 weeks and may also be a 

neurological effect, not a true gastrointestinal effect. Histological examination of gastrointestinal tissues 

revealed no treatment-related lesions in Fischer 344 rats and B6C3F1 mice orally exposed to tricresyl phosphate 

(NTP 1994). Dosing regimens (highest doses in mg/kg/day in parenthesis) were as follows: 13-week feeding 

(rats 770, mice 1,050); 13-week gavage, 5 days a week (rats 800, mice 800); and 2-year feeding (rats 15, mice 

37). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding gastrointestinal effects in humans or 

animals after oral exposure to polyalphaolefm hydraulic fluids. 

Hematological Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding hematological effects in humans after oral 

exposure to mineral oil hydraulic fluids. 

A statistically significant reduction of 16% in the percentage of lymphocytes in whole blood was reported in rats 

receiving 1,000 mg/kg/day ME-H-5606 for 26 days (Mattie et al. 1993). 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding hematological effects in 

humans after oral exposure to organophosphate ester hydraulic fluids. 
HYDRAULIC FLUIDS 101 

2. HEALTH EFFECTS 

In rats exposed for intermediate durations at 250 mg/kg/day to tricresyl phosphate for 90 days, 

250 mg/kg/day dibutyl phenyl phosphate for 91 days, or 250 mg/kg/day of trimethyl phosphate for 9 weeks, 

decreased hematocrit, erythrocyte counts and hemoglobin were reported (Healy et al. 1991; Oishi et al. 1982); at 

500-1,000 mg/kg/day of MIL-H-83306, hemoglobin, mean cell hemoglobin, and mean cell hemoglobin 

concentration were reduced (Mattie et al. 1993). In other intermediate-duration studies, no effect on 

hematological parameters was observed in rats exposed to 50 mg/kg/day Pydraul 90 E (Monsanto 1979), < 350 

mg/kg/day of tributyl phosphate (Laham et al. 1985; Oishi et al. 1982), ≤800 mg/kg/day of tricresyl phosphate 

(Latendresse et al. 1994a, 1994b), or ≤250 mg/kg/day trioctyl phosphate (Oishi et al. 1982). Similar results were 

reported in rabbits exposed to ≤480 mg/kg/day Cellulube 220 (Carpenter et al. 1959). No alteration in 

hematological parameters was noted in Fischer 344 rats and B6C3F1, mice orally exposed to tricresyl phosphate 

(NTP 1994). Dosing regimens (highest doses in mg/kg/day in parenthesis) were as follows: 13-week feeding 

(rats 770, mice 1,050); 13-week gavage, 5 days a week (rats 800, mice 800); and 2-year feeding (rats 15, mice 

37). 

Polyalphaolefm Hydraulic Fluids. No studies were located regarding hematological effects in humans after oral 

exposure to polyalphaolefin hydraulic fluids. 

Reductions of approximately 10% in total hemoglobin and mean cell hemoglobin were observed in rats 

receiving 1,000 mg/kg/day of MIL-H-83282LT for 4 weeks (Mattie et al. 1993). A 47% increase in white 

blood cell counts was also observed in this study. No effects on hematological parameters were seen in rats 

similarly exposed to MIL-H-83282 (Mattie et al. 1993). 

Musculoskeletal Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding musculoskeletal effects in humans or 

animals after oral exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding musculoskeletal effects in 

humans after oral exposure to organophosphate ester hydraulic fluids. 

No gross or histological alterations were observed in skeletal muscle following acute exposure to Cellulube 

220. The identified NOAEL values are 480 mg/kg/day in rabbits and 720 mg/kg/day in chickens (Carpenter 

et al. 1959). Muscle wasting was reported for cows exposed to a Fyrquel product containing tri-ortho-cresyl 
HYDRAULIC FLUIDS 102 

2. HEALTH EFFECTS
 

phosphate (Julien et al. 1976). Histological examination of bone revealed no treatment-related lesions in 

Fischer 344 rats and B6C3F1 mice orally exposed to tricresyl phosphate (NTP 1994). Dosing regimens 

(highest doses in mg/kg/day in parenthesis) were as follows: 13-week feeding (rats 770, mice 1,050); 

13-week gavage, 5 days a week (rats 800, mice 800); and 2-year feeding (rats 15, mice 37). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding musculoskeletal effects in humans or 

animals after oral exposure to polyalphaolefin hydraulic fluids. 

Hepatic Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding hepatic effects in humans after oral 

exposure to mineral oil hydraulic fluids. 

A 32% increase in liver weights, along with a 187% increase in peroxisomal beta-oxidation activity, was 

noted in rats exposed to 1,000 mg/kg/day MIL-H-5606 for 26 days (Mattie et al. 1993). The toxicological 

significance of the changes in peroxisomal enzyme activities is unclear. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding hepatic effects in humans 

after oral exposure to organophosphate ester hydraulic fluids. 

No gross or histological hepatic alterations were observed in rabbits exposed to ≤480 mg/kg/day or chickens 

exposed to up to 720 mg/kg/day, respectively, of Cellulube 220 for an acute duration (Carpenter et al. 1959). No 

hepatic effects were reported in rats exposed to 50 mg/kg/day of Pydraul 90E for an intermediate duration 

(Monsanto 1979). Several intermediate-exposure rat studies showed liver effects for organophosphate esters. 

Liver weight increases were shown for tributyl phosphate at 250 mg/kg/day (Laham et al. 1985; Oishi et al. 

1982), trioctyl phosphate at 250 mg/kg/day (Oishi et al. 1982), 2-ethylhexyl diphenyl phosphate at 220 

mg/kg/day (Noda et al. 1984), dibutyl phenyl phosphate at 250 mg/kg/day (Healy et al. 1991), butylated 

triphenyl phosphate at 1,000 mg/kg/day, tricresyl phosphate at 400 mg/kg/day (Latendresse et al. 1994b), and 

MIL-H-83306 at 500 mg/kg/day (Mattie et al. 1993). Blood urea nitrogen was also decreased in rats receiving 

500 mg/kg/day MIL-H-83306 (Mattie et al. 1993). Histopathological evidence for hepatic effects after exposure 

to MIL-H-83306 (increased smooth endoplasmic reticulum) was found in rats exposed to 500 mg/kg/day for 26 

days (Mattie et al. 1993). Changes in hepatic vacuolation and fatty accumulation were seen in rats exposed to 

250 mg/kg/day dibutyl phenyl phosphate for 91 days (Healy et al. 1991). 
HYDRAULIC FLUIDS 103 

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No histopathologic evidence of hepatic changes was seen in Fischer 344 rats orally exposed to tricresyl 

phosphate for 13 weeks in feed (≤770 mg/kg/day) or by gavage for 13 weeks, 5 days a week 

(≤800 mg/kg/day) (NTP 1994). Minimal papillary hyperplasia of the gall bladder mucosa was seen in male 

B6C3F1 mice exposed to tricresyl phosphate in feed at 110 mg/kg/day for 13 weeks; this sign was 

characterized as mild in female mice similarly exposed at 230 mg/kg/day (NTP 1994). These signs were not 

seen in mice exposed for 13 weeks, 5 days a week by gavage at ≤800 mg/kg/day (NTP 1994). In a chronic 

duration study, male mice exposed to 13 mg/kg/day tricresyl phosphate for 105 weeks showed increased 

incidences of clear cell foci, fatty change and ceroid pigmentation (NTP 1994). This effect was not seen in 

female mice exposed to ≤37 mg/kg/day, or in rats exposed for 104 weeks at ≤15 mg/kg/day. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding hepatic effects in humans after oral 

exposure to polyalphaolefin hydraulic fluids. 

Increased serum alkaline phosphatase was observed in rats receiving 1,000 mg/kg/day of MIL-H-83282 for 

4 weeks but not in rats similarly exposed to 1,000 mg/kg/day MIL-H-83282LT (Mattie et al. 1993). 

Increased peroxisomal beta-oxidation rates were seen after exposure to both fluids, but the toxicological 

significance of this finding is unclear (Mattie et al. 1993). 

Renal Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding renal effects in humans after oral 

exposure to mineral oil hydraulic fluids. 

Persistent diuresis, proteinuria, and an increased urinary protein/creatinine ratio were observed in rats 

receiving 1,000 mg/kg/day MIL-H-5606 for 26 days (Mattie et al. 1993). Hyaline droplets in the proximal 

tubules were also noted at histopathological examination. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding renal effects in humans after oral 

exposure to organophosphate ester hydraulic fluids. 

No gross or histological alterations were observed in rabbits exposed to ≤480 mg/kg/day of Cellulube 220 

for an acute duration (Carpenter et al. 1959) or rats exposed to 50 mg/kg/day of Pydraul 90E for an 

intermediate duration (Monsanto 1979). Several reports of urinary bladder hyperplasia were found with 
HYDRAULIC FLUIDS 104 

2. HEALTH EFFECTS
 

exposure levels to dibutyl phenyl phosphate at 50 mg/kg/day (Healy et al. 1991), to tributyl phosphate at 

200 mg/kg/day (Laham et al. 1985) for intermediate-duration exposures. Urinary bladder hyperplasia was 

also reported in rats exposed to 32.5 mg/kg/day tributyl phosphate for 24 months (FMC 1994a). Kidney 

weights and blood urea nitrogen increased in rats at 250 mg/kg/day tributyl phosphate (Oishi et al. 1982) and 

diuresis, proteinuria, and an increase in urinary protein/creatinine ratio were observed in rats exposed to 500 

mg/kg/day MIL-H-83306 for 26 days (Mattie et al. 1993). Signs of renal papillary edema and/or 

necrosis were observed in female rats exposed to 430 mg/kg/day tricresyl phosphate by feed for 13 weeks and in 

males at 750 mg/kg/day (NTP 1994). These signs were not observed when rats were exposed to 

≤800 mg/kg/day for 13 weeks by gavage, 5 days a week (NTP 1994). Evidence for renal tubule regeneration 

was observed in male mice exposed to 900 mg/kg/day tricresyl phosphate in feed for 13 weeks, but not in 

female mice similarly exposed (NTP 1994). As in rats, no renal pathology was observed in mice exposed by 

gavage for 13 weeks, 5 days a week to ≤800 mg/kg/day. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding renal effects in humans after oral 

exposure to polyalphaolefin hydraulic fluids. 

An increased urinary protein/creatinine ratio was observed in rats exposed to 1,000 mg/kg/day MIL-H-83282 

for 4 weeks, and diuresis was seen in rats similarly exposed to MIL-H-83282LT (Mattie et al. 1993). 

Endocrine Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding endocrine effects in humans or animals 

after oral exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding endocrine effects in humans after 

oral exposure to organophosphate ester hydraulic fluids. 

Effects on the adrenal cortex have been observed in intermediate-duration studies for several 

organophosphate hydraulic fluids. Exposure of rats to 1,700 mg/kg/day of a butylated triphenyl phosphate 

fluid resulted in enlargement of the adrenals and lipidosis and cytoplasmic vacuolization of the adrenal 

cortex (Latendresse et al. 1994a). Similar results were observed in this study with exposure to tricresyl 

phosphate at 400 mg/kg/day. An important enzyme in steroid synthesis, neutral cholesteryl ester hydrolase, 

was significantly inhibited with both treatments. In a reproductive toxicity study (Chapin et al. 1988) in 
HYDRAULIC FLUIDS 105 

2. HEALTH EFFECTS
 

which male and female mice were exposed to 62.5 mg/kg of a mixture of tricresyl phosphates containing <0.1% 

pure TOCP, hypertrophy of the zona fasciculata cells and brown degeneration of cells in the juxtamedullary 

zone were observed in the adrenal gland. Cytoplasmic vacuolization of the adrenal cortex was also observed in 

rats exposed to tricresyl phosphate at all doses tested both in feed (55-770 mg/kg/day) and by gavage (50-800 

mg/kg/day) for 13 weeks (NTP 1994). Similar results were observed in mice in 13-week feeding and gavage 

exposures in this study. In a 104-week exposure in rats, this sign was not seen in males at 13 mg/kg/day or 

females at 7 mg/kg/day, but was observed in 36 of 50 females exposed at 15 mg/kg/day. 

Increased severity of ceroid pigmentation was observed in the adrenal cortex of mice exposed to 

7-8 mg/kg/day tricresyl phosphate (the lowest dose tested for 105 weeks) (NTP 1994). 

No histopathological changes in endocrine tissues (adrenal glands and thyroid) were noted in rabbits 

receiving ≤480 mg/kg/day Cellulube 220 for 114 days (Carpenter et al. 1959), or in rats receiving 

≤350 mg/kg/day tributyl phosphate for 18 weeks (Laham et al. 1985). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding endocrine effects in humans or 

animals after oral exposure to polyalphaolefin hydraulic fluids. 

Dermal Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding dermal effects in humans or animals after 

oral exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding dermal effects in humans 

after oral exposure to organophosphate ester hydraulic fluids. 

Scabbing was observed in some rats exposed to Santicizer 154 at 300 mg/kg/day for 14 days (IRDC 1981). 

No gross or histological alterations were observed in chickens exposed to 720 mg/kg/day of Cellulube 220 

for an acute duration (Carpenter et al. 1959). Histological examination of the skin revealed no treatmentrelated 

lesions in Fischer 344 rats and B6C3Fi mice orally exposed to tricresyl phosphate (NTP 1994). Dosing regimens 

(highest doses in mg/kg/day in parenthesis) were as follows: 13-week feeding (rats 770, mice 1,050); 13-week 

gavage, 5 days a week (rats 800, mice 800); and 2-year feeding (rats 15, mice 37). 
HYDRAULIC FLUIDS 106 

2. HEALTH EFFECTS
 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding dermal effects in humans or animals 

after oral exposure to polyalphaolefin hydraulic fluids. 

Ocular Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding ocular effects in humans or animals after 

oral exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding ocular effects in humans 

after oral exposure to organophosphate ester hydraulic fluids. 

No gross or histological alterations were observed in chickens exposed to 720 mg/kg/day of Cellulube 220 

for an acute duration (Carpenter et al. 1959). No longer-term studies examining ocular end points were 

located. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding ocular effects in humans or animals 

after oral exposure to polyalphaolefin hydraulic fluids. 

Body Weight Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding body weight effects in humans after oral 

exposure to mineral oil hydraulic fluids. 

In acute lethality studies, no significant changes in growth were observed in rats administered 5,000 mg/kg of 

Sunsafe F, Quintolubric 9583OW, Houghto-Safe 5047F, or Pyroguard A-443 (Kinkead et al. 1989b, 19SS), or 

4,500 mg/kg of a mineral oil meeting military specifications of MLH-5606 (Kinkead et al. 1985). No 

effect on body weight was observed in rats orally exposed to 1,000 mg/kg/day MIL-H-5606 for 26 days 

(Mattie et al. 1993). 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding body weight effects in 

humans after oral exposure to organophosphate ester hydraulic fluids. 
HYDRAULIC FLUIDS 107 

2. HEALTH EFFECTS
 

Weight loss has been observed in rats exposed to a single dose of 5,775 mg/kg of Durad MP280 (Gaworski 

et al. 1986) in chickens receiving 10,000 mg/kg/day of Reofos 65 and 15,000 mg/kg/day of Fyrquel EHC for 

acute durations (Mortensen and Ladefoged 1992), and in chickens receiving 1,333 mg/kg/day of Durad 110 

for an intermediate duration (FMC 1986). No changes in body weight gain have been reported in rats and 

chickens exposed to a single dose of ≥5,000 mg/kg of a number of hydraulic fluids including 

cyclotriphosphazene (Kinkead et al. 1992c; MacEwen and Vemot 1985), Durad 550B (FMC 1992a), Durad 

220B (FMC 1990a), Durad 110 (FMC 1990a), Durad 300 (FMC 1990a), and Fyrquel 220 (Gaworski et al. 1986; 

Kinkead et al. 1992a). Maternal rats showed a 35% reduced body weight gain in a 10-day exposure to 

5,000 mg/kg/day of Santicizer 141 (Robinson et al. 1986). In a dose-finding study using 5 pregnant rats per 

group, a 12% decrease in maternal weight gain was noted at 200 mg/kg/day tributyl phosphate (Noda et al. 

1994) but in a larger study with 20 animals per group, only minor body weight reductions were observed at 

500 mg/kg/day. Several intermediate-duration studies showed reduction in body weight gain in rats or mice. 

Thirteen-week feeding exposures to tricresyl phosphate in rats at 430 mg/kg/day were associated with an 

11% reduction in body weight in both males and females (NTP 1994). Exposure to 750 mg/kg/day caused a 

33% decrease in body weight in males. Treatment by gavage for 13 weeks, 5 days a week did not affect 

female body weight at ≤800 mg/kg/day; male body weight was decreased 13% at this dose (NTP 1994). 

Body weight effects were also reported in mice in this study, decreases greater than 10% were seen in female 

mice at 530 mg/kg/day and above and in males at 900 mg/kg/day exposed to tricresyl phosphate by feed. 

Gavage doses greater than 400 mg/kg/day also caused decreased body weight (NTP 1994). Dibutyl phenyl 

phosphate exposure for 91 days at 250 mg/kg/day in female rats was observed to cause a 15% body weight 

reduction (Healy et al. 1991). Butylated triphenyl phosphate exposure at 1,000 mg/kg/day for 106 days caused 

an 11-17% decrease in body weight in Fischer 344 rats (Latendresse et al. I994b). Similar results have been 

reported with exposure to tributyl phosphate in rats: a 15% decrease at 300 mg/kg/day for 18 weeks (Laham et 

al. 1985) and an 11% decrease at 250 mg/kg/day for 9 weeks (Oishi et al. 1982). No changes in body weight 

gain were observed in rats exposed to 50 mg/kg/day of Pydraul 90E (Monsanto 1979) and chickens exposed to 

270 mg/kg/day of Durad 110 (FMC 1986) for intermediate durations. Twoyear feeding exposure of rats and 

mice to tricresyl phosphate at 13-37 mg/kg/day produced no effect on body weight (NTP 1994). 

Polyalphaolefzn Hydraulic Fluids. No studies were located regarding body weight effects in humans after 

oral exposure to polyalphaolefm hydraulic fluids. 
HYDRAULIC FLUIDS 108 

2. HEALTH EFFECTS 

No changes in body weight gain were observed in rats receiving single doses of 4,250 mg/kg of 

polyalphaolefin hydraulic fluids designated as DTNSRDC N448, N501, N5 17, N5 18, N525, and N527 

(MacEwen and Vemot 1983); MIL-H-83282 (Kinkead et al. 1985); 5,000 mg/kg of B85-174 (Kinkead et al. 

1987b); or MIL-H-83282LT (Kinkead et al. 1992b). Similar results were reported in 4-week exposures to 

1,000 mg/kg/day MIL-H-83282 and MIL-H-83282LT in rats (Mattie et al. 1993). 

2.2.2.3 Immunological and Lymphoreticular Effects 

Mineral Oil Hydraulic Fluids. No studies were located regarding immunological or lymphoreticular effects 

in humans or animals after oral exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding immunological or 

lymphoreticular effects in humans after oral exposure to organophosphate ester hydraulic fluids. 

Rats exposed for 6 weeks to 2.5 mg/kg/day of tricresyl phosphate showed decreased serum antibody titers to 

tetanus and decreased immunoglobin levels (Banerjee et al. 1992). In a 16-day gavage study with tricresyl 

phosphate, serious effects on immunological/lymphoreticular tissues were observed (NTP 1994). Male and 

female rats that received 2900 mg/kg/day tricresyl phosphate had increased incidences of lymphoid depletion 

and necrosis of the spleen, thymus and the mandibular lymph node; the severity of these lesions ranged from 

mild to marked (NTP 1994). Significantly reduced thymus weight was observed at 1,450 mg/kg/day. Necrosis of 

the spleen, thymus, and mandibular lymph node and lymphoid depletion of the thymus were also observed in 

mice at 2,900 mg/kg/day (NTP 1994). The NOAEL value in this study was 1,452 mg/kg/day. At reduced doses 

in subsequent studies, histological examination of bone marrow, spleen, thymus and mandibular and mesenteric 

lymph nodes revealed no treatment-related lesions in Fischer 344 rats and B6C3F1 mice orally exposed to 

tricresyl phosphate (NTP 1994). Dosing regimens (highest doses in mg/kg/day in parenthesis) were as follows: 

13-week feeding (rats 770, mice 1,050); 13-week gavage, 5 days a week (rats 800, mice 800); and 2-year 

feeding (rats 15, mice 37). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding immunological or lymphoreticular 

effects in humans after oral exposure to polyalphaolefin hydraulic fluids. 
HYDRAULIC FLUIDS 109 

2. HEALTH EFFECTS
 

Histopathological analysis of the thymus, lymph nodes, and spleen of rats exposed to 1,000 mg/kg/day MIL-H83282 or MIL-H-83282LT for 4 weeks revealed no treatment-related changes in these tissues (Mattie et al. 

1993). 

2.2.2.4 Neurological Effects 

The highest NOAEL values and all LOAEL values from each reliable study for neurological effects in each 

species and duration category are recorded in Tables 2-4,2-5, and 2-6 and plotted in Figures 2-4,2-5, and 

2-6 for mineral oil hydraulic fluids, organophosphate ester hydraulic fluids, and polyalphaolefin hydraulic 

fluids, respectively. 

Mineral Oil Hydraulic Fluids. No studies were located regarding neurological effects in humans after 

oral exposure to mineral oil hydraulic fluids. 

Mineral oil hydraulic fluids sometimes contain organophosphate ester additives; however, no symptoms of 

acute cholinergic toxicity or delayed neuropathy were seen in several studies with animals treated with single 

oral doses of mineral oil hydraulic fluids. Single gavage doses of several hydraulic fluids at doses of 

≈5,000 mg/kg produced no clinical signs of neurotoxicity within 14 days of dosing in Fischer 344 rats; tested 

fluids include several water-in-oil emulsion types of hydraulic fluids (Pyroguard A-443, Houghto-Safe 

5047F, Quintolubric 9583OW, and Sunsafe F) (Kinkead et al. 1987a, 1988) and a U.S. military MIL-H-5606 

fluid (Kinkead et al. 1985). Single gavage doses of a MIL-H-5606 hydraulic fluid (5 mL/kg or 

≈4,500 mg/kg) produced no clinical signs of acute neurotoxicity or delayed neuropathy in Leghorn chickens 

within 2 1 days of dosing, nor did it produce histological changes in peripheral or central nervous system 

(tissues examined were not specified) like those produced in positive control chickens treated with 500 mg/kg 

tri-ortho-cresyl phosphate (Kinkead et al. 1985). 

No studies were located regarding neurological effects in animals after intermediate or chronic-duration oral 

exposures to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. A brief overview of organophosphate ester neurotoxicity 

is presented in Section 2.2.1.4. 
HYDRAULIC FLUIDS 110 

2. HEALTH EFFECTS
 

A number of human poisonings have been reported, dating back to the 1930s in which the primary effects of 

tricresyl phosphates were neurological (Goldstein et al. 1988; Senanayake and Jeyaratnam 1981; Srivastava et 

al. 1990). Though doses are difficult to ascertain, estimated exposure to 50-100 mg/kg/day resulted in facial 

weakness, severe dysarthria (difficulty of speech due to muscular control problems stemming from central or 

peripheral nerve damage), loss of reflexes and myoclonic jerking in a 4-year-old boy (Goldstein et al. 1988) and 

polyneuropathy in young Sri Lankan girls (Senanayake and Jeyaratnam 1981) exposed to 5-10 mg/kg/day for 14 

days. The boy fully recovered in 5 weeks. One year after ingesting 5-7 doses of tricresyl phosphate, the young 

women still reported reduced muscular strength. Abou-Donia and Lapadula (1990) have estimated that there 

have been more than 40,000 cases of OPIDN. More than 20,000 cases occurred in the United States in the 1930s 

as a result of people consuming a contaminated extract of ginger called “Jamaican Ginger.” Subsequent analysis 

revealed that these cases of delayed neuropathy were caused by the presence of a specific isomer of tricresyl 

phosphate, tri-ortho-cresyl phosphate (TOCP), in the extract. 

Many of the studies on the neurological effects of oral exposure to organophosphate ester hydraulic fluids in 

animals have employed chickens as models instead of the more commonly used rodent models. For reasons that 

are not well understood, organophosphate-induced delayed neuropathy can be induced in chickens and cats, but 

not in mice or rats (Abou-Donia and Lapadula 1990). 

Several organophosphate ester hydraulic fluids produced neurological effects, including acute cholinergic 

toxicity and signs of organophosphate-induced delayed neuropathy (OPIDN), in chickens after acute gavage 

administration (see Table 2-5). Fyrquel EHC produced incoordination, inability to stand and eventually 

ataxia in chickens after a single dose of 11,350 mg/kg (Stauffer Chemical Co. 1980); spinal cord lesions with 

minor signs of neuropathy at 5,000 mg/kg and ataxia at 10,000 mg/kg (Mortensen and Ladefoged 1992); and 

decreased activities of brain neurotoxic esterase and plasma cholinesterase without signs of neurotoxicity at 

1,140 mg/kg (Stauffer Chemical Co. 1981). Brain neurotoxic esterase activity was reduced 94% by a single dose 

of 11,350 mg/kg Fyrquel EHC, a dose which produced ataxia (Stauffer Chemical Co. 1980). Chickens dosed 

with either tributyl phosphate or dibutyl phenyl phosphate exhibited apparent cholinergic signs (salivation, 

diarrhea, impaired respiration) for 2-4 days after single doses near the LD50 for these compounds but did not 

show significant reduction in brain acetylcholinesterase or further signs of neurotoxicity (Canington et al. 1989). 

Tributoxyethyl phosphate significantly inhibited brain acetylcholinesterase (45%), but neither acute cholinergic 

signs nor further signs of neurotoxicity developed. Inhibition of NTE and motor incoordination were observed in 

chickens receiving a single oral dose of 11,700 mg/kg isopropyl triphenyl phosphate (Sprague et al. 1984), but 

OPIDN did not develop. Reofos 65 produced minor 
HYDRAULIC FLUIDS 111 

2. HEALTH EFFECTS
 

histological changes in peripheral nerves without cholinergic symptoms or signs of delayed neuropathy at 

doses ≤5,000 mg/kg (Mortensen and Ladefoged 1992). 

Tricresyl phosphate caused ataxia, axonal degeneration and reduction of NTE at 60 mg/kg/day over 10 weeks in 

chickens (Freudenthal et al. 1993). Skydrol LD-4 and Skydrol 500B-4 produced decreased activities of brain 

neurotoxic esterase (-46%), brain acetylcholinesterase (-18%), and plasma butyrylcholinesterase (-78%), as well 

as cholinergic symptoms at respective LD50 levels of 2,594 and 2,559 mg/kg in chickens. No clear signs of 

delayed neuropathy developed in survivors at doses as high as 5,000 mg/kg (Monsanto 1987c, 1987d). U.S. 

military fluids designated as Durad MP280 and Cellulube 220 produced distinct clinical signs of OPIDN (ataxia 

and paralysis) in chickens after 5 days of dosing with 240 and 60 mg/kg/day, respectively (Carpenter et al. 1959; 

Gaworski et al. 1986). A tricresyl phosphate fluid designated TCP-1 caused leg and wing weakness and 

paralysis in chickens receiving 240 mg/kg/day for 5 days (Friess et al. 1959). Fyrquel 220 and Fyrquel 150 each 

produced distinct clinical signs of OPIDN in chickens after 5-day administrations of respective doses of 5,000 

mg/kg/day (FMC 1977a) and 240 mg/kg/day (Stauffer Chemical Co. 1971). Fyrquel 220 at a dose of 420 

mg/kg/day had no effect (FMC 1977a). Fourteen days of tricresyl phosphate exposure in mice caused 

cholinergic signs such as piloerection, tremors, and lethargy at 2,275 mg/kg/day, but not OPIDN (Chapin et al. 

1988) 

Another group of organophosphate ester hydraulic fluids produced no signs of neurotoxicity in chickens 

following acute gavage administration. Fluids that produced no neurotoxic signs in chickens (with the 

maximum dose level at which they were tested in parenthesis) included U.S. military fluids MIL-H-19457B 

and MIL-H-19457(3 (420 mg/kg/day for 5 days [Gaworski et al. 1986; Kinkead et al. 1989b]), Pydraul 50E 

(20,000 mg/kg/day for 3 days [Monsanto 19791 and 5,000 mg/kg/day for 4 or 5 days [Ciba-Geigy 1973; 

FMC 1977b]), Pydraul 29ELT (20,000 mg/kg/day for 3 days [Monsanto 1979]), and Pydraul 90E 

(20,000 mg/kg/day for 3 days [Monsanto 19791). Each of these studies provided sufficient periods 

(>18 days) to observe signs of delayed neuropathy. 

Administration of organophosphate ester hydraulic fluids has produced neurological effects in-species other 

than chickens. Cellulube 220 produced delayed hindlimb paralysis in two goats 19-36 days after single 

doses of 5,000 or 10,000 mg/kg, and incoordination, accompanied with demyelination and axonal swelling in 

peripheral nerves, and increased cellularity in dorsal and ventral spinal nerve roots in a calf 19 days after a 

single dose of 7,700 mg/kg (Dollahite and Pierce 1969). Beck et al. (1977) observed acute signs of 

cholinesterase inhibition (diarrhea, rapid respiration, salivation, miosis) that eventually led to death in calves 
HYDRAULIC FLUIDS 112 

2. HEALTH EFFECTS
 

given 500, 1,000, or 2,000 mg/kg/day Fyrquel 150 by gavage for 10 days. The dose level did not influence 

the onset or severity of clinical signs. Delayed hindlimb paralysis developed in two cows given single gavage 

doses of 500 or 1,000 mg/kg Fyrquel 150; histological examination of the spinal cord revealed axonal 

degeneration and demyelination (Beck et al. 1977). The onset of hindlimb paralysis was observed after the 

cessation of cholinesterase effects on either day 15 or 19. 

No clinical signs of neurotoxicity were observed in rats after acute gavage administration in lethality studies 

of several organophosphate ester hydraulic fluids tested at dose levels as high as 5,000 mg/kg. Tested 

materials included Durad 300 (FMC 1990a), Durad 110 (FMC 1990a), Durad 220B (FMC 1990a), Durad 

550B (FMC 1992a), and a cyclotriphosphazene based fluid (Kinkead et al. 1992c; MacEwen and Vemot 

1985). Durad 125 produced an 85% inhibition of serum cholinesterase in rats, without producing cholinergic 

signs (tremors, diarrhea) like those produced in positive controls treated with tri-ortho-cresyl phosphate 

(FMC 199 la). Cellulube 220, a fluid that produced definite signs of delayed neuropathy in goats and cows, 

produced no signs of neurotoxicity in rats treated with 20,000 mg/kg (Dollahite and Pierce 1969). 

No studies were located regarding neurological effects in animals after chronic oral exposure to 

organophosphate ester hydraulic fluids, but three hydraulic fluids have been tested for neurological effects in 

animals after intermediate dose administration. In a 90-day dietary study, administration of 50 mg/kg/day 

Pydraul90E to albino rats produced no effects on brain, plasma, or red blood cell cholinesterase activities, 

compared with controls, and no histological effects. The report did not mention the extent of the histological 

examination nor the occurrence of clinical signs of neurotoxicity (Monsanto 1979). In a 28day study with 

domestic chickens gavaged daily with Durad 110, an increased incidence of chickens with clinical signs of 

ataxia was observed at 1,333 mg/kg/day, but not at 444 mg/kg/day (FMC 1986). In a 90-day gavage study 

with Durad 110, chickens treated with 90 mg/kg/day displayed an increased incidence of ataxia and axonal 

damage in the spinal cord and peripheral nerves. The NOAEL for neurological effects was 20 mg/kg/day 

(FMC 1986). Cellulube 220 administered at a dose level of ≈8,333 mg/kg/day three times over a 56-day 

period produced incoordination in a calf after the last dose administration; axonal swelling in the peripheral 

nervous system was observed (Dollahite and Pierce 1969). 

Neurological effects have also been observed with several organophosphate esters used currently or formerly in 

hydraulic fluids. Dibutyl phenyl phosphate decreased erythrocyte and brain acetylcholinesterase levels in female 

rats exposed by feed for 91 days at 250 mg/kg/day but not at 50 mg/kg/day (Healy et al. 1991). Male rats 

similarly exposed were unaffected. In Fischer 344 rats receiving tricresyl phosphate by gavage for 
HYDRAULIC FLUIDS 113 

2. HEALTH EFFECTS
 

16 days, decreased activity and grip strength were noted in females at 1,450 mg/kg/day and in males at 

2,900 mg/kg/day (NTP 1994); no-effect levels were 730 mg/kg/day in females and 1,450 mg/kg/day in 

males. Thirteen-week exposures by gavage or feed in this strain of rats at ≤800 mg/kg/day tricresyl 

phosphate had no effect on neurological parameters or histology of brain, spinal cord or sciatic nerve (NTP 

1994). In a 2-year feeding study with tricresyl phosphate in rats (0, 3, 6, or 13 mg/kg/day in males; 0,4,7, or 

15 mg/kg/day in females), no histological evidence of treatment-related damage to nervous system tissues 

(brain, spinal cord, and sciatic nerve) was observed (NTP 1994). 

Tricresyl phosphate exposure by feed for 13 weeks resulted in tremors in male B6C3F, mice receiving 

900 mg/kg/day and decreased forelimb grip strength at 380 mg/kg/day (NTP 1994). Female mice exposed at 530 

mg/kg/day also showed decreased hindlimb strength along with histopathological evidence of axonal 

degeneration in the spinal cord and sciatic nerve. NOAELs in this study were 180 mg/kg/day in males and 

230 mg/kg/day in females. Tricresyl phosphate was more potent for inducing neurological effects when given by 

gavage. A 13-week exposure by gavage (5 days a week) produced multifocal degeneration of the spinal cord and 

sciatic nerve at 100 mg/kg/day (NTP 1994). No histologic evidence of treatment-related damage to brain, spinal 

cord, or sciatic nerve was seen in mice after a 2-year feed exposure to ≤37 mg/kg/day tricresyl phosphate (NTP 

1994). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding neurological effects in humans 

after oral exposure to polyalphaolefin hydraulic fluids. 

In a series of acute lethality studies on U.S. military fluids, single gavage doses (4,250 or 5,000 mg/kg) of 

one of several polyalphaolefin hydraulic fluids did not produce signs of neurological toxicity in rats within 

14 days of dosing. Tested materials included fluids designated as DTNSRDC Nos. N448, N501, N517, 

N518, N525, and N527 (MacEwen and Vemot 1983); B85-174 (Kinkead et al. 1987b); MIL-H-83282LT 

(Kinkead et al. 1992b); MIL-H-83282 (Kinkead et al. 1985). Single gavage doses of MIL-H-83282 

(7.5 mL/kg or 6,375 mg/kg) or MIL-H-83282LT (5,000 mg/kg) did not produce delayed neuropathy in 

Leghorn chicken hens within 21 days of dosing (Kinkead et al. 1985, 1992b). No other information was 

located on neurological effects in animals after oral exposure to polyalphaolefin hydraulic fluids. 
HYDRAULIC FLUIDS 114 

2. HEALTH EFFECTS 

2.2.2.5 Reproductive Effects 

No studies were located regarding reproductive effects in humans or animals after oral exposure to mineral oil 

hydraulic fluids or to polyalphaolefin hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding reproductive effects in 

humans after oral exposure to organophosphate ester hydraulic fluids. 

Data suggestive of adverse reproductive effects after an assumed acute oral exposure to organophosphate 

ester hydraulic fluids are restricted to an observation of reduced lactation and delayed estrus with no 

coincident gross lesions in cows that ingested grass contaminated with Fyrquel 150 (Beck et al. 1977). 

There are a number of studies of intermediate duration which note reproductive effects in experimental 

animals. Rats exposed to 400 mg/kg/day tricresyl phosphate and 1,900 mg/kg/day butylated triphenyl 

phosphate for 40 days by gavage showed hypertrophy and vacuolization of ovarian interstitial cells 

(Latendresse et al. 1993). These results are supported by a study in which rats exposed by gavage for 20,40, and 

60 days showed lipidosis in ovarian interstitial cells at 400 mg/kg/day tricresyl phosphate and 

1,700 mg/kg/day butylated triphenyl phosphate, as well as testicular degeneration and decreased testicular 

weight at 400 mg/kg/day tricresyl phosphate (Latendresse et al. 1994a). An increase in abnormal sperm 

morphology and necrosis of seminiferous tubules were noted in male rats exposed to 100 mg/kg/day tricresyl 

phosphate by gavage, while decreased fertility and vacuolar cytoplasmic alteration of ovarian interstitial cells 

were noted in female rats exposed at 200 mg/kg/day to this compound for 66 days (Carlton et al. 1987). 

Latendresse et al. (1994b) reported decreased numbers of litters in rats exposed by gavage to 600, 1,000, and 

1,700 mg/kg/day butylated triphenyl phosphate and 400 mg/kg/day tricresyl phosphate for 98 days. In the same 

study, 100% infertility, decreased testicular and epididymal weights, and increased ovarian weights were seen at 

400 mg/kg/day tricresyl phosphate; and abnormal estrous cycles and decreased uterine weights were noted in 

female rats exposed to 1,000 mg/kg/day butylated triphenyl phosphate, all for 106 days. Decreased mating and 

fertility indices and decreased number of live pups per litter were seen after 105 days of exposure to 124 

mg/kg/day in the feed (Chapin et al. 1988) but not at 62.5 mg/kg/day. 

Reproductive changes in rats and mice were found in intermediate- and chronic-duration oral studies performed 

with tricresyl phosphate by the National Toxicology Program (NTP 1994). Ovarian interstitial 

cell hypertrophy was a common finding in both species and occurred at the lowest doses tested in rats in a 
HYDRAULIC FLUIDS 115 

2. HEALTH EFFECTS
 

13-week feeding study in rats (65 mg/kg/day) and a 13-week gavage study (50 mg/kg/day). In mice, this sign 

was observed at 50 mg/kg/day in a 13-week gavage study. These effects were seen at all doses tested, but did 

not increase in severity with dose. Interstitial cell cytoplasmic vacuolization was observed at 530 mg/kg/day in a 

13-week feeding study, but hypertrophy was not. Seminiferous tubule atrophy was observed in rats at 430 

mg/kg/day in 13-week feeding studies and at 400 mg/kg/day in 13-week gavage studies. Similar results were 

seen in mice treated by gavage, but not in mice exposed to tricresyl phosphate by feeding (NTP 1994). 

In contrast, several studies did not report reproductive effects. Laham et al. (1985) reported no significant 

changes in the testes or ovaries in rats exposed by gavage to a high dose of 350 mg/kg/day tri-n-butyl 

phosphate for 18 weeks. No gross or histological alterations in the reproductive tract after acute oral 

exposure were observed in male rabbits gavaged with 480 mg/kg Cellulube 220 (Carpenter et al. 1959) or in 

chickens given ≤420 mg/kg of MIL-H-19457B or MIL-H-19457C (Kinkead et al. 1989b). No changes in 

gonad weight or histology were observed in male or female rats after oral exposure to Pydraul90E at a 

dietary concentration of 50 mg/kg/day for 90 days (Monsanto 1979). 

In a 2-year feeding study in rats, ovarian interstitial cell hyperplasia was observed in rats exposed to 

15 mg/kg/day tricresyl phosphate, but no effect was seen at 7 mg/kg/day (NTP 1994). No effects on male 

reproductive tissues were seen at ≤13 mg/kg/day. No effects on reproductive tissues in either sex were 

observed in 2-year feeding studies in mice (27 mg/kg/day in males, 37 mg/kg/day in females). 

A neurotoxic isomer of tricresyl phosphate (tri-ortho-cresyl phosphate) altered testicular morphology and 

function as well as reproductive function after oral exposure in rats (Somkuti et al. 1987a, 1987b) (see 

Section 2.5). 

2.2.2.6 Developmental Effects 

No studies were located regarding developmental effects in humans or animals after oral exposure to mineral oil 

hydraulic fluids or to polyalphaolefin hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding developmental effects 

in humans after oral exposure to organophosphate ester hydraulic fluids. 
HYDRAULIC FLUIDS 116 

2. HEALTH EFFECTS
 

Data suggestive of adverse developmental effects after an assumed acute oral exposure to organophosphate ester 

hydraulic fluids are restricted to an observation of retarded growth in calves of cows with reduced lactation, and 

“abnormal” growth in a calf of a cow that showed moderate ataxia, after the cows ingested grass probably 

contaminated with Fyrquel 150 (Beck et al. 1977). 

None of the calves of 10 cows showed clinical signs of neurotoxicity after the cows were orally exposed to an 

unknown quantity of a Fyrquel hydraulic fluid reclamation waste that according to the authors possibly 

contained tri-ortho-cresyl phosphate (TOCP), and that was applied liberally to their backs one time as a 

treatment for ringworm (Julian et al. 1976). The cows were seen licking their backs and the backs of other 

cows; thus, the cows were orally and dermally exposed to organophosphate ester hydraulic fluids. 

With acute-duration exposure to tricresyl phosphate and dibutyl phenyl phosphate, decreased litter size and 

pup survivability were found at 400 mg/kg/day (Carleton et al. 1987) and 50 mg/kg/day (Healy et al. 1991), 

respectively. Exposure to Santicizer 154 caused no developmental changes in the offspring of rats treated 

with ≤2,000 mg/kg/day for 14 days (Robinson et al. 1986). An 8% decrease in pup weight was reported in 

the offspring of rats treated during gestation with 1,000 mg/kg/day Phosflex 5 1 B, although the authors 

considered this effect to be secondary to maternal toxicity (Stauffer 1982). Increased incidence of 

rudimentary lumbar ribs were noted in offspring of rat dams treated with tributyl phosphate at 500 mg/kg/day 

over gestation days 7-17 (Noda et al. 1986). Dibutyl phenyl phosphate, a component of some 

organophosphate ester hydraulic fluids, decreased the postnatal survival of rat pups. Decreased survival to 

day 4 was observed in the F1a pups (first litter) of rats exposed to 50 or 250 mg/kg/day and F1b pups (second 

litter) of rats exposed to 5 or 50 mg/kg/day (but not to 250 mg/kg/day). The number of live offspring at 

weaning was also diminished in the F1a pups in 50 and 250 mg/kg/day groups and F2, pups of the 

250 mg/kg/day group. In an attempt to determine if the reduced survival was due to in utero effects, the F1b 

pups of the 250 mg/kg/day pups were cross-fostered with control pups. Reduced survival at day 4 and 

weaning was observed in the control pups raised by the high-dose rats. Decreased body weight gains were 

observed in the F, dams (parental) exposed to 250 mg/kg/day and F1, dams exposed to 50 and 250 mg/kg/day. 

Effects on control pups, potentially exposed via treated dams are equivocal. Although surviva1 was reduced, the 

cause is not clear (Healy et al. 1991). Additionally, no changes were seen in the type or incidence of 

developmental anomalies observed in the pups of male and female rats that had been orally exposed to triphenyl 

phosphate, another component of some organophosphate ester hydraulic fluids at doses < 690 mg/kg/day for 91 

days, including through mating and gestation (Welsh et al. 1987). 
HYDRAULIC FLUIDS 117 

2. HEALTH EFFECTS
 

No intermediate- or chronic-duration oral studies examining developmental effects in animals were located. 

2.2.2.7 Genotoxic Effects 

Mineral Oil Hydraulic Fluids. No studies were located regarding genotoxic effects in humans or 

animals after oral exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding genotoxic effects in 

humans after oral exposure to organophosphate ester hydraulic fluids. 

The incidence of nuclear anomalies in bone marrow interphase cells significantly increased (p<0.05) in 

Chinese hamsters gavaged on 2 consecutive days with 2,500 and 5,000 mg/kg/day of Reofos 50 (Ciba-Geigy 

1984a), but not in those dosed with 1,250 mg/kg/day. The types of anomalies used in scoring were single 

“Howell-Jolly” bodies, fragments of nuclei in erythrocytes, micronuclei in erythroblasts, micronuclei in 

leucopoietic cells, and polyploidal cells. 

Administration of single doses of ≤5,000 mg/kg Reofos 50 in sodium-carboxymethyl cellulose or Reolube 

HYD46 in arachid oil by gavage oil to four male and four female Chinese hamsters did not induce significant 

increases in sister chromatid exchanges in bone marrow cells (Ciba-Geigy 1983b, 1984b). Other 

genotoxicity studies for organophosphate ester hydraulic fluids are discussed in Section 2.5. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding genotoxic effects in humans or 

animals after oral exposure to polyalphaolefin hydraulic fluids. 

2.2.2.8 Cancer 

Mineral Oil Hydraulic Fluids. No studies were located regarding cancer in humans or animals after oral 

exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding cancer in humans after 

oral exposure to organophosphate ester hydraulic fluids. 
HYDRAULIC FLUIDS 118 

2. HEALTH EFFECTS 

A 2-year carcinogenicity bioassay of tricresyl phosphate in mice and rats showed no evidence of 

carcinogenicity in these species (NTP 1994). Doses (consumed in feed) were 137 mg/kg/day in mice and 

≤15 mg/kg/day in rats. Dietary administration of tributyl phosphate was associated with transitional and 

squamous cell carcinomas of the bladder in rats after 2 years of exposure at 143.3 mg/kg/day (FMC 1994a). 

An increased incidence of hepatocellular adenomas in the liver was observed in mice after dietary 

administration of 455 mg/kg/day tributyl phosphate for 18 months (FMC 1994b). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding cancer in humans or animals 

after oral exposure to polyalphaolefin hydraulic fluids. 

2.2.3 Dermal Exposure 

The NOAEL and LOAEL values for each effect after dermal exposure are shown in Tables 2-7,2-8, and 2-9 

for mineral oil hydraulic fluids, organophosphate ester hydraulic fluids, and polyalphaolefin hydraulic fluids, 

respectively. 

2.2.3.1 Death 

Mineral Oil Hydraulic Fluids. No studies were located regarding death in humans after dermal 

exposure to mineral oil hydraulic fluids. 

Several water-in-oil emulsion hydraulic fluids (Houghto-Safe 5047F, Sunsafe F, Pyroguard A-443, and 

Quintolubric 95830W) produced no deaths or signs of toxicity in rabbits within 14 days of single 24-hour 

exposures to occluded doses of 2,000 mg/kg spread evenly onto the backs and sides of the animals (Kinkead et 

al. 1987a, 1988). A U.S. military fluid designated as MIL-H-5606 likewise produced no deaths in rabbits within 

14 days of 24-hour exposures to occluded doses of 1,800 mg/kg spread evenly onto the backs and sides of the 

animals (Kinkead et al. 1985). Additional information on lethality of mineral oil hydraulic fluids in animals after 

oral exposure was not located. -. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding death in humans after 

dermal exposure to organophosphate ester hydraulic fluids. 













HYDRAULIC FLUIDS 132 

2. HEALTH EFFECTS 

No deaths occurred in rats after dermal exposure to Durad 220B, Durad 300, or Durad 110 under occluded 

conditions for 24 hours at dosage levels of 2,000 mg/kg (FMC 1990a). Dermal exposure to 2,890 mg/kg 

doses of a cyclotriphosphazene hydraulic fluid for 24 hours under occluded conditions likewise produced no 

deaths in rabbits (Kinkead et al. 1992c; MacEwen and Vemot 1985). Deaths associated with severe 

cholinergic symptoms and symptoms of delayed neuropathy occurred in a group of 50 cattle treated dermally 

with about 1.52 L of waste from reclamation of a Fyrquel hydraulic fluid (Julian et al. 1976). The material was 

poured over the backs of the animals as a ringworm treatment. Exposure was expected to have been by the oral 

route as well as by dermal contact, because the cows were seen licking their backs or the backs of other cows; 

14 of 50 cows died within 4 weeks of exposure. The authors stated that this fluid may have been contaminated 

with tri-ortho-cresyl phosphate. 

Johannsen and colleagues (1977) report dermal LD50 values for rabbits at levels of >3,700 mg/kg for a group of 

triaryl phosphates, >5,000 mg/kg for dibutyl phenyl phosphate, 5,000 mg/kg for both asymmetrical and 

symmetrical triaryls, and >3,100 mg/kg for tributyl phosphate. This study looked at structural activity 

relationships for the organophosphate esters. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding death in humans after dermal 

exposure to polyalphaolefin hydraulic fluids. 

Several U.S. military polyalphaolefin hydraulic fluids (designated as B85-174, MJL-H-83282, MLL-H83282, and DTNSBDC Nos. N448, N501, N5 17, N5 18, N525, and N527) produced no deaths in rabbits 

within 14 days of single 24-hour occluded exposures to either 2,000 mg/kg (B85-174 and MJL-H-83232LT) 

or 5 mL/kg (= 1,700 mg/kg; the remaining fluids were applied at this level) (Kinkead et al. 1987b; MacEwen 

and Vemot 1983). The test materials were spread evenly over the backs and sides of the animals. 

2.2.3.2 Systemic Effects 

The highest NOAEL and all LOAEL values from each reliable study for systemic effects in each species and 

duration category are recorded in Tables 2-7,2-8, and 2-9 for mineral oil hydraulic fluids, organophosphate 

ester hydraulic fluids, and polyalphaolefin hydraulic fluids, respectively. 
HYDRAULIC FLUIDS 133 

2. HEALTH EFFECTS 

Respiratory Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding respiratory effects in humans or animals 

after dermal exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding respiratory effects in humans 

after dermal exposure to organophosphate ester hydraulic fluids. 

Respiratory effects have been observed in one dermal toxicity study. Of six rabbits exposed to an 

unspecified amount of Cellulube 220 for an intermediate duration, one died on day 36 of weakness and 

dyspnea of 4%hour duration (Carpenter et al. 1959). Respiratory effects were not observed in rabbits 

dermally exposed to 1,000 mg/kg of cyclotriphosphazene for an intermediate duration (Kinkead et al. 1989c, 

1990). No acute- or chronic-duration animal studies examining respiratory tract effects were located. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding respiratory effects in humans or 

animals after dermal exposure to polyalphaolefin hydraulic fluids. 

Cardiovascular Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding cardiovascular effects in humans or 

animals after dermal exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding cardiovascular effects in 

humans after dermal exposure to organophosphate ester hydraulic fluids. 

Several animal studies conducted histological examination of the heart following intermediate-duration 

dermal exposure to organophosphate ester hydraulic fluids. No cardiovascular effects were observed in rats 

exposed to 5,750 mg/kg/day of Fyrquel 220 (MacEwen and Vemot 1983), or rabbits exposed to 1,000 

mg/kg/day of cyclotriphosphazene (Kinkead et al. 1989c, 1990) or an unspecified amount of Cellulube 220 

(Carpenter et al. 1959). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding cardiovascular effects in humans or 

animals after dermal exposure to polyalphaolefin hydraulic fluids. 
HYDRAULIC FLUIDS 134 

2. HEALTH EFFECTS 

Gastrointestinal Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding gastrointestinal effects in humans or 

animals after dermal exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding gastrointestinal effects in 

humans after dermal exposure to organophosphate ester hydraulic fluids. 

Diarrhea was observed in rabbits administered an unspecified amount of Cellulube 220 for an intermediate 

duration (Carpenter et al. 1959). Soft feces were also observed in Pasturella-infected rabbits receiving 

5,750 mg/kg/day of Fyrquel220, but not 2,875 mg/kg for an intermediate duration (MacEwen and Vemot 

1983). The diarrhea may have been the result of cholinesterase inhibition or of the underlying infection or a 

combination of the two. No gross or histological alterations were observed in rabbits receiving a dermal dose of 

1,000 mg/kg/day of cyclotriphosphazene for an intermediate duration (Kinkead et al. 1989c, 1990). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding gastrointestinal effects in humans or 

animals after dermal exposure to polyalphaolefin hydraulic fluids. 

Hematological Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding hematological effects in humans or 

animals after dermal exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No change in the levels of leukocytes was observed in workers 

dermally exposed to triaryl phosphate hydraulic fluids for an intermediate duration (Baldridge et al. 1959). 

Two intermediate-duration studies examined hematological parameters (e.g., red blood cell levels, 

hemoglobin levels) following dermal exposure to organophosphate ester hydraulic fluid. No hematological 

effects were observed in rabbits exposed to 1,000 mg/kg/day of cyclotriphosphazene (Kinkead et al. 1989c, 

1990) or in rabbits exposed to 5,750 mg/kg/day of Fyrquel 220 (MacEwen and Vemot 1983). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding hematological effects in humans or 

animals after dermal exposure to polyalphaolefin hydraulic fluids. 
HYDRAULIC FLUIDS 135 

2. HEALTH EFFECTS 

Musculoskeletal Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding musculoskeletal effects in humans or 

animals after dermal exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding musculoskeletal effects in 

humans after dermal exposure to organophosphate ester hydraulic fluids. 

No gross or histological alterations in skeletal muscle were observed in rabbits exposed to 1,000 mg/kg/day 

of cyclotriphosphazene (Kinkead et al. 1989c, 1990) or in rabbits exposed to an unspecified amount of 

Cellulube 220 (Carpenter et al. 1959). Both of these studies were intermediate-duration dermal exposure 

studies. Studies examining musculoskeletal end points following acute- or chronic-duration exposure were 

not located. 

Polyalphaolefm Hydraulic Fluids. No studies were located regarding musculoskeletal effects in humans or 

animals after dermal exposure to polyalphaolefin hydraulic fluids. 

Hepatic Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding hepatic effects in humans or animals after 

dermal exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding hepatic effects in humans 

after dermal exposure to organophosphate ester hydraulic fluids. 

In rabbit intermediate-duration studies, no gross or histological alterations in the liver were observed 

following exposure to 1,000 mg/kg/day of cyclotriphosphazene (Kinkead et al. 1989c, 1990) or an 

unspecified amount of Cellulube 220 (Carpenter et al. 1959), and no changes in liver weights Were observed in 

rabbits exposed to 5,750 mg/kg/day of Fyrquel 220 (MacEwen and Vemot 1983). No acute- or chronicduration 

studies examining hepatic end points were located. 

Polyalphaolejin Hydraulic Fluids. No studies were located regarding hepatic effects in humans or animals 

after dermal exposure to polyalphaolefin hydraulic fluids. 
HYDRAULIC FLUIDS 136 

2. HEALTH EFFECTS 

Renal Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding renal effects in humans or animals after 

dermal exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding renal effects in humans after 

dermal exposure to organophosphate ester hydraulic fluids. 

Significant increases in serum urea nitrogen and serum creatinine levels (which may be indicative of impaired 

renal function) were observed in Pasteurella-infected rabbits exposed to 2,875 or 5,750 mg/kg/day of 

Fyrquel220 for an intermediate duration (MacEwen and Vemot 1983). The results of the histological 

examination were not reported, and the renal effects of the infection were not discussed. No gross or 

histological alterations were observed in the kidneys of rabbits exposed to 1,000 mg/kg/day of 

cyclotriphosphazene (Kinkead et al. 1989c, 1990) or in rabbits exposed to an unspecified amount of Cellulube 

220 for an intermediate duration (Carpenter et al. 1959). No studies examining renal effects following acute or 

chronic durations were located. 

Polyalphaolejin Hydraulic Fluids. No studies were located regarding renal effects in humans or animals 

after dermal exposure to polyalphaolefin hydraulic fluids. 

Endocrine Effects. 

No studies were located regarding endocrine effects in humans or animals after dermal exposure to mineral 

oil or polyalphaolefin hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No histopathological evidence of adverse effects on the adrenal 

gland was found in rabbits dermally exposed to 1,000 mg/kg/day cyclotriphosphazene for 6 hours per day, 5 

days per week, for 21 days (Kinkead et al. 1989c, 1990). 

Dermal Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding dermal effects in humans after dermal 

exposure to mineral oil hydraulic fluids. 
HYDRAULIC FLUIDS 137 

2. HEALTH EFFECTS 

Several mineral oil hydraulic fluids have been shown to be skin irritants in rabbits following a single 

exposure. Moderate skin irritation, erythema, and edema were observed following application of a 0.5 mL 

napthenic petroleum-based hydraulic fluid designated as MIL-H-5606 (Kinkead et al. 1985). No signs of 

skin irritation were observed following application of 0.1 mL of Sunsafe F, Houghto-Safe 5047F, 

Quintolubric 95830W, or Pyroguard A-443 (Kinkead et al. 1987a, 1988). 

Organophosphate Ester Hydraulic Fluids. Repeated application of a patch treated with 0.2 μL of Skydrol 

500B-4 for 5 weeks (3 times/week) resulted in mild cumulative erythema confined to the contact site in 14 of 

53 human test subjects, beginning with the third dose during the first week. No evidence of immediate 

primary dermal irritation was observed (Monsanto 1980). 

Mild erythema and skin thickening was observed in rabbits following a single exposure to 0.5 mL of Durad 

550B (FMC 1992a). A number of other animal studies have found no signs of skin irritation following acute 

exposure to Durad 220B (FMC 1990a), Durad 110 (FMC 1990a), Durad 300 (FMC 1990a), Durad MP280 

(Gaworski et al. 1986; Kinkead et al. 1992d), Durad 125 (FMC 1991 b), Fyrquel 220 (Gaworski et al. 1986; 

Kinkead et al. 1992e), and cyclotriphosphazene (Gaworski et al. 1986; Kinkead et al. 1992a, 1992c; 

MacEwen and Vemot 1985). No evidence of skin histological damage was observed in rabbits repeatedly 

exposed to an unspecified amount of Cellulube 220 (Carpenter et al. 1959) or 1,000 mg/kg/day of 

cyclotriphosphazene (Kinkead et al. 1989c, 1990) for an intermediate duration. Skin irritation was not 

observed in rabbits exposed to 5,750 mg/kg/day of Fyrquel220 for an intermediate duration (MacEwen and 

Vemot 1983). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding dermal effects in humans after dermal 

exposure to polyalphaolefin hydraulic fluids. 

A number of studies examined dermal end points in animals exposed to polyalphaolefin hydraulic fluids for 

an acute duration. Mild skin irritation was observed in rabbits following application of 0.5 mL of 

polyalphaolefin hydraulic fluids designated as DTNSRDC No. N50 1 or N5 17 (MacEwen andVemot 1983) 

and in guinea pigs following application of 0.05 mL DTNSRDC No. N501. No signs of dermal irritation 

were observed in rabbits following application of 0.5 mL of polyalphaolefin hydraulic fluids designated as 

DTNSRDC Nos. N448, N518, N525, and N527 (MacEwen and Vemot 1983), MIL-H-83282 (Kinkead et al. 

1985), and MIL-H-83282LT (Kinkead et al. 1992b), and application of 142 mg/cm2

 of a polyalphaolefin 

hydraulic fluid with a Naval designation of B85-174 (Kinkead et al. 1987b). 
HYDRAULIC FLUIDS 138 

2. HEALTH EFFECTS 

Ocular Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding ocular effects in humans after exposure to 

mineral oil hydraulic fluids. 

Mild eye irritation was observed following ocular application of 0.1 mL of Sunsafe F, Houghto-Safe 5047F, 

Quintolubric 95830W, or Pyroguard A-443 (Kinkead et al. 1987a, 1988). A NOAEL of 0.1 mL for eye 

irritation was identified for MIL-H-5606 (Kinkead et al. 1985). No longer term studies examining ocular end 

points were located. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding ocular effects in humans 

after exposure to organophosphate ester hydraulic fluids. 

Eye irritation was not observed in animal studies following a single application of 0.1 mL of Fyrquel 220 

(Gaworski et al. 1986; Kinkead et al. 1992e), Durad MP280 (Gaworski et al. 1986; Kinkead et al. 1992d), or 

cyclotriphosphazene (Kinkead et al. 1992c; MacEwen and Vemot 1985). Intermediate-duration exposure of 

rats, rabbits, or hamsters to aerosols of Fyrquel 220 or Durad MP280 (MacEwen and Vemot 1983), rabbits 

to Cellulube 220 (Carpenter et al. 1959), or rats to cyclotriphosphazene (Kinkead et al. 1989a, 1990) also did not 

cause eye irritation. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding ocular effects in humans after 

exposure to polyalphaolefin hydraulic fluids. 

During a single 4-hour exposure to 1,120 mg/m3

 MIL-H-83282LT hydraulic fluid, rats showed signs of 

mucosal irritation including rubbing of the eyes and nose and squinting of eyes (Kinkead et al. 1992b). 

Exposure in this case was a whole-body exposure in an inhalation chamber and aerosols of the hydraulic fluid 

came into direct contact with the eyes. No other studies reported ocular effects following exposure to 

polyalphaolefin hydraulic fluid aerosols. 

Eye irritation was observed in rabbits following ocular application of MIL-H-83282LT (Kinkead et al. 

1992b). No signs of irritation were observed in rabbits following ocular application of 0.1 mL of 

polyalphaolefin hydraulic fluids designated as DTNSRDC Nos. N448, N501, N5 17, N5 18, N525, and N527 

(MacEwen and Vemot 1983), MIL-H-83282 (Kinkead et al. 1985), or B85-174 (Kinkead et al. 1987b). 
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2. HEALTH EFFECTS 

Body Weight Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding body weight effects in humans after 

dermal exposure to mineral oil hydraulic fluids. 

In acute toxicity studies, no significant changes in body weight were observed following dermal application of 

2,000 mg/kg of Sunsafe F, Quintolubric 95830W, Houghto-Safe 5047F, Pyroguard A-443 (Kinkead et al. 

1989b, 1988), or 1,800 mg/kg of a mineral oil hydraulic fluid meeting military specifications of MIL-H-5606 

(Kinkead et al. 1985). No longer-term studies were located. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding body weight effects in 

humans after dermal exposure to organophosphate ester hydraulic fluids. 

Following acute exposure, no changes in body weight gain were observed in rats exposed to 2,000 mg/kg of 

Durad 110, Durad 220B, or Durad 300 (FMC 1990a) or in rabbits exposed to 2,890 mg/kg of 

cyclotriphosphazene (Kinkead et al. 1992c; MacEwen and Vemot 1985). A transient weight loss was observed 

in rabbits exposed to 2 mL/kg of MIL-H-19457B or Fyrquel 220 (Gaworski et al. 1986; Kinkead et al. 1992a). 

Intermediate-duration exposure of rabbits to 1,000 mg/kg/day of cyclotriphosphazene (Kinkead et al. 1989c, 

1990) or 5,750 mg/kg/day of Fyrquel 220 (MacEwen and Vemot 1983) did not alter body weight gains. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding body weight effects in humans after 

dermal exposure to polyalphaolefin hydraulic fluids. 

No changes in growth were observed in rabbits following single applications of 1,700 mg/kg of 

polyalphaolefin hydraulic fluids designated as DTNSRDC N448, N501, N5 17, N5 18, N525, or N527 

(MacEwen and Vemot 1983), 1,700 mg/kg of polyalphaolefin hydraulic fluids meeting military specifications 

of MIL-H-83282 (Kinkead et al. 1985) or 2,000 mg/kg of MIL-H-83282LT or B85-174 (Kinkead et al. 

1992b). No longer-term studies were located. 
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2.2.3.3 Immunological and Lymphoreticular Effects 

The highest NOAEL values and all LOAEL values for each reliable study for immunological effects in each 

species and duration category are recorded in Tables 2-7, 2-8, and 2-9 for mineral oil hydraulic fluids, 

organophosphate ester hydraulic fluids, and polyalphaolefin hydraulic fluids, respectively. 

Mineral Oil Hydraulic Fluids. No studies were located regarding immunological effects in humans after 

dermal exposure to mineral oil hydraulic fluids. 

In guinea pig assays for skin sensitization, 4 of 5 tested mineral oil hydraulic fluids (Pyroguard A-443, 

Sunsafe F, Houghto-Safe 5047F, and MIL-H-5606) displayed no activity; the remaining fluid, Quintolubric 

95830W, displayed only weak skin sensitization (skin sensitization occurred in only 1 of 10 guinea pigs) 

(Kinkead et al. 1985, 1987a, 1988). No other studies were located regarding immunological effects in 

animals after dermal exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No dermal sensitization was observed in a study of 

human subjects (46 females and 7 males) exposed dermally to 0.2 mL Skydrol 500B-4 for three 24-hour 

periods per week for 5 weeks (Monsanto 1980). No other studies were located regarding immunological 

effects in humans after dermal exposure to organophosphate ester hydraulic fluids. Two case reports of skin 

sensitization to triphenyl phosphate were found. A woman developed eczema from her eyeglasses containing the 

phosphate (Carlsen et al. 1986), and a carpenter tested positive to an allergy patch test, where a 5% petrolatum 

solution of triphenyl phosphate was applied after exposure to a glue containing it (Camarassa and Serra-Baldfich 

1992). 

No skin sensitization was seen in guinea pigs treated with four doses of 0.1 mL of a cyclotriphosphazenebased 

hydraulic fluid on the skin of the forelegs (Kinkead et al. 1992c; MacEwen and Vernot 1985). Thymus weight 

decreases (both absolute and relative to body weight) were observed, without histological alterations, in rabbits 

dermally exposed to 6-hour doses of cyclotriphosphazene ≤1,000 mg/kg, 5 days/week for 21 days (Kinkead et 

al. 1989c, 1990). No other studies regarding immunological effects in animals after dermal exposure were 

located. 
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Polyalphaolefin Hydraulic Fluids. No studies were located regarding immunological effects in 

humans after dermal exposure to polyalphaolefin hydraulic fluids. 

Two U.S. military polyalphaolefin hydraulic fluids, MJL-H83232LT and B85-174, displayed skin 

sensitization activity in guinea pigs (Kinkead et al. 1987b, 1992b). Seven other polyalphaolefin hydraulic 

fluids did not produce skin sensitization in guinea pig assays; tested materials were designated as 

MIL-H-83282 (Kinkead et al. 1985) and DTNSDR Nos. N448, N501, N517, N518, N525, and N527 

(MacEwen and Vernot 1983). No other studies were located regarding immunological effects in animals after 

dermal exposure to polyalphaolefin hydraulic fluids. 

2.2.3.4 Neurological Effects 

The highest NOAEL values and all LOAEL values for each reliable study for neurological effects in each 

species and duration category are recorded in Tables 2-7,2-8, and 2-9 for mineral oil hydraulic fluids, 

organophosphate ester hydraulic fluids, and polyalphaolefin hydraulic fluids, respectively. 

Mineral Oil Hydraulic Fluids. Weakness in the hands and the absence of tendon reflexes developed in a 

man whose skin was exposed heavily to mineral-oil-based hydraulic fluids on a daily occupational basis for 

≈2 years. Reportedly, his hands and arms “were always wet with fluid,” and his clothes were often saturated 

with fluid (Järvholm et al. 1986). The fluid, to which the man was exposed for an unspecified number of 

months prior to the appearance of neurotoxic signs, contained ≈0.5% isopropylated triphenyl phosphate and 

<50 ppm tri-ortho-cresyl phosphate (TOCP) according to the manufacturer’s analysis. A coincidental 

association between polyneuropathy and exposure to hydraulic fluid in this case could not be excluded. 

Neurological examination of eight men who worked with mineral-oil-based hydraulic fluids for 3 months to 

13 years revealed subtle electromyographical effects in several muscles of four of the men (“a reduced 

number of motor unit potentials”), but no such effects were observed in eight nonexposed male controls 

(Järvholm et al. 1986). Reportedly, the exposed men in this study were less heavily exposed to hydraulic 

fluids than the man who developed arm weakness and absence of tendon reflexes. The two reports provide 

limited evidence that dermal exposure to certain mineral-oil-based hydraulic fluids may produce neurological 

effects. Other studies on neurological effects in humans following dermal exposure to mineral-oil-based 

hydraulic fluids were not located. 
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In acute toxicity studies, rabbits exposed to 2,000 mg/kg occluded dermal doses of one of several mineral oil 

hydraulic fluids (Sunsafe F, Houghto-Safe 5047F, Quintolubric 95830W, Pyroguard A-443 and 

MIL-H-5606) for 24 hours displayed no signs of neurological toxicity within 14 days postdosing (Kinkead et 

al. 1985, 1987a, 1988). Other information on neurological effects in animals following dermal exposure to 

mineral oil hydraulic fluids was not located. 

Organophosphate Ester Hydraulic Fluids. A brief overview of organophosphate ester neurotoxicity 

is presented in Section 2.2.1.4. 

During a cleaning operation, 14 men on a U.S. Navy ship were dermally exposed on their hands and arms, 

and on the clothing to a hydraulic fluid described as a mixture of triphenyl phosphates (Baldridge et al. 1959). 

The men were directed to bathe and change clothing 24 hours after the operation. Blood samples were drawn for 

plasma and red blood cell cholinesterase measurement presumably 24 hours after the cleanup event and after an 

interval of 2 weeks. No significant differences in cholinesterase values were observed between theexposed men 

and a group of nonexposed men. The men were instructed to report the occurrence of any neuropathic symptoms 

to the medical department of the ship, but none were reported. 

Another group of 14 men was exposed primarily by dermal contact to a triaryl phosphate hydraulic fluid 

during installation and operation of hydraulic aircraft elevators on a U.S. Navy ship (Baldridge et al. 1959). 

Neurological examinations, physical examinations, white blood cell counts, and blood cholinesterase 

measurements made several times during a 3- to 4-month operation period failed to detect differences 

between the exposed men and a group of eight nonexposed men from the same ship. 

No other information was located regarding neurological effects in humans after dermal exposure to hydraulic 

fluids. 

Several organophosphate ester hydraulic fluids produced no clinical signs of neurotoxicity in rats and rabbits 

during 14-day observation periods after 24-hour periods of occluded dermal exposure. Tested hydraulic 

fluids included Durad 110 (FMC 1990a), Durad 300 (FMC 1990a), and a cyclotriphosphazene-based 

hydraulic fluid (Kinkead et al. 1992c; MacEwen and Vemot 1985). These species are not susceptible to 

organophosphate-induced delayed neuropathy (Abou-Donia and Lapadula 1990). 
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Delayed neuropathy occurred in a group of 50 cattle after the waste from reclamation of contaminated 

hydraulic fluid was poured over their backs as a treatment for ringworms (Julian et al. 1976). The animals 

were observed licking their backs and the backs of others, suggesting that oral as well as dermal exposure 

occurred. The composition of the waste product was unknown, but the hydraulic fluid was identified as a 

Fyrquel that may have been contaminated with tri-ortho-cresyl phosphate (TOCP). The first signs of 

posterior weakness (knuckling at the fetlocks and mild ataxia) were noted 20 days after treatment. Decreased 

sensory and motor responses in the hind limbs were observed, and histopathological examination of seven cows 

revealed demyelination and degeneration in the spinal cord and the sciatic nerve. 

Severe cholinergic signs (diarrhea, generalized weakness, dyspnea, and decreased blood cholinesterase 

activity) and subsequent death occurred in two rabbits given daily 4-hour occluded dermal exposures to 

Cellulube 220 that contained a mixture of tricresyl and trixylenyl phosphate esters (Carpenter et al. 1959). 

One rabbit died after 6 days of exposure and the other died after 42 days of exposure. Daily exposures of 

1 or 2 hours also produced cholinergic signs in groups of two rabbits exposed for <44 days. One of the two 

rabbits exposed daily for 2 hours developed hind limb weakness with an altered gait. Histological 

examination of brain, spinal cord, and sciatic nerve tissues in exposed rabbits revealed no “remarkable” 

alterations. Although this study indicates that neurological effects occurred in rabbits with repeated dermal 

exposure to Cellulube 220, no dosage levels were reported. Neither clinical nor histopathological signs of 

neurotoxicity were observed in hens treated dermally with two doses of 5,000 mg/kg tributoxyethyl 

phosphate 21 days apart (Carrington et al. 1989) 

A cyclotriphosphazene-based hydraulic fluid produced no deaths, signs of neurotoxicity or histological 

alterations in the brain or sciatic nerve in rabbits after occluded dermal exposure at 1,000 mg/kg/day, 

6 hours/day (≈10% of body surface area), 5 days/week for 21 days (Kinkead et al. 1989c, 1990). 

No other information was located regarding neurological effects in animals after intermediate to chronic 

dermal exposure to organophosphate ester hydraulic fluids. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding neurological effects in humans 

after dermal exposure to polyalphaolefin hydraulic fluids. 

Information regarding neurological effects in animals after dermal exposure to polyalphaolefin hydraulic 

fluids is restricted to a report that lethargy was observed in some rabbits during 24-hour periods of exposure 
HYDRAULIC FLUIDS 144 

2. HEALTH EFFECTS
 

to occluded topically applied (1,700 mg/kg) of polyalphaolefin hydraulic fluids designated as DTNSRDC 

Nos. N448, N501, N517, N518, N525, and N527 (MacEwen and Vemot 1983). 

2.2.3.5 Reproductive Effects 

No studies were located regarding reproductive effects in humans or animals after dermal exposure to mineral 

oil hydraulic fluids or to polyalphaolefin hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding reproductive effects in 

humans after dermal exposure to organophosphate ester hydraulic fluids. 

Dermal exposure of male rabbits to unspecified doses of Cellulube 220 (14 hours/day, 4-5 days/week for 

≤46 days) did not elicit histological alterations in the testes (Carpenter et al. 1959). Dermal exposure of male 

and female rabbits to cyclotriphosphazene at doses ≤1,000 mg/kg/day for 6 hours/day, 5 days/week, for 

21 days did not affect the reproductive organs (Kinkead et al. 1989c, 1990). No other dermal studies 

examining reproductive effects in animals were located. This NOAEL value for reproductive effects in 

rabbits acutely exposed to cyclotriphosphazene hydraulic fluid is recorded in Table 2-8. 

2.2.3.6 Developmental Effects 

No studies were located regarding developmental effects in humans or animals after dermal exposure to 

mineral oil hydraulic fluids or to polyalphaolefin hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding developmental effects 

in humans after derrnal exposure to organophosphate ester hydraulic fluids. 

After a single dermal exposure to waste from the reclamation of a Fyrquel hydraulic fluid that may have been 

contaminated with tri-ortho-cresyl phosphate (TOCP), no apparent signs of neurotoxicity wereobserved in 

calves of 10 cows that manifested neurotoxicity just after the birth of the calves. The cows were apparently also 

exposed orally concurrent to the dermal exposure (Julian et al. 1976). No intermediate- or chronic-duration 

dermal studies examining developmental effects in animals were located. 
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2. HEALTH EFFECTS 

2.2.3.7 Genotoxic Effects 

Mineral Oil Hydraulic Fluids. No studies were located regarding genotoxic effects in humans or 

animals after dermal exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding genotoxic effects in 

humans or animals after dermal exposure to organophosphate ester hydraulic fluids. Genotoxicity studies for 

organophosphate ester hydraulic fluids are discussed in Section 2.5. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding genotoxic effects in humans or 

animals after dermal exposure to polyalphaolefin hydraulic fluids. 

2.2.3.8 Cancer 

Mineral Oil Hydraulic Fluids. A significant elevated odds ratio was found between stomach cancer and 

occupational exposure to hydraulic fluids in a case-control study examining associations between subjectively 

reported occupational exposure to petroleum-derived liquids and cancer in particular organs (Siemiatycki et al. 

1987a). The reference group consisted of 2,514 cancer patients who did not have stomach cancer. The main 

group of patients (n=155) exposed to hydraulic fluids consisted of automotive mechanics exposed to 

transmission and brake fluids. While inhalation exposure was possible, dermal contact was the expected 

predominant exposure route. Although the association between exposure to hydraulic fluids and stomach cancer 

was statistically significant, the biological relevance is uncertain due to several limitations of the study including 

sample size, possible misclassification errors in subjective exposure assessment, and confounding exposure to 

other compounds. The importance of exposure to other chemicals as a limitation was emphasized by the 

authors’ report that the association between stomach cancer and exposure to hydraulic fluids was no longer 

significant when adjustments were made for exposure to gasoline. No other information on cancer in humans 

exposed dermally to mineral oil hydraulic fluids was located. 

No studies were located regarding cancer in animals after dermal exposure to mineral oil hydraulic fluids. 
HYDRAULIC FLUIDS 146 

2. HEALTH EFFECTS
 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding cancer in humans or 

animals after dermal exposure to organophosphate ester hydraulic fluids. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding cancer in humans or animals 

after dermal exposure to polyalphaolefin hydraulic fluids. 

2.3 TOXICOKINETICS 

No studies were located that examined the toxicokinetics of mineral oil, organophosphate ester, or 

polyalphaolefin hydraulic fluids in humans or animals, with the exception of a study examining absorption in 

rats after exposure to a hydraulic fluid containing 99.9% cyclotriphosphazene (Kinkead and Bashe 1987) and the 

absorption and metabolism of Reolube HYD46, another organophosphate hydraulic fluid (Ciba-Geigy 1985). 

This section, therefore, discusses available information on the toxicokinetics of major components of these 

classes of hydraulic fluids or of materials that may be expected to display similar toxicokinetic properties based 

on similar physical and chemical characteristics. It should be emphasized that many hydraulic fluids are 

complex mixtures of chemicals that may include some chemicals which may not share toxicokinetic properties 

with the major components. 

Hydrocarbons in mineral oil hydraulic fluids may be expected to be poorly absorbed, regardless of the route 

of exposure, based on results from studies with animals exposed to food-grade or medicinal mineral oil 

(Bollinger 1970; Ebert et al. 1966) or motor oil (Lushbaugh et al. 1950). Absorbed hydrocarbons from 

mineral oil are likely to be preferentially distributed to the liver and fatty tissues, slowly metabolized to 

various types of lipids (e.g., fatty acids or triglycerides), and excreted in the feces via the bile (Bollinger 

1970; Ebert et al. 1966). Accumulation of oil in the lungs (and the consequent development of lipoid 

pneumonia), has been observed in humans and animals after inhalation or oral exposure to mineral oils 

(Cannon 1940; Lushbaugh 1950; Perrot and Palmer 1992). 

No studies were located that examined the toxicokinetics of polyalphaolefins in humans or animals, but the 

similarities in physical and chemical properties between polyalphaolefins and hydrocarbons in mineral oil 

indicate that the toxicokinetics of polyalphaolefins may be similar to those of hydrocarbons in mineral oil 

hydraulic fluids. 
HYDRAULIC FLUIDS 147 

2. HEALTH EFFECTS
 

Animal studies with organophosphate esters, including tricresyl phosphate isomers (Abou-Donia et al. 1990a, 

1990b; Casida et al. 1961; Eto et al. 1962; Kurebayashi et al. 1985; NTP 1988; Suwita and Abou-Donia 1990), 

isopropylated phenyl phosphates (Yang et al. 1990), and tributyl phosphate (Gatz 1992a, 1992b; Suzuki et al. 

1984a) indicate that these compounds are readily absorbed by the gastrointestinal tract and may be absorbed by 

the skin (Ciba-Geigy 1985; Hodge and Sterner 1943; Nomeir and Abou-Donia 1986). Studies examining the 

toxicokinetics of inhaled aerosols of organophosphate esters were not located. Absorbed tricresyl phosphate 

isomers are widely distributed among animal tissues, and display a preferential distribution to fatty tissues, liver, 

and kidneys. They are readily cleared without displaying a tendency to accumulate (Abou-Donia et al. 1990a, 

1990b; Hodge and Sterner 1943; Kurebayashi et al. 1985; Nomeir and Abou-Donia 1986; Somkuti and AbouDonia 1990). 

Animal studies with several organophosphate esters show that these compounds and their metabolites are 

excreted in the urine, bile, and feces. The relative importance of urinary versus fecal excretion appears to 

depend on the organophosphate ester and the dosage (NTP 1988; Somkuti and Abou-Donia 1990; Suzuki et al. 

1984a). Species differences in sensitivity to experimental tri-ortho-cresyl phosphate-induced delayed 

neuropathy have been associated in part with apparently subtle differences among species in elimination 

kinetics (Abou-Donia 1990a, 1990b; Suwita and Abou-Donia 1990). (TOCP is not a hydraulic fluid, but a 

contaminant in older formulations of TCP-based hydraulic fluids.) 

Metabolism of the triaryl and trialkyl organophosphate esters used in hydraulic fluids involves a very 

complex array of Phase I reactions including cytochrome P-450-mediated oxidations, dearylations, and cyclic 

rearrangements. For example, 19 metabolites were identified in rats after exposure to [14C] labeled tributyl 

phosphate (Gatz 1992a). Phase II reactions include glutathione and glucuronic acid conjugations, as 

indicated by animal studies with several organophosphate esters including isopropylated phenyl phosphates 

(Yang et al. 1990), tri-ortho-cresyl phosphate (TOCP) (Abou-Donia 1990a, 1990b; Casida et al. 1961; Eto 

et al. 1962, 1967; Nomeir and Abou-Donia 1986; Somkuti and Abou-Donia 1990), tri-para-cresyl phosphate 

(Kurebayashi et al. 1985), and tributyl phosphate (Gatz 1992a, 1994; Suzuki et al. 1984a). The preferential 

distribution of radioactivity in the liver after administration of radiolabeled tricresyl phosphateisomers 

emphasizes the importance of the liver in metabolism of these compounds, but metabolism in other tissues is 

possible. 
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2. HEALTH EFFECTS 

2.3.1 Absorption 

2.3.1.1 Inhalation Exposure 

Mineral Oil Hydraulic Fluids. No studies were located regarding absorption in humans or animals after 

inhalation exposure to mineral oil hydraulic fluids. 

Indirect evidence suggests that pulmonary absorption of hydrocarbons in mineral oil hydraulic fluids may 

occur. Mice, rats, and rabbits exposed to fogs (particle size ranged from 0.34 to 1.45 μm) of 63 mg/L of a 

diesel-engine lubricating oil for ≤343 days displayed (as indicated by histological analysis) oil in alveolar 

macrophages, mediastinal lymph nodes, lymphatic channels of the lungs, and in the pleura (Lushbaugh et al. 

1950). A chemical analysis of lung and liver tissue found oil at respective concentrations of 0.13% and 

0.03% (w/w) in exposed mice, but no oil in the same tissues from controls. These results are consistent with 

the hypothesis that mineral oil aerosols are not quickly absorbed by alveolar pneumocytes, and macrophages 

subsequently mediate clearance. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding absorption in humans 

after inhalation exposure to organophosphate ester hydraulic fluids. 

No data were located regarding absorption in animals after inhalation exposure to organophosphate ester 

hydraulic fluids or specific organophosphate esters, except for the observation that parent material was not 

detected by gas chromatography in the blood or urine of male rats exposed to 5,120 mg/m3

 of an aerosol of a 

cyclotriphosphazene (99.9%) hydraulic fluid for 4 hours, thereby suggesting that the extent of absorption was 

limited (Kinkead and Bashe 1987). Blood samples were collected at 0,24, and 48 hours after exposure was 

terminated. Urine was collected for 24 hours after exposure. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding absorption in humans or animals 

after inhalation exposure to polyalphaolefin hydraulic fluids or their major components. Based on 

physicochemical similarities with mineral oils (i.e., long-chain aliphatic hydrocarbons are predominant 

components), inhaled aerosols of polyalphaolefin hydraulic fluids may enter the body by macrophagemediated 

clearance (see discussion above for mineral oil hydraulic fluids). 
HYDRAULIC FLUIDS 149 

2. HEALTH EFFECTS 

2.3.1.2 Oral Exposure 

Mineral Oil Hydraulic Fluids. No studies were located regarding absorption in humans or animals after 

oral exposure to mineral oil hydraulic fluids. 

Food-grade or medicinal mineral oil, a mixture of aliphatic hydrocarbons that also may be found in mineral 

oil hydraulic fluids, is known to be absorbed only to a limited extent by the human gastrointestinal tract and 

has a laxative effect (Anonymous 1967; Brunton 1985), thus suggesting that mineral oil hydraulic fluids may 

behave likewise. 

Experiments with rats given oral doses of tritiated food-grade mineral oil provide supporting evidence that 

the absorption of hydrocarbons in mineral oils is limited. Five hours after dosing with 0.66 mL/kg of tritiated 

mineral oil (“liquid petrolatum U.S.P.“), ≈75% of the administered radioactivity remained in the alimentary 

tract, and only 3% of the administered radioactivity was accounted for by radioactivity in other parts of the 

rat carcass (Ebert et al. 1966). About 80% of the administered radioactivity was recovered in feces during 

the first 2 days after treatment, and over 90% of the radioactivity in the feces was in the form of mineral oil. 

These data are consistent with the hypothesis that ingested mineral oil was poorly absorbed. Neither biliary 

excretion nor enterohepatic circulation of mineral oils was measured in this study, and thus, any quantitative 

estimates of the extent of absorption based on these data should be viewed as tentative. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding absorption in humans 

or animals after oral exposure to organophosphate ester hydraulic fluids. 

Studies of excretion in animals following oral administration of TOCP and tri-para-cresyl phosphate suggest 

that organophosphate esters found in hydraulic fluids may be extensively absorbed by the gastrointestinal 

tract (Abou-Donia et al. 1990a, 1990b; Kurebayashi et al. 1985; Suwita and Abou-Donia 1990). 

One day after oral administration of single 7.8-mg/kg doses of [methyl-14C]tri-para-cresyl phosphate (in 

DMSO) to male rats, radioactivity in urine, feces, expired air (as CO2), and bile represented approximately 

34%, 42%, 14%, and 28% of the administered dose, respectively (Kurebayashi et al. 1985). Measurements 

for expired air and excreted bile were carried out on five rats with cannulated bile ducts; fecal and urinary 

excretion were measured in another group of three rats without cannulated bile ducts. Assuming that 

radioactivity in urine, expired air, and bile represent absorbed compound, these results suggest that at least 
HYDRAULIC FLUIDS 150 

2. HEALTH EFFECTS
 

76% of the tri-para-cresyl phosphate dose was absorbed. In rats given larger single doses of 

[

14C]tri-para-cresyl phosphate (89.6 mg/kg), radioactivity in urine, feces, and expired air accounted for 

approximately 8%, 65%, and 3% of the dose, respectively, 1 day after dosing, and for 12%, 77%, and 6% of 

the dose, respectively, after 7 days. Enterohepatic circulation was not examined in the high-dose rats, but 

GC-MS analysis of the feces indicated that most of the radioactivity in the feces from the high-dose rats was 

unchanged tri-para-cresyl phosphate. This observation is consistent with the hypothesis that a significant 

portion of the high dose was not absorbed. 

Male rats given single gavage doses of 50 mg/kg [uniformly labeled 14C-phenyl]tri-ortho-cresyl phosphate in 

corn oil excreted approximately 50% and 25% of administered radioactivity in urine and feces, respectively, 

24 hours after dosing (Abou-Donia et al. 1990a). Five days after dosing, cumulative radioactivity in urine 

and feces accounted for approximately 60% and 35%, respectively. Although biliary excretion and 

enterohepatic circulation were not examined in this study, the appearance of a large proportion of the 

administered radioactivity in the urine is indicative of extensive gastrointestinal absorption. Peak 

concentrations of radioactivity were observed between 2 and 48 hours after dosing (most tissues attained 

peak levels at 6 hours) in a number of nongastrointestinal tissues (Abou-Donia et al. 1990a); this implies that the 

TOCP was absorbed in less than 6 hours. The extent of absorption could not be estimated in companion 

excretion studies with chickens given single gavage doses of 50 mg/kg [uniformly labeled 14C-phenyl]TOCP in 

corn oil, because chickens void urine and feces together and the authors did not attempt to separate them (AbouDonia et al. 1990b; Suwita and Abou-Donia 1990). However, the hen studies provided qualitative evidence that 

TOCP was readily absorbed since radioactivity was detected within 12 hours of dosing in nongastrointestinal 

tissues including plasma, liver, kidney, and gall bladder. 

Results from animal studies with other organophosphate esters also indicate ready gastrointestinal 

absorption. Rats given single oral doses of 14 mg/kg [1 -butyl-14C]tributyl phosphate excreted approximately 

50%, 10%, and 6% of applied radioactivity in urine, expired CO2 and feces, respectively (Suzuki et al. 

1984a). Metabolites of isopropylated phenyl phosphates were detected in the bile of rabbits within 

6-24 hours of gavage administration of 2 g/kg Reolube HYD46, a hydraulic fluid containing isopropylated 

phenyl phosphates (Yang et al. 1990). Evidence for extensive absorption of tributyl phosphate was shown by the 

recovery of 66 to 80% of the radioactivity from [14C]tributyl phosphate in urine for single oral doses up to 350 

mg/kg in rats (Gatz 1992a, 1992b, 1994). 
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2. HEALTH EFFECTS
 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding absorption in humans or animals 

after oral exposure to polyalphaolefin hydraulic fluids. 

As mentioned previously, ingested food-grade mineral oil is absorbed only to a limited extent in humans and 

animals (Brunton 1985; Ebert et al. 1966). The physicochemical similarities between polyalphaolefins and 

mineral oils suggest that the extent of gastrointestinal absorption of polyalphaolefin hydraulic fluids also may 

be limited. 

2.3.1.3 Dermal Exposure 

Mineral Oil Hydraulic Fluids. No studies were located regarding absorption in humans or animals after 

dermal exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. Limited studies indicate that organophosphate esters 

found in hydraulic fluids are absorbed by human skin. Radioactivity was detected in the blood and urine of 

two human subjects 1 hour after dermal exposure of both palms to 0.11 or 0.22 g of tri-ortho-cresyl 

phosphate labeled with radioactive phosphorus (Hodge and Sterner 1943). In vitro studies with human 

cadaver abdominal skin separating neat hydraulic fluids from an ethanol/water solution (70:30) found mean 

steady-state absorption rates of 0.9 and 0.54 μg/cm2

/hour for triphenyl phosphate (TPP) and 

2-isopropylphenyl diphenyl phosphate (2-IDPP), respectively, from the hydraulic fluid additive Reofos 50 

(Ciba-Geigy 1985). The Reofos 50 sample reportedly contained 261.5 mg/mL TPP and 341.43 mg/mL 

2-IDPP. Using the hydraulic fluid, Reolube HYD46 (which contained 30.5 mg/mL TPP and 218.1 mg/mL 

2-IDPP), steady-state absorption rates of 0.67 and 3.32 μg/cm2kour were measured for TPP and 2-IDPP, 

respectively. The applicability of these in vitro absorption rates to in vivo exposures is uncertain due to 

several limitations of the study, including the use of skin from only one individual, the use of 70% ethanol in 

the receptor chamber, and the absence of reference standards in the study. 

Single dermal doses of 50 mg/kg tri-ortho-cresyl-[uniformly labeled 14C-phenyl]phosphate (TOCP) were 

applied to preclipped, unprotected, 10-cm2

 areas of skin in male cats (Nomeir and Abou-Donia 1986). Three 

treated cats were sacrificed 0.5, 1,2,5, and 10 days after treatment. Radioactivity in urine and feces collected 

over the 10-day period accounted for 28% and 19% of the applied dose, respectively, but no radioactivity was 

detected in expired air. Radioactivity in analyzed tissues reached maximal levels at 24 hours (accounting for 

8.7% of the applied dose). These data are inadequate for quantitative measurements of the extent of dermal 
HYDRAULIC FLUIDS 152 

2. HEALTH EFFECTS
 

absorption of TOCP, because a significant fraction of the applied radioactivity was not accounted for in the 

analysis, and some of the TOCP may have been ingested by the cats during grooming. 

Radioactivity was detected in the blood and urine of a single female dog, 1 hour after dermal application of a 

2.094-g dose of TOCP labeled with radioactive phosphorus to a 300-cm2

 area of clipped and depilated 

abdominal skin (Hodge and Sterner 1943). Gas chromatographic analysis of blood detected no parent 

material in male rats at 4,24, or 48 hours after a 24-hour, occluded exposure to a hydraulic fluid containing 

99.9% cyclotriphosphazene, but the presence of metabolites in the blood was not investigated (Kinkead and 

Bashe 1987). 

In Yucatan minipigs dermally exposed for 6 hours to 350 mg/kg, [14C]tributyl phosphate was only poorly 

absorbed (less than 5% of the applied dose). Absorption in rats treated under similar conditions was much 

higher (54-58%) (Gatz 1992a, 1992b). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding absorption in humans or animals 

after dermal exposure to polyalphaolefin hydraulic fluids. 

2.3.1.4 Other Routes of Exposure 

Mineral Oil Hydraulic Fluids. Absorption of a mineral oil in an emulsion was apparently very slow in 

female rats injected subcutaneously with 0.1 mL and in squirrel monkeys injected intramuscularly with 

0.3 mL (Bollinger 1970). The emulsion contained 1 volume mannide monoleate, 9 volumes mineral oil, and 

9 volumes water; [14C] labeled hexadecane, a major component of the mineral oil, was added to the emulsion as 

a radiotracer. At 1 week and 10 months after treatment, radioactivity remaining at the sites of injection 

accounted for 85-99% and 25-33%, respectively, of the administered radioactivity. 

Organophosphate Ester Hydraulic Fluids. Absorption rates of TOCP were measured in chickens 

after subcutaneous injection by measuring the apparent disappearance of TOCP from the site of injection 

with 31P NMR spectroscopy (Carrington et al. 1988). Five chickens were injected with single, 1 ,187-mg/kg, 

neurotoxic doses in the back of the neck. Diminishment of the 31P-TOCP signal at the site of injection 

showed a biphasic pattern; calculated half-lives for the first and second phases were 3.22 hours and 

15.3 days. The authors interpreted the first phase to be indicative of spreading of the material under the skin 
HYDRAULIC FLUIDS 153 

2. HEALTH EFFECTS
 

and the second phase to be indicative of absorption. They concluded that absorption of the subcutaneously 

injected material was slow. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding absorption of polyalphaolefin 

hydraulic fluids in humans or animals after exposure by routes other than inhalation, oral, or dermal. 

2.3.2 Distribution 

2.3.2.1 Inhalation Exposure 

Mineral Oil Hydraulic Fluids. No studies were located regarding distribution in humans or animals 

after inhalation exposure to mineral oil hydraulic fluids. 

Numerous case reports of lipoid pneumonia in humans exposed through intranasal application of liquid 

petrolatum in medicinal nose drops (Cannon 1940; Lushbaugh et al. 1950) suggest that accumulation of oil in 

the lungs may be a concern with prolonged or high-level exposure to aerosols of mineral oils in hydraulic 

fluids. An examination of mice exposed to fogs of a lubricating oil for ≤343 days chemically detected oil in 

lung (0.13% [w/w]) and liver (0.03% [w/w]) tissue and histologically detected oil in alveolar macrophages, 

mediastinal lymph nodes, and lymphatic channels of the lung (Lushbaugh 1950). Further information 

regarding the distribution of inhaled mineral oil was not located. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding distribution in humans 

or animals after inhalation exposure to organophosphate hydraulic fluids. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding distribution in humans or 

animals after inhalation exposure to polyalphaolefin hydraulic fluids. 

Oil accumulationin the lungs after long-term or high-level exposure to aerosols of polyalphaolefin may be a 

concern, based on observations of lipoid pneumonia in humans after prolonged intranasal application of 

mineral oil mists (Lushbaugh 1950) and the physical and chemical similarities between mineral oil and 

polyalphaolefins (i.e., both are composed predominately of aliphatic hydrocarbons). 
HYDRAULIC FLUIDS 154 

2. HEALTH EFFECTS 

2.3.2.2 Oral Exposure 

Mineral Oil Hydraulic Fluids. No studies were located regarding distribution in humans or animals 

after oral exposure to mineral oil hydraulic fluids. 

Limited evidence suggests that oil accumulation in the lungs may occur due to aspiration of ingested mineral 

oil hydraulic fluids. Although the danger of aspiring mineral oil into the lungs is not as great as other 

petroleum-based hydrocarbon mixtures with higher volatility and lower viscosity such as kerosene (Gerarde 

1963; Klein and Simon 1986), oil accumulation in the lungs and lipoid pneumonia were observed in a child 

who ingested approximately 5-10 mL of a mineral oil automobile transmission fluid (Perrot and Palmer 

1992). 

Mineral oil may accumulate to some degree in liver and fatty tissues after absorption of ingested mineral oil 

hydraulic fluids, as indicated by experiments with rats given single, 0.66-mL oral doses of tritiated mineral 

oil (Ebert et al. 1966). Twenty-four hours after administration, the concentrations of tritiated mineral oil in 

liver and fat were approximately seven-fold greater than those in kidney and brain; other tissues were not 

examined. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding distribution in humans 

or animals after oral exposure to organophosphate ester hydraulic fluids. 

A triaryl phosphate ester, tributoxyethyl phosphate, was detected at a mean concentration of 11.3 ng/g in 41 

of 115 human adipose tissue samples taken from cadavers from Kingston and Ottawa, Canada (LeBel and 

Williams 1986). Because triaryl phosphate esters have been found in Canadian drinking water and fish, the 

presumed route of exposure of these individuals was oral. This study provides limited evidence that 

organophosphate esters found in hydraulic fluids may accumulate in human fatty tissue. 

Studies with rats and chickens given oral doses of TOCP and tri-para-cresyl phosphate provide more 

definitive evidence that, following absorption, organophosphate esters in hydraulic fluids (or their 

metabolites) may be widely distributed among tissues with a preferential distribution to fatty tissues, the 

liver, and the kidneys (Abou-Donia et al. 1990a, 1990b; Kurebayashi et al. 1985; Somkuti and Abou-Donia 

1990; Suwita and Abou-Donia 1990). 
HYDRAULIC FLUIDS 155 

2. HEALTH EFFECTS
 

Less than 1% of total radioactivity was found in tissues 6-48 hours after oral administration of [14C]tributyl 

phosphate. The majority of label was found in urine (70%) and feces (18%) after both single and multiple 

doses of 10 and 350 mg/kg/day (Gatz 1992b). Approximately 5% of the label was recovered as CO2 in 

expired air. 

Twenty-four hours following oral administration of 89.6 mg/kg of [methyl14C]tri-para-cresyl phosphate to 

male rats, radioactivity was detected in all tissues examined (Kurebayashi et al. 1985). Aside from the 

stomach and intestines, the highest concentrations (in units of ug-equivalents per gram of tissue) were found in 

fatty tissue (20), liver (1 l), and kidney (4). Radioactivity was detected at lower concentrations (>0.2 and <2 μgequivalents per gram of tissue) in the following tissues listed in order of decreasing concentration: 

lungs, spleen, thymus, blood, testicles, heart, muscle, and brain. In male rats given single oral doses of 

50 mg/kg [uniformly labeled 14C-phenyl]TOCP, peak concentrations of radioactivity were observed between 

2 and 48 hours after dosing (most tissues attained peak levels at 6 hours) in the following nongastrointestinal 

tissues, listed in order of decreasing concentration: urinary bladder, adipose tissue, liver, kidney, plasma, lungs, 

red blood cells, sciatic nerve, heart, spleen, testes, brain, spinal cord, and muscle (Abou-Donia et al. 1990a). The 

high concentration of radioactivity in the urinary bladder suggests that urinary excretion was significant (see 

Section 2.3.4). Similar evidence for widespread distribution of TOCP with preferential distribution to fat, liver, 

and kidneys was found in experiments in which male rats were given 10 daily doses of 50 mg/kg [uniformly 

labeled 14C-phenyl]TOCP (Somkuti and Abou-Donia 1990) and chickens were given single oral doses of 50 

mg/kg [uniformly labeled 14C-phenyl]TOCP(Abou-Donia et al. 1990b). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding distribution in humans or 

animals after oral exposure to polyalphaolefin hydraulic fluids. 

Based on physical and chemical similarities between mineral oil and polyalphaolefins, oil accumulation in the 

lung (and subsequent lipoid pneumonia) may occur following the ingestion of polyalphaolefin hydraulic 

fluids due to aspiration, and that distribution of polyalphaolefins to the liver and fatty tissues may occur to 

some degree (see-discussion for distribution of mineral oil hydraulic fluids). 
HYDRAULIC FLUIDS 156 

2. HEALTH EFFECTS 

2.3.2.3 Dermal Exposure 

No studies were located regarding distribution in humans or animals after dermal exposure to mineral oil or 

polyalphaolefin hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding distribution in humans 

after dermal exposure to organophosphate ester hydraulic fluids. 

A study with a dog exposed to an occluded dermal dose of TOCP labeled with radioactive phosphorus 

provides limited evidence that organophosphate esters in hydraulic fluids may be widely distributed after 

dermal absorption (Hodge and Sterner 1943). Similar widespread distribution of radioactivity among tissues 

was observed in male cats after dermal exposure to [uniformly labeled 14C-phenyl]TOCP (Nomeir and AbouDonia 1986). Tissues and fluids with the highest concentrations of radioactivity in these studies included the 

bile, gall bladder, urinary bladder, liver, kidney, and fat, thus suggesting that TOCP and metabolites are 

somewhat preferentially distributed to these tissues. 

Twenty-four hours after application of 2.094 g TOCP labeled with radioactive phosphorus to a 15x20 cm 

area of clipped and depilated abdominal skin, radioactivity was detected in the following tissues in a dog, 

listed in order of decreasing concentration (counts per gram of tissue): skin and facia at site of application, 

liver, omental fat, blood, kidney, lung, muscle (triceps femoris), spinal cord, heart, spleen = brain = sciatic 

nerve, and bone (femur) (Hodge and Sterner 1943). 

In male cats, peak concentrations of radioactivity in most tissues and fluids were observed 24 hours after 

application of 50 mg/kg [uniformly labeled 14C-phenyl]TOCP to unprotected areas of skin on the back of the 

neck (Nomeir and Abou-Donia 1986). Peak concentrations of radioactivity (reported in parentheses in units 

of μg TOCP equivalent per gram) were highest for collected bile (317), followed by gall bladder (39.7), 

urinary bladder (39.1), kidneys (25.3), liver (16.3), cecum (14.5), fat (12.0), plasma (12.1), and lungs (12.1). 

Radioactivity was also detected in the following cat tissues (listed in order of decreasing concentration) but at 

peak concentrations <10 ug TOCP equivalents per gram: large intestine, sciatic nerve, red blood cells, 

pancreas, small intestine, heart, stomach, muscle, spleen, brain, and spinal cord. The observation of 

radioactivity in the stomach suggests that cats in his study ingested TOCP during grooming. 
HYDRAULIC FLUIDS 157 

2. HEALTH EFFECTS 

2.3.3 Metabolism 

Mineral Oil and Polyalphaolefin Hydraulic Fluids. No studies were located regarding metabolism in 

humans or animals after exposure to mineral oil hydraulic fluids or polyalphaolefin hydraulic fluids. It should 

be noted, however, that hydrocarbons found in mineral oils generally are not expected to undergo extensive 

metabolism in animals or humans (Cannon 1940; IARC 1984). It may be speculated that polyalphaolefins 

may undergo limited metabolism of a similar nature. 

Experiments with monkeys given intramuscular injections of a mineral oil emulsion with [1 -14C]n-hexadecane 

tracer provide data illustrating that absorbed C-16 hydrocarbon (a major component of liquid petrolatum) is 

slowly metabolized to various classes of lipids (Bollinger 1970). Two days after injection, substantial portions 

of the radioactivity recovered in liver (30%), fat (42%), kidney (74%), spleen (8 l%), and ovary (90%) were 

unmetabolized n-hexadecane. The remainder of the radioactivity was found as phospholipids, free fatty acids, 

triglycerides, and sterol esters. Essentially no radioactivity was found in the water-soluble or residue fractions. 

One or three months after injection, radioactivity still was detected only in the fat-soluble fractions of the 

various organs, but 80-98% of the detected radioactivity was found in non-hydrocarbon lipids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding metabolism in humans 

after exposure to organophosphate ester hydraulic fluids. 

Studies directly examining the metabolism of organophosphate ester hydraulic fluids in animals are limited. 

One study identified metabolites in ether extracts of bile obtained from rabbits given single, 2 g/kg, oral 

doses of Reolube HYD46, a hydraulic fluid containing isopropylated triphenyl phosphates (35% 

mono-[o-isopropylphenyll-diphenyl phosphate, 25% di-[o-isopropylphenyll-phenyl phosphate, 10% 

tri-[o-isopropylphenyl] phosphate, and 7% triphenyl phosphate) (Yang et al. 1990). Metabolites were 

identified by mass spectrometry. Identified metabolites in extracts treated with ß-glucuronidase included 

isopropylated triphenyl phosphate derivatives hydroxylated at either the phenyl group or the isopropyl group. 

This finding is consistent with the hypothesis that Phase I oxidation reactions took place (presumably 

catalyzed by microsomal cytochrome P-450 mixed function oxidases) followed by Phase II glucuronicacidconjugation reactions. Two cyclic metabolites (in which only two of the original three phenyl groups 

remained) were identified in bile extracts without ß-glucuronidase treatment (Yang et al. 1990). This finding 

is consistent with the in vivo occurrence of cyclization reactions that split off one of the phenyl groups (which 
HYDRAULIC FLUIDS 158 

2. HEALTH EFFECTS
 

presumably leaves as phenol) and form a six-membered heterocyclic ring involving the α-carbon of the 

isopropyl residue on one of the remaining phenyl groups. These reactions are similar to those proposed to 

occur in the metabolism of TOCP (discussed in the next paragraph). No studies were located that definitively 

identify the enzymes involved in the formation of isopropylated triphenyl phosphate metabolites or their 

distribution among organs and within cells. 

The metabolism of TOCP has received considerable study because tricresyl phosphate isomers are widely 

used as plasticizers, flame retardants, and lubricants. TOCP is also widely used in mechanistic studies of 

organophosphate ester-induced neurotoxicity in animals. Cholinergic and delayed neuropathic responses to 

TOCP in humans are well known, and TOCP metabolism has been related to its biological activity (Casida et al. 

1961). Definitive in vivo and in vitro evidence for the participation of hydroxylation reactions and 

cyclization reactions (hydrolytic dearylation and cyclic rearrangements) in metabolism of TOCP was first 

presented for the rat (Eto et al. 1962, 1967). A particular cyclic metabolite, saligenin cyclic-ortho-tolyl 

phosphate, is generally thought to be the responsible agent for TOCP-induced delayed neuropathy. The 

metabolic production of this metabolite, however, does not necessarily predict the occurrence of delayed 

neuropathy, since it can be detected in various tissues (including brain tissue) in the rat, a species that does 

not display the classical symptoms of delayed neuropathy as seen in humans (Baron 1981; Casida et al. 1961; 

Eto et al. 1962; Somkuti and Abou-Donia 1990). 

A recent series of experiments with cats, chickens, or rats exposed to [uniformly labeled 14C-phenyl]-TOCP 

shows that a complex array of oxidized and dearylated metabolites are found in excreta and various tissues 

including the liver, kidney, testis, and brain (Abou-Donia et al. 1990a, 1990b; Nomeir and Abou-Donia 

1986; Somkuti and Abou-Donia 1990). Cats and chickens, like humans, are sensitive to TOCP-induced 

delayed neuropathy (Baron 1981). A similar array of oxidized and dearylated derivatives of tri-para-cresyl 

phosphate (but no cyclic metabolites) were identified by mass spectrometry in the urine and bile of rats orally 

exposed to tri-para-cresyl phosphate (Kurebayashi et al. 1985). In contrast to TOCP, tri-para-cresyl 

phosphate does not cause delayed neuropathy. The identified metabolites suggest that the metabolism of 

tricresyl phosphate isomers involves a complex array of Phase I and Phase II reactions including oxidations 

of the methyl and phenyl groups (to produce alcohols, aldehydes, and carboxylic acids, presumably via 

cytochrome P-450 mixed function oxidases), hydrolytic dearylations, cyclic rearrangements (for TOCP 

derivatives only), and conjugations with glucuronic acid or glutathione. A metabolic pathway for TOCP as 

proposed by Somkuti and Abou-Donia (1990) is illustrated in Figure 2-7. 

HYDRAULIC FLUIDS 160 

2. HEALTH EFFECTS
 

Eleven metabolites of [butyl-l14C]tributyl phosphate, an organophosphate ester used as a base stock in some 

aircraft hydraulic fluids (WHO 1991), were identified in urine from rats given single 250-mg/kg 

intraperitoneal injections of the compound (Suzuki et al. 1984a). Major metabolites included dibutyl 

hydrogen phosphate, butyl dihydrogen phosphate, and butyl bis(3-hydroxybutyl)phosphate. Several 

sulfurcontaining metabolites also were also identified in urine including (3-oxobutyl)- and (3-hydroxybutyl)-

mercapturic acids (Suzuki et al. 1984b). Two hours after administration of 1 mmole tributyl phosphate, 

levels of glutathione diminished to 55% and 75% of initial levels in liver and kidney, respectively (Suzuki et 

al. 1984b). Based on these data, a complex metabolic scheme for tributyl phosphate has been proposed 

involving mixed function oxidase-mediated oxidations of the butyl groups and glutathione-S-transferasemediated transalkylations (Suzuki et al. 1984b). Similarly complex metabolite profiles (19 metabolites) for 

tributyl phosphate after oral, dermal, and intravenous administration have also been seen in rats (Gatz 1992b). 

The preferential (although not exclusive) distribution of radioactivity to the liver and kidneys after dermal 

(Nomeir and Abou-Donia 1986) and oral (Abou-Donia et al. 1990a, 1990b; Kurebayashi et al. 1985; 

Somkuti and Abou-Donia 1990; Suwita and Abou-Donia 1990) exposure of cats, rats, and chickens to 

radiolabeled tricresyl phosphate isomers suggests that these organs may play important roles in the 

metabolism of organophosphate esters found in hydraulic fluids. Existing demonstrations of in vitro 

metabolism of TOCP with liver preparations emphasize the role of the liver (Casida et al. 196 1; Eto et al. 

1962). It is possible, however, that metabolism occurs at other sites, including the gastrointestinal tract and 

the testes. In rats given oral doses of [methyl-14C]tri-para-cresyl phosphate, 18% of the administered 

radioactivity was exhaled after 3 days as CO2: if rats were pretreated with neomycin, then expiration of 

radiolabeled CO2 decreased to 3% of the administered dose (Kurebayashi et al. 1985). The neomycininduced 

decrease in expired radioactivity suggests that a small, but measurable, portion of orally administered triaryl 

phosphates may be metabolized by gut microflora. Cultured Leydig cells from rat testes could metabolize TOCP 

to saligerin cyclic-o-tolyl phosphate (Chapin et al. 1990). 
HYDRAULIC FLUIDS 161 

2. HEALTH EFFECTS 

2.3.4 Elimination and Excretion 

2.3.4.1 Inhalation Exposure 

No studies were located regarding elimination and excretion in humans or animals after inhalation exposure 

to mineral oil hydraulic fluids, organophosphate ester hydraulic fluids, or to polyalphaolefin hydraulic fluids. 

2.3.4.2 Oral Exposure 

Mineral Oil Hydraulic Fluids. No studies were located regarding excretion in humans or animals after 

oral exposure to mineral oil hydraulic fluids. 

Experiments with rats given oral or intraperitoneal doses of tritiated mineral oil (Liquid Petrolatum USP) 

indicate that orally administered hydrocarbons in mineral oil are predominately excreted rapidly, unchanged, 

and unabsorbed in the feces and that absorbed mineral oil is slowly excreted in the feces (presumably via 

biliary excretion) (Ebert et al. 1966). 

Approximately 80% of administered radioactivity was excreted in the feces of rats within 2 days of oral 

administration of single 0.66 mL/kg doses of tritiated mineral oil (Ebert et al. 1966). Of administered 

radioactivity, 7-8% was excreted in the urine, but was in chemical forms other than mineral oil. The fecal 

radioactivity was predominately (90%) in the form of mineral oil. Pretreatment of the rats with 

0.66 ml/kg/day nonradioactive mineral oil for 3 1 days did not substantially alter the excretion patterns. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding excretion in humans 

after oral exposure to organophosphate ester hydraulic fluids. 

Studies with rats treated orally with triaryl or trialkyl phosphate esters (which may be found in 

organophosphate ester hydraulic fluids) indicate that these compounds and their metabolites are readily 

excreted in the urine, bile, feces and, to a limited extent, in expired air (Kurebayashi et al. 198.5; Somkuti and 

Abou-Donia 1990a; Suzuki et al. 1984a; Yang et al. 1990). Urinary excretion of metabolites appears to be the 

predominant elimination route in rats for tri-ortho-cresyl phosphate and tri-para-cresyl phosphate, but 

biliary excretion of parent material and metabolites is also important (Kurebayashi et al. 1985; NTP 1988). 

Fecal excretion may gain relative importance as an excretory route for tri-para-cresyl phosphate as doses 
HYDRAULIC FLUIDS 162 

2. HEALTH EFFECTS 

approach levels of ≈100 mg/kg (Kurebayashi et al. 1985; NTP 1988). Fecal excretion of tri-m-cresyl 

phosphate appears to be predominant in rats even at a dose level of 200 mg/kg (NTP 1988). 

In rats gavaged with 7.8 mg/kg [methyl-14C]tri-para-cresyl phosphate, most administered radioactivity was 

excreted in the urine (41%) and feces (44%) within 7 days of administration (Kurebayashi et al. 1985). 

Biliary excretion was estimated using a separate group of rats with cannulated bile ducts to account for -28% of 

administered dose. CO, in expired air accounted for 18% of administered radioactivity, but this 

diminished to 3% when the rats were pretreated with the antibiotic, neomycin (thereby indicating that some of 

the compound was metabolized by the gut microflora). Fecal excretion was relatively more important than 

urinary excretion after administration of a higher dose, 89.6 mg/kg tri-para-cresyl phosphate (77% versus 

12% of administered radioactivity, respectively). Unchanged tri-para-cresyl phosphate was reported to be 

the main fecal “metabolite,” thereby indicating that absorption may have been incomplete at the higher dose. 

Half-lives of radioactivity in tissues were reported to range from 14 hours for blood to 26 hours for lungs and 

brain. 

In rats given 10 daily 50-mg/kg doses of [phenyl-14C]TOCP, 63.1% and 36.1% of administered radioactivity 

was excreted in the urine and feces, respectively, within 4 days of the last administration (Somkuti and AbouDonia 1990a). Most of the radioactivity in urine was in metabolites found in an acid hydrolysate fraction, 

emphasizing the importance of Phase II metabolism in the disposition of TOCP (see Section 2.3.3). Major 

metabolites in feces included (in order of decreasing abundance) o-cresol, unchanged TOCP, “unknowns,” and 

o-hydroxybenzoic acid. The authors reported that TOCP concentrations in brain, liver, kidney, testis, and plasma 

decreased exponentially within 4 days of the last dosing; estimated half-lives ranged from approximately 12 

hours (0.49 days) in brain tissue to 24 hours (0.98 days) in the liver. The authors did not calculate half-lives for 

total radioactivity in tissues or plasma, but in a related study, the same group of investigators reported that the 

approximate half-life of radioactivity in tissues in general was 1 day in rats treated with single doses of 50 

mg/kg [phenyl-14C]TOCP (Abou-Donia et al. 1990a). 

Patterns of excretion in rats differed among [14C]labeled tricresyl phosphate isomers administered by gavage at 

dosage levels ranging from 0.5 to 200 mg/kg (NTP 1988). Radioactivity from tri-ortho-cresyl phosphate was 

excreted within 24 hours predominately in urine at all dosage levels (270% of applied doses). Radioactivity 

from tri-m-cresyl phosphate was excreted predominately in feces at all dosage levels. In contrast, urinary 

excretion of radioactivity from tri-para-cresyl was the predominant excretory route at low 

doses (0.5 or 2 mg/kg), while fecal excretion was the primary route at higher doses (20 or 200 mg/kg). 
HYDRAULIC FLUIDS 163 

2. HEALTH EFFECTS
 

Male rats given single, oral doses of 14 mg/kg [l-14C]tributyl phosphate excreted 50% of the label in urine, 

10% in exhaled air as CO2and 6% in the feces within 1 day (Suzuki et al. 1984a). Within 5 days, 

cumulative radioactivity in urine, exhaled CO2and feces accounted for approximately 68%, 10%, and 10% 

of the administered radioactivity, respectively. 

Studies with chickens treated with single oral doses of 50 mg/kg [phenyl-14C]TOCP provide general 

corroborative data for the ready excretion of TOCP and metabolites (Abou-Donia et al. 1990b; Suwita and 

Abou-Donia 1990). However, the relative importance of urinary and fecal excretion cannot be ascertained 

from these studies, because feces and urine were not separated. Approximately 47% of administered 

radioactivity was found in excreta by 12 hours after administration; radioactivity in excreta collected for 

5 days accounted for 99% of administered radioactivity (Abou-Donia et al. 1990b). Plasma half-lives of 

TOCP and saligenin cyclic-ortho-tolyl phosphate, the putative neurotoxic agent in TOCP, were reported to 

be 53 and 46 hours, respectively, and were compared with respective values of 46 and 19 hours for plasma 

half-lives in rats treated with single doses of [phenyl-14C]TOCP at the same dosage level (Abou-Donia 

1990a). The authors suggested that the clearance of TOCP and its metabolites in plasma and tissues is 

slower in the hen (which is sensitive to TOCP-induced delayed neuropathy) than in the rat (which is less 

sensitive) and that this apparent difference may contribute to the difference in responses between these 

species (Abou-Donia 1990a, 1990b; Suwita and Abou-Donia 1990). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding excretion in humans or animals 

after oral exposure to polyalphaolefin hydraulic fluids or major components. The physicochemical 

similarities between polyalphaolefins and mineral oils suggest that hydrocarbons in ingested polyalphaolefins 

may be excreted similarly to hydrocarbons in ingested mineral oil. 

2.3.4.3 Dermal Exposure 

Mineral Oil Hydraulic Fluids. No studies were located regarding excretion in humans or animals after 

dermal exposure to mineral oil hydraulic fluids or to their major components. -. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding excretion in humans 

after derrnal exposure to organophosphate ester hydraulic fluids. However, a human study using the tricresyl 

phosphate isomer tri-o&o-cresyl phosphate (TOCP) was located. 
HYDRAULIC FLUIDS 164 

2. HEALTH EFFECTS
 

Urinary excretion of radioactivity was measured in human volunteers during and after a 3.5-hour period of 

dermal exposure to 0.11 or 0.22 g 32P-labeled TOCP (Hodge and Sterner 1943). The specific activity of the 

test substance was not reported. Radioactivity in urine was measured with a Geiger-Muller counter, but the 

limits of detection were not reported. Maximum estimated excretion rates, 10 and 43 ug TOCP/hour for the 

respective dosage levels, were measured within 24 hours of initiation of exposure. Radioactivity was not 

detected 48 or 72 hours after dosing ceased. Cumulative radioactivity detected in urine accounted for 0.13% 

and 0.36% of the dermally applied radioactivity. 

Cyclotriphosphazene was not detected by gas chromatography in urine collected for 24 hours after occluded 

dermal exposure of rats to a hydraulic fluid containing 99.9% cyclotriphosphazene (Kinkead and Bashe 

1987). 

Urinary excretion of radioactivity has been observed in cats (Nomeir and Abou-Donia 1986) and a dog 

(Hodge and Sterner 1943) after dermal exposure to radiolabeled TOCP, thereby suggesting that this route of 

excretion is important following dermal exposure. In cats, cumulative excretion of radioactivity, within 

10 days of dermal exposure to [phenyl-14C]TOCP, reached 28% and 20% of the administered dose 

(50 mg/kg) via the urinary and fecal routes, respectively (Nomeir and Abou-Donia 1986). The importance of 

biliary excretion was demonstrated in cats by the observation that the peak concentration of radioactivity in 

bile was much higher than peak concentrations for any other analyzed tissue or body fluid (see 

Section 2.3.2.3.). Interpretation of the cat data should be addressed with caution, because a portion of the 

dose was probably ingested during grooming. Peak rates of urinary excretion of radioactivity (equivalent to 

202 pg TOCP/hour) were measured for a dog, 12 hours after initiation of a 25.5-hour exposure of a 

15x20 cm area of skin to 2.094 g TOCP labeled with radioactive phosphorus (Hodge and Sterner 1943). 

Radioactivity in urine collected during exposure (the dog was sacrificed immediately following exposure) 

accounted for 0.14% of the applied dose. Fecal or biliary excretion was not examined. 

Urinary excretion of radioactivity after a dermal dose of [14C]tributyl phosphate was 29944% of the applied 

dose in rats (Gatz 1992b). A large proportion of the dose (24-43%) was recovered in the sitewash at the end 

of the exposure. 
 

 

 

 

 

HYDRAULIC FLUIDS 165 

2. HEALTH EFFECTS
 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding excretion in humans or animals 

after dermal exposure to polyalphaolefin hydraulic fluids or major components. 

2.3.4.4 Other Routes of Exposure 

Mineral Oil Hydraulic Fluids. No studies were located regarding excretion in humans after exposure by other 

routes to mineral oil hydraulic fluids. 

Within 8 days of an intraperitoneal dose of 0.66 mL/kg tritiated mineral oil to rats, 11% of administered 

radioactivity was excreted in the feces, predominately in the form of mineral oil (95%) (Ebert et al. 1966). Urine 

during the same time frame after intraperitoneal administration contained about 8% of the administered 

radioactivity, but in chemical forms other than mineral oil. The detection of radioactivity in the feces after 

intraperitoneal administration suggests that significant biliary excretion of absorbed mineral oil can occur. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding excretion in humans 

after exposure by other routes to organophosphate ester hydraulic fluids. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding excretion in humans or animals 

after exposure by other routes to polyalphaolefin hydraulic fluids. 

2.4 MECHANISMS OF ACTION 

Mineral Oil Hydraulic Fluids. The mechanism whereby mineral oil hydraulic fluids may enter the blood from 

the lungs, skin or gastrointestinal tract is not known. In general, mineral oils and other petroleumderived 

materials are expected to be absorbed only to a limited extent by the lungs, skin, and the 

gastrointestinal tract (IARC 1984; Klein and Simon 1986), but data monitoring mineral oil hydraulic fluid 

components in the blood of animals or humans after exposure were not located. 

Data regarding the toxicity of mineral oil hydraulic fluids have not identified definitively specific end points 

or target organs. However, lipoid pneumonia, lung hemorrhaging, and subsequent death occurred in a 

14-month-old boy who ingested 5-10 cc of automobile transmission fluid, thereby indicating that significant 

aspiration of ingested mineral oil hydraulic fluid can occur (Perrot and Palmer 1992). Clinical experience 
 

HYDRAULIC FLUIDS 166 

2. HEALTH EFFECTS 

with hydrocarbon poisoning in children indicates that aspiration of ingested petroleum-derived products with 

subsequent pulmonary edema and hemorrhaging is common (Klein and Simon 1986). The molecular 

mechanism by which respiratory injury occurs is not known, but interaction of hydrocarbons in mineral oil 

with pulmonary surfactants has been proposed (Perrot and Palmer 1992). 

Organophosphate Ester Hydraulic Fluids. Information regarding the extent of absorption of 

organophosphate ester hydraulic fluids by the skin, lungs and gastrointestinal tract is very limited and the 

mechanism by which the organophosphate components of the fluids may enter the blood is unknown. 

The most clearly identified toxicological hazard associated with exposure to organophosphate ester hydraulic 

fluids involves the nervous system. Acute exposures to certain organophosphorus compounds, including certain 

organophosphate ester hydraulic fluids and organophosphorus insecticides, produce at least one of two types of 

neurological effects: acetylcholinesterase inhibition resulting in a host of rapidly appearing cholinergic 

symptoms and a slowly developing axonal degeneration and demyelination in central and peripheral nerve 

tissues resulting in neuropathy. The delayed neuropathy has been termed organophosphate induced delayed 

neuropathy (OPIDN). 

Organophosphorus cholinesterase inhibitors bind to nervous tissue acetylcholinesterase, thereby inhibiting 

the catalytic breakdown of the neurotransmitter, acetylcholine (Ecobichon 1991; Murphy 1986). The 

accumulation of acetylcholine at the nerve endings leads to a continual stimulation of electrical activity along 

the nerves. Signs of cholinergic toxicity associated with stimulation of muscarinic receptors in smooth 

muscles, the heart, and exocrine glands include bronchoconstriction and increased bronchial secretions, 

increased salivation, urination, diarrhea, and bradycardia. Signs associated with stimulation of nicotinic 

receptors in motor nerve junctions to skeletal muscles and autonomic ganglia include muscle weakness, 

tremors, muscle fasciculation, tachycardia, and hypertension. Signs associated with acetylcholine 

accumulation in the central nervous system include restlessness, ataxia, mental confusion, convulsion, and 

coma (see Table 2-10). 

Organophosphorus esters are known to react with a serine hydroxyl group in the active site of the 

acetylcholinesterase protein (Ecobichon 1991; Murphy 1986). Some organophosphorus esters (e.g., diisopropyl 

fluorophosphate, [DFP]) bind irreversibly, while others bind in a slowly reversible fashion, thereby leading to a 

slow reactivation (dephosphorylation) of the enzyme. A process known as “aging” has also been described in 

which reversibly bound compounds are changed with time to moieties that are essentially irreversibly 

HYDRAULIC FLUIDS 168 

2. HEALTH EFFECTS
 

bound to the enzyme. Dephosphorylation of reversibly inactivated acetylcholinesterase can be accelerated by 

certain chemicals, the best known of which is 2-pyridine aldoxime methiodide (pralidoxime). However, 

2-pyridine aldoxime methiodide does not dephosphorylate the “aged” phosphorylated enzyme. Thus, to be 

effective, 2-pyridine aldoxime methiodide must be administered before aging occurs (within 12-48 hours). 

Acute exposure to certain organophosphate esters produces a slowly developing neuropathy in humans, 

OPIDN, that is functionally characterized by initial weakness and subsequent ataxia and paralysis in the 

lower limbs (8-14 days or longer, following exposure) (Ecobichon 1991; Johnson 1975; Murphy 1986). In 

severe cases, paralysis may also affect the upper limbs. Recovery is usually slow and is not always complete. 

Tri-ortho-cresyl phosphate (TOCP), an isomer found in tricresyl phosphate, was the first organophosphate ester 

linked to OPIDN, being responsible for an epidemic of paralysis in the southeastern United States that led to the 

name “ginger jake paralysis” (Smith 1930) (see Section 2.4). Current manufacturing processes for 

organophosphate ester hydraulic fluids are designed to minimize production of this isomer, although it is 

possible that fluids disposed of in the past may be contaminated. 

Studies with TOCP have indicated that the delayed neurotoxic responses observed in the adult hen and the cat 

closely resemble the responses observed in humans and that other species (including the rat, rabbit, and mouse) 

are relatively insensitive to the delayed neurotoxicity of TOCP (Baron 1981). Other species that are sensitive to 

OPIDN include dogs, calves, sheep, and nonhuman primates (Baron 1981). Light- and electronmicroscopic 

studies with cats exposed to TOCP (Cavanagh and Patangia 1965) or di-isopropylfluorophosphate (another 

agent that produces OPIDN [Bouldin and Cavanagh 1979a, 1979b]) have associated the clinical signs of delayed 

paralysis with degeneration of the distal ends of the longest and largest axonal fibers. Although acute exposure 

to TOCP does not produce clinical signs of delayed neuropathy in the rat, it produces acetylcholinesterase 

inhibition, spinal cord histological damage, and inhibition of brain or spinal cord neurotoxic esterase (see next 

paragraph) in this insensitive species (Inui et al. 1993; Padilla and Veronesi 1995). Several hypotheses have 

been proposed to explain species differences in susceptibility to OPIDN including species differences in 

gastrointestinal absorption (Baron 198 l), in kinetics of tissue clearance (Abou-Donia 1990a, 1990b; Suwita and 

Abou-Donia 1990), and in unspecified neuroanatomical features (Baron 1981). 

The mechanism of OPIDN is poorly understood, but, since all organophosphate esters that produce OPIDN 

are either direct cholinesterase inhibitors or are metabolically converted to cholinesterase inhibitors, inhibition 

of an esterase of some kind has generally been thought to be involved (Baron 1981). Certain 
HYDRAULIC FLUIDS 169 

2. HEALTH EFFECTS
 

organophosphate esters, including TOCP, are known to require bioactivation before they induce OPIDN 

(Casida et al. 1961; Eto et al. 1962, 1967; Johnson 1975) (see Section 2.3.3). However, acetylcholinesterase 

inhibition in nervous tissue is not thought to be primarily involved in OPIDN, because a survey of a wide variety 

of organophosphate esters showed that not all organophosphate esters that inhibit acetylcholinesterase produce 

delayed neuropathy (Johnson 1975,1982,1990). The same study, however, found an association between 

inhibition of the esterase activity of a specific protein, termed “neurotoxic esterase” or “neuropathy target 

esterase” (NTE), and the development of delayed neuropathy (Johnson, 1982, 1990). Inhibition of brain NTE in 

animals (by approximately 70-80%) has been proposed as a screening tool or monitor to evaluate the potential 

of organophosphorus compounds to induce OPIDN (Ecobichon 1991; Johnson, 1982). Inhibition of lymphocytic 

NTE and inhibition of platelet NTE in humans have been proposed as surrogate markers for brain NTE (Lotti et 

al. 1984; Maroni and Bleeker 1986). When chickens were exposed to 3 organophosphorus esters, there was 

good correlation between lymphocyte and brain NTE for only 24 hours; after that lymphocyte NTE was not 

consistent with OPIDN or brain NTE (Schwab and Richardson 1986). Brain NTE inhibition appears to be a 

reasonable predictor of OPIDN. The physiological and/or molecular sequence of events involved in the 

development of OPIDN are not yet defined (Ecobichon 1991; Johnson 1990). 

Two types of OPIDN have been described in animals (Abou-Donia and Lapadula 1990). Type I is produced 

by compounds with a pentavalent phosphorus (like TOCP), and Type II is produced by compounds with a 

trivalent phosphorus. Characteristics used to differentiate between the types of OPIDN include species 

selectivity, age sensitivity, length of latent period, and morphology of neuropathologic lesions. Thus, at doses 

that did not produce death due to acetylcholinesterase inhibition, TOCP (a Type I compound) produced lesions 

in the spinal cord of rats without producing ataxia. In contrast, triphenyl phosphite (a Type II compound) 

produced delayed (1 week) ataxia in the rat and a distribution of spinal cord lesions distinct from those produced 

by TOCP (Abou-Donia and Lapadula 1990). 

Conclusions drawn from the review of a large number of organophosphate esters (Johnson 1975) indicate 

that potency for OPIDN depends on the following factors: 1) esters having one or more rings substituted in 

the ortho position are neurotoxic provided that the ortho-alkyl group has at least one hydrogen on the alpha 

carbon atom; 2) further substitution in the ring containing the ortho-substituent greatly reduces neurotoxicity; 

3) neurotoxicity is higher in isomers having only one ortho-substituent; 4) neurotoxicity decreases as the 

substituent on the ortho position becomes larger and more branched; 5) esters having no ortho-substituents 

are not neurotoxic. OPIDN has not been associated with trialkyl phosphates. 
HYDRAULIC FLUIDS 170 

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Tricresyl phosphate (a complex mixture containing tri-o, tri-m-, and tri-para-cresyl phosphate that is used in 

certain hydraulic fluids) and TOCP are demonstrated testicular toxicants in rodents (Carlton et al. 1987; 

Somkuti et al. 1987a, 1987b). Tricresyl phosphate also has been shown to impair in vivo fertility in rats and 

mice (Carlton et al. 1987; Chapin et al. 1988a). In addition, tricresyl phosphate-treated female rats displayed 

vacuolar cytoplasmic alteration of ovarian interstitial cells (Carlton et al. 1987; NTP 1994). Reproductive 

effects have also been seen after oral exposure to butylated triphenyl phosphate (Latendresse et al. 1994b). 

The mechanism of male reproductive toxicity, but not female reproductive toxicity, has received some 

research attention. The mechanism by which these substances affect the male reproductive system is not 

completely understood, but evidence indicates that the production of the testicular effects may involve 

bioactivation of TOCP to saligenin cyclic-ortho-tolyl phosphate in testicular Leydig cells (Chapin et al. 1990, 

1991) and the inhibition of esterases (nonspecific esterase, also known as butyrylcholinesterase or NSE, and 

neurotoxic esterase) by saligenin cyclic-ortho-tolyl phosphate in testicular Sertoli cells (Chapin et al. 1991; 

Somkuti et al. 1987a, 1991). Although inhibition of esterases in testicular cells has been associated with the 

occurrence of testicular effects including increased frequency of sperm with abnormal morphology, decreased 

sperm motility, and decreased epididymal sperm density, mechanistic details concerning the specific functions 

of these esterases currently are unknown. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding the absorption of 

polyalphaolefin hydraulic fluids following oral, inhalation, or dermal exposure of animals or humans. The 

mechanism whereby these materials may enter the blood stream is not known. 

Acute inhalation exposure to aerosols of certain polyalphaolefin hydraulic fluids produced death in rats 

associated with respiratory tract irritation, while aerosols of other polyalphaolefin hydraulic fluids produced 

no apparent respiratory tract irritation or deaths (MacEwen and Vemot 1983; Kinkead et al. 1987b, 1992b). 

The mechanism by which certain polyalphaolefin fluids may produce respiratory tract irritation is not 

understood. 
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2. HEALTH EFFECTS 

2.5 RELEVANCE TO PUBLIC HEALTH 

Overview. 

This profile covers three major classes of hydraulic fluids: mineral oil, organophosphate ester, and 

polyalphaolefin. Information on another phosphorus-containing hydraulic fluid, cyclotriphosphazene, is 

discussed with the organophosphate esters for convenience. The chemical identity and concentration of 

hydraulic fluid components may often be proprietary information. This profile primarily focuses on the 

toxicological properties of hydraulic fluids themselves (identified by commercial name when possible), rather 

than on the properties of known major components. This focus was taken because it is possible that the 

toxicity of any particular fluid is influenced by non-additive interactions among the components, as well as by 

the presence of unknown, but potentially toxic, compounds. The profile also discusses toxicological 

properties of several major organophosphate ester components of hydraulic fluids because components of a 

hydraulic fluid contaminating a waste site may be known without having toxicological data for the complete 

fluid. 

Mineral Oil Hydraulic Fluids. There is limited information on the toxicity of mineral oil hydraulic 

fluids in humans and animals. Death, respiratory effects, gastrointestinal effects, and neurotoxicity have been 

reported in humans. Severe respiratory effects and mild gastrointestinal effects were observed in a small child 

who accidentally ingested a lethal dose of automotive transmission fluid (Perrot and Palmer 1992). Peripheral 

neuropathy was observed in a worker heavily exposed to mineral oil hydraulic fluids by dermal contact 

(Jarvholm et al. 1986), although the toxicity in this case was attributed to an organophosphate ester additive 

(isopropyl triphenyl phosphate, 0.5%). The lack of corroborative case reports or epidemiology data make it 

difficult to extrapolate these data to populations living at or near hazardous waste sites. A series of acute animal 

inhalation, oral, and dermal exposure studies tested the toxicity of five different mineral oil hydraulic fluids 

(Kinkead et al. 1985, 1987a, 1989). No deaths, skin sensitization, neurotoxicity, or changes in body weight gain 

were observed. Following acute ocular exposure to four of the fluids, mild eye irritation was observed; the fifth 

fluid was not an ocular irritant but did cause moderate skin irritation. Dermal and ocular irritation may occur in 

humans heavily exposed to these same mineral oil hydraulic fluids. Reproductive and developmental end points 

have not been examined in animal studies. The most sensitive targets of toxicity of mineral oil hydraulic fluids 

cannot be identified from these data primarily because of the small number of end points that have been 

examined. Based on data on the laxative properties of mineral oil, it is likely that the gastrointestinal tract will 

be affected following oral exposure to mineral oil hydraulic fluid. 
 

 

HYDRAULIC FLUIDS 172 

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Additionally, there are data which suggest untreated distillates of petroleum and mildly solvent-refined or 

mildly hydrotreated mineral oils are carcinogenic (IARC 1984). However, highly refined mineral oils do not 

appear to be carcinogenic. The available data for mineral oils as a class are not adequate to predict whether a 

particular mineral oil hydraulic fluid will be carcinogenic because of the dependence of carcinogenic activity 

upon quality of the oil, presence of additives, and potentially, the conditions of use (JARC 1984). Mineral oil 

hydraulic fluids often contain organophosphate ester additives which may be relevant to assessment of toxicity. 

Organophosphate Ester Hydraulic Fluids. A number of studies have been conducted on 

organophosphate ester hydraulic fluids because of the well known neurotoxic effects caused by 

organophosphorus insecticides, organophosphorus nerve gases, and tri-ortho-cresyl phosphate (TOCP). The 

following manifestations of acute exposure to organophosphorus compounds have been described: 

1. cholinergic symptoms associated with acetylcholinesterase inhibition that develop within 4-12 hours

 of exposure (see Table 2- 10); 

2. “intermediate syndrome,” a paralysis of limb muscles and respiratory muscles developing within 

24-96 hours after the subsidence of cholinergic symptoms; and 

3. “organophosphorus-induced delayed neuropathy” (OPJDN), typically a paralytic condition of the legs,

 hands, or forearms developing within 7 or 14 days of first exposure (Ecobichon 1991). 

Because the “intermediate syndrome” has not been described for animals or humans exposed to hydraulic 

fluids, this syndrome is not discussed further in this profile. 

Some organophosphorus compounds are potent inhibitors of acetylcholinesterase, but do not produce 

OPIDN; while others display both activities. The chemical structure of organophosphate esters is linked to 

OPIDN; ortho substitution has been associated with neurotoxicity (Johnson 1975). Tri-ortho-cresyl 

phosphate (TOCP), an isomer of tricresyl phosphate, is a well-known example of an organophosphorus 

compound that induces OPJDN. Current manufacturing processes for tricresyl phosphate are designed to 

minimize production of this isomer. Contamination of an alcoholic extract of ginger (ginger jake) with TOCP 

in the southeastern United States produced an epidemic of neuropathies in the 1930s the symptoms of which 

became known as “ginger jake paralysis” (Smith et al. 1930). No such widespread exposure and outbreak of 
 

HYDRAULIC FLUIDS 173 

2. HEALTH EFFECTS
 

neuropathies in humans has been reported for organophosphate ester hydraulic fluids, but controlled animal 

studies have indicated that neurological effects are the most sensitive toxicological end points for certain 

organophosphate hydraulic fluids. 

Polyalphaolefin Hydraulic Fluids. No information on the toxicity of polyalphaolefin hydraulic fluids 

to humans was located. Acute animal inhalation, oral, and dermal exposure studies (Kinkead et al. 1985, 

1987a, 1992b; MacEwen and Vemot 1983) have examined a limited number of end points. The only end 

points examined in these studies were death, body weight gain, dermal and ocular irritation, and clinical signs of 

toxicity. Death, evidence of severe respiratory irritation, and lethargy were observed following inhalation 

exposure to relatively high concentrations of certain polyalphaolefin hydraulic fluids. Human exposure to high 

concentrations of these fluids may result in similar effects. No changes in body weight gain or evidence of 

neurotoxicity were observed following oral exposure. Following dermal exposure, mild eye and skin irritation, 

as well as skin sensitization were observed for some of the polyalphaolefin hydraulic fluids, and lethargy was 

observed for all of the polyalphaolefin hydraulic fluids. It is not known whether human exposure to relatively 

high dermal doses of polyalphaolefin hydraulic fluids will also result in lethargy. 

Reproductive and developmental end points have not been examined. The animal data are not sufficient to 

identify the most sensitive target(s) of toxicity of polyalphaolefin hydraulic fluids because only a limited 

number of end points have been examined. 

Minimal Risk Levels for Hydraulic Fluids. 

Rational assessment of the health hazard presented by hydraulic fluid(s) contaminating an environmental 

medium is not possible without knowing the identity of the contaminating fluid(s) and/or knowing something 

about the fluids chemical composition. Even if the identity of a contaminating fluid is known and there are 

sufficient toxicological data for the fluid to derive a Minimal Risk Level (MRL), any resultant hazard 

assessment would contain an inherent uncertainty because of compositional changes between production 

batches. Such changes are expected due to different starting materials and production practices (especially 

for fluids containing processed “natural materials” like mineral oil) and due to unreported changes in 

production formulation (e.g., change of additives) (see Chapters 3 and 5). Adding to the uncertainty is the 

possibility that processes in the environment (e.g., physical and biological transformations) may change the 

composition of the contaminating fluid from that used in toxicological testing. 
HYDRAULIC FLUIDS 174 

2. HEALTH EFFECTS 

Mineral Oil Hydraulic Fluids 

Inhalation MRLs. 

No inhalation MRLs were derived. 

Available data are restricted to acute lethality studies in rats exposed to four water-in-oil emulsion hydraulic 

fluids or a mineral oil hydraulic fluid for 4-6 hours. No deaths or body weight alterations occurred at 

exposure concentrations ranging from 180 to 2 10 mg/m3

 for the water-in-oil fluids and 1,130 mg/m3 for the 

mineral oil fluid. The data are inadequate for acute inhalation MRL derivation. No data regarding 

intermediate or chronic inhalation exposure to mineral oil hydraulic fluids were located. 

Oral MRLs. 

No oral MRLs were derived. 

The available data did not adequately identify target organs or effects. In acute lethality studies in rats 

gavaged with 5,000 mg/kg doses of the water-in-oil emulsion hydraulic fluids or mineral oil hydraulic fluids, 

no deaths or body weight changes occurred. One of these fluids was tested for neurotoxicity in chickens 

without effects. 

Organophosphate Ester Hydraulic Fluids 

Inhalation MRLs 

No inhalation MRLs were derived. 

No NOAELs or LOAELs were identified for toxic effects in humans after inhalation exposure to 

organophosphate ester hydraulic fluids. Reliable NOAELs and LOAELs for acute inhalation exposure are 

restricted to 4-hour NOAELs for systemic effects in rats exposed to Fyrquel220 or Durad MP280 and 

4-hour LOAELs for mild lethargy in rats exposed to Durad MP280 and Fyrquel 220 (Gaworski et al. 1986). 

The study identifying these NOAEL and LOAEL values did not measure cholinesterase inhibition, did not 

allow sufficient follow-up time for the development of delayed neurotoxic effects, and used a species that is 
HYDRAULIC FLUIDS 175 

2. HEALTH EFFECTS
 

relatively insensitive to OPIDN. An acute inhalation MRL was not derived for organophosphate ester 

hydraulic fluids as a class due to the inadequacy of the available data to assess the neurotoxicity of Fyrquel 

220 and Durad MP280 and the lack of any acute inhalation data for other organophosphate ester hydraulic 

fluids. 

There are insufficient data to derive hydraulic fluid-specific acute-duration inhalation MRLs. No systemic 

effects were observed in rats exposed to 6,350 mg/m3

 of Durad MP280 for 4 hours (Gaworski et al. 1986). 

Mild lethargy was observed 1-3 hours post-exposure to 6,190 and 6,350 mg/m3

. Longer-term inhalation 

exposure to Durad MP280 resulted in testicular atrophy in rats (MacEwen and Vemot 1983). Reproductive 

end points have not been examined following acute inhalation exposure. In rats exposed to Fyrquel 220, no 

systemic effects were observed following exposure to 6,3 10 mg/m3

 and mild lethargy was observed at 

≥5,790 mg/m3 (Gaworski et al. 1986; Kinkead et al. 1992a). The short duration of the study (single 4-hour 

exposure), the lack of testing in a species sensitive to the neurotoxic effects, and the lack of reproductive 

testing (especially for Durad MP280) precludes deriving acute-duration inhalation MRLs for Durad MP280 

and Fyrquel 220. 

Reliable intermediate-duration inhalation NOAELs and LOAELs were located for systemic effects in rats and 

rabbits exposed to several organophosphate ester hydraulic fluids (Durad MP280, Fyrquel 220, Skydrol 

500B-4, or Cellulube 220) and cyclotriphosphazene. Neurological effects were observed in rats, rabbits, 

dogs, hamsters, monkeys, and hens exposed to Durad MP280, Fyrquel 220, Skydrol 500B-4, Cellulube 220, 

or triaryl phosphate. In addition, reproductive effects (histological alteration of reproductive organs) were 

observed in rats, rabbits, and hamsters exposed to cyclotriphosphazene, Durad MP280, or Fyrquel 220. 

Based on the lowest LOAEL, the most sensitive end point appears to be the neurological effects. The 

NOAELs for neurological effects ranged from 4.4 to 260 mg/m3 and the range of serious LOAELs was 23 to 

2,000 mg/m3

. Not all of the organophosphate ester hydraulic fluids tested had the same targets. For 

example, head droop and generalized weakness or lethargy were observed in rabbits exposed to 2,000 mg/m3 

(lowest concentration tested) of Cellulube 220 4 hours/day, 4-5 days/week for 11 or 22 days (Carpenter et al. 

1959) and 101 mg/m3 of Durad MP280 continuously for 90 days (MacEwen and Vemot 1983). No neurological 

effects were observed in rabbits continuously exposed to 100 mg/m3

 of Fyrquel 220 for 90 days (MacEwen and 

Vemot 1983). Testicular atrophy was observed in rats continuously exposed to 101 mg/m3

 Durad MP280, but 

not in rats continuously exposed to Fyrquel 220 for 90 days (MacEwen and Vemot 1983), rats exposed for 13 

weeks (6 hours/day, 5 days/week) to Skydrol 500B-4 (Healy et al. 1992; Monsanto 1987a, 1987b, 1989), or rats 

exposed to 990 mg/m3

of cyclotriphosphazene for 21 days (6 hours/day, 
HYDRAULIC FLUIDS 176 

2. HEALTH EFFECTS 

5 days/week) (Kinkead et al. 1989b, 1990). No intermediate inhalation MRL was derived for 

organophosphate ester hydraulic fluids as a class because of the uncertainty that derivation of a MRL based 

on data for a single fluid with the lowest identified threshold would be representative for other fluids in the 

class. 

The available inhalation data for Durad MP280, Fyrquel 220, Cellulube 220, Skydrol 500B-4, and 

cyclotriphosphazene (reviewed in the next paragraph) are inadequate to derive intermediate-duration MRLs 

for these individual fluids, principally because the studies were conducted in species (rats or rabbits) that are 

generally considered to be insensitive to the delayed neurotoxicity of acute exposure to organophosphate esters. 

Cats, dogs, or nonhuman primates more accurately model the human expression of OPIDN than rats and rabbits, 

and studies in these species would provide a better basis for MRL derivation. 

Following a 90-day continuous exposure to 101 mg/m3

 of Durad MP280, leukocytosis, kyphosis, and 

testicular atrophy were observed in rats and 100% mortality, cachexia, head droop, anorexia, and lethargy 

were observed in rabbits. No effects were observed in either species at 10.3 mg/m3

 Durad MP280 (MacEwen 

and Vemot 1983). Continuous exposure to 100 mg/m3

 of Fyrquel220 for 90 days resulted in kyphosis in rats 

(MacEwen and Vemot 1983); the NOAEL for this effect was 10.1 mg/m3

. No adverse effects were observed in 

rabbits exposed to 100 mg/m3

 Fyrquel 220 continuously for 90 days (MacEwen and Vemot 1983). At the lowest 

tested concentration of Cellulube 220 (2,000 mg/m3

, 4 hours/day, 4-5 days/week for 11 or 22 days), severe 

dyspnea, head droop, and generalized weakness were observed in rabbits (Carpenter et al. 1959). No adverse 

effects were observed in rats exposed to 990 mg/m3

 of cyclotriphosphazene (6 hour/day, 5 days/week) for 21 

days (Kinkead et al. 1989b, 1990). Exposure of rats to Skydrol500B-4 for 13 weeks (6 hours/day, 5 days/week) 

resulted in nasal discharge at 100 mg/m3

, decreased erythrocyte, hemoglobin, and hematocrit levels at 300 

mg/m3

, and decrease in plasma cholinesterase activity at 300 mg/m3 (Healy et al. 1992; Monsanto 1987a, 1987b, 

1989). Mild hepatocellular vacuolization and excessive salivation, a sign of cholinergic neurotoxicity, were also 

observed in these studies at 300 mg/m3

. The lowest LOAEL is 5.3 mg/m3 Skydrol 500B-4 for nasal effects. No 

chronic exposure data were located. 
HYDRAULIC FLUIDS 177 

2. HEALTH EFFECTS 

Oral MRLS 

No oral MRLs were derived. 

No data are available regarding systemic or neurological effects in humans after oral exposure to 

organophosphate ester hydraulic fluids. The acute oral data base consists of a number of studies examining 

limited end points. Effects associated with cholinesterase inhibition (e.g., diarrhea) and OPIDN have been 

observed. Extensive testing of organophosphate ester hydraulic fluids in chickens (this species is generally 

thought of as one of the most sensitive to the neurotoxicity of organophosphorus compounds and a valid 

model species for identifying neurotoxic potential in humans) has demonstrated that there is a wide diversity 

in the ability of organophosphate ester hydraulic fluids to produce neurological effects. Some fluids produced no 

signs of neurological effects in chickens after administration of substantial doses (e.g., Pydraul29ELT, 

Pydraul50E, and Pydraul90E), other fluids produced only subtle neurological effects (e.g., Skydrol500B-4, 

Skydrol LD-4, and Reofos 65), and a few produced frank neurological effects (OPIDN) at comparatively low 

doses (e.g., Cellulube 220 and Fyrquel 150). A comparison of the relative toxicity of the different 

organophosphate ester hydraulic fluids is difficult because many of the studies only tested one dose level or a 

NOAEL was not identified. For hydraulic fluids causing cholinesterase inhibition effects, the LOAELs ranged 

from 120 mg/kg/day in rabbits for Cellulube 220 (Carpenter et al. 1959) to 5,750 mg/kg in rats exposed to 

Fyrquel 220 (Gaworski et al. 1986; Kinkead et al. 1992a). NOAELs for this effect were not 

reported. Inhibition of brain neurotoxic esterase and butyrylcholinesterase were observed in chickens 

exposed to approximately 2,600 mg/kg Skydrol500B-4 (Monsanto 1987d) or Skydrol LD-4 (Monsanto 

1987c) and 114 mg/kg Fyrquel EHC (Stauffer Chemical Co. 1981). The range of LOAELs for OPIDN was 

60 mg/kg/day for chickens exposed to Cellulube 220 for 5 days (Carpenter et al. 1959) to 11,350 mg/kg in 

chickens exposed once to Fyrquel EHC (Stauffer Chemical Co. 1980). 

Derivation of an acute-duration oral MRL for organophosphate ester hydraulic fluids as a class based on the 

lowest identified reliable LOAEL for neurological effects in chickens (60 mg/kg/day Cellulube 220 for leg 

and wing weakness) (Carpenter et al. 1959) is not recommended for two reasons. First, the LOAEL is a 

serious LOAEL (no NOAEL was identified in the study) and MRLs are not derived from serious LOAELs. 

Second, the wide diversity in the apparent neurotoxicities among members of the class indicates that 

derivation of an MRL based on data for a single fluid may not be representative for the class. Acute-duration 

oral MRLs for individual organophosphate ester hydraulic fluids have not been proposed. In addition, 
HYDRAULIC FLUIDS 178 

2. HEALTH EFFECTS
 

although chickens have been identified as a good species for qualitatively identifying the neurotoxicity of 

organophosphate esters, the extrapolation of chicken doses to human doses is uncertain. 

Reliable NOAELs and LOAELs for intermediate oral exposure are restricted to a 90-day NOAEL of 

50 mg/kg/day for systemic toxicity in rats (a species that is not sensitive to the neuropathic effects of 

organophosphate esters) exposed to Pydraul 90E for 90 days and NOAELs and LOAELs for delayed 

neuropathy in chickens exposed to Durad 110. In chickens exposed to Durad 110 for 28 days, a NOAEL of 

444 mg/kg/day and LOAEL of 1,333 mg/kg/day were identified (FMC 1986); when the duration was 

increased to 90 days, the NOAEL was 20 mg/kg/day and the LOAEL was 90 mg/kg/day (FMC 1986). These 

data are inadequate for derivation of an intermediate oral MRL for organophosphate ester hydraulic fluids. 

As discussed under the acute-duration oral MRL section, there is uncertainty regarding extrapolation of 

chicken doses to human doses. 

No data were located regarding chronic oral exposure to organophosphate ester hydraulic fluids 

Toxicity data are available for several organophosphate ester components of hydraulic fluids, in particular 

tricresyl phosphate (NTP 1994). However, these components are always present in products as mixtures with 

other chemicals. Since insufficient information exists to assess the effect on toxicity of interactions among these 

mixtures, MRLs for the components were not derived. 

Polyalphaolefin Hydraulic Fluids 

Inhalation MRLs 

No inhalation MRLs were derived. 

No data were located regarding toxic effects in humans following inhalation exposure to polyalphaolefin 

hydraulic fluids. Three of nine tested polyalphaolefin hydraulic fluids were lethal in rats at 4-hour aerosol 

concentrations ranging from <5,330 to <10,720 mg/m3

. LC50 values for the three lethal fluids in females 

ranged from 1,390 to 1,670 mg/m3

. Deaths were associated with respiratory irritation. The data are 

inadequate for acute inhalation MRL derivation. No intermediate or chronic inhalation MRLs for 

polyalphaolefin hydraulic fluids were derived due to the lack of data. 
HYDRAULIC FLUIDS 179 

2. HEALTH EFFECTS 

Oral MRLS 

No oral MRLs were derived. 

No data were located regarding toxic effects in humans following oral exposure to polyalphaolefin hydraulic 

fluids. No deaths or body weight changes occurred in rats in a series of acute lethality studies with nine 

polyalphaolefin hydraulic fluids at doses ranging from 4,250 to 5,000 mg/kg. One of these fluids was also 

tested for neurotoxicity in chickens, and did not produce effects at 4,250 mg/kg. The available data have not 

identified a target organ or effect for these fluids. The data are inadequate for MRL derivation. No 

intermediate or chronic oral MRLs for polyalphaolefin hydraulic fluids were derived due to the lack of data. 

Death. 

Mineral Oil Hydraulic Fluids. Only one report was located regarding death in humans following exposure to 

mineral oil hydraulic fluids. A 14-month-old boy ingested 5-10 cc of a mineral oil hydraulic fluid and died 4 

weeks later after developing pneumonia (Perrot and Palmer 1992). Postmortem analysis revealed edema, 

hemorrhages, and lipoid/oil droplets in the lungs. The attending physicians believed that the development of 

lipoid pneumonia with marked interstitial pneumonitis eventually led to death. 

Acute lethality studies in animals exposed by inhalation, ingestion, or dermal contact to several mineral oil 

hydraulic fluids indicate that mineral oil fluids are not potent toxicants. Mineral oil hydraulic fluids produced 

no deaths in rats after 4-hour exposures to aerosol concentrations of 11 0-2 10 mg/m3

or gavage 

administration of single doses <5,000 mg/kg (Kinkead et al. 1987a, 1988). Rabbits, likewise, did not die 

after single 24-hour exposures to occluded dermal doses of several mineral oil hydraulic fluids <2,000 mg/kg 

(Kinkead et al. 1985,1987a, 1988). 

Organophosphate Ester Hydraulic Fluids. No reports were located regarding deaths in humans 

following exposure to organophosphate ester hydraulic fluids. As reviewed in Section 2.2, acute to intermediate 

exposures to certain organophosphate ester hydraulic fluids, but not all tested fluids in this class, have produced 

lethal neurotoxic effects in animals through effects associated either with cholinesterase inhibition or delayed 

development of axonal degeneration and demyelination. Evidence is available that humans are susceptible to 

both types of neurotoxicity by organophosphorus compounds in general (Johnson 1982; Smith 
HYDRAULIC FLUIDS 180 

2. HEALTH EFFECTS 

et al. 1930), indicating that lethal neurotoxic effects may occur in humans at appropriate dosage levels and 

exposure durations. 

Lethal neurotoxicity in animals occurred after inhalation and oral exposure at levels that may be considered 

high for most environmental media. Lethal neurotoxic effects have not been observed in controlled studies 

with animals dermally exposed to several organophosphate ester hydraulic fluids at 24-hour dose levels 

< 2,000 mg/kg (Gaworski et al. 1986; Kinkead et al. 1992a), but combined dermal and oral acute exposure of 

cows to waste from reclamation of an organophosphate hydraulic fluid produced lethal neurotoxic effects 

(Julian et al. 1976). The lowest lethal aerosol concentrations of organophosphate hydraulic fluids identified 

in animals after acute to intermediate inhalation exposure were for the U.S. military fluid, triaryl phosphate: 

23 mg/m3

 in chickens and 102 mg/m3 in rabbits exposed continuously for 30-160 days (Siegel et al. 1965). 

The lowest lethal doses of organophosphate hydraulic fluids identified in animals after acute to intermediate 

oral exposure were for Cellulube 220 in rabbits given 120 mg/kg/day for 2-14 days (Carpenter et al. 1959) 

and for Fyrquel 150 in chickens given single doses of 300 mg/kg (Stauffer Chemical Co. 1971). Oral 

exposure to tricresyl phosphate for up to 2 years had no effect on mortality in rats or mice (NTP 1994). 

Polyalphaolefin Hydraulic Fluids. Reports of deaths in humans following exposure to polyalphaolefin 

hydraulic fluids were not located. Inhalation of several polyalphaolefin hydraulic fluids (N501, MIL-83282­

LT, and BSS-174) produced deaths in rats associated with acute respiratory irritation and congestion (4-hour 

LC50 values ranged from 1,390 to 1,670 mg/m3

 for females). Several other polyalphaolefin fluids produced no 

deaths after 4-hour exposures to 5,350-10,720 mg/m3

(Kinkead et al. 1987b, 1992b; MacEwen and Vernot 1983). 

None of these fluids produced deaths in animals following single gavage doses <5,000 mg/kg. 

Systemic Effects. 

Respiratory Effects. 

Mineral Oil Hydraulic Fluids. There is a paucity of data on respiratory effects following inhalation, oral, 

ordermal exposure to mineral oil hydraulic fluids. The only available information for humans comes from a case 

report of a child ingesting a lethal dose of an automotive transmission fluid, which was most likely amineral oil 

hydraulic fluid. Lipoid pneumonia with marked fibrosis was observed (Perrot and Palmer 1992). It is likely that 

some of the fluid was aspirated and that the oil caused irritation of the lung tissue. Lipoidpneumonia is 

frequently reported among people who chronically use medicated oils via intranasa sprays or 
HYDRAULIC FLUIDS 181 

2. HEALTH EFFECTS
 

nose drops (Cannon 1940; Lushbaugh 1950). It is unlikely that individuals living at or near hazardous waste 

sites contaminated with mineral oil hydraulic fluids would ingest (and subsequently aspirate) or inhale 

sufficient mineral oil to produce lipoid pneumonia. In the only animal study available, histopathological 

examination of the lungs from rats exposed to < 1.0 mg/m3

 of the water-in-oil emulsion hydraulic fluid 

Houghto-Safe 5047F for 90 days, 23 hours/day, showed no treatment-related lesions (Kinkead et al. 1991). 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding respiratory effects in humans 

after inhalation, oral, or dermal exposure to organophosphate ester hydraulic fluids. The most commonly 

reported respiratory effects in animals are dyspnea and rapid respirations. These effects have been observed in 

rabbits exposed to 2,000 mg/m3 of airborne Cellulube 220 (Carpenter et al. 1959); in cows and goats exposed to 

oral doses of 5,000 and 7,700 mg/kg of Cellulube 220, respectively, (Dollahite and Pierce 1969); in cows eating 

grass contaminated with Fyrquel 150 (Beck et al. 1977); in cows orally exposed to 500 mg/kg (Beck et al. 

1977); and in rabbits dermally exposed to Cellulube 220 (Carpenter et al. 1959). It is likely that the respiratory 

effects observed shortly after exposure were the result of acetylcholinesterase inhibition (see section on 

neurological effects for more information on cholinesterase inhibition) rather than a direct effect on the 

respiratory tract. Other respiratory effects include nasal discharge in rats exposed to Skydrol 500B-4 for an 

intermediate duration (Healy et al. 1992; Monsanto 1987a, 1987b, 1989) and rats orally exposed to Durad 110 

for an acute duration (FMC 1990a); bronchopneumonia in rabbits acutely exposed to orally administered 

Cellulube 220 (Carpenter et al. 1959); and emphysema and intralobular fibrosis in cows eating grass 

contaminated with Fyrquel 150 (Beck et al. 1977). It is not known whether the respiratory effects observed 

following oral exposure to organophosphate ester hydraulic fluids were due to aspiration of the hydraulic fluid. 

Following acute and intermediate inhalation exposure to a number of organophosphate ester hydraulic fluids, 

including Fyrquel 220, Durad MP280, and cyclotriphosphazene, no evidence of gross and/or histological 

damage was observed in rats, rabbits, hamsters, dogs, monkeys, and hens (Carpenter et al. 1959; Gaworski et al. 

1986; Kinkead et al. 1989a, 1990; MacEwen and Vemot 1983; Siegel et al. 1965). Based on the observations of 

dyspnea in cows, goats, and rabbits exposed to hydraulic fluids, it is likely that sufficient exposure to 

organophosphate ester hydraulic fluids that contain acetylcholinesterase inhibitors would result in dyspnea in 

humans. 

Polyalphaolefin Hydraulic Fluids. No information was located on the toxicity of polyalphaolefin hydraulic 

fluids to the respiratory tract of humans following inhalation, oral, or dermal exposure. Animal data suggest 

that certain airborne polyalphaolefin hydraulic fluids may be respiratory tract irritants. Bloody nasal 

discharge, rapid and shallow breathing, lung congestion, and perivascular and peribronchial edema have been 
HYDRAULIC FLUIDS 182 

2. HEALTH EFFECTS
 

observed in rats acutely exposed to polyalphaolefin hydraulic fluids (Kinkead et al. 1987b, 1992b; MacEwen 

and Vemot 1983). No information was located on respiratory effects in animals orally or dermally exposed 

to polyalphaolefin hydraulic fluids. 

Cardiovascular Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding cardiovascular effects in humans after 

inhalation, oral, or dermal exposure to mineral oil hydraulic fluids. In the only animal study available, 

histopathological examination of the hearts from rats exposed to ≤1.0 mg/m3

 of the water-in-oil emulsion 

hydraulic fluid Houghto-Safe 5047F for 90 days, 23 hours/day, showed no treatment-related lesions (Kinkead et 

al. 1991). 

Organophosphate Ester Hydraulic Fluids. No studies regarding cardiovascular effects in humans after 

inhalation, oral, or dermal exposure to organophosphate ester hydraulic fluids or cyclotriphosphazene were 

located. Animal data suggest that the cardiovascular system would not be a direct target of organophosphate 

ester hydraulic fluid toxicity. No gross and/or histological damage was observed in animals intermediately 

exposed to airborne Fyrquel 220, Durad MP280 (Gaworski et al. 1986; MacEwen and Vemot 1983), Skydrol 

500B-4 (Healy et al. 1992; Monsanto 1976a, 1987b, 1989), cyclotriphosphazene (Kinkead et al. 1989a, 1990), 

or triaryl phosphate hydraulic fluids (Carpenter et al. 1959; Siegel et al. 1965); acute oral doses of triaryl 

phosphate hydraulic fluids (Carpenter et al. 1959; Kinkead et al. 1989b) or intermediate oral doses of Pydraul 

90E (Monsanto 1979); or to intermediate dermal applications of Fyrquel 220 (MacEwen and Vemot 1983), 

cyclotriphosphazene (Kinkead et al. 1989a, 1990), or Cellulube 220 (Carpenter et al. 1959). Although no direct 

histological effects on the cardiovascular system have been observed in studies with organophosphate ester 

hydraulic fluids, organophosphate esters that inhibit acetylcholinesterase can overstimulate muscarinic receptors 

in the heart resulting in bradycardia or complete heart block (arrest) (Murphy 1986). Tachycardia can also result 

due to stimulation of sympathetic ganglia to overcome bradycardia due to muscarinic overstimulation (Murphy 

1986). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding cardiovascular effects in humans 

after inhalation, oral, or dermal exposure to polyalphaolefin hydraulic fluids or in animals after inhalation or 

dermal exposure. The only information available on the cardiovascular effects of polyalphaolefin hydraulic 

fluids is a histopathology finding that oral exposure to MIL-H-83282 and MIL-H-83282LT for 4 weeks at 

<1,000 mg/kg/day in the rat had no effect on the heart (Mattie et al. 1993). 
HYDRAULIC FLUIDS 183 

2. HEALTH EFFECTS 

Gastrointestinal Effects. 

Mineral Oil Hydraulic Fluids. The only information available on gastrointestinal effects in humans or 

animals exposed to mineral oil hydraulic fluids is from a case report of a child ingesting a lethal dose of 

automotive transmission fluid, which was probably a mineral oil hydraulic fluid. Subserosal hemorrhages 

were observed in the small and large intestine and omentum (Perrot and Palmer 1992). Focal gastritis with 

edema was also noted in rats receiving 1,000 mg/kg/day of MIL-H-5606 (Mattie et al. 1993). Mineral oils 

(petroleum-derived aliphatic hydrocarbons) are known to have laxative effects, to interfere with absorption of 

essential fat-soluble substances, and to cause foreign body reactions in the intestinal mucosa (Brunton 1985). 

These data, however, are not adequate to determine the likelihood of individuals living at or near hazardous 

waste sites having gastrointestinal effects from exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. Gastric upset and diarrhea have been reported in humans 

following oral exposure to organophosphate ester hydraulic fluid components (Goldstein et al. 1988; 

Srivastava 1990). In animals, the most widely reported gastrointestinal effect is diarrhea. Diarrhea (or soft 

feces) has been observed following oral exposure of rats to Durad MP280 (Gaworski et al. 1986), rabbits to 

Cellulube 220 (Carpenter et al. 1959; Dollahite and Pierce 1969), hens to Skydrol 500B-4 (Monsanto 1987d) 

or Skydrol LD-4 (Monsanto 1987c), and cows to Cellulube 220 (Dollahite and Pierce 1969) or Fyrquel 150 

(Beck et al. 1977). Diarrhea (or soft feces) has also been observed in rabbits dermally exposed to Fyrquel 

220 (Gaworski et al. 1986; MacEwen and Vemot 1983) or Cellulube 220 (Carpenter et al. 1959). The 

studies that reported diarrhea did not conduct histological examinations of the gastrointestinal tract. 

However, it is possible that the diarrhea was the result of acetylcholinesterase inhibition (see discussion on 

neurological effects) rather than direct damage to the gastrointestinal tract. In other studies, gastrointestinal 

effects have not been observed in rats, rabbits, and hamsters exposed to Fyrquel 220 or Durad MP280 

(MacEwen and Vemot 1983) Skydrol 500B-4 (Healy et al. 1992; Monsanto 1987a, 1987b, 1989), 

cyclotriphosphazene (Kinkead et al. 1989a, 1990), or Cellulube 220 (Carpenter et al. 1959). Because the 

gastrointestinal effects are possibly the result of acetylcholinesterase inhibition rather than direct damage, it is 

likely that there will not be route-specific differences. Based on the results of the animal studies, it is likely 

that humans exposed to sufficient organophosphate ester hydraulic fluids to inhibit acetylcholinesterase will 

exhibit gastrointestinal effects. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding gastrointestinal effects in humans or 

animals after inhalation, oral, or dermal exposure to polyalphaolefin hydraulic fluids. 
HYDRAULIC FLUIDS 184 

2. HEALTH EFFECTS 

Hematological Effects. 

Mineral Oil Hydraulic Fluids. No information on hematological effects in humans after inhalation, oral, or 

dermal exposure to mineral oil hydraulic fluids is available. In another animal study, a statistically 

significant reduction of 16% was reported in the percentage of lymphocytes in whole blood in rats receiving 

1,000 mg/kg/day MIL-H-5606 by gavage for 26 days (Mattie et al. 1993). 

Organophosphate Ester Hydraulic Fluids. There is limited information on hematological effects following 

exposure to organophosphate ester hydraulic fluids. In workers dermally exposed to triaryl phosphate 

hydraulic fluids for an intermediate duration, no changes in the levels of leukocytes were observed (Baldridge et 

al. 1959). This study is limited because leukocyte levels were the only hematological parameter monitored. No 

other human studies examining hematological parameters were located. Significant decreases in erythrocyte, 

hemoglobin, and hematocrit levels were observed in rats exposed to 300 mg/m3 of Skydrol 500B-4 (Healy et al. 

1992; Monsanto 1987a, 1987b, 1989) and leukocytosis was observed in male rats exposed to 101 mg/m3 Durad 

MP280 (MacEwen and Vemot 1983); both of these studies were for intermediate durations. A number of 

intermediate-duration animal studies examined hematological parameters, but no significant effects were found. 

Hematological examinations were made after inhalation exposure to Durad MP280, Fyrquel 220, and 

cyclotriphosphazene (Gaworski et al. 1986; Kinkead et al. 1989a, 1990; MacEwen and Vemot 1983); oral 

exposure to Pydraul90E (Monsanto 1979); and dermal exposure to cyclotriphosphazene (Kinkead et al. 1989c, 

1990) and Fyrquel 220 (MacEwen and Vemot 1983). Studies of oral exposures to MIL-H-83306 also have 

shown decreased hematocrits, erythrocyte numbers, and hemoglobin at levels of 250 mg/kg and 500 mg/kg, 

respectively (Mattie et al. 1993). A chronic-duration study of oral exposure to tricresyl phosphate for 2 years in 

rats and mice showed no alteration in hematological parameters (NTP 1994). 

Polyalphaolefin Hydraulic Fluids. Studies examining hematological effects in humans or animals 

following inhalation, oral, or dermal exposure to polyalphaolefin hydraulic fluids are limited to a 4-week 

study in rats orally exposed to 1,000 mg/kg/day of MIL-H-83282 or MIL-H-83282LT (Mattie’et al. 1993). 

No effect was seen with MIL-H-83282 but reductions in total and mean cell hemoglobin as well as anemia 

were seen in rats exposed to MIL-H-83282LT. 
HYDRAULIC FLUIDS 185 

2. HEALTH EFFECTS 

Musculoskeletal Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding musculoskeletal effects in humans or 

animals after inhalation, oral, or dermal exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No human studies examining musculoskeletal effects 

following inhalation, oral, or dermal exposure to organophosphate ester hydraulic fluids were located. No 

musculoskeletal abnormalities were observed in rabbits and hens orally exposed to Cellulube 220 for an acute 

duration (Carpenter et al. 1959). In rats, kyphosis was observed following intermediate-duration exposure to ≈

100 mg/m3

 of Durad MP280 or Fyrquel 220 (MacEwen and Vemot 1983). It is not known if this deformity of 

the spine characterized by extension flexion is the result of damage to musculoskeletal system or a neurological 

effect. No histological damage to the skeletal muscle was observed following intermediateduration inhalation 

exposure of rats or dermal exposure of rabbits to cyclotriphosphazene (Kinkead et al. 1989a, 1989~ 1990) or 

rabbits to Cellulube 220 (Carpenter et al. 1959). There is insufficient information to determine the likelihood of 

humans having musculoskeletal effects following exposure to organophosphate ester hydraulic fluids. 

Polyalphaolefin Hydraulic Fluids. There is limited information on the potential of polyalphaolefin 

hydraulic fluids to induce musculoskeletal effects. Kyphosis, a deformity of the spine characterized by 

extension flexion was observed in rats exposed to 880-5,030 mg/m3

 (concentration eliciting response not 

reported) of a polyalphaolefin hydraulic fluid designated at B85-174 for 4 hours (Kinkead et al. 1987b). It is 

not known if this effect is related to damage to the musculoskeletal system or to neurological damage. This is 

the only study that examined musculoskeletal effects. Thus, the likelihood of musculoskeletal effects 

occurring in humans exposed to polyalphaolefin hydraulic fluids cannot be determined. 

Hepatic Effects. 

Mineral Oil Hydraulic Fluids. No studies regarding hepatic effects in humans following inhalation, oral, or 

dermal exposure to mineral oil hydraulic fluids were located. In an animal study, histopathological 

examination of the livers from rats exposed by inhalation to < 1.0 mg/m3

 of the water-in-oil emulsion 

hydraulic fluid Houghto-Safe 5047F for 90 days, 23 hours/day, showed no treatment-related lesions (Kinkead et 

al. 1991). Animal data for oral exposure are limited to one study where rats were exposed to MLH-5606 
HYDRAULIC FLUIDS 186 

2. HEALTH EFFECTS 

at 1,000 mg/kg/day for 26 days (Mattie et al. 1993). Increases in liver weight and peroxisomal betaoxidation 

activity were observed. 

Organophosphate Ester Hydraulic Fluids. No human exposure studies examining hepatic end points were 

located. Several hepatic effects have been observed in animals after exposure to organophosphate ester 

hydraulic fluids. Mild hepatocellular vacuolation and increased liver weight were found in rats exposed to 300 

mg/m3 Skydrol500B-4 (Healy et al. 1992; Monsanto 1987a, 1987b, 1989). Increased smooth 

endoplasmic reticulum was seen with increased liver weight after oral exposure in rats to MIL-H-83306 at 

500 mg/kg/day for 26 days (Mattie et al. 1993). Evidence of adverse histological alterations and/or changes 

in serum enzymes indicative of liver damage was not observed in other inhalation studies (Carpenter et al. 

1959; Healy et al. 1992; Kinkead et al. 1989a, 1990, 1992a; Monsanto 1987a, 1987b, 1989; Siegel et al. 

1965), in oral exposure studies (Carpenter et al. 1959; Monsanto 1979), or in dermal exposure studies 

(Carpenter et al. 1959; Kinkead et al. 1989c, 1990; MacEwen and Vemot 1983). Increased fatty 

accumulation and decreased hepatocyte vacuolization, along with increased absolute and relative liver weights 

were observed in rats orally exposed to dibutylated phenyl phosphate for 91 days at 250 mg/kg/day (Healy et al. 

1991). Minimal to mild papillary hyperplasia of the gallbladder mucosa was observed in mice orally exposed to 

tricresyl phosphate at 11 0-230 mg/kg/day for 13 weeks (NTP 1994). In 2-year feeding studies, clear cell foci, 

fatty change, and ceroid pigmentation were observed in mice but not in rats (NTP 1994). 

Polyalphaolefin Hydraulic Fluids. The only information available on hepatic effects of polyalphaolefin 

hydraulic fluids in humans or animals is a report of increased peroxisomal beta-oxidation and serum alkaline 

phosphatase after oral exposure in rats to 1,000 mg/kg/day MIL-H-83282 for 26 days (Mattie et al. 1993). 

Increased peroxisomal beta-oxidation but no increase in serum alkaline phosphatase was observed in rats 

similarly treated with MIL-H-83282LT. 

Renal Effects. 

Mineral Oil Hydraulic Fluids. The only information regarding renal effects in humans or animals following 

inhalation, oral, or dermal exposure to mineral oil hydraulic fluids are two animal studies. Histopathological 

examination of the kidneys from rats exposed to ≤1.0 mg/m3

 of the water-in-oil emulsion hydraulic fluid 

Houghto-Safe 5047F for 90 days, 23 hours/day, showed no treatment-related lesions (Kinkead et al. 1991). 

Persistent diuresis, and increased protein and protein/creatinine ratios in the urine were reported in rats orally 
HYDRAULIC FLUIDS 187 

2. HEALTH EFFECTS
 

exposed to 1,000 mg/kg/day MIL-H-5606 for 26 days (Mattie et al. 1993). Hyaline droplets were also 

observed in the proximal tubule on histopathological examination. 

Organophosphate Ester Hydraulic Fluids. No human studies examining renal end points were located. No 

renal effects were observed in rats exposed by inhalation to ≈6,300 mg/m3

 of Durad MP280 or Fyrquel 220 for 4 

hours (Gaworski et al. 1986; Kinkead et al. 1992a) or in rabbits exposed orally to 120 mg/kg/day 

Cellulube 220 for ≤14 days (Carpenter et al. 1959). A minimal to mild accumulation of hyaline droplets was 

found in the kidneys of male and female rats exposed to ≥240 mg/m3

 of cyclotriphosphazene for 90 days 

(Kinkead et al. 1989a, 1990). Orally exposed mice showed renal tubule degeneration at 430-730 mg/kg/day 

tricresyl phosphate over 13 weeks (NTP 1994). Urinary bladder hyperplasia was observed after oral 

exposure in rats to tributyl phosphate at 55-350 mg/kg (Healy et al. 1991; Laham et al. 1985). In rabbits 

exposed dermally to >2,882 mg/kg/day of Fyrquel 220 for an intermediate duration, significant increases in 

serum urea nitrogen and creatinine levels were observed (MacEwen and Vernot 1983); this study did not 

report the results of histological examination of the kidneys. Interpretation of this study is complicated by the 

fact that one of the rabbits was infected with Pasturella. Other intermediate-duration inhalation studies have 

found no gross or histological damage in the kidneys of rats, rabbits, hamsters, dogs, monkeys, and hens 

exposed to Durad MP280 (Gaworski et al. 1986; MacEwen and Vernot 1983) Fyrquel 220 (Gaworski et al. 

1986; MacEwen and Vernot 1983), Skydrol 500B-4 (Healy et al. 1992; Monsanto 1987a, 1987b, 1989), 

Cellulube 220 (Carpenter et al. 1959), and a triaryl phosphate hydraulic fluid (Siegel et al. 1965). In 

addition, no evidence of renal damage was observed following intermediate-duration exposure of rats to oral 

doses of Pydraul 90E (Monsanto 1979), rabbits to topical cyclotriphosphazene (Kinkead et al. 1989c, 1990), 

or rabbits to topical Cellulube 220 (Carpenter et al. 1959). 

Polyalphpolejin Hydraulic Fluids. The only information on renal effects in humans or animals following 

inhalation, oral, or dermal exposure to polyalphaolefm hydraulic fluids is a report of increased urinary protein 

to creatinine ratio of rats orally exposed to MIL-H-83282 at 1,000 mg/kg/day for 4 weeks. Diuresis was 

noted in rats similarly exposed to MIL-H-83282LT (Mattie et al. 1993). 

Endocrine Effects. 

Mineral Oil Hydraulic Fluids. No information on endocrine effects in humans or animals following 

inhalation, oral of dermal exposure to mineral oil hydraulic fluids was located. 
HYDRAULIC FLUIDS 188 

2. HEALTH EFFECTS
 

Organophosphate Ester Hydraulic Fluids. No information on endocrine effects in humans following 

inhalation, oral, or dermal exposure to organophosphate ester hydraulic fluids was located. 

There are some equivocal data suggesting that the adrenal gland is a target for organophosphate ester hydraulic 

fluid toxicity. Nodular hyperplasia was observed in the adrenal cortex of one of two dogs examined following 

20 subcutaneous injections of an unspecified amount of Cellulube 220 (Carpenter et al. 1959). No adrenal 

effects were observed in rats continuously exposed to 100 mg/m3

 Fyrquel 220 or 101 mg/m3 Durad MP280 for 

90 days (MacEwen and Vemot 1983); rats exposed to 300 mg/m3

 Skydrol 500B-4,6 hours/day, 5 days/week for 

13 weeks (Healy et al. 1992; Monsanto 1987a, 1987b, 1989); or rabbits inhaling 2,000 mg/m3

 Cellulube 220,4 

hours/day, 4-5 days/week for 11 or 22 days (Carpenter et al. 1959). Rabbits receiving repeated dermal exposure 

(6 hours/day, 5 days/week for 21 days) to 1,000 mg/kg cyclotriphosphazene (Kinkead et al. 1989c, 1990) did not 

have adrenal effects. In a reproductive toxicity study (Chapin et al. 1988) in which male and female mice were 

exposed to 62.5 mg/kg of a mixture of tricresyl phosphates containing <0.1% pure TOCP, hypertrophy of the 

zona fasciculata cells and brown degeneration of cells in the juxtamedullary zone were observed in the adrenal 

gland. Tricresyl phosphate, a widely used fire-retardant additive for hydraulic fluids, produced minimal to 

moderate cytoplasmic vacuolization of the adrenal cortex of rats and mice exposed orally for subchronic and 

chronic durations (NTP 1994). Both tricresyl phosphate and butyl triphenyl phosphate treatment resulted in 

bilaterally enlarged adrenal glands and lipidosis and vacuolization of the adrenal cortex in rats orally exposed to 

400 mg/kg/day for 20-60 days (Latendresse et al. 1994a). 

Polyalphaolefin Hydraulic Fluids. No information on endocrine effects in humans or animals following 

inhalation, oral, or dermal exposure to polyalphaolefin hydraulic fluids was located. 

Dermal Effects. 

Mineral Oil Hydraulic Fluids. No human studies examining dermal end points were located. In animals, no 

information on dermal effects following inhalation or oral exposure were located. A number of mineral oil 

hydraulic fluids have been tested for acute dermal toxicity in rabbits. Signs of skin irritation have been observed 

following application of a naphthenic petroleum-based hydraulic fluid designated as MIL-H-5606 (Kinkead et 

al. 1985). No signs of skin irritation were observed following exposure to Sunsafe‘F, Houghto- Safe 5047F, 

Quintolubric 9583OW, or Pyroguard A-443 (Kinkead et al. 1987a, 1988). 

Organophosphate Ester Hydraulic Fluids. No studies regarding dermal effects in humans after inhalation 

or oral exposure were located. Erythema was observed in humans repeatedly exposed to dermal patches of 
HYDRAULIC FLUIDS 189 

2. HEALTH EFFECTS
 

Skydrol 500B-4 for an intermediate duration (Monsanto 1980). Skin scabbing was seen after oral exposure 

to Sanitizer 154 at 300 mg/kg (IRDC 1981). 

Signs of skin irritation were observed in one acute dermal exposure study. A single application of 0.5 mL of 

Durad 550B resulted in mild erythema and skin thickening in rabbits (FMC 1992a). No signs of skin 

irritation or evidence of histological damage were observed in rabbits exposed once to Durad 220B, Durad 

110, Durad 300, Durad MP280, Durad 125, Fyrquel 220, or cyclotriphosphazene (FMC 1990a, 1991 b; 

Gaworski et al. 1986; Kinkead et al. 1992a, 1992c, 1992d, 1992e; MacEwen and Vet-not 1985) or after 

intermediate-duration dermal exposure of rabbits to Fyrquel 220, cyclotriphosphazene, or Cellulube 220 

(Carpenter et al. 1959; Kinkead et al. 1989c, 1990; MacEwen and Vet-not 1983). No evidence of skin 

damage was located in hens ingesting Cellulube 220 for 5 days (Carpenter et al. 1959), or following 

intermediate-duration inhalation exposure of rats, rabbits, or hamsters to Fyrquel 220 or Durad MP280 

(MacEwen and Vemot 1983), rabbits to Cellulube 220 (Carpenter et al. 1959), or rats to cyclotriphosphazene 

(Kinkead et al. 1989a, 1990). 

Polyalphaolejin Hydraulic Fluids. No studies regarding dermal effects in humans following inhalation, 

oral, or dermal exposure to polyalphaolefin hydraulic fluids were located. Mild skin irritation was observed 

following a single application of a polyalphaolefin hydraulic fluids designated as DTNSRDC N501 and 

N5 17. No signs of skin irritation were observed following single applications of polyalphaolefin hydraulic 

fluids designated as DTNSRDC N448, N518, N525, N527 (MacEwen and Vemot 1983), B85-174 (Kinkead 

et al. 1987b), or meeting military specifications of MIL-H-83282 (Kinkead et al. 1985) or MIL-H-83282LT 

(Kinkead et al. 1992b). 

Based on these data, it is not likely that acute exposure of humans to environmental levels of polyalphaolefin 

hydraulic fluids will result in dermal irritation. There is insufficient information to determine if long-term 

exposure to polyalphaolefin hydraulic fluids will result in dermal irritation in humans. 

Ocular Effects. 

Mineral Oil Hydraulic Fluids. No human studies examining ocular end points were located. In animals, no 

information on ocular effects following inhalation or dermal exposure were located. Mild eye irritation was 

observed in rabbits following a single application of 0.1 mL of Sunsafe F, Houghto-Safe 5047F, Quintolubric 
HYDRAULIC FLUIDS 190 

2. HEALTH EFFECTS
 

9583OW, or Pyroguard A-443 (Kinkead et al. 1987a, 1988). No signs of irritation were observed following 

application of MIL-H-5606 (Kinkead et al. 1985). 

Organophosphate Ester Hydraulic Fluids. No studies regarding ocular effects in humans after inhalation 

or oral exposure were located. 

Eye irritation was not observed in animal studies following a single application of 0.1 mL of Fyrquel 220 

(Gaworski et al. 1986; Kinkead et al. 1992e), Durad MP280 (Gaworski et al. 1986; Kinkead et al. 1992d), or 

cyclotriphosphazene (Kinkead et al. 1992c; MacEwen and Vernot 1985). No evidence of eye damage was 

observed in hens ingesting Cellulube 220 for 5 days (Carpenter et al. 1959), or following intermediateduration 

exposure of rats, rabbits, or hamsters to aerosols of Fyrquel220 or Durad MP280 (MacEwen and Vet-not 1983), 

rabbits to Cellulube 220 (Carpenter et al. 1959), or rats to cyclotriphosphazene (Kinkead et al. 1989a, 1990). 

Polyalphaolefin Hydraulic Fluids. No studies regarding ocular effects in humans following inhalation, oral, 

or dermal exposure to polyalphaolefin hydraulic fluids were located. Evidence of eye irritation was observed 

in rats following a single ocular application or acute exposure to airborne polyalphaolefin hydraulic fluids 

with a designation of MIL-H-83282LT (Kinkead et al. 1992b). No signs of eye irritation were observed 

following single ocular applications of polyalphaolefin hydraulic fluids designated as DTNSRDC N448, 

N501, N517, N518, N525, N528 (MacEwen and Vemot 1983), B85-174 (Kinkead et al. 1987b), or meeting 

military specifications of MIL-H-83282 (Kinkead et al. 1985) or MIL-H-83282LT (Kinkead et al. 1992b). 

Based on these data, it is not likely that acute exposure of humans to environmental levels of polyalphaolefin 

hydraulic fluids will result in ocular irritation. There is insufficient information to determine if long-term 

exposure to polyalphaolefin hydraulic fluids will result in ocular irritation in humans. 

Body Weight Effects. 

Mineral Oil Hydraulic Fluids. There is limited information on body weight effects following exposure to 

mineral oil hydraulic fluids. No studies were located regarding body weight effects in humans following 

inhalation, oral, or dermal exposure to mineral oil hydraulic fluids. In rats, no changes in body weight gain 

were observed following acute inhalation, oral, or dermal exposure to Sunsafe F, Quintolubric 9583OW, 

Houghto-Safe 5047F, or Pyroguard A-443 (Kinkead et al. 1989b, 1988) and a mineral oil hydraulic fluid 
HYDRAULIC FLUIDS 191 

2. HEALTH EFFECTS
 

meeting military specifications of MIL-H-5606 (Kinkead et al. 1985). Body weights of rats exposed to 

<1.0 mg/m3

 of the water-in-oil emulsion hydraulic fluid Houghto-Safe 5047F for 90 days, 23 hours/day, were 

similar to those of controls (Kinkead et al. 1991). No longer-term studies were located. Based on this limited 

information, it is not likely that effects on body weight will be observed in humans acutely exposed to 

environmental levels of mineral oil hydraulic fluids. The likelihood of changes in body weight occurring 

following longer-term exposure to mineral oil hydraulic fluids is not known. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding body weight effects in humans 

following inhalation, oral, or dermal exposure to organophosphate ester hydraulic fluids. 

Most animal studies found no significant alterations in body weight gain following inhalation, oral, or dermal 

exposure to a number of organophosphate ester hydraulic fluids. Several studies demonstrated weight loss 

following acute or intermediate oral exposure to high doses. The identified LOAEL values were 

250 mg/kg/day in rats exposed to dibutyl phenyl phosphate for an intermediate duration (Healy et al. 1991), 

5,775 mg/kg/day in rats acutely exposed to Durad MP280 (Gaworski et al. 1986) or 10,000 mg/kg and 

15,000 mg/kg/day in hens acutely exposed to Reofos 65 or Fyrquel EHC for acute exposures, respectively, 

(Mortensen and Ladefoged 1992), and 1,333 mg/kg/day in hens exposed to Durad 110 for an intermediate 

duration (FMC 1986). No changes in body weight gain were observed in rats, rabbits, hamsters, hens, 

monkeys, or dogs exposed to Fyrquel 220, Skydrol 500B-4, cyclotriphosphazene, a triaryl phosphate hydraulic 

fluid, Durad MP280 (<5,775 mg/kg/day oral), Durad 550B, Durad 100, Durad 300, Durad 110, Durad 220B, 

Pydraul 50E, or Pydraul 90E (Ciba-Giegy 1973; FMC 1986, 1990a, 1992a; Gaworski et al. 1986; Healy et al. 

1992; Kinkead et al. 1989a, 1989c, 1990, 1992a, 1992c; MacEwen and Vernot 1983, 1985; Monsanto 1979, 

1987a, 1987b, 1989; Siegel et al. 1965) via inhalation, oral, or dermal exposure. High oral doses of 

organophosphate esters have caused body weight changes. In a dose-finding study using 5 pregnant rats per 

group, a 12% decrease in maternal weight gain was noted after 11 days at 200 mg/kg/day tributyl phosphate 

(Noda et al. 1994) but in a larger study with 20 animals per group, only minor body weight reductions were 

observed at 500 mg/kg/day. Several intermediate-duration studies showed reduction in body weight gain in rats 

or mice. Thirteen-week feeding exposures to tricresyl phosphate in rats at 430 mg/kg/daywere associated with 

an 11% reduction in body weight in both males and females (NTP 1994). Exposure to 750 mg/kg/day caused a 

33% decrease in body weight in male rats. Treatment by gavage for 13 weeks, 5 days a week did not affect 

female body weight at ≤800 mg/kg/day; male body weight was decreased 13% at this dose (NTP 1994). Body 

weight effects were also reported in mice in this study, decreases greater than 10% were seen in female mice at 

530 mg/kg/day and above and in males at 900 mg/kg/day exposed to tricresyl phosphate by feed 
HYDRAULIC FLUIDS 192 

2. HEALTH EFFECTS
 

Gavage doses greater than 400 mg/kg/day also caused decreased body weight (NTP 1994). Dibutyl phenyl 

phosphate exposure for 91 days at 250 mg/kg/day in female rats was observed to cause a 15% body weight 

reduction (Healy et al. 1991). Butylated triphenyl phosphate exposure at 1,000 mg/kg/day for 106 days caused 

an 1 l-17% decrease in body weight in Fischer 344 rats (Latendresse et al. 1994b). Similar results have been 

reported with exposure to tributyl phosphate in rats: a 15% decrease at 300 mg/kg/day for 18 weeks (Laham et 

al. 1985) and an 11% decrease at 250 mg/kg/day for 9 weeks (Oishi et al. 1982). Based on these animal data, it 

is not likely that human exposure to organophosphate ester hydraulic fluids at concentrations expected to be 

found at or near hazardous waste sites will result in changes in body weight. 

Polyalphaolefin Hydraulic Fluids. No information on body weight effects in humans after inhalation, oral, or 

dermal exposure to polyalphaolefin hydraulic fluids was located. In acute rabbit inhalation, oral, or dermal 

exposure studies, no changes in growth were observed following exposure to polyalphaolefm hydraulic fluids 

designated as DTNSRDC N448, N501, N5 17, N518, N525, or N528 (MacEwen and Vemot 1983) B85-174 

(Kinkead et al. 1987b), or polyalphaolefin hydraulic fluids meeting military specifications of MIL-H-83282 

(Kinkead et al. 1985) or MIL-H-83282LT (Kinkead et al. 1992b). These acute exposure animal studies suggest 

that short term human exposure to polyalphaolefin hydraulic fluids will not result in alterations of body weight 

gain. There is insufficient information to determine longer-term human risks. 

Immunological and Lymphoreticular Effects. 

Mineral Oil Hydraulic Fluids. No information was located regarding immunological effects in humans after 

inhalation, oral, or dermal exposure to mineral oil hydraulic fluids. Limited animal testing provided no clear 

evidence that the immune system is a target for mineral oil hydraulic fluids. In guinea pig skin sensitization 

assays, four of five tested mineral oil hydraulic fluids were inactive as skin sensitization agents, and the 

remaining fluid only showed weak activity (Kinkead et al. 1985, 1987a, 1988). This information is inadequate to 

determine the likelihood of immunological effects occurring in humans exposed to environmental media 

contaminated with mineral oil hydraulic fluids, due to the limited number of immunological end points 

examined. The data suggest, however, that skin sensitization may not be a major concern with dermal exposure 

to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding immunological effects in 

humans or animals after inhalation or oral exposure to organophosphate ester hydraulic fluids. No dermal 

sensitization reactions were observed in humans exposed to Skydrol 500B-4 for three 24-hour periods per 
HYDRAULIC FLUIDS 193 

2. HEALTH EFFECTS
 

week for 5 weeks (Monsanto 1980) or in guinea pigs exposed for 10 days to a cyclotriphosphazene-based 

hydraulic fluid (Kinkead et al. 1992c; MacEwen and Vernot 1985). Thymus weight decreases (both absolute 

and relative to body weight) were observed, without histological alterations, in rabbits exposed dermally to 

cyclotriphosphazene for 21 days (Kinkead et al. 1989c, 1990). No histological alterations were observed in the 

tbymus of rats exposed to aerosols of cyclotriphosphazene for 2 1 days (Kinkead et al. 1989a, 1990). Although 

there are no data for many organophosphate ester hydraulic fluids, the limited data suggest that skin 

sensitization may not be a concern with dermal exposure to organophosphate ester hydraulic fluids. High doses 

(2,905 mg/kg/day) of tricresyl phosphate, a widely used fire-retardant hydraulic fluid additive, produced 

necrosis of the mandibular lymph node, the spleen, and the thymus in mice exposed by gavage for 16 days (NTP 

1994). No such lesions, however, were noted in mice treated with 1,452 mg/kg/day for 16 days or in mice 

treated with doses <800 mg/kg/day for 90 days (NTP 1994). A moderate level of tricresyl phosphate, 5 

mg/kg/day, in an oral exposure study caused a reduction in serum tetanus antibodies (Banerjee et al. 1992). 

Polyalphaolefin Hydraulic Fluids. Two U.S. military polyalphaolefm hydraulic fluids, MIL-H-83232LT and 

B85-174, produced skin sensitization in guinea pigs (Kinkead et al. 1987b, 1992b), but seven other 

polyalphaolefin hydraulic fluids did not produce sensitization (Kinkead et al. 1985; MacEwen and Vemot 

1983). No other studies were located regarding immunological effects in animals or humans exposed to 

polyalphaolefm hydraulic fluids. This information suggests that skin sensitization may occur in humans after 

dermal exposure to MIL-H-83282LT or B85-174, but not after dermal exposure to the other polyalphaolefin 

hydraulic fluids. The lack of data for other immunological end points precludes determination of the 

immunotoxicity of polyalphaolef hydraulic fluids. 

Neurological Effects. 

Mineral Oil Hydraulic Fluids. Peripheral neuropathy developed in a man after about 2 years of heavy 

occupational exposure by dermal contact to mineral oil hydraulic fluids, at least one of which was known to 

contain organophosphate esters (0.5% isopropylated triphenyl phosphate and <50 ppm TOCP) (Jarvholm et al. 

1986). Subtle electromyographical effects were measured in four of eight men exposed to lower levels of 

mineral oil hydraulic fluids for 3 months to 13 years (Jarvholm et al. 1986). Other studies regarding 

neurological effects in humans after exposure to mineral oil hydraulic fluids were not located. 

The lack of corroborative case reports, epidemiological data, or animal data (see next paragraph) makes the 

association between dermal exposure to mineral oil hydraulic fluids and peripheral neuropathy uncertain. 
HYDRAULIC FLUIDS 194 

2. HEALTH EFFECTS
 

Nonetheless, the presence of organophosphate esters, some of which are demonstrated neurotoxic agents, in 

most mineral oil hydraulic fluids (they often are added as anti-wear agents) suggests that they may play a 

causative role if such an association exists. 

Several mineral oil hydraulic fluids (Sunsafe F, Houghto-Safe 5047F, Quintolubric 9583OW, Pyroguard 

A-443, and MIL-H-5606) produced no clinical signs of neurotoxicity in rabbits after acute occluded dermal 

exposure (2,000 mg/kg doses), in rats after acute inhalation exposure (110 -210 mg/m3

 for 4 hours or 

1,148 mg/m3

 for 6 hours), or in chickens or rats after single gavage dose administration (5,000 mg/kg) 

(Kinkead et al. 1985,1987a, 1988). 

In conclusion, the limited animal and human data suggest that acute to intermediate exposures to mineral oil 

hydraulic fluids do not represent a major hazard to the neurological health of workers or the general public. 

The possible presence of low levels of neurotoxic organophosphate esters in these fluids, however, may lead to 

some concern to limit exposure. 

Organophosphate Ester Hydraulic Fluids. Certain organophosphorus compounds produce at least one of two 

types of acute neurological effects in humans and certain animal species - cholinesterase inhibition 

associated with acute symptoms including diarrhea, sweating, salivation, respiratory depression and 

generalized weakness (see Section 2.2.1.4 and Table 2-l 0), and acute organophosphorus-induced delayed 

neuropathy (OPIDN) associated with the delayed development of incoordination, limb weakness, ataxia and 

axonal degeneration, and demyelination in spinal cord and peripheral nerve tissues (Abou-Donia and 

Lapadula 1990; Minton and Murray 1988). Only one study was located examining humans for neurological 

effects following acute or intermediate exposure to an organophosphate ester hydraulic fluid, and no evidence 

for the occurrence of neurological effects was found (Baldridge et al. 1959). However, several 

organophosphate ester hydraulic fluids have produced one or both of these types of neurological effects in 

animals after acute or intermediate oral, inhalation, or dermal exposures. Other organophosphate ester 

hydraulic fluids have not produced neurological effects in animal species. 

The variability in apparent neurotoxicity among organophosphate ester hydraulic fluids may be influenced by 

several factors, including differences in phosphate ester composition (including isomeric composition), 

differences in species’ sensitivity to OPIDN, and the fact that the delayed neurotoxicity of certain fluids has 

only been examined in relatively insensitive species. Several Durad hydraulic fluids (Durads 300,220B, and 

550B [FMC 1990a, 1992a]) produced no signs of neurotoxicity in Sprague-Dawley rats after single gavage 
HYDRAULIC FLUIDS 195 

2. HEALTH EFFECTS
 

doses of 5,000 mg/kg, but have not been tested in other species. Rats, mice, and rabbits do not display the 

dysfunctions of OPIDN as seen in humans, cats, dogs, and chickens (Abou-Donia and Lapadula 1990; Baron 

1981), and therefore, these fluids have not been adequately tested for their ability to produce OPIDN. It should 

be noted, however, that a consistent difference in species sensitivity to organophosphate induced 

cholinesterase inhibition and cholinergic toxicity has not been generally recognized, and rats often have been 

used to examine the ability of organophosphate esters to inhibit cholinesterases (Wills 1972). In contrast to the 

previously mentioned Durads, Durad 110 produced no signs of neurotoxicity in rats after single gavage doses of 

5,000 mg/kg (FMC 1990a), but produced increased incidences of ataxia in chickens treated with 1,333 

mg/kg/day for 28 days or with 90 mg/kg/day for 90 days (FMC 1986). Cellulube 220 is another 

organophosphate ester hydraulic fluid that demonstrates that species differ in their susceptibility to OPIDN. 

Signs of delayed neuropathy were observed in goats and cows treated with 5,000 and 7,700 mg/kg doses, 

respectively, but were not observed in rats given 20,000 mg/kg (Dollahite and Pierce 1969). Rats in this study 

did not show signs of acetylcholinesterase inhibition, but rabbits given doses of > 5,000 mg/kg showed signs of 

acetylcholinesterase inhibition. Paralysis occurred in rabbits at doses; >7,500 mg/kg, but the available report did 

not clearly specify if the observed paralysis was slow in developing or developed quickly (and thus was more 

closely associated with acetylcholinesterase inhibition). 

Humans have been recognized as susceptible to the delayed neuropathy of ingested organophosphorus 

compounds since the 1930s when it was determined that an epidemic of neuropathies in the southern United 

States (“ginger jake paralysis”) was caused by the contamination of an alcoholic beverage containing an extract 

of Jamaican ginger (“ginger jake”) with tri-ortho -cresyl phosphate (TOCP) (Smith et al. 1930). This is an 

isomer of the hydraulic fluid component tricresyl phosphate. While current manufacturing processes minimize 

production of this isomer, it is possible that older organophosphate ester hydraulic fluids disposed of at waste 

sites may be contaminated with TOCP. The chicken generally is considered one of the most sensitive animal 

species to OPIDN, and neurotoxicity testing in hens is a normal practice in the safety evaluation of 

organophosphate esters used in plasticizers, hydraulic fluids, and insecticides (Johnson 1982). 

The diversity in the ability of organophosphate ester hydraulic fluids to produce OPIDN is best illustrated by 

the database for acute delayed neuropathy in chickens after oral exposure. Several organophosphate 

hydraulic fluids produced definitive OPIDN in chickens after acute gavage exposure (Cellulube 220, Durad 

MP280, and Fyrquels EHC, 150, and 220), while other fluids produced other neurological effects (Skydrol 

LD-4 and 500B-4, Reofos 65: cholinergic toxicity and spinal cord lesions without signs of delayed 

neuropathy). Another group produced no neurological effects in chickens (several U.S. military fluids 

designated as MIL-H-19457C and Pydrauls 29ELT, 50E, and 90E). Thus, a definitive conclusion that acute, 
HYDRAULIC FLUIDS 196 

2. HEALTH EFFECTS
 

intermediate, or chronic oral exposure to organophosphate ester hydraulic fluids, as a class, can produce 

neurotoxic effects cannot be drawn. There should be a concern, however, that acute, intermediate, or chronic 

oral exposure to any particular fluid demonstrated to be neurotoxic in chickens (or other animal species) also 

may produce neurological effects in humans at appropriate dosage levels. 

Diverse neurological effects have been observed in animals after acute to intermediate inhalation or dermal 

exposure to organophosphate hydraulic fluids. Observed effects from inhalation include mild transient 

lethargy in rabbits after 4-hour exposures to U.S. military fluids designated as Durad MP280 (6,190 mg/m3

) 

and Fyrquel 220 (5,750 mg/m3

) (Gaworski et al. 1986; Kinkead et al. 1992a); salivation (possibly of 

neurological origin) in rats exposed to 300 mg/m3 Skydrol 500B-4,6 hours/day for 6 or 13 weeks (Healy et 

al. 1992; Monsanto 1987a, 1987b, 1989); head droop, generalized weakness, and decreased blood 

cholinesterase in rabbits exposed to Cellulube 220 at 2,000 mg/m3

, 4 hours/day for <22 days (Carpenter et al. 

1959), delayed neuropathy in rabbits and chickens continuously exposed for 30-l 60 days to another U.S. 

military hydraulic fluid (triaryl phosphate) at 102 mg/m3

 and 23 mg/m3, respectively (Siegel et al. 1965); and 

kyphosis in rats continuously exposed to 100 mg/m3

 concentrations of Durad MP280 or Fyrquel 220 for 

90 days (McEwen and Vemot 1983). Observed effects from dermal exposure include delayed neuropathy in 

cattle after dermal treatment with the waste from reclamation of a Fyrquel hydraulic fluid (Julian et al. 1976) 

and cholinergic toxicity in rabbits following occluded dermal exposure to Cellulube 220 (Carpenter et al. 

1959). 

The range of responses noted for the different fluids, as well as the absence of inhalation or dermal data for 

many organophosphate hydraulic fluids known to be manufactured, makes it difficult to conclude whether 

inhalation or dermal exposure to organophosphate fluids, as a class, will produce neurological effects in 

humans. As with oral exposure, however, there should be a concern that dermal or inhalation exposure to any 

particular organophosphate fluid demonstrated to produce neurological effects (either cholinesteraseinhibitionassociated effects or delayed neuropathic effects) in animals may also produce neurological effects in humans at 

an appropriate dosage level. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding neurological effects in humans after 

inhalation, oral, or dermal exposure to polyalphaolefin hydraulic fluids. 

Single gavage doses (4,250-5,000 mg/kg) of several polyalphaolefin hydraulic fluids produced no signs of 

neurotoxicity in rats within 14 days of dosing (Kinkead et al. 1987b, 1985, 1992b; MacEwen and Vemot 
HYDRAULIC FLUIDS 197 

2. HEALTH EFFECTS
 

1983) or chickens within 21 days of dosing (Kinkead et al. 1985, 1992b). Several polyalphaolefin hydraulic 

fluids produced lethargy in some rabbits during 24-hour periods of exposure to occluded dermal doses of 

≈1,700 mg/kg (MacEwen and Vemot 1983). Lethargy was also observed in rats during and after 4-hour 

inhalation exposures to lethal concentrations of several polyalphaolefin hydraulic fluids ranging from 700 to 

6,430 mg/m3

 (Kinkead et al. 1987b; MacEwen and Vemot 1983). 

In general, the animal data do not provide strong evidence that acute exposures to polyalphaolefin hydraulic 

fluids produce neurological effects. No information is available regarding neurological effects after 

intermediate or chronic exposure to polyalphaolefin hydraulic fluids. 

Reproductive Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding reproductive effects in humans or animals 

after inhalation, oral, or dermal exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding reproductive effects in 

humans after inhalation, oral, or dermal exposure to organophosphate ester hydraulic fluids. 

Organophosphate ester hydraulic fluids may cause adverse reproductive effects based on observations of 

testicular atrophy in rats after continuous inhalation exposure to 101 mg/m3

 Durad MP280 for 90 days 

(MacEwen and Vemot 1983), loss of spermatic elements and degeneration in the seminiferous tubules in 

dogs given 20 subcutaneous injections of Cellulube 220 at doses ranging from 100 to 500 mg/kg/day 

(Carpenter et al. 1959), and decreased lactation and delayed estrus in cows after oral ingestion of 

Fyrquel-150-contaminated plant tissue at unspecified dose levels (Beck et al. 1977). 

Examination of reproductive organs found no histological alterations in male or female rats exposed to 

aerosol concentrations of cyclotriphosphazene ≤990 mg/m3

, 6 hours/day, 5 days/week for 21 days (Kinkead 

et al. 1989a, 1990); in male or female rats exposed to Skydrol500B-4 concentrations ≤300 mg/m3

, 

6 hours/day, 5 days/week for 13 weeks (Healy et al. 1992; Monsanto 1987a, 1987b, 1989). No gross 

alterations were observed in male or female rats continuously exposed to 100 mg/m3

 Fyrquel 220 for 90 days 

(MacEwen and Vemot 1983); in male or female rabbits and male hamsters continuously exposed to 

101 mg/m3

 Durad MP280 or 100 mg/m3 Fyrquel 220 for 90 days (MacEwen and Vemot 1983); and in male 

rabbits exposed to Cellulube 220 aerosol concentrations of 2,000 mg/m3

, l-4 hours/day, 4-5 days/week for 
HYDRAULIC FLUIDS 198 

2. HEALTH EFFECTS
 

≤26 days (Carpenter et al. 1959). There were also no gross alterations found following acute oral exposure 

of rabbits to Cellulube 220 at doses 5480 mg/kg/day (Carpenter et al. 1959) or in leghorn hens exposed to 

MLH-19457C or MLH-19457B fluids at doses ≤420 mg/kg/day for 5 days (Kinkead et al. 1989b); or 

dermal exposure of male rabbits to unspecified doses of Cellulube 220 for l-4 hours/day, 4-5 days/week for 

≤43 days (Carpenter et al. 1959); or in male or female rabbits exposed to 1,000 mg/kg dermal doses of 

cyclotriphosphazene 6 hours/day, 5 days/week for 2 1 days (Kinkead et al. 1989c, 1990). No exposurerelated 

changes in gonad weights were observed in male rats following dietary exposure to 50 mg/kg/day Pydraul 90E 

doses for 90 days (Monsanto 1979). Studies designed to assess reproductive performance in animals after 

exposure to organophosphate ester hydraulic fluids were not located. 

An organophosphate ester commonly used in hydraulic fluids, tricresyl phosphate (TCP), and tri-ortho-cresyl 

phosphate (TOCP), a possible contaminant of older formulations of TCP, have been shown to alter testicular 

morphology, testicular function, and reproductive function in rodents after oral exposure (Carlton et al. 1987; 

Chapin et al. 1988; NTP 1994; Somkuti et al. 1987a, 1987b). 

In studies conducted by Somkuti et al. (1987a, 1987b), significant reductions in sperm density and motility, 

altered morphology (e.g., headless sperm, spermatozoa with no head hook or excessive hooks, and 

amorphous heads), and decreased relative testicular weight were observed in rats given oral doses of TOCP. The 

effects were dose- and duration-related. No sperm effects were observed in rats exposed to 

150 mg/kg/day for 3 or 7 days, but longer exposure resulted in decreased sperm count (≥10 days) and 

motility (≥14 days) (Somkuti et al. 1987b). In rats exposed to doses >50 mg/kg/day TOCP for 63 days, 

sperm had altered morphology and no motility, and relative testicular weight was decreased, compared with 

controls (Somkuti et al. 1987a). In addition to these effects, degeneration and necrosis of the seminiferous 

epithelium were observed in rats exposed to ≥100 mg/kg/day TOCP for 14 days (Somkuti et al. 1987a) and 

disorganization of testicular germ cells and the presence of hematoxylin-positive “droplets” in the tubule 

lumena were observed in rats exposed for 63 days to ≥25 mg/kg/day TOCP (Somkuti et al. 1987a). No 

evidence of seminiferous tubule regeneration or re-initiation of spermatogenesis was observed 98 days after 

termination of the 21 -day exposure period (Somkuti et al. 1987b). 

No changes in testicular testosterone concentrations were observed in rats exposed to 150 mg/kg/day TOCP for 

3-21 days or 100 mg/kg/day for 63 days. Significant decreases in testicular nonspecific esterase (NSE) activity 

and neurotoxic esterase (NTE) activity were observed in rats exposed to ≥10 and ≥50 mg/kg/day, respectively, 

for 63 days (Somkuti et al. 1987a). Testicular activities of nonspecific esterase and neurotoxic 
HYDRAULIC FLUIDS 199 

2. HEALTH EFFECTS 

esterase were also inhibited in rats exposed to 150 mg/kg for >3 days. No changes in testicular 

ß-glucuronidase (Serotoli cell-specific enzyme) or serum luteinizing hormone, follicle stimulating hormone, 

or testosterone levels were observed (Somkuti et al. 1987b). 

In contrast to TOCP, exposure of rats to tri-para-cresyl phosphate (TPCP) for 63 days, at oral doses of 

100 mg/kg/day, did not significantly alter (compared with controls) the frequency of sperm with abnormal 

morphology, relative testis weight, sperm motility, sperm density, or testicular activities of NSE (also known 

as butyrylcholinesterase) and NTE (Somkuti et al. 1987a). Acetylcholinesterase activity was not detected in 

testicular homogenates (either controls or treated) in these studies (Somkuti et al. 1987a). The negative data for 

TPCP, coupled with the positive data for TOCP, suggest that the testicular toxicity of TOCP may involve 

inhibition of esterases in the testis. Molecular details of this potential involvement, however, are unknown, as 

are the physiological functions of NSE and NTE. Light and electron microscopic studies of rats during exposure 

to TOCP have identified the Sertoli cell as the first cell type that is structurally altered in the testis (Somkuti et 

al. 1991). Studies with Sertoli cells in culture showed that exposure for 24 hours to saligenin cyclic-ortho-tolyl 

phosphate (the TOCP metabolite thought to be responsible for TOCP delayed neuropathy), but not TOCP, 

produced a dose-related decrease in NSE activity (NTE activity was not measured in these studies) (Chapin et 

al. 1991). Several other TOCP metabolites did not decrease NSE activity in cultured Sertoli cells (Chapin et al. 

1991). The presence of TOCP in the culture medium of rat Sertoli cells produced diminished NSE activities only 

when the cells were co-cultured with Leydig cells (Chapin et al. 1990). These results have led to the hypothesis 

that the in viva metabolic conversion of TOCP to saligenin cyclic-orthotolyl phosphate in the testis may occur in 

Leydig cells. 

Sperm alterations have also been observed in rats receiving repeated gavage doses of a mixture of TCP 

isomers (containing < 9% TOCP). Decreased sperm motility, concentration, and velocity were observed in 

rats receiving 200 mg/kg/day TCP in corn oil for 66 days (Carlton et al. 1987). These effects were not 

observed in the vehicle-control or 100 mg/kg/day groups. A dose-dependent increase in abnormal sperm 

morphology was observed in the 100 and 200 mg/kg/day groups. In the 200 mg/kg/day group, there was a 

significant reduction in epididymal weights. Significant increases in minimal-to-mild seminiferous tubule 

necrosis and degeneration, hypospermia in the epididymides, degenerate and immature spermatids in 

seminiferous tubules and epididymides, and early sperm granulomas in the seminiferous tubules were 

observed in the 200 mg/kg/day males. Reproductive effects were also observed in female rats exposed to 

TCP. A dose-dependent diffuse vacuolar cytoplasmic alteration of ovarian interstitial cells and an impression 

of increased follicular and luteal activity (as indicated by increased numbers of follicles and corpora lutea) 
HYDRAULIC FLUIDS 200 

2. HEALTH EFFECTS
 

were observed in female rats receiving daily gavage doses of 200 or 400 mg/kg/day TCP (Carlton et al. 

1987). 

A mixed isomer preparation of TCP (containing <0.1% tri-ortho-cresyl phosphate) produced histological 

changes in reproductive organs in both sexes of rats and female mice in 13-week and 2-year bioassays (NTP 

1994). Ovarian interstitial cell hypertrophy occurred in female mice and female rats exposed to gavage doses of 

50-800 mg/kg/day for 13 weeks, in female rats exposed to dietary doses of 65 and 120 ng/kg/day for 13 weeks, 

and in female rats exposed to dietary doses of 9 or 18 mg/kg/day for 2 years (NTP 1994). Atrophy of the 

seminiferous tubules occurred in male rats that received gavage doses of 400 and 800 mg/kg/day for 13 weeks 

and in male rats exposed to dietary doses of 470 and 940 mg/kg/day for 13 weeks (NTP 1994). 

Reproductive performance has also been assessed in animals exposed to mixed isomers of TCP. Male rats 

were gavaged daily with 100 or 200 mg/kg/day TCP (containing <9% TOCP) during a 56-day premating and 

10-day mating period. The males were mated with female rats exposed to TCP 14-days prior to mating, 

during the 10-day mating, 21 -day gestation, and 21 -day lactation periods. Males exposed to 100 mg/kg/day 

were mated with females exposed to 200 mg/kg/day, and 200 mg/kg/day males were mated with 

400 mg/kg/day females. No difference in numbers of sperm-positive females was observed. However, 

significant decreases in the number of females delivering live young, litter size, and pup viability were 

observed in the high-dose group (Carlton et al. 1987). 

No changes in the fertility index (number of dams producing a litter per number of breeding pairs) were 

observed in mice exposed to 0, 62.5, 124, or 250 mg/kg/day TCP (containing <0.1% TOCP) in the diet for 

98 days in a continuing breeding experiment (Chapin et al. 1988). However, a significant increase in the 

number of dead pups and decrease in the number of live pups were observed in the 250 mg/kg/day group. A 

significant increase in the number of dead pups was also observed in the last two litters of mice exposed to 124 

mg/kg/day. The last litters from the 0, 62.5, and 124 mg/kg/day groups were fed TCP from weaning 

to day 74 of age. At this point, they were mated. Significant trends toward decreased mating and fertility 

indices and number of live pups per litter were observed. In the 124 mg/kg/day group, the fertility index and 

proportion of live pups per litter were significantly lower than in the control group. Sperm-motility was 

significantly decreased in both TCP-exposed groups, and no change in epididymal sperm concentration or 

histological alterations in reproductive organs were observed. 
HYDRAULIC FLUIDS 201 

2. HEALTH EFFECTS
 

To further assess the reproductive toxicity of TCP, a cross-over fertility test was performed (Chapin et al. 

1988). Control males were mated to females exposed to 250 mg/kg/day, and males exposed to 

250 mg/kg/day were mated with control females. The number of live pups per litter was significantly 

decreased in both groups of exposed mice. The reproductive performance was more severely affected in the 

exposed females mated with control males. No treatment related changes were observed in the prostate, seminal 

vesicles, ovaries, uterus, or vagina. In mice exposed to 250 mg/kg/day, atrophy of the seminiferous tubules was 

seen in the testes, and significant decreases in testicular and epididymal weights were observed. Significant 

decreases in the percentage of motile sperm, sperm concentration, and the percentage of abnormal sperm were 

observed in the 250 mg/kg/day group. Latendresse et al. (1994b) reported decreased numbers of litters in rats 

exposed by gavage to 600, 1,000, and 1,700 mg/kg/day butylated triphenyl phosphate. In the same study, 

abnormal estrous cycles and decreased uterine weights were noted in female rats exposed to 1,000 mg/kg/day 

butylated triphenyl phosphate. 

An in vitro study demonstrated decreased testosterone output by Leydig cells with addition of TOCP (Chapin et 

al. 1990), and suggested that the TOCP metabolite, saligenin cyclic-o-tolyl phosphate, may be the responsible 

agent for eliciting this effect. 

Only three (Durad MP280, Cellulube 220, and Fyrquel 150) of nine hydraulic fluids that have been studied in 

animals produced reproductive effects. It is difficult to generalize about the ability of organophosphate ester 

hydraulic fluids, as a class, to cause reproductive effects in humans because of the inadequacies of the database. 

There are no human data. Examinations of reproductive organs in animals after exposure have been conducted 

for only nine organophosphate hydraulic fluids. In addition, reproductive performance has not been evaluated 

following exposure of animals to organophosphate ester hydraulic fluids. Nevertheless, the limited data suggest 

that some hydraulic fluids in this class may produce reproductive effects, while other may not. For example, 

Durad MP280 produced testicular atrophy in rats via inhalation exposure, but Fyrquel 220 did not (MacEwen 

and Vemot 1983). Tri-ortho-cresyl phosphate and mixed isomer preparations of TCP can be found in hydraulic 

fluids and are demonstrated reproductive toxicants in animals. In general, the limited data suggest that exposure 

to certain organophosphate ester hydraulic fluids, especially those containing TCP isomers, may present a 

reproductive hazard to public health at some undetermined dosage level. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding reproductive effects in humans or 

animals after inhalation, oral, or dermal exposure to polyalphaolefin hydraulic fluids. 
HYDRAULIC FLUIDS 202 

2. HEALTH EFFECTS 

Developmental Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding developmental effects in humans or 

animals after inhalation, oral, or dermal exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding developmental effects in 

humans after inhalation, oral, or dermal exposure to organophosphate ester hydraulic fluids. 

Data concerning developmental toxicity in animals are very limited, and are at best suggestive that elicitation of 

developmental effects by some organophosphate ester hydraulic fluids may occur in some animals. The 

developmental toxicity data are too sparse to make any conclusions regarding their relevance to human health. 

Data that are suggestive of adverse developmental effects in animals after an assumed acute oral exposure to an 

organophosphate ester hydraulic fluid are restricted to an observation in cows of retarded growth in calves of 

cows with reduced lactation, and abnormal growth in one calf of a cow that showed moderate ataxia, after the 

cows ingested grass probably contaminated with components of Fyrquel 150 (Beck et al. 1977). 

None of the calves of 10 cows were adversely affected after the cows were acutely dermally exposed to an 

unknown quantity of a Fyrquel hydraulic fluid reclamation waste that probably contained TOCP and other 

hydraulic fluid components and was applied liberally to their backs once (Julian et al. 1976). 

Dibutyl phenyl phosphate, a component of some organophosphate ester hydraulic fluids, decreased the 

postnatal survival of rat pups. Decreased survival to day 4 was observed in the F1a pups (first litter) of rats 

exposed to 50 or 250 mg/kg/day and F1b pups (second litter) of rats exposed to 5 or 50 mg/kg/day (but not to 250 

mg/kg/day). The number of live offspring at weaning was also diminished in the F1a pups in 50 and 

250 mg/kg/day groups and F2 pups of the 250 mg/kg/day group. In an attempt to determine if the reduced 

survival was due to in utero effects, the F1b pups of the 250 mg/kg/day pups were cross-fostered with control 

pups. Reduced survival at day 4 and weaning was observed in the control pups raised by the high-dose rats. 

Decreased body weight gains were observed in the F0 dams (parental) exposed to 250 mg/kg/day and F1 dams 

exposed to 50 and 250 mg/kg/day. Effects on control pups, potentially exposed via treated dams are equivocal. 

Although survival was reduced, the cause is not clear (Healy et al. 1991). 
HYDRAULIC FLUIDS 203 

2. HEALTH EFFECTS
 

Additionally, no changes were seen in the type or incidence of developmental anomalies observed in the pups of 

male and female rats that had been orally exposed to triphenyl phosphate, another component of some 

organophosphate ester hydraulic fluids at doses <690 mg/kg/day for 91 days, including through mating and 

gestation (Welsh et al. 1987). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding developmental effects in humans or 

animals after inhalation, oral, or dermal exposure to polyalphaolefin hydraulic fluids. 

Genotoxic Effects. 

Mineral Oil Hydraulic Fluids. No studies were located regarding genotoxic effects in humans or animals after 

inhalation, oral, or dermal exposure to mineral oil hydraulic fluids. No information was located 

regarding the genotoxicity of mineral oil hydraulic fluids in in vitro assays. 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding genotoxic effects in humans after 

inhalation, oral, or dermal exposure to organophosphate ester hydraulic fluids. 

No studies were located regarding genotoxic effects in animals after inhalation or dermal exposure to 

organophosphate ester hydraulic fluids. However, the incidence of nuclear anomalies in bone marrow 

interphase cells was significantly increased in Chinese hamsters gavaged on 2 consecutive days with 2,500 

and 5,000 mg/kg/day of Reofos 50 (Ciba-Geigy 1984a), but not in those dosed with 1,250 mg/kg/day. 

Oral doses of ≤5,000 mg/kg Reofos 50 or Reolube HYD46 to male and female Chinese hamsters did not 

induce significant increases in sister chromatid exchanges in bone marrow cells (Ciba-Geigy 1983b, 1984b). 

No results indicating genotoxicity were observed in in vitro studies that examined six organophosphate ester 

hydraulic fluids for gene mutation, deoxyribonucleic acid (DNA) damage, or chromosomal aberrations in 

eukaryotes (see summarized data in Table 2-l 1). 

No mutagenic activity was observed in Ames assays of the prokaryote Salmonella typhimurium either with 

or without activation systems when exposed to concentrations of Durad 550B ≤10,000 mg/plate (FMC 

1992b), Reofos 95 at concentrations ≤162 μg/plate (Ciba-Geigy 1978a), Reofos 50 at concentrations 

≤162 μg/plate (Ciba-Geigy 1978b), or Reolube HYD46 at concentrations ≤5,120 μg/plate (Ciba-Geigy 

HYDRAULIC FLUIDS 205 

2. HEALTH EFFECTS
 

1983a). Tricresyl phosphate, a component of some hydraulic fluids, was not mutagenic in S. typhimurium 

strains TAlOO, TA1535, TA1537, or TA98 (NTP 1994) (see Table 2-l 1). 

DNA-repair assays of rat hepatocytes treated with Reolube HYD46 at concentrations < 150 nL/mL (CibaGeigy 1984c) or Reofos 50 at concentrations <75 nL/mL (Ciba-Geigy 1984d) were negative. Assays that 

examined Chinese hamster ovary cells for chromosomal aberrations (with or without activation systems) were 

negative after in vitro exposure to Skydrol 500B-4 or Skydrol LD-4 at concentrations ≤95 μg/mL (Monsanto 

1988a, 1988b). Tricresyl phosphate did not induce chromosomal aberrations or sister chromatid exchanges in 

Chinese hamster ovary cells (NTP 1994). 

The studies indicate low genotoxic potential in five of six organophosphate ester hydraulic fluids, and the 

data that suggest genotoxic potential in Reofos 50 appear to be equivocal. The incidence of nuclear 

anomalies was reportedly increased in bone marrow interphase cells of Chinese hamsters after acute oral 

exposure to Reofos 50 (Ciba-Geigy 1984a). However, the incidence of sister chromatid exchanges in bone 

marrow cells of Chinese hamsters after oral exposure to the same oral dose levels of Reofos 50 

(≤5,000 mg/kg by gavage) did not differ from the incidence observed in controls (Ciba-Geigy 1984b). The 

negative in vitro genotoxicity results of an Ames assay with S. typhimurium (Ciba-Geigy 1978b) and a 

DNA-repair assay with rat hepatocytes (Ciba-Geigy 1984d) further suggest that Reofos 50 is a very weak 

genotoxin if it is genotoxic at all. 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding genotoxic effects in humans or 

animals after inhalation, oral, or dermal exposure to polyalphaolefin hydraulic fluids. No information was 

located regarding the genotoxicity of polyalphaolefin hydraulic fluids in in vitro assays. 

Cancer. The Department of Health and Human Services (DHHS), the International Agency for Research 

on Cancer (IARC), and EPA have not classified mineral oil hydraulic fluids, polyalphaolefin hydraulic fluids, 

and organophosphate ester hydraulic fluids for carcinogenic effects. 

Mineral Oil Hydraulic Fluids. No associations between occupational exposure to mineral oil hydraulic 

fluids and cancer occurrence in particular organs were found in a case-control study of cancer patients after 

adjustment for gasoline exposure (Siemiatycki et al. 1987a). No other studies were located regarding cancer 

in humans or animals after inhalation, oral, or dermal exposure to mineral oil hydraulic fluids. The available 

animal and human data are inadequate to ascertain the human carcinogenicity of mineral oil hydraulic fluids. 
HYDRAULIC FLUIDS 206 

2. HEALTH EFFECTS
 

There is evidence, as reviewed by IARC (1984), that certain types of mineral oils are carcinogenic in animals 

and other mineral oils are not carcinogenic. The carcinogenic activity of mineral oils is thought to be 

dependent upon the initial processing of the crude petroleum and the nature and concentration of additives. 

Thus, highly refined oils like white mineral oil do not appear to be carcinogenic, but carcinogenic responses 

have been observed in animals exposed to untreated vacuum distillates of petroleum and mildly solventrefined 

or mildly hydro treated oils (IARC 1984). In addition, carcinogenic responses have been observed in animals 

exposed to used gasoline engine oils (IARC 1984). The available data for mineral oils as a class are not adequate 

to predict whether a particular mineral oil hydraulic fluid will be carcinogenic because of the dependence of 

carcinogenic activity upon quality of the oil, the presence of additives, and potentially, the conditions of use 

(IARC 1984). 

Organophosphate Ester Hydraulic Fluids. No studies were located regarding cancer in humans or animals 

after inhalation, oral, or dermal exposure to organophosphate ester hydraulic fluids. In 2-year feed studies, 

carcinogenic responses to tricresyl phosphate, a common fire-retardant, organophosphate ester hydraulic fluid 

additive, were not found in male or female Fischer 344 rats exposed to daily doses <20 mg/kg/day or in male or 

female B6C3F1, mice at doses <45 mg/kg/day (NTP 1994). Dietary administration of tributyl phosphate was 

associated with transitional and squamous cell carcinomas of the bladder in rats after 2 years of exposure at 

143.3 mg/kg/day (FMC 1994a). An increased incidence of hepatocellular adenomas in the liver was observed in 

mice after dietary administration of 455 mg/kg/day tributyl phosphate for 18 months (FMC 1994b). 

Polyalphaolefin Hydraulic Fluids. No studies were located regarding cancer in humans or animals after 

inhalation, oral, or dermal exposure to polyalphaolefin hydraulic fluids. 

2.6 BIOMARKERS OF EXPOSURE AND EFFECT 

Biomarkers are broadly defined as indicators signaling events in biologic systems or samples. They have 

been classified as markers of exposure, markers of effect, and markers of susceptibility (NAS/NRC 1989). 

Due to a nascent understanding of the use and interpretation of biomarkers, implementation of biomarkers as 

tools of exposure in the general population is very limited. A biomarker of exposure is a xenobiotic 

substance or its metabolite(s), or the product of an interaction between a xenobiotic agent and some target 

molecule(s) or cell(s) that is measured within a compartment of an organism (NRC 1989). The preferred 
HYDRAULIC FLUIDS 207 

2. HEALTH EFFECTS 

biomarkers of exposure are generally the substance itself or substance-specific metabolites in readily 

obtainable body fluid(s) or excreta. However, several factors can confound the use and interpretation of 

biomarkers of exposure. The body burden of a substance may be the result of exposures from more than one 

source. The substance being measured may be a metabolite of another xenobiotic substance (e.g., high urinary 

levels of phenol can result from exposure to several different aromatic compounds). Depending on the properties 

of the substance (e.g., biologic half-life) and environmental conditions (e.g., duration and route of exposure), the 

substance and all of its metabolites may have left the body by the time samples can be taken. It may be difficult 

to identify individuals exposed to hazardous substances that are commonly found in body tissues and fluids 

(e.g., essential mineral nutrients such as copper, zinc, and selenium). Biomarkers of exposure to hydraulic fluids 

are discussed in Section 2.6.1. Biomarkers of effect are defined as any measurable biochemical, physiologic, or 

other alteration within an organism that, depending on magnitude, can be recognized as an established or 

potential health impairment or disease (NAS/NRC 1989). This definition encompasses biochemical or cellular 

signals of tissue dysfunction (e.g., increased liver enzyme activity or pathologic changes in female genital 

epithelial cells), as well as physiologic signs of dysfunction such as increased blood pressure or decreased lung 

capacity. Note that these markers are not often substance specific. They also may not be directly adverse, but 

can indicate potential health impairment (e.g., DNA adducts). Biomarkers of effects caused by hydraulic fluids 

are discussed in Section 2.6.2. 

A biomarker of susceptibility is an indicator of an inherent or acquired limitation of an organism’s ability to 

respond to the challenge of exposure to a specific xenobiotic substance. It can be an intrinsic genetic or other 

characteristic or a preexisting disease that results in an increase in absorbed dose, a decrease in the 

biologically effective dose, or a target tissue response. If biomarkers of susceptibility exist, they are 

discussed in Section 2.8, Populations That Are Unusually Susceptible. 

2.6.1 Biomarkers Used to Identify or Quantify Exposure to Hydraulic Fluids 

Mineral Oil Hydraulic Fluid. Limited studies were located that suggest biomarkers of exposure to 

mineral oil hydraulic fluids. No data that indicate quantitative or qualitative biomarkers of exposure to 

mineral oil hydraulic fluid were located. Mineral oil (hydrocarbons containing ≈15-30 carbon atoms per 

molecule) is a major component that is common to all mineral oil hydraulic fluids. Following exposure to 

food-grade mineral oil, most of the administered radioactivity was excreted in the feces as mineral oil (Ebert 
HYDRAULIC FLUIDS 208 

2. HEALTH EFFECTS
 

et al. 1966). Although the presence of mineral oil is a biomarker of exposure to mineral oil hydraulic fluids, 

it is also a biomarker of exposure to other readily available products that contain mineral oils. 

Organophosphate Ester Hydraulic Fluid. Analyses of blood or urine for the presence of 

organophosphates or their metabolites can be valuable in confirming exposure to organophosphate ester 

hydraulic fluids; however, sample collections must be completed during or shortly after exposure unless 

exposure levels are very high. Urinary excretion of metabolites can be completed within a few days of 

exposure, depending on the level of exposure. 

The inhibition of two cholinesterase activities in blood can also be used to confirm exposure to certain 

organophosphate ester compounds. Red blood cell acetylcholinesterase is the same cholinesterase found in the 

gray matter of the central nervous system and motor endplates of sympathetic ganglia. Synonyms for this 

enzyme include specific cholinesterase, true cholinesterase, and E-type cholinesterase. Plasma cholinesterase is 

a distinct enzyme found in intestinal mucosa, liver, plasma, and white matter of the central nervous system. 

Synonyms for this enzyme include nonspecific cholinesterase, pseudocholinesterase, butyrylcholinesterase, and 

S-type cholinesterase (Evans 1986). Nonspecific cholinesterase is thought to be a very poor indicator of 

neurotoxic effects. 

A third enzyme may have limited potential as a measure of exposure. Neurotoxic esterase, also known as 

neuropathy target esterase (NTE), is inhibited by certain organophosphate esters. When brain NTE is 

inhibited above 70% for acute or possibly as low as 50% for repeated exposures, there is a consensus that 

delayed neuropathy is likely. NTE also is found in lymphocytes and platelets (Lotti et al. 1984). The 

measurement of lymphocytic NTE or platelet NTE has been proposed as a surrogate for brain NTE (Lotti et 

al. 1984; Maroni and Bleeker 1986). Monitoring lymphocyte NTE in agricultural workers exposed to 

organophosphate insecticides for inhibition of lymphocyte NTE, however, has not been widely employed 

because of a number of practical limitations, including the instability of the enzyme in blood and the 

possibility that lymphocyte proliferation, in response to infection, may influence activity measurements 

(Mutch et al. 1992). 

Measurement of inhibition of blood cholinesterases requires estimation of baseline values because “normal” 

values vary widely among individuals due to genetic, age, sex, and disease-related variance (Coye et al. 1986; 

Shanor et al. 1961). In the absence of baseline values for an individual, a consistent increase in activity with 

time after cessation of exposure can be used to confirm exposure (Evans et al. 1986). Plasma cholinesterase 
HYDRAULIC FLUIDS 209 

2. HEALTH EFFECTS
 

activity is more labile than red blood cell acetylcholinesterase, can be depressed by hepatic disease, infection, 

alcohol consumption, and pregnancy, and is often more sensitive to inhibition by organophosphates than is 

acetylcholinesterase (Trundle and Morcial 1988). Plasma cholinesterase is produced in the liver and can be 

rapidly regenerated. Red blood cell acetylcholinesterase activity can be depressed by hemolytic anemia. It 

should be noted that organophosphate insecticides and carbamate insecticides inhibit both types of blood 

cholinesterase. Thus, inhibition of red cell cholinesterase alone is not sufficiently diagnostic to ascertain 

exposure to organophosphate ester hydraulic fluids, per se. 

Decreased levels of erythrocyte acetylcholinesterase and/or plasma butyrylcholinesterase, brain neurotoxic 

esterase, or clinical signs of cholinesterase inhibition have been observed in animals exposed to Cellulube 

220 (Carpenter et al. 1956; Dollahite and Pierce 1969), Skydrol500B-4 (Healy et al. 1992; Monsanto 

1987d), Skydrol LD-4 (Monsanto 1987c), Fyrquel EHC (Stauffer Chemical Co. 198 l), Fyrquel220 

(Gaworski et al. 1986; Kinkead et al. 1992a), Fyrquel 150 (Beck et al. 1977), Durad MP280 (Gaworski et al. 

1986; Kinkead et al. 1992d), and Durad 125 (FMC 1991). There are insufficient data to establish an 

exposure-response relationship for cholinesterase inhibition for the individual hydraulic fluids in this class. 

Polyalphaolefin Hydraulic Fluid. Data were insufficient to indicate biomarkers of exposure to 

polyalphaolefin hydraulic fluids. 

2.6.2 Biomarkers Used to Characterize Effects Caused by Hydraulic Fluids 

Mineral Oil Hydraulic Fluid. Data were insufficient to indicate biomarkers of effects caused by mineral oil 

hydraulic fluids. 

Organophosphate Ester Hydraulic Fluid. The most widely examined target of organophosphate 

ester hydraulic fluids is the nervous system. Two types of neurological effects have been observed following 

exposure to certain organophosphate ester hydraulic fluids: cholinergic symptoms associated with 

acetylcholinesterase inhibition and delayed neuropathy (OPIDN). 

Inhibition of cholinesterase activity in red blood cells (erythrocyte acetylcholinesterase) provides a biomarker 

for cholinergic toxic effects caused by organophosphate esters in hydraulic fluids. As stated previously, 

baseline levels of this enzyme for an individual must be known in order to use inhibition as a biomarker of 

effect because “normal” values vary widely among humans (Coye et al. 1986; Evans 1986). Cholinesterase 
HYDRAULIC FLUIDS 210 

2. HEALTH EFFECTS
 

activities in agricultural workers chronically exposed to organophosphate and carbamate insecticides are 

routinely monitored in the United States to prevent development of cholinergic toxic effects. In general, the 

inhibition of erythrocyte acetylcholinesterase has been shown to correlate with the appearance of cholinergic 

symptoms such as salivation, diarrhea, altered heart rate and rhythm, respiratory depression, dizziness, and 

confusion (Coye et al. 1986). However, the rate of decline in enzyme activity is taken as a better indicator of 

the development of overt effects than is the absolute level of inhibition. Cholinergic symptoms may not 

develop in chronically exposed workers with 70-80% inhibition, but may develop in individuals without prior 

exposure after sudden exposure and a rapid decrease in cholinesterase activities of <30% (Coye et al. 1986). 

Inhibition of red blood cell acetylcholinesterase is generally taken to be a better indicator of effect than plasma 

cholinesterase, because acetylcholinesterase is the same enzyme as that found in nervous tissue, and inhibition 

of plasma cholinesterase sometimes has not correlated with the appearance of cholinergic symptoms (Coye et al. 

1986; Peedicayil et al. 1991). 

Cholinergic effects have been observed in animals exposed to Cellulube 220 (Carpenter et al. 1956; Dollahite 

and Pierce 1969), Skydrol 500B-4 (Healy et al. 1992; Monsanto 1987d), Skydrol LD-4 (Monsanto 1987c), 

Fyrquel EHC (Stauffer Chemical Co. 1981 ), Fyrquel220 (Gaworski et al. 1986; Kinkead et al. 1992a), Fyrquel 

150 (Beck et al. 1977), Durad MP280 (Gaworski et al. 1986; Kinkead et al. 1992d), and Durad 125 (FMC 

1991). In many cases, whole blood cholinesterase activity was measured instead of erythrocyte 

acetylcholinesterase in these studies. Thus, there are insufficient data to establish a relationship between severity 

of effects and percent inhibition of blood cholinesterase activity for the organophosphate ester hydraulic fluids. 

In other words, plasma cholinesterase inhibition is a biomarker of exposure, but not of effect. 

Organophosphate-induced delayed neurotoxicity (OPIDN) is a slowly developing axonal degeneration and 

demyelination in central and peripheral nerve tissues. The initial symptoms occur 8-14 days or longer after 

exposure to organophosphate (Ecobichon 1991; Johnson 1975; Murphy 1986) and can occur after a single 

exposure. Inhibition of brain neurotoxic esterase (NTE) has been proposed as a biomarker for OPIDN 

(Ecobichon 1991). The measurement of lymphocytic NTE or platelet NTE has been proposed as a surrogate 

for brain NTE (Lotti et al. 1984; Maroni and Bleeker 1986). Monitoring lymphocyte NTE in-agricultural 

workers exposed to organophosphate insecticides for inhibition of lymphocyte NTE, however, has not been 

widely employed because of a number of practical limitations, including the instability of the enzyme in blood 

and the possibility that lymphocyte proliferation, in response to infection, may influence activity 

measurements (Mutch et al. 1992). Acetylcholinesterase in nerve tissue is not thought to be directly involved 

in OPIDN because of a lack of correlation between acetylcholinesterase inhibition and potency as a OPIDN 
HYDRAULIC FLUIDS 211 

2. HEALTH EFFECTS
 

agent (Johnson 1975, 1990; Murphy 1986). OPIDN has been observed in animals exposed to unspecified 

triaryl phosphate hydraulic fluid (Siegel et al. 1965), Cellulube 220 (Carpenter et al. 1959; Dollahite and 

Pierce 1969), Fyrquel EHC (Mortensen and Ladefoged 1992; Stauffer 1980), Durad MP280 (Gaworski et al. 

1986), and Reofos 65 (Mortensen and Ladefoged 1992). 

Polyalphaolefin Hydraulic Fluid. Data were insufficient to indicate biomarkers of exposure to 

polyalphaolefin hydraulic fluids. 

For more information on biomarkers for renal and hepatic effects of chemicals see ATSDRKDC 

Subcommittee Report on Biological Indicators of Organ Damage (1990) and for information on biomarkers 

for neurological effects see OTA (1990). 

2.7 INTERACTIONS WITH OTHER CHEMICALS 

No studies were located regarding interactions of mineral oil hydraulic fluids, organophosphate ester 

hydraulic fluids, or polyalphaolefin hydraulic fluids with other substances. 

However, there are some data on interactions of phosphate esters with other compounds. Cocaine undergoes 

metabolism by three major routes; one of these routes involves hydrolysis by liver and plasma cholinesterases to 

form ecgonine methyl ester. It has been suggested that cocaine users with serious complications tend to have 

lower plasma cholinesterase levels. Thus, it is possible that individuals with decreased plasma cholinesterase 

levels (such as resulting from organophosphate ester exposure) may be highly sensitive to cocaine (Cregler and 

Mark 1986; Hoffman et al. 1992). However, there are no experimental data to support this hypothesis. 

A potentiation of neuropathy has been observed in studies involving administration of n-hexane or methyl 

n-butyl ketone with O-ethyl-O-4-nitrophenyl phenylphosphonothioate (EPN) (Abou-Donia 1983; AbouDonia et al. 1985). Administration of each compound individually resulted in peripheral neuropathy. The 

peripheral neuropathy observed when n-hexane or methyl n-butyl ketone was administered simultaneously 

with EPN was more severe and had an earlier onset (Abou-Donia et al. 1985). The potential interactive effect of 

multiple exposures to different organophosphorus pesticides on delayed neuropathy has not been 

characterized (Chemiack 1988). 
HYDRAULIC FLUIDS 212 

2. HEALTH EFFECTS 

2.8 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE 

A susceptible population will exhibit a different or enhanced response to hydraulic fluids than will most 

persons exposed to the same level of hydraulic fluids in the environment. Reasons may include genetic 

makeup, developmental stage, age, health and nutritional status (including dietary habits that may increase 

susceptibility, such as inconsistent diets or nutritional deficiencies), and substance exposure history 

(including smoking). These parameters may result in decreased function ofthe detoxification and excretory 

processes (mainly hepatic, renal, and respiratory) or the pre-existing compromised function of target organs 

(including effects or clearance rates and any resulting end-product metabolites). For these reasons we expect the 

elderly with declining organ function and the youngest of the population with immature and developing organs 

will generally be more vulnerable to toxic substances than healthy adults. Populations who are at greater risk 

due to their unusually high exposure are discussed in Section 5.6, Populations With Potentially High Exposure. 

No information was located regarding populations that may be unusually susceptible to toxic effects 

produced by mineral oil hydraulic fluids or polyalphaolefin hydraulic fluids. 

Incomplete development of acetylcholinesterase systems and an immature liver may make infants (under 

6 months) unusually susceptible to the cholinergic symptoms of organophosphate ester hydraulic fluids 

(Echobichon 1991; Evans 1986). This is supported by the Beck et al. (1977) study in cows (2 calves and 

>20 adults). A single oral exposure to Fyrquel 150 resulted in severe cholinergic effects, and the calves died 

after 13 days. Cows administered the same dose of Fyrquel exhibited equally severe cholinergic symptoms; 

however, the symptoms began to abate within 2 days, and lethality was not observed. Although the young 

appear to be more susceptible to the cholinergic symptoms of phosphate esters, they may be less sensitive to the 

delayed neuropathy (Abou-Donia and Lapadula 1990). Studies in chickens and rats have shown that 

neuropathic sensitivity gradually increases with age (Abou-Donia and Lapadula 1990; Johnson and Barnes 

1970). 

People with impaired liver function would be unusually susceptible to organophosphate ester exposure 

because of an impaired ability to metabolize organophosphate esters absorbed by the body. This population 

would primarily be composed of people suffering from liver diseases. Some groups have lower levels of 

plasma cholinesterase than the general population and are more susceptible to drugs such as succinylcholine 

which are metabolized by this enzyme. Some organophosphate esters can bind stoichiometrically to this 
HYDRAULIC FLUIDS 213 

2. HEALTH EFFECTS 

enzyme and inhibit its activity, possibly reducing plasma cholinesterase activity to a level where 

administration of succinylcholine would be dangerous. Low plasma cholinesterase levels have been seen in 

individuals with inherited abnormally low cholinesterase levels, long-distance runners, women during early 

pregnancy or using birth control pills, and individuals with advanced liver disease, chronic alcoholism, or 

malnutrition (Echobichon 1991; Evans 1986). 

2.9 METHODS FOR REDUCING TOXIC EFFECTS 

This section will describe clinical practice and research concerning methods for reducing toxic effects of 

exposure to hydraulic fluids. However, because some of the treatments discussed may be experimental and 

unproven, this section should not be used as a guide for treatment of exposures to hydraulic fluids. When 

specific exposures have occurred, poison control centers and medical toxicologists should be consulted for 

medical advice. 

Studies designed to examine methods for reducing toxic effects of mineral oil, organophosphate ester, and 

polyalghaolefin hydraulic fluids in humans or animals were not located. Most hydraulic fluids are mixtures 

comprised of major and minor components whose presence may or may not be public information. Adverse 

health effects from exposure to mixtures can be caused by potent components which may represent only 

minor portions of the whole mixture and whose presence may not be common knowledge. This section 

discusses available information on methods for reducing toxic effects of major components of these classes of 

hydraulic fluids or of materials that may be expected to display similar toxicity and/or toxicokinetic 

properties. It should be noted that methods for reducing the toxic effects of the major component of the 

hydraulic fluid may not prevent the manifestations of toxic effects because the toxicity of the hydraulic fluid 

may be due to a minor component (such as organophosphate ester additives in mineral oil hydraulic fluids). 

Because the composition of a particular hydraulic fluid may vary greatly from other hydraulic fluids in the 

same class, it is suggested that health professionals attempt to obtain a label containing a list of all 

components of the hydraulic fluid of concern. Mineral oil hydraulic fluids frequently have organophosphate 

ester additives, so that in some cases-particularly in interfering with mechanism of action-the same 

strategies as for organophosphate esters might be applicable. 
HYDRAULIC FLUIDS 214 

2. HEALTH EFFECTS 

2.9.1 Reducing Peak Absorption Following Exposure 

Mineral Oil Hydraulic Fluids. Mineral oil hydraulic fluids are expected to be poorly absorbed by the 

gastrointestinal tract (see Section 2.3). Although specific recommendations for treatment of acute 

intoxication from ingested mineral oil hydraulic fluids were not located, the removal of ingested 

petroleumderived hydrocarbons by intubation with a cuffed endotracheal tube followed by lavage has been 

suggested for cases where the patient is unconscious (Klein and Simon 1986). Warnings against the induction of 

vomiting have been made, because of the hazard of aspiration of the ingested fluids (Eade et al. 1974; Klein and 

Simon 1986). Food-grade or medicinal mineral oil (containing mostly aliphatic hydrocarbons) has cathartic 

properties (Brunton 1985). Administration of other cathartic agents (i.e., sorbitol) may result in a faster 

excretion rate, thus reducing gastrointestinal effects that may result from mineral oil hydraulic fluids passing 

through the gastrointestinal tract. 

There is no available information on absorption of mineral oil hydraulic fluids following inhalation or dermal 

absorption. There are data suggesting that mineral oil aerosols are cleared from the lungs via alveolar 

macrophages. No specific methods to reduce absorption of dermally applied or inhaled mineral oil hydraulic 

fluids were located, but it is expected that removal of contaminated clothing and multiple washings of 

contaminated skin would reduce the dermal absorption of these materials. 

Organophosphate Ester Hydraulic Fluids. Major components of organophosphate ester hydraulic fluids 

such as tricresyl phosphate isomers, isopropylated phenyl phosphates, and tributyl phosphate are readily 

absorbed through the gastrointestinal tract. These phosphate esters are slowly absorbed by the skin. No data on 

the absorption of inhaled tricresyl phosphate, isopropylated phenyl phosphate, or tributyl phosphate were 

located. No specific methods were located to reduce absorption of inhaled, ingested, or dermally applied 

organophosphate ester hydraulic fluids. Recommendations for the clinical treatment of organophosphorus 

insecticide poisonings, however, are likely applicable to poisonings with organophosphate ester hydraulic fluids. 

Recommended decontamination procedures to reduce absorption have included removal of contaminated 

clothing, washing of skin with alkaline soap that will remove and hydrolyze the-phosphate ester, washing of 

eyes with water or saline, and lavage of the stomach (Murphy 1986). 

Polyalphaolefin Hydraulic Fluids. There is no information on the absorption of polyalphaolefin hydraulic 

fluids. Based on the physicochemical similarities between polyalphaolefins and mineral oils, it is likely that 

gastrointestinal absorption will be limited. No specific methods were located to reduce absorption of inhaled, 
HYDRAULIC FLUIDS 215 

2. HEALTH EFFECTS
 

ingested, or dermally applied polyalphaolefin hydraulic fluids. Because certain polyalphaolefins are irritants 

following inhalation and dermal exposure (Kinkead et al. 1987b, 1992b; MacEwen and Vemot 1983) and the 

hazard of aspiration of the ingested fluids, it is questionable whether the induction of vomiting upon ingestion 

should be recommended as a method to reduce absorption. As with mineral oil hydraulic fluids, it is expected 

that removal of contaminated clothing and multiple washings of contaminated skin would reduce the dermal 

absorption of polyalphaolefin hydraulic fluids. 

2.9.2 Reducing Body Burden 

No specific methods were located to reduce the body burden of absorbed mineral oil hydraulic fluids, 

organophosphate ester hydraulic fluids, or polyalphaolefin hydraulic fluids. 

Absorbed hydrocarbons from mineral oil are likely to be preferentially distributed to the liver and fatty tissues 

and slowly metabolized to various types of lipids. Polyalphaolefins are expected to be similarly distributed 

and retained based on the similarities of the physical and chemical properties of polyalphaolefins and mineral 

oil. 

Tricresyl phosphate isomers, a major component of some organophosphate ester hydraulic fluids, are widely 

distributed throughout the body with preferential uptake in fatty tissues, liver, and kidneys. The isomers are 

readily cleared without displaying a tendency to accumulate in tissues. 

2.9.3 Interfering with the Mechanism of Action for Toxic Effects 

Mineral Oil Hydraulic Fluids. No specific methods were located for interfering with the mechanism of 

action for toxic effects produced by mineral oil hydraulic fluids. Unstable alveoli and distal airways have 

been proposed as major factors in the respiratory symptoms that occur after the ingestion of other 

petroleumderived materials. Continuous positive airway pressure or continuous negative chest wall pressure, as 

well as the application of supplemental oxygen, have been recommended to counteract the resultant pneumonitis 

(Eade et al. 1974; Klein and Simon 1986). 

Organophosphate Ester Hydraulic Fluids. Recommended procedures for interfering with the cholinergic 

toxic effects produced by organophosphoms insecticide poisonings are likely applicable to poisoning with 

organophosphate ester hydraulic fluids. Recommended treatments have included various regimens of 
HYDRAULIC FLUIDS 216 

2. HEALTH EFFECTS
 

artificial respiration (if needed), atropine intravenous administration (to control muscarinic responses), and 

2-pyridine aldoxime methiodide intravenous administration (to accelerate reactivation of phosphorylated 

acetylcholinesterase) (Ecobichon 1991; Murphy 1986). Administration of 2-pyridine aldoxime methiodide 

should be accomplished as soon as possible, but within 48 hours of organophosphate exposure (Ecobichon 

1991). After this time, the phosphorylated acetylcholinesterase may become “aged” (i.e., irreversibly 

phosphorylated), and thus impossible to reactivate. The interference of the cholinergic toxicity of 

organophosphate esters is not necessarily expected to interfere with the development of organophosphateinduced delayed neurotoxicity (Ecobichon 1991). No methods to interfere with the development of OPIDN were 

located. It should be noted, however, that by the time symptoms of OPIDN appear, organophosphorus 

compounds and metabolites may have been cleared from the body (see Section 2.3). 

Use of the muscle relaxant succinylcholine, which is metabolized by plasma cholinesterase, is contraindicated in 

cases of organophosphate poisoning (Giurini et al. 1986). 

Polyalphaolefin Hydraulic Fluids. No specific methods were located for interfering with the mechanism of 

action for toxic effects produced by polyalphaolefin hydraulic fluids. 

2.10 ADEQUACY OF THE DATABASE 

Section 104(I)(5) of CERCLA, as amended, directs the Administrator of ATSDR (in consultation with the 

Administrator of EPA and agencies and programs of the Public Health Service) to assess whether adequate 

information on the health effects of hydraulic fluids is available. Where adequate information is not 

available, ATSDR, in conjunction with the National Toxicology Program (NTP), is required to assure the 

initiation of a program of research designed to determine the health effects (and techniques for developing 

methods to determine such health effects) of hydraulic fluids. 

The following categories of possible data needs have been identified by a joint team of scientists from 

ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that if met would 

reduce the uncertainties of human health assessment. This definition should not be interpreted to mean that 

all data needs discussed in this section must be filled. In the future, the identified data needs will be evaluated 

and prioritized, and a substance-specific research agenda will be proposed. 
 

HYDRAULIC FLUIDS 217 

2. HEALTH EFFECTS 

2.10.1 Existing Information on Health Effects of Hydraulic Fluids 

The existing data on health effects of inhalation, oral, and dermal exposure of humans and animals from 

hydraulic fluids are summarized in Figures 2-8,2-9, and 2-10. The purpose of these figures is to illustrate 

the existing information concerning the health effects of hydraulic fluids. Each dot in the figure indicates that 

one or more studies provide information associated with that particular effect. The dot does not necessarily 

imply anything about the quality of the study or studies, nor should missing information in this figure be 

interpreted as a “data need.” A data need, as defined in ATSDR’s Decision Guide for Identifying SubstanceSpecific Data Needs Related to Toxicological Profiles (ATSDR 1989), is substance-specific information 

necessary to conduct comprehensive public health assessments. Generally, ATSDR defines a data gap more 

broadly as any substance-specific information missing from the scientific literature. 

Mineral Oil Hydraulic Fluids. There is limited information on the toxicity of mineral oil hydraulic 

fluids in humans. A single case report of a child accidentally ingesting a single dose of automotive 

transmission fluid provides limited information on death and systemic effects. A case-control study provides 

some information on the carcinogenicity of mineral oil hydraulic fluids. The study population was exposed 

via inhalation and dermal routes. An occupational exposure study provides information on neurotoxicity 

following chronic dermal exposure. Information on the toxicity of mineral oil hydraulic fluids is limited to a 

series of inhalation, oral, and dermal acute-duration exposures. These studies provide information on death, 

systemic effects, and neurotoxicity by inhalation, oral, and dermal routes, and immunotoxicity following 

dermal exposure. 

Organophosphate Ester Hydraulic Fluids. Information on human toxicity of organophosphate ester 

hydraulic fluids is very limited. Accidental poisonings (oral exposure) account for the majority of studies, 

though occupational exposure and dermal exposure is also reported. In animals, a number of 

organophosphate ester hydraulic fluids have been studied following inhalation exposure. These inhalation 

studies provide information on death, acute and intermediate systemic effects, possible information on 

immunotoxicity, neurotoxicity, and reproductive toxicity. Information on death, acute-, intermediate-, and 

chronic-duration systemic effects, immunological and lymphoreticular toxicity, neurotoxicity, reproductive 

toxicity, developmental toxicity, genotoxicity and cancer is available from oral exposure studies. Dermal 

exposure studies provide information on death, acute- and intermediate-duration systemic effects, 

immunotoxicity, neurotoxicity, reproductive toxicity, and developmental toxicity. 



HYDRAULIC FLUIDS 221 

2. HEALTH EFFECTS
 

No information was located on the toxicity of organophosphate ester hydraulic fluid breakdown products. 

Since these products may occur in the environment after disposal of organophosphate ester hydraulic fluids, 

this represents a potential data need in all categories. 

Polyalphaolefin Hydraulic Fluids. No information on the toxicity of polyalphaolefin hydraulic fluids 

to humans was located. 

A series of acute- and intermediate-duration inhalation, oral, and dermal exposure studies in animals provide 

information on death, systemic effects, neurological effects, and immunotoxicity following exposure to 

polyalphaolefin hydraulic fluids. 

2.10.2 Identification of Data Needs 

Acute-Duration Exposure. 

Mineral Oil Hydraulic Fluids. There is limited information on the acute toxicity of mineral oil hydraulic 

fluids to humans. A single case report of a child accidentally ingesting automotive transmission fluid 

reported respiratory and gastrointestinal effects (Perrot and Palmer 1992). 

There is also limited animal data. A series of acute inhalation, oral, and dermal lethality studies monitored 

death and body weight gain in rats exposed to Sunsafe F, Quintolubric 9583OW, Houghto-Safe 5047F, or 

Pyroguard A-443 mineral oil hydraulic fluids (Kinkead et al. 1988, 1989a) or mineral oil hydraulic fluids 

meeting military specifications of MIL-H-5606 (Kinkead et al. 1985). The dermal and ocular irritancy of 

these fluids has also been tested (Kinkead et al. 1985, 1988, 1989a). These lethality studies are not adequate for 

the derivation of acute inhalation or oral MRLs. No acute-duration studies performing complete 

histopathological examinations or repeated exposure studies that identify target organs were located. These 

studies would be useful in determining the health risks of individuals acutely exposed to mineral oil hydraulic 

fluids. 

Organophosphate Ester Hydraulic Fluids. Human studies of exposure to organophosphates are primarily 

those of acute, accidental poisonings with tricresyl phosphate (Goldstein et al. 1988; Senayanake and 

Jeyaratnam 1981; Srivastava et al. 1990). 
HYDRAULIC FLUIDS 222 

2. HEALTH EFFECTS
 

In rats, studies of the acute toxicity of inhaled Durad MP280 and Fyrquel 220 (Gaworski et al. 1986), 

examined respiratory, hepatic, and renal end points and found no effects. In rabbits, acute inhalation 

exposure to Cellulube 220 caused respiratory and gastrointestinal problems (Carpenter et al. 1959). Mice 

and rabbits exhibited acute neurotoxicity with exposure to triphenyl phosphate and Cellulube 220 (Carpenter 

et al. 1959; Sutton et al. 1960). Acute-duration oral exposure studies were located for rats, mice, guinea pigs, 

rabbits, hens, goats, and cows exposed to Durad 220B (FMC 1990a), Durad 550B (FMC 1992a), Durad 110 

(FMC 1990a), Durad 300 (FMC 1990a), Cellulube 220 (Dollahite and Pierce 1969; Carpenter et al. 1959), 

Reofos 65 (Mortensen and Ladefoged 1992), Pydraul 50E (Ciba-Geigy 1973), Fyrquel EHC (Mortensen and 

Ladefoged 1992), Fyrquel 220 (FMC 1977a), Skydrol 500B-4 (Monsanto 1987d), Skydrol LD-4 (Monsanto 

1987c), Fyrquel 150 (Beck et al. 1977), ethylhexyldiphenyl phosphate (Noda et al. 1984), butylated triphenyl 

phosphate (Latendresse et al. 1994), dibutylphenyl phosphate (Carrington et al. 1989), isopropyltriphenyl 

phosphate (Sprague et al. 1984), Santicizer 141048 (Robinson et al. 1986), tributoxyethyl phosphate (Carrington 

et al. 1989), triphenyl phosphate (Sutton et al. 1960), and tributyl phosphate (Healy et al. 1995; Johannsen et al. 

1977). 

Neurotoxic end points, especially acetylcholinesterase and related enzymes, were the most heavily studied, 

but other studies have expanded the toxicity literature to include developmental, immunological, and systemic 

effects. The acute dermal toxicity of Fyrquel 220 and Durad MP280 (Gaworski et al. 1986; Kinkead et al. 

1992a, 1992d, 1992e), Durad 220B, Durad 110, and Durad 300 (FMC 1990a), Durad 125 (FMC 1991b), 

cyclotriphosphazene (Kinkead et al. 1992c; MacEwen and Vemot 1985), and Durad 550B (FMC 1992c) has 

been tested in rats and rabbits. These studies were designed to examine dermal and/or ocular irritancy or to 

assess neurotoxicity. Because the inhalation and oral exposure studies examined a limited number of end points, 

MRLs could not be derived. EPA has been negotiating an Enforceable Consent Agreement with the 

manufacturers of aryl phosphates and in reviewing the needs for testing, acute testing is not identified (EPA 

1994). 

Polyalphaolefin Hydraulic Fluids. No acute exposure human studies were located. 

There is limited information on the acute toxicity of polyalphaolefin hydraulic fluids to animals. Several 

single 4-hour exposure studies identified the respiratory tract as a target of toxicity following exposure to 

polyalphaolefin hydraulic fluids designated as B85-174 (Kinkead et al. 1987b), MIL-H-83282LT (Kinkead et 

al. 1992b), or DTNSRDC N501 (MacEwen and Vemot 1983). Acute inhalation, oral, and dermal lethality 

studies on polyalphaolefin hydraulic fluids designated as DTNSRDC N448, N501, N5 17, N5 18, N525, or 
HYDRAULIC FLUIDS 223 

2. HEALTH EFFECTS
 

N527 (MacEwen and Vemot 1983) or a polyalphaolefin hydraulic fluid meeting military specifications of 

MIL-H-83282 (Kinkead et al. 1985) provide evidence that polyalphaolefin hydraulic fluids were not very 

lethal and did not affect body weight gain. Dermal and ocular irritancy were also assessed using 

polyalphaolefin hydraulic fluids designated as DTNSRDC N448, N501, N5 17, N5 18, N525, or N527 

(MacEwen and Vemot 1983), MIL-H-83282LT (Kinkead et al. 1992b), B85-174 (Kinkead et al. 1987b), or 

meeting military specifications of MIL-H-83282 (Kinkead et al. 1985). The DTNSRDC N501 was a mild 

skin irritant and MIL-H-83282LT was a eye irritant. Based on these animal data, the targets of toxicity of 

polyalphaolefin hydraulic fluids cannot be identified. Repeated exposure and studies conducting complete 

histological examinations would be useful in assessing the risk of individuals exposed to polyalphaolefin 

hydraulic fluids for acute durations. 

Intermediate-Duration Exposure. 

Mineral Oil Hydraulic Fluids. No intermediate exposure human studies were located. 

Two studies on intermediate-duration exposure to mineral oil hydraulic fluids are available: a single oral 

exposure rat study to MIL-H-5606 (Mattie et al. 1993), and an inhalation-exposure study in rats to HoughtoSafe 5047F (Kinkead et el. 1991). Because no other intermediate-duration studies were located, no inhalation or 

oral intermediate MRLs were derived. Inhalation, oral, and dermal systemic toxicity studies examining a 

number of end points would be useful in identifying the targets of toxicity of mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. Four human exposure studies were located. In one study, no 

change in hematological parameters was observed in workers dermally exposed to organophosphate ester 

hydraulic fluids for an intermediate duration (Baldridge et al. 1959). The application of patches containing 

Skydrol500B-4 resulted in erythema in individuals exposed for an intermediate duration (Monsanto 1980). 

A woman developed an allergic reaction to triphenyl phosphate found in the frames of her glasses (Carlson et al. 

1986) and a man also became hypersensitive to organophosphates found in a glue he was using (Camaras and 

Serra-Baldrich 1992). 

The toxicity of inhaled triaryl phosphates (triaryl phosphate-mixture), Fyrquel 220, Durad MP280, and 

cyclotriphosphazene has been well studied in rats, rabbits, and hamsters. These studies suggest that Fyrquel 220 

(Gaworski et al. 1986; MacEwen and Vemot 1983), Durad MP280 (Gaworski et al. 1986; MacEwen and Vemot 

1983), cyclotriphosphazene (Kinkead et al. 1989a, 1990), and Cellulube 220 (Carpenter et al. 
HYDRAULIC FLUIDS 224 

2. HEALTH EFFECTS
 

1959; Siegel et al. 1965) are not potent systemic toxicants. No further inhalation exposure studies are needed for 

these organophosphate ester hydraulic fluids. Although there is a reasonable body of data for 

intermediate oral exposure to organophosphate esters, EPA and the aryl phosphate industry are planning 

additional testing (EPA 1994). The National Toxicology study, published in 1994, has helped to define oral, 

systemic end points for exposure to tricresyl phosphate. Adrenal, liver and body weight changes are reported in 

rats and mice. Endocrine effects are further delineated for rats exposed to TCP and butylated triphenyl 

phosphate (Latendresse et al. 1994a, 1994b; Oishi et al. 1982). Following exposure to low doses of Pydraul 90E, 

no evidence of systemic toxicity was observed in rats (Monsanto 1979) and no changes in body weight gain 

were observed in hens exposed to Durad 110 (FMC 1986). As a broad range of systemic end points become 

defined, it would be useful to have additional testing of systemic effects. A number of studies on 

organophosphorus ester hydraulic fluids suggest that neurological effects may be the most sensitive end point of 

toxicity. Because of limitations in the neurotoxicity database, inhalation and oral intermediate-duration MRLs 

were not derived. Information is available on the intermediate-duration dermal toxicity in rabbits of 

cyclotriphosphazene (Kinkead et al. 1989c, 1990), Fyrquel220 (MacEwen and Vemot 1983), and Cellulube 220 

(Carpenter et al. 1959). No further systemic toxicity studies on the dermal toxicity of cyclotriphosphazene and 

Fyrquel 220 are needed. (Cellulube 220 is no longer in production.) Studies on other organophosphate ester 

hydraulic fluid components might be useful for assessing the potential for human toxicity following 

intermediate-duration exposure. 

Polyalphaolefin Hydraulic Fluids. No intermediate exposure human studies were located. 

Information on polyalphaolefin hydraulic fluids is limited to a single study in rats orally exposed to MIL-H83282 and MIL-H-83282LT (Mattie et al. 1993). Intermediate-duration inhalation or oral MRLs could not 

be derived based on a single study. Significant toxicity was not observed. Systemic toxicity studies in which 

animals were exposed via inhalation and dermal routes would be useful in identifying the end points of 

toxicity for humans living at or near hazardous waste sites and exposed for intermediate-durations. 

Chronic-Duration Exposure and Cancer. 

Mineral Oil Hydraulic Fluids. No human or animal studies involving inhalation, oral, or dermal 

chronicduration exposure were located. Because no chronic-duration studies were located, no inhalation or oral 

chronic MRLs were derived. Inhalation, oral, and dermal systemic toxicity studies examining a number of end 

points would be useful in identifying the targets of toxicity of mineral oil hydraulic fluids. 
HYDRAULIC FLUIDS 225 

2. HEALTH EFFECTS
 

One human carcinogenicity exposure study was located. This study did not find convincing associations 

between exposure to hydraulic fluid and the incidence of cancer at a specific site (Siemiatycki et al. 1987a). 

As discussed in Section 2.2.1.8, there are a number of limitations to this study. An animal carcinogenicity 

study or well-controlled cohort retrospective or prospective study would be useful for determining the 

carcinogenic potential of mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No chronic exposure human studies were located. 

Chronic animal studies of organophosphates are few in number, but those that do exist provide a useful base 

from which to draw toxicological insight. In rats and mice exposed orally to tricresyl phosphate for 2 years, 

endocrine effects were found in a dose-response pattern and hepatic effects were found. Ovarian interstitial 

hyperplasia was also observed but was not dose related. No chronic-duration MRLs could be derived because of 

the limited number of studies. Tricresyl phosphate, a component of certain hydraulic fluids, produced no 

evidence of carcinogenic activity in assays with rats and mice (NTP 1994). However, another component, 

tributyl phosphate, was associated with an increased incidence of bladder tumors in rats and mice (FMC 1994a, 

1994b). 

Polyalphaolefin Hydraulic Fluids. Because no chronic-duration human or animal inhalation, oral, or 

dermal exposure studies using polyalphaolefin hydraulic fluids were located, chronic-duration inhalation or 

oral MRLs could not be derived. Systemic toxicity studies in which animals were exposed via inhalation, 

oral, and dermal routes would be useful in identifying the end points of toxicity for humans living at or near 

hazardous waste sites and exposed for chronic durations. Further carcinogenicity studies on individual 

organophosphate ester components of hydraulic fluids may be useful. 

No information on the carcinogenic potential of polyalphaolefin hydraulic fluids was located. Studies 

designed to assess carcinogenicity in animals exposed via inhalation, oral, and dermal routes or a well controlled 

cohort retrospective or prospective study would be useful for determining the carcinogenic 

potential of polyalphaolefin hydraulic fluids. 

Genotoxicity. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. No studies were located regarding 

genotoxicity after inhalation, oral, or dermal exposure to mineral oil hydraulic fluids or polyalphaolefin. 
HYDRAULIC FLUIDS 226 

2. HEALTH EFFECTS 

hydraulic fluids. No studies were located regarding genotoxicity of mineral oil hydraulic fluids or 

polyalphaolefin hydraulic fluids in in vitro assays. Studies that address the genotoxicity of members of these 

classes of hydraulic fluids would be helpful. 

Organophosphate Ester Hydraulic Fluids. In vivo genotoxicity assays have been conducted for two 

organophosphate ester hydraulic fluids. Results have generally been negative. The in vivo genotoxicity of 

Reofos 50 and Reolube HYD46 has been tested in Chinese hamsters (Ciba-Geigy 1983b, 1984a, 1984b). 

Durad 550B (FMC 1992b), Reofos 95 (Ciba-Geigy 1978a), Reolube HYD46 (Ciba-Geigy 1983a, 1984a), 

Reofos 50 (Ciba-Geigy 1978b, 1984b), Skydrol500B-4 (Monsanto 1988a), and Skydrol LD-4 (Monsanto 

1988b) have been tested for in vitro genotoxicity using gene mutation, DNA damage, and/or chromosomal 

aberrations. In EPA’s Notice of Proposed Test Rule for aryl phosphates there is no mention of genotoxic 

testing (EPA 1992), nor is there an identified need for genotoxic testing in the 1994 EPA Testing Consent 

Order (EPA 1994). 

Reproductive Toxicity. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. No studies were located regarding 

reproductive toxicity after exposure by any route to mineral oil or polyalphaolefin hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. Rats and mice were tested with oral exposure to certain 

components of organophosphate ester hydraulic fluids, generally for subchronic periods, and effects were 

reported for both males and females. Females showed ovarian interstitial hypertrophy, increased ovarian 

weights, and decreased fertility after exposure to tricresyl phosphate (Latendresse et al. 1994a, 1994b; NTP 

1994). Males exhibited abnormal sperm, necrosis of seminiferous tubules, and reduced testes weights after 

exposure to tricresyl phosphate (Carlton et al. 1987; Latendresse et al. 1994a, 1994b; NTP 1994). 

Reproductive toxicity is an area of concern, and further reproductive toxicity testing on individual 

components of organophosphate ester hydraulic fluids would be useful. 

Developmental Toxicity. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. The developmental toxicity data 

base is generally inadequate. No studies were located regarding developmental toxicity after exposure by any 

route to mineral oil hydraulic fluids or polyalphaolefin hydraulic fluids. 
HYDRAULIC FLUIDS 227 

2. HEALTH EFFECTS
 

Organophosphate Ester Hydraulic Fluids. No studies concerning developmental effects of organophosphate 

ester hydraulic fluids in humans were located; among the limited number of studies that report organophosphate 

ester developmental toxicity are reports of reduced litter size, pup survivability and pup weights in rats with 

tricresyl phosphate and dibutyl phenyl phosphate (Carlton et al. 1987; Healy et al. 1991). Teratogenicity was not 

observed. The database also has two observations of developmental effects in cows that were probably 

environmentally exposed to organophosphate ester hydraulic fluids (Beck et al. 1977; Julian et al. 1976). Further 

developmental toxicity testing may be warranted. 

Immunotoxicity. 

Mineral Oil Hydraulic Fluids. No information was located regarding immunological effects in humans 

after inhalation, oral, or dermal exposure to mineral oil hydraulic fluids. Data from animal testing of limited 

immunological end points suggest that the immunological system may not be a sensitive target for certain 

mineral oil hydraulic fluids. In guinea pig skin sensitization assays, four of five tested mineral oil hydraulic 

fluids were inactive as skin sensitization agents, and the remaining fluid only showed weak activity (Kinkead 

et al. 1985, 1987a, 1988). Testing of other mineral oil hydraulic fluids using an immunological test battery in 

animals by several routes of exposure would help to determine if the immunologic system is a target of 

mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No dermal sensitization reactions were observed in a study of 

human subjects exposed dermally to Skydrol 500B-4 (Monsanto 1980) or in a study of guinea pigs exposed 

to a cyclotriphosphazene-based hydraulic fluid (Kinkead et al. 1992c; MacEwen and Vemot 1985). Two case 

reports indicate dermal sensitization from eyeglass frames and glue (Carlsen et al. 1986; Camarasa and SerraBaldrich 1992). No histological alterations were observed in the thymus of rats exposed to aerosols of 

cyclotriphosphazene for 21 days (Kinkead et al. 1989a, 1990). Thymus weight decreases (both absolute and 

relative to body weight) were observed, without histological alterations, in rabbits exposed dermally to 

cyclotriphosphazene (Kinkead et al. 1989c, 1990). Additional testing of other organophosphate ester hydraulic 

fluids would provide support for the hypothesis suggested by the limited available data that skin sensitization 

may not be a concern with dermal exposure to organophosphate ester hydraulic fluids. Testing of other 

organophosphate ester hydraulic fluids for additional immunological end points in animals would help to 

determine if the immunologic system is a target of these materials. 
HYDRAULIC FLUIDS 228 

2. HEALTH EFFECTS
 

Polyalphaolefin Hydraulic Fluids. No data were located regarding immunological effects in humans after 

exposure to polyalphaolefin hydraulic fluids. Results from guinea pig skin sensitization assays indicated that 

two of nine tested polyalphaolefin hydraulic fluids were skin sensitizers (Kinkead et al. 1985, 1992b; 

MacEwen and Vemot 1983). Data from oral administration is limited to histological examination of 

immunological tissues where no effect was found (Mattie et al. 1993). Examination of additional 

immunological end points in animals after oral, inhalation, and dermal exposure to polyalphaolefin hydraulic 

fluids would help to determine the likelihood of immunologic effects occurring in humans exposed to 

environmental media contaminated with these materials. 

Neurotoxicity. 

Mineral Oil Hydraulic Fluids. Reports of neurological effects in humans or animals are restricted to a 

single case report of neuropathy in a man who was heavily exposed to mineral oil hydraulic fluids by 

occupational dermal contact (Jarvholm et al. 1986) and a report of subtle electromyographical effects in four 

of eight examined men who were less heavily exposed by occupational dermal contact (Jkvholm et al. 1986). 

However, an association between human exposure to mineral oil hydraulic fluids and neurological effects is 

uncertain, due to the lack of corroborative case reports and epidemiological data and the lack of studies 

demonstrating neurological effects in animals after exposure to mineral oil hydraulic fluids. The presence of 

organophosphate ester additives in many mineral oil hydraulic fluids raises some concern regarding 

neurotoxicity, but levels of these additives are normally low. Acute inhalation, oral or dermal testing of 

additional fluids for organophosphate-induced delayed neuropathy (OPJDN) in sensitive species (e.g., cats or 

chickens) may provide useful information to ascertain the neurological hazard presented by mineral oil 

hydraulic fluids. No information was located regarding neurological effects in humans or animals after 

intermediate to chronic exposure to mineral oil hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. Neurotoxicity is a concern from acute dermal, inhalation, or 

oral exposure to organophosphate ester hydraulic fluids because of the well-established susceptibility of 

humans to the cholinergic and delayed neuropathic properties of certain organophosphate este compounds 

such as TOCP. Sufficient acute oral testing of organophosphate hydraulic fluids in chickens has been 

conducted to conclude that there is a wide range in the ability of organophosphate ester fluids to produce 

adverse neurological effects. Certain fluids (e.g., Durad 220B and Durad 125), however, have not been tested for 

neurotoxicity in sensitive animal species. Acute testing of these additional organophosphate hydraulic fluids for 

neurotoxicity in chickens will provide useful information regarding their potential to produce acute 
HYDRAULIC FLUIDS 229 

2. HEALTH EFFECTS
 

neurological effects. Dermal or inhalation testing in cats (another sensitive species to OPIDN) may provide 

additional information regarding the hazard from these expected routes of certain occupational exposures. It 

is unknown if long-term, low-dose exposures to organophosphate ester hydraulic fluids will produce 

neurological effects. Experiments with hens, however, suggested that with longer exposure periods, lower 

doses of Durad 110 produced increased incidences of ataxia and nerve damage. A LOAEL of 

1,333 mg/kg/day was observed with a 2%day oral exposure, compared with a LOAEL of 90 mg/kg/day with 

90 days of exposure (FMC 1986). Additional animal experiments with other organophosphate ester 

hydraulic fluids are needed to assess the neurological hazard presented by intermediate to chronic exposure. 

Polyalphaolefin Hydraulic Fluids. Several polyalphaolefin hydraulic fluids have been tested for clinical 

signs of OPIDN in chickens after acute gavage exposure, but adverse effects were not seen (Kinkead et al. 

1985, 1992b). As with mineral oil hydraulic fluids, the possible presence of organophosphate ester additives 

in these fluids may raise some concern regarding neurotoxicity, but levels would normally be expected to be 

low. Acute oral or dermal testing of additional fluids for OPIDN in sensitive species may be useful to further 

ascertain the neurological hazard presented by polyalphaolefin hydraulic fluids. No information was located 

regarding neurological effects in humans or animals after intermediate to chronic exposure to polyalphaolefin 

hydraulic fluids. 

Epidemiological and Human Dosimetry Studies. 

Mineral Oil Hydraulic Fluids. Two human studies involving exposure to mineral oil hydraulic fluids were 

located. One was a case report of a child who accidentally ingested a lethal dose of automotive transmission 

fluid (Perrot and Palmer 1992). The other is an occupational exposure in which workers were dermally exposed 

to mineral oil hydraulic fluids (Jarvholm et al. 1986). Both of these studies are limited because only a small 

number of end points were examined and there is no accurate reporting of dose levels. Because mineral oil 

hydraulic fluids are widely used, the potential for human exposure is great. The identified human studies and the 

animal studies did not identify the primary target of toxicity for mineral oil hydraulic fluids. Epidemiology 

studies of workers (including auto mechanics exposed to transmission fluids) exposed to mineral oil hydraulic 

fluids would be useful in identifying targets of toxicity. 

Organophosphate Ester Hydraulic Fluids. Two human exposure studies were identified. In these studies, 

individuals were dermally exposed to organophosphate ester hydraulic fluids for an intermediate duration 

(Baldridge et al. 1959; Monsanto 1980). In the Baldridge et al. (1959) study, no hematological or 
HYDRAULIC FLUIDS 230 

2. HEALTH EFFECTS
 

neurological effects were observed. The Monsanto (1980) study was designed to assess dermal irritation and 

sensitization. Organophosphate ester hydraulic fluids are fire-resistant hydraulic fluids used in the hydraulic 

systems of aircraft; thus, there is a potential for occupational exposure. The animal data suggest that the most 

sensitive target of toxicity is the neurological system. Studies designed to monitor acetylcholinesterase 

inhibition, particularly in the workplace, would be useful in establishing dose-response relationships. 

Polyalphaolefin Hydraulic Fluids. No human studies for polyalphaolefin hydraulic fluids were located. 

Polyalphaolefin hydraulic fluids are used in U.S. military aircraft hydraulic systems; thus, there is a potential 

for occupational exposure. Animal studies were insufficient for determining the primary targets of toxicity. 

Epidemiology studies examining a number of end points would be useful for identifying targets of toxicity. 

Biomarkers of Exposure and Effect. 

Exposure. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. The data bases regarding the 

toxicity of mineral oil and polyalphaolefin hydraulic fluids are very limited. Further toxicity testing may 

elucidate biomarkers of exposure for these classes of hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. Interpretation of the biomarkers of exposure to organophosphate 

ester hydraulic fluids is complicated by the diversity of composition among the hydraulic fluids in this class. 

Erythrocyte acetylcholinesterase activity is a good biomarker of exposure to certain organophosphates (e.g., 

insecticides), but results are inconsistent with organophosphate components of hydraulic fluids. A biomarker of 

exposure to any component of a hydraulic fluid would serve as a biomarker of exposure to the hydraulic fluid 

itself. 

Effect. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. The data bases of the toxicity of 

mineral oil and polyalphaolefin hydraulic fluids are very limited. Further toxicity testing may elucidate 

biomarkers of effect for these classes of hydraulic fluids. 
 

HYDRAULIC FLUIDS 231 

2. HEALTH EFFECTS
 

Organophosphate Ester Hydraulic Fluids. The biomarkers of effects after exposure to organophosphate
 

ester hydraulic fluids are well established in cases of delayed neuropathy (clinical signs of peripheral
 

neuropathy). Further study would be helpful to determine whether certain effects (such as diarrhea after oral
 

exposure) are due to direct action of the toxic agent on the target organ or to inhibition of acetylcholinesterase at
 

the acetylcholine nerve receptor site on the organ.
 

Absorption, Distribution, Metabolism, and Excretion. The toxicokinetics database is inadequate.
 

Very limited data were located regarding relative rates of absorption, distribution, metabolism, and excretion
 

after exposure to mineral oil hydraulic fluids, organophosphate ester hydraulic fluids, or polyalphaolefin
 

hydraulic fluids. The extent of located pertinent data is: a study describing the in vivo absorption and
 

excretion of cyclotriphosphazene (rates were not quantified), the in vivo metabolism of Reolube HYD46 to
 

cyclic and mono-hydroxylated metabolites (rate was not quantified), and observations concerning the in vitro
 

absorption of components of Reolube HYD46 and Reofos 50 (Yang et al. 1990). There are data on the
 

toxicokinetics of some of the major components of these classes of hydraulic fluids. Data on these
 

components does not obviate the need for data on the hydraulic fluids, per se, because many of the fluids are
 

complex mixtures of chemicals that may include some components which may not share toxicokinetic
 

properties with the major components. No data were located regarding differences in absorption,
 

distribution, metabolism, or excretion with respect to time or dose.
 

Comparative Toxicokinetics. The toxicokinetics database is wholly inadequate with respect to
 

comparing toxicokinetics across species, largely because of the dearth of baseline data regarding absorption,
 

distribution, metabolism, and excretion in any species after exposure to mineral oil hydraulic fluids,
 

organophosphate ester hydraulic fluids, or polyalphaolefin hydraulic fluids. Also, no studies were located on the
 

toxicokinetic properties of hydraulic fluids in humans.
 

Methods for Reducing Toxic Effects. 

Mineral Oil Hydraulic Fluids. Aside from the possibility of the development of pneumonitis.following the 

aspiration of ingested mineral oil hydraulic fluid, little is known regarding the toxicity of these materials. 

Additional animal studies to identify the possible toxic effects of exposure to these materials may provide 

information relevant to the investigation of methods for reducing the toxic effects. 
HYDRAULIC FLUIDS 232 

2. HEALTH EFFECTS
 

Organophosphate Ester Hydraulic Fluids. There are no established methods for reducing absorption of 

organophosphate esters. Studies in animals designed to identify agents that could inhibit or delay the 

absorption of organophosphate esters may provide valuable information for the preventive treatment of acute 

neurotoxic effects produced by some organophosphate ester hydraulic fluids. The mechanism of the acute 

cholinergic toxicity of organophosphorus esters is well known, as are methods to interfere with it. 

Identification of chemicals that reactivate “irreversibly” inhibited acetylcholinesterase would be valuable in 

the treatment of acute poisoning by organophosphorus esters. In contrast, the mechanism of OPIDN is 

poorly understood. Additional studies on the mechanism of OPIDN may provide information relevant to the 

identification of chemicals that interfere with a requisite step in its development. 

Polyalphaolefin Hydraulic Fluids. Aside from the acute lethality of inhalation exposure to certain 

polyalphaolefin hydraulic fluids, little is known regarding the toxic effects produced by these materials. 

Additional animal studies to identify the possible toxic effects of exposure to these materials may provide 

information relevant to the investigation of methods for reducing the toxic effects. 

2.10.3 Ongoing Studies 

Dr. D.R. Mattie and colleagues at the Wright-Patterson Air Force Base Armstrong Laboratory are involved in 

ongoing evaluations of the comparative toxicity of various hydraulic fluids used by the U.S. Air Force. 

Results from subchronic toxicity studies with rats orally exposed to mineral oil and polyalphaolefin hydraulic 

fluids are being prepared for publication. Under the Toxic Substances Control Act, EPA and aryl phosphate 

industry representatives are negotiating a test program to cover toxicological gaps in our present knowledge 

and potential environmental exposure to aryl phosphates. The EPA has published a proposed test rule (EPA 

1992b) for testing aryl phosphate base stocks. The proposed tests include: chronic exposure neurotoxicity in 

the hen, two-generation reproduction and fertility effects, subchronic mammalian toxicity, and developmental 

toxicity. Since this proposed rule was published in January 1992, the comment period has closed, and EPA is 

considering what stocks to test, what tests to proceed with, and how to implement any testing program. 
HYDRAULIC FLUIDS 233 

3. CHEMICAL AND PHYSICAL INFORMATION 

3.1 Chemical Identity 

Information regarding the chemical identity of hydraulic fluid products is located in Table 3-l. This table 

contains information representative of three types of hydraulic fluids: mineral oil, organophosphate ester, and 

polyalphaolefin. 

Early fluid power systems used water as the hydraulic medium. Because of its corrosive effect on the metallic 

parts and lack of lubricity, water was replaced by petroleum-based oil. The petroleum-based fluids discussed in 

this profile are mineral oil and water-in-oil emulsion fluids. Water-in-oil emulsions consist of 35-40% water, 

<60% mineral oil, and emulsifiers and additives. The water is dispersed in fine droplets in the oil phase. 

However, these fluids containing oil are readily ignited (NFPA 1991). Some water-in-oil emulsion 

hydraulic fluids contain ethylene glycol; however, ethylene glycol represents <10% of the total volume of 

water-in-oil emulsion hydraulic fluids. The carbon number range in mineral oil hydraulic fluids will vary 

depending on the application, but probably is in the range of C15 to C50(IARC 1984). The hydrocarbon 

components of mineral oil (and ethylene glycol) are used in numerous other applications, so the presence of 

these components in the environment cannot be uniquely associated with mineral oil-based hydraulic fluid use. 

Most mineral oil hydraulic fluids are made from dewaxed paraffin-based crude oils that are blended with 

additives to impart appropriate properties for the specific use (Newton 1989; Papay 1989, 1991; Wills 

1980). The types of additives, which are summarized below, are quite numerous and in some cases (Mattie et al. 

1993) may contain organophosphate esters. These additives include extreme pressure additives, which help 

prevent surface damage under severe loading (organic sulfur-, phosphorus-, and chlorine-containing 

compounds); anti-wear additives, which prevent wearing under light loads (fatty acids and derivatives, 

organophosphate esters); corrosion inhibitors, which prevent corrosion by oxygen and water (fatty acids, 

sulfonates, and salts of fatty acids); oxidation inhibitors, which inhibit oxidation of the hydraulic fluid (phenols, 

amines, and sulfides); defoamers, which prevent foam formation (silicone oils); viscosity index improvers, 

which reduce the dependence of viscosity on temperature (polyalphaolefins, polymethacrylates, and 

polyalkylstyrenes); pour point depressants, which lower the pour point temperature (polymethacrylates and 

condensation products); demulsifiers, which allow separation of oil and water (ionogenic and nonionogenic 

polar compounds); and dispersants, which prevent unwanted deposits (sulfonates and amides) (Moller 1989). 





HYDRAULIC FLUIDS 239 

3. CHEMICAL AND PHYSICAL INFORMATION
 

The exact nature of each of these additives appears to be trade secret information since none of the Material 

Safety Data Sheets describing the hydraulic fluids presented in this profile identify these materials. In addition, 

no information concerning the exact production methods used in manufacturing these hydraulic 

fluids was located in the available literature. Nonetheless, they are probably manufactured in batch processes 

and then tested to insure that they conform to the specifications for which they are sold. The number, nature, and 

amount of each additive used in a batch may depend on availability, cost, or performance. 

The carbon number range (hence, viscosity) in mineral oil hydraulic fluids will vary depending on the 

application of the fluid (IARC 1984; Papay 1989, 1991, 1993; Wills 1980), but probably are in the range of 

C15 to C50. The higher the carbon number, the higher the viscosity; viscosity is a major factor in determining 

the base stock of a hydraulic fluid (Moller 1989; Papay 1989, 1991, 1993; Shubkin 1993; Wills 1980). A 

more highly refined mineral oil will have better viscosity properties (i.e., high viscosity index or low 

dependence of viscosity on temperature) (Moller 1989; Shubkin 1993). 

In the past, hydraulic fluids using mineral oils sometimes included such additives as PCBs to improve the 

thermal resistance or other properties of the resulting fluids. While such uses of PCBs have been 

discontinued, PCBs at NPL sites may be encountered as a component where hydraulic fluids are a site 

contaminant (ATSDR 1993b). 

Synthetic fire-resistant fluids have been developed to replace petroleum-based fluids for many applications. 

Although there are several types of these less hazardous fluids, the only synthetic fluids discussed in this 

profile are phosphate esters and polyalphaolefins. The phosphate esters are tertiary esters of orthophosphoric 

acid, O=P(OH)3, and may be triaryl, trialkyl, and alkyl/aryl. The polyalphaolefins are usually based on 2-decene 

and contain a mixture of oligomers (dimers, trimers, etc.). 

The first commercial trialkyl phosphate esters (TAP) were tricresyl phosphate (TCP) and trixylenyl 

phosphate (TXP), referred to as “natural” phosphate esters because the cresols and xylenols used as raw 

materials are derived from petroleum oil or coal tar (Marino and Placek 1994). These products are not 

commercially significant at present; however, at waste disposal sites, contaminants from older product 

formulations may be encountered, particularly those containing the neurotoxic tri-ortho-cresyl phosphate 

isomer. “Synthetic” phosphate esters are derived from synthetic feedstocks. Specific synthetic reactions have 

been developed to produce triaryl, trialkyl, and alkyl\aryl esters. The triaryl phosphates are currently the most 

significant commercial products (Marino 1992). All three organic groups can be the same, such as tricresyl 
HYDRAULIC FLUIDS 240 

3. CHEMICAL AND PHYSICAL INFORMATION
 

or trixylenyl phosphate, or they may be different, as iso-propylphenyl diphenyl phosphate or cresyl diphenyl 

phosphate. Of the trialkyl phosphate esters, tributyl phosphate is the most important of the synthetic base 

stocks. Most are used in aircraft hydraulic fluids (Marino 1992). Dibutyl phenyl phosphate, also used as an 

aircraft hydraulic fluid, is the most important of the alkyl/aryl phosphate esters (Marino 1992). 

Products may be either mixtures of phosphate ester compounds resulting directly from the manufacturing 

process or mixtures resulting from post-blending or compounding with additives. 

One of the main human health concerns about organophosphate esters is the potential for neurotoxicity 

reactions, in particular a condition known as organophosphate-induced delayed neurotoxicity (OPIDN). Triortho- cresyl phosphate (TOCP) has been identified as one of the more potent OPIDN neurotoxins in humans, 

and was formerly a constituent in some organophosphate ester hydraulic fluid products (Marino 1992; Marino 

and Placek 1994). Production processes now routinely remove virtually all the TOCP. For instance, tricresyl 

phosphate (TCP) products now typically are manufactured to contain over 98% meta and para isomers and 

virtually no TOCP (Marino and Placek 1994). Products containing these compounds associated with OPIDN 

have now entirely disappeared from commercial use, and the vast majority of the industrial organophosphate 

esters are based on triaryl phosphates with no halogenated components (Marino 1992). At waste disposal sites, 

however, site contaminants from older product formulations containing the ortho form may be encountered. 

In addition, organophosphate esters also are used as antiwear additives in hydraulic fluids and other 

lubricants; of the organophosphate esters discussed in this profile, Durad 110, 125, 220B, and 300 are 

categorized by their manufacturers as antiwear additives and not as hydraulic fluids (FMC 1991c, 1991d, 

1992a, 1992b; Marino and Placek 1994). 

Before the 1960s products were introduced based on alkyl aryl phosphates that could contain chlorinated 

aromatic hydrocarbons. Such products have now entirely disappeared from commercial use, and the vast 

majority of the industrial organophosphate esters are based on triaryl phosphates with no halogenated 

components (Marino 1992). However, at older waste disposal sites, hydraulic fluid site contaminants could 

contain chlorinated hydrocarbons. As with the PCBs formerly included as additives in other forms of 

hydraulic fluids, these additives may present more toxicity risks than the primary ingredients of the hydraulic 

fluids. 
HYDRAULIC FLUIDS 241 

3. CHEMICAL AND PHYSICAL INFORMATION
 

A typical polyalphaolefin oil prepared from 1-decene and BF 3· n-C4H9OH catalyst at 30 о

C contains 

predominantly trimer (C30hydrocarbons) with much smaller amounts of dimer, tetramer, pentamer, and 

hexamer. While 1 -decene is the most common starting material, other alphaolefins can be used, depending on 

the needs of the product oil. 

The final oil contains a large number of isomers (e.g., the trimer of 1 -decene contains many C30 isomers, the 

tetramer contains many C40 isomers) which result from skeletal branching during the oligomerization 

(Shubkin 1993). Polyalphaolefin oils are many times classified by their kinematic viscosity at 100 °

C; the 

higher the viscosity, the longer the average chain length of the polyalphaolefin. The isomer distribution of a 

polyalphaolefin oil used in a particular hydraulic fluid will depend on the application. A polyalphaolefin oil 

contains a narrower range of molecular weights than a comparable mineral oil (Chrisope and Landry 

1993;Shubkin 1993). 

Most hydraulic fluids contain additives that impart needed properties (Papay 1989, 1991; Wills 1980). The 

exact composition and proportion of these additives in a certain type of fluid depends on the intended use. 

Hydraulic fluids are compounded to conform to performance-based standards such as Military or ASTM 

(American Society for Testing and Materials) specifications. Some examples of Military specifications are 

shown in Table 3-2. Many different formulations can be compounded to conform to one performance 

standard. It should be noted that the variability among these products or even within products with the same 

trade names may confuse efforts to determine environmental and health effects of hydraulic fluids at 

hazardous waste landfills since hydraulic fluids that are currently used may or may not contain the same 

components present in old products of the same name. 

Table 3-3 contains information regarding the chemical identity of principal components of hydraulic fluids. 

Trade names are included when the component constitutes 100% (or nearly 100%) of the product. 

Information has also been included for several representative types of mineral oil. It should be noted, 

however, that the term “mineral oil” encompasses a wide variety of petroleum-based products. Several 

phosphate esters used as hydraulic fluid additives are also included in Table 3-3. 

Some of the products listed in the tables in Chapter 3 are not currently on the market. Information has been 

included for these products since components may be present at older waste disposal sites. For example, 

Cellulube 200 has not been a commercial product for over 20 years, Pydraul products are no longer sold 

commercially, and MIL-H- 19457B has been obsolete since 1981 (FMC 1995). In addition, some product 





HYDRAULIC FLUIDS 247 

3. CHEMICAL AND PHYSICAL INFORMATION
 

names and designations have changed. For example, Durad MP 280B is now known as a Reolube (effective 

January 1995) (FMC 1995). 

3.2 Physical and Chemical Properties 

Information regarding the physical and chemical properties of selected hydraulic fluid products is shown in 

Table 3-4. Physical and chemical properties of selected hydraulic fluid components are shown in Table 3-5. 

The physical properties important for the projected use of hydraulic fluids are viscosity, density, foaming 

behavior, and fire resistance. There is no generally recognized test method for measuring flammability of 

hydraulic fluids, although various test methods may be utilized (Moller 1989). 

Physical data important for describing environmental behavior (KOC, KOW, vapor pressure, water solubility, and 

Henry’s law constant) are incomplete. In general, hydraulic fluids have relatively low water solubilities. 

A summary of the hydraulic fluids discussed in this profile is found in Table 3-6. Data on some of the 

components of hydraulic fluids are shown in Tables 3-7 through 3-9. 

















HYDRAULIC FLUIDS 265 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 

4.1 PRODUCTION 

Background information on production for the three major categories of hydraulic fluids that are the subject 

of this profile is summarized below. Most hydraulic fluid products involve special formulations or mixtures 

marketed under specific trade names. Public agencies will seldom attempt to track production figures for 

such highly specialized product lines. In addition, many of the constituent chemicals used in hydraulic fluids 

appear in a variety of other products or applications ranging from lubricants to plasticizers. Since hydraulic 

fluids have not been viewed as the most serious forms of toxicants or site contaminants, there are as yet no 

reporting requirements for the Toxics Release Inventory (EPA 1995) for hydraulic fluids or any of the major 

chemical constituents in the three categories of hydraulic fluids discussed below or listed in Tables 3-l 

through 3-3. 

Mineral Oil Hydraulic Fluids. Most mineral oil hydraulic fluids are made from dewaxed paraffin-based 

crude oils that are blended with additives to impart appropriate properties for the specific use (Newton 1989; 

Papay 1989, 1991; Wills 1980). The types of additives, which are summarized below, are quite numerous 

and in some cases (Mattie et al. 1993) may contain organophosphate esters. These additives include extreme 

pressure additives, which help prevent surface damage under severe loading (organic sulfur-, phosphorus-, 

and chlorine-containing compounds); anti-wear additives, which prevent wearing under light loads (fatty 

acids and derivatives, organophosphate esters); corrosion inhibitors, which prevent corrosion by oxygen and 

water (fatty acids, sulfonates, and salts of fatty acids); oxidation inhibitors, which inhibit oxidation of the 

hydraulic fluid (phenols, amines, and sulfides); defoamers, which prevent foam formation (silicone oils); 

viscosity index improvers, which reduce the dependence of viscosity on temperature (polyalphaolefins, 

polymethacrylates, and polyalkylstyrenes); pour point depressants, which lower the pour point temperature 

(polymethacrylates and condensation products); demulsifiers, which allow separation of oil and water 

(ionogenic and non-ionogenic polar compounds); and dispersants, which prevent unwanted deposits 

(sulfonates and amides) (Moller 1989). The exact nature of each of these additives appears to be trade secret 

information since none of the Material Safety Data Sheets describing the hydraulic fluids presented in this 

profile identify these materials. In addition, no information concerning the exact production methods used in 

manufacturing these hydraulic fluids was located in the available literature. Nonetheless, they are probably 

manufactured in batch processes and then tested to insure that they conform to the specifications for which 
HYDRAULIC FLUIDS 266 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL
 

they are sold. The number, nature, and amount of each additive used in a batch may depend on availability, 

cost, or performance. 

The carbon number range (hence, viscosity) in mineral oil hydraulic fluids will vary depending on the 

application of the fluid (IARC 1984; Papay 1989, 1991, 1993; Wills 1980), but probably is in the range of 

C15 to C50. The higher the carbon number, the higher the viscosity; viscosity is a major factor in determining 

the base stock of a hydraulic fluid (Moller 1989; Papay 1989, 1991, 1993; Shubkin 1993; Wills 1980). A 

more highly refined mineral oil will have better viscosity properties (i.e., high viscosity index or low 

dependence of viscosity on temperature) (Moller 1989; Shubkin 1993). 

Mineral oil hydraulic fluids are not listed on the Toxics Release Inventory (TRI), so a listing of 

manufacturing sites cannot be generated from this inventory. U.S. suppliers of mineral oil hydraulic fluids 

include Amoco, Arco, Chevron, Citgo, Exxon, Mobil, Shell, Texaco, and Union (Wills 1980). Producers 

include American Lubricants Co., Amoco Oil Co., Anderson Oil & Chemical Co., Inc., Ashland Oil Co., 

Benz Oil Co., Cepsa Chempet Corp., Chevron U.S.A. Inc., Cities Service Oil Co., Continental Oil Co., 

Cooks Industrial Lubricants Inc., Drydene Co., Engineered Lubricants Co., Exxon Chemical Co., U.S.A., 

Exxon Co. U.S.A. (Esso Affiliated Co.), Exxon Research & Engineers Co., Gulf Oil Corp. & Subsidiaries, 

Interlube Corp., International Refining and Mfg. Co., Luscon Industries Corp., A. Margolis & Son Corp., 

Metal Lubricant Co., Mobil Oil Corp., Motor Oils Refining Co., Penzoil Co., Shell Co., Shultz Lubricants 

Inc., Sun Petroleum Products Co., Texaco Inc., Texaco Canada Inc., Total Compagnie Fran&se de 

Raffinage, Total Compagnie Francaise des Petroles & its Affiliates, Tower Oil & Technology Co., Valvoline 

Oil Co. (International Division), Vulcan Oil Co., and Arthur C. Withrow Co. (Wills 1980). Much of the 

publicly available information on mineral oil-based hydraulic fluid production derives from surveys 

conducted in the late 1970s so it is often difficult to determine which facilities or companies presently carry 

out significant production activities. 

No information concerning the specific production volumes of mineral oil hydraulic fluids was found in the 

available literature. The National Petroleum Refiners Association (NPRA 1992) reported that- 192 million 

gallons of automatic transmission fluids, universal tractor hydraulic/transmission fluids, energy/shock 

absorber and power steering fluids, and other automotive hydraulic fluids were sold in 1991. Virtually all of 

these fluids are mineral oil hydraulic fluids (Chrisope and Landry 1993; Papay 1989, 1991; Wills 1980). 

This volume is lower than sales volumes for 1990 (216 million gallons), 1989 (221 million gallons), 1988 

(223 million gallons), 1987 (220 million gallons), and 1986 (210 million gallons) (NPRA 1992). 
HYDRAULIC FLUIDS 267 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL
 

Water-in-oil emulsion hydraulic fluids are made from paraffin- or naphthenic-based crudes (i.e., mineral oil) 

and combined with water, bridging solvents (e.g., ethylene glycol [bridging solvents, in this case, increase the 

solubility of mineral oil in water and probably help stabilize the emulsion]), and emulsifiers (Houghton 1992; 

Quaker 1993; Wills 1980). Production methods are probably similar to those for the mineral oil hydraulic fluids. 

Suppliers include Mobil, Conoco, Shell, Sun, Houghton, Hurlburt, and Quaker (Quaker 1993; Wills 1980). 

Some water-in-oil emulsion hydraulic fluids contain ethylene glycol (Houghton 1992; Quaker 1993), which is 

subject to reporting under TRI. Nonetheless, since ethylene glycol is used in numerous other applications and 

represents 110% of the total volume of water-in-oil emulsion hydraulic fluids, it is not anticipated that 

information concerning releases on the TRI will be indicative of water-in-oil emulsion hydraulic fluid use. 

In 1991, ≈12.5 million gallons of fire resistant fluids (probably including water-in-oil emulsions) were sold; 

this is the lowest sales volume since 1985 (NPRA 1992). No detailed breakdown of water-in-oil emulsion 

hydraulic fluids was provided in NPRA (1992). 

Organophosphate Ester Hydraulic Fluids. Organophosphate esters are made by condensing an 

alcohol (aryl or alkyl) with phosphorus oxychloride in the presence of a metal catalyst (Muir 1984) to 

produce trialkyl, tri(alkyl/aryl), or triaryl phosphates. For the aryl phosphates, phenol or mixtures of 

alkylated phenols (e.g., isobutylated phenol, a mixture of several t-butylphenols) are used as the starting 

alcohols to produce potentially very complex mixtures of organophosphate esters. Some phosphate esters 

(e.g., tricresyl and trixylyl phosphates) are made from phenolic mixtures such as cresylic acid, which is a 

complex mixture of many phenolic compounds. The composition of these phenols varies with the source of 

the cresylic acid, as does the resultant phosphate ester. The phosphate esters manufactured from alkylated 

phenylated phenols are expected to have less batch-to-batch variations than the cresylic acid derived 

phosphate esters. The differences in physical properties between different manufacturers of the same 

phosphate ester are expected to be larger than batch-to-batch variations within one manufacturer. 

The synthesis of organophosphate ester compounds dates to the mid-1800s. From an early date, the most 

commercially useful compounds for lubricants, plasticizers, and hydraulic fluids were in the chemical family 

of the tertiary esters. Before 1970, products were introduced based on alkyl aryl phosphates that could 

contain chlorinated aromatic hydrocarbons. One of the main human health concerns about organophosphate 

esters is the potential for neurotoxicity reactions, in particular a condition known as organophosphate-induced 

delayed neurotoxicity (OPIDN). Tri-ortho-cresyl phosphate (TOCP) has been identified as one of the more 
HYDRAULIC FLUIDS 268 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL
 

potent OPIDN neurotoxins in humans, and was formerly a constituent in some organophosphate ester 

hydraulic fluid products (Marino 1992; Marino and Placek 1994). Production processes now routinely 

remove virtually all the TOCP. For instance, tricresyl phosphate (TCP) products now typically are 

manufactured to contain over 98% meta and para isomers and virtually no TOCP (Marino and Placek 1994). 

Products containing these compounds associated with OPIDN have now entirely disappeared from 

commercial use, and the vast majority of the industrial organophosphate esters are based on triaryl 

phosphates with no halogenated components (Marino 1992). At waste disposal sites, however, site 

contaminants from older product formulations containing the ortho form may be encountered. 

Organophosphate ester hydraulic fluids are not listed on the TRI, so a listing of manufacturing sites cannot be 

generated from this inventory. U.S. suppliers of organophosphate ester hydraulic fluids include Akzo, 

Chevron, FMC, Houghton, Mobil, and Monsanto (Akzo 1989, 1991, 1992; FMC 1991c, 1992a, 1992b, 

1992c, 1992d; Wills 1980). 

No information on recent production volumes of organophosphate esters used in hydraulic fluids was found 

in the available literature. 

Polyalphaolefin Hydraulic Fluids. Polyalphaolefins are made by oligomerizing alphaolefins such as 

1-decene in the presence of a catalyst (Newton 1989; Shubkin 1993; Wills 1980). The crude reaction 

mixture is quenched with water, hydrogenated, and distilled. The number of monomer units present in the 

product polyalphaolefin oil depends on a number of reaction parameters including the type of catalyst, 

reaction temperature, reaction time, and pressure (Shubkin 1993). The exact combination of reaction 

parameters used by a manufacturer is tailored to fit the end-use of the resulting polyalphaolefin oil. A typical 

polyalphaolefin oil prepared from 1 -decene and BF3 • n-C4,H9,OH catalyst at 30 °C contains predominantly 

trimer (C30 hydrocarbons) with much smaller amounts of dimer, tetramer, pentamer, and hexamer. While 

1 -decene is the most common starting material, other alphaolefins can be used, depending on the needs of the 

product oil. 

The final oil contains a large number of isomers (e.g., the trimer of I-decene contains many C30 isomers, the 

tetramer contains many C30 isomers) which result from skeletal branching during the oligomerization 

(Shubkin 1993). Polyalphaolefin oils are many times classified by their kinematic viscosity at 100 °C; the 

higher the viscosity, the longer the average chain length of the polyalphaolefin. The isomer distribution of a 

polyalphaolefin oil used in a particular hydraulic fluid will depend on the application. A polyalphaolefin oil 
HYDRAULIC FLUIDS 269 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL
 

contains a narrower range of molecular weights than a comparable mineral oil (Chrisope and Landry 1993; 

Shubkin 1993). 

Polyalphaolefin hydraulic fluids have many advantages over the mineral oil counterparts including low 

temperature flow characteristics, lower volatility, and oxidative stability (Chrisope and Landry 1993; 

Shubkin 1993). Certain polyalphaolefins maintain good operational characteristics and have been proposed 

for use in hydraulic systems in U.S. military aircraft (Kinkead et al. 1992b). 

U.S. manufacturers of alphaolefins include Ethyl Corp., Shell Chemical Co., Shell Oil Co., and Texaco 

Chemical Co. (USITC 1993). More than 1 billion pounds of alphaolefins were produced in 1991 (USITC 

1993), but no information concerning the volume of alphaolefins used in the production of polyalphaolefin 

hydraulic fluids was found in the available literature. 

4.2 IMPORT/EXPORT 

No information on the import/export of mineral oil hydraulic fluids, organophosphate ester hydraulic fluids, 

or polyalphaolefin hydraulic fluids was found in the available literature. 

4.3 USE 

Hydraulic fluids are a very diverse class of mixtures that are used in mechanical systems for transmitting 

pressure (Wills 1980). The choice of which hydraulic fluid class and which specific hydraulic fluid to use in a 

particular application is based on a number of factors including the type of application, environment, and 

equipment using the fluid. 

Mineral Oil Hydraulic Fluids. Mineral oil hydraulic fluids are used in numerous applications such as 

automobile automatic transmissions (hydrokinetic transmission) and power steering units, elevators, farm 

equipment (including lifting and tilting mechanisms), mining, energy, chemical manufacturing,primary 

metals, machining, and manufacturing (such as forklift trucks, loading systems, metal working machines and 

systems, hydrostatic transmissions, and work-holding systems) (Papay 1993; Wills 1980). Mineral oil-based 

hydraulic fluids constitute the largest class of hydraulic fluids and are used in a large number of industrial, 

commercial, and consumer applications. 
HYDRAULIC FLUIDS 270 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL
 

Water-in-oil emulsion hydraulic fluids are used not only in applications such as those described above, but 

also where leaking hydraulic fluid could contact an ignition source such as in mines, general industry, and 

rolling mills (Wills 1980). They are temperature sensitive and do not withstand freezing temperatures; their 

applications, therefore, are limited to environments where freezing temperatures do not exist. 

In the past, hydraulic fluids using mineral oils sometimes included such additives as PCBs to improve the 

thermal resistance or other properties of the resulting fluids. While such uses of PCBs have been 

discontinued, PCBs at NPL sites may be encountered as a component where hydraulic fluids are a site 

contaminant (ATSDR 1993b). 

Organophosphate Ester Hydraulic Fluids. Military and commercial performance needs for fire 

resistance, a wide range of operating temperatures, and improved safety in handling and storage provided the 

impetus for the development of many types of organophosphate esters as synthetic lubricant products and 

feedstocks during the 1940s and 1950s (Marino and Placek 1994). Organophosphate ester hydraulic fluids are 

used where fire retardancy is needed, such as on aircraft, in marine applications, in electrohydraulic control 

systems of steam turbines, and in industrial systems where leaking fluid might contact an ignition source (Papay 

1993; Wills 1980). In addition, organophosphate esters also are used as antiwear additives in hydraulic fluids 

and other lubricants; of the organophosphate esters discussed in this profile, Durad 110, 125, 220B, and 300 are 

categorized by their manufacturers as antiwear additives and not as hydraulic fluids (FMC 1991 c, 1991 d, 

1992a, 1992b; Marino and Placek 1994). When used as hydraulic fluids or lubricants, organophosphate esters 

act as solvents on a variety of hydrocarbon-based seals, hoses, paints, coatings, and elastomers used with 

machinery or other equipment. Without proper maintenance, leaks from seal and hose failures can lead to spills 

and releases to the environment (Marion and Placek 1994). 

Polyalphaolefin Hydraulic Fluids. Polyalphaolefin hydraulic fluids have properties comparable to the 

most effective components in mineral oil and are used in applications identical to mineral oil hydraulic fluids 

(Chrisope and Landry 1993; Papay 1993; Shubkin 1993; Wills 1980). Polyalphaolefins are more expensive 

than mineral oil, and this may limit their use in industry. In addition, polyalphaolefin hydraulic fluids are 

used in military applications such as aircraft and missile hydraulic systems, tank recoil and hydraulic systems, 

and aerospace test stands (Shubkin 1993). 
HYDRAULIC FLUIDS 271 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 

4.4 DISPOSAL 

Mineral Oil Hydraulic Fluids. Disposal of used mineral oil hydraulic fluids is regulated as used oil 

under the Solid Waste Disposal Act as amended by the Resource Conservation and Recovery Act (RCRA) 

and as amended by the Used Oil Recycling Act (42 U.S.C. 6901,6905,6935,6937-6939, and 6074, see 40 

CFR parts 260,261,266,271, and 279). Used mineral oil hydraulic fluids to be recycled are not listed as 

hazardous wastes and can be burned for energy recovery or recycled. In general, the newer mineral oil 

hydraulic fluids (including water-in-oil emulsion fluids) do not contain known chemicals or other materials 

that are listed in 40 CFR 261 (RCRA) and can be burned for energy recovery or recycled. However, this may 

not apply to some of the older hydraulic fluids, particularly those containing PCBs. 

Organophosphate Ester Hydraulic Fluids. Disposal of used organophosphate ester hydraulic fluids 

is regulated as used oil under the Solid Waste Disposal Act as amended by the RCRA and as amended by the 

Used Oil Recycling Act (42 U.S.C. 6901,6905,6935,6937-6939, and 6074, see 40 CFR parts 260,261, 

266,271, and 279). Used organophosphate ester hydraulic fluids to be recycled are not listed as hazardous 

wastes and can be burned for energy recovery or recycled. In general, the newer organophosphate ester 

hydraulic fluids do not contain known chemicals or other materials that are listed in 40 CFR 261 (RCRA) and 

can be burned for energy recovery or recycled. 

Polyalphaolefin Hydraulic Fluids. Disposal of used polyalphaolefin hydraulic fluids is regulated as 

used oil under the Solid Waste Disposal Act as amended by the RCRA and as amended by the Used Oil 

Recycling Act (42 U.S.C. 6901, 6905, 6935, 6937-6939, and 6074, see 40 CFR parts 260, 261, 266, 271, 

and 279). Used polyalphaolefin hydraulic fluids to be recycled are not listed as hazardous wastes and can be 

burned for energy recovery or recycled. In general, the new polyalphaolefin hydraulic fluids covered in this 

profile do not contain known chemicals or other materials that are listed in 40 CFR 261 (RCRA) and can be 

burned for energy recovery or recycled. 

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5. POTENTIAL FOR HUMAN EXPOSURE 

5.1 OVERVIEW 

Hydraulic fluid contaminants have been identified in at least 10 of 1,428 current or former NPL Sites 

(HazDat 1996). All of these sites are located in the conterminous United States. The frequency of these sites can 

be seen in Figure 5-l. However, the number of sites evaluated for hydraulic fluids is not known. 

Mineral Oil Hydraulic Fluids. Mineral oil and water-in-oil emulsion hydraulic fluids are used 

extensively in virtually all heavy industries as well as in construction equipment, automobiles, tractors, 

trucks, and material handling equipment. Potentially exposed populations include workers in heavy and allied 

industries and the general population due to the use of hydraulic fluids in automobiles; however, this profile 

does not focus on automotive fluids. The most common route of exposure is dermal contact with the neat fluid, 

although inhalation of oil mists and vapors may also occur. The components of mineral oil hydraulic fluids are 

present in many other petroleum-derived products including lubricating oils, so exposure to the major 

components of mineral oil hydraulic fluids is not limited to hydraulic fluid exposures. 

In the past, mineral. oil hydraulic fluids sometimes included additives such as polychlorinated biphenyls 

(PCBs) to improve the thermal resistance or other properties of the resulting fluids. These additives may 

present more toxicity risks than the primary ingredients of the hydraulic fluids. While such uses of PCBs 

have been discontinued, PCBs may be encountered as components of hydraulic fluids at NPL sites 

contaminated by hydraulic fluids (ATSDR 1993b). 

Organophosphate Ester Hydraulic Fluids. Organophosphate ester hydraulic fluids are used in 

applications that require the fluid to be fire resistant, for example, in aircraft and in electrohydraulic control 

systems of steam turbines. It is not likely that significant concentrations in air will occur from such sources. 

Exposed populations include aircraft maintenance workers and mechanics, as well as other workers who 

maintain hydraulic control systems that use organophosphate ester hydraulic fluids. The most-common route of 

exposure probably is dermal contact with the neat fluid, although inhalation exposure may also occur, probably 

from both mists and vapors. Organophosphate esters can also enter the environment from their use as 

plasticizers and antiwear additives in lubricating oils. Therefore, the occurrence of organophosphate esters in the 

environment cannot be uniquely associated with hydraulic fluid use. 

HYDRAULIC FLUIDS 275 

5. POTENTIAL FOR HUMAN EXPOSURE
 

The synthesis of organophosphate ester compounds began in the mid-l 800s. From an early date, the most 

commercially useful compounds for lubricants, plasticizers, and hydraulic fluids were in the chemical family 

of the tertiary esters. Before the 1960s products were introduced based on alkyl aryl phosphates that could 

contain chlorinated aromatic hydrocarbons. Such products have now entirely disappeared from commercial 

use, and the vast majority of the industrial organophosphate esters are based on triaryl phosphates with no 

halogenated components (Marino 1992). However, at older waste disposal sites, hydraulic fluid site 

contaminants could contain chlorinated hydrocarbons. As with the PCBs formerly included as additives in 

other forms of hydraulic fluids, these additives may present more toxicity risks than the primary ingredients 

of the hydraulic fluids. 

One of the main human health concerns about organophosphate esters is the potential for neurotoxicity 

reactions, in particular a condition known as organophosphate-induced delayed neurotoxicity (OPIDN). 

Tri-ortho-cresyl phosphate (TOCP) has been identified as one of the more potent OPlDN neurotoxins in 

humans, and was formerly a constituent in some organophosphate ester hydraulic fluid products (Marino 

1992; Marino and Placek 1994). Production processes now routinely remove virtually all the TOCP. For 

instance, tricresyl phosphate (TCP) products now typically are manufactured to contain over 98% meta and 

para isomers and virtually no TOCP (Marino and Placek 1994). At waste disposal sites, however, site 

contaminants from older product formulations containing the ortho form may be encountered. 

Polyalphaolefin Hydraulic Fluids. Polyalphaolefin hydraulic fluids are used in most applications 

where mineral oil fluids are used, especially those that require proper operation in cold temperatures since 

polyalphaolefins possess very good temperature characteristics. Exposed populations will include 

maintenance workers and mechanics who maintain hydraulic control systems that use polyalphaolefin 

hydraulic fluids. The hydrocarbon isomers of polyalphaolefin hydraulic fluids probably are also present in 

mineral oil, so the presence of the components of polyalphaolefins in the environment cannot be uniquely 

associated with polyalphaolefin hydraulic fluid usage. Nonetheless, polyalphaolefin oils have a much 

narrower distribution of molecular weights than mineral oils (Chrisope and Landry 1993). If, for example, 

there is a spill of a hydraulic fluid containing only polyalphaolefin oils, the gas chromatograpliic scan would 

be different than the scan for a similar mineral-oil-based hydraulic fluid. Polyalphaolefin oils, however, are 

blended with mineral oils to achieve particular properties in hydraulic fluids (Collins 1993), making it 

impossible to identify the presence of a polyalphaolefin oil in these cases. In addition, polyalphaolefin oils 

are used for applications other than hydraulic fluids, and the presence of a polyalphaolefin oil in the 
HYDRAULIC FLUIDS 276 

5. POTENTIAL FOR HUMAN EXPOSURE
 

environment may result from release of a substance such as motor oil that contains polyalphaolefins, rather 

than hydraulic fluids. 

5.2 RELEASES TO THE ENVIRONMENT 

5.2.1 Air 

Mineral Oil Hydraulic Fluids. The majority of the components of mineral oil and water-in-oil emulsion 

hydraulic fluids are not on the Toxics Release Inventory (TRI). Some water-in-oil emulsion hydraulic fluids 

contain ethylene glycol (Houghton 1992; Quaker 1993), which is subject to reporting under TRI. 

Nonetheless, since ethylene glycol is used in numerous other applications and represents <10% (Houghton 

1992; Quaker 1993) of the total volume of water-in-oil emulsion hydraulic fluids, it is not anticipated that 

TRI information concerning releases of ethylene glycol will be indicative of water-in-oil emulsion hydraulic 

fluid use. It may be difficult to estimate the release of mineral oil or water-in-oil emulsion hydraulic fluids to 

air by identifying occurrences of mineral oil (the major constituent) in air at a particular facility since mineral 

oils are also used in numerous other products and applications, and concentrations of the components cannot 

always be uniquely associated with mineral oil hydraulic fluid release. 

Weschler et al. (1990) reported that the concentration of individual paraffins present in the air of a building 

was 0.0088-0.262 mg/m3

 and was associated with operating a hydraulic elevator. Mineral oil hydraulic 

fluids, therefore, may be released to the air during use in hydraulic elevators (and probably other hydraulic 

equipment) and can come from volatilization or as mists or aerosols from fluid reservoirs and mechanisms 

such as actuation pistons. It is not likely that significant concentrations in air will occur from such sources. 

Organophosphate Ester Hydraulic Fluids. None of the known components of organophosphate 

ester hydraulic fluids are on the TRI. Releases of organophosphate ester hydraulic fluids in air are probably 

lower than mineral oil hydraulic fluids because of their lower vapor pressures. It may be difficult to estimate 

the release of organophosphate ester hydraulic fluids to air by identifying occurrences of organophosphate 

esters (the major constituents) in air at a particular facility since organophosphate esters are also used in 

numerous other products and applications, and concentrations of the components cannot always be uniquely 

associated with organophosphate ester hydraulic fluid release. 
HYDRAULIC FLUIDS 277 

5. POTENTIAL FOR HUMAN EXPOSURE
 

A component of Skydrol 500B and Skydrol LD (tributyl phosphate) was detected in the air at the CP air test 

facility at Vancouver International Airport at a concentration of 0.04-0.3 mg/m3

 (Labour-Canada 1990), 

indicating that organophosphate ester hydraulic fluids may be released during aircraft maintenance operations 

on equipment using organophosphate ester hydraulic fluids. 

Polyalphaolefin Hydraulic Fluids. None of the known components of polyalphaolefin hydraulic fluids 

are on the TRI. Releases of polyalphaolefin hydraulic fluids in air are probably similar to mineral oil 

hydraulic fluids. It may be difficult to estimate the release of polyalphaolefin hydraulic fluids to air by 

identifying occurrences of polyalphaolefin hydrocarbon isomers in air at a particular facility since these 

constituents also are present in mineral oil and concentrations of the components cannot always be uniquely 

associated with polyalphaolefin hydraulic fluid release. Nonetheless, the gas chromatographic profile of a 

polyalphaolefin will be very different than that of a mineral oil, and identification may be possible when 

polyalphaolefins predominate in a sample. 

5.2.2 Water 

Mineral Oil Hydraulic Fluids. The majority of the components of mineral oil and water-in-oil emulsion 

hydraulic fluids are not on the TRI. Some water-in-oil emulsion hydraulic fluids contain ethylene glycol 

(Houghton 1992; Quaker 1993), which is subject to reporting under the TRI. Nonetheless, since ethylene 

glycol is used in numerous other applications and represents < 10% of the total volume of water-in-oil 

emulsion hydraulic fluids, it is not anticipated that TRI information concerning releases of ethylene glycol 

will be indicative of water-in-oil emulsion hydraulic fluid use. It may be difficult to estimate the release of 

mineral oil or water-in-oil emulsion hydraulic fluids to water by identifying occurrences of mineral oil (the 

major constituent) in water at a particular facility since mineral oils also find use in numerous other products 

and applications, and concentrations of the components cannot always be uniquely associated with mineral oil 

hydraulic fluid release. 

Releases of mineral oil hydraulic fluids from hydraulic systems at a steel mill were estimated G be 

5,680 L/year from continuous leakage and 5,670 L/year from accidents such as line breakage (Per1 et al. 

1985). Spills and leakage were sent to a lagoon and then treated by a waste water treatment plant. If this 

amount of leakage is typical for industries using hydraulic systems, then loss of hydraulic fluids to the 

environment will be very large. Abdul et al. (1990) reported the spill of ≈ 208,000 gallons of automatic 
HYDRAULIC FLUIDS 278 

5. POTENTIAL FOR HUMAN EXPOSURE
 

transmission fluid (ATF) from storage tanks. The ATF migrated to groundwater. No information concerning 

releases from other hydraulic systems were identified in the available literature. 

In the past, mineral oil hydraulic fluids sometimes included additives such as PCBs to improve the thermal 

resistance or other properties of the resulting fluids. While such uses of PCBs have been discontinued, PCBs 

may be encountered as a component of hydraulic fluids at NPL sites contaminated by hydraulic fluids 

(ATSDR 1993b). 

Organophosphate Ester Hydraulic Fluids. None of the known components of organophosphate 

ester hydraulic fluids are on the TRI. Releases of organophosphate ester hydraulic fluids to water are 

probably similar to mineral oil hydraulic fluids. It may be difficult to estimate the release of organophosphate 

ester hydraulic fluids to water by identifying occurrences of organophosphate esters (the major constituents) 

in water at a particular facility since organophosphate esters also find use in numerous other products and 

applications, and concentrations of the components cannot always be uniquely associated with 

organophosphate ester hydraulic fluid release. 

Polyalphaolefin Hydraulic Fluids. None of the known components of polyalphaolefin hydraulic fluids 

are on the TRI. Releases of polyalphaolefin hydraulic fluids to water are probably similar to mineral oil 

hydraulic fluids, only much smaller since they are not used as extensively. It should be noted that it may be 

difficult to estimate the release of polyalphaolefin hydraulic fluids to water by identifying occurrences of 

polyalphaolefin hydrocarbon isomers in water at a particular facility since these constituents also are present 

in mineral oil, and concentrations of the components cannot always be uniquely associated with 

polyalphaolefin hydraulic fluid release. Nonetheless, the gas chromatographic profile of a polyalphaolefin 

will be very different than that of a mineral oil, and identification may be possible when polyalphaolefins 

predominate in a sample. 

5.2.3 Soil 

Mineral Oil Hydraulic Fluids. The majority of the components of mineral oil and water-in-oil emulsion 

hydraulic fluids are not on the TRI. Some water-in-oil emulsion hydraulic fluids contain ethylene glycol 

(Houghton 1992; Quaker 1993), which is subject to reporting under TRI. Nonetheless, since ethylene glycol 

is used in numerous other applications and represents ≤10% of the total volume of water-in-oil emulsion 

hydraulic fluids, it is not anticipated that TRI information concerning releases of ethylene glycol will be 
HYDRAULIC FLUIDS 279 

5. POTENTIAL FOR HUMAN EXPOSURE
 

indicative of water-in-oil emulsion hydraulic fluid use (Houghton 1992; Quaker 1993). It may be difficult to 

estimate the release of mineral oil or water-in-oil emulsion hydraulic fluids to soil by identifying occurrences 

of mineral oil (the major constituent) in soil at a particular facility since mineral oils also find use in 

numerous other products and applications, and concentrations of the components cannot always be uniquely 

associated with mineral oil hydraulic fluid release. Abdul et al. (1990) reported that ≈208,000 gallons of 

automatic transmission fluid (ATF) was released to soil from a leaky storage tank. Soil in the area of the spill 

was saturated with ATF; concentrations decreased in lower soil layers. In addition, mineral oil and water-in oil 

emulsion hydraulic fluids are probably released to soil from leaks and spills in a manner similar to that 

described by Per1 et al. (1985) for water release. 

Organophosphate Ester Hydraulic Fluids. None of the known components of organophosphate 

ester hydraulic fluids are on the TRI. Releases of organophosphate ester hydraulic fluids to soil are probably 

similar to mineral oil hydraulic fluids. It may be difficult to estimate the release of organophosphate ester 

hydraulic fluids to soil by identifying occurrences of organophosphate esters (the major constituents) in soil at a 

particular facility since organophosphate esters also find use in numerous other products and applications, and 

concentrations of the components cannot always be uniquely associated with organophosphate ester hydraulic 

fluid release. 

Polyalphaolefin Hydraulic Fluids. None of the known components of polyalphaolefin hydraulic fluids 

are on the TRI. Releases of polyalphaolefin hydraulic fluids to soil are probably similar to mineral oil 

hydraulic fluids. It may be difficult to estimate the release of polyalphaolefin hydraulic fluids to soil by 

identifying occurrences of polyalphaolefin hydrocarbon isomers in soil at a particular facility since these 

constituents also are present in mineral oil and concentrations of the components cannot always be uniquely 

associated with polyalphaolefin hydraulic fluid release. Nonetheless, the gas chromatographic profile of a 

polyalphaolefin will be very different than that of a mineral oil, and identification may be possible when 

polyalphaolefins predominate in a sample. 
HYDRAULIC FLUIDS 280 

5. POTENTIAL FOR HUMAN EXPOSURE 

5.3 ENVIRONMENTAL FATE 

5.3.1 Transport and Partitioning 

No information on the transport and partitioning of all the components for any of the hydraulic fluids 

presented in this profile was located in the available literature; thus, a full accounting of the transport and 

partitioning is not possible. Information is available, however, concerning the transport and partitioning of 

some of the major components of the hydraulic fluids, which allows an assessment of some of these 

components. Since hydraulic fluids are formulated to conform to performance specifications and not to 

specific chemical analysis, any tests performed on a specific hydraulic fluid pertain only to that particular 

hydraulic fluid and not necessarily to earlier or later versions of the same fluid. 

Mineral Oil Hydraulic Fluids. No information identifying the major components of mineral oil or 

water-in-oil hydraulic fluids was located in the available literature, nor was any information located that 

described how the emulsifiers and other components in water-in-oil emulsion hydraulic fluids alter the 

environmental properties of the mineral oils contained in them. The carbon number range present in mineral 

oil hydraulic fluids probably is from C15 to C50 (IARC 1984; Shubkin 1993; Wills 1980). If automatic 

transmission fluids are typical of the mineral oil content in a hydraulic fluid, then mineral oil hydraulic fluids 

contain ≈ 90% mineral oil (Abdul et al. 1990; Papay 1989, 1991). Therefore, the transport and partitioning 

of these hydrocarbons will largely account for the environmental behavior of mineral oil hydraulic fluids. 

Typical transport and partitioning information for hydrocarbons in this range is presented below; this 

information is indicative of the transport and partitioning of mineral oils present in hydraulic fluids. 

The water solubility values of some C14-36 alkanes are presented in Table 3-7. The octanol/water partition 

coefficient log (KOW) of tetradecane (C14) is 7.2 (Hutchinson et al. 1980). Water solubilities for alkanes with 

more than about 10-l 5 carbon atoms (typical of the components in gasoline) are generally consider to be 

low, with highest estimates at about a log (KOW) value of 7.4 (ATSDR 1995). Based on the available 

measured data, C15-50 alkanes as a group are expected to have low water solubilities and high KOW values. In 

general, chemicals with low water solubilities and high KOW, values tend to partition to sediments when 

released to water and to sorb to soils (Lyman et al. 1982). Bioconcentration factors (BCFs) also tend to rise 

with increasing KOW values, but chemicals with very high octanol/water KOW values (>7) tend to have 

decreasing BCFs (Droy 1993). C15-50 hydrocarbons appear to partition to sediments and suspended particles 

(Bates et al. 1984; Saliot et al. 1985; Serrazanetti et al. 1991). Docosane (C22H46) has a BCF of 10,100 in 
HYDRAULIC FLUIDS 281 

5. POTENTIAL FOR HUMAN EXPOSURE
 

activated sludge and 8,730 in algae (Chlorella fusca), but only 10 in fish (golden ide) (Freitag et al. 1985). 

These results for the algae and sludge may reflect a simple partitioning phenomenon more than an actual 

physiologically-mediated bioconcentration of the docosane. By contrast, the marine diatom Cyclotella 

cryptica has a BCF of 2 for n-C16H34, but the BCF dropped to 0 for C28-30 hydrocarbons (Karydis 1980). In 

soil, C5-50 hydrocarbons adsorbed to sludge and tended to migrate only slowly into the surrounding soil (Liu 

1980). Based on the available BCF values, the hydrocarbon components of mineral oil hydraulic fluids show 

little tendency for bioaccumulation in animals. No studies were identified dealing with the various additives 

that are often associated with mineral-oil-based hydraulic fluid products. 

Organophosphate Ester Hydraulic Fluids. Most of the monitoring information available for 

components of organophosphate ester hydraulic fluids pertains to water and sediments, with only a few 

reports of organophosphate esters in soils and very few reporting air or rain concentrations (see Section 5.4). 

There is insufficient monitoring information to demonstrate that sediments and soils are the dominant 

environmental sinks, as the physical/chemical properties predict. 

The log KOW, water solubilities, and Henry’s law constants of several of the components that are present in the 

organophosphate ester hydraulic fluids included in this profile have been measured and are presented in 

Tables 3-4, 3-5, 3-8, and 3-9. In general, chemicals with low KOW (log KOW <1) tend to have high water 

solubilities, do not sorb to sediments, and do not bioconcentrate; chemicals with high KOW, tend to have low 

water solubilities, partition to sediments and soil, and bioconcentrate in fish (Lyman et al. 1982). Most of the 

values presented above are for mixtures and are the average values for all of the components in the mixture. 

Outdoor artificial ponds containing clay sediments (6% organic carbon, pH 6.8), fish, and chronomid larvae 

were treated with triphenyl phosphate, 2-ethylhexyl diphenyl phosphate, t-butylphenyl diphenyl phosphate, 

and tri(m-cresyl) phosphate and their concentration and partitioning monitored over time (Muir et al. 1985). 

After 18 hours, 62.3%, 61.5%, and 77.7% of the applied radioactivity was present in the sediment for 

2-ethylhexyl diphenyl phosphate (labeled at C1), t-butylphenyl diphenyl phosphate (ring labeled), and 

tri(m-cresyl) phosphate (ring-labeled), respectively. After 18 hours, ≈ 24% of the applied radioactivity was 

present in the water for all esters, and 1.3-l .8% of the applied radioactivity was present in the biota. After 

7 days, concentrations in the biota were ≤0.5%; and after 21 days, concentrations in the biota were below the 

detection limit ( ≤0.1 % or 0.2 mg). Sediment concentrations also dropped over time, although much more 

slowly. After 360 days, 23.6-30.5% of the applied radioactivity was still present in the sediments and was 

present at least to some extent as untransformed ester, as determined by gas chromatographic analyses. Air 
HYDRAULIC FLUIDS 282 

5. POTENTIAL FOR HUMAN EXPOSURE
 

concentrations measured at 5 cm above the ponds decreased from maximum concentrations of 1.97x10-4 and
 

3.2x 10-5

 mg/m3 measured in the first 18 hours for t-butylphenyl diphenyl phosphate and 2-ethylhexyl
 

diphenyl phosphate, respectively, to below 2x10-6 mg/m3

 after 3 days. By contrast, in a more complex
 

artificial pond containing clay sediments (6% organic matter, pH 6.8), fish (rainbow trout), duckweed, and
 

cattails, 32% and 34% of the applied radioactivity of 2-ethylhexyl diphenyl phosphate and triphenyl
 

phosphate, respectively, was present in the sediments after 24 hours, while 36% and 52%, respectively, was in
 

the water (Muir et al. 1982). Over the course of the experiment (240 hours), the cattails never absorbed a
 

measurable amount of radioactivity (0.2%), while the duckweed and fish absorbed 1.4-1.7% and 2.0-3.4%,
 

respectively, of the applied radioactivity in 24 hours. After 240 hours, the duckweed and fish contained 0.2-

0.5% and 3.0-0.5%, respectively, of the applied radioactivity (the amount of radioactivity in the fish appeared to
 

be decreasing during the experiment, but increased from 0.2% to 3.0% between 180 and 240 hours for 2-

ethylhexyl diphenyl phosphate). A study was conducted by Mayer et al. (1981) on the transport and partitioning
 

of Pydraul50E in a lake microcosm containing 8 L of sediment and 20 L of water. At the end of the 28-day test,
 

38-47% of the originally applied Pydraul 50E remained in the sediment. In the materials that remained in the
 

sediment, about 10% was triphenyl phosphate, and approximately 90% was nonylphenyl diphenyl phosphate
 

and cumylphenyl diphenyl phosphate. Significant degradation occurred in this system after 28 days. These
 

results show that, in general, the higher molecular weight fractions of the organophosphate ester hydraulic fluids
 

partition to the sediments, while lower molecular weight fractions tend to remain in the water column or
 

degrade.
 

The BCFs of some of the components of organophosphate ester hydraulic fluids are presented in Table 5-l.
 

In general, the larger organophosphate esters, such as cumylphenyl diphenyl phosphate, concentrate more in fish
 

because they have higher KOW values and hence, tend to partition to fat, while smaller ones, such as
 

triphenyl phosphate, concentrate less because they have lower KOW values and do not partition. In fish,
 

organophosphate esters appear to be more bioavailable when sediments are not present (Huckins et al. 1991),
 

but chronomids appear to be able to bioaccumulate organophosphate esters from the sediments (Muir et al.
 

1983b, 1985).
 

Polyalphaolefin Hydraulic Fluids. The transport and partitioning properties of the polyalphaolefin
 

hydraulic fluids will be similar to the mineral oil fluids since they contain similar aliphatic hydrocarbon
 

isomers.
 

HYDRAULIC FLUIDS 284 

5. POTENTIAL FOR HUMAN EXPOSURE 

5.3.2 Transformation and Degradation 

5.3.2.1 Air 

Mineral Oil Hydraulic Fluids. No information concerning the atmospheric transformation and 

degradation of C17-50 hydrocarbons was found in the available literature. Alkanes degrade in the atmosphere 

by reacting with hydroxyl radicals via hydrogen abstraction; reaction rates for n-alkanes increase with 

increasing chain length because more hydrogen ions are available for removal. Reaction rates for C 10-16 

hydrocarbons are (11.7-25.0)x10-12 cm3 s -1 (at 3 12 K) (Nolting et al. 1988), corresponding to gas phase 

halflives of 0.6-l .4 days for average hydroxyl radical concentrations of 0.5x10 -6 molecules cm-3. A study 

conducted by Cautreels and Van Cauwenberghe (1978) reported that C25-31 hydrocarbons were l-3 times 

more likely to be associated with particulates than with the gas phase, so the actual atmospheric half-life of 

these hydrocarbons may be longer. 

Organophosphate Ester Hydraulic Fluids. No information concerning the atmospheric 

transformation and degradation of organophosphate ester hydraulic fluids was found in the available 

literature. 

Polyalphaolefin Hydraulic Fluids. The transformation and degradation properties of the 

polyalphaolefin hydraulic fluids in air will be similar to the mineral oil fluids since they contain similar 

hydrogen isomers. 

5.3.2.2 Water 

Mineral Oil Hydraulic Fluids. In water, low concentrations of C15-50 hydrocarbons will biodegrade. 

Haines and Alexander (1974) reported that C16-44 hydrocarbons degraded in a soil-water suspension (64-7 1% 

degradation in 20 days), while Matsumoto (1983) reported that river water highly polluted with sewage 

degraded n-alkanes (>90% in 29 days) faster than branched alkanes. While these data indicate that C15-30 

hydrocarbons will biodegrade, no information is available that will allow an estimation of the rates of 

degradation in the environment or an estimation of any attenuating or accelerating effects other mineral oil 

hydraulic fluid components may have on degradation. 
HYDRAULIC FLUIDS 285 

5. POTENTIAL FOR HUMAN EXPOSURE 

Organophosphate Ester Hydraulic Fluids. Numerous reports are available detailing the aerobic 

biodegradation of organophosphate esters. These reports indicate that organophosphate esters will degrade 

with half-lives of a few days to several months under aerobic conditions, using a river die-away test. (A river 

die-away test is a very common biodegradation test in which river or lake water is spiked with a chemical of 

interest, and the concentration of the chemical is monitored with time. This type of test is more indicative of 

degradation in natural systems than tests using, for example, pure cultures or sludge inocula.) Results vary 

depending on the organophosphate used and the exact conditions of the test; triphenyl phosphate appears to 

degrade rapidly while more complex organophosphate esters degrade slowly (FMC 1978b; Heitkamp et al. 

1986; Howard and Deo 1979; Mayer et al. 1981; Monsanto 1978, 1983a, 198313, 1983c; Saeger et al. 1979). 

Specific complex esters for which river die-away test information is available include butyl diphenyl 

phosphate, tert-butylphenyl diphenyl phosphate, dibutyl phenyl phosphate, nonylphenyl diphenyl phosphate, 

and cumylphenyl phosphate. Similar half-lives are expected in the environment. 

Under sewage treatment plant conditions, organophosphate ester components of hydraulic fluids may not 

completely degrade, depending on the influent concentration. Some organophosphate esters were toxic to 

sludge microorganisms especially at feed rates of 13 mg/L, while lower feed rates were degraded 74-99% in 

24 hours (Saeger et al. 1979). 

Hydrolysis appears to be the most important abiotic degradative mechanism for organophosphate esters 

under basic pH conditions. Under neutral and acidic conditions, the reaction slows considerably and could 

become an insignificant removal mechanism. The hydrolysis proceeds by a stepwise mechanism in which one 

alcohol group is removed at a time. The first step is cleavage of a P-OR bond (where “R” is an aryl or alkyl 

group) to produce a diester of phosphoric acid, which, under basic conditions, becomes an anion. This anion is 

much more resistant to further hydrolytic cleavage than the triester (Barnard et al. 1961). This property of 

organophosphate esters may be of environmental importance since phosphoric acid diesters are much more 

soluble and very little is known concerning the environmental toxicity of these compounds. The available data 

do not provide sufficient descriptions of the experimental methods to determine if the rates are reliable (Barnard 

et al. 1961; Ciba-Geigy 1984e, 1986; Howard and Deo 1979; Mayer et al. 1981; Wolfe 1980). The majority of 

reports provide only a minimum of information and exclude important facts such as the duration of the 

experiments and the concentration of buffers. Despite the lack of experimental detail, published rate constants 

for base-catalyzed hydrolysis appear to be reasonably consistent and suggest that the hydrolytic half-life of 

triphenyl phosphate will vary from 350 days at pH 6.0 to 9.3 days at pH 8.5. Rates for tricresyl 
HYDRAULIC FLUIDS 286 

5. POTENTIAL FOR HUMAN EXPOSURE
 

phosphate appear to be on the same order as for triphenyl phosphate. Other alkylphenyl diphenyl phosphates 

appear to have rates about an order of magnitude smaller than triphenyl phosphate and tricresyl phosphate. 

Polyalphaolefin Hydraulic Fluids. The transformation and degradation properties of the 

polyalphaolefin hydraulic fluids in water will be similar to the mineral oil fluids since they contain similar 

aliphatic hydrocarbon isomers. 

5.3.2.3 Sediment and Soil 

Mineral Oil Hydraulic Fluids. No information concerning the transformation and degradation of 

mineral oil hydraulic fluids in sediments and soils was found in the available literature. 

Organophosphate Ester Hydraulic Fluids. Sediment degradation of organophosphate ester 

hydraulic fluid components was studied by Mayer et al. (1981) and Muir et al. (1982, 1985) in microcosms 

as described in Section 5.3.1. In general, these authors found that organophosphate esters partitioned to the 

sediments where degradation (presumably biodegradation) occurred slowly. Larger organophosphate esters 

degraded more slowly. The pseudo-first-order half-lives for t-butylphenyl diphenyl phosphate, cumylphenyl 

diphenyl phosphate, and tricresyl phosphate in sediment were 39,79, and 39 days, respectively (Muir et al. 

1985). Rates are expected to be dependent on environmental conditions such as temperature, contaminants, 

nutrients, and pre-exposure of the system to organophosphorus esters. 

While there is little information identified in the literature on empirical laboratory studies documenting 

disappearance rates in microcosms for organophosphate esters, one study (Heltkamp et al. 1984) provides 

results on degradation of the triaryl organophosphate known as isopropylphenyl diphenyl phosphate (IPDP). 

Results for both aerobic and anaerobic sediment microcosms showed a disappearance of less than 8% from the 

initial IPDP concentration levels after 4 weeks due to a combination of physical and biochemical 

degradation. IPDP is a common type of organophosphate ester, whose production has increased because of 

concerns over possible toxic impacts from tricresyl organophosphates and cresyl diphenyl organophosphates 

(Heltkamp et al. 1984). 

Studies conducted by Pickard et al. (1975) documented that bacteria can use triaryl phosphate-containing 

hydraulic or lubricating fluids as a carbon source. An innoculum of a mixed bacterial population was 

obtained from lake sediments that had a history of spills from aviation fuels and other petrochemical oils. 
HYDRAULIC FLUIDS 287 

5. POTENTIAL FOR HUMAN EXPOSURE
 

Tests showed cell growth on a commercial triaryl phosphate lubricating oil (Fyrquel 220) (0.5% TOCP by 

weight) and on its individual components, triphenyl phosphate, tri-ortho-cresyl phosphate and trixylenyl 

phosphate. The bacteria were able to emulsify the substrate, which increased the surface area and otherwise 

enhanced the conditions needed for actual biodegradation of the triaryl phosphates. Actual biodegradation, as 

reflected in cell growth, was still considered very low. The ability of the bacteria to emulsify the substrate, 

however, could accentuate chemical degradation processes such as hydrolysis (see Section 5.3.2.2 above). 

Polyalphaolefin Hydraulic Fluids. No information concerning the transformation and degradation of 

polyalphaolefin hydraulic fluids in sediments and soils was found in the available literature. 

5.4 LEVELS MONITORED OR ESTIMATED IN THE ENVIRONMENT 

5.4.1 Air 

Mineral Oil Hydraulic Fluids. It is difficult to assess the presence of mineral oil or water-in-oil 

emulsion hydraulic fluids in air by identifying occurrences of mineral oil (the major constituent) in air since 

mineral oils are also used in numerous other products and applications and these other applications account 

for a much greater volume than hydraulic fluid applications. For example, the National Petroleum Refiners 

Association (NPRA) reported that over 1 billion gallons of mineral-oil-based engine oils were sold in the 

United States every year from 1984 to 1991; this volume does not account for other mineral-oil-based 

products such as gear oils or other consumer, industrial, or commercial oil products (NPRA 1992). By 

contrast, only ≈ 200 million gallons of mineral oil and water-in-oil emulsion hydraulic fluids were sold each 

year between 1984 and 1991 (NPRA 1992). Thus, even if mineral oil or water-in-oil emulsion losses from 

hydraulic fluid were much greater on a percentage basis than losses from engine oils, because of the very 

large differences in use volumes, it would still be difficult to associate the occurrence of mineral oil in air with 

hydraulic fluid usage. 

Organophosphate Ester Hydraulic Fluids. Organophosphate esters are used in numaous 

applications other than hydraulic fluids including use as flame retardant plasticizers and antiwear additives to 

lube oils (FMC 199 lc, 1991 d, 1992c, 1992d; Weil 1980); no current estimates are available concerning the 

amounts of organophosphate esters used for these applications. Plasticizer applications include electrical 

insulation, automotive interiors, furniture upholstery, conveyor belts, and vinyl foams (Weil 1980), and some 

emissions to the air are expected from these uses. Therefore, organophosphate ester occurrence in air will be 
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5. POTENTIAL FOR HUMAN EXPOSURE
 

associated with hydraulic fluid, engine oil, plasticizer, and other uses. No reports of organophosphate ester 

occurrence in air were located in the available literature and only one report was found for occurrence in 

rainwater. Kawamura and Kaplan (1983) reported that unspecified concentrations of triphenyl phosphate and 

tributyl phosphate were detected in rainwater in Los Angeles. 

Polyalphaolefin Hydraulic Fluids. As is the case with mineral oil hydraulic fluids, assessing the 

presence of polyalphaolefin hydraulic fluids in air by identifying occurrences of the components of these 

hydraulic fluids may be difficult because the hydrocarbon isomers in polyalphaolefin hydraulic fluids also are 

present in mineral oils. Thus, the occurrence of polyalphaolefins in air cannot always be uniquely associated 

with hydraulic fluid usage. 

5.4.2 Water 

Mineral Oil Hydraulic Fluids. It is difficult to assess the presence of mineral oil or water-in-oil 

emulsion hydraulic fluids in water by identifying occurrences of mineral oil in water since mineral oils also 

find use in numerous other products and applications, which account for a much greater volume than 

hydraulic fluid applications. For example, NPRA (1992) reported that over 1 billion gallons of mineral-oilbased 

engine oils were sold in the United States every year from 1984 to 1991 and this volume does not 

account for other mineral-oil-based products such as gear oils or other consumer, industrial, or commercial oil 

products. By contrast, only ≈ 200 million gallons of mineral oil and water-in-oil emulsion hydraulic fluids 

were sold each year between 1984 and 1991 (NPRA 1992). Thus, even if mineral oil or water-in-oil 

emulsion losses from hydraulic fluid were much greater on a percentage basis than losses from engine oils, 

because of the very large differences in use volumes, it would still be difficult to associate the occurrence of 

mineral oil in the environment with hydraulic fluid usage. In addition, ≈ 193 million gallons of do-ityourselfgenerated used oils are disposed of annually (EPA 1992a), which is approximately equal to the entire 

sales volume of mineral oil and water-in-oil emulsion hydraulic fluids. Since do-it-yourself-generated used oils 

are not widely recycled, but disposed of in other ways (EPA 1992a), it is more likely that occurrences of mineral 

oil in water will be associated with engine oils than with hydraulic fluids. -. 

Abdul et al. (1990) reported that groundwater was contaminated with automatic transmission fluid (ATF) 

after a storage tank leaked ≈ 208,000 gallons onto the surrounding soil. Pure ATF penetrated the saturated 

zone and migrated with groundwater flow from there, saturating surrounding groundwater. 
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5. POTENTIAL FOR HUMAN EXPOSURE 

Organophosphate Ester Hydraulic Fluids. Organophosphate esters are used in numerous 

applications other than hydraulic fluids including use as flame retardant plasticizers and antiwear additives to 

lube oils (FMC 1991 c, 1991 d, 1992c, 1992d; Weil 1980); no current estimates are available concerning the 

amounts of organophosphate esters used for these applications. Plasticizer applications include electrical 

insulation, automotive interiors, furniture upholstery, conveyor belts, and vinyl foams (Weil 1980), and some 

emissions to the water are expected from these uses. Therefore, organophosphate ester occurrence in water will 

be associated with hydraulic fluid, engine oil, and plasticizer use. 

Data show that organophosphate esters, while not ubiquitous in surface waters, are geographically 

widespread contaminants and appear to be present principally in industrialized locations, especially where 

organophosphate esters are manufactured. In nonpolluted areas, concentrations typically are <l μg/L, but in 

polluted areas, concentrations appear to be in the range of ≈ l-10 μg/L (Deleon et al. 1986; EPA 1978, 

1979a; FMC 1977c, 1979, 1980; Konasewich et al. 1978; Mayer et al. 1981; Monsanto 1981; Sheldon and 

Hites 1978, 1979; Strachan 1974; Weber and Ernst 1983); however, concentrations < 29.5 μg/L have been 

reported (Keith et al. 1976; LeBel et al. 1981; Mayer et al. 1981; Suffet et al. 1980; Williams et al. 1982). 

For example, FMC (1979, 1980) reported that surface water concentrations of organophosphate esters were 

generally below the detection limit upstream of their Nitro, West Virginia, plant near the Kanawha River 

(where organophosphate esters are produced), while concentrations of 0.1-4.2 μg/L were detected 

downstream of the plant. Similarly, Mayer et al. (1981) found <0.1 μg/L of nonylphenyl diphenyl phosphate 

and cumylphenyl diphenyl phosphate at 9 of 10 locations throughout the midwest and San Francisco, but 

found 2-20 μg/L in 3 of 15 samples taken near Monsanto’s St. Louis organophosphate ester manufacturing 

facility. Thus, organophosphate esters are present in surface waters, particularly near manufacturing and use 

facilities, but the data suggest that they disappear rapidly from the water column by degradation or by 

partitioning to sediments, as indicated from the data presented in Sections 5.3.1 and 5.3.2. 

Organophosphate ester hydraulic fluid components have also been detected in groundwater near a hazardous 

waste site (1.7 μg/L tributyl phosphate) (Sawhney 1989) and in surface water from a radioactive waste disposal 

site (triphenyl phosphate and tributyl phosphate) (Francis et al. 1980). Organophosphate ester components of 

hydraulic fluids also have been detected in drinking water from New Orleans, the Great Lakes, and Philadelphia 

(Keith et al. 1976; LeBel et al. 1981; Suffet et al. 1980; Williams et al. 1982). 

Concentrations of 0.03-l .31 μg/L in finished water from New Orleans have been reported, and 

concentrations ≤29.5 μg/L in raw water taken from the Great Lakes have been reported. All finished water 

from six Ontario drinking water plants drawing their water from the Great Lakes contained tributyl and 
HYDRAULIC FLUIDS 290 

5. POTENTIAL FOR HUMAN EXPOSURE
 

triphenyl phosphates (0.2-11.8 ng/L) while tricresyl phosphate was detected in water from one plant (LeBel 

et al. 1981). 

Polyalphaolefin Hydraulic Fluids. As is the case with mineral oil hydraulic fluids, assessing the 

presence of polyalphaolefin hydraulic fluids in water by identifying occurrences of the components of these 

hydraulic fluids is difficult because the aliphatic hydrocarbon isomers in polyalphaolefin hydraulic fluids also 

are present in mineral oils. Thus, the occurrence of polyalphaolefins in water cannot always be uniquely 

associated with hydraulic fluid usage. 

5.4.3 Sediment and Soil 

Mineral Oil Hydraulic Fluids. It is difficult to assess the presence of mineral oil or water-in-oil 

emulsion hydraulic fluids in sediments and soil by identifying occurrences of mineral oil in sediments and soil 

since mineral oils also find use in numerous other products and applications and these other applications account 

for a much greater volume than hydraulic fluid applications. For example, NPRA (1992) reported that over 1 

billion gallons of mineral-oil-based engine oils were sold in the United States every year from 1984 to 1991, and 

this volume does not account for other mineral-oil-based products such as gear oils or other consumer, 

industrial, or commercial oil products. By contrast, only ≈ 200 million gallons of mineral oil and water-in-oil 

emulsion hydraulic fluids were sold each year between 1984 and 1991 (NPRA 1992). Thus, even if mineral oil 

or water-in-oil emulsion losses from hydraulic fluid were much greater on a percentage basis than losses from 

engine oils, because of the very large differences in use volumes, it would still be difficult to associate the 

occurrence of mineral oil in the environment with hydraulic fluid usage. In addition, ≈ 193 million gallons of 

do-it-yourself-generated used oils are disposed of annually (EPA 1992a), which is approximately equal to the 

entire sales volume of mineral oil and water-in-oil emulsion hydraulic fluids. Since do-it-yourself-generated 

used oils are not widely recycled, but disposed of in other ways (EPA 1992a), it is more likely that occurrences 

of mineral oil in sediments and soil will be associated with engine oils than with hydraulic fluids. 

Abdul et al. (1990) reported that upper layers of soil were saturated with automatic transmission fluid (ATF) 

after a storage tank leaked ≈ 208,000 gallons onto the surrounding soil. Lower soil layers contained less 

ATF; volumetric ATF concentrations ranged from <10% to 40% at 80-0 cm above the ATF table. 
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5. POTENTIAL FOR HUMAN EXPOSURE 

Organophosphate Ester Hydraulic Fluids. Organophosphate esters are used in numerous 

applications other than hydraulic fluids including use as flame retardant plasticizers and antiwear additives to 

lube oils (FMC 1991c, 1991 d, 1992c, 1992d; Weil 1980); no current estimates are available concerning the 

amounts of organophosphate esters used for these applications. Plasticizer applications include electrical 

insulation, automotive interiors, furniture upholstery, conveyor belts, and vinyl foams (Weil 1980), and some 

emissions to the soil and sediment are expected from these uses. Therefore, organophosphate ester occurrence in 

soils and sediment will be associated with hydraulic fluid, engine oil, and plasticizer use. 

Sediment monitoring data present a different picture than the water monitoring data discussed above. For 

most cases in which organophosphate esters were detected in water, concentrations many times higher were 

found in the sediment (Adams et al. 1986; EPA 1978, 1979a; FMC 1977c; Konasewich et al. 1978; Mayer et al. 

1981). The concentration factors ranged from around 100 to >108

. This is expected, based on the 10g KOW for 

these chemicals. When detected, sediment concentrations were in the range of <100 to >6,300,000 μg/L. While 

not ubiquitous, detectable concentrations in the sediment were found in more locations than concentrations in 

water, indicating a more widespread release than would be expected from the water monitoring data alone. 

These data also support the indication of microcosm studies (see Sections 5.3.1 and 5.3.2) that the water column 

rapidly looses detectable concentrations of organophosphate esters to the sediments, which accumulate the 

esters. The data further show that concentrations of triphenyl phosphate in the environment are lower than 

concentrations of other organophosphate esters. This agrees with the data presented above, which indicate that 

triphenyl phosphate degrades more rapidly than the other 

organophosphate esters. 

Typical concentrations are more difficult to determine for sediments than for water since the range of reported 

values is very large, and most of the monitoring is not random but centered around manufacturing facilities 

(sediment concentrations are not limited by the solubility of the organophosphate esters as are water 

concentrations). In the sediment, concentrations appear to drop off rapidly with distance from the source (FMC 

1979, 1980). This further indicates that sorption to sediments is rapid as well as thermodynamically favored. 

Monitoring studies of the Kanawha River in Nitro, West Virginia, by FMC (1980) revealed unspecified aryl 

phosphates at 7,200-6,320,OOO ug/kg within 800 yards of the plant outfall. Mayer et al. (1981) reported 

sediment concentrations in the range of 10-20,000 pg/kg in a variety of locations. Higher sediment 

concentrations are also commonly reported. Both tricresyl phosphate and isopropylphenyl diphenyl phosphate 

were detected at 5,000 ug/kg in sediment from Bethlehem, Pennsylvania, where fire resistant 
HYDRAULIC FLUIDS 292 

5. POTENTIAL FOR HUMAN EXPOSURE 

hydraulic fluids are used in steel mills (EPA 1979a). Organophosphate esters were detected at 

1,580,000 ug/kg in sediment samples from Kishacoquillas Creek, Pennsylvania (Sheaffer 1977). 

Polyalphaolefin Hydraulic Fluids. As is the case with mineral oil hydraulic fluids, it may be difficult 

to assess the presence of polyalphaolefin hydraulic fluids in sediments and soil by identifying occurrences of 

the components of these hydraulic fluids, because the aliphatic hydrocarbon isomers in polyalphaolefin 

hydraulic fluids also are present in mineral oils. Thus, the occurrence of polyalphaolefins in sediments and 

soil cannot always be uniquely associated with hydraulic fluid usage. 

5.4.4 Other Environmental Media 

Mineral Oil Hydraulic Fluids. It is difficult to assess the presence of mineral oil or water-in-oil 

emulsion hydraulic fluids in other environmental media by identifying occurrences of mineral oil (the major 

constituent) in other environmental media since mineral oils also find use in numerous other products and 

applications and these other applications account for a much greater volume than hydraulic fluid applications. 

For example, NPRA (1992) reported that over 1 billion gallons of mineral-oil-based engine oils were sold in the 

United States every year from 1984 to 1991, and this volume does not account for other mineral-oil-based 

products such as gear oils or other consumer, industrial, or commercial oil products. By contrast, only ≈200 

million gallons of mineral oil and water-in-oil emulsion hydraulic fluids were sold each year between 1984 and 

1991 (NPRA 1992). Thus, even if mineral oil or water-in-oil emulsion losses from hydraulic fluid were much 

greater on a percentage basis than losses from engine oils, because of the very large differences in use volumes, 

it would still be difficult to associate the occurrence of mineral oil in the environment with hydraulic fluid 

usage. In addition, ≈ 193 million gallons of do-it-yourself-generated used oils are disposed of annually (EPA 

1992a), which is approximately equal to the entire sales volume of mineral oil and water-in-oil emulsion 

hydraulic fluids. Since do-it-yourself-generated used oils are not widely recycled, but disposed of in other ways 

(EPA 1992a), it is more likely that occurrences of mineral oil in other environmental media will be associated 

with engine oils than with hydraulic fluids. No literature was identified dealing explicitly with the bioavailability 

of mineral-oil-based hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. Organophosphate esters are used in numerous 

applications other than hydraulic fluids including use as flame retardant plasticizers and antiwear additives to 

lube oils (FMC 1991c, 1991d, 1992c, 1992d; Weil 1980); no current estimates of the amounts of 

organophosphate esters used for these applications are available. Plasticizer applications include electrical 
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5. POTENTIAL FOR HUMAN EXPOSURE
 

insulation, automotive interiors, furniture upholstery, conveyor belts, and vinyl foams (Weil 1980), and some 

uptake by other environmental media are expected from these uses. Therefore, organophosphate ester 

occurrence in other environmental media will be associated with hydraulic fluid, engine oil, and plasticizer 

use. 

Organophosphate esters have also been detected in vegetation around manufacturing and use facilities and in 

sewage sludge. The detection of organophosphate esters on vegetation suggests that when emitted, 

organophosphate esters are present as aerosols that deposit in detectable concentrations near the site of origin 

(EPA 1978, 1979a). Positive detections on vegetation ranged from 1,000 to 20,000 ppb, while soil 

concentrations ranged from 100 to 400,000 ppb (EPA 1978, 1979a). The presence of organophosphate 

esters in sewage sludge (Konasewich et al. 1978) indicates that these compounds are not always degraded in 

sewage treatment plants, but removal from the influent water may be accomplished by a combination of 

sorption and degradation. Landfilling of the sludge may result in a more widespread distribution of these 

compounds in the environment since municipal waste landfills are sometimes used to dispose of sewage 

sludge and these landfills are not always lined with materials that prevent leaching and/or runoff. 

Nonetheless, many organophosphate esters are strongly sorbed to sludge and will not be subject to leaching or 

run off. 

Organophosphate ester components of hydraulic fluids such as triphenyl phosphate, nonylphenyl diphenyl 

phosphate, and cumylphenyl phosphate also have been detected in fish; concentrations of 0.1-0.9 μg/g of 

fish tissue were detected principally near manufacturing facilities, while fish caught in other areas generally 

had concentrations below the detection limit (0.1 μg/g) (Mayer et al. 1981). In a market basket survey, 

tributyl phosphate was found to be present in 2% of the foods analyzed between April 1982 and April 1984 

(Gunderson 1988). Intakes of tributylphosphate were estimated to be a maximum of 38.9 ng/kg body 

weight/day for 6- to 11 -month-old children. 

Polyalphaolefin Hydraulic Fluids. As is the case with mineral oil hydraulic fluids, assessing the 

presence of polyalphaolefin hydraulic fluids in other environmental media by identifying occurrences of the 

components of these hydraulic fluids may be difficult because the aliphatic hydrocarbon isomers in 

polyalphaolefin hydraulic fluids also are present naturally in mineral oils. Thus, the occurrence of 

polyalphaolefins in other environmental media cannot always be uniquely associated with hydraulic fluid 

usage. 
 

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5. POTENTIAL FOR HUMAN EXPOSURE 

5.5 GENERAL POPULATION AND OCCUPATIONAL EXPOSURE 

Mineral Oil Hydraulic Fluids. Mineral oil and water-in-oil hydraulic fluids comprise the largest 

category of hydraulic fluids under consideration. These fluids include automobile automatic transmission 

fluids and power steering fluids as well as fluids used in many industrial and commercial applications. 

Because of this, extremely widespread general population, occupational, and military exposure to these fluids is 

expected, including exposures of automobile, truck, and tractor mechanics and workers in any heavy or light 

industry that makes use of hydraulic equipment (including forklift trucks, construction equipment, and farm 

equipment). While estimates of the numbers of persons occupationally exposed were not located in the available 

literature, the number of workers exposed will be extremely high, since mineral oil hydraulic fluids are used in 

virtually all heavy industry. No recent estimates were found that quantified the general population exposure to 

mineral oil hydraulic fluids from do-it-yourself operations; however, the numbers may be very large. Exposure 

will probably occur by both dermal contact and inhalation. 

Weschler et al. (1990) reported that the concentration of individual paraffins present in the air of a building 

was 0.0088-0.262 mg/m3

 and was associated with operating a hydraulic elevator. 

Organophosphate Ester Hydraulic Fluids. Organophosphate ester hydraulic fluids are used in 

applications that require a degree of fire resistance such as in aircraft. EPA (1992b) has noted that aircraft 

mechanics may have dermal exposures of 1,300-3,900 mg/day and that 2,200 aircraft workers are routinely 

exposed to tributyl phosphate, while another 43,000 mechanics may be exposed at various times. Estimates 

of worker exposure in other industries were not found in the available literature. General population and 

military personnel exposure to organophosphate ester hydraulic fluids is likely to be much lower than 

exposure to mineral oil hydraulic fluids because these fluids have more specialized uses. 

A component of Skydrol 500B and Skydrol LD (tributyl phosphate) was detected in the air at the CP air test 

facility at Vancouver International Airport at a concentration of 0.04-0.3 mg/m3

 (Labour Canada 1990), 

indicating that organophosphate ester hydraulic fluids may be released during aircraft maintenance operations 

on equipment using organophosphate ester hydraulic fluids. 
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5. POTENTIAL FOR HUMAN EXPOSURE
 

Polyalphaolefin Hydraulic Fluids. Polyalphaolefin hydraulic fluids find significant use in a number of 

applications including situations where cold temperature operation is important. Applications include 

construction equipment and other machinery that is designed to operate in cold conditions. No estimates of 

either occupational or general population exposure to these hydraulic fluids were found in the available 

literature. 

5.6 POPULATIONS WITH POTENTIALLY HIGH EXPOSURES 

Mineral Oil Hydraulic Fluids. Populations with potentially high exposures to mineral oil hydraulic 

fluids include all occupations that maintain hydraulic equipment including automobile, truck, and tractor 

mechanics, mechanics employed by heavy industry and mining operations to repair and maintain hydraulic 

equipment, and other maintenance workers involved with the repair and maintenance of hydraulic systems. 

The number of workers with potentially high exposures to mineral oil hydraulic fluids is expected to be very 

large. 

Organophosphate Ester Hydraulic Fluids. Populations with potentially high exposures to 

organophosphate ester hydraulic fluids include aircraft mechanics and other mechanics repairing and 

maintaining hydraulic equipment designed to operate near combustion sources that require fire resistant 

hydraulic fluids. 

Polyalphaolefin Hydraulic Fluids. Populations with potentially high exposures to polyalphaolefin 

hydraulic fluids include mechanics repairing and maintaining hydraulic equipment containing polyalphaolefin 

hydraulic fluids, including military personnel using or repairing equipment having these fluids. 

5.7 ADEQUACY OF THE DATABASE 

Section 104(i)(5) of CERCLA, as amended, directs the Administrator of ATSDR (in consultation with the 

Administrator of EPA and agencies and programs of the Public Health Service) to assess whether adequate 

information on the health effects of hydraulic fluids is available. Where adequate information is not 

available, ATSDR, in conjunction with the NTP, is required to assure the initiation of a program of research 

designed to determine the health effects (and techniques for developing methods to determine such health 

effects) of hydraulic fluids. 
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5. POTENTIAL FOR HUMAN EXPOSURE
 

The following categories of possible data needs have been identified by a joint team of scientists from 

ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that if met would 

reduce the uncertainties of human health assessment. This definition should not be interpreted to mean that 

all data needs discussed in this section must be filled. In the future, the identified data needs will be evaluated 

and prioritized, and a substance-specific research agenda will be proposed. 

5.7.1 Identification of Data Needs 

Most hydraulic fluid preparations start as chemical mixtures. For instance, there is a considerable area of 

overlap in the specific petroleum hydrocarbon chemicals contained in the mineral oil and polyalphaolefin 

hydraulic fluids. For all classes of hydraulic fluids, there may be similarities with other original products 

intended for use as lubricants. The complications involved in documenting the environmental fate of 

mixtures increase under conditions encountered at many NPL sites, where it may be hard to determine the 

precise original product associated with chemicals identified at an area in need of remediation. In most 

instances, available peer-reviewed literature, supplemented with data obtained from manufacturers of 

particular formulations and information in trade magazines, can supply information about the original 

hydraulic fluid preparations. At NPL sites, site-specific evaluations of specific chemicals may be the only 

feasible way to address concerns over environmental fate and potential exposure risks. 

In the sections that follow, the data needs issues for the mineral oil and polyalphaolefin hydraulic fluids will 

be discussed first. This will be followed in each section by a discussion of issues regarding organophosphate 

ester-based products. 

Physical and Chemical Properties. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. Limited information about 

environmentally important physical and chemical properties is available for the mineral oil and water-in-oil 

emulsion hydraulic fluid products and components is presented in Tables 3-4,3-5, and 3-7. Much of the 

available trade literature emphasizes properties desirable for the commercial end uses of the products as 

hydraulic fluids rather than the physical constants most useful in fate and transport analysis. Since the 

products are typically mixtures, the chief value of the trade literature is to identify specific chemical 

components, generally various petroleum hydrocarbons. Additional information on the properties of the 

various mineral oil formulations would make it easier to distinguish the toxicity and environmental effects 
 

HYDRAULIC FLUIDS 297 

5. POTENTIAL FOR HUMAN EXPOSURE
 

and to trace the site contaminant’s fate based on levels of distinguishing components. Improved information 

is especially needed on additives, some of which may be of more environmental and public health concern 

than the hydrocarbons that comprise the bulk of the mineral oil hydraulic fluids by weight. For the 

polyalphaolefin hydraulic fluids, basic physical and chemical properties related to assessing environmental 

fate and exposure risks are essentially unknown. Additional information for these types of hydraulic fluids is 

clearly needed. 

Organophosphate Ester Hydraulic Fluids. The physical and chemical property information available for 

the organophosphate ester hydraulic fluid products and components is presented in Tables 3-4, 3-5, 3-8, and 

3-9. Much of this information was abstracted from trade literature or data taken from material safety data 

sheets. While there is information on many of the major component chemicals in the hydraulic fluid products, 

there can still be major data uncertainties for products that involve mixtures of different components. While 

current manufacturing practices aim to minimize or eliminate the presence of such worrisome components as triortho-cresyl phosphate, there remain major uncertainties about the composition and properties of older products, 

which would be more commonly encountered as site contaminants at NPL sites. Additional information on 

physical and chemical properties for organophosphate ester hydraulic fluid products is, therefore, an important 

data need. 

Production, Import/Export, Use, Release, and Disposal. According to the Emergency Planning 

and Community Right-to-Know Act of 1986,42 U.S.C. Section 11023, industries are required to submit 

chemical release and off-site transfer information to the EPA. The Toxics Release Inventory (TRI), which 

contains this information for 1993, became available in May of 1995. This database will be updated yearly 

and should provide a list of industrial production facilities and emissions. However, most of the components 

contained in hydraulic fluids are not on the Toxics Release Inventory (TRI) (EPA 1995). 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. Very little public information is 

collected on the production volume and methods, import/export, applications, and disposal practices for the 

different types of mineral oil and polyalphaolefin hydraulic fluids. This is largely because public data series 

will generally not distinguish between hydraulic fluids and lubricants. Because of the extremely large number 

of workers and people in the general population exposed to these hydraulic fluids, development of more 

carefully defined data would allow a more accurate estimate of the numbers of people exposed and would 

allow development of likely routes of exposure and environmental loss. 
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5. POTENTIAL FOR HUMAN EXPOSURE
 

Organophosphate Ester Hydraulic Fluids. Very little is known about the production volume, import/ 

export, and disposal practices for the different types of organophosphate ester hydraulic fluids. Because of 

the large number of workers exposed to these hydraulic fluids, development of these data would allow a much 

more accurate estimate of the numbers of people exposed, and would allow development of likely routes of 

exposure and environmental loss. 

Environmental Fate. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. Very little direct information is 

available concerning the environmental fate of these categories of hydraulic fluids. Especially at NPL sites, 

the identity of the original products may be uncertain. Site-specific approaches are usually needed, involving 

analysis for more specific chemical constituents. Many of the chemicals are petroleum hydrocarbons often 

classified as long-chain paraffins, which show relatively modest water solubility or potential to migrate offsite 

or into groundwater. While not viewed as a major data need, additional studies on the environmental fate 

of the various chemicals in this category of hydraulic fluids would be useful for assessing potential human 

exposure near hazardous waste sites. 

Organophosphate Ester Hydraulic Fluids. Information is available on many of the major components of 

organophosphate ester hydraulic fluids, particularly on their aerobic biodegradation, monitoring, and 

environmental partitioning. Little research can be identified dealing with the actual multi-component 

mixtures typical of most hydraulic fluid products. There is also little information on some of the degradation 

products of organophosphate esters, such as diesters of phosphoric acid. Given the concerns over the toxicity of 

the organophosphate ester class of chemicals, further research for this category of hydraulic fluids is warranted. 

The development of this information will allow an assessment of the environmental transport, 

distribution, transformation, and degradation processes and provide a better understanding of how these 

processes affect environmental contamination. Given the tendency of organophosphate ester hydraulic fluids to 

partition to soils and sediments, research should be focussed on these media. More research is needed on the 

reactive importance of chemical degradation processes such as hydrolysis in relation to thepotential for 

biodegradation by some strains of bacteria (Pickard et al. 1974). 
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5. POTENTIAL FOR HUMAN EXPOSURE 

Bioavailability from Environmental Media. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. No literature was identified dealing 

with the bioavailability of chemicals in this category of hydraulic fluids. Because of this wide variation and 

the lack of any information in mammalian species, it is difficult to estimate bioavailability to humans. 

Additional research on the bioavailability of this category of hydraulic fluids would be valuable but may not 

be as high a priority as research on bioavailability issues for the phosphate ester-based hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. Very little is known about the bioavailability of 

organophosphorus esters. In fish, organophosphate esters appear to be more bioavailable when sediments are not 

present (Huckins et al. 1991), but chronomids appear to be able to bioaccumulate organophosphate esters from 

the sediments (Muir et al. 1983b, 1985). Because of this wide variation and the lack of any information in 

mammalian species, it is difficult to estimate bioavailability to humans. Development of bioavailability 

information in mammalian species will allow a better understanding of this complex process. Given the 

concerns over the toxicity of this class of hydraulic fluids, further research on this topic would be useful. 

Food Chain Bioaccumulation. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. While very little information 

dealing explicitly with the food chain bioaccumulation of this category of hydraulic fluids is available, the 

principle petroleum hydrocarbon constituents do not appear to have a significant tendency for 

bioconcentration, bioaccumulation, or biomagnification. There do not appear to be any major research needs on 

this topic for this class of hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. Very little information on the food chain bioaccumulation of 

organophosphate ester hydraulic fluids is available. It is known that some organisms bioconcentrate 

components of organophosphate ester hydraulic fluids (values are 133-2,807 for rainbow trout and 596-928 

for fathead minnows) (Lombardo and Egry 1979; Mayer et al. 1981; Muir et al. 1983a; Veithxt al. 1979). 

Given the concerns over the toxicity of this class of hydraulic fluids, further research on this topic would be 

useful. 
HYDRAULIC FLUIDS 300 

5. POTENTIAL FOR HUMAN EXPOSURE 

Exposure Levels in Environmental Media. Reliable monitoring data for the levels of all types of 

hydraulic fluids in contaminated media at hazardous waste sites are needed so that the information obtained 

on levels of these hydraulic fluids in the environment can be used in combination with the known body burden 

of these hydraulic fluids to assess the potential risk of adverse health effects in populations living in the vicinity 

of hazardous waste sites. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. Very limited information is 

available concerning levels of these hydraulic fluids in environmental media. The only available study 

described concentrations at a spill site (Abdul et al. 1990). No other reports of mineral oil hydraulic fluid 

exposure levels in environmental media were found in the available literature. At NPL sites, it becomes 

difficult to decide which original products are associated with documentation of specific site contaminants. 

General research dealing with assessment techniques relevant to complex petroleum hydrocarbon mixtures 

would be helpful in deciding how to approach the environmental media exposure issues. 

Organophosphate Ester Hydraulic Fluids. A large amount of monitoring data is available that describes 

the presence of many of the components of organophosphate ester hydraulic fluids in the environment 

(Deleon et al. 1986; EPA 1978, 1979a; FMC 1977c, 1979, 1980; Konasewich et al. 1978; Mayer et al. 1981; 

Monsanto 1981; Sheldon and Hites 1978, 1979; Strachan 1974; Weber and Ernst 1983). Additional 

research on this topic for the organophosphate ester hydraulic fluids is not a major data need. 

Exposure Levels in Humans. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. Very little current workplace 

monitoring data is available for this class of hydraulic fluids. The only studies that are available discuss 

leakage (Per1 et al. 1985) and alkane concentrations in an office building (Weschler et al. 1990). These 

hydraulic fluids are used in virtually every manufacturing and heavy industrial site as well as in most cars, so 

potentially exposed populations are very large. More data that better define the concentrations of mineral oil 

hydraulic fluid components in the workplace and in the vicinity of major industrial plants that-use hydraulic 

fluids would allow an assessment of the exposure levels of these populations. Some difficulty may be 

encountered in isolating hydrocarbons that result from use of mineral oil hydraulic fluid versus use of other 

mineral-oil-based products such as lubricants. Research efforts should be focused on populations where 

higher exposures are expected. Targeted research efforts on workplace exposure could be of great value to 
HYDRAULIC FLUIDS 301 

5. POTENTIAL FOR HUMAN EXPOSURE
 

document exposure risks resulting directly from hydraulic fluids as opposed to exposure to products (e.g., 

lubricants) that contain similar chemical components. 

Organophosphate Ester Hydraulic Fluids. Very little workplace monitoring data is available for 

organophosphate ester hydraulic fluids. The available study reports workplace air concentrations in an 

airport hangar (Labour Canada 1990). Since organophosphate ester hydraulic fluids are used in many 

manufacturing and heavy industrial sites and in aircraft (both military and civilian), potentially exposed 

populations are large. More data that better define the concentrations of organophosphate ester hydraulic 

fluid components would allow an assessment of the exposure levels of these populations. Some difficulty 

may be encountered in isolating organophosphate esters that result from hydraulic fluid use versus use of 

other organophosphate ester-containing products such as lubricants. 

This information is necessary for assessing the need to conduct health studies on these populations. 

Exposure Registries. No exposure registries for hydraulic fluids were located. This substance is not 

currently one of the compounds for which a subregistry has been established in the National Exposure 

Registry. The substance will be considered in the future when chemical selection is made for subregistries to be 

established. The information that is amassed in the National Exposure Registry facilitates the 

epidemiological research needed to assess adverse health outcomes that may be related to exposure to this 

substance. 

5.7.2 Ongoing Studies 

Mineral Oil Hydraulic Fluids. No information concerning ongoing studies on mineral oil or water-in-oil 

emulsion hydraulic fluids was located in the available literature. 

Organophosphate Ester Hydraulic Fluids. The EPA has published a proposed test rule (EPA 

992b) for testing aryl phosphate base stocks. The proposed tests include: 120-day post-hatch trout, chronic 

exposure neurotoxicity in the hen, two-generation reproduction and fertility effects, anaerobic biodegradation, 

chronic Daphnia magna, subchronic mammalian toxicity, aerobic biodegradation, microcosm ecosystem, and 

developmental toxicity. Since this proposed rule was published in January 1992, the comment period has closed, 

and EPA is considering what stocks to test, what tests to proceed with, and how to implement any testing 

program. As of early 1997, no final test rule had been published. 
HYDRAULIC FLUIDS 302 

5. POTENTIAL FOR HUMAN EXPOSURE 

Polyalphaolefin Hydraulic Fluids. No information concerning ongoing studies on polyalphaolefin 

hydraulic fluids was located in the available literature. 
HYDRAULIC FLUIDS 303 

6. ANALYTICAL METHODS
 

The purpose of this chapter is to describe the analytical methods that are available for detecting, and/or 

measuring, and/or monitoring hydraulic fluids, their metabolites, and other biomarkers of exposure and effect to 

hydraulic fluids. The intent is not to provide an exhaustive list of analytical methods. Rather, the intention is to 

identify well-established methods that are used as the standard methods of analysis. Many of the analytical 

methods used for environmental samples are the methods approved by federal agencies and 

organizations such as EPA and the National Institute for Occupational Safety and Health (NIOSH). Other 

methods presented in this chapter are those that are approved by groups such as the Association of Official 

Analytical Chemists (AOAC) and the American Public Health Association (APHA). Additionally, analytical 

methods are included that modify previously used methods to obtain lower detection limits, and/or to improve 

accuracy and precision. 

Mineral oil, water-in-oil emulsion, and polyalphaolefin hydraulic fluids all have components in common with 

a very large number of other products that are based on mineral oil and synthetic mineral oils 

(polyalphaolefins); these products include motor oils, fuel oils, and petroleum distillates. No analytical 

method can distinguish the source of mineral oil components; that is, mineral oil components that result from 

hydraulic fluids are indistinguishable from those resulting from other forms of mineral oil taken from the 

same distillation and processing cut. The analytical methods presented here are capable of identifying long 

chain alkanes (the components present in mineral oils and polyalphaolefins used in hydraulic fluids) and will 

be most useful when something is known about the source of contamination. 

Similarly, organophosphate esters are used in a wide variety of applications including hydraulic fluids, 

plasticizers, and antiwear additives to hydraulic fluids and engine oils. All of these uses have the potential to 

contaminate the environment, and all of the organophosphate ester components present in hydraulic fluids 

also are present in plasticizers and antiwear additives. Therefore, detection of a particular organophosphate 

ester in the environment or in biological media cannot identify the source of the contamination (i.e., hydraulic 

fluids, plasticizers, antiwear additives). 
HYDRAULIC FLUIDS 304 

6. ANALYTICAL METHODS 

6.1 BIOLOGICAL SAMPLES 

Mineral Oil Hydraulic Fluids. Several methods are available for analysis of the components of mineral oil 

hydraulic fluids (straight and branched chain alkanes) in biological samples. They are summarized in Table 6-l 

Several methods involve a preparation step followed by purification procedures, then analysis (Ferrario et al. 

1985a, 1985b; Hesselberg and Seelye 1982). Briefly, sample preparation includes homogenization and 

extraction. A low boiling hydrocarbon extraction solvent, alone or in combination with a more polar solvent, 

probably is best since all of the components of the mineral oil will be soluble in it. If lipids are present, they 

should be removed by gel permeation chromatography and the alkanes separated from other more polar 

compounds by silica gel chromatography. The purge-and-trap method involves homogenizing the sample, and 

then purging it with nitrogen (or other inert gas) while warming the sample. The purged gases are trapped on a 

Tern&silica gel column maintained at a low temperature. The trap is then heated to desorb the trapped material 

onto a GC column. All of the methods presented in this chapter for analyzing mineral oil hydraulic fluids in 

biological samples use gas chromatography (GC) for peak separation, coupled with mass spectrometry (MS) for 

peak identification. 

Organophosphate Ester Hydraulic Fluids. Few methods are available for determining 

organophosphate esters in biological samples. A summary is shown in Table 6-2. The only biological 

matrices with well established analytical procedures for organophosphate esters are fish (Muir et al. 1981) 

and human fat (LeBel and Williams, 1983; 1986). Preparation of tissue includes extraction and clean-up 

steps; determination is usually accomplished using GC with nitrogen/phosphorus detection (NPD). Selective 

detectors, such as the NPD, are preferred since biological matrices are usually complex. 

Fish tissue is homogenized with a Polytron apparatus using methanol as a solvent, or extracted in a ball mill 

with hexane. The extracts are evaporated to dryness, dissolved in ethyl acetate toluene, and cleaned up on a gel 

permeation column followed by an alumina column. Analysis is performed by GCYNPD (Muir et al. 

1981). Recovery is acceptable (79-97%) and limit of detection is 10 mg/g (Muir et al. 1981). 

Human adipose tissue samples are analyzed by homogenizing the sample with benzene or 15:85 acetonehexane 

and then centrifuging the sample and filtering the supemate through a sodium sulfate (Na2SO4) column. The 

organophosphate esters in the benzene extract are then separated from the fat by gel permeation 

chromatography, and the eluate is cleaned up using a Florisil column. Analysis is performed using GC/NPD. 


HYDRAULIC FLUIDS 307 

6. ANALYTICAL METHODS
 

Confirmation by GUMS is recommended. Recovery is acceptable (82%). Tributyl phosphate and triphenyl 

phosphate contamination was reported in procedural blanks and may prevent determination of phosphate 

esters at levels near the detection limit (1 ng/g) (LeBel and Williams 1983; 1986). 

Polyalphaolefin Hydraulic Fluids. The methods for analyzing polyalphaolefin hydraulic fluids are 

identical to those for the mineral oil hydraulic fluids (see Table 6-l). Polyalphaolefin oils can be 

distinguished from mineral oils because they will be present in combinations of the alphaolefin from which 

they were synthesized (Shubkin 1993). Thus, polyalphaolefins obtained from 1 -decene will be present as 

dimers (C20 alkanes), trimers (C30 alkanes), tetramers (C40 alkanes), pentamers (C50 alkanes), etc., with no 

alkanes between these isomers (e.g., there will be no C21 alkanes present in the oil). This method of 

identification will only be possible if the polyalphaolefin hydraulic fluids contain no mineral oils or if the 

samples being analyzed were not exposed to mineral oils. 

6.2 ENVIRONMENTAL SAMPLES 

Mineral Oil Hydraulic Fluids. Methods are available for analysis of the hydrocarbon components of 

mineral oil hydraulic fluids (predominantly straight and branched chain alkanes) in environmental samples. 

Some of these methods are summarized in Table 6-3. In general, water and sediment samples are extracted with 

a suitable solvent in a Soxhlet extractor (for solid samples) or in separatory funnel or shake flask (for liquid 

samples) (Bates et al. 1984; Peterman et al. 1980). The extract is cleaned up on silica gel or Florisil columns 

using a nonpolar solvent to elute the nonpolar alkanes. Analysis is usually performed by GC/MS (Bates et al. 

1984; Kawamura and Kaplan 1983; Peterman et al. 1980). Method performance has not been reported, although 

82% recovery of aliphatic hydrocarbons was reported for rainwater (Kawamura and 

Kaplan 1983). 

Air samples can be analyzed by passing a known volume of air through a Teflon filter to catch air particulates 

followed by an activated charcoal filter to trap any gas-phase materials. The Teflon filters are extracted with 

hexane, concentrated, and analyzed by GC/MS. The charcoal traps are desorbed with carbondisulfide, 

concentrated, and analyzed by GC/MS. No performance data were reported (Dannecker et al. 1990). 

HYDRAULIC FLUIDS 309 

6. ANALYTICAL METHODS 

Organophosphate Ester Hydraulic Fluids. Few analytical methods are available for analysis of 

organophosphate esters in environmental samples. A summary of methods is shown in Table 6-4. Care must be 

taken in the laboratory to assure that all labware, solvents and reagents are free of interfering 

contaminants. Organophosphate esters have widespread use and have been reported as sources of 

contamination (Muir 1984; LeBel and Williams 1986). 

Water samples are acidified and extracted with solvent (Kawamura and Kaplan 1983; Muir et al. 1981). 

Clean-up steps may be used (Kawamura and Kaplan 1983). Methylene chloride is often used as the 

extracting solvent, and it may interfere with the nitrogen-phosphorus detector. In this case, a solventexchange 

step is used (Muir et al. 1981). Analysis by GC/NPD or GC/MS provides specificity (Kawamura and Kaplan 

1983; Muir et al. 1981). Accuracy is acceptable (>80%), but precision has not been reported. Detection limits 

were not reported, but are estimated to be 0.05-0.1 μg/L (Muir et al. 1981). Detection limits at the low ppt level 

(ng/L) were achieved by concentrating organophosphate esters on XAD-2 resin. The analytes were solvent 

extracted from the resin and analyzed by GC/NPD and GC/MS. Recovery was acceptable (>70%) and precision 

was good (<10% RSD) (LeBel et al. 1981). 

A method for sediment involves Soxhlet extraction followed by filtration, and concentration to 5 mL. The 

residue is diluted with water, acidified, extracted with methylene chloride, and then the extracts are dried and 

evaporated to dryness. The residue is cleaned up on an alumina column. Analysis is performed by GC/NPD. 

Good recovery (81-97%) and precision (>15% RSD) were reported; detection limits were not reported (Muir et 

al. 1981). 

A method for food (fish) has been reported. The sample is ground with sodium sulfate and extracted with 

petroleum ether. The extract is cleaned up by liquid-liquid partition, followed by Florisil column 

chromatography. Analysis is performed by GC/NPD. Detection limits are 0.1 ppm; recovery was not reported 

(Lombard0 and Egry 1979). 

Polyalphaolefin Hydraulic Fluids. The methods for analyzing polyalphaolefin hydraulic fluids are 

identical to those for the mineral oil hydraulic fluids (see Table 6-3). Polyalphaolefin oil can be distinguished 

from mineral oils because they will be present in combinations of the alphaolefin from which they were 

synthesized (Shubkin 1993). Thus, polyalphaolefins obtained from 1-decene will be present as dimers (C20 

alkanes), trimers (C30 alkanes), tetramers (C40 alkanes), pentamers (C50 alkanes), etc., with no alkanes 

between these isomers (e.g., there will be no C21 alkanes present in the oil). This method of identification will 

HYDRAULIC FLUIDS 311 

6. ANALYTICAL METHODS
 

only be possible if the polyalphaolefin hydraulic fluids contain no mineral oils or if the samples being 

analyzed were not exposed to mineral oils. 

6.3 ADEQUACY OF THE DATABASE 

Section 104(I)(5) of CERCLA, as amended, directs the Administrator of ATSDR (in consultation with the 

Administrator of EPA and agencies and programs of the Public Health Service) to assess whether adequate 

information on the health effects of hydraulic fluids is available. Where adequate information is not 

available, ATSDR, in conjunction with the NTP, is required to assure the initiation of a program of research 

designed to determine the health effects (and techniques for developing methods to determine such health 

effects) of hydraulic fluids. 

The following categories of possible data needs have been identified by a joint team of scientists from 

ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that if met would 

reduce the uncertainties of human health assessment. This definition should not be interpreted to mean that 

all data needs discussed in this section must be filled. In the future, the identified data needs will be evaluated 

and prioritized, and a substance-specific research agenda will be proposed. 

6.3.1 Identification of Data Needs 

Methods for Determining Biomarkers of Exposure and Effect. 

Mineral Oil Hydraulic Fluids. No methods were identified for determining biomarkers of exposure to or effect 

of mineral oil hydraulic fluids. Nonetheless, the available analytical methods for identifying C15-50 

alkanes in biological tissues could be used to determine exposure levels (Ferrario et al. 1985a, 1985b; 

Hesselberg and Seelye 1982). The methods appear to be sensitive; however, since many compounds are 

being detected, the exact sensitivity depends on the alkane under consideration. The development of a 

method to identify metabolites of mineral oil hydraulic fluids in humans would aid in determining exposures. 

Organophosphate Ester Hydraulic Fluids. The measurement of organophosphate esters in fish and human 

adipose tissue has been used to assess environmental contamination in several studies (Mayer et al. 1981). The 

methods are able to detect concentrations of 0.1 mg/kg in fish and 2.5 μg/kg in human adipose tissue. At 

concentrations below this level, interferences from organophosphate esters used as plasticizers appear in 
HYDRAULIC FLUIDS 312 

6. ANALYTICAL METHODS
 

procedural blanks (Muir 1984). Several organophosphate esters have been detected in distilled water, 

pesticide grade solvents, and o-rings used in metering valves (Muir 1984). The methods appear to be 

adequate to identify background levels and can identify concentrations below known effect levels. 

Polyalphaolefin Hydraulic Fluids. No methods were identified for determining biomarkers of exposure or 

effect. Nonetheless, the available analytical methods for identifying C15-50 alkanes in biological tissues could be 

used to determine exposure levels (Ferrario et al. 1985a, 1985b; Hesselberg and Seelye 1982). The methods 

appear to be sensitive; however, since many compounds are being detected, the exact sensitivity depends on the 

alkane under consideration. The development of a method to identify metabolites of polyalphaolefin hydraulic 

fluids in humans would aid in determining exposures. 

Methods for Determining Parent Compounds and Degradation Products in Environmental 

Media. 

Mineral Oil Hydraulic Fluids. Analytical methods similar to those described above have been used to 

analyze straight and branch chained alkanes in the environment (Ferrario et al. 1985a, 1985b; Hesselberg and 

Seelye 1982). The methods appear to be sensitive, although the sensitivity depends on the alkane being 

analyzed. Determining the presence of a specific mineral oil hydraulic fluid (e.g., Sunsafe F hydraulic fluid) in 

the environment may be possible if all the components are known, but this may or may not work for other 

brands of the fluid. The mineral oil in a hydraulic fluid cannot be distinguished from other mineral oils 

derived from the same distillation cut/processing stream. If more information on the exact alkane isomer 

distribution present in representative common hydraulic fluids was available, it might be possible to 

distinguish, for example, a hydraulic fluid from a motor oil. 

Organophosphate Ester Hydraulic Fluids. Analytical methods similar to those described above have been 

used in many monitoring studies (Deleon et al. 1986; EPA 1978, 1979; FMC 1977c, 1979, 1980; 

Konasewich et al. 1978; Mayer et al. 1981; Monsanto 1981; Sheldon and Hites 1978, 1979; Strachan 1974; 

Weber and Ernst 1983). The methods are sensitive to ≈0.05 mg/kg for sediments and ≈0.5 μgpL for water. 

Interferences from organophosphate esters used as plasticizers appear in procedural blanks, and the potential for 

sources of contamination must be examined at sub-nanogram per gram levels (Muir 1984). Several 

organophosphate esters have been detected in distilled water, pesticide grade solvents, and o-rings used in 

metering valves (Muir 1984). The methods appear to be sensitive enough to determine background levels. While 

the major exposure medium for organophosphate ester hydraulic fluids is from the neat fluid, the 
HYDRAULIC FLUIDS 313 

6. ANALYTICAL METHODS
 

environmental media of concern are water and sediments since organophosphate ester hydraulic fluids appear to 

be discharged most often to water where they partition to sediments. 

Polyalphaolefin Hydraulic Fluids. Analytical methods similar to those described above have been used to 

analyze straight and branch chained alkanes present in polyalphaolefin hydraulic fluids in the environment 

(Ferrario et al. 1985a, 1985b; Hesselberg and Seelye 1982). The methods appear to be sensitive, although 

the sensitivity depends on the alkane being analyzed. Determining the presence of a specific polyalphaolefin 

hydraulic fluid (e.g., MLH-83282) in the environment may be possible if all the components are known, but this 

may or may not work for other types of polyalphaolefin fluids. The polyalphaolefin oil in a hydraulic fluid 

cannot be distinguished from other polyalphaolefin oils derived from the same catalyst/operating 

parameters/processing. If more information on the exact alkane isomer distribution present in representative 

common polyalphaolefin hydraulic fluids was available, it might be possible to distinguish, for example, a 

polyalphaolefin hydraulic fluid from a polyalphaolefin motor oil. 

6.3.2 Ongoing Studies 

No ongoing studies on the analytical chemistry of mineral oils, organophosphate esters, or polyalphaolefins 

were located in the available literature. 

HYDRAULIC FLUIDS 315 

7. REGULATIONS AND ADVISORIES
 

The national regulations and guidelines regarding hydraulic fluids in air, water, and other media are 

summarized in Table 7- 1. 

ATSDR has not derived any Minimal Risk Levels for hydraulic fluids. 

Regulations found for mineral oils include the OSHA occupational exposure limit for mineral oil mists of 

5 mg/m3

 (OSHA 1974). 

The only regulations found for organophosphate ester hydraulic fluids were for aryl phosphates. Two 

proposed rules for aryl phosphates address 1) exclusion from hazardous waste regulations and 2) additional 

testing, recordkeeping, and reporting under the Toxic Substances Control Act (TSCA). 

HYDRAULIC FLUIDS 317 

8. REFERENCES
 

*Abdul AS, Gibson TL, Kia SF. 1990. Contamination of soil and groundwater by automatic transmission
 

fluid: Site description and problem assessment. J Hydrol 121:133-153.
 

*Abou-Donia MB. 19 8 3. Interaction between neurotoxicities induced by organophosphorus and long-chain
 

hexacarbon compounds. Neurotoxicology 4:117-l 36.
 

*Abou-Donia MB, Lapadula DM. 1990. Mechanisms of organophosphorus ester-induced delayed
 

neurotoxicity: Type I and Type II. Ann Rev Pharmacol Toxicol 30:405-440.
 

*Abou-Donia MB, Lapadula DM, Campbell G, et al. 1985. The joint neurotoxic action of inhaled methyl
 

butyl ketone vapor and dermally applied O-ethyl O-4-nitrophenyl phenylphosphonothioate in hens:
 

Potentiating effect. Toxicol Appl Pharmacol79:69-82.
 

*Abou-Donia MB, Nomeir AA, Bower JH, et al. 1990b. Absorption, distribution, excretion, and metabolism
 

of a single oral dose of [‘“Cl tri-ortho-cresyl phosphate (TOCP) in the male rat. Toxicology 65:61-74.
 

*Abou-Donia MB, Suwita E, Nomeir AA. 1990a. Absorption, distribution, and elimination of a single oral
 

dose of [‘4C]tri-ortho-cresy1 phosphate in hens. Toxicology 6 1: 13-25.
 

*Adams WJ, Ziegenfuss PS, Renaudette WJ, et al. 1986. Comparison of laboratory and field methods for 

testing the toxicity of chemicals sorbed to sediments. In: Poston TM, Purdy R, eds. Aquatic toxicology and 

environmental fate, Vol. 9. American Society for Testing and Materials Special Technical Publication 921, 

494-5 13. 

*Akzo. 1988. Material Safety Data Sheet for Fyrquel LT. 1 l/88. Akzo Chemicals, Inc., Chicago, IL.
 

*Akzo. 1989. Material Safety Data Sheet for Fyrquel 150. 2/89. Akzo Chemicals, Inc., Chicago, IL.
 

*Akzo. 1991. Material Safety Data Sheet for Fyrquel EHC. 2/9 1. Akzo Chemicals, Inc., Chicago, IL.
 

*Akzo. 1992. Material Safety Data Sheet for Fyrquel220. l/92. Akzo Chemicals, Inc., Chicago, IL.
 

*Akzo. 1993. Facsimile cover sheet. June 14, 1993. Akzo Chemicals Inc., Chicago, IL.
 

*Anonymous. 1967. Mineral oil in human tissues. Nutr Rev 25:46-49.
 

*ASTM. 1966. Fire Resistance of Hydraulic Fluids. American Society for Testing and Materials,
 

Philadelphia, PA..
 

*ATSDR. 1989. Decision guide for identifying substance-specific data needs related to toxicological 

profiles. Agency for Toxic Substances and Disease Registry, Division of Toxicology, Atlanta, GA. 

*ATSDR. 1993a. Technical report on ethylene glycol and propylene glycol. Agency for Toxic Substances 

and Disease Registry, Division of Toxicology, Atlanta, GA. 

*Cited in text 
HYDRAULIC FLUIDS 318 

8. REFERENCES 

*ATSDR. 1993b. Toxicological Profile for PCBs. Agency for Toxic Substances and Disease Registry,
 

Division of Toxicology, Atlanta, GA.
 

*ATSDR. 1993c. Case studies in environmental medicine - cholinesterase inhibiting pesticide toxicity.
 

Agency for Toxic Substances and Disease Registry, Division of Toxicology, Atlanta, GA.
 

*ATSDR. 1995. Toxicological profile for automotive gasoline. Agency for Toxic Substances and Disease
 

Registry, Division of Toxicology, Atlanta, GA.
 

*ATSDR/CDC. 1990. Subcommittee report on biological indicators of organ damage. Agency for Toxic
 

Substances and Disease Registry, Centers for Disease Control and Prevention, Atlanta, GA.
 

*Baldridge HD, Jenden DJ, Knight CE, et al. 1959. Toxicology of a triaryl phosphate oil. Arch Ind Health
 

20:86-88.
 

*Banerjee BD, Saha S, Ghosh KK, et al. 1992. Effect of tricresyl phosphate on humoral and cell-mediated
 

immune responses in albino rats. Bull Environ Contam Toxicol 49:3 12-317.
 

*Barnard PWC, Bunton CA, Llewellyn DR, et al. 1961. The reactions of organic phosphate: Part V. The
 

hydrolysis of triphenyl and trimethyl phosphates. J Chem Sot 2670-2676.
 

*Barnes DG, Dourson M. 1988. Reference dose (RfD): Description and use in health risk assessments.
 

Regul Toxicol Pharmacol8:471-486.
 

*Baron RL. 1981. Delayed neurotoxicity and other consequences of organophosphate esters. Ann Rev
 

Entomol26:29-48.
 

*Bates TS, Hamilton SE, Cline JP. 1984. Vertical transport and sedimentation of hydrocarbons in the
 

central main basin of Puget Sound, Washington. Environ Sci Technol 18:299-305.
 

*Beck BE, Wood CD, Whenham GR. 1977. Triaryl phosphate poisoning in cattle. Vet Path01 14:128-137.
 

*Bollinger JN. 1970. Metabolic fate of mineral oil adjuvants using 14C-labeled tracers. I. Mineral Oil. J
 

Pharm Sci 59:1084-1088.
 

*Bouldin TW, Cavanagh JB. 1979a. Organophosphorus neuropathy. I. A teased-fiber study of the 

spatio-temporal spread of axonal degeneration. Am J Path01 94:241-252. 

*Bouldin TW, Cavanagh JB. 1979b. Organophosphorus neuropathy. I. A fine-structural study of the early 

stages of axonal degeneration. Am J Path01 94:253-270. 

*Brinkerhoff CR, Sharma RP, Boucier DR. 1981. The effects of Tri-ortho-tolyl Phosphate (TOTP) on the 

immune system of mice. Ecotoxicology and Environmental Safety 5:368-376. 

*Brunton LL. 1985. Laxatives. In: Gilman AG, Goodman LS, Rall TW, et al., eds. The Pharmacological 

Basis of Therapeutics. New York: MacMillan Publishing Company, 994-1003.
 

*Camarasa JG, Serra-Baldrich E. 1992. Allergic contact dermatitis from triphenyl phosphate. Contact
 

Dermatitis 26:264-265.
 
HYDRAULIC FLUIDS 319 

8. REFERENCES 

*Cannon PR. 1940. The problem of lipid pneumonia. J Am Med Assoc. 115:2 176-2179. 

*Carlsen L, Andersen KE, Egsgaard H. 1986. Triphenyl phosphate allergy from spectacle frames. Contact 

Dermatitis 15:274-277. 

*Carlton BD, Basaran AH, Mezza LE, et al. 1987. Examination of the reproductive effects of tricresyl
 

phosphate administered to Long-Evans rats. Toxicology 46:321-328.
 

*Carpenter HM, Jenden DJ, Shulman NR, et al. 1956. The toxicology of cellulube 220: III Experimental
 

Toxicology Research Report. Naval Medical Research Institute, National Naval Medical Center 14:725-760.
 

*Carpenter HM, Jenden DJ, Shulman NR, et al. 1959. Toxicology of a triaryl phosphate oil: I. Experimental
 

toxicology. Arch Ind Health 20:62,234-252.
 

*Carrington CD, Burt CT, Abou-Donia MB. 1988. In viva 3 1 P nuclear magnetic resonance studies on the
 

absorption triphenyl phosphate and tri-or&-cresyl phosphate following subcutaneous administration in
 

hens. Drug Metab Distrib 104- 109.
 

*Carrington CD, Lapadula DM, Othman M, et al. 1989. Assessment of the delayed neurotoxicity of tributyl
 

phosphate, tributoxyethyl phosphate, and dibutylphenyl phosphate. Toxicol Ind Health 6 (3/4):415-423.
 

*CAS. 1995. Chemical Abstract Service. On-line database. May 13, 1995.
 

*Casida JE, Eto M, Baron RL. 196 1. Biological activity of a tri-ortho-cresyl phosphate metabolite. Nature
 

191:1396-1397.
 

*Cautreels W, VanCauwenberghe K. 1978. Experiments on the distribution of organic pollutants between
 

airborne particulate matter and the corresponding gas phase. Atmos Environ 12: 1133- 114 1.
 

*Cavanagh JB, Patangia GN. 1965. Changes in the central nervous system in the cat as the result of triorthocresyl phosphate poisoning. Brain 88: 165-l 80.
 

*CELDS. 1992. Computer Aided Environmental Legislative Data System. February 1992.
 

*Chapin RE, George JD, Lamb JC IV. 1988. Reproductive toxicity of tricresyl phosphate in a continuous
 

breeding protocol in Swiss (CD-l) Mice. Fundam Appl Toxicol 10:344-354.
 

*Chapin RE, Phelps JL, Burka LT, et al. 1991. The effects of tri-ortho-cresyl phosphate and metabolites on
 

rat Sertoli cell function in primary culture. Toxicol Appl Pharmacol 108:194-208.
 

*Chapin RE, Phelps JL, Somkuti SG, et al. 1990. The interaction of sertoli and leydig cells in-the testicular
 

toxicity of tri-ortho-cresyl phosphate. Toxicol Appl Pharmacol 104:483-495.
 

*ChemID. 1993. On-line database. May 1933.
 

*Chemiak MG. 1988. Toxicological screening for organophosphorus-induced delayed neurotoxicity:
 

Complications in toxicity testing. Neurotoxicology 9:249-272.
 

*Chevron. 1994. Tributyl Phosphate. Chevron International Oil Company, San Francisco, CA.
 
HYDRAULIC FLUIDS 320 

8. REFERENCES

 *Chrisope DR, Landry JF. 1993. Automatic transmission fluid. In: Shubkin RL, ed. Synthetic Lubricants 

and High Performance Functional Fluids. New York: Marcel Dekker, Inc., 35 1-364. 

*Ciba-Geigy. 1984e. TSCA sect. S(d) submission no. 86-870000078. Hydrolysis report with cover letter 

dated 01/09/87. Washington, DC: Office of Toxic Substances, U.S. Environmental Protection Agency. 

Microfiche no. 5 13263. 

*Ciba-Geigy. 1986. TSCA sec. 8(d) submission no. 86-870000077. Ecotoxicology of phosphate esters. 

Testing to OECD guidelines, 1982. Washington, DC: Office of Toxic Substances, U.S. Environmental 

Protection Agency. Microfiche no. 5 13262. 

*Ciba-Geigy Ltd. 1973. Pydraul50E: Neurotoxicity study in domestic hens. Ciba-Geigy Limited, Basle, 

Switzerland. 

*Ciba-Geigy Ltd. 1978a. Salmonella/mammalian-microsome mutagenicity test with TK 10 509 (REOFOS 

95). Experiment No. 78-2506. Ciba-Geigy Limited, Basle, Switzerland. NTIS OTS0507280. 

*Ciba-Geigy Ltd. 1978b. Salmonella/mammalian-microsome mutagenicity test with TK 10507 (REOFOS 

50) with cover letter from J.L. Greig. Experiment No. 78-2507. Ciba-Geigy Limited, Basle, Switzerland. 

NTIS/OTS0507280. 

*Ciba-Geigy Ltd. 1983a. Salmonella/mammalian-microsome mutagenicity test TK 12 477 (REOLUBE 

HYD46). Project No. 830209. Ciba-Geigy Limited, Basle, Switzerland. 

*Ciba-Geigy Ltd. 1983b. Sister chromatid exchange studies on somatic cells of Chinese hamsters TK 12 

477 (REOLUBE HYD46). Test No. 830211. Ciba-Geigy Limited, Basle, Switzerland. 

*Ciba-Geigy Ltd. 1984a. Nucleus anomaly test in somatic interphase nuclei of Chinese hamster TK 10 507 

(REOFOS 50) Test No. 830071. Ciba-Geigy Ltd, Basle, Switzerland. NTIS OTS0507280. 

*Ciba-Geigy, Ltd. 1984b. Sister chromatid exchange studies on somatic cells of Chinese hamsters TK 10 

507 (REOFOS 50) Test No. 830206. Ciba-Geigy Ltd, Basle, Switzerland. NTIS OTS0507280. 

*Ciba-Geigy Ltd. 1984~. Autoradiographic DNA repair test on rat hepatocytes TK 12 477 (REOLUBE 

HYD46) Test No. 830208. Ciba-Geigy Ltd, Basle, Switzerland. 

*Ciba-Geigy Ltd. 1984d. Autoradiographic DNA repair test on rat hepatocytes TK 10 507 (REOFOS 50) 

Test No. 830205. Ciba-Geigy Ltd, Basle, Switzerland. NTIS OTS0507280. 

*Ciba-Geigy Ltd. 1985. In vitro absorption through human epidermis of Reofos 50 and Reolube with cover 

letter dated October 16, 1985. EPA/OTS Public Files. NTIS OTS05 12802. -. 

*Ciba-Geigy Ltd. 1986. Ecotoxicology of phosphate ester with cover letter dated January 9, 1987. 

EPA/OTS Public Files. NTIS OTS05 13262. 

*Collins JM. 1993. Automotive trends. In: Shubkin RL, ed. Synthetic Lubricants and High-Performance 

Functional Fluids. New York: Marcel Dekker, Inc., 493-508. 
HYDRAULIC FLUIDS 321 

8. REFERENCES
 

*Coye MJ, Lowe JA, Maddy KT. 1986. Biological monitoring of agricultural workers exposed to pesticides: 

I. Cholinesterase activity determinations. J Occup Med 28:619-627. 

*Cregler LL, Mark H. 1986. Medical complications of cocaine abuse. New Engl J Med 315:1495-1500. 

*Dannecker W, Schroeder B, Stechmann H. 1990. Organic and inorganic substances in highway tunnel 

exhaust air. Sci Total Environ 93:293-300. 

*Dawson RB, Platteau C. 1993. Industrial trends. In: Shubkin RL, ed. Synthetic Lubricants and 

High-Performance Functional Fluids. New York: Marcel Dekker, Inc., 509-524. 

*Deleon IR, Byrne CJ, Peuler EA, et al. 1986. Trace organic and heavy metal pollutants in the Mississippi 

River. Chemosphere 15:795-805. 

*Dee PD, Howard PH. 1978. Combined gas-liquid chromatographic mass spectrometric analysis of some 

commercial aryl phosphate oils. J Assoc Off Anal Chem 61:266-270. 

*Department of Defense. 1993. Military handbook: Design guide for military applications of hydraulic 

fluids. Department of Defense. MIL-HKBK-118. 

*Dollahite JW, Pierce KR. 1969. Neurologic disturbances due to triaryl phosphate toxicity. Am J Vet Res 

30:1461-1464. 

*Dray BF. 1993. Environmental impact. In: Shubkin RL, ed. Synthetic Lubricants and High-Performance 

Functional Fluids. New York: Marcel Dekker, Inc., 533-543. 

*Eade NR, Taussig LM, Marks MI. 1974. Hydrocarbon pneumonitis. Pediatrics 54:35 l-357. 

*Ebert AG, Schleifer CR, Hess SM. 1966. Absorption, disposition and excretion of 3Hmineral oil in rats. 

J Pharm Sci 55:923-929. 

*Ecobichon DJ. 1991. Toxic effects of pesticides. In: Casarett and Doull’s Toxicology. 4th ed. New York: 

Macmillan, 565-622. 

*EPA. 1978. Environmental Protection Agency. Preliminary report on aryl phosphate monitoring with 

attachment. Intra-Agency memorandum from A.B. Crockett, Environmental Monitoring and Support 

Laboratory, Office of Research and Development to M.P. Halper, Monitoring and Data Support. 

*EPA. 1979. Technical grade products manufactured in 1979, Table II. Washington, DC: U.S. 

Environmental Protection Agency, 4. 

*EPA. 1979a. Environmental Protection Agency. Analysis of aryl phosphate samples. IntrGkgency 

memorandum from A.B. Crockett, Environmental Monitoring and Support Laboratory, Office of Research 

and Development to P. Hilgard, Office of Toxic Substances. 

*EPA. 1979b. U.S. Environmental Protection Agency. Designation of conventional pollutants. 40 CFR 

401.16. Fed Regist 44:44501. 
HYDRAULIC FLUIDS 322 

8. REFERENCES 

*EPA. 1989. Interim methods for development of inhalation reference doses. U.S. Environmental 

Protection Agency. EPA/600/8-90/066F. 

*EPA. 1990. Interim methods for development of inhalation reference doses. U.S. Environmental 

Protection Agency. EPA-600/8-90/066A.
 

*EPA. 1992. Environmental Protection Agency. Code of Federal Regulations. 40 CFR part 704 and 799.
 

*EPA. 1992a. Environmental Protection Agency. Hazardous waste management system: Identification and
 

listing of hazardous waste; recycled used oil management standards; final rule. Fed Regist 57:41566-41626.
 

*EPA. 1992b. Environmental Protection Agency. Aryl phosphate base stocks; proposed text rule including
 

reporting and recordkeeping requirements. Fed Regist 57:2138-2158.
 

*EPA. 1994. Testing Consent Order for Aryl Phosphate Base Stocks. September 27, 1994.
 

*EPA. 1995. Environmental Protection Agency. Code of Federal Regulations. 40 CFR 261-60 FR 6054.
 

*Eta M, Casida JE, Eto T. 1962. Hydroxylation and cyclization reactions involved in the metabolism of trior&­

cresyl phosphate. Biochem Pharmacol 11:337-352.
 

*Eto M, Oshima Y, Casida JE. 1967. Plasma albumin as a catalyst in cyclization of diaryl-o(-hydroxy)-tolyl
 

phosphates. Biochem Pharmacol 16:295-308.
 

*Evans RT. 1986. Cholinesterase phenotyping: Clinical aspects and laboratory applications. CRC Crit Rev
 

Clin Lab Sci 23:35-64.
 

*Ferrario JB, Deleon IR, Tracy RE. 1985b. Evidence for toxic anthropogenic chemicals in human
 

thrombogenic coronary plaques. Arch Environ Contam Toxicol 14:529-234.
 

*Ferrario JB, Lawler GC, Deleon IR, et al. 1985a. Volatile organic pollutants in biota and sediments of Lake
 

Pontchartrain. Bull Environ Contam Toxicol 34:246-255.
 

*FMC. 1975. Gas chromatographic-mass spectral assay of Kronitex isopropylphenyl phosphates. Technical
 

report no. CPG-75-10. FMC Corporation, Princeton, NJ.
 

*FMC. 1977a Neurotoxicity study in hens on commercially available phosphate ester products: II.
 

Monsanto. ICD/T-77-047. FMC Corporation, Princeton, NJ, 1-17.
 

*FMC. 1977b. A neurotoxicity study in hens on commercially available phosphate ester products: I.
 

Stauffer. ICD/T-77-040. FMC Corporation, Princeton, NJ, l-l 1. (submitted for peer review),.
 

*FMC. 1977~. Aryl phosphates and phenols in Nitro area samples. Memorandum from J.E. Jadlocki, FMC
 

Corporation Industrial Division to W.H. Kibble, FMC Corporation.
 

*FMC. 1978a. Acute oral toxicity of Pydraul50E. ICG/T-78-085. FMC Corporation, Princeton, NJ, l-5.
 

*FMC. 1978b. Part of unidentified submission (exhibit G): Environmental fate of triaryl phosphate
 

[microfiche 05 192591. FMC Corporation, Philadelphia, PA. 
HYDRAULIC FLUIDS 323 

8. REFERENCES
 

*FMC. 1979. Analysis of aryl phosphates and phenols in plant and environmental samples from Nitro, West
 

Virginia. Technical report [microfiche 05 183991. FMC Corporation, Princeton, NJ, 95.
 

*FMC. 1980. The environmental fate and effects of aryl phosphates and phenolics in wastewaters from the
 

production of Kronitex phosphate esters. Technical report [microfiche 05 183991. FMC Corporation,
 

Princeton, NJ, 42.
 

*FMC. 1986. The subchronic (90-day) neurotoxicity study of (X096-126-1 phosphate ester to the domestic
 

hen. FCC 45/84526. FMC Corporation, Philadelphia, PA.
 

*FMC. 1990a. Non-definitive acute oral toxicity study of Durad 110 in rats. Study No. 190-l 143. FMC
 

Corporation, Princeton, NJ.
 

*FMC. 1990b. Letter from FMC Corp to U.S. EPA containing preliminary study results for triaryl
 

phosphates. EPA/OTS public files: 86-900000502. FMC Corporation, Princeton, NJ. NTIS OTS0530040.
 

*FMC. 1991 a. The effects of Durad 125 on serum cholinesterase and brain neuropathy. Target esterase
 

activity in male Long-Evans rats. Study No: 64460. FMC Corporation, Princeton, NJ.
 

*FMC. 1991 b. Durad 125. Non-definite primary skin irritation study in rabbits. FMC Corporation,
 

Princeton, NJ.
 

*FMC. 1991~. Material safety data for Durad 300 (triaryl phosphate). FMC Corporation, Princeton, NJ.
 

*FMC. 1991 d. Material safety data for Durad 110 (triaryl phosphate). FMC Corporation, Princeton, NJ.
 

*FMC. 1992a. Letter submitting two enclosed non-definitive acute oral toxicity studies of Durad 550B with
 

attachments. FMC Corporation, Princeton, NJ.
 

*FMC. 1992b. Durad 550B. Salmonella/mammalian-microsome plate incorporation mutagenicity assay
 

(Ames Test). Study No. 19 1 - 1222. FMC Corporation, Philadelphia, PA.
 

*FMC. 1992c. Material Safety Data Sheet: Durad 550B. FMC Corporation, Princeton, NJ. July 13, 1992.
 

*FMC. 1992d. Material Safety Data Sheet: Durad MP 280B. FMC Corporation, Princeton, NJ. July 13,
 

1992.
 

*FMC. 1992e. Material Safety Data Sheet: Durad (R) 220B. FMC Corporation, Princeton, NJ. July 13,
 

1992.
 

*FMC. 1992f. Material Safety Data Sheet: Durad (R) 125. FMC Corporation, Princeton, NL. July 13, 1992
 

*FMC. 1994. Material Safety Data Sheet: Durad 220. FMC Corporation, Princeton, NJ. January 1, 1994.
 

*FMC. 1995. Material Safety Data Sheet: Durad 280B. FMC Corporation, Princeton, NJ. January 1, 1995.
 

*Francis AJ, Iden CR, Nine BJ, et al. 1980. Characterization of organics in leachates from low-level
 

radioactive waste disposal sites. Nuclear Technol50:158-163.
 
HYDRAULIC FLUIDS 324 

8. REFERENCES 

*Freitag D, Ballhom L, Geyer H, et al. 1985. Environmental hazard profile of organic chemicals. 

Chemosphere 14:1589-1616. 

*Freudenthal RI, Rausch L, Gerhart JM. 1993. Subchronic Neurotoxicity of Oil formulations containing 

either Tricresyl Phosphate or Tri-Orthocresyl Phosphate. Journal of the American College of Toxicology 

12(4):409-416. 

*Friess, SL, Jensen DJ, Tureman, JR. 1959. Toxicology of a triaryl phosphate oil. II. A quantitative study 

of toxicity in different production batches. Arch Ind Health 20:253-261. 

*Gatz. 1992a. Intravenous and dermal absorption, distribution, and excretion of 14C-tributyl phosphate in 

Yucatan minipigs: Part I. MRI Project No. 9526-F(02). 

*Gatz. 1992b. Pharmacokinetics of TBP in rats: Section 1 distribution, metabolism, and excretion of 

i4C-tributyl phosphate. MRI Project No. 9526-F. 

*Gatz. 1994. Metabolism of tributyl phosphate in Yucatan minipigs following intravenous and dermal 

exposure: Part Il. MRI Project No. 9526-02. 

*Gaworski CL, Kinkead ER, Horton JR, et al. 1986. Comparative studies of the short-term toxicity of the 

hydraulic fluids MIL-H-l 9457C, MIL-H- 19457B, and MIL-H-22072B. Harry G. Armstrong Aerospace 

Medical Research Laboratory, Wright-Patterson Air Force Base, OH. NTIS/AD-Al 72 172/9. 

*Gerarde HW. 1963. Toxicological studies on hydrocarbons. IX. The aspiration hazard and toxicity of 

hydrocarbon mixtures. Arch Environ Health 6:329-341. 

*Giurini JM, Hopkins WE, Redner T, et al. 1986. Succinylcholine sensitivity and plasma cholinesterase 

deficiency. J Foot Surgery 25:382-385. 

*Goldstein DA, McGuigan MA, Ripley BD. 1988. Acute tricresylphosphate intoxication in childhood. 

Human Toxicol, 7:179-l 82. 

*Gunderson EL. 1988. FDA total diet study, April 1982-April 1984, dietary intakes of pesticides, selected 

elements and other chemicals. J Assoc Off Anal Chem 7 1: 1200- 1209. 

*Haines JR, Alexander M. 1974. Microbial degradation of high-molecular weight alkanes. Appl Microbial 

28:1084-1085. 

*Hatton RE. 1962. Water-base Fluids. In: Hydraulic Fluids. New York: Reinhold Publishing Corporation 

131273-287. 

*HazDat. 1996. Database. Agency for Toxic Substances and Disease Registry (ATSDR), Atlanta, GA. 

*Healy CE, Beyrouty PC, Broxup BR. 1995. Acute and subchronic neurotoxicity studies with tri-n-butyl 

phosphate in adult Sprague-Dawley rats. Am Ind Hyg Assoc, 56:349-355. 

*Healy CE, Nair RS, Lemen JK, et al. 1991. Subchronic and reproduction studies with dibutyl phenyl 

phosphate in Sprague-Dawley rats. Fundam Appl Toxicol 16: 117-l 27. 
HYDRAULIC FLUIDS 325 

8. REFERENCES
 

*Healy CE, Nair RS, Ribelin WE, et al. 1992. Subchronic rat inhalation study with Skydrol500B-4 fire 

resistant hydraulic fluid. Am Ind Hyg Assoc J 53: 175-180. 

*Heitkamp MA, Freeman JP, Ceringlia CE. 1986. Biodegradation of tert-butylphenyl diphenyl phosphate. 

Appl Environ Microbial 5 1:3 16-322. 

*Heitkamp MA, Huckins JN, Petty JD, et al. 1984. Fate and metabolism of isopropylphenyl diphenyl 

phosphate in freshwater sediments. Environmental Science and Technology 18:434-439. 

*Henrich RT. 1995. Toxicology profile for hydraulic fluids. Comments of Akzo Nobel Chemicals Inc. 

Akzo Nobel Chemical Inc. Dobbs Ferry, NY. 

*Hesselberg RJ, Seelye JG. 1982. Identification of organic compounds in Great Lakes fishes by gas 

chromatography/mass spectrometry: 1977. Admen Report No. 82-l. Ann Arbor, MI: U.S. Fish and Wildlife 

Society Great Lakes Fishery Laboratory, 49. 

*Hedge HC, Sterner JH. 1943. The skin absorption of triorthocresyl phosphate as shown by radioactive 

phosphorus. J Pharmacol Exp Ther 79:225-234. 

*Hoffman RS, Henry GC, Howland MA, et al. 1992. Association between life-threatening cocaine toxicity 

and plasma cholinesterase activity. Ann Emerg Med 2 1:248-253 

*Houghton. 1992. Material Safety Data Sheet: Houghton-Safe 5047-F. March 24, 1992 

*Howard PH, Deo PG. 1979. Degradation of aryl phosphates in aquatic environments. Bull Environ 

Contam Toxicol 22:337-344. 

*HSDB. 1995. Hazardous Substances Data Bank. National Library of Medicine, National Toxicology 

Information Program, Bethesda MD. February 1995. 

*Huckins JN, Fairchild JF, Boyle TP. 1991. Role of exposure mode in the bioavailability of triphenyl 

phosphate to aquatic organisms. Arch Environ Contam Toxicol 21:48 l-485. 

*Hutchinson TC, Hellebust JA, Tam D et al. 1980. The correlation of the toxicity to algae of hydrocarbons 

and halogenated hydrocarbons with their physical-chemical properties. In: Afghan BK, MacDay D, eds. 

Hydrocarbons and Halogenated Hydrocarbons in the Aquatic Environment. New York: Plenum Press, 

577-586. 

*IARC. 1984. Carbon blacks, mineral oils, (lubricant base oils and derived products) and some nitroarenes. 

IARC Monogr Eva1 Carcinog Risk Chem Hum 33:86-167. 

*Inui K, Mitsumori K, Harada T, et al. 1993. Quantitative analysis of neuronal damage induced by 

tri-ortho-cresyl phosphate in Wistar rats. Fundam Appl Toxicol 20: 11 l-l 19. 

*IRDC. 1981. Teratology study in rats. International Research and Development Corporation. Mattawan, 

Michigan U.S.A. 

*Jarvholm B, Johansson B, Lavenius B, et al. 1986. Exposure to triarylphosphate and polyneuropathy: A 

case report. Am J Ind Med 9:56 l-566. 
HYDRAULIC FLUIDS 326 

8. REFERENCES 

*Johannsen FR, Wright PL, Gordon DE, et al. 1977. Evaluation of Delayed Neurotoxicity and 

Dose-Response Relationships of Phosphate Esters in the Adult Hen. Toxicol Appl Pharmacol, 41:29 l-304. 

*Johnson MK. 1975. The delayed neuropathy caused by some organophosphorus esters: Mechanism and 

challenge. Crit Rev Toxicol 3:289-3 16. 

*Johnson MK. 1982. The target for initiation of delayed neurotoxicity by organophosphorus esters: 

biochemical studies and toxicological applications. In: Hodgson E, Bend JR, Philpot, RM, eds. Reviews of 

biochemical toxicology, Vo14. New York: Elsevier, 141-212. 

*Johnson MK. 1990. Organophosphates and delayed neuropathy: Is NTE alive and well? Toxicol Appl 

Pharmacol 102:355-399: 

*Johnson MK, Barnes JM. 1970. Age and the sensitivity of chicks to the delayed neurotoxic effects on some 

organophosphorus compounds. Biochem Pharmacol19:3045-3047. 

*Julian RJ, Galt DE, Butler D. 1976. Diagnosis of triorthocresyl phosphate poisoning in cattle. Proceedings 

of the Annual Meeting of the American Association of Veterinary Laboratory Diagnostics 18:407-418. 

*Karydis M. 1980 Uptake of hydrocarbons by the marine diatom Cyclotella cryptica. Microbiological 

Ecology 5:287-293. 

*Kawamura K, Kaplan IR. 1983. Organic compounds in the rainwater of Los Angeles. Environ Sci Technol 

17:497-501. 

*Keith LH, Garrison AW, Allen FR, et al. 1976. Identification of organic compounds in drinking water from 

thirteen U.S. cities. In: Keith LH, ed. Advances in identifying and analyzing organic pollution in water. Ann 

Arbor, MI: Ann Arbor Press, 329-373. 

*Kinkead E, Kimmel E, Wall H, et al. 1990. Determination of the toxicity of cyclotriphosphazene hydraulic 

fluid by 2 1 -day repeated inhalation and dermal exposure. Am Ind Hyg Assoc J 5 1:583-587. 

*Kinkead ER, Bashe WJ. 1987. Evaluation of the inhalation and skin absorption kinetics of a 

cyclotriphosphazene based hydraulic fluid. Report to Toxic Hazards Division of Aerospace Medical 

Research Laboratory, Wright-Patterson Air Force Base, OH. LR-86-03. February 1987. 

*Kinkead ER, Bunger SK, Wolfe RE. 1992c. Acute toxicologic evaluation of a cyclotriphosphazene 

hydraulic fluid. Acute Toxicity Data 1:2 19. 

*Kinkead ER, Bunger, SK Wolfe RE. 1992e. Irritation and sensitization evaluation of Fyrquel220 

hydraulic fluid. 2 12-2 13. -. 

*Kinkead ER, Culpepper BT, Henry SS. 1989~. Determination of the toxicity of cyclotriphosphazene 

hydraulic fluid by 2 1 -day repeated dermal exposure. Harry G. Armstrong Aerospace Medical Research 

Laboratory Technical Report AAMRL-TR-89-022,214-223 

*Kinkead ER, Culpepper BT, Henry SS, et al. 1988. Evaluation of the acute toxicity of four water-in-oil 

emulsion hydraulic fluids. Harry G. Armstrong Aerospace Medical Research Laboratory Technical Report 

AAMRL-TR-87-063, l-42. 
HYDRAULIC FLUIDS 327 

8. REFERENCES
 

*Kinkead ER, Culpepper BT, Henry SS, et al. 1989a. Determination of the toxicity of cyclotriphosphazene 

hydraulic fluid by 2 1 -day repeated inhalation exposure. Harry G. Armstrong Aerospace Medical Research 

Laboratory Technical Report AAMRL-TR-89-022,224-230. 

*Kinkead, ER, Culpepper BT, Pollard DL, et al. 1987a. The evaluation of the acute toxicity of four 

water-in-oil emulsions hydraulic fluids. Harry G. Armstrong Aerospace Medical Research Laboratory 

Technical Report AAMRL-TR-87-020, 14-22. 

*Kinkead ER, Henry SS, Culpepper BT, et al. 1989b. Evaluation of the acute delayed neurotoxicity of four 

shipboard hydraulic fluids. Harry G. Armstrong Aerospace Medical Research Laboratory Technical Report 

AAMRL-TR-89-022,242-248. 

*Kinkead ER, Henry SS, Leahy HF, et al. 198713. Evaluation of the acute toxicity of a synthetic 

polyalphaolefin-based hydraulic fluid. 23-32. 

*Kinkead ER, Horton JR, Gaworski CL. 1985. Acute toxicity studies on two air force hydraulic fluids 

(ML0 82-233 and ML0 82-585). Harry G. Armstrong Aerospace Medical Research Laboratory Technical 

Report AAMRL-TR-85-070. 

*Kinkead ER, Wolfe RE, Bunger SK, et al. 1991. Evaluation of the toxic effects of a 90-day continuous 

exposure of rats to water-in-oil hydraulic fluid emulstions. Harry G. Armstrong Aerospace Medical Research 

Laboratory Technical Report AL-Tr- 1991-0 15 NMRI-9 l-90. 

*Kinkead ER, Wolfe RE, Bunger SK. 1992a. Acute toxicologic evaluation of Fyrquel220 hydraulic fluid. 

Acute Toxicity Data 1:2 10. 

*Kinkead ER, Wolfe RE, Bunger SK. 1992d. Irritation and sensitization evaluation of Durad MP280 

hydraulic fluid. Acute Toxicity Data 1:2 11. 

*Kinkead ER, Wolfe RE, Bunger SK, et al. 1992b. The acute toxicity evaluation of a low-temperature 

hydraulic fluid. J Am Ind Hyg Assoc 53:163-168. 

*Klein BL, Simon JE. 1986. Hydrocarbon poisonings. Pediatr Clin North Am 33:411-419. 

*Konasewich D, Traversy W, Zar H. 1978. Status report on organic and heavy metal contaminants in the 

Lakes Erie, Michigan, Huron and Superior basins. Great Lakes Water Quality Board. 

*Kurebayashi H, Tanaka A, Yamaha T. 1985. Metabolism and disposition of the flame retardant plasticizer, 

tri-p-cresyl phosphate, in the rat. Toxicol Appl Pharmacol77: 395-404. 

*Labour Canada. 1990. Evaluation of health hazards associated with occupational exposure>? Skydrol 

hydraulic fluids with attachments, cover sheet, and letter dated 02/01/90. EPA/OTS Public files: 

86-900000073. Monsanto Company, St. Louis, MO. NTIS OTS0522305. 

*Laham S, Long G, Broxup B. 1984. Subacute oral toxicity of Tri-n-butyl Phosphate in the 

Sprague-Dawley rat. J Appl Toxicol 4(3): 150-154. 

*Laham S, Long G, Broxup B. 1985. Induction of urinary bladder hyperplasia in Sprague-Dawley rats 

orally administered Tri-n-butyl Phosphate. Archives of Environmental Health 302-301-306. 
HYDRAULIC FLUIDS 328 

8. REFERENCES
 

*Latendresse JR, Brooks CL, Capen CC. 1994. Pathologic effect of butylated triphenyl phosphate-based 

hydraulic fluid and tricresyl phosphate on the adrenal gland, ovary, and testis in the Fischer-344 Rat. Toxicol 

Path 22 (4):341-352. 

*Latendresse JR, Brooks CL, Flemming CD, et al. 1994. Reproductive toxicity of butylated triphenyl 

phosphate and tricresyl phosphate fluids in F344 Rats. Fundam Appl Toxicol 22:392-399. 

*LeBel GL, Williams DT. 1983. Determination of organic phosphate triesters in human adipose tissue. J 

Assoc Off Anal Chem 66:69 1-699. 

*LeBel GL, Williams DT. 1986. Levels of triaryl/alkyl phosphates in human adipose tissue from Eastern 

Ontario. Bull Environ Contam Toxicol 37:41-46. 

*LeBel GL, Williams DT, Benoit FM. 1981. Gas chromatographic determination of trialkyl/aryl phosphates 

in drinking water following isolation using macroreticular resin. J Assoc Off Anal Chem 64:991-998. 

*Lide DR. 1994. Handbook of Chemistry and Physics. CRC Press Boca Raton London Tokyo. 

3-398-3-399. 

*Liu D. 1980. Fate of petroleum hydrocarbons in sewage sludge after land disposal. Bull Environ Contam 

Toxicol 25:616-622. 

*Lombard0 P, Egry IJ. 1979. Identification and gas-liquid chromatographic determination of aryl phosphate 

residues in environmental samples. J Assoc Off Anal Chem 62:47-5 1. 

*Lotti M, Becker CE, Aminoff MJ. 1984. Organophosphate polyneuropathy: Pathogenesis and’prevention. 

Neurology 34:658-662. 

*Lushbaugh CC, Green JW, Redemann CE. 1950. Effects of prolonged inhalation of oil fogs on 

experimental animals. Arch Ind Hyg Occup Med 1:237-247. 

*Lyman WJ, Reehl WF, Rosenblatt DH. 1982. Handbook of Chemical Property Estimation Methods: 

Environmental behavior of organic compounds. New York: McGraw-Hill Book Company, l- 1 to l-2. 

*MacEwen JD, Vemot EH. 1983. Toxic Hazards Research Unit Annual Technical Report: 1983. Air Force 

Aerospace Medical Research Laboratory. AFAMRL-TR-83-64. NTIS AD-136170. 

*MacEwen JD, Vemot EH. 1985. Toxic Hazards Research Unit Annual Report: 1985. Harry G. Armstrong 

Aerospace Medical Research Laboratory AAMRL-TR-85-058. NTIS AD-A161558, 144-158. 

*Mandel JS, Berlinger NT, Kay N. 1989. Organophosphate exposure inhibits Non-Specific esterase staining in 

human blood monocytes. Amer J Industrial Med 15 :207-2 12. 

*Marino MP. 1992. Phosphate Esters. In: Shubkin RL, ed. Synthetic Lubricants and High-Performance 

Functional Fluids. New York: Marcel Dekker Inc. 67- 100. 

*Marino MP, Placek DG. 1994. Phosphate Esters. In: CRC Handbook of Lubrication and Tribology; 

Volume III: Monitoring, Materials, Synthetic Lubricants, and Applications, ed. E. Richard Booser. Boca 

Raton: CRC Press, Inc. 269-286. 
HYDRAULIC FLUIDS 329 

8. REFERENCES
 

*Maroni M, Bleecker ML. 1986. Neuropathy target esterase in human lymphocytes and platelets. J Appl 

Toxicol 6: l-7. 

*Matsumoto G. 1983. Changes in organic constituents in river water during incubation. Water Research 

17:1803-1810. 

*Mattie DR, Hoeflich TJ, Jones CE, et al. 1993. The Comparative Toxicity of Operational Air Force 

Hydraulic Fluids. Toxicol Ind Health 9(6):995-1016. 

*Mayer FL, Adams WJ, Finley MT, et al. 1981. Phosphate ester hydraulic fluids: An aquatic environmental 

assessment of Pydrauls 50E and 115E [Abstract]. American Society for Testing and Materials Special 

Technical Publication 838:103-123. CA/O96/137347V. 

*Merck Index. 1989. Merck index: An Encyclopedia of Chemicals, Drugs, and Biologicals. 11 th ed. 

Budavari S, ed. Rahway NJ: Merck & Co., Inc. 

*Minton NA, Murray VSG. 1988. A review of organophosphate poisoning. Med Toxicol 3:350-375. 

*Moller UJ. 1989. Hydraulic Fluids. In: Ullmann’s Encyclopedia of Industrial Chemistry, Vol Al 3,5th ed. 

165-176. 

*Monsanto. 1978. TSCA sect. 8(d) submission 40-7859047. A study of variables effecting the river 

die-away test. Special study 1978. Washington, D.C.: Office of Toxic Substances, U.S. Environmental 

Protection Agency. EPA Dot Control No. OTS 84003A 

*Monsanto. 1979. Summaries of mutagenicity studies, neurotoxicity studies, teratology studies, long term 

feeding studies, and 90-day inhalation studies on aryl phosphate ester products. 

*Monsanto. 1980. Evaluation of potential hazards by dermal contact. Test material: SH-79-007, Skydrol 

(R) 500B-4 Fire resistant hydraulic fluids. 

*Monsanto. 1981. Stability study of natural sediments samples preserved by frozen storage with attachment. 

Monsanto Company, St. Louis, MO. 

*Monsanto. 1983a. TSCA sect. 8(d) submission 8782 11865. Santicizer 154 river die-away biodegradation 

rate study [microfiche 2062271. Washington, D.C.: Office of Toxic Substances, U.S. Environmental 

Protection Agency. 

*Monsanto. 1983b. TSCA sect. 8(d) submission 878211112. Santicizer 141 river die-away biodegradation 

rate study [microfiche 2062271. Washington, D.C. Office of Toxic Substances, U.S. Environmental 

Protection Agency. -. 

*Monsanto. 1983~. TSCA sect. 8(d) submission 878211885. Biodegradability of t-butyl/phenyl phosphate 

mixtures [microfiche 2062271. Washington, D.C. Office of Toxic Substances, U.S. Environmental 

Protection Agency. 

*Monsanto. 1986a. Material Safety Data Sheet: Pydraul29ELT. Monsanto Company, St. Louis, MO. 

April 18,1986 
HYDRAULIC FLUIDS 330 

8. REFERENCES
 

*Monsanto. 1986b. Material Safety Data Sheet: Pydraul50E. Monsanto Company, St. Louis, MO.
 

January 3, 1986.
 

*Monsanto. 1986~. Material Safety Data Sheet: Pydraul90E. Monsanto Company, St. Louis, MO
 

April 18, 1986.
 

*Monsanto. 1987a. Three-month study of Skydrol500B-4 administered to male and female 

Sprague-Dawley rats by inhalation. Study No. 84049. Project No. ML-84-226. 

*Monsanto. 1987b. Three-month inhalation toxicity study of Skydrol500B-4 

*Monsanto. 1987~. In viva/in vitro neurotoxicity studies of Skydrol LD-4 in adult hens with mixtures of 

butyl diphenyl phosphate, dibutyl phenyl phosphate and tributyl phosphate. 

*Monsanto. 1987d. In vivoh vitro neurotoxicity studies of Skydrol500B-4. 

*Monsanto. 1988a. In vitro chromosome aberration with Skydrol500B-4 fire resistant hydraulic fluid study
 

on butyldiphenylphosphate, dibutylphenylphosphate and tributylphosphate.
 

*Monsanto. 1988b. In vitro cytogenetics study of Skydrol LD4 fire resistant hydraulic fluid. Study No.
 

87066. Project No. 87-57.
 

*Monsanto. 1989. Three-month inhalation toxicity study of Skydrol500B-4.
 

*Monsanto. 1992a. Material safety data for Skydrol500B-4 fire resistant hydraulic fluid. 9/l 5/92.
 

Monsanto Company, 800 North Lindbergh Boulevard, St. Louis, MO.
 

*Monsanto. 1992b. Material safety data for Skydrol LD-4 fire resistant hydraulic fluid. 9/l 5/92. Monsanto
 

Company, 800 North Lindbergh Boulevard, St. Louis, MO.
 

*Mortensen A, Ladefoged 0. 1992. Delayed neurotoxicity of trixylenyl phosphate and a trialkyl/aryl
 

phosphate mixture, and the modulating effect of atropine on tri-ortho-tolyl phosphate-induced neurotoxicity.
 

NeuroToxicology 13:347-354.
 

*Muir DCG. 1984. Phosphate esters. In: The Handbook of Environmental Chemistry: Anthropogenic
 

substances, Vol. 3. Germany: Springer-Verlag Berlin, 41-66.
 

*Muir DCG, Grift NP, Lockhart WL. 1982. Comparison of laboratory and field results for prediction of the
 

environmental behavior of phosphate esters. Environmental Toxicology and Chemistry 1: 113- 119.
 

*Muir DCG, Grift NP, Solomon J. 1981. Extraction and cleanup of fish, sediment, and water for
 

determination of triaryl phosphates by gas-liquid chromatography. J Assoc Off Anal Chem 64:79-84.
 

*Muir DCG, Lint D, Grift NP. 1985. Fate of three phosphate ester flame retardants in small ponds.
 

Environmental Toxicology and Chemistry. 4:663-675.
 

*Muir DCG, Townsend BE, Lockhart WL. 1983b. Bioavailability of six organic chemicals to Chironomus
 

tentans larvae in sediment and water. Environmental Toxicology and Chemistry 2:269-282.
 
HYDRAULIC FLUIDS 331 

8. REFERENCES
 

*Muir DCG, Yarechewski AL, Grift NP. 1983a. Environmental dynamics of phosphate esters: III. 

Comparison of the bioconcentration of four triaryl phosphates by fish. Chemosphere 12:155-166. 

*Murphy SD. 1986. Toxic effects of pesticides. In: Casarett and Doull’s toxicology, 3rd ed. 5 19-58 1. 

*Mutch E, Blain PG, Williams FM. 1992. Interindividual variations in enzymes controlling 

organophosphate toxicity in man. Hum Exp Toxicol 11: 109- 116. 

*NAS/NRC. 1989. Biologic markers in reproductive toxicology. National Academy of Sciences/National 

Research Council. Washington, DC: National Academy Press, 15-35. 

*Newton J. 1989. A look at lubricating oils. Industrial Lubrication and Tribology 41:13-15. 

*NFPA. 1991. Fire Protection Guide to Hazardous materials. 11 th ed. One Battrymarch Park, Quincy, MA. 

325-88.325-91. 

*NIOSH. 1989a. NIOSH Manual of Analytical Methods. Occupational air method no. 7905. NIOSH 

recommendations for occupational safety and health compendium of policy documents and statements. 

Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease 

Control, National Institute for Occupational Safety and Health. 

*NIOSH. 1989b. NIOSH Manual of Analytical Methods. Occupational air method no. 7300. NIOSH 

recommendations for occupational safety and health compendium of policy documents and statements. 

Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease 

Control, National Institute for Occupational Safety and Health. 

*NIOSH. 1989~. NIOSH Manual of Analytical Methods. Occupational air method no. 5037. NIOSH 

recommendations for occupational safety and health compendium of policy documents and statements. 

Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease 

Control, National Institute for Occupational Safety and Health. 

*NIOSH. 1992. NIOSH recommendations for occupational safety and health compendium of policy 

documents and statements. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health 

Service, Centers for Disease Control, National Institute for Occupational Safety and Health. NTIS 

PB92-162536. 

*Noda T, Mortia S, Ohgaki S. 1984. A Safety Evaluation of Chemicals Used in Household Products (V) 

Teratological Studies in 2-Ethylhexyl Diphenyl Phosphate in Rats. Annu Rep. Osaka City Inst. Public 

Health Environmental Science 46:82-88. 

*Nolting F, Behnke W, Zetzsch C. 1988. A smog chamber for studies of the reactions of terpenes and 

alkanes with ozone and OH. Journal of Atmospheric Chemistry 6:47-59. 

*Nomier AA, Abou-Donia MB. 1986. Studies on the metabolism of the neurotoxic tri-or&-cresyl 

phosphate: Synthesis and identification by infrared, proton nuclear magnetic resonance and mass 

spectrometry of five of its metabolites. Toxicology 38: l-l 3. 

*NPRA. 1992. 1991 Report on U.S. lubricating oil sales. National Petroleum Refiners Association, 

Washington, DC. 
HYDRAULIC FLUIDS 332 

8. REFERENCES 

*NTP. 1988. Unpublished report. (Cited in NTP 1994). 

*NTP. 1994. National Toxicology Program Technical report series no. 433. Tricresyl phosphate (CAS No. 

1330-78-5) in F344 rats and B6C3Fi mice (gavage and feed studies). Research Triangle Park, NC: U.S. 

Department of Health and Human Services, Public Health Service, National Institute of Health. NIH 

publication no. 84-2544. 

*Ofstad EB, Sletten T. 1985. Composition and water solubility determination of a commercial 

tricresylphosphate. Science of the Total Environment 43:233-241. 

*Oishi H, Oishi S, Hiraga K. 1982. Toxicity of Several Phosphoric Acid Esters in Rats. Toxicol Lett, 

13:29-34. 

*OSHA. 1974. U.S. Department of Labor. Occupational Safety and Health Administration. Code of 

Federal Regulations. 40 CFR 19 10.1000. Fed Regist 54:2948. 

*OTA. 1990. Neurotoxicology: Identifying and controlling poisons of the nervous system. Office of 

Technology Assessment, Washington, DC. OTA-BA-438. 

*Padilla S, Veronesi B. 1985. The relationship between neurological damage and neurotoxic esterase 

inhibition in rats acutely exposed to tri-ortho-cresyl phosphate. Toxicol Appl Pharmacol78:78-87. 

*Papay AG. 1989. Automatic-transmission fluids Dexron II and beyond. Lubrication Engineering 

45:121-128. 

*Papay AG. 1991. Formulating automatic-transmission fluids. Lubrication Engineering 47:271-275. 

*Papay AG. 1993. Hydraulics. In: Shubkin RL, ed. Synthetic Lubricants and High-Performance functional 

fluids. New York: Marcel Dekker, Inc., 427-452. 

*Peedicayil J, Ernest K, Thomas M, et al. 1991. The effect of organophosphorus compounds on serum 

pseudocholinesterase levels in a group of industrial workers. Hum Exp Toxicol 10:275-278. 

*Per1 CA, Hewitt TA, Vice DL, et al. 1985. Process and environmental considerations involved in the 

selection of hydraulic and lubrication fluids for a modem hot strip mill. Proceedings of the Industrial Waste 

Conference 40:121-132. 

*Perrot LJ, Palmer H. 1992. Fatal hydrocarbon lipoid pneumonia and pneumonitis secondary to automatic 

transmission fluid ingestion. J Forensic Sci 37:1422-1427. 

*Peterman PH, Delfino JJ, Dube DJ, et al. 1980. Chloro-organic compounds in the lower FoxRiver, 

Wisconsin. In: Afghan BK, Mackay D, eds. Hydrocarbons and halogenated hydrocarbons in the aquatic 

environment. New York: Plenum Press. 145-160. 

*Pickard MA, Whelihan JA, Westlake WS. 1975. Utilization of triaryl phosphates by a mixed bacterial 

population. Can J Microbial 24:140-145. 

*MA, Whelihan JA, Westlake WS. 1974. Utilization of triaryl phosphates by a mixed bacterial population. 

Can J Microbial 24: 140- 145. 
HYDRAULIC FLUIDS 333 

8. REFERENCES 

*Quaker 1993. Material Safety Data Sheet: Quintolubric 95830W. June 1, 1993 

*Reape JM. 1982. Neurologic health impact on workers with chronic low dose exposure to aryl phosphates. 

Thesis submitted to the faculty of the graduate school of the university of Minnesota. 

*Richardson RJ, Moore TB, Kayyali US, et al. 1993. Chlorpyrifos: Assessment of potential for delayed 

neurotoxicity by repeated dosing in adult hens with monitoring of brain acetylcholinesterase, brain and 

lymphocyte neurotoxic esterase, and plasma butyrylcholinesterase activities. Fundam Appl Toxicol 21:89-96. 

*Robinson EC, Hammond BG, Johannsen FR, et al. 1986. Teratogenicity studies of alkylaryl phosphate 

ester plasticizers in rats. Fundam Appl Toxicol 7:138-143. 

*RTECS. 1993. Registry of Toxic Effects of Chemical Substances. U.S. Department of Health and Human 

Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and 

Health, Cincinnati, OH. May 1993. 

*RTECS. 1996. Registry of Toxic Effects of Chemical Substances (RTECS). National Institute for 

Occupational Safety and Health (NIOSH). Computer database online. 

*RTI. 1992. Research Triangle Institute. Two-generation reproductive toxicity study of tributyl phosphate 

administered in the feed to CD (Sprague-Dawley) rats. RTI Project No. 6OC-4652. 

*Saeger VW, Hicks 0, Kaley RG, et al. 1979. Environmental fate of selected phosphate esters. 

Environmental Science and Technology 13:840-844. 

*Saliot A, Andril C, Ho R, et al. 1985. Hydrocarbons in the Mediterranean Sea: Their occurrence and fate in 

the sediment and in the water column, as dissolved and associated with small and large size particulates. 

Journal of Environmental Analytical Chemical 22:25-46. 

*Sawhney BL. 1989. Movement of organic chemicals through landfill and hazardous waste disposal sites. 

In: Reactions and movement of organic chemicals in soils. SSSA Special Publication no. 22,447-474. 

*Schwab BW, Richardson RJ. 1986. Lymphocyte and brain neurotoxic esterase: Dose and time dependence of 

inhibition in the hen examined with three organophosphorus esters. Toxicol Appl Pharmacol83:1-9. 

*Senanayake N, Jeyaratnam J. 1981. Toxic Polyneuropathy due to Gingili Oil contaminated with tri-cresyl 

phosphate affecting adolescent girls in Sri Lanka. The Lancet, January 10, 1981. 

*Serrazanetti GP, Conte LS, Carpene E, et al. 1991. Distribution of aliphatic hydrocarbons in plankton of 

Adriatic sea open waters. Chemosphere 23:925-938. 

“Shanor SP, Van Hees GR, Bart N, et al. 1961. The influence of age and sex on human plasma and red cell 

cholinesterase. Am J Med Sci 242:357-36 1. 

*Shaw DG, ed. 1989. Solubility data series. Volume 38: Hydrocarbons with water and seawater. Part II: 

Hydrocarbons C8 to C36. New York: Pergamon Press, 546-547. 
HYDRAULIC FLUIDS 334 

8. REFERENCES
 

*Sheaffer KK. 1977. Summary report: Toxicity of aryl phosphates, Kishacoquillas Creek, Standard Steel 

Works, Mifflin County. Memorandum to T.P. Clista, Division of Water Quality, Commonwealth of 

Pennsylvania. 

*Sheldon LS, Hites RA. 1978. Organic compounds in the Delaware River. Environmental Science and 

Technology 12:1188-l 194. 

*Sheldon LS, Hites RA. 1979. Sources and movement of organic chemicals in the Delaware River. 

Environmental Science and Technology 13574-579. 

*Shubkin RL. 1993. Polyalphaolefins. In: Shubkin RL, ed. Synthetic lubricants and high-performance 

functional fluids. New York: Marcel Dekker, Inc., l-40. 

*Siegel J, Rudolph HS, Getzkin AJ, et al. 1965. Effects on experimental animals of long-term continuous 

inhalation of a triaryl phosphate hydraulic fluid. Toxicol Appl Pharmacol7:543-549. 

*Siemiatycki J, Dewar R, Nadon L, et al. 1987. Associations between several sites of cancer and twelve 

petroleum-derived liquids. Stand J Work Environ Health 13:493-504. 

*Singler RE, Bieberich MJ. 1993. Phosphazenes. In: Shubkin RL, ed. Synthetic lubricants and 

high-performance functional fluids. New York: Marcel Dekker, Inc., 215-228. 

*Smith MI, Elvove E, Valaer PJ, et al. 1930. Pharmacological and chemical studies of the cause of so-called 

ginger paralysis. Public Health Rep 45:1703-1717. 

*Snyder Jr. CE, Gschwender LJ. 1993. Aerospace. In: Shubkin RL, ed. Synthetic lubricants and 

high-performance functional fluids. New York: Marcel Dekker, Inc., 525-532. 

*Somkuti SG, Abou-Donia MB. 1990. Disposition, elimination, and metabolism of tri-ortho-cresyl 

phosphate following daily oral administration in Fischer 344 male rats. Arch Toxicol 64:572-579. 

*Sornkuti SG, Lapadula D, Chapin RM, et al. 1991. Light and electron microscopic evidence of tri-orthocresyl 

phosphate (TOCP)-mediated testicular toxicity in F344 rats. Toxicol Appl Pharmacol 107:35-46. 

*Somkuti SG, Lapadula DM, Chapin RE, et al. 1987a. Reproductive tract lesions resulting from subchronic 

administration (63 days) of tri-o-cresyl phosphate in male rats. Toxicol Appl Pharmacol89:49-63. 

*Somkuti SG, Lapadula DM, Chapin RE, et al. 1987b. Time course of the tri-o-cresyl phosphate-induced 

testicular lesion in F-344 rats: Enzymatic, hormonal, and sperm parameter studies. Toxicol Appl Pharmacol 

89:64-72. 

*Sprague GL, Castles TR, Bickford AA. 1984. Assessment of the delayed neurotoxic potential of isopropyl 

triphenylphosphate using a nontraditional testing strategy. Toxicol Environ Health 14:773-788. 

*SRC. 1994a. Syracuse Research Corporation. HENRYWIN. Henry program for MS Windows 3.1. 

Syracuse Research Corporation, Merrill Lane Syracuse, NY. 

*SRC. 1994b. Syracuse Research Corporation. HYDROWIN. Hydro program for MS Windows 3.1. 

Syracuse Research Corporation, Merrill Lane Syracuse, NY. 
HYDRAULIC FLUIDS 335 

8. REFERENCES
 

*SRC. 1995a. Syracuse Research Corporation. AOPWIN. Atmospheric Oxidation Program for Microsoft 

Windows 3.1. Syracuse Research Corporation, Merrill Lane Syracuse, NY. 

*SRC. 1995b. Syracuse Research Corporation. KOWWIN. Log Kow program for MS Windows 3.1. 

Syracuse Research Corporation, Merrill Lane Syracuse, NY. 

*Srivastava. 1990. An outbreak of tricresyl phosphate poisoning in Calcutta, India. Fd Chem Toxic 

28(4):303-304. 

*Stauffer Chemical Company. 197 1. Neurotoxicity of Fyrquel 1.50. T-6422. 

*Stauffer Chemical Company. 1980. Neurotoxicity evaluation of Fyrquel EHC. T-10264. 

*Stauffer Chemical Company. 1981. Toxicology report on “effect of 3 doses of Fyrquel EHC on neurotoxic 

esterase”. T-10553. 

*Stauffer Chemical Company. 1982. A teratology study in CD rats with Phosflex 51B. 

*Strachan WMJ. 1974. Chloroform-extractable organic compounds in the international great lakes. In: 

Keith LH, ed. Identification and Analysis of Organic Pollutants in Water. Ann Arbor, MI: Ann Arbor 

Science, 479,487-488. 

*Suffet IH, Brenner L, Radziul JV. 1980. GC/MS identification of trace organic compounds in Philadelphia 

waters during a 2-year period. Water Research 14:853-867. 

*Sutton WL, Terhaar CJ, Miller FA, et al. 1960. Studies on the industrial hygiene and toxicology of 

triphenyl phosphate. Archives of Environmental Health 1:33-46. 

*Suwita E, Abou-Donia MB. 1990. Pharmacokinetics and metabolism of a single subneurotoxic oral dose of 

tri-o-cresyl phosphate in hens. Arch Toxicol 64:237-241. 

*Suzuki T, Sasaki K, Takeda M, et al. 1984a. Metabolism of tributyl phosphate in male rats. J Agric Food 

Chem 32:603-610. 

*Suzuki T, Sasaki K, Takeda M, et al. 1984b. Some S-containing metabolites of tributyl phosphate in the 

rat. J Agric Food Chem 32:1278-1283. 

*Taylor P, Li Y, Camp S, et al. 1993. Structure and regulation of expression of the acetylcholinesterase gene. 

Chem Biol Interactions 87: 199-207. 

TR192. 1994. Toxic Chemical Release Inventory. National Library of Medicine, National Toxicology 

Information Program, Bethesda, MD. 

*Trundle D, Marcia1 G. 1988. Detection of cholinesterase inhibition: The significance of cholinesterase 

measurements. Ann Clin Lab Sci 18:345-352. 

*U.S. Air Force. 1989. Hydraulic fluids. In: The installation restoration program toxicology guide: Vol. 4. 

Prepared by Oak Ridge National Laboratory for Armstrong Aerospace Medical Research Laboratory, 

Wright-Patterson Air Force Base, OH, 68-l to 68-40. 
HYDRAULIC FLUIDS 336 

8. REFERENCES 

*USCG. 1994. U. S. Coast Guard. 46 CFR parts 30,50, 150,151, and 153. 59 FR 45150. 

*USITC. 1993. Synthetic organic chemicals United States production and sales, 1991. USITC Publication 

2607 U.S. International Trade Commissions, Washington, DC., 2-l to 2-7. 

*Veith GD, Delore DL, Bergstedt BV. 1979. Measuring and estimating the bioconcentration factor of 

chemicals in fish. Journal of the Fish Research Board of Canada 36:1040-1048. 

*Weber R, Ernst W. 1983. Occurrence and fluctuation of organic environmental chemicals in German 

estuaries. Vom Wasser 61:11-123. 

*Weil ED. 1980. Flame retardants (phosphorus compounds). In: Grayson M, Eckroth D, eds. 

Kirk-Othmer’s encyclopedia of chemical technology, Vol. 10, 3rd ed. New York: John Wiley & Sons, 

348-349,396-411,416-419. 

*Welsh JJ, Collins TFX, Whitby KE, et al. 1987. Teratogenic potential of triphenyl phosphate in 

Sprague-Dawley (Spartan) rats. Toxicol Ind Health 3:357-369. 

*Weschler CJ, Shields HC, Rainer D. 1990. Concentration of volatile organic compounds at a building with 

health and comfort complaints. J Am Ind Hyg Assoc 5 1:261-268. 

*WHO. 1991. Environmental health criteria for tri-n-butyl phosphate. World Health Organization, Geneva, 

Switzerland. 

*Williams DT, Nestmann ER. LeBel GL, et al. 1982. Determination of mutagenic potential and organic 

contaminants of Great Lakes drinking water. Chemosphere 11:263-276. 

*Wills JG. 1980. Hydraulic fluids. In: Kirk-Othmer’s Encyclopedia of Chemical Technology, Vol. 12, 3rd 

ed. New York: John Wiley & Sons, 712-733. 

*Wills JH. 1972. The measurement and significance of changes in the cholinesterase activities of 

erythrocytes and plasma in man and animals. CRC Crit Rev Toxicol (March): 153-202. 

*Wolfe NL. 1980. Organophosphate and organophosphorothionate esters: Application of linear free energy 

relationships to estimate hydrolysis rate constants for use in environmental fate assessment. Chemosphere 

9:571-579. 

*Yang SM, Thieme RA, von Meyerinck L, et al. 1990. Identification of isopropylated phenyl phosphates in 

rabbit bile. Biomed Environ Mass Spectrom 19:573-576. 
HYDRAULIC FLUIDS 337 

9. GLOSSARY
 

Acute Exposure-Exposure to a chemical for a duration of 14 days or less, as specified in the Toxicological 

Profiles. 

Adsorption Coeffkient (KJ)-The ratio of the amount of a chemical adsorbed per unit weight of organic 

carbon in the soil or sediment to the concentration of the chemical in solution at equilibrium. 

Adsorption Ratio (Kd)-The amount of a chemical adsorbed by a sediment or soil (i.e., the solid phase) 

divided by the amount of chemical in the solution phase, which is in equilibrium with the solid phase, at a 

fixed solid/solution ratio. It is generally expressed in micrograms of chemical sorbed per gram of soil or 

sediment. 

Bioconcentration Factor (BCF)-The quotient of the concentration of a chemical in aquatic organisms at a 

specific time or during a discrete time period of exposure divided by the concentration in the surrounding 

water at the same time or during the same period. 

Cancer Effect Level (CEL)-The lowest dose of chemical in a study, or group of studies, that produces 

significant increases in the incidence of cancer (or tumors) between the exposed population and its 

appropriate control. 

Carcinogen-A chemical capable of inducing cancer. 

Ceiling Value-A concentration of a substance that should not be exceeded, even instantaneously. 

Chronic Exposure-Exposure to a chemical for 365 days or more, as specified in the Toxicological Profiles. 

Developmental Toxicity-The occurrence of adverse effects on the developing organism that may result 

from exposure to a chemical prior to conception (either parent), during prenatal development, or postnatally 

to the time of sexual maturation. Adverse developmental effects may be detected at any point in the life span of 

the organism. 

Embryotoxicity and Fetotoxicity-Any toxic effect on the conceptus as a result of prenatal exposure to a 

chemical; the distinguishing feature between the two terms is the stage of development during which the 

insult occurred. The terms, as used here, include malformations and variations, altered growth, and in utero 

death. 

EPA Health Advisory-An estimate of acceptable drinking water levels for a chemical substance based on 

health effects information. A health advisory is not a legally enforceable federal standard, but serves as 

technical guidance to assist federal, state, and local officials. -. 

Immediately Dangerous to Life or Health (IDLH)-The maximum environmental concentration of a 

contaminant from which one could escape within 30 min without any escape-impairing symptoms or 

irreversible health effects. 

Intermediate Exposure-Exposure to a chemical for a duration of 15-364 days, as specified in the 

Toxicological Profiles. 
HYDRAULIC FLUIDS 338 

9. GLOSSARY
 

Immunologic Toxicity-The occurrence of adverse effects on the immune system that may result from 

exposure to environmental agents such as chemicals. 

In vitro-Isolated from the living organism and artificially maintained, as in a test tube. 

In Vivo-Occurring within the living organism. 

Lethal Concentration(LO) (LCLO)-The 1 lowest concentration of a chemical in air which has been reported to 

have caused death in humans or animals. 

Lethal Concentration(50) (LC50)-A calculated concentration of a chemical in air to which exposure for a 

specific length of time is expected to cause death in 50% of a defined experimental animal population. 

Lethal Dose(LO) ( LDLO)-The lowest dose of a chemical introduced by a route other than inhalation that is 

expected to have caused death in humans or animals. 

Lethal Dose(50) (LD50)-The dose of a chemicalwhich has been calculated to cause death in 50% of a 

defined experimental animal population. 

Lethal Time(50) (LT50)-A calculated period of time within which a specific concentration of a chemical is 

expected to cause death in 50% of a defined experimental animal population. 

Lowest-Observed-Adverse-Effect Level (LOAEL)-The lowest dose of chemical in a study, or group of 

studies, that produces statistically or biologically significant increases in frequency or severity of adverse 

effects between the exposed population and its appropriate control. 

Malformations-Permanent structural changes that may adversely affect survival, development, or function. 

Minimal Risk Level-An estimate of daily human exposure to a dose of a chemical that is likely to be 

without an appreciable risk of adverse noncancerous effects over a specified duration of exposure. 

Mutagen-A substance that causes mutations. A mutation is a change in the genetic material in a body cell. 

Mutations can lead to birth defects, miscarriages, or cancer. 

Neurotoxicity-The occurrence of adverse effects on the nervous system following exposure to chemical. 

No-Observed-Adverse-Effect Level (NOAEL)-The dose of chemical at which there were no statistically 

or biologically significant increases in frequency or severity of adverse effects seen between the exposed 

population and its appropriate control. Effects may be produced at this dose, but they are not considered to 

be adverse. 

Octanol-Water Partition Coefficient (KOW)-The equilibrium ratio of the concentrations of a chemical in 

n-octanol and water, in dilute solution. 

Permissible Exposure Limit (PEL)-An allowable exposure level in workplace air averaged over an 8-hour 

shift. 
HYDRAULIC FLUIDS 339 

9. GLOSSARY
 

q1*-The upper-bound estimate of the low-dose slope of the dose-response curve as determined by the 

multistage procedure. The q, * can be used to calculate an estimate of carcinogenic potency, the incremental 

excess cancer risk per unit of exposure (usually pg/L for water, mg/kg/day for food, and pg/m3 for air). 

Reference Dose (RfD)-An estimate (with uncertainty spanning perhaps an order of magnitude) of the daily 

exposure of the human population to a potential hazard that is likely to be without risk of deleterious effects 

during a lifetime. The RfD is operationally derived from the NOAEL (from animal and human studies) by a 

consistent application of uncertainty factors that reflect various types of data used to estimate RfDs and an 

additional modifying factor, which is based on a professional judgment of the entire database on the chemical. 

The RfDs are not applicable to nonthreshold effects such as cancer. 

Reportable Quantity (RQ)-The quantity of a hazardous substance that is considered reportable under 

CERCLA. Reportable quantities are (1) 1 pound or greater or (2) for selected substances, an amount 

established by regulation either under CERCLA or under Sect. 3 11 of the Clean Water Act. Quantities are 

measured over a 24-hour period. 

Reproductive Toxicity-The occurrence of adverse effects on the reproductive system that may result from 

exposure to a chemical. The toxicity may be directed to the reproductive organs and/or the related endocrine 

system. The manifestation of such toxicity may be noted as alterations in sexual behavior, fertility, 

pregnancy outcomes, or modifications in other functions that are dependent on the integrity of this system. 

Short-Term Exposure Limit (STEL)-The maximum concentration to which workers can be exposed for 

up to 15 min continually. No more than four excursions are allowed per day, and there must be at least 60 

min between exposure periods. The daily TLV-TWA may not be exceeded. 

Target Organ Toxicity-This term covers a broad range of adverse effects on target organs or physiological 

systems (e.g., renal, cardiovascular) extending from those arising through a single limited exposure to those 

assumed over a lifetime of exposure to a chemical. 

Teratogen-A chemical that causes structural defects that affect the development of an organism. 

Threshold Limit Value (TLV)-A concentration of a substance to which most workers can be exposed 

without adverse effect. The TLV may be expressed as a TWA, as a STEL, or as a CL. 

Time-Weighted Average (TWA)-An allowable exposure concentration averaged over a normal S-hour 

workday or 40-hour workweek. 

Toxic Dose (TD50)-A calculated dose of a chemical, introduced by a route other than inhalation, which is 

expected to cause a specific toxic effect in 50% of a defined experimental animal population. 

Uncertainty Factor (UF)-A factor used in operationally deriving the RfD from experimentaldata. UFs are 

intended to account for (1) the variation in sensitivity among the members of the human population, (2) the 

uncertainty in extrapolating animal data to the case of human, (3) the uncertainty in extrapolating from data 

obtained in a study that is of less than lifetime exposure, and (4) the uncertainty in using LOAEL data rather 

than NOAEL data. Usually each of these factors is set equal to 10. 
HYDRAULIC FLUIDS A-1 

APPENDIX A 

ATSDR MINIMAL RISK LEVEL 

The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) [42 U.S.C. 9601 

et seq.], as amended by the Superfund Amendments and Reauthorization Act (SARA) [Pub. L. 99-4991, 

requires that the Agency for Toxic Substances and Disease Registry (ATSDR) develop jointly with the U.S. 

Environmental Protection Agency (EPA), in order of priority, a list of hazardous substances most commonly 

found at facilities on the CERCLA National Priorities List (NPL); prepare toxicological profiles for each 

substance included on the priority list of hazardous substances; and assure the initiation of a research 

program to fill identified data needs associated with the substances. 

The toxicological profiles include an examination, summary, and interpretation of available toxicological 

information and epidemiologic evaluations of a hazardous substance. During the development of 

toxicological profiles Minimal Risk Levels (MRLs) are derived when reliable and sufficient data exist to 

identify the target organ(s) of effect or the most sensitive health effect(s) for a specific duration for a given 

route of exposure. An MRL is an estimate of the daily human exposure to a hazardous substance that is 

likely to be without appreciable risk of adverse noncancer health effects over a specified duration of exposure. 

MRLs are based on noncancer health effects only and are not based on a consideration of cancer effects. These 

substance-specific estimates, which are intended to serve as screening levels, are used by ATSDR health 

assessors to identify contaminants and potential health effects that may be of concern at hazardous waste sites. It 

is important to note that MRLs are not intended to define clean-up or action levels. 

MRLs are derived for hazardous substances using the no-observed-adverse-effect-level/uncertainty factor 

approach. They are below levels that might cause adverse health effects in the people most sensitive to such 

chemical-induced effects. MRLs are derived for acute (l-l 4 days), intermediate (15-364 days), and chronic (365 

days and longer) durations and for the oral and inhalation routes of exposure. Currently, MRLs for the dermal 

route of exposure are not derived because ATSDR has not yet identified a method suitable for this route of 

exposure. MRLs are generally based on the most sensitive chemical-induced end point considered to be of 

relevance to humans. Serious health effects (such as irreparable damage to the liver or kidneys, or birth defects) 

are not used as a basis for establishing MRLs. Exposure to a level above the MRL does not mean that adverse 

health effects will occur. 
HYDRAULIC FLUIDS A-2 

APPENDIX A
 

MRLs are intended only to serve as a screening tool to help public health professionals decide where to look 

more closely. They may also be viewed as a mechanism to identify those hazardous waste sites that are not 

expected to cause adverse health effects. Most MRLs contain a degree of uncertainty because of the lack of 

precise toxicological information on the people who might be most sensitive (e.g., infants, elderly, 

nutritionally or immunologically compromised) to the effects of hazardous substances. ATSDR uses a 

conservative (i.e., protective) approach to address this uncertainty consistent with the public health principle 

of prevention. Although human data are preferred, MRLs often must be based on animal studies because 

relevant human studies are lacking. In the absence of evidence to the contrary, ATSDR assumes that humans are 

more sensitive to the effects of hazardous substances than animals and that certain persons may be particularly 

sensitive. Thus, the resulting MRL may be as much as a hundredfold below levels that have been shown to be 

nontoxic in laboratory animals. 

Proposed MRLs undergo a rigorous review process: Health Effects/MRL Workgroup reviews within the 

Division of Toxicology, expert panel peer reviews, and agencywide MRL Workgroup reviews, with 

participation from other federal agencies and comments from the public. They are subject to change as new 

information becomes available concomitant with updating the toxicological profiles. Thus MRLs in the most 

recent toxicological profiles supersede previously published levels. For additional information regarding 

MRLs, please contact the Division of Toxicology, Agency for Toxic Substances and Disease Registry, 1600 

Clifton Road, Mailstop E29, Atlanta, Georgia 30333. 
HYDRAULIC FLUIDS A-3 

APPENDIX A
 

MINIMAL RISK LEVEL (MRL) WORKSHEETS
 

No MRLs have been derived for Hydraulic Fluids.HYDRAULIC FLUIDS
 
HYDRAULIC FLUIDS B-1 

APPENDIX B 

USER’S GUIDE 

Chapter 1 

Public Health Statement 

This chapter of the profile is a health effects summary written in non-technical language. Its intended 

audience is the general public especially people living in the vicinity of a hazardous waste site or chemical 

release. If the Public Health Statement were removed from the rest of the document, it would still 

communicate to the lay public essential information about the chemical. 

The major headings in the Public Health Statement are useful to find specific topics of concern. The topics 

are written in a question and answer format. The answer to each question includes a sentence that will direct the 

reader to chapters in the profile that will provide more information on the given topic. 

Chapter 2 

Tables and Figures for Levels of Significant Exposure (LSE) 

Tables (2-1,2-2, and 2-3) and figures (2-l and 2-2) are used to summarize health effects and illustrate 

graphically levels of exposure associated with those effects. These levels cover health effects observed at 

increasing dose concentrations and durations, differences in response by species, minimal risk levels (MRLs) to 

humans for noncancer end points, and EPA’s estimated range associated with an upper- bound individual 

lifetime cancer risk of 1 in 10,000 to 1 in 10,000,000. Use the LSE tables and figures for a quick review of the 

health effects and to locate data for a specific exposure scenario. The LSE tables and figures should always be 

used in conjunction with the text. All entries in these tables and figures represent studies that provide reliable, 

quantitative estimates of No-Observed-Adverse- Effect Levels (NOAELs), 

Lowest-Observed-Adverse-Effect Levels (LOAELs), or Cancer Effect Levels (CELs). 

The legends presented below demonstrate the application of these tables and figures. Representative 

examples of LSE Table 2-l and Figure 2-l are shown. The numbers in the left column of the legends 

correspond to the numbers in the example table and figure. 

LEGEND 

See LSE Table 2-1 

(1)	 Route of Exposure One of the first considerations when reviewing the toxicity of a substance using 

these tables and figures should be the relevant and appropriate route of exposure. When sufficient 

data exists, three LSE tables and two LSE figures are presented in the document. The three LSE tables 

present data on the three principal routes of exposure, i.e., inhalation, oral, and dermal (LSE Table 2- 1, 

2-2, and 2-3, respectively). LSE figures are limited to the inhalation (LSE Figure 2-l) and oral (LSE 

Figure 2-2) routes. Not all substances will have data on each route of exposure and will not therefore 

Have all five of the tables and figures. 
 

HYDRAULIC FLUIDS B-2 

APPENDIX B
 

(2) Exposure Period Three exposure periods - acute (less than 15 days), intermediate (15-364 days), and

 chronic (365 days or more) are presented within each relevant route of exposure. In this example, an

 inhalation study of intermediate exposure duration is reported. For quick reference to health effects 

occurring from a known length of exposure, locate the applicable exposure period within the LSE table

 and figure. 

(3) Health Effect The major categories of health effects included in LSE tables and figures are death,

 systemic, immunological, neurological, developmental, reproductive, and cancer. NOAELs and

 LOAELs can be reported in the tables and figures for all effects but cancer. Systemic effects are

 further defined in the “System” column of the LSE table (see key number 18). 

(4) Key to Figure Each key number in the LSE table links study information to one or more data points

 using the same key number in the corresponding LSE figure. In this example, the study represented by

 key number 18 has been used to derive a NOAEL and a Less Serious LOAEL (also see the 2 “18r” data

 points in Figure 2-l). 

(5) Species The test species, whether animal or human, are identified in this column. Section 2.5,

 “Relevance to Public Health,” covers the relevance of animal data to human toxicity and Section 2.3,

 “Toxicokinetics,” contains any available information on comparative toxicokinetics. Although

 NOAELs and LOAELs are species specific, the levels are extrapolated to equivalent human doses to

 derive an MRL. 

(6) Exposure Frequency/Duration The duration of the study and the weekly and daily exposure regimen

 are provided in this column. This permits comparison of NOAELs and LOAELs from different

 studies. In this case (key number 1 S), rats were exposed to 1,1,2,2-tetrachloroethane via inhalation for

 6 hours per day, 5 days per week, for 3 weeks. For a more complete review of the dosing regimen refer

 to the appropriate sections of the text or the original reference paper, i.e., Nitschke et al. 1981. 

(7) System This column further defines the systemic effects. These systems include: respiratory,

 cardiovascular, gastrointestinal, hematological, musculoskeletal, hepatic, renal, and dermal/ocular.

 “Other” refers to any systemic effect (e.g., a decrease in body weight) not covered in these systems. In

 the example of key number 18, 1 systemic effect (respiratory) was investigated. 

(8) NOAEL A No-Observed-Adverse-Effect Level (NOAEL) is the highest exposure level at which no

 harmful effects were seen in the organ system studied. Key number 18 reports a NOAEL of 3 ppm for

 the respiratory system which was used to derive an intermediate exposure, inhalation MRL of 0.005

 ppm (see footnote “b”). 

(9) LOAEL A Lowest-Observed-Adverse-Effect Level (LOAEL) is the lowest dose used in the study that

 caused a harmful health effect. LOAELs have been classified into “Less Serious” and “Serious”

 effects. These distinctions help readers identify the levels of exposure at which adversehealth effects

 first appear and the gradation of effects with increasing dose. A brief description of the specific

 endpoint used to quantify the adverse effect accompanies the LOAEL. The respiratory effect reported

 in key number 18 (hyperplasia) is a Less serious LOAEL of 10 ppm. MRLs are not derived from

 Serious LOAELs. 

(10) Reference The complete reference citation is given in chapter 8 of the profile. 
 

 

 

 

 

 

 

 

 

HYDRAULIC FLUIDS B-3 

APPENDIX B

 (11) CEL A Cancer Effect Level (CEL) is the lowest exposure level associated with the onset of

 carcinogenesis in experimental or epidemiologic studies. CELs are always considered serious effects.

 The LSE tables and figures do not contain NOAELs for cancer, but the text may report doses not

 causing measurable cancer increases. 

(12) Footnotes Explanations of abbreviations or reference notes for data in the LSE tables are found in the

 footnotes. Footnote “b” indicates the NOAEL of 3 ppm in key number 18 was used to derive an MRL

 of 0.005 ppm. 

LEGEND 

See Figure 2-1 

LSE figures graphically illustrate the data presented in the corresponding LSE tables. Figures help the reader 

quickly compare health effects according to exposure concentrations for particular exposure periods. 

(13) Exposure Period The same exposure periods appear as in the LSE table. In this example, health

 effects observed within the intermediate and chronic exposure periods are illustrated. 

(14) Health Effect These are the categories of health effects for which reliable quantitative data exists. The

 same health effects appear in the LSE table. 

(15) Levels of Exposure concentrations or doses for each health effect in the LSE tables are graphically 

displayed in the LSE figures. Exposure concentration or dose is measured on the log scale “y” axis.

 Inhalation exposure is reported in mg/m3

 or ppm and oral exposure is reported in mg/kg/day. 

(16) NOAEL In this example, 18r NOAEL is the critical endpoint for which an intermediate inhalation

 exposure MRL is based. As you can see from the LSE figure key, the open-circle symbol indicates to a

 NOAEL for the test species-rat. The key number 18 corresponds to the entry in the LSE table. The 

dashed descending arrow indicates the extrapolation from the exposure level of 3 ppm (see entry 18 in

 the Table) to the MRL of 0.005 ppm (see footnote “b” in the LSE table). 

(17 ) CEL Key number 38r is 1 of 3 studies for which Cancer Effect Levels were derived. The diamond

 symbol refers to a Cancer Effect Level for the test species-mouse. The number 38 corresponds to the

 entry in the LSE table. 

(18) Estimated Upper-Bound Human Cancer Risk Levels This is the range associated with the upper-bound

 for lifetime cancer risk of 1 in 10,000 to 1 in 10,000,000. These risk levels are derived from the EPA’s

 Human Health Assessment Group’s upper-bound estimates of the slope of the cancer dose response

 curve at low dose levels (qi *). 

(19) Key to LSE Figure The Key explains the abbreviations and symbols used in the figure. 


HYDRAULIC FLUIDS B-6 

APPENDIX B 

Chapter 2 (Section 2.5) 

Relevance to Public Health 

The Relevance to Public Health section provides a health effects summary based on evaluations of existing 

toxicologic, epidemiologic, and toxicokinetic information. This summary is designed to present interpretive, 

weight-of-evidence discussions for human health end points by addressing the following questions. 

(1). What effects are known to occur in humans? 

(2). What effects observed in animals are likely to be of concern to humans? 

(3). What exposure conditions are likely to be of concern to humans, especially around hazardous waste 

sites? 

The section covers end points in the same order they appear within the Discussion of Health Effects by Route of
 

Exposure section, by route (inhalation, oral, dermal) and within route by effect. Human data are presented first,
 

then animal data. Both are organized by duration (acute, intermediate, chronic). In vitro data and data from
 

parenteral routes (intramuscular, intravenous, subcutaneous, etc.) are also considered in this section. If data are
 

located in the scientific literature, a table of genotoxicity information is included.
 

The carcinogenic potential of the profiled substance is qualitatively evaluated, when appropriate, using
 

existing toxicokinetic, genotoxic, and carcinogenic data. ATSDR does not currently assess cancer potency or
 

perform cancer risk assessments. Minimal risk levels (MRLs) for noncancer end points (if derived) and the end
 

points from which they were derived are indicated and discussed.
 

Limitations to existing scientific literature that prevent a satisfactory evaluation of the relevance to public
 

health are identified in the Data Needs section.
 

Interpretation of Minimal Risk Levels
 

Where sufficient toxicologic information is available, we have derived minimal risk levels (MRLs) for
 

inhalation and oral routes of entry at each duration of exposure (acute, intermediate, and chronic). These
 

MRLs are not meant to support regulatory action; but to acquaint health professionals with exposure levels at
 

which adverse health effects are not expected to occur in humans. They should help physicians and public health
 

officials determine the safety of a community living near a chemical emission, given the concentration of a
 

contaminant in air or the estimated daily dose in water. MRLs are based largely on toxicological studies in
 

animals and on reports of human occupational exposure.
 

MRL users should be familiar with the toxicologic information on which the number is based. Chapter 2.5,
 

“Relevance to Public Health,” contains basic information known about the substance. Other sections such as 2.7,
 

“Interactions with Other Substances,” and 2.8, “Populations that are Unusually Susceptible” provide
 

important supplemental information.
 

MRL users should also understand the MRL derivation methodology. MRLs are derived using a modified
 

version of the risk assessment methodology the Environmental Protection Agency (EPA) provides (Barnes
 

and Dourson 1988) to determine reference doses for lifetime exposure (RfDs).
 
HYDRAULIC FLUIDS B-7 

APPENDIX B
 

To derive an MRL, ATSDR generally selects the most sensitive endpoint which, in its best judgement, 

represents the most sensitive human health effect for a given exposure route and duration. ATSDR cannot 

make this judgement or derive an MRL unless information (quantitative or qualitative) is available for all 

potential systemic, neurological, and developmental effects. If this information and reliable quantitative data 

on the chosen endpoint are available, ATSDR derives an MRL using the most sensitive species (when 

information from multiple species is available) with the highest NOAEL that does not exceed any adverse 

effect levels. When a NOAEL is not available, a lowest-observed-adverse-effect level (LOAEL) can be used 

to derive an MRL, and an uncertainty factor (UF) of 10 must be employed. Additional uncertainty factors of 

10 must be used both for human variability to protect sensitive subpopulations (people who are most 

susceptible to the health effects caused by the substance) and for interspecies variability (extrapolation from 

animals to humans). In deriving an MRL, these individual uncertainty factors are multiplied together. The 

product is then divided into the inhalation concentration or oral dosage selected from the study. Uncertainty 

factors used in developing a substance-specific MRL are provided in the footnotes of the LSE Tables.