TOXICOLOGICAL PROFILE FOR
 

OTTO FUEL II AND ITS COMPONENTS
 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
 

Public Health Service
 

Agency for Toxic Substances and Disease Registry
 

June 1995 
OTTO FUEL II AND ITS COMPONENTS 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. 
OTTO FUEL II AND ITS COMPONENTS iii 

UPDATE STATEMENT 

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
 



OTTO FUEL II AND ITS COMPONENTS vii 

CONTRIBUTORS 

CHEMICAL MANAGER(S)/AUTHOR(S):
 

Henry Abadin, M.S.P.H.
 

ATSDR, Division of Toxicology, Atlanta, GA
 

Fernando Llados, Ph.D.
 

Research Triangle Institute, Research Triangle Park, NC
 

THE PROFILE HAS UNDERGONE THE FOLLOWING ATSDR INTERNAL REVIEWS:
 

1. Green Border Review. Green Bonier 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. Quality Assurance Review. The Quality Assurance Branch assures that consistency across

 profiles is maintained, identifies any significant problems in format or content, and establishes

 that Guidance has been followed. 

OTTO FUEL II AND ITS COMPONENTS ix 

PEER REVIEW 

A peer review panel was assembled for Otto Fuel II and its components. The panel consisted of the 

following members: 

1 . Steven Godin, Ph.D., DABT, Research Scientist, Drug Metabolism, CEPHALON, Inc., West

 Chester, Pennsylvania; 

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

3 . Dr. Richard Stewart, Private Consultant, Racine, Wisconsin. 

These experts collectively have knowledge of Otto Fuel II and its components’ 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(i)( 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. 









OTTO FUEL II AND ITS COMPONENTS 1 

1. PUBLIC HEALTH STATEMENT 

This statement was prepared to give you information about Otto Fuel II and its components, 

and to emphasize the human health effects that may result from exposure to them. The 

Environmental Protection Agency (EPA) has identified 1,397 hazardous waste sites as the 

most serious in the nation. These sites make up the National Priorities List (NPL) and are the 

sites targeted for long-term federal clean-up activities. Otto Fuel II has been found at two of 

the sites on the NPL. However, the number of NPL sites evaluated for Otto Fuel II and its 

components is not known. As EPA evaluates more sites, the number of sites at which Otto 

Fuel II and its components are found may increase. This information is important for you to 

know because Otto Fuel II and its components may cause harmful health effects and because 

these sites are potential or actual sources of human exposure to Otto Fuel II and its 

components. 

When a chemical 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 as a chemical emission. This 

emission, which is also called a release, does not always lead to exposure. You can be 

exposed to a chemical only when you come into contact with the chemical. You may be 

exposed to it in the environment by breathing, eating or drinking substances containing the 

chemical, or from skin contact with it. 

If you are exposed to a hazardous chemical such as Otto Fuel II and its components, several 

factors will determine whether harmful health effects will occur, and what the type and 

severity of those health effects will be. These factors include the dose (how much), the 

duration (how long), the route or pathway by which you are exposed (breathing, eating, 

drinking, or skin contact), the other chemicals to which you are exposed, and your individual 

characteristics such as age, sex, nutritional status, family traits, life-style, and state of health. 
OTTO FUEL II AND ITS COMPONENTS 2 

1. PUBLIC HEALTH STATEMENT 

1.1 WHAT ARE OTTO FUEL II AND ITS COMPONENTS? 

Otto Fuel II is a distinct-smelling, reddish-orange, oily liquid that the U.S. Navy uses as a 

fuel for torpedo and other weapons systems. It is a mixture of three synthetic substances. It 

contains mostly propylene glycol dinitrate, but it also contains dibutyl sebacate and 

2-nitrodiphenylamine. 

Propylene glycol dinitrate is the explosive part of Otto Fuel II. It is a colorless liquid with an 

unpleasant odor. Other names for propylene glycol dinitrate are PGDN, 1,Zpropylene glycol 

dinitrate, and 1,2-propanediol dinitrate. 

Dibutyl sebacate is a clear liquid. It is most often used for making plastics, many of which 

are used for packaging food. It is also used to enhance flavor in foods such as ice cream, 

candy, baked goods, and nonalcoholic drinks. Some shaving creams also contain dibutyl 

sebacate. Other names for dibutyl sebacate are decanedioic acid, dibutyl ester; sebacic acid, 

dibutyl ester; and dibutyl decanedioate. 

2-Nitrodiphenylamine is a solid. Otto Fuel II contains 2-nitrodiphenylamine to control the 

explosion of propylene glycol dinitrate. It is also used as a solvent dye. Other names for 

2-nitrodiphenylamine are 2-nitrobenzenamine, 2-nitro-N-phenyl; 2-nitro-N-phenylaniline; and 

Sudan Yellow 1339. 

See Chapters 3 and 4 for more information. 

1.2 WHAT HAPPENS TO OTTO FUEL II AND ITS COMPONENTS WHEN THEY

 ENTER THE ENVIRONMENT? 

Otto Fuel II enters the environment mainly in waste water from Navy facilities that produce it 

or are involved in torpedo rework operations. Otto Fuel II may also be spilled by accident or 

be disposed of improperly and contaminate soil. We do not have much information on what 

happens to Otto Fuel II and its components when they enter the environment. We do know 
OTTO FUEL II AND ITS COMPONENTS 3 

1. PUBLIC HEALTH STATEMENT
 

that Otto Fuel II enters the environment as a mixture of three separate components. A large 

portion of the propylene glycol dinitrate will evaporate very rapidly from the water or the 

surface of wet soil, but a small portion of it will be broken down by light to other chemicals. 

Propylene glycol dinitrate that enters the air is probably also broken down by light. Some 

studies suggest that propylene glycol dinitrate in water or soil is broken down by 

microorganisms that are normally present, but not all studies agree about this point. It is 

unlikely that 2-nitrodiphenylamine will evaporate from water or soil into the air. 

2-Nitrodiphenylamine will also probably not stay dissolved in water because it does not 

dissolve easily in water and because it most likely sticks to particles in the water or soil. 

2-Nitrodiphenylamine that enters the water is broken down by light. A portion of 

2-nitrodiphenylamine in the water or soil also is broken down by microorganisms. We do not 

know which of the two processes (light- or microorganism-assisted) is more important in 

breaking down this chemical in the environment. Many microorganisms in water and soil 

have the capability to break down dibutyl sebacate. We do not have any information on other 

ways that dibutyl sebacate might be broken down in water or soil. There is no evidence that 

dibutyl sebacate evaporates into the air from soil or water. You will find more information 

about the fate and movement of Otto Fuel II and its components in the environment in 

Chapter 5. 

1.3 HOW MIGHT I BE EXPOSED TO OTTO FUEL II AND ITS COMPONENTS? 

Humans are most likely to be exposed to Otto Fuel II or its components in areas where Otto 

Fuel II is used as a torpedo fuel or where it is made. The most likely ways these people will 

be exposed to Otto Fuel II are by breathing contaminated air and by touching the fuel during 

handling. One of the chemicals that makes up Otto Fuel II, propylene glycol dinitrate, was 

measured at levels of less than 1 part per million (ppm) parts of air in a facility where Otto 

Fuel II was used. Another chemical found in Otto Fuel II, 2-nitrodiphenylamine, was 

measured at levels of 1-14 ppm in waste water released from a plant where torpedo fuel was 

being manufactured. This chemical was also measured at levels of 0.5-12.2 ppm in the 

sediment of the river where the waste water was dumped. Almost nothing is known about 

levels of Otto Fuel II or its components at hazardous waste sites or at other places. It is not 
OTTO FUEL II AND ITS COMPONENTS 4 

1. PUBLIC HEALTH STATEMENT
 

known whether exposure of persons living or working near hazardous waste sites occurs. 

Exposure to 2-nitrodiphenylamine also may occur as the result of its manufacture and use as a 

solvent dye. Exposure to dibutyl sebacate also may occur as a result of its manufacture and 

use as a flavor enhancer, as an ingredient in plastic food containers, and as an ingredient in 

shaving lotions. See Chapter 5 for more information. 

1.4 HOW CAN THE COMPONENTS OF OTTO FUEL II ENTER AND LEAVE MY

 BODY? 

Propylene glycol dinitrate, the explosive chemical in Otto Fuel II, enters your bloodstream 

when you breathe it in, when you drink water containing it, eat food or soil containing it, and 

when your skin comes in contact with it. 2-Nitrodiphenylamine and dibutyl sebacate, the 

other two components in Otto Fuel II, enter your bloodstream when you drink water or eat 

food with either of these two chemicals in it. We do not know how much of these two 

chemicals can enter your bloodstream by breathing or touching them. Within a day, 

propylene glycol dinitrate is rapidly and completely broken down in your blood to chemicals 

that are normally found in your body. Some of the breakdown products leave your body in 

your urine, and others are used by your body to make other chemicals. One study reported 

that dibutyl sebacate is rapidly broken down in your body by the same process that your body 

uses to break down fat. We do not know what happens to the breakdown products of dibutyl 

sebacate in your body. We also do not know what happens to 2-nitrodiphenylamine in your 

body or how it is eliminated. Chapter 2 contains more information on how the chemicals in 

Otto Fuel II enter and leave your body. 

1.5 HOW CAN OTTO FUEL II AND ITS COMPONENTS AFFECT MY HEALTH? 

People who work around Otto Fuel II report experiencing a number of effects which include 

headaches, loss of balance, poor eye-hand coordination, eye irritation, congested noses, 

nausea, dizziness, and difficulty breathing. The most common side effect of overexposure is 

headache. It can occur when there are no other reported side effects, even when the degree 

of overexposure is minimal. The greater the overexposure, the larger the number of reported 
OTTO FUEL II AND ITS COMPONENTS 5 

1. PUBLIC HEALTH STATEMENT 

symptoms. Some people who work around Otto Fuel II get used to being around it, and after 

a period of time, they do not seem to experience discomfort. People who have worked 

around Otto Fuel II, but later are no longer exposed to this chemical, might feel chest pain or 

rapid beating of the heart, or have heart attacks. We do not know if Otto Fuel II affects the 

ability of people to have children or if it causes children to have birth defects. We also do 

not know if this chemical affects the ability of people to fight disease or if it causes cancer in 

people. Most of the effects of Otto Fuel II on people’s health are believed to be caused by 

its major component, propylene glycol dinitrate. Exposure to levels of propylene glycol 

dinitrate as low as 0.2 ppm in the air for several hours causes headaches in some persons. At 

0.2 ppm, some brain wave patterns are also altered, and at 0.5 ppm, dizziness and nausea are 

common. We do not know anything about the effects of propylene glycol dinitrate on the 

ability of people to have babies or to fight disease. We also do not know whether propylene 

glycol dinitrate causes birth defects or cancer. Very little is known about the other two 

components of Otto Fuel II, 2-nitrodiphenylamine or dibutyl sebacate. We do not know 

anything about the human health effects of the component 2-nitrodiphenylamine. The only 

thing we know about the human health effects of the component dibutyl sebacate is that it 

was not irritating to the skin of volunteers who were tested. 

Animal studies show effects of propylene glycol dinitrate that are related to the effects seen in 

people. Results from animal studies also show additional effects of propylene glycol dinitrate 

that have not been reported in people exposed to this chemical. Exposure of animals to 

moderate-to-large amounts of propylene glycol dinitrate for several weeks causes problems in 

blood, like anemia and a decreased ability of the blood to carry oxygen. The livers and 

kidneys of some animals exposed to moderate levels of propylene glycol dinitrate all day, 

every day, for several months showed some damage. We do not know whether these effects 

might also occur in persons exposed to sufficiently high concentrations. We also do not 

know whether propylene glycol dinitrate affects the ability of animals to have babies or 

whether it causes birth defects in animals. However, we know that rats that had Otto Fuel II 

applied to their skin during pregnancy gave birth to babies with low birth weights. Propylene 

glycol dinitrate has not been sufficiently tested to see whether or not it causes cancer in 

animals. 
OTTO FUEL II AND ITS COMPONENTS 6 

1. PUBLIC HEALTH STATEMENT
 

Animal studies also examined the effects of dibutyl sebacate. These studies showed that 

eating large amounts of this chemical for long periods did not affect the health of the animals 

that ate it. The babies of animals that ate large amounts of this chemical grew more slowly 

than babies of animals that did not eat it. We do not know whether dibutyl sebacate causes 

cancer in animals. 

We do not know anything about the health effects of 2-nitrodiphenylamine in animals. 

The Department of Health and Human Services, the International Agency for Research on 

Cancer, and the Environmental Protection Agency have not reviewed Otto Fuel II to 

determine what classification of carcinogenicity it should receive. 

More information on the health effects of the chemicals found in Otto Fuel II is given in 

Chapter 2. 

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

 EXPOSED TO OTTO FUEL II AND ITS COMPONENTS? 

There is no routinely available test that can directly measure an individual’s exposure to Otto 

Fuel II. Sensitive methods have been used to measure propylene glycol dinitrate, the major 

component in Otto Fuel II, in both the blood and the exhaled air of the exposed individual. 

Tests that measure the amount of a breakdown product of propylene glycol dinitrate in your 

urine could give some information about whether a person has been exposed to this chemical. 

These tests, which assume the same breakdown products for humans and animals, could be 

easily performed by clinical laboratories. Your body rapidly breaks down propylene glycol 

dinitrate, and the breakdown products leave your body in your urine within a day. Therefore, 

the tests are only helpful if given within a few hours of exposure. The tests also are not 

specific for exposure to propylene glycol dinitrate. Many other chemicals, such as those 

found in fertilizers, explosives, some heart and diarrhea medications, and, some food 

preservatives, also raise the amount of this breakdown product in the urine. No tests are 
OTTO FUEL II AND ITS COMPONENTS 7 

1. PUBLIC HEALTH STATEMENT 

known for measuring the other two components of Otto Fuel II in your body. Chapters 2 and 

6 contain more information on these tests. 

1.7 WHAT RECOMMENDATIONS HAS THE FEDERAL GOVERNMENT MADE TO

 PROTECT HUMAN HEALTH? 

The government has developed regulations and guidelines for Otto Fuel II and the chemicals 

in it. These are designed to protect the public from potential harmful health effects of the 

chemical. The Department of Transportation regulates the transportation of Otto Fuel II 

because of its potential health effects. 

The National Institute for Occupational Safety and Health (NIOSH) recommends that workers 

not be exposed to air containing more than 0.05 ppm propylene glycol dinitrate during an 

8-hour workday, 40-hour workweek. For more information, see Chapter 7. 

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, E-29 

Atlanta, Georgia 30333 

(404) 639-6000 

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

and environmental health clinic. These clinics specialize in the recognition, evaluation, and 

treatment of illnesses resulting from exposure to hazardous substances. 

OTTO FUEL II AND ITS COMPONENTS 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 Otto Fuel II 

and its components, and a depiction of significant exposure levels associated with various adverse 

health effects. It contains descriptions and evaluations of studies, and presents levels of significant 

exposure for Otto Fuel II and its components based on toxicological studies and epidemiological 

investigations. 

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 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, developmental, 

reproductive, 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-observedadverse-effect levels (LOAELs) reflect the actual doses (levels of exposure) used in the 

studies. LOAELs have been classified into “less serious” or “serious” effects. These distinctions are 

intended to help the users of the document identify the levels of exposure at which adverse health 

effects start to appear. They should also help to determine whether or not the effects vary with dose 

and/or duration, and place into perspective the possible significance of these effects to human health. 

The significance of the exposure levels shown in the tables and figures may differ depending on the 

user’s perspective. For example, physicians concerned with the interpretation of clinical findings in 

exposed persons may be interested in levels of exposure associated with “serious” effects. Public 

health officials and project managers concerned with appropriate actions to take at hazardous waste 
OTTO FUEL II AND ITS COMPONENTS 10 

2. HEALTH EFFECTS
 

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 (NOAEL) have been observed. 

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

health professionals and citizens alike. 

Estimates of exposure levels posing minimal risk to humans (MRLs) have been made, where data were 

believed reliable, for the most sensitive noncancer effect for each exposure duration. MRLs include 

adjustments to reflect human variability and extrapolation of data from laboratory animals to humans. 

Although methods have been established to derive these levels (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 A). 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 

Otto Fuel II is a torpedo propellant that is composed of a mixture of approximately 75% propylene 

glycol dinitrate, 2% 2-nitrodiphenylamine, and 23% dibutyl sebacate. The studies described in this 

section include both those concerning exposures to the mixture, Otto Fuel II, as well as those 

concerning exposures to the individual components of this mixture. 

Propylene glycol dinitrate is the only component of Otto Fuel II with significant volatility. However, 

inhalation exposures to the other components of Otto Fuel II are considered in this section because 

mists of Otto Fuel II may be generated, and inhalation of aerosol particles in the mists is possible. 
OTTO FUEL II AND ITS COMPONENTS 11 

2. HEALTH EFFECTS
 

Occupational exposure to Otto Fuel II may result in simultaneous inhalation and dermal exposures. 

Thus, many of the effects reported in occupational studies in this section may be due, in part, to 

dermal exposure to Otto Fuel II. 

2.2.1.1 Death 

No studies were located regarding death in humans after inhalation exposure to Otto Fuel II or its 

individual components. 

No studies were located regarding death in animals after inhalation exposure to either Otto Fuel II or 

two of its components, 2-nitrodiphenylamine, and dibutyl sebacate. However, information was 

available regarding death in animals following inhalation exposure to propylene giycol dinitrate. 

These studies indicate that differences in species sensitivity to the lethal effects of propylene glycol 

dinitrate may exist. 

For example, exposure to concentrations of propylene glycol dinitrate as high as 200 ppm.for 4 hours 

has been tolerated in rats without any toxic signs, and continuous (24 hours/day) exposure of rats, 

guinea pigs, and dogs to 35 ppm for 90 days produced no treatment-related deaths in any of these 

species (Jones et al. 1972). However, continuous exposure of a rabbit to 35 ppm of propylene glycol 

dinitrate resulted in the death of the rabbit on the 4th day (Jones et al. 1972). The rabbit appeared to 

be cyanotic 6 hours prior to death. One out of 9 squirrel monkeys exposed.continuously to 35 ppm 

died on the 31st day of exposure, and a squirrel monkey exposed to 61 ppm of propylene glycol 

dinitrate for 23 hours/day died on the third day of exposure (Jones et al. 1972). 

In longer-term studies, intermittent (6 hours/day, 5 days/week) exposure of rats and mice to 35 ppm of 

propylene glycol dinitrate for 1 year resulted in no increase in deaths over the death rates of controls 

in either species during the exposure period or in the l-year postexposure observation period (Air 

Force 1985a). Also, a 14-month exposure of dogs to 0.2 ppm propylene glycol dinitrate for 

6 hours/day, 5 days/week, caused no treatment-related deaths (Air Force 1985a). Test atmospheres in 

the Air Force study were generated by volatilizing propylene glycol dinitrate from Otto Fuel II. 
OTTO FUEL II AND ITS COMPONENTS 12 

2. HEALTH EFFECTS 

2.2.1.2 Systemic Effects 

The highest NOAEL values and all reliable LOAEL values for each study for each end point for 

propylene glycol dinitrate are recorded in Table 2-l and plotted in Figure 2-l. 

Respiratory Effects. No studies were located regarding respiratory effects in humans after 

inhalation exposure to 2-nitrodiphenylamine or dibutyl sebacate. However, information was available 

regarding respiratory end points following inhalation exposure to Otto Fuel II and propylene glycol 

dinitrate. 

Approximately 6% of a group of 87 torpedo maintenance workers with 1-132 months (average 

47 months) of occupational exposure to Otto Fuel II reported experiencing dyspnea during past 

exposures (Horvath et al. 1981). However, it is unknown whether the incidence of this effect was 

increased relative to controls. Airway irritation was reported by incinerator workers with between I7 

months and 3 years of experience (ATSDR 1990). In addition, one individual living near the 

incinerator was reported to have had bronchiolar obstruction; possibly related to inhaling incinerator 

fumes. However, only approximately 10% of the material incinerated was Otto Fuel II; other solvents 

and corrosive materials were also incinerated. Thus, the irritation and bronchiolar damage described in 

the report by ATSDR (I 990) cannot be entirely attributed to Otto Fuel II exposure with certainty. 

Nasal congestion was reported by approximately 31% of the torpedo maintenance workers in the study 

by Horvath et al. (1981). Although respiratory tissues were affected, this symptom is most likely due 

to a direct vasodilatory effect of the propylene glycol dinitrate on blood vessels of the nasal mucosa 

and not to an effect on respiratory function. Therefore, nasal congestion is also discussed below as a 

symptom of a cardiovascular response. 

Volunteers exposed, in a single session lasting between 1and 8 hours, to propylene glycol dinitrate 

atmospheres generated by volatilizing Otto Fuel II experienced no effects on respiratory function as 

measured using computerized spirometry (Stewart et al. 1974). Exposure levels in the study by 

Stewart et al. (I 974) were measured by monitoring atmospheric concentrations of propylene glycol 

dinitrate. Exposure to concentrations of propylene glycol dinitrate in this study as high as I.5 ppm for 

a single 3.2-hour period or 0.2 ppm for 7.5-8 hours/day for 5 days caused no measurable decrease in 

the respiratory function parameters measured. 










OTTO FUEL II AND ITS COMPONENTS 23 

2. HEALTH EFFECTS 

No studies were located regarding respiratory effects in animals after inhalation exposure to Otto Fuel 

II, 2-nitrodiphenylamine, or dibutyl sebacate. However, studies were located that examined respiratory 

end points in animals following inhalation exposure to propylene glycol dinitrate. 

In general, inhalation exposure of animals to propylene glycol dinitrate resulted in no gross or 

histologically apparent adverse effects on the tissues of the respiratory system. Studies examining the 

effects of a 90-day, 24-hour/day exposure of rats, monkeys, and dogs to 35 ppm propylene glycol 

dinitrate showed no treatment-related gross or histopathological alterations in the lungs (Jones et al. 

1972). In addition, a l-year exposure of mice to 35 ppm propylene glycol dinitrate and a 14-month 

exposure of dogs to 0.2 ppm propylene glycol dinitrate for 6 hours/day, 5 days/week, produced no 

gross or histopathological changes in the tissues of the nasal cavity, larynx, trachea,. bronchi, or lungs 

(Air Force 198Sa). In this Air Force study (1985a), the atmosphere containing propylene glycol 

dinitrate was generated by volatilizing Otto Fuel II. The study is limited, however, in that the controls 

were not sham exposed. In addition, the control mice developed intercurrent ulcerative dermatitis, 

thereby confounding the conclusions that can be drawn. 

Adverse respiratory effects were, however, observed in two studies. In the first study, exposure of 

guinea pigs to 16 ppm propylene glycol dinitrate for 24 hours/day for 90 days resulted in foci of 

pulmonary hemorrhage in both males and females (Jones et al. 1972). In the other study, exposure of 

rats of both sexes to propylene glycol dinitrate for 6 hours/day, 5 days/week, for I year, resulted in 

mild degeneration of the nasal epithelium at concentrations as low as 0.2 ppm and pulmonary 

inflammation only in females at 35 ppm (Air Force 1985a). After a l-year recovery period, the effects 

on the nasal epithelium and lungs were no longer significantly increased. As noted above, the 

propylene glycol dinitrate atmospheres in the Air Force study were generated by voIatilizing 

Otto Fuel II. Also, controls were not sham exposed in this study; thus, it is difficult to determine 

whether the effects observed on the nasal epithelium and lungs were related specifically to propylene 

glycol dinitrate exposure. 

Cardiovascular Effects. No studies were located regarding cardiovascular effects in humans 

following inhalation exposure to 2-nitrodiphenylamine alone or dibutyl sebacate alone. However, 

information was available regarding cardiovascular end points following inhalation exposure to Otto 

Fuel II or propylene glycol dinitrate. 
OTTO FUEL II AND ITS COMPONENTS 24 

2. HEALTH EFFECTS
 

Symptoms identified with nitrate-induced vasodilation or compensatory vasoconstriction have been 

observed in studies examining human exposure to Otto Fuel II and its major component, propylene 

glycol dinitrate. For example, headaches of presumed vascular origin were experienced either 

frequently or occasionally by 65% of 87 torpedo maintenance workers with l-132 months (average of 

47 months) of exposure to Otto Fuel II (Horvath et al. 1981). However, it was not reported whether 

the incidence of this effect was greater than in controls. Also, workers at an incinerator where Otto 

Fuel II was burned reported that they were able to identify exposures to Otto Fuel II by the 

characteristic vasodilatory headache (ATSDR 1990). 

Experimental exposure of volunteers to atmospheres of propylene glycol dinitrate generated by 

volatilizing this chemical from Otto Fuel II, resulted in headaches of presumed vascular origin 

(Stewart et al. 1974). The headaches began as mild frontal headaches and became progressively worse 

and throbbing in nature. Headaches were reported by some subjects exposed to concentrations of 

propylene glycol dinitrate as low as 0.2 ppm for up to 8 hours. With repeated exposures, the severity 

and frequency of headaches was observed to decrease. By analogy with the effects of other aliphatic 

nitrates, the headaches are most likely the result of vasodilation of the meningeal blood vessels 

(Nickerson 1975). 

Nasal congestion was also reported by 31% of the torpedo maintenance workers interviewed by 

Horvath et al. (1981) as an occasional or frequent symptom associated with Otto Fuel II exposure. 

This effect was considered to be cardiovascular in origin because it was most likely the result of 

vasodilation of blood vessels in the nasal mucosa and sinuses. 

Lowered blood pressures were observed in workers at an incineration facility at which Otto Fuel II 

comprised approximately 10% of the waste burned (ATSDR 1990). However, this effect cannot be 

directly attributed to Otto Fuel II exposure because of the number of other materials incinerated at the 

facility. An increase in diastolic pressure was observed during the last 2-3 hours of exposure in 

volunteers exposed to 0.5 ppm propylene glycol dinitrate for 8 hours (Stewart et al. 1974) possibly 

indicating compensatory vasoconstriction. 

Based on the observation that nitrated esters cause a compensatory vasospasm that may produce 

coronary insufficiency upon withdrawal from exposure (Carmichael and Lieben 1963; Morton 1977), a 

study was conducted to examine the incidence of coronary symptoms among 1,352 Navy torpedoman’s 
OTTO FUEL II AND ITS COMPONENTS 25 

2. HEALTH EFFECTS 

mates with potential exposure to Otto Fuel II (Forman et al. 1987). This study demonstrated a 

significantly greater incidence of hospitalizations for myocardial infarctions or angina pectoris in the 

exposed torpedoman’s mates than in 14,336 unexposed torpedoman’s mates or 29,129 fire control 

technicians. Palpitations and chest pain were also reported by the workers in the study by Horvath et 

al. (1981). Of the 87 exposed workers that were interviewed, 10% reported experiencing palpitations 

and 4% reported experiencing chest pain. However, it was not reported whether the incidence of these 

symptoms was greater than in the controls. Chest pain and tightness were also reported by several 

workers at an incinerator where Otto Fuel II was burned (ATSDR 1990). One of these workers was 

diagnosed with nitrate withdrawal angina when cardiac catheterization failed to reveal any other cause. 

However, causative agents other than Otto Fuel II cannot be eliminated because of the large number of 

other hazardous wastes also burned at the facility. 

No changes were observed in the electrical activity or mechanical performance of the hearts of 

9 subjects exposed to up to 0.5 ppm propylene glycol dinitrate for 8 hours, 1.5 ppm propylene glycol 

dinitrate for 3.2 hours, or 0.2 ppm propylene glycol dinitrate for 5 days for 7.5-8 hours/day (Stewart 

et al. 1974). Tests were conducted during exposure, and baseline studies were repeated 16 hours 

following each exposure. 

No studies were located regarding cardiovascular effects in animals after inhalation exposure to Otto 

Fuel II or two of its components, 2-nitrodiphenylamine and dibutyl sebacate. However, limited 

information was located regarding cardiovascular effects in animals following inhalation exposure to 

propylene glycol dinitrate. 

Relative to a pre-exposure period, anesthetized rats exposed nose-only to up to 94 ppm propylene 

glycol dinitrate vapors for 30-45 minutes exhibited no changes in mean systolic pressure during 

exposure (Godin et al. 1993). Exposure of monkeys to 74-103 ppm of propylene glycol dinitrate for 

6 hours resulted in pallor and cold extremities of the monkeys during exposure (Jones et al. 1972), 

suggesting hypotension and compensatory vasoconstriction. The monkeys recovered within 

30-45 minutes after termination of the exposure. No other studies reported effects associated with 

changes in vascular tone. However, two studies found no gross or microscopically apparent damage to 

the heart following inhalation exposure to propylene glycol dinitrate. In one study, no gross or 

histopathologic changes in the heart were observed following exposure of rats, guinea pigs, dogs, or 

monkeys to 35 ppm propylene glycol dinitrate for 24 hours/day, for 90 days (Jones et al. 1972). In 
OTTO FUEL II AND ITS COMPONENTS 26 

2. HEALTH EFFECTS 

the other study, no gross or histopathologic changes in the heart were observed during routine 

examination of tissues from rats or mice exposed to 35 ppm propylene glycol dinitrate for 6 hours/day, 

5 days/week, for 1 year, or from dogs exposed to 0.2 ppm propylene glycol dinitrate for 6 hours/day, 

5 days/week, for 14 months (Air Force 1985a). The test atmospheres in the Air Force study were 

generated by volatilizing propylene glycol dinitrate from Otto Fuel II. 

Gastrointestinal Effects. No studies were located regarding gastrointestinal effects in humans 

after inhalation exposure to Otto Fuel II or its components. 

No studies were located regarding gastrointestinal effects in animals after inhalation exposure to Otto 

Fuel II or two of its components, 2-nitrodiphenylamine or dibutyl sebacate. However, extremely 

limited information was located regarding potential gastrointestinal effects resulting from inhalation 

exposure of animals to propylene glycol dinitrate. 

Routine gross and histopathological examination of the esophagus, stomach, duodenum, ileum, colon, 

and anus of rats and mice exposed to 35 ppm propylene glycol dinitrate for 1 year, 6 hours/day, 

5 days/week, and then observed for an additional year post-exposure revealed no treatment-related 

effects (Air Force 1985a). Similarly, no treatment-related gross or microscopic changes were observed 

in this study in dogs exposed to 0.2 ppm propylene glycol dinitrate for 14 months, 6 hours/day, 

5 days/week. 

Hematological Effects. No studies were located regarding hematological effects in humans after 

inhalation exposure to Otto Fuel II or two of its components, 2-nitrodiphenylamine and dibutyl 

sebacate. However, methemoglobin levels were examined in one study in which volunteers were 

exposed to concentrations of 1.5 ppm propylene glycol dinitrate for 3.2 hours or 0.2 ppm for 7.5-8 hours/day for 5 

days (Stewart et al. 1974). Inhalation exposure at these levels was insufficient to elevate methemoglobin levels 

above control values. Test atmospheres in this study were generated by volatilizing propylene glycol dinitrate from 

Otto Fuel II. 

No studies were located regarding hematological effects in animals after inhalation exposure to Otto 

Fuel II or two of its components, 2-nitrodiphenylamine and dibutyl sebacate. However, hematological 

end points were assessed in several studies following inhalation exposure of animals to propylene glycol dinitrate. 
OTTO FUEL II AND ITS COMPONENTS 27 

2. HEALTH EFFECTS
 

Elevated methemoglobin levels were observed in a number of acute-, intermediate-, and chronic-duration 

exposure studies in which animals were exposed to propylene glycol dinitrate. Methemoglobin levels of 23.5% 

were measured in rats immediately following a 4-hour exposure to 200 ppm propylene glycol dinitrate (Jones et al. 

1972). Cyanosis and elevated methemoglobin levels (18.2%) were observed in a rabbit exposed to 35 ppm 

propylene glycol dinitrate for 23 hours/day for 4 days (Jones et al. 1972). This animal died on the 4th day of 

exposure. At the time of death, the methemoglobin level was 32.8%. Similarly, the methemoglobin level in a 

squirrel monkey that died following exposure to 61 ppm propylene glycol dinitrate for 23 hours/day for 3 days was 

40.2% at the time of death (Jones et al. 1972). 

Continuous (24 hours/day) exposure of rats, guinea pigs, dogs, and monkeys to propylene glycol 

dinitrate for 90 days resulted in elevated methemoglobin levels during exposure and histopathologic 

evidence of hemolysis in all four species (Jones et al. 1972). At concentrations as low as 10 ppm, 

hemosiderin deposits (indicating phagocytosis of oxidized hemoglobin released from hemolyzed red 

cells) were observed in kidneys and livers from dogs and in kidneys from some rats. At 16 ppm, 

hemosiderin deposits were observed in the liver of dogs and monkeys; at 35 ppm, in addition to the 

liver and kidneys, heavy hemosiderin deposits were observed in the spleens of these animals. At 

35 ppm, all four species exhibited elevated methemoglobin levels. Postexposure values for leukocytes, 

hemoglobin, and hematocrit were not significantly altered in rats, guinea pigs, or monkeys, but dogs 

exposed to 35 ppm experienced an average 63% decrease in hemoglobin and a 37% decrease in 

hematocrit (Jones et al. 1972). 

Chronic intermittent (6 hours/day, 5 days/week) exposure of dogs to 0.2 ppm propylene glycol 

dinitrate for 14 months resulted in a small but statistically significant increase in methemoglobin levels 

(1-3% above normal levels) (Air Force 1985a). Exposure at this level also caused anemia in the dogs. 

At the first 2-week blood test, a decreased hematocrit and hemoglobin content was observed, and at 

4 weeks, a significant decrease in the number of red blood cells and reticulocytes was also observed. 

These decreases were maintained throughout the duration of the study. Despite the indication that 

hematopoiesis was affected (low reticulocyte count in the presence of reduced red cell count), samples 

of bone marrow taken at necropsy showed no effect on the blood forming cells and no effect was 

observed on the spleen. Additional tests performed to determine the nature of the anemia revealed 

neither excessive hemoglobin denaturation nor increase in the fragility of the erythrocyte membrane. 

No Heinz bodies (precipitates of denatured hemoglobin within the red blood cell) were observed, and 
OTTO FUEL II AND ITS COMPONENTS 28 

2. HEALTH EFFECTS
 

the erythrocytes demonstrated only a Slight increase in osmotic fragility at the lowest osmotic strengths 

tested. Rats exposed to 35 ppm propylene glycol dinitrate for 1 year, 6 hours/day, 5 days/week, also 

demonstrated a small but statistically significant increase in methemoglobin levels (1-2% above 

normal) during exposure, but no consistent effects on the hematocrit, hemoglobin, or red blood cell 

content of the blood were observed (Air Force 1985a), indicating the increased sensitivity of the dog 

relative to the rat. The test atmospheres in the Air Force study were generated by volatilizing 

propylene glycol dinitrate from Otto Fuel II. 

Musculoskeletal Effects. No studies were located regarding musculoskeletal effects in humans 

after inhalation exposure to propylene glycol dinitrate, 2-nitrodiphenylamine, or dibutyl sebacate. 

However, a “seronegative arthritis” was diagnosed in several workers from an incinerator at which 

10% of the material burned was Otto Fuel II (ATSDR 1990). Because of the large number of other 

wastes handled at the facility, the arthritis cannot be ascribed to Otto Fuel II exposure with any 

certainty. 

No studies were located regarding musculoskeletal effects in animals after inhalation exposure to Otto 

Fuel II or two of its components, 2-nitrodiphenylamine and dibutyl sebacate. However, effects on the 

skeletal system were observed in one animal study following inhalation exposure to propylene glycol 

dinitrate. 

An increased incidence of osteosclerosis of cortical bone (stemebrae, vertebrae and/or femur) was 

observed in female rats 1 year after they had been exposed to 35 ppm propylene glycol dinitrate for 

1 year, 6 hours/day, 5 days/week (Air Force 1985a). This effect was attributed by the study authors to 

altered estrogen levels in these animals, but no data on estrogen levels were presented to support this 

assertion. Routine gross and histopathologic examination of the thigh muscle and stemebrae, vertebrae, or femur of 

mice exposed to 35 ppm propylene glycoi dinitrate for 1 year, 6 hours/day, 5 days/week, and then observed for an 

additional year, or of dogs exposed to 0.2 ppm propylene glycol dinitrate for 14 months, 6 hours/day, 5 days/week, 

revealed no abnormalities in these tissues (Air Force 1985a). The test atmospheres in this study were generated by 

volatilizing propylene glycol dinitrate from Otto Fuel II. 

Hepatic Effects. No studies were located regarding hepatic effects in humans after inhalation 

exposure to propylene glycol dinitrate, 2-nitrodiphenylamine, or dibutyl sebacate. However, transient 
OTTO FUEL II AND ITS COMPONENTS 29 

2. HEALTH EFFECTS 

elevations were noted in unspecified parameters assessing liver function in several incinerator workers 

at a facility at which approximately 10% of the waste handled was Otto Fuel II (ATSDR 1990). This 

effect cannot be definitively attributed to Otto Fuel II because the other wastes incinerated included a 

number of solvents. 

No studies were located regarding hepatic effects in animals after inhalation exposure to Otto Fuel II 

or two of its components, 2-nitrodiphenylamine and dibutyl sebacate. However, several animal studies 

provided information regarding hepatic end points following inhalation exposure to propylene glycol 

dinitrate. 

Continuous (24 hours/day) exposure of rats, guinea pigs, dogs, and monkeys to propylene glycol 

dinitrate for 90 days has been shown to result in degenerative changes in the liver (Jones et al. 1972). 

Concentrations of propylene glycol dinitrate as low as 10 ppm in rats and guinea pigs, and 16 ppm in 

dogs and monkeys, have been shown to cause fatty changes in the livers of these animals. Changes 

observed at 35 ppm included vacuolar changes in the livers of guinea pigs, focal liver necrosis in 

female rats (male rats were unaffected), and vacuolar change, mononuclear, cell infiltrates, and focal 

necrosis in the livers of monkeys and dogs (Jones et al. 1972). In addition, bromosulfophthalein 

retention was increased in one of the two dogs exposed at 35 ppm, indicating depressed hepatic 

function. In dogs and monkeys, the degenerative changes were commonly associated with heavy 

deposition of hemosiderin in the liver. It is unclear whether these effects are causally related. 

In contrast, routine gross and histopathological examination of livers from animals that were 

intermittently exposed to propylene glycol dinitrate for intermediate or chronic durations did not reveal 

any adverse effects. For example, gross and histopathological examination of livers of male rats 

exposed to 10 ppm propylene glycol dinitrate for 6 weeks, 7 hours/day, 5 days/week (Jones et al. 

1972) or 35 ppm propylene glycol dinitrate for I year, 6 hours/day, 5 days/week (Air Force 1985a) 

showed no treatment-related effects. The 6-week study is limited in that no controls were used. Gross 

and histopathological examination of livers of mice exposed for I year, 6 hours/day, 5 days/week, to 

35 ppm propylene glycol dinitrate or dogs exposed for 14 months, 6 hours/day, 5 days/week, to 

0.2 ppm propylene glycol dinitrate revealed no adverse treatment-related effects (Air Force 1985a). 

The test atmospheres in the Air Force study were generated by volatilizing propylene glycol dinitrate 

from Otto Fuel II. 
OTTO FUEL II AND ITS COMPONENTS 30 

2. HEALTH EFFECTS 

Renal Effects. No studies were located regarding renal effects in humans after inhalation exposure 

to Otto Fuel II or its components. 

No studies were located regarding renal effects in animals after inhalation exposure to Otto Fuel II or 

two of its components, 2-nitrodiphenylamine and dibutyl sebacate. However, several studies have 

examined the renal toxicity of propylene glycol dinitrate following inhalation exposure. 

Continuous (24 hours/day) exposure of rats to 35 ppm of propylene glycol dinitrate for 90 days 

resulted in an increased incidence of acute tubular necrosis in female, but not male, rats (Jones et al. 

1972). In addition, continuous exposure of monkeys to propylene glycol dinitrate at concentrations as 

low as I6 ppm for 90 days resulted in increased serum urea nitrogen and decreased serum alkaline phosphatase 

(indicating the possibility of renal dysfunction). However, no gross or histological evidence of degenerative 

changes in the kidneys was observed in monkeys exposed to concentrations as high as 35 ppm for 90 days (Jones et 

al. 1972). The renal toxicity observed in these cases may have been caused by hemoglobinuria resulting from 

massive hemolysis (Cotran et al. 1989). In support of this is the observation that continuous exposure of rats to 

concentrations as low as 10 ppm and monkeys to concentrations as low as 16 ppm of propylene glycol dinitrate for 

90 days resulted in an increase in hemosiderin deposits in the proximal convoluted tubules of the kidneys (Jones et 

al. 1972). Heavy hemosiderin deposits were observed in the kidneys of monkeys continuously exposed to 

35 ppm propylene glycol dinitrate for 90 days. These deposits were attributed to increased destruction 

of erythrocytes (see also Hematological Effects above). Arguing against the role of hemoglobinuria in 

the renal toxicity is the observation that dogs exposed to concentrations of propylene glycol dinitrate 

as low as 10 ppm also had increased hemosiderin deposits in the proximal convoluted tubules of the 

kidneys but no clinical or microscopic evidence of renal dysfunction at concentrations as high as 

35 ppm (Jones et al. 1972). Thus, it is unclear whether the observed renal effects in female rats and 

monkeys were the result of hemoglobinuria or a direct toxic effect of propylene glycol dinitrate on the 

kidneys. 

Other studies in which intermittent exposures were used have not detected renal toxicity. Routine 

gross and histopathological examination of kidneys from male rats that have been intermittently 

(7 hours/day, 5 days/week, for 6 weeks) exposed to 10 ppm of propylene glycol dinitrate by inhalation 

(Jones et al. 1972) or from rats or mice that have been intermittently (6 hours/day, 5 days/week, for 

1 year) exposed by inhalation to 35 ppm propylene glycol dinitrate (Air Force 1985a) did not reveal 
OTTO FUEL II AND ITS COMPONENTS 31 

2. HEALTH EFFECTS
 

any adverse effects. The 6-week study by Jones et al. (1972) is limited in that no controls and only 

male rats were used. The test atmospheres in the Air Force study were generated by volatilizing 

propylene glycol dinitrate from Otto Fuel II. 

Endocrine Effects. Limited information is available regarding endocrine effects after inhalation 

exposure to Otto Fuel II and its components. No gross or histopathologic alterations were observed in 

the adrenals of two male dogs continuously exposed to up to 35 ppm propylene glycol dinitrate for 

90 days (Jones et al. 1972). In a chronic-duration study, no gross or microscopical alterations were 

observed in the thyroid, parathyroid, and pituitary glands from mice and rats exposed for a year to 

35 ppm of propylene glycol dinitrate vapors 6 hours/day, 5 days/week, or in dogs exposed to 0.2 ppm 

using a similar protocol (Air Force 1985a). 

Dermal Effects. No studies were located regarding dermal effects in humans after inhalation 

exposure to propylene glycol dinitrate, 2-nitrodiphenylamine or dibutyl sebacate. Eczema, dermatitis 

with macropapular rashes, and sweating with no apparent cause were reported by incinerator workers 

at a facility at which Otto Fuel II made up approximately 10% of the waste material handled (ATSDR 

1990). However, other materials processed at the incinerator could have been responsible for these 

effects. 

No studies were located regarding dermal effects in animals after inhalation exposure to Otto Fuel II, 

2-nitrodiphenylamine and dibutyl sebacate. No adverse effects of inhalation exposure to propylene 

glycol dinitrate on the skin were reported in rats or mice exposed to 35 ppm for 1 year, 6 hours/day, 

5 days/week, or in dogs exposed to 0.2 ppm for 14 months, 6 hours/day, 5 days/week (Air Force 

1985a). The test atmospheres in the Air Force study were generated by volatilizing propylene glycol 

dinitrate from Otto Fuel II. 

Ocular Effects. No studies were located regarding ocular effects in humans after inhalation 

exposure to 2-nitrodiphenylamine and dibutyl sebacate. However, eye irritation has been reported by 

workers occupationally exposed to Otto Fuel II and volunteers experimentally exposed to propylene 

glycol dinitrate. Slight eye irritation was reported by one of twelve volunteers exposed to atmospheres 

containing 0.2 propylene glycol dinitrate in an exposure chamber for 8 hours (Stewart et al. 1974). An 

exposure level of 1.5 ppm propylene glycol dinitrate caused frank eye irritation in 8 out of 8 subjects 

after 40 minutes in the chamber (Stewart et al. 1974). However, the same investigators also reported 
OTTO FUEL II AND ITS COMPONENTS 32 

2. HEALTH EFFECTS
 

that none of 9 volunteers exposed to 0.2 ppm propylene glycol dinitrate 8 hours/day for 5 days 

complained of eye irritation (Stewart et al. 1974). Eye irritation was also reported as an occasional or 

frequent symptom experienced by 26% of a group of 87 workers occupationally exposed to Otto 

Fuel II (Horvath et al. 1981). However, the incidence of this effect was not contrasted with the 

incidence in an unexposed population. Eye irritation was also a common complaint among incinerator 

workers at a facility at which Otto Fuel II made up approximately 10% of the waste materials handled 

(ATSDR 1990). However, other materials processed at the incinerator could have been responsible for 

these effects. 

No studies were located regarding ocular effects in animals after inhalation exposure to Otto Fuel II or 

two of its components, 2-nitrodiphenylamine and dibutyl sebacate. However, limited information on 

ocular end points was found in one study in which animals were exposed to propylene glycol dinitrate 

by inhalation. 

Pupillary dilation was observed to increase from slight to moderate in monkeys exposed to 

atmospheres containing 35 ppm propylene glycol dinitrate for 24 hours/day for 90 days (Jones et al. 

1972). It was not stated whether this effect was a direct effect on the eyes or whether the effect may 

have been neurologically mediated (see also Section 2.2.1.4). 

Body Weight Effects. Body weight effects after inhalation exposure to Otto Fuel II or its 

components are limited to studies in animals exposed to propylene glycol dinitrate. No significant 

alterations in body weight gain were reported in rats, guinea pigs, dogs and monkeys exposed 

continuously to 35 ppm propylene glycol dinitrate vapors for 90 days (Jones et al. 1972). Similar 

results were reported in rats and mice exposed to 35 ppm and dogs exposed to 0.2 ppm intermittently 

for approximately one year (Air Force 1985a). 

2.2.1.3 Immunological and Lymphoreticular Effects 

No studies were located regarding immunological effects in humans after inhalation exposure to 

propylene glycol dinitrate, 2-nitrodiphenylamine, or dibutyl sebacate. However, an immunological end 

point was observed in a situation where workers were exposed to Otto Fuel II. 
OTTO FUEL II AND ITS COMPONENTS 33 

2. HEALTH EFFECTS
 

A child of a worker at an incinerator at which Otto Fuel II was processed developed asthma (ATSDR 

1990). The asthma was linked to materials handled at the incinerator because when the father of the 

child stopped bringing his work clothing home, the child’s condition improved. However, Otto Fuel II 

comprised only approximately 10% of the wastes handled at the facility; thus, other materials may 

have triggered the reaction in the child. The possibility also exists that the asthma-like response may 

have been caused by tetryl particles activating nerve receptors which triggered vagal reflexes inducing 

bronchoconstriction. 

No studies were located regarding immunological effects in animals after inhalation exposure to Otto 

Fuel II or two of its components, 2-nitrodiphenylamine and dibutyl sebacate. However, limited 

information was located regarding immunological effects of propylene glycol dinitrate in animals after 

inhalation exposure. 

No studies that directly examined immunological function were located. However, no gross or 

histopathoiogic alterations were observed in the spleens from rats and guinea pigs exposed 

continuously to up to 35 ppm propylene glycol dinitrate for 90 days (Jones et al. 1972). Dogs and 

monkeys exposed in the same fashion showed heavy iron deposits in their spleens at 35 ppm, but not 

at 16 ppm or less (Jones et al. 1972). Total and differential leukocyte counts and routine gross and 

histopathological examination of the mandibular and mesenteric lymph nodes, spleen and thymus were 

normal in rats and mice exposed to 35 ppm propylene glycol dinitrate for 6 hours/day, 5 days/week, 

for 1 year, and in dogs exposed to 0.2 ppm for 6 hours/day, 5 days/week, for 14 months (Air Force 

1985a). Test atmospheres in the Air Force study were generated by volatilizing propylene glycol 

dinitrate from Otto Fuel II. 

The highest NOAEL values for immunologic effects of propylene glycol in rats, mice, guinea pigs, 

monkeys, and dogs in intermediate-duration and chronic-duration studies are recorded in Table 2-l and 

plotted in Figure 2- 1. 

2.2.1.4 Neurological Effects 

No studies were located regarding neurological effects in humans after inhalation exposure to 

2-nitrodiphenylamine or dibutyl sebacate. However, neurological effects were reported in studies 
OTTO FUEL II AND ITS COMPONENTS 34 

2. HEALTH EFFECTS 

examining occupational exposure to Otto Fuel II and experimental inhalation exposure to propylene 

glycol dinitrate. 

Studies designed to assess the neurological effects of Otto Fuel II and its component, propylene glycol 

dinitrate, in humans have indicated that an alteration of central nervous system activity may result 

from occupational exposures. In one study, workers were given tests of balance and oculomotor 

performance before and after a torpedo maintenance procedure (Horvath et al. 1981). The 

maintenance procedures were approximately 30-60 minutes in duration, and propylene glycol dinitrate 

concentrations measured in the work area ranged from 0 to 0.22 ppm (88% of the concentrations 

measured were less than 0.1 ppm and 50% were less than 0.05 ppm). Although no statistically 

significant decrement in balance was observed, some tests of oculomotor performance were 

significantly altered. Mean saccade velocity was significantly decreased and mean saccade delay was 

significantly increased in the workers. Saccade accuracy and smooth pursuit were not significantly 

affected. A decrease in saccade velocity and an increase in saccade delay have been observed in cases 

of central nervous system depression. Consistent with this effect was the observation that volunteers 

exposed to various concentrations of propylene glycol dinitrate also exhibited central nervous system 

effects (Stewart et al. 1974). Exposure to 0.2 ppm propylene glycol dinitrate for 1-8 hours altered the 

visual evoked responses measured in the subjects. With repeated 7.5-8 hour exposures to 0.2 ppm, 

the change in the visual evoked response was observed to increase in magnitude indicating a 

cumulative effect. Exposure to 0.5 ppm for 8 hours resulted in nausea, dizziness, and more markedly 

altered visual evoked responses. At this concentration, the subjects had significantly altered ability to 

perform the modified Romberg and heel-to-toe tests. At the highest concentration tested, 1.5 ppm, 

subjects experienced coordination deficits and altered visual evoked responses although they were 

exposed for less than 4 hours. The effects on visual evoked responses and coordination were 

consistent with central nervous system depression. The central nervous system effects noted in these 

studies are consistent with the reports of dizziness and loss of balance reported by 13% and 1%, 

respectively, of workers occupationally exposed to Otto Fuel II (Horvath et al. 1981). However, it is 

unknown whether the incidence of the effects reported by exposed workers was significantly greater 

than in controls. No significant differences between the results of tests of oculomotor function or 

coordination and balance were observed when workers occupationally exposed to Otto Fuel II for 

1-132 months (47 months average) were compared to clerical and technical personnel with no known 

exposure to Otto Fuel II (Horvath et al. 198 I). 
OTTO FUEL II AND ITS COMPONENTS 35 

2. HEALTH EFFECTS
 

An unspecified number of workers at an incinerator at which Otto Fuel II comprised approximately 

10% of the waste materials processed, were diagnosed with a number of neurological disorders 

(ATSDR 1990). These included mood disorders, cerebellar dysfunction (ataxia, tremor, nystagmus), 

cognitive disorders, memory loss, and possible vestibular dysfunction. Magnetic resonance imaging 

showed that two of these workers had cerebellar and cortical atrophy. However, the effects observed 

cannot be attributed to Otto Fuel II with certainty because a large number of solvents and other wastes 

were also handled at the incinerator. 

Headaches have frequently been reported both by workers occupationally exposed to Otto Fuel II and 

volunteers experimentally exposed to propylene glycol dinitrate (ATSDR 1990; Horvath et al. 1981 ; 

Sfewart et al. 1974). The headaches are most likely associated with meningeal blood vessel dilation 

(Nickerson 1975) (see also Cardiovascular Effects in Section 2.2.1.2). 

No studies were located regarding neurological effects in animals after inhalation exposure to Otto 

Fuel II or two of its components, 2-nitrodiphenylamine and dibutyl sebacate. However, several studies 

have examined neurological end points following inhalation exposure of animals to propylene glycol 

dinitrate. 

Monkeys exposed to concentrations of propylene glycol dinitrate as low as 2 ppm for 4 hours have 

demonstrated altered visual evoked responses (Mattsson et al. 1981); however, studies in animals have 

provided only very limited gross behavioral evidence of neurological effects of propylene glycol 

dinitrate. For example, exposure of an unspecified number of monkeys to 74-103 ppm propylene 

glycol dinitrate for 6 hours resulted in semiconsciousness and clonic convulsions (Jones et al. 1972). 

Recovery from these effects was observed within 30-45 minutes after termination of exposure. Also, 

monkeys exposed to 39 ppm propylene glycol dinitrate for 24 hours/day, for 90 days, experienced an 

increase in pupillary dilation from slight to moderate (Jones et al. 1972). No effect on visual 

discrimination or visual acuity was observed. This study was limited by the small number of animals 

used. 

Other tests have not demonstrated neurological effects of propylene glycol dinitrate in animals. 

Performance of monkeys in an operant avoidance behavioral test was not affected by inhalation 

exposure to propylene glycol dinitrate at concentrations as high as 33 ppm for 4 hours or by exposure 

to concentrations as high as 4.23 ppm for 23 hours/day in an increasing dose paradigm lasting 
OTTO FUEL II AND ITS COMPONENTS 36 

2. HEALTH EFFECTS
 

125 days (Mattsson et al. 1981). This study is limited in that only two monkeys were used. No gross 

or histopathological effects have been observed in sections from brain and spinal cord or sciatic nerve 

in dogs and monkeys exposed to 35 ppm, 24 hours/day, for 90 days (Jones et al. 1972), in rats and 

mice exposed to 35 ppm, 6 hours/day, 5 days/week, for I year, and in dogs exposed to 0.2 ppm, 

6 hours/day, 5 days/week, for 14 months (Air Force 1985a). 

The highest NOAEL values and all reliable LOAEL values for neurological effects of propylene glycol 

dinitrate in each species and duration category are recorded in Table 2- 1 and plotted in Figure 2- 1. 

2.2.1.5 Reproductive Effects 

No studies were located regarding reproductive effects in humans after inhalation exposure to the 

individual components of Otto Fuel II. However, a study compared the incidence of spontaneous and 

induced abortions in female Navy enlisted personnel exposed to Otto Fuel II with that in two groups 

of enlisted female workers nat exposed to Otto Fuel II and found no increase (Forman 1988). The 

number of female workers exposed to Otto Fuel II in this study was extremely small, limiting the 

sensitivity of the comparison. 

No studies were located that examined the effects of Otto Fuel II or its individual components on 

reproductive performance in animals after inhalation exposure. Although no information was located 

regarding reproductive performance, limited data were available regarding effects of propylene glycol 

dinitrate on the gross and microscopic structure of reproductive organs. Routine gross and 

histopathological examination of the seminal vesicles, prostate, testes, ovaries, uterus, and mammary 

glands of mice and rats exposed to 35 ppm propylene glycol dinitrate for 1 year, 6 hours/day, 

5 days/week, and dogs exposed to 0.2 ppm for 14 months, 6 hours/day, 5 days/week, revealed no 

treatment-related effects (Air Force 1985a). Test atmospheres in this study were generated by 

volatilizing propylene glycol dinitrate from Otto Fuel II. 

The highest NOAEL values for reproductive effects in each species following chronic-duration 

inhalation exposure to propylene glycol dinitrate are recorded in Table 2- 1 and plotted in Figure 2- 1. 
OTTO FUEL II AND ITS COMPONENTS 37 

2. HEALTH EFFECTS 

2.2.1.6 Developmental Effects 

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

propylene glycol dinitrate, 2-nitrodiphenylamine, or dibutyl sebacate. However, extremely limited 

information regarding developmental effects in children of workers occupationally exposed to Otto 

Fuel II was available. 

A child with multiple birth defects was born to the wife of a worker at an incineration facility at 

which Otto Fuel II comprised approximately 10% of the waste processed (ATSDR 1990). The defects 

included club foot, imperforate anus, renal anomalies and persistence of the cloaca. Chromosomal 

studies on the child were normal. However, the birth defects cannot be definitively ascribed to Otto 

Fuel II exposure because other possible causes for the defects existed (i.e., exposure to other 

developmental toxicants) and the incidence of similar defects in a control population were not 

adequately characterized. 

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

Fuel II or its components. 

2.2.1.7 Genotoxic Effects 

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

Otto Fuel II or its components. 

Genotoxicity studies are discussed in Section 2.4. 

2.2.1.8 Cancer 

No studies were located regarding cancer in humans after inhalation exposure to Otto Fuel II or any of 

its individual components. 

No studies were located regarding cancer in animals after inhalation exposure to Otto Fuel II or two of 

its components, 2-nitrodiphenylamine and dibutyl sebacate. 
OTTO FUEL II AND ITS COMPONENTS 38 

2. HEALTH EFFECTS
 

Extremely limited information was located regarding cancer in animals after inhalation exposure to 

propylene glycol dinitrate. One osteoma and one osteosarcoma were observed in rats 1 year following 

exposure to 0.2 ppm of propylene glycol dinitrate for I year, 5 days/week, 6 hours/day; 

2 osteosarcomas were observed in rats I year following exposure at the 35ppm level for the same 

duration (Air Force 1985a). These tumors are rare and could be indicative of a tumorigenic potential 

of propylene glycol dinitrate. However, the study authors concluded that the lack of a dose response 

given the large differences in doses tested suggested that the tumors were not exposure related. Mice 

exposed to 35 ppm of propylene glycol dinitrate for 6 hours/day, 5 days/week, for 1 year, and then 

observed for 1 year postexposure, had an increased incidence of lymphoid hyperplasia (considered to 

be indicative of early lymphoma, a common lesion in older mice) (Air Force 1985a). However, the 

study authors also concluded that this lesion was incidental and not exposure related. Both of these 

studies are limited in that they were less than lifetime studies (18 months in the mouse and 2 years in 

the rat), the controls were not sham exposed, and a chronic ulcerative dermatitis was observed in the 

control mice, confounding the analysis of the results of the study. 

2.2.2 Oral Exposure 

With the exception of acute oral LD50 data, virtually all of the information on the effects of Otto Fuel 

II or its components after oral exposure comes from studies examining the oral toxicity of dibutyl 

sebacate. These studies show that dibutyl sebacate is a relatively nontoxic component of Otto Fuel II. 

The only toxicity observed with dibutyl sebacate is a slight depression of body weight of offspring 

from parental animals that had consumed large amounts of dibutyl sebacate prior to conception (Smith 

1953). 

2.2.2.1 Death 

No studies were located regarding death in humans after oral exposure to Otto Fuel II or its
 

components.
 

The only study that was located regarding death in animals after oral exposure to Otto Fuel II was an
 

LD50 determination in rats; however, very few experimental details were presented (Navy 1982b).
 

This study reported an LD50 value of 2,000 mg/kg.
 
OTTO FUEL II AND ITS COMPONENTS 39 

2. HEALTH EFFECTS
 

A number of studies have examined the acute oral toxicity of propylene glycol dinitrate in rats. Oral 

LD50 values ranging from 250 to 1,190 mg/kg have been determined (Andersen and Mehl 1979; Clark 

and Litchfield 1969; Jones et al. 1972). The reason for the wide range of values obtained is not clear 

but may have been due to differences in the strain, sex, age, or weight of the rats tested. Different rat 

strains were used in all three studies: Sprague Dawley (Andersen and Mehl 1979) Alderley Park 

strain (Clark and Litchfield 1969), and Long Evans (Jones et al. 1972). Also, Andersen and Mehl 

( 1979) and Jones et al. (1972) used only male rats; whereas, Clark and Litchfield (1 969) used only 

females. All three studies described similar symptoms before death including prostration and anoxia. 

In addition, mild convulsions were observed in the rats prior to death in the study by Jones et al. 

(1972). 

Dibutyl sebacate has very low toxicity and only very large oral doses were observed to result in death. 

All rats given a single oral dose of 32,000 mg/kg died; whereas, all rats given 16,000 mg/kg survived 

(Smith 1953). No gross or histopathologic changes indicating the cause of death were observed in the 

rats at necropsy. However, extremely large volumes of test material were administered (approximately 

2.4 mL at the highest dose tested) to 60-75gram rats; thus, it is possible that death may have resulted 

from aspiration of the test material. This is supported by the observation of hemorrhaging and edema 

in the lungs of the rats and mice receiving doses greater than or equal to 10-1 5 g/kg in the oral LD50 

study by Komarova (1976, 1979). Oral LD50 values for dibutyl sebacate in rats and mice in this study 

were reported to be 17,200 mg/kg/day and 18,100 mg/kg/day, respectively (Komarova 1976, 1979). 

The only information located regarding death following ingestion of 2-nitrodiphenylamine indicated 

that the oral toxicity of 2-nitrodiphenylamine was also very low. The oral LD50 value for rats was 

6,150 mg/kg. (This information was obtained from a Material Safety Data Sheet on 

2-nitrodiphenylamine [American Cyanamid 19821). Because the actual study was unavailable for 

review, this value could not be verified.) 

All reliable LOAEL values for death in rats following acute-duration exposure are recorded for 

propylene glycol dinitrate in Table 2-2 and for dibutyl sebacate in Table 2-3 and plotted for propylene 

glycol dinitrate in Figure 2-2 and for dibutyl sebacate in Figure 2-3. 






OTTO FUEL II AND ITS COMPONENTS 46 

2. HEALTH EFFECTS 

2.2.2.2 Systemic Effects 

No studies were located regarding musculoskeletal, dermal, or ocular effects in humans or animals 

after oral exposure to Otto Fuel II or its components. 

The highest NOAEL values and all reliable LOAEL values for each study for each end point for 

dibutyl sebacate in rats are recorded in Table 2-3 and plotted in Figure 2-3. 

Respiratory Effects. No studies were located regarding respiratory effects in humans after oral 

exposure to Otto Fuel II or its components. 

No studies were located regarding respiratory effects in animals after oral exposure to Otto Fuel II or 

two of its components, propylene glycol dinitrate and 2-nitrodiphenylamine. However, necropsy of 

rats and mice that died as a result of receiving a single oral dose of dibutyl sebacate greater than or 

equal to 10,000 and 15,000 mg/kg, respectively, revealed hemorrhaging and edema of the lungs 

(Komarova 1976, 1979). No information regarding the number of animals per dose with lung 

pathology or the dose relationship of this response was presented. It is possible that the hemorrhaging 

and edema in the lungs was the result of aspiration of the gastric contents, considering the relatively 

large gavage volumes used. In contrast, routine gross and histopathological examination of rats 

consuming 3,125 mg/kg/day of dibutyl sebacate for 2 years demonstrated no treatment-related gross or 

histopathological alterations in the lungs (Smith 1953). 

Cardiovascular Effects. No studies were located regarding cardiovascular effects in humans after 

oral exposure to Otto Fuel II or its components. 

No studies were located regarding cardiovascular effects in animals after oral exposure to Otto Fuel II 

or two of its components, propylene glycol dinitrate and 2-nitrodiphenylamine. However, 

cardiovascular end points were reported in animals following oral exposure to dibutyl sebacate in two 

studies. 

Hypervolemia of the heart muscle was observed at necropsy of rats and mice that died following 

administration of a single oral dose of dibutyl sebacate greater than or equal to 10,000 and 

15,000 mg/kg, respectively (Komarova 1976, 1979). Insufficient information regarding the incidence 
OTTO FUEL II AND ITS COMPONENTS 47 

2. HEALTH EFFECTS
 

of this effect or the number of animals exposed limits this study. Also, it is unclear whether this 

represents a direct toxic effect of the dibutyl sebacate or is a result of the administration of a large 

volume of test material. Routine gross and histopathological examination of rats consuming 

3, 125 mg/kg/day of dibutyl sebacate for 2 years showed no treatment-related gross or histopathological 

changes in the heart (Smith 1953). 

Gastrointestinal Effects. No studies were located regarding gastrointestinal effects in humans 

after oral exposure to Otto Fuel II or its components. 

No studies were located regarding gastrointestinal effects in animals after oral exposure to Otto Fuel II 

or two of its components, propylene glycol dinitrate and 2-nitrodiphenylamine. However, 

gastrointestinal end points were reported in animals following oral exposure to dibutyl sebacate in two 

studies. 

Hypervolemia of the walls of the small intestines and paresis of the stomach were observed in rats and. 

mice that died following oral administration of single doses of dibutyl sebacate greater than or equal to 

10,000 and 15,000 mg/kg, respectively (Komarova 1976, 1979). It is unclear whether these effects 

represented direct toxic effects of the dibutyl sebacate or were the result of administration of a large 

oral volume of test material. Routine gross and histopathological examination of rats consuming 

3,125 mg/kg/day of dibutyl sebacate for 2 years revealed no treatment-related gross or 

histopathological changes in the stomach or small intestine (Smith 1953). 

Hematological Effects. No studies were located regarding hematologicat effects in humans after 

oral exposure to Otto Fuel II or its components. 

No studies were located regarding hematological effects in animals after oral exposure to Otto Fuel II 

or its component, propylene glycol dinitrate. However, limited information was located regarding the 

hematological toxicity of 2-nitrodiphenylamine and dibutyl sebacate. 

An Army review indicated that oral administration of 3,070 mg/kg of 2-nitrodiphenylamine to rats 

resulted in elevation of methemoglobin levels to 9.45% (Army 1979). (This information was obtained 

by the U.S. Army through personal communication with American Cyanamid. Because the actual 

study was unavailable for review, this information could not be verified.) 
OTTO FUEL II AND ITS COMPONENTS 48 

2. HEALTH EFFECTS 

Routine hematology performed at 6, 12, 18, and 24 months revealed no effects of consumption of up 

to 3,125 mg/kg/day of dibutyl sebacate on hemoglobin, total erythrocytes, or total or differential 

leukocyte counts in rats (Smith 1953). Differential counts taken on bone marrow smears at the time of 

final sacrifice also revealed no effect on cellular distribution or the myeloid-erythroid ratio. 

Hepatic Effects. No studies were located regarding hepatic effects in humans after oral exposure 

to Otto Fuel II or its components. 

No studies were located regarding hepatic effects in animals after oral exposure to Otto Fuel II or two 

of its components, propylene glycol dinitrate and 2-nitrodiphenylamine. However, routine gross and 

histopathological examination of rats consuming 3,125 mg/kg/day of dibutyl sebacate for 2 years 

revealed no treatment-related gross or histopathological changes in the liver (Smith 1953). 

Renal Effects. No studies were located regarding renal effects in humans after oral exposure to 

Otto Fuel II or its components. 

No studies were located regarding renal effects in animals after oral exposure to Otto Fuel II or two of 

its components, propylene glycol dinitrate and 2-nitrodiphenylamine. However, in two studies, renal 

end points were evaluated in animals following oral exposure to dibutyl sebacate. 

Hypervolemia of the kidneys was observed at necropsy of rats and mice that died as a result of oral 

administration of a single dose of dibutyl sebacate greater than or equal to 10,000 and 15,000 mg/kg, 

respectively (Komarova 1976, 1979). However, insufficient information regarding the number of 

animals tested and the incidence of this observation limits the interpretation of this report. In addition, 

it is unclear whether this effect is a direct toxic effect of the dibutyl sebacate or the result of the 

administration of a large volume of test material. Routine gross and histopathological examination of 

rats consuming 3,125 mg/kg/day of dibutyl sebacate for 2 years revealed no treatment-related gross or 

histopathological changes in the kidneys (Smith 1953). 

Endocrine Effects. Information regarding endocrine effects after oral exposure to Otto Fuel II or 

its components was limited to an early study with dibutyl sebacate in rats. In that study (Smith 1953), 

rats fed a diet that provided up to 3,125 mg dibutyl sebacate/kg/day for up to 2 years showed no gross 
OTTO FUEL II AND ITS COMPONENTS 49 

2. HEALTH EFFECTS 

or histopathological changes in the thyroid and adrenal glands. No further endocrinological end points 

were assessed. 

2.2.2.3 Immunological and Lymphoreticular Effects 

No studies were located regarding immunological effects in humans or animals after oral exposure to 

Otto Fuel II or its components propylene glycol dinitrate and 2-nitrophenylamine. However, no gross 

alterations were observed in the spleens of rats fed a diet that provided 625 mg dibutyl sebacate/kg/day 

for 1 year or 3,125 mg/kg/day for 2 years (Smith 1953). This information is recorded in Table 2-3 

and plotted in Figure 2-3. 

2.2.2.4 Neurological Effects 

No studies were located regarding neurological effects in humans after oral exposure to Otto Fuel II or 

its components. 

No studies were located regarding neurological effects in animals after oral exposure to Otto Fuel II or 

its component, 2-nitrodiphenylamine. However, information regarding the effects of propylene glycol 

dinitrate and dibutyl sebacate on neurological parameters was available. 

A reduced response to external stimuli, prostration, and mild convulsions were observed in rats given 

single oral doses of propylene glycol dinitrate (Jones et al. 1972). At concentrations ranging from 

1,100 to 3,320 mg/kg/day, the effects were observed within 15 minutes, and at lower doses 

(76-760 mg/kg/day), the symptoms were not as severe and were delayed in onset. The lowest doses at 

which specific effects were observed in this study were not specified. 

Hypervolemia of the “brain substance” was observed in rats and mice that died following 

administration of a single oral dose of dibutyl sebacate greater than or equal to 10,000 and 

15,000 mg/kg, respectively (Komarova 1976, 1979). However, evaluation of this finding is limited 

because insufficient information regarding the number of animals tested or the dose-related incidence 

was provided. In addition, it is unclear whether this effect is a direct toxic effect of the dibutyl 

sebacate or is related to the volume of the test material that was administered. No gross pathological 
OTTO FUEL II AND ITS COMPONENTS 50 

2. HEALTH EFFECTS 

changes were observed in the brains of rats consuming 625 mg dibutyl sebacate/kg/day for I year or 

3,125 mg/kg/day for 2 years (Smith 19.53). 

The highest NOAEL values for neurological effects in rats following chronic-duration exposure to 

dibutyl sebacate are recorded in Table 2-3 and plotted in Figure 2-3. 

2.2.2.5 Reproductive Effects 

No studies were located regarding reproductive effects in humans after oral exposure to Otto Fuel II or 

its components. 

No studies were located regarding reproductive effects in animals after oral exposure to propylene 

glycol dinitrate or 2-nitrodiphenylamine. 

The only study located regarding possible reproductive effects of Otto Fuel II was a dominant lethal 

study in mice which demonstrated that exposure of males to 200 mg/kg/day of Otto Fuel II for 5 days 

prior to mating had no effect on fertility, the total number of implants per pregnant female, or the 

number of dead implants per pregnant female (Navy 1982b). However, this study was limited in that 

the fertility was low overall in both control and treated animals. 

Consumption of 3,125 mg/kg/day of dibutyl sebacate in the diet by parental animals for 10 weeks 

prior to mating caused no adverse effects on fertility, litter size, or litter survival (Smith 1953). 

The highest NOAEL for reproductive effects in rats after intermediate-duration oral exposure to dibutyl 

sebacate is recorded in Table 2-3 and plotted in Figure 2-3. 

2.2.2.6 Developmental Effects 

No studies were located regarding developmental effects in humans after oral exposure to Otto Fuel II 

or its components. 

No studies were located regarding developmental effects in animals after oral exposure to Otto Fuel II 

or two of its components, propylene glycol dinitrate and 2-nitrodiphenylamine. 
OTTO FUEL II AND ITS COMPONENTS 51 

2. HEALTH EFFECTS 

Consumption of 3,125 mg/kg/day of dibutyl sebacate in the diet by male and female rats for 10 weeks 

prior to mating resulted in a decreased weight gain in litters during the preweaning period (Smith 

1953). It is unclear whether the reduced growth was caused by contact with test material in utero or 

during lactation. Additional exposure of a subset of the pups to the parental diet for 21 days 

postweaning resulted in continued retarded growth. No gross pathological changes were observed at 

necropsy of the litters following sacrifice at the end of a 21-day postweaning period. 

The NOAEL value for developmental effects in rats after intermediate-duration exposure to dibutyl 

sebacate is recorded in Table 2-3 and plotted in Figure 2-3. 

2.2.2.7 Genotoxic Effects 

No studies were located regarding genotoxic effects in humans after oral exposure to Otto Fuel II or 

its components. 

No studies were located regarding genotoxic effects in animals after oral exposure to propylene glycol 

dinitrate, 2-nitrodiphenylamine, or dibutyl sebacate. 

Otto Fuel II was evaluated for the potential to induce chromosome aberrations in mouse bone marrow 

cells following the acute oral administration of 20, 62, or 200 mg/kg/day (Navy 1982b). Although the 

results from the acute study suggested a clastogenic response (i.e., slight but dose-related increases in 

chromosome damage and the presence of rare complex aberrations at two doses), no definite 

conclusions could be drawn. In that study (Navy 1982b), treatment with Otto Fuel II did not induce 

any signs of overt toxicity. Negative results were reported for the mouse dominant lethal assay 

conducted with comparable acute oral doses of Otto Fuel II (Navy 1982b). (The.assay detects mainly 

chromosome aberrations but may also detect ploidy changes and chromosome nondisjunctions.) The 

relevance, if any, of the reduced fertility indices in the three treatment groups at the majority of mating 

intervals (weekly matings for the 7-week test period) could not be determined because similar reduced 

fertility indices were seen in the historic and concurrent negative controls. Also of concern was the 

low number of pregnant females (<20/treatment group/mating week) evaluated for critical dominant 

lethal parameters. Although the dominant lethal indices (i.e., dead implants/total implants) for the 

majority of treatment groups and mating weeks were within the historical spontaneous range of the 

reporting laboratory and also within published ranges (Green et al. 1985) the small sample size of 
OTTO FUEL II AND ITS COMPONENTS 52 

2. HEALTH EFFECTS
 

pregnant females compromised the overall results. It was, nonetheless, concluded that there was no 

compelling evidence from this study that Otto Fuel II was clastogenic in male mouse germinal cells. 

Other genotoxicity studies are discussed in Section 2.4. 

2.2.2.8 Cancer 

No studies were located regarding cancer in humans after oral exposure to Otto Fuel II or its 

components. 

No studies were located regarding cancer in animals after oral exposure to Otto Fuel II or its 

components, propylene glycol dinitrate and 2-nitrodiphenylamine. Limited information was, however, 

available regarding the tumorigenic potential of dibutyl sebacate in animals after oral exposure. 

Consumption of up to 3,125 mg/kg/day dibutyl sebacate by rats for 2 years had no effect on tumor 

incidence (Smith 1953). However, interpretation of this study is limited by the relatively small 

number of rats tested (20 males and 20 females per dose). 

2.2.3 Dermal Exposure 

As indicated in the section on inhalation exposure, it is often difficult to clearly separate dermal from 

inhalation exposures in many occupational studies. Thus, many of the findings from occupational 

studies described in Section 2.2.1 regarding inhalation exposure are repeated here. 

2.2.3.1 Death 

No studies were located regarding death in humans after dermal exposure to Otto Fuel II or its 

components. 

Application of 4,000 mg/kg/day of Otto Fuel II to the skin of pregnant rats during days 6-15 of 

gestation resulted in the deaths of 25 out of 47 rats at this dose (Cooper et al. 1993). No deaths were 

reported among pregnant rats at doses as great as 2,000 mg/kg/day or in pregnant rabbits at doses as 

great as 1,000 mg/kg/day (applied during days 6-18 of gestation) (Cooper et al. 1993). 
OTTO FUEL II AND ITS COMPONENTS 53 

2. HEALTH EFFECTS
 

Application of propylene glycol dinitrate to the skin of rabbits for 20 days for 2 hours/day resulted in 

death in 1 of 5 rabbits after the sixth application of 2,000 mg/kg and death in 13 of I4 rabbits after 

the fifth application of 4,000 mg/kg (Jones et al. 1972). Similarly, 6 of 1 I rabbits died as the result of 

daily application of 3,488 mg/kg for 3 weeks (Andersen and Mehl 1979). 

No deaths were reported to result from application of an unspecified amount of 100% dibutyl sebacate 

to the skin of rabbits for 48 hours (Mallette and Von Haam 1952b). This study is limited by the 

absence of details regarding the sex of the rabbits and dosage of dibutyl sebacate used. 

Application of 2-nitrodiphenylamine to the skin of rabbits resulted in a 24-hour dermal LD50 value of 

>l0,000 mg/kg (American Cyanamid 1982). (This information was obtained from a Material Safety 

Data Sheet on 2-nitrodiphenylamine. Because the actual study was unavailable for review, this value 

could not be verified.) 

All reliable LOAEL values for death in rats following acute-duration dermal exposure to Otto Fuel II 

are recorded in Table 2-4 and all reliable LOAEL values for death in rabbits after intermediateduration 

dermal exposure to propylene glycol dinitrate are recorded in Table 2-5: 

2.2.3.2 Systemic Effects 

No studies were located regarding gastrointestinal effects in humans or animals after dermal exposure 

to Otto Fuel II or any of its components. 

The highest NOAEL value and all reliable LOAEL values for each end point in rabbits after 

intermediate-duration dermal exposure to propylene glycol dinitrate are recorded in Table 2-4. 

Respiratory Effects. No studies were located regarding respiratory effects in humans after dermal 

exposure to propylene glycol dinitrate, 2nitrodiphenylamine, or dibutyl sebacate. However, 

respiratory effects associated with Otto Fuel II exposure have been reported. 

Approximately 6% of a group of 87 torpedo maintenance workers with 1-132 months (average 

47 months) of occupational exposure to Otto Fuel II reported experiencing dyspnea occasionally 

during past exposures (Horvath et al. 1981). It is possible that these workers may have been exposed 



OTTO FUEL II AND ITS COMPONENTS 57 

2. HEALTH EFFECTS
 

dermally as well as by inhalation (see Section 2.2. I .2) to Otto Fuel II during the maintenance 

procedures. It is unknown whether the incidence of the dyspnea was increased relative to controls or 

whether other chemical exposures may have contributed to the dyspnea. 

Nasal congestion was reported by approximately 31% of the workers in the study by Horvath et al. 

(1981). However, this symptom is most likely due to a direct vasodilatory effect of the propylene 

glycol dinitrate found in Otto Fuel II on the blood vessels of the nasal mucosa and not an effect on 

respiratory function as such. Therefore, nasal congestion is discussed below as a symptom of a 

cardiovascular response. 

No studies were located regarding respiratory effects in animals after dermal exposure to Otto Fuel II 

or two of its components, 2-nitrodiphenylamine and dibutyl sebacate. However, application of 

2,000 mg/kg/day of propylene glycol dinitrate to the skin of rabbits for 2 hours/day for 20 days 

resulted in rapid and shallow breathing (Jones et al. 1972). This effect was apparently not associated 

with pulmonary damage because histopathologic examination of the lungs of the animals at the 

termination of exposure found no pathologic alterations, but was probably related to development of 

methemoglobinemia. 

Cardiovascular Effects. No studies were located regarding cardiovascular effects in humans after 

dermal exposure to propylene glycol dinitrate, 2-nitrodiphenylamine, or dibutyl sebacate. However, 

cardiovascular effects have been associated with exposure to Otto Fuel II. 

Symptoms identified with nitrate-induced vasodilation or compensatory vasoconstriction have been 

observed in studies examining human exposure to Otto Fuel II. For example, symptoms that were 

experienced either frequently or occasionally by 87 torpedo maintenance workers with 1-132 months 

(average of 47 months) of exposure to Otto Fuel II included headache (65%) and nasal congestion 

(31%) (Horvath et al. 1981). However, it was not reported whether the incidence of these symptoms 

was greater than in the controls. Workers at an incinerator at which Otto Fuel II was burned reported 

that they were able to identify exposures to Otto Fuel II by its characteristic vasodilatory headache 

(ATSDR 1990). Labile blood pressures were also recorded in the incinerator workers. However, this 

effect cannot be directly attributed to Otto Fuel II exposure because only 10% of the waste handled at 

the facility was Otto Fuel II. 
OTTO FUEL II AND ITS COMPONENTS 58 

2. HEALTH EFFECTS
 

Ten percent of the torpedo maintenance workers also reported experiencing palpitations and 4% 

reported experiencing chest pain. Although it was not stated whether the incidence of these symptoms 

was greater than in controls, a study of 1,352 Naval torpedoman’s mates with potential exposure to 

Otto Fuel II demonstrated a significantly greater incidence of hospitalizations for myocardial 

infarctions or angina pectoris than 14,336 unexposed torpedoman’s mates or 29,129, unexposed fire 

control technicians (Forman et al. 1987). Chest pain and tightness were also reported by several of the 

incinerator workers, and one worker was diagnosed with nitrate withdrawal angina (ATSDR 1990). 

However, because of the large number of wastes handled at the facility, other possible causative agents 

for these cardiac symptoms cannot be eliminated. 

No studies were located regarding cardiovascular effects in animals after dermal exposure to Otto 

Fuel II or two of its components, 2-nitrodiphenylamine and dibutyl sebacate. However, a single 

application of 50 mg/kg of propylene glycol dinitrate in corn oil to the skin of rats resulted in a 

7-mm Hg fall in blood pressure (Clark and Litchfield 1969). It is unclear whether the decrease in 

blood pressure is statistically significant. Similar drops in blood pressure were reported in a recent 

study in which anesthetized rats were applied a wide range of doses (5-450 mg/kg) of propylene 

glycol dinitrate (Godin et al. 1993). It must be mentioned, however, that the magnitude of the fall in 

blood pressure was not dose-related. Exposure of rabbits to propylene glycol dinitrate for 2 hours/day 

for 20 days resulted in the appearance of myocardial degeneration in some rabbits (Jones et al. 1972). 

It was not specified at which dose (1,000, 2,000, or 4,000 mgkg) this effect was observed, but it is 

assumed that it was present at 4,000 mg/kg/day. 

Hematological Effects. No studies were located regarding hematoiogical effects in humans after 

dermal exposure to Otto Fuel II or its components. 

No studies were located regarding hematological effects in animals after dermal exposure to 

2-nitrodiphenylamine and dibutyl sebacate. However, hematotoxicity was observed in animals 

following derrnal exposure to Otto Fuel II or propylene glycol dinitrate. 

A brownish discoloration of the blood was observed at necropsy in pregnant rats that died following 

application of 4,000 mg/kg/day of Otto Fuel II to the skin during gestation days 6-15 (Cooper et al. 

1993). This discoloration was attributed by the authors to be due to methemoglobinemia because a 

blood sample taken from one of the moribund animals had a methemoglobin level of 56.7%. 
OTTO FUEL II AND ITS COMPONENTS 59 

2. HEALTH EFFECTS
 

Application of 1,000 mg/kg/day propylene glycol dinitrate to the skin of rabbits for 2 hours/day, for 

20 days, resulted in a transient decrease in hemoglobin (Jones et al. 1972). A transient decrease in 

hematocrit was observed in rabbits receiving 2,000 mg/kg/day in this study. At 2,000 mg/kg, rabbits 

appeared cyanotic and internal organs appeared dark blue-gray in color. At the highest concentration 

tested, 4,000 mg/kg/day, methemoglobin levels were elevated to 34.5%. 

Musculoskeletal Effects. No studies were located regarding musculoskeletal effects in humans 

after dermal exposure to propylene glycol dinitrate, 2-nitrodiphenylamine, and dibutyl sebacate. 

“Seronegative arthritis” was diagnosed in several workers from an incinerator at which 10% of the 

material burned was Otto Fuel II (ATSDR 1990). However, because of the large number of other 

wastes processed at the facility, the arthritis cannot be ascribed to Otto Fuel II exposure with any 

certainty. 

No studies were located regarding musculoskeletal effects in animals after dermal exposure to Otto 

Fuel II or its components. 

Hepatic Effects. No studies were located regarding hepatic effects in humans after dermal 

exposure to propylene glycol dinitrate, 2-nitrodiphenylamine, and dibutyl sebacate. However, transient 

elevations in unspecified parameters assessing liver function were noted in several incinerator workers 

at a facility at which approximately 10% of the waste handled was Otto Fuel II (ATSDR 1990). 

However, because the other wastes incinerated included a number of solvents, this effect cannot be 

definitively attributed to Otto Fuel II. 

No studies were located regarding hepatic effects in animals after dermal exposure to Otto Fuel II and 

its components, 2-nitrodiphenylamine and dibutyl sebacate. However, hepatic effects were noted in 

studies in which animals received dermal applications of propylene glycol dinitrate. 

Degenerative changes were observed in the livers of rabbits that died after six applications of 

4,000 mg propylene glycol dinitrateikg (Jones et al. 1972). The investigators also indicated that liver 

oxygen uptake rates and serum proteins, alkaline phosphatase, glutamate-oxaloacetate transaminase, 

glutamate-pyruvate transaminase, isocitrate dehydrogenase, and lactate dehydrogenase were not 

affected by propylene glycol dinitrate application, but the dose levels referred to (1,000, 2,000, or 

4,000 mg propylene glycol dinitrate/kg) were unclear. 
OTTO FUEL II AND ITS COMPONENTS 60 

2. HEALTH EFFECTS 

Renal Effects. No studies were located regarding renal effects in humans after dermal exposure to 

Otto Fuel II or its components. 

No studies were located regarding renal effects in animals after dermal exposure to Otto Fuel II or twc 

of its components, 2-nitrodiphenylamine and dibutyl sebacate. However, vacuolar changes were 

reported in the epithelial cells of the proximal convoluted tubules of the kidneys in a study in which 

1,000, 2,000, or 4,000 mg/kg propylene glycol dinitrate was applied to the skin of rabbits for 

2 hours/day for 20 days (Jones et al. 1972). However, the doses at which this effect was observed 

were not reported. 

Dermal Effects. No studies were located regarding dermal effects in humans after dermal exposure 

to propylene glycol dinitrate or 2-nitrodiphenylamine. 

Eczema, dermatitis with macropapular rashes, and sweating with no apparent cause were also reported 

among incinerator workers at a facility at which Otto Fuel II made up approximately 10% of the waste 

material processed (ATSDR 1990). However, other materials processed at the incinerator could have 

been responsible for these effects. 

Application of undiluted dibutyl sebacate (dosage not reported) to abraded skin of volunteers for an 

unspecified period of time was not irritating (Askarova and Muryseva 1975). Application of dibutyl 

sebacate (dosage not reported) to the skin of volunteers for 48 hours also resulted in no irritation 

(Mallette and Von Haam 1952b). No sensitization was observed when the subjects in the latter study 

were reexposed 2 weeks later. 

Animal studies were located regarding dermal effects in animals after dermal exposure to Otto Fuel II 

and each of its individual components. 

Moderate erythema was observed at the application site of pregnant female rats that received a daily 

dose of 4,000 mg/kg/day of Otto Fuel II for 10 days (Cooper et al. 1993). In addition, marked 

erythema was observed at the application site of pregnant female rabbits that received a daily dose of 

1,000 mg/kg/day of Otto Fuel II for 13 days (Cooper et al. 1993). 
OTTO FUEL II AND ITS COMPONENTS 61 

2. HEALTH EFFECTS 

No skin irritation was observed 24 or 72 hours after a single application of an unspecified amount of 

propylene glycol dinitrate to the skin of rabbits (Jones et al. 1972). Repeated application of 

1,000 mg/kg/day to the skin of rabbits for 2 hours/day for 20 days resulted in slight erythema and 

roughening of the skin that cleared up 5 days after the final application (Jones et al. 1972). At 

2,000 mg/kg/day, the skin appeared slightly wrinkled and scaly at the end of the exposure period. 

Slight irritation was observed following application of an unspecified dose of dibutyl sebacate to the 

skin of rabbits and guinea pigs (Komarova 1976, 1979). However, no experimental details were 

provided in this report. No skin irritation was observed in rabbits following application of an 

unspecified concentration of dibutyl sebacate to the skin for 48 hours (Mallette and Von Haam 1952b). 

Reexposure 2 weeks later resulted in no sensitization. 

Also, no irritation was reported following application of an unspecified amount of 

2-nitrodiphenylamine to the skin of rabbits (American Cyanamid 1982). (This information was 

obtained from a Material Safety Data Sheet on 2-nitrodiphenylamine. Because the actual study was 

unavailable for review, this lack of irritation could not be verified.) 

Ocular Effects. No studies were located regarding ocular effects in humans after dermal exposure 

to 2-nitrodiphenylamine or dibutyl sebacate. 

Occupational exposure to Otto Fuel II resulted in approximately 26% of the 87 workers interviewed 

complaining of eye irritation as an occasional or frequent exposure-related effect (Horvath et al. 1981). 

However, the incidence of this effect relative to the control population was not reported. Eye irritation 

was also a common complaint among incinerator workers at a facility at which Otto Fuel II made up 

approximately 10% of the waste material processed (ATSDR 1990). However, other materials 

processed at the incinerator could have been responsible for these effects. 

One out of 12 volunteers exposed to 0.2 ppm propylene glycol dinitrate for 8 hours experienced eye 

irritation, and 8 out of 8 had frank eye irritation after 40 minutes of exposure to 1.5 ppm propylene 

glycol dinitrate (Stewart et al. 1974). In the same study, no eye irritation was reported in nine subjects 

exposed to 0.2 ppm propylene glycol dinitrate 8 hours/day for 5 days (Stewart et al. 1974). 
OTTO FUEL II AND ITS COMPONENTS 62 

2. HEALTH EFFECTS
 

Data in animals are limited to propylene glycol dinitrate and 2-nitrodiphenylamine. Conjunctival 

redness was observed 5 minutes after an unspecified dose of propylene glycol dinitrate was instilled 

into the eyes of rabbits (Jones et al. 1972). The irritation disappeared within 24 hours. No effects on 

the cornea or iris were observed. 

Also, no irritation was reported following application of an unspecified amount of 

2-nitrodiphenylamine to the eyes of rabbits (American Cyanamid 1982). (This information was 

obtained from a Material Safety Data Sheet on 2-nitrodiphenylamine. Because the actual study as 

unavailable for review, this value could not be verified.) 

Body Weight Effects. The only information regarding body weight effects after dermal exposure 

to Otto Fuel II or its components is that provided by Cooper et al. (1993) who reported significant 

decreases in body weight gain in both rats and rabbits after repeated applications of Otto Fuel II to the 

skin during pregnancy (400 mg/kg/day to rats, 100 mg/kg/day to rabbits). However, food consumption 

data were not provided.) 

2.2.3.3 Immunological and Lymphoreticular Effects 

No studies were located regarding immunological effects in humans after dermal exposure to 

propylene glycol dinitrate and 2-nitrodiphenylamine. However, sensitization was tested following 

dermal exposure to dibutyl sebacate and immunological effects (possibly related to Otto Fuel II 

exposure) were reported. 

No skin sensitization was observed in volunteers exposed to an unspecified amount of 100% dibutyl 

sebacate 2 weeks following an initial 2-day dermal exposure (Mallette and Von Haam 1952b). 

However, in workers exposed to lubricants containing dibutyl sebacate, a 3.3% rate of sensitization 

was observed when nonirritating concentrations of dibutyl sebacate were applied to their skin 

(Askarova and Muryseva 1975). Nonirritating concentrations were determined in volunteers with no 

known exposure to the lubricants or their ingredients. This study is limited, however, in that a control 

group was not used in the sensitization portion of the study. 

A child of a worker at an incineration facility at which Otto Fuel II was processed developed asthma 

(ATSDR 1990). The asthma was linked to materials handled at the incinerator because when the 
OTTO FUEL II AND ITS COMPONENTS 63 

2. HEALTH EFFECTS 

father of the child stopped bringing his work clothing home, the child’s condition improved. 

However, Otto Fuel II comprised only approximately 10% of the wastes handled at the facility; thus, 

other materials may have triggered the reaction in the child. The possibility also exists that the 

asthma-like response may have been caused by tetryl particles activating nerve receptors which 

triggered vagal reflexes inducing bronchoconstriction. 

No studies were located regarding immunological effects in animals after dermal exposure to Otto 

Fuel II or its component, 2-nitrodiphenylamine. However, extremely limited information was located 

regarding immunological effects of propylene glycol dinitrate and dibutyl sebacate in animals after 

dermal exposure. No studies that directly examined immunological function were located. However, 

total and differential leukocyte counts and routine gross and histopathological examination of the 

spleen were normal in rabbits after application of doses as high as 4,000 mg/kg/day of propylene 

glycol dinitrate to the skin for 2 hours/day for 20 days (Jones et al. 1972). 

No skin sensitization was observed in rabbits reexposed to an unspecified dose of 100% dibutyl. 

sebacate 2 weeks after a 2-day dermal application (Mallette and Von Haam 1952b). 

2.2.3.4 Neurological Effects 

No studies were located regarding neurological effects in humans after dermal exposure to propylene 

glycol dinitrate, 2-nitrodiphenylamine, and dibutyl sebacate. 

The only reliable information regarding neurological effects in humans after dermal exposure to Otto 

Fuel II was found in a study examining the effects of exposure to Otto Fuel II during torpedo 

maintenance procedures on tests of balance and oculomotor performance (Horvath et al. 1981). 

Twenty-nine workers with an unspecified number of months of previous occupational exposure to Otto 

Fuel II were tested both before and after a typical torpedo maintenance procedure. The duration of the 

procedure was between 30 and 45 minutes, and both inhalation and dermal exposures were likely. The 

inhalation exposures ranged from 0 to 0.22 ppm, but the amount of dermal exposure was not 

monitored. No significant difference in the tests evaluating balance and coordination were observed 

when comparing pre- and postexposure results. However, a significant decrease in saccade velocity 

and increase in saccade delay were observed. Although these effects were reported by the authors to 

be functionally insignificant, they were proposed as evidence of preclinical neurological effects of Otto 
OTTO FUEL II AND ITS COMPONENTS 64 

2. HEALTH EFFECTS
 

Fuel II exposure. Eighty-seven torpedo maintenance workers were also questioned regarding effects 

experienced during past exposures. Dizziness was reported by 13% of the workers and loss of balance 

was reported by 1% of the workers; however, the incidence of these effects was not compared to that 

in an unexposed control group. 

Workers at an incinerator where Otto Fuel II comprised approximately 10% of the waste materials 

processed, were diagnosed with a number of neurological disorders (ATSDR 1990). These included 

mood disorders, cerebellar dysfunction (ataxia, tremor, nystagmus), cognitive disorders, memory loss, 

and possible vestibular dysfunction. Magnetic resonance imaging showed that two of the four workers, 

interviewed in the report had cerebellar and cortical atrophy. However, the effects observed cannot be 

attributed to Otto Fuel II with certainty because a large number of solvents and other wastes were also 

handled at the incinerator. It is also unclear from the report whether the individuals that were 

examined represented a substantial percentage of the workers that were exposed to Otto Fuel II. 

Headaches have frequently been reported by workers occupationally exposed to Otto Fuel II (Horvath 

et al. 1981). However, the headaches are most likely associated with meningeal blood vessel dilation 

(Nickerson 1975) (see also Cardiovascular Effects in Section 2.2.3.2). 

No studies were located regarding neurological effects in animals after dermal exposure to Otto Fuel II 

or its components, 2-nitrodiphenylamine or dibutyl sebacate. Extremely limited information was 

obtained regarding possible neurological effects resulting from dermal application of propylene glycol 

dinitrate. Weakness was observed in rabbits after the third 2-hour/day application of 2,000 mg/kg/day 

of propylene glycol dinitrate to the skin (Jones et al. 1972). The animals had recovered by the 20th 

daily application. However, it is not known whether the weakness that was observed was neurological 

in origin. The gross and histopathological examination of sections of brain and spinal cord showed no 

adverse structural effects of propylene glycol dinitrate on these tissues. 

2.2.3.5 Reproductive Effects 

No studies were located regarding reproductive effects in humans or animals after dermal exposure to 

Otto Fuel II or any of its individual components. 
OTTO FUEL II AND ITS COMPONENTS 65 

2. HEALTH EFFECTS 

2.2.3.6 Developmental Effects 

No studies were located regarding developmental effects in humans after dermal exposure to propylene 

glycol dinitrate, 2-nitrodiphenylamine, and dibutyl sebacate. However, a child with multiple birth 

defects was born to the wife of a worker at an incinerator where Otto Fuel II comprised approximately 

10% of the waste processed (ATSDR 1990). The defects included club foot, imperforate anus, renal 

anomalies, and persistence of the cloaca. Chromosomal studies on the child were normal. The birth 

defects cannot be definitively ascribed to exposure to Otto Fuel II because other possible causes for 

the defects exist (i.e., exposure to other developmental toxicants) and the incidence of similar defects 

in a control population were not adequately characterized. 

No studies were located regarding developmental effects in animals after dermal exposure to propylene 

glycol dinitrate, 2-nitrodiphenylamine, and dibutyl sebacate. 

Rat pups from dams receiving daily dermal applications of 2,000 mg/kg/day of Otto Fuel II during 

gestation days 6-15 had decreased body weight when compared to pups from control rats (Cooper et 

al. 1993). At 4,000 mg/kg/day, an increase in the number of resorptions, decrease in the number of 

viable pups, and decreases in pup weight were observed. Decreased maternal body weights were 

observed among dams at 2,000 and 4,000 mg/kg/day indicating maternal toxicity at these doses. 

Discoloration of the blood, likely due to methemoglobinemia, was observed in dams at the 

4,000 mg/kg/day dose. No developmental toxicity was observed in pups from dams at doses where no 

maternal toxicity was evident. No increase in visceral or skeletal abnormalities was observed at any 

dose. No developmental toxicity was observed at doses as high as 1,000 mg/kg/day in rabbits that 

received daily dermal applications of Otto Fuel II during gestation days 6-18 (Cooper et al. 1993). 

2.2.3.7 Genotoxic Effects 

No studies were located regarding genotoxic effects in humans or animals after dermal exposure to
 

Otto Fuel II or its components.
 

Genotoxicity studies are discussed in Section 2.4.
 
OTTO FUEL II AND ITS COMPONENTS 66 

2. HEALTH EFFECTS 

2.2.3.8 Cancer 

No studies were Located regarding cancer in humans or animals after dermal exposure to Otto Fuels XI 

or its components. 

2.3 TOXICOKINETICS 

Otto Fuel II is a mixture of three components. Discussion of the toxicokinetics of Otto Fuel II is 

directed specifically at the toxicokinetics of the individual components of Otto Fuel II. This has been 

done because the individual components of Otto Fuel II, and not the mixture itself, are subject to 

absorption, distribution, metabolism, and excretion by the body based upon their individual physical 

and chemical characteristics. 

Data regarding the toxicokinetics of the components of Otto Fuel II in humans are limited to a single 

study in volunteers exposed to propylene glycol dinitrate by the inhalation route. These data provide 

qualitative evidence that propylene glycol dinitrate may be absorbed in humans by this route. There 

are no data regarding oral or dermal absorption of 2-nitrodiphenylamine or dibutyl sebacate in humans. 

There is qualitative evidence that animals can absorb propylene glycol dinitrate after inhalation, oral, 

and dermal exposure, and also, that animals can absorb 2-nitrodiphenylamine and dibutyl sebacate after 

oral exposure. The mechanisms by which the components of Otto Fuel II are transported to the tissues 

are unknown. There are no data regarding distribution patterns for the components of Otto Fuel II or 

their metabolites in humans or animals. No information is available regarding the metabolism of the 

components of Otto Fuel II in humans. In animal studies, limited data suggest that propylene glycol 

dinitrate undergoes enzymatic reduction to the mononitrates and nitrite, with the subsequent formation 

of inorganic nitrate. No data were available for 2-nitrodiphenylamine or dibutyl sebacate. There is no 

information on how 2-nitrodiphenylamine or dibutyl sebacate or their potential metabolites are 

excreted in humans or animals. Qualitative information indicates that humans may excrete unchanged 

propylene glycol dinitrate in expired air after inhalation exposure and that urinary nitrate may represent 

a major excretion for propylene glycol dinitrate in animals after dermal exposure. The mechanism of 

2-nitrodiphenylamine or dibutyl sebacate toxicity is unknown. The toxicity of propylene glycol 

dinitrate is related to its vasodilating properties and its methemoglobin forming capacity in the red 

blood cells. 
OTTO FUEL II AND ITS COMPONENTS 67 

2. HEALTH EFFECTS 

2.3.1 Absorption 

2.3.1.1 Inhalation Exposure 

No studies were located that examined the absorption of the nonvolatile components of Otto Fuel II, 

2-nitrodiphenylamine and dibutyl sebacate, in humans after inhalation exposure. 

Limited information exists regarding absorption of the Otto Fuel II component, propylene glycol 

dinitrate, in humans as a result of inhalation exposures. Less than 5 ppb (limit of detection of the 

method) of propylene glycol dinitrate were measured in the blood of volunteers during a 3.2-hour 

exposure to test atmospheres containing 1.5 ppm propylene glycol dinitrate (Stewart et al. 1974), 

indicating that absorption occurs during inhalation exposures. 

No studies were located that examined the absorption of two of the components of Otto Fuel II, 

2-nitrodiphenylamine and dibutyl sebacate, in animals after inhalation exposure. 

Data are also extremely limited regarding absorption of the Otto Fuel II component, propylene glycol 

dinitrate, in animals as a result of inhalation exposures. Exposure of monkeys to concentrations of 

1.6 ppm and 4.2 ppm of propylene glycol dinitrate for 20 and 14 days, respectively, resulted in the 

detection of small amounts of propylene glycol dinitrate in plasma (Mattsson et al. 1981). During 

exposures to 1 .6 ppm, 35 ug/mL propylene glycol dinitrate was detected in plasma, and during 

exposures at 4.2 ppm, 170 ug/mL was detected in plasma. 

2.3.1.2 Oral Exposure 

No studies were located that examined the absorption of the components of Otto Fuel II, propylene 

glycol dinitrate, 2-nitrodiphenylamine, dibutyl sebacate, in humans after oral exposure. 

No quantitative data regarding oral absorption of the components of Otto Fuel II, propylene glycol 

dinitrate, 2-nitrodiphenylamine, and dibutyl sebacate, were located. However, all three components 

have been demonstrated to cause some measure of toxicity after ingestion (American Cyanamid 1982; 

Andersen and Mehl 1979; Clark and Litchfield 1969; Jones et al. 1972; Smith 1953), indicating some 

gastrointestinal absorption. 
OTTO FUEL II AND ITS COMPONENTS 68 

2. HEALTH EFFECTS 

2.3.1.3 Dermal Exposure 

No studies were located that examined the absorption of the components of Otto Fuel II, propylene 

glycol dinitrate, 2-nitrodiphenylamine, dibutyl sebacate, in humans after dermal exposure. 

Also, no studies were located that either directly or indirectly examined the absorption of two of the 

components of Otto Fuel II, 2-nitrodiphenylamine and dibutyl sebacate, in animals after dermal 

exposure. Information supporting the dermal absorption of propylene glycol dinitrate was obtained 

from studies demonstrating systemic toxicity after dermal exposure in rats (Clark and Litchfield 1969) 

and rabbits (Jones et al. 1972) and from a recent study which attempted to quantify absorption in rats 

(Godin et al. 1993). For example, a transient decrease in hemoglobin was observed following dermal 

application of doses of propylene glycol dinitrate as low as 1,000 mg/kg/day, 2 hours/day, for 20 days 

to rabbits (Jones et al. 1972). Also, observation of elevated levels of the metabolite nitrate in the urine 

of rabbits receiving a dermal dose of 4,000 mg/kg/day supported the absorption of propylene glycol 

dinitrate after dermal exposure (Jones et al. 1972). In a recent study in rats (Godin et al. 1993), 

dermal absorption of propylene glycol dinitrate was estimated as the difference between the amount of 

compound applied and the amount that could be later extracted from the skin. It should be noted, 

however, that this difference may not necessarily indicate absorption since local metabolism may 

occur. The authors found that, in general, absorption was inversely related to the amount applied, 

such that 75% of a 5 mg/kg dose was presumably absorbed, whereas only 20% of a 450 mg/kg dose 

was absorbed. 

2.3.2 Distribution 

2.3.2.1 Inhalation Exposure 

Extremely little information is available regarding the distribution of the components of Otto Fuel II 

following inhalation exposure in humans. No information was located regarding the distribution of 

2-nitrodiphenylamine or dibutyl sebacate. The only information located regarding the distribution of 

propylene glycol dinitrate in humans was the observation that propylene glycol dinitrate could be 

measured in the blood of volunteers during inhalation exposures to propylene glycol dinitrate 

volatilized from Otto Fuel II (Stewart et al. 1974). 
OTTO FUEL II AND ITS COMPONENTS 69 

2. HEALTH EFFECTS 

Similarly, no information was located regarding the distribution of 2-nitrodiphenylamine or dibutyl 

sebacate in animals after inhalation exposure. Also, no information was located regarding a 

differential distribution of propylene glycol dinitrate in animals after inhalation exposure. The only 

information located regarding the distribution of propylene glycol dinitrate in animals was the 

observation that propylene glycol dinitrate could be measured in plasma of monkeys during inhalation 

exposures to concentrations of 1.6 and 4.2 ppm (Mattsson et al. 1981). In vitro studies using dog 

blood have shown that propylene glycol dinitrate preferentially associates with red blood cells in the 

blood (Air Force 1982b). The ratio of propylene glycol dinitrate in red blood cells versus plasma was 

2.12. 

2.3.2.2 Oral Exposure 

No information was located regarding the distribution of the components of Otto Fuel II in humans or 

animals after oral exposure. 

2.3.2.3 Dermal Exposure 

No information was located regarding the distribution of the components of Otto Fuel II in humans or 

animals after dermal exposure. 

2.3.3 Metabolism 

2.3.3.1 Inhalation Exposure 

No information was located regarding the metabolism of the components of Otto Fuel II in humans 

after inhalation exposure. 

No studies were located that examined the metabolism of either 2-nitrodiphenylamine or dibutyl 

sebacate in animals after inhalation exposure. Also, no studies were located that followed the 

metabolism of propylene glycol dinitrate in animals after inhalation exposure. The only information 

relating to the metabolism of propylene glycol dinitrate after inhalation exposure was the observation 

of elevated blood levels of inorganic nitrate, a metabolic product of propylene glycol dinitrate, in dogs 

and monkeys exposed to 35 ppm for 24 hours/day for 90 days (Jones et al. 1972). Nitrate is not 
OTTO FUEL II AND ITS COMPONENTS 70 

2. HEALTH EFFECTS 

specific to propylene glycol dinitrate, however; thus, an increase in urinary nitrates is not specific for 

propylene glycol dinitrate exposure. 

2.3.3.2 Oral Exposure 

No information was located regarding the metabolism of the components of Otto Fuel II in humans or 

animals after oral exposure. 

2.3.3.3 Dermal Exposure 

No information was located regarding the metabolism of the components of Otto Fuel II in humans or 

animals after dermal exposure. 

2.3.3.4 Other Routes of Exposure 

No information was located on the metabolism of the components of Otto Fuel II in humans exposed 

by other routes. 

Also, no information was located on the metabolism of 2-nitrodiphenylamine in animals exposed by 

other routes. The metabolism of propylene glycol dinitrate has been studied in animals after parenteral 

administration (Clark and Litchfield 1969). Subcutaneous injection of 65 mg/kg propylene glycol 

dinitrate in rats caused a rapid increase in blood levels of propylene glycol dinitrate. Peak blood 

levels of propylene glycol dinitrate were observed within 1 hour and then were observed to decline to 

zero by 8-12 hours postinjection. Appearance of metabolites of propylene glycol dinitrate in the blood 

was maximal 2-4 hours postinjection and had declined to essentially zero by 8-12 hours postinjection. 

The predominant metabolite observed in the blood was nitrate, with propylene glycol 2-mononitrate 

observed at approximately one-half the concentration of inorganic nitrate. The levels of propylene 

glycol 1-mononitrate and inorganic nitrite were less than half that of propylene glycol 2-mononitrate. 

Similar results have been reported in rats after intravenous injection of 0.1-30 mg propylene glycol 

dinitrate/kg (Godin et al. 1994). In that study, maximum concentration of metabolites (propylene 

glycol 2-mononitrate and propylene glycol I-mononitrate) in blood was achieved 10 minutes after the 

injection. Elimination of the parent compound from blood was monoexponential. For doses of 0.3, 3, 

and 30 mg/kg, the elimination half-time of propylene glycol dinitrate was 8.8, 13.1, and 17.4 hours, 
OTTO FUEL II AND ITS COMPONENTS 71 

2. HEALTH EFFECTS 

respectively. Rapid metabolism of propylene glycol dinitrate in vitro has also been observed. 

Incubation of propylene glycol dinitrate in rat blood resulted in degradation of approximately half of 

the propylene glycol dinitrate by 60 minutes and degradation of half of the remainder by 120 minutes 

(Clark and Litchfield 1969). Levels of inorganic nitrate and the mononitrates increased with time, but 

only small amounts of inorganic nitrite were observed. The breakdown of propylene glycol dinitrate 

in vitro was shown to occur primarily in the erythrocytes, as no degradation in purified plasma was 

observed (Clark and Litchfield 1969). In contrast with the in vivo situation, however, the mononitrates 

were stable and did not undergo further degradation. Based on these observations and their study of 

the metabolism of ethylene glycol dinitrate (Clark and Litchfield 1967) the study authors proposed the 

following metabolic, scheme (Figure 2-4): A nitrate group of propylene glycol dinitrate could be 

reduced to give an organic nitrite-nitrate, followed by hydrolysis to yield the mononitrate and 

inorganic nitrite. The inorganic nitrite in the blood could then be oxidized to inorganic nitrate. The 

authors suggested that the predominance of the 2-isomer in the blood may have been due to either its 

more rapid formation or the more rapid degradation of the 1-isomer. 

The only information regarding metabolism of dibutyl sebacate was an in vitro analysis in which 

dibutyl sebacate was added to a preparation of pancreatic lipase (Smith 1953). Hydrolysis of dibutyl 

sebacate in the lipase preparation was reported to occur more rapidly than the hydrolysis of triolein, 

causing the author to speculate that dibutyl sebacate is metabolized in the body by the same pathways 

used in normal fat metabolism. No other information on the metabolism of dibutyl sebacate was 

located. 

. 

2.3.4 Excretion 

2.3.4.1 Inhalation Exposure 

No studies were located that examined the excretion of 2-nitrodiphenylamine or dibutyl sebacate in 

humans after inhalation exposure. 

Alveolar breath samples taken from volunteers during and after exposure to 1.5 ppm propylene glycol 

dinitrate demonstrated the short duration of excretion of this chemical in expired air (Stewart et al. 

1974). During exposure, alveolar breath samples contained between 20 and 35 ppb propylene glycol 

dinitrate. By 5 minutes after the termination of exposure, only between 1 and 5 ppb of propylene 

OTTO FUEL II AND ITS COMPONENTS 73 

2. HEALTH EFFECTS
 

glycol dinitrate were found in expired air. No measurable propylene glycol dinitrate was found in 

expired air I5 minutes after the termination of exposure. No information on other routes of excretion 

of propylene glycol dinitrate in humans was located. 

No studies were located that examined the excretion of any of the components of Otto Fuel II in 

animals after inhalation exposure. 

2.3.4.2 Oral Exposure 

No studies were located that examined the excretion of any of the components of Otto Fuel II in 

humans or animals after oral exposure. 

2.3.4.3 Dermal Exposure 

No studies were located that examined the excretion of any of the components of Otto Fuel II in 

humans after dermal exposure. 

No studies were located regarding the excretion of 2-nitrodiphenylamine or dibutyl sebacate in animals 

after dermal exposure. Only extremely limited informaticq was found regarding excretion of 

propylene glycol dinitrate in animals after dermal exposure. One study reported that excretion of 

nitrate in the urine of rabbits exposed to 4,000 mg/kg/day for 2 hours/day for 20 days accounted for 

approximately 7% of nitrate in the propylene glycol dinitrate that had been applied (Jones et al. 1972). 

Because excess propylene glycol dinitrate was wiped off each day at the end of the 2-hour exposure 

period, the excretion of nitrate relative to the applied dose of propylene glycol dinitrate is unknown. 

2.3.4.4 Other Routes of Exposure 

No information was located on the excretion of the components of Otto Fuel II in humans exposed by 

other routes. 

No information was located on the excretion of 2-nitrodiphenylamine or dibutyl sebacate in animals 

exposed by other routes. Subcutaneous injection of a dose of 65 mg propylene glycol dinitrate/kg in 

the rat resulted in rapid excretion of unmetabolized propylene glycol dinitrate and its metabolites in 
OTTO FUEL II AND ITS COMPONENTS 74 

2. HEALTH EFFECTS 

the urine (Clark and Litchfield 1969). Urinary excretion of propylene glycol dinitrate and its 

metabolites was essentially complete within 24 hours. Inorganic nitrate was the major metabolite 

excreted in the urine, accounting for approximately 56% of the nitrate in the injected dose. 

Unmetabolized propylene glycol dinitrate and other metabolites were present in the urine in amounts 

less than 0.5% of the injected dose. Excretion of unmetabolized propylene glycol dinitrate in the urine 

accounted for less than 1% of an intravenous dose (Air Force 1982b). In addition, less than 1% of a 

dose of propylene glycol dinitrate administered intravenously was excreted unchanged in expired air 

(Air Force 1982b). The major means of elimination of propylene glycol dinitrate from the blood was 

by metabolism through stepwise removal of nitrate radicals. The rate constant for elimination by 

metabolism was estimated as 0.895 min-1 (Air Force 1982b). 

2.3.5 Mechanisms of Action 

No information was located regarding the mechanism by which propylene glycol dinitrate, 

2-nitrodiphenylamine, or dibutyl sebacate enter the blood stream from the lungs, skin, or 

gastrointestinal tract. The mechanism of propylene glycol dinitrate toxicity is related to its 

vasodilating capacity. Propylene glycol dinitrate is an organic nitrate and shares many of the 

cardiovascular properties of therapeutic nitrates such as nitroglycerin, which is widely used for the 

symptomatic treatment of angina pectoris (Nickerson 1975). Organic nitrates induce peripheral 

vasodilation, decreased ventricular ejection time, relaxation, and a longer period of coronary blood 

flow. One of the earliest consequences of overexposure to propylene glycol dinitrate (or to Otto Fuel 

II) is a vasodilation of the cerebral vessels, which is believed to be the major factor in the 

development of the typical “trinitrotoluene” headache. Should the overexposure be more severe, the 

relaxation of the vascular smooth muscle can result in a fall in blood pressure followed by a 

compensatory vasoconstriction (Abrams 1980). However, a decrease in the magnitude of the 

vasodilating effect has been observed after repeated exposure to organic nitrates. Although the exact 

mechanism of initiation and maintenance of tolerance to organic nitrates is not known, several 

possibilities have been suggested, including depletion of sulfhydryl groups at the receptor sites, 

reduced availability or activity of the active intermediate S-nitrosothiol, and altered pharmacokinetics 

leading to decreased nitrate concentration in vascular tissues (Parker 1985). Massive overexposure to 

propylene glycol dinitrate can produce toxic levels of methemoglobin. This property is shared by 

many organic and inorganic nitrates and also by aromatic amines, 2-nitrodiphenylamine among them 

(Beard and Noe 1981; Donovan 1990; Ellenhom and Barceloux 1988). Methemoglobinemia is defined 
OTTO FUEL II AND ITS COMPONENTS 75 

2. HEALTH EFFECTS
 

as a methemoglobin concentration of greater than 1%, and it results from iron in the normal ferrous 

state being oxidized to the ferric state at a rate that exceeds the erythrocyte’s reducing capacity. 

Methemoglobin is unable to combine reversibly with oxygen and carbon dioxide and also causes a 

shift in the oxygen dissociation curve toward increased oxygen affinity, preventing the transfer of 

oxygen from the blood to the tissues. The possible mechanism of dibutyl sebacate toxicity is not 

known. 

2.4 RELEVANCE TO PUBLIC HEALTH 

Exposure to Otto Fuel II may occur by the inhalation, oral, or dermal routes. The only component of 

Otto Fuel II with significant volatility is propylene glycol dinitrate. Thus, inhalation exposures to Otto 

Fuel II would consist primarily of inhalation exposure to propylene glycol dinitrate. Oral exposures to 

all three components as well as the mixture, Otto Fuel II, are possible through consumption of 

contaminated water. Information was located that indicated that propylene glycol dinitrate and 

2-nitrodiphenylamine are released into waste water effluent streams from plants manufacturing and/or 

using these substances as a military propellant. It is unknown whether oral exposure to propylene 

glycol dinitrate and 2-nitrodiphenylamine may occur through consumption of contaminated food 

products because extremely limited data are available on their presence in food products or their 

bioaccumulation, biomagnification, or biodegradation. It is likely that significant ingestion of dibutyl 

sebacate may occur as a result of its civilian use in food packaging materials and as a flavor enhancer 

in ice cream, candy, baked goods, and non-alcoholic beverages. It is unknown to what extent dermal 

exposure to Otto Fuel II and its components is likely through contact with contaminated soils because 

information on the extent of soil contamination, leaching, and/or soil adsorption of these substances 

was not located. Limited information was also located regarding the degradation of the components in 

the environment, but the available data indicate that degradation would occur fairly rapidly (i.e., within 

days), It is likely that dermal contact with dibutyl sebacate may be significant as a result of the 

civilian use of this substance (as a lubricant in shaving lotions). 

The group with the greatest likelihood of exposure to Otto Fuel II consists of persons with 

occupational exposure to torpedo propellants as this is the predominant use of Otto Fuel II. 

Information on the effects that occur in humans comes from studies of workers occupationally exposed 

to Otto Fuel II and from experimental exposures of humans to propylene glycol dinitrate and dibutyl 

sebacate. These studies indicate that short-term exposure to Otto Fuel II may result in headache, loss 
OTTO FUEL II AND ITS COMPONENTS 76 

2. HEALTH EFFECTS
 

of balance, poor eye-hand coordination, eye irritation, and dizziness, and that propylene glycol 

dinitrate is probably the component of Otto Fuel II responsible for these effects. Studies of longer-term 

exposure suggest that humans may experience an increased incidence of angina and myocardial 

infarctions. 

For the most part, studies in animals support the observation of these toxic effects. In addition, animal 

studies indicate that methemoglobinemia, degenerative hepatic and renal effects, and developmental 

toxicity (at maternally toxic doses) may occur. 

Minimal Risk Levels for Otto Fuel II and Its Components. 

Inhalation MRLs. 

•	 An MRL of 0.003 ppm has been derived for acute inhalation exposure (14 days or less) to 

propylene glycol dinitrate. 

The acute inhalation MRL was based on a NOAEL for altered visual evoked responses in volunteers 

exposed to concentrations ranging from 0.03 to 1.5 ppm for 1-8 hours (Stewart et al. 1974). At 

0.2 ppm 7 of 9 subjects reported headaches. The change in visual evoked response was duration-related
 

indicating a cumulative effect. Exposure to 0.5 ppm for 8 hours resulted in nausea, dizziness,
 

and more markedly altered visual evoked responses. These results are supported by other studies in
 

humans (Horvath et al. 198 1) and studies in monkeys (Mattsson et al. 1981).
 

•	 An MRL of 0.00004 ppm has been derived for intermediate inhalation exposure (15-364 days) 

to propylene glycol dinitrate. 

The intermediate inhalation MRL was based on a LOAEL for hematological changes in dogs exposed 

to 0.2 ppm propylene glycol dinitrate intermittently for 14 months (Air Force 1985a). As early as 

4 weeks into the study, significantly decreased hematocrit, hemoglobin, red blood cells, and 

reticulocytes were observed, and by exposure day 44, significantly increased methemoglobin levels 

were observed. No other exposure level was tested. These results are supported by human data 

(Donovan 1990), and also by studies in other animal species, such as guinea pigs, rats, and monkeys 

(Jones et al. 1972). 
OTTO FUEL II AND ITS COMPONENTS 77 

2. HEALTH EFFECTS 

•	 An MRL of 0.00004 ppm has been derived for chronic inhalation (365 days or more) to 

propylene glycol dinitrate. 

The chronic inhalation MRL was based on a LOAEL for hematological changes in dogs exposed to 

0.2 ppm propylene glycol dinitrate intermittently for 14 months (Air Force 1985a). Significant 

hematological changes, such as decreased hematocrit, hemoglobin, red blood cells, and reticulocytes, 

and increased in methemoglobin concentration were observed before the seventh week of exposure. 

These effects persisted at the termination of the study at 14 months. Methemoglobinemia was also 

reported in rats exposed to propylene glycol dinitrate for 1 year (Air Force 1985a). 

Inhalation MRLs were not derived for Otto Fuel II due to lack of proper exposure characterization in 

the human studies and lack of animal data. Inhalation MRLs were not derived for 

2-nitrodiphenylamine, or dibutyl sebacate due to both lack of human and animal data. 

Oral MRLs. 

No oral MRLs were derived for Otto Fuel II or its components due to lack of adequate human and 

animal data. An intermediate and a chronic duration study were identified for oral exposure to dibutyl 

sebacate (Smith 1953); however, the fact that this early study represents the only existing information 

on dibutyl sebacate precludes its use as the basis for MRLs. 

Dermal MRLs were not derived because of the lack of an appropriate methodology for doing so. 

Death. No studies were located that reported deaths in humans attributable to exposure to Otto Fuel 

II or any of its components. Studies in animals indicate that there are species differences in lethality 

of propylene glycol dinitrate by the inhalation route. Rabbits appear most sensitive with deaths 

reported after continuous exposure to concentrations as low as 35 ppm (Jones et al. 1972). Animal 

studies also indicate that propylene glycol dinitrate is the most toxic component of Otto Fuel II 

following exposure by the oral route. Oral LD,, values in rats for propylene glycol dinitrate ranged 

from 250 to I, 190 mg/kg (Andersen and Mehl 1979; Clark and Litchfield 1969; Jones et al. 1972), 

whereas the oral LD,, values in rats for 2-nitrodiphenylamine and dibutyl sebacate were 6,150 (Army 

1979) and 17,200 mg/kg (Komarova 1976, 1979), respectively. Comparison of the dermal lethality of 

the individual components of Otto Fuel II in rabbits is not as straightforward because of differing 
OTTO FUEL II AND ITS COMPONENTS 78 

2. HEALTH EFFECTS 

durations of exposure and incomplete information on the doses applied; however, the same hierarchy 

of toxicity appears to hold (Army 1979; Jones et al. 1972; Mallette and Von Haam 1952b). Very 

limited information is available on the cause of death in these studies, but symptoms observed in 

propylene glycol dinitrate-treated animals prior to death are consistent with methemoglobin-induced 

anoxia (Jones et al. 1972). 

Although environmental data are limited, based on the potentially rapid degradation of the components 

of Otto Fuel II and the high doses necessary to cause death, it is unlikely that propylene glycol 

dinitrate, 2-nitrodiphenylamine, or dibutyl sebacate levels near hazardous waste sites are sufficient to 

cause death in exposed populations. 

Systemic Effects. 

Respiratory Effects. A small percentage of workers with occupational exposure to Otto Fuel II have 

reported experiencing dyspnea during occupational exposure to this substance (Horvath et al. 1981); 

however, the majority of animal studies have not reported similar effects, and those that have, do not 

clearly demonstrate the cause for this symptom. Application of a large concentration of propylene 

glycol dinitrate to the ‘skin of rabbits (2,000 mg/kg/day) has been reported to cause rapid and shallow 

breathing (Jones et al. 1972), but examination of the respiratory system at necropsy did not reveal any 

abnormalities that might account for the change in breathing pattern. Chronic inhalation exposure of 

rats to 35 ppm propylene glycol dinitrate resulted in microscopic evidence of slight respiratory 

irritation (mild degeneration of the nasal epithelium and very slight pulmonary inflammation) (Air 

Force 1985a); however, it is unlikely that these findings are associated with the dyspnea reported by 

exposed workers. Dyspnea has been reported to be a common finding in patients with clinically 

significant methemoglobinemia (see Hematological Effects below) (Bronstein and Currance 1988); 

thus, the dyspnea described in the above reports may have been associated with methemoglobinemia. 

The combined results of these studies indicate that sensitive members of exposed populations near 

hazardous waste sites may experience difficulty breathing when exposed to sufficiently high 

concentrations, but the cause of this effect remains unknown. 

Cardiovascular Effects. The major component of Otto Fuel II, propylene glycol dinitrate, is an 

organic nitrate and shares many of the cardiovascular properties of therapeutic nitrates such as amyl 

nitrate and nitroglycerin. The primary cardiovascular action of the therapeutic nitrates is to relax 
OTTO FUEL II AND ITS COMPONENTS 79 

2. HEALTH EFFECTS 

vascular smooth muscle resulting in a fall in blood pressure. Under normal conditions, this decrease in 

blood pressure is counteracted by a reflex vasoconstriction and increase in heart rate (Nicker-son 1975). 

Effects associated with both nitrate-induced vasodilation and compensatory vasoconstriction have been 

reported in studies evaluating the human response to Otto Fuel II and/or propylene glycol dinitrate 

exposure. 

Headaches (of likely vasodilatory origin) were reported as a frequent symptom by workers exposed to 

Otto Fuel II (ATSDR 1990; Horvath et al. 1981) and by subjects experimentally exposed to propylene 

glycol dinitrate (Stewart et al. 1974). These reports are consistent with the reported ability of aliphatic 

nitrates to cause meningeal blood vessel dilation which results in a characteristic type of headache 

(Nickerson 1975). The earliest and most commonly encountered symptom of overexposure to 

propylene glycol dinitrate (or Otto Fuel II) is headache. In the study by Stewart et al. (1974), the 

severity and frequency of the headaches decreased with repeated exposures, indicating adaptation to 

the vasodilatory effects. 

In studies of other aliphatic nitrates, continued adaptive vasoconstriction after removal from the source 

of exposure has been reported to be the cause of coronary insufficiency (Carmichael and Lieben 1963; 

Morton 1977). The increased incidence of angina pectoris and myocardial infarction among workers 

exposed to Otto Fuel II (Forman et al. 1987) indicates that compensatory vasoconstriction of the blood 

vessels of the heart may lead to coronary insufficiency in these workers. 

Studies in animals have assessed the vasodilatory activity of propylene glycol dinitrate following 

exposure by the dermal route (Clark and Litchfield 1969) and following parenteral administration (Air 

Force 1982b; Clark and Litchfield 1969; Pharmackon 1988). These studies demonstrate that propylene 

glycol dinitrate causes a decrease in blood pressure that is rapidly corrected. An increase in heart rate 

also occurs as part of the compensatory response. Comparison of the time-course of the vasodilation 

with the blood levels of propylene glycol dinitrate and its metabolites indicated that propylene glycol 

dinitrate levels correlated most closely with the decrease in blood pressure (Clark and Litchfield 1969). 

Animal studies also suggest that the heart may be adversely affected by exposure to propylene glycol 

dinitrate. Evidence of myocardial degeneration was observed in rabbits receiving a large dermal dose 

of propylene glycol dinitrate (Jones et al. 1972). 
OTTO FUEL II AND ITS COMPONENTS 80 

2. HEALTH EFFECTS
 

These results suggest that persons exposed to sufficient concentrations of Otto Fuel II or propylene 

glycol dinitrate at hazardous waste sites may experience transitory vasodilation and headaches. The 

development of a compensatory level of vasoconstriction may also lead to coronary vasospasm in 

susceptible individuals. 

Hematological Effects. In addition to their effects on the cardiovascular system, nitrates are also 

known to oxidize the heme iron molecule of hemoglobin, resulting in the formation of methemoglobin 

(Donovan 1990). Experimental acute-duration exposure of humans to low levels of propylene glycol 

dinitrate did not result in elevation of methemoglobin levels (Stewart et al. 1974). However, studies in 

animals demonstrated that exposure to high levels of Otto Fuel II or propylene glycol dinitrate for 

short periods or exposure to low levels for longer periods resulted in elevation of blood 

methemoglobin levels (Air Force 1982b, 1985a; Cooper et al. 1993; Jones et al. 1972). 

Nitrates have also been reported to oxidize the sulfhydryl groups of the globin portion of the 

hemoglobin molecule resulting in hemoglobin denaturation and hemolysis (ATSDR 1991; Cotran et al. 

1989). Evidence of hemolysis and phagocytosis of hemoglobin has been observed in animal studies 

(Air Force 1985a; Jones et al. 1972). Heavy increases in hemosiderin deposits in the spleen, liver, and 

kidneys were observed in rats, dogs, and monkeys following continuous inhalation exposure to 

moderate levels of propylene glycol dinitrate (Jones et al. 1972). Also, decreased red cell count, 

hemoglobin, and/or hematocrit were observed in rabbits after short-term, high-level dermal exposure 

(Jones et al. 1972) and dogs after long-term, low-level exposure (Air Force 1985a) to propylene glycol 

dinitrate. 

Comparison of the susceptibility of hemoglobin from various species to oxidation by propylene glycol 

dinitrate revealed that human hemoglobin is relatively resistant to oxidation (Wyman et al. 1985). 

Therefore, it is unlikely that exposure to low levels of propylene glycol dinitrate at hazardous waste 

sites would result in clinically significant methemoglobinemia in most persons. However, some 

persons are highly susceptible to agents that oxidize hemoglobin (see also Section 2.7), and such 

persons may experience elevated methemoglobin levels when exposed to Otto Fuel II or propylene 

glycol dinitrate at hazardous waste sites. Intermediate- and chronic-duration inhalation MRLs were 

derived based on a study in which dogs exhibited increased methemoglobin levels and decreased red 

blood cells, hematocrit, and hemoglobin during intermediate-to-chronic inhalation exposures (Air Force 

1985a). 
OTTO FUEL II AND ITS COMPONENTS 81 

2. HEALTH EFFECTS
 

Musculoskeletal Effects. Although no adverse effects on the musculoskeletal system have been 

identified in humans exposed to Otto Fuel II or its components, a study in rats demonstrated an 

increase in osteosclerosis in females chronically exposed to propylene glycol dinitrate (Air Force 

1985a). No studies were available that corroborated this effect; thus, it is unknown whether it may 

have been incidental or exposure related. Insufficient information is available to assess the relevance 

of this finding to persons exposed to Otto Fuel II or propylene glycol dinitrate at hazardous waste 

sites. 

Hepatic Effects. Studies in humans have not demonstrated adverse effects of Otto Fuel II or its 

components on the liver. However, studies in animals continuously exposed to moderate levels of 

propylene glycol dinitrate by inhalation (16-35 ppm) have demonstrated degenerative hepatocellular 

changes (Jones et al. 1972). Intermittent exposures to similar levels did not, however, cause such 

changes (Air Force 1985a). Thus, it is possible that persons continuously exposed to Otto Fuel II or 

propylene glycol dinitrate by virtue of their living and/or working in close proximity to a hazardous 

waste site may also experience some degree of hepatocellular damage. 

Renal Effects. No adverse renal effects have been observed in studies of persons exposed to Otto 

Fuel II or its components. However, a number of animal studies have shown renal toxicity resulting 

from propylene glycol dinitrate exposure. Evidence of renal toxicity in these studies includes acute 

tubular necrosis in rats and elevated serum urea nitrogen and decreased serum alkaline phosphatase in 

monkeys continuously exposed to moderate levels of propylene glycol dinitrate (Jones et al. 1972); 

vacuolar changes in the proximal convoluted tubules of kidneys of rabbits to which a large dermal 

dose of propylene glycol dinitrate had been applied (Jones et al. 1972); and decreased urine production 

and increased red blood dells in the urine of dogs receiving an intravenous dose of 2 mg/kg of 

propylene glycol dinitrate (Air Force 1982b). The renal toxicity observed in these studies may be the 

result either one or a combination of the following causes: a direct toxic effect of propylene glycol 

dinitrate on the kidneys or renal toxicity resulting from the urinary excretion of massive amounts of 

hemoglobin resulting from hemolysis (Cotran et al. 1989) (see also Hematological Effects above). 

Based on the observation of renal toxicity in animals, it may be concluded that it is possible that 

persons exposed to sufficiently high levels of Otto Fuel II or propylene glycol dinitrate at hazardous 

waste sites may experience renal toxicity. 
OTTO FUEL II AND ITS COMPONENTS 82 

2. HEALTH EFFECTS
 

Dermal Effects. Animal studies indicate that Otto Fuel II and its components are only very slightly to 

moderately irritating when applied to rabbit skin (Army 1979; Cooper et al. 1993; Jones et al. 1972; 

Komarova 1976, 1979; Mallette and Von Haam 1952b), and dibutyl sebacate has been demonstrated to 

be nonirritating to the skin in humans (Askarova and Muryseva 1975; Mallette and Von Haam 1952b). 

Thus, it is unlikely that skin contact with Otto Fuel II or its components at hazardous waste sites 

would result in a severe skin reaction. 

Ocular Effects. Slight eye irritation has been reported by subjects experimentally exposed to 

propylene glycol dinitrate by inhalation (Stewart et al. 1974). This finding has been corroborated in 

an eye irritation study in which propylene glycol dinitrate was instilled into the eyes of rabbits (Jones 

et al. 1972). Thus, persons exposed to Otto Fuel II or propylene glycol dinitrate at hazardous waste 

sites may experience mild eye irritation. 

Body Weight Effects. No significant effects on body weight were observed in rats mice, guinea pigs, 

dogs, and monkeys after intermediate- or chronic-duration exposure to propylene glycol dinitrate (Air 

Force 1985a; Jones et al. 1972). However, a significant reduction in body weight gain was reported in 

rats and rabbits exposed to propylene glycol dinitrate dermally during pregnancy (Cooper et al. 1993). 

The relevance of these results to human health is unknown. 

Immunological and Lymphoreticular Effects. Very little information was located regarding 

immunological effects of Otto Fuel II or its components in humans or animals. Dibutyl sebacate was 

not shown to cause dermal sensitization when applied to the skin of human volunteers or rabbits 

(Mallette and Von Haam 1952b). However, 3.3% of workers occupationally exposed to lubricants 

containing dibutyl sebacate reacted to application of this material in a skin test (Askarova and 

Muryseva 1975). Hemosiderin deposits were observed in the spleens of dogs and monkeys, but not 

rats or guinea pigs, exposed continuously for 90 days to atmospheres containing 35 ppm propylene 

glycol dinitrate (Jones et al. 1972). This response probably reflects increased destruction of 

erythrocytes. Insufficient information exists to conclude whether exposure to dibutyl sebacate at 

hazardous waste sites might result in sensitization or whether the other components of Otto Fuel II at 

hazardous waste sites may cause other adverse immunological effects. 

Neurological Effects. Studies in humans have demonstrated adverse effects of acute-duration 

exposure to low levels of propylene glycol dinitrate (0.5 ppm) on coordination (Stewart et al. 1974) 
OTTO FUEL II AND ITS COMPONENTS 83 

2. HEALTH EFFECTS
 

and effects of acute-duration exposure to 0.2 ppm on subclinical indicators of neuronal function 

(Horvath et al. 1981; Stewart et al. 1974). An acute-duration inhalation MRL was derived for 

propylene glycol dinitrate based on altered visual responses in human subjects voluntarily exposed to 

propylene glycol dinitrate (Stewart et al. 1974). Animal studies have also demonstrated effects of 

propylene glycol dinitrate exposure on neuronal function, although most effects (ataxia, decreased 

consciousness, convulsions) have been observed following inhalation and parenteral exposure to high 

levels of this chemical (Andersen and Mehl 1979; Bogo et al. 1987; Jones et al. 1972). Behavioral 

paradigms designed to detect performance decrements caused by low-level exposure to propylene 

glycol dinitrate have given negative results (Mattsson et al. 1981). Thus, humans may be more 

sensitive than any of the other species that have been tested to the neurological effects of propylene 

glycol dinitrate. Based on the effects reported in the studies by Stewart et al. (1974) and Horvath et 

al. (1981), it is possible that persons exposed to sufficient levels of Otto Fuel II or propylene glycol 

dinitrate at hazardous waste sites may experience adverse neurological effects. 

In vitro studies have demonstrated the ability of propylene glycol dinitrate to disrupt neuromuscular 

activity (Andersen and Mehl 1979) and to inhibit monoamine oxidase activity (Kalin and Kylin 1969); 

however, it is unknown what possible role the effects observed in vitro might play in the neurotoxicity 

observed in human subjects. 

Headaches have frequently been reported both by workers occupationally exposed to Otto Fuel II and 

volunteers experimentally exposed to propylene glycol dinitrate (ATSDR 1990; Horvath et al. 1981; 

Stewart et al. 1974). However, the headaches are most likely associated with meningeal blood vessel 

dilation (Nickerson 1975) (see also Cardiovascular Effects above). 

Reproductive Effects. Studies in humans have begun to address the reproductive toxicity of 

exposure to Otto Fuel II (Forman 1988). However, for purposes of epidemiological evaluation, the 

exposed population is still too small to allow meaningful analysis of the data. Animal studies 

examining reproductive function are limited to a single study that examined the reproductive effects of 

consumption of large amounts of dibutyl sebacate in rats (Smith 1953) and a dominant lethal study in 

mice that examined the effects of oral exposure to Otto Fuel II (Navy 1982b). These studies 

demonstrated no adverse effects of consumption of large amounts of dibutyl sebacate on fertility, litter 

size, or litter survival or of Otto Fuel II on male.fertility. Routine examination of the reproductive 

organs of animals chronically exposed to propylene glycol dinitrate did not reveal any abnormalities 
OTTO FUEL II AND ITS COMPONENTS 84 

2. HEALTH EFFECTS
 

(Air Force 1985a); however, the effects of propylene glycol dinitrate and 2-nitrodiphenylamine on 

reproductive function are unknown. Thus, although dibutyi sebacate does not appear to have any 

adverse reproductive effects in either sex and Otto Fuel II does not appear to cause adverse effects on 

male reproductive function, insufficient information exists on propylene glycol dinitrate or 

2-nitrodiphenylamine to conclude whether populations exposed to these chemicals or to Otto Fuel II at 

hazardous waste sites are at risk of significant reproductive toxicity. 

Developmental Effects. Developmental toxicity consisting of increased resorptions and decreased 

fetal viability, weight, and length has been observed following dermal exposure of rats to Otto Fuel II 

during mid-gestation (Cooper et al. 1993). However, the developmental effects were observed only at 

maternally toxic doses. Reduced growth of litters of parental rats given very large amounts of dibutyl 

sebacate in their diets prior to conception has also been reported (Smith 1953). It is unlikely that 

persons exposed to dibutyl sebacate at hazardous waste sites could be exposed to sufficiently high 

concentrations of this material to adversely affect development. The absence of information on 

developmental effects of propylene glycol dinitrate or 2-nitrodiphenylamine precludes estimation of the 

developmental effects of these components of Otto Fuel II on exposed populations. 

Genotoxic Effects. No studies were located regarding the genotoxicity of Otto Fuel II or its 

components in humans. Two in vivo experiments were performed using the oral route of exposure to 

assess potential genotoxic activity of Otto Fuel II in somatic cells (bone marrow) or germinal cells 

(dominant lethal mutations in sperm) (Navy 1982b). Slight increases in the frequency of chromosome 

aberrations were seen in the bone marrow cytogenetic assay, but the finding was not definitive. 

Similarly, there was no evidence that Otto Fuel II was clastogenic in the dominant lethal assay; 

however, the number of pregnant females available for analysis did not constitute a reliable sample 

size. The only in vivo assays performed on a fuel component were two assays done with dibutyl 

sebacate (Wild et al. 1983). Both assays obtained negative results, but were incomplete. Drosophila 

melanogaster allowed to consume a 5% saccharose solution containing 19 mmol/L dibutyl sebacate 

showed no evidence of sex-linked recessive lethal mutations. Doses of dibutyl sebacate ranging from 

943 to 2,829 mg/kg did not increase the frequency of micronuclei induction in bone marrow cells 

harvested from mice receiving the test compound by intraperitoneal injection (Wild et al. 1983). 

However, less than the recommended number of animals was used, and there was no indication that 

the test material was toxic to the animals or cytotoxic to the target organ. Based on the above 

considerations, no conclusions can be reached from the available in vivo genetic toxicology assays; the 
OTTO FUEL II AND ITS COMPONENTS 85 

2. HEALTH EFFECTS 

genotoxic activity, if any, of Otto Fuel II and its constituents in whole animals remains 

uncharacterized. 

In vitro genotoxicity studies have been performed with Otto Fuel II and its constituents (propylene 

glycol dinitrate, 2-nitrodiphenylamine, and dibutyl sebacate). The U.S. Navy (1982b) concluded that 

Otto Fuel II assayed at toxic levels did not cause a significant increase in the frequency of sister 

chromatid exchange in mouse lymphoma cells in the presence or absence of rat liver microsomes (S9). 

There was also no evidence of mitotic delay at any dose. Exposure to severely cytotoxic levels (<=10% 

survival) of Otto Fuel II in the nonactivated phase of the mouse lymphoma cell forward mutation 

assay increased the mutation frequencies and the number of mutant colonies. This evidence suggesting 

mutagenesis was confirmed under S9-activated conditions. Levels ranging from 0.025% to 0.075% 

with microsomal activation induced significant and dose-related increases in the mutation frequency at 

the thymidine kinase locus. Therefore, the U.S. Navy (1982b) concluded that Otto Fuel II was 

mutagenic in this mammalian cell line. Otto Fuel II was also evaluated for mutagenesis in 

Saccharomyces cerevisiae D4 and several histidine-requiring mutant strains of Salmonella typhimurium 

(Navy 1982b). In both of these test systems, Otto Fuel II, both with and without S9 activation, was 

assayed over an appropriate range of doses (0.005-10 uL/mL) but failed to induce a mutagenic effect. 

Several authors (Kleindienst et al. 1985; McGregor et al. 1980; Shepson et al. 1985; Wild et al. 1983) 

have reported that the components of Otto Fuel II are not mutagenic in microbial systems, but none of 

their results were conclusive. Propylene glycol dinitrate was negative in the Ames test with or without 

activation at unspecified concentrations (Kleindienst et al. 1985; Shepson et al. 1985). McGregor et al. 

(1980) stated that 2-nitrodiphenylamine with or without activation did not cause mitotic recombination 

in Saccharomyces cerevisiae, gene mutation in S. typhimurium, or preferential inhibition of a polA ̄ 

Escherichia coli strain: no data were presented to support their claims. Kononova et al. (1972) 

concluded that propylene glycol dinitrate produced mutations in the r gene of phage T4B without 

activation. However, the only dose tested inactivated over 95% of the phage, casting doubts on the 

validity of the conclusion. Finally, a report that dibutyl sebacate with and without activation was 

negative in the Ames test presented no study results (Wild et al. 1983). Key in vivo genotoxicity 

studies are presented in Table 2-6 and in vitro genotoxicity studies are presented in Table 2-7. 


OTTO FUEL II AND ITS COMPONENTS 88 

2. HEALTH EFFECTS
 

Cancer. Studies in humans have not evaluated the carcinogenic potential of Otto Fuel II or its 

components. Studies in animals have examined the carcinogenic potential of inhalation exposure to 

propylene glycol dinitrate in rats and mice and have not found strong evidence of a carcinogenic 

potential (Air Force 1985a). However, the appearance of osteosarcoma and osteoma (rare tumors) in 

rats, and possibly the increase in the incidence of a common preneoplastic observation (lymphoid 

hyperplasia) in mice, precludes concluding that exposure to propylene glycol dinitrate is without a 

carcinogenic risk. No increase in the incidence of neoplasms was noted in a study examining the 

effects of chronic-duration consumption of large amounts of dibutyl sebacate in rats (Smith 1953); 

however, the number of rats used in this study was somewhat small for an adequate test of 

oncogenicity. Thus, insufficient information is available to conclude whether the potential for 

carcinogenicity exists from exposure to Otto Fuel II or its components at hazardous waste sites. 

2.5 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). 

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 (NAS/NRC 1989). The preferred 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 biologic 

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 Otto Fuel II and its components are discussed in 

Section 2.5.1. 
OTTO FUEL II AND ITS COMPONENTS 89 

2. HEALTH EFFECTS 

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 often not substance specific. They also may not 

be directly adverse, but can indicate potential health impairment (e.g., DNA adducts). Biomarkers of 

effects caused by Otto Fuel II and its components are discussed in Section 2.5.2. 

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, biologically effective dose, or target tissue response. If biomarkers of susceptibility exist, they 

are discussed in Section 2.7, Populations That Are Unusually Susceptible. 

2.5.1 Biomarkers Used to Identify or Quantify Exposure to Otto Fuel II and Its 

Components 

Extremely limited information was located regarding biomarkers that may be used to estimate 

exposures to Otto Fuel II. No standard procedures exist for identifying or quantifying exposure to 

Otto Fuel II. Furthermore, no standard procedures were identified for estimating exposure to the 

components of Otto Fuel II, propylene glycol dinitrate, 2-nitrodiphenylamine, and dibutyl sebacate. 

However, based on information on the toxicokinetics of one of the components, propylene glycol 

dinitrate (Air Force 1982b; Clark and Litchfield 1969; Jones et al. 1972; Mattsson et al. 1981; Stewart 

et al. 1974), biomarkers for exposure to this component may be proposed. 

Propylene glycol dinitrate is rapidly metabolized in the blood (Air Force 1982b; Clark and Litchfield 

1969; Kylin et al. 1966). Therefore, measurement of blood levels of this substance or the propylene 

glycol mononitrates is limited to exposures of a very large magnitude and that occur within a very few 

hours of the time at which the blood sample is obtained. Also, because propylene glycol dinitrate may 

be metabolized in isolated blood samples (Clark and Litchfield 1969), steps must be taken to prevent 

the continued metabolism of this substance. Measurement of propylene glycol dinitrate in the urine or 

in expired air is of limited value since only a very small fraction of propylene glycol dinitrate is 
OTTO FUEL II AND ITS COMPONENTS 90 

2. HEALTH EFFECTS 

excreted by these routes (Air Force I982b; Clark and Litchfield 1969; Stewart et al. 1974). 

Measurement of inorganic nitrate, a metabolic product of propylene glycol dinitrate, in the blood may 

give some indication of whether exposure levels were high. However, this biomarker may increase 

following exposure to a large number of other nitrate-containing substances. 

Urinary nitrate is the major metabolic marker for propylene glycol dinitrate (Clark and Litchfield 

1969). However, measurement of urinary nitrate as a biomarker for exposure to propylene glycol 

dinitrate is limited by the rapid excretion of nitrate in the urine following exposure (Clark and 

Litchfield 1969). Within 24 hours of exposure, excretion of nitrate in the urine may be complete. 

Measurement of urinary nitrate as a biomarker for exposure to propylene glycol dinitrate is also 

limited by the fact that a large number of inorganic and organic nitrite and nitrate compounds used 

commercially or therapeutically may produce increased urinary nitrate that is indistinguishable from 

that caused by propylene glycol dinitrate (Donovan 1990). Such nitrites and nitrates include sodium, 

potassium, and calcium nitrate (used as fertilizers and food preservatives), bismuth subnitrate 

(antidiarrheal), ammonium nitrate (diuretic, fertilizer), silver nitrate (topical burn therapy), isosorbide 

dinitrate or tetranitrate (vasodilator), amyl nitrite (cyanide therapy, vasodilator, abused substance), 

butyl and isobutyl nitrite (room odorizer, abused inhalant), sodium nitrite (cyanide therapy, food 

preservative, anticorrosive), and nitroglycerin (vasodilator, explosives). 

Methods for detecting 2-nitrodiphenylamine and dibutyl sebacate in body tissues or in excretory 

products were not located in the literature. In addition, metabolites for these chemicals have not been 

identified. Thus, measurement of these substances in bodily tissues or excretory products cannot be 

proposed as useful biomarkers of exposure. 

The physiological effects caused by exposure to propylene glycol dinitrate (vasodilation, headache, loss 

of balance, poor eye-hand coordination, eye irritation, congested nose, nausea, dizziness, and 

methemoglobin formation) either individually or in combination are not unique to propylene glycol 

dinitrate exposure. Thus, observation of any one or a combination of these effects does not contribute 

to the identification or quantification of exposure to propylene glycol dinitrate. For example, eye 

irritation may be produced by a wide range of substances. Also, a number of other chemicals are 

known to cause methemoglobinemia (e.g., aniline, benzocaine, chlorate salts, chloroquine, copper 

sulfate, dapsone, lidocaine, metoclopramide, methylene blue (high doses), monolinuron, naphthalene, 

nitrates, nitrites, nitrobenzene, nitrogen oxide, nitroglycerin, permanganate salts, phenacetin, 
OTTO FUEL II AND ITS COMPONENTS 91 

2. HEALTH EFFECTS 

phenazopyridine, phenols, prilocaine, primaquine, sulfonamides, toluidine) (Donovan 1990). Finally, 

the combination of symptoms, vasodilation, headache, methemoglobin formation, dizziness, and 

nausea, may be caused by any of a number of inorganic or organic nitrites or nitrates (Donovan 1990). 

However, if there is a known exposure event (e.g., accidental release) and a potentially exposed 

individual experiences vasodilation, headache, eye irritation, nausea, dizziness, and 

methemoglobinemia, these symptoms may be confirmatory that significant exposure has occurred. It 

must be mentioned, however, that the absence of headache almost always rules out significant 

physiological overexposure to propylene glycol dinitrate (or Otto Fuel II) in otherwise healthy 

individuals. 

For more information on biomarkers for renal and hepatic effects of chemicals see ATSDR/CDC 

Subcommittee Report on Biological Indicators of Organ Damage (1990) and for information on 

biomarkers for neurological effects see OTA (1990). 

2.5.2 Biomarkers Used to Characterize Effects Caused by Otto Fuel II and Its 

Components 

Very limited information was located regarding effects caused by Otto Fuel II. Also, limited 

information was located regarding effects caused by two of the components of Otto Fuel II, 

2-nitrodiphenylamine and dibutyl sebacate. The effects caused by propylene glycol dinitrate have, 

however, been described sufficiently to discuss possible biomarkers for these effects. Such effects 

include the characteristic type of headache, vasodilation, methemoglobin formation, and dizziness. 

In experimental exposures in humans, headache due to meningeal blood vessel dilation appears to be 

the most sensitive effect caused by propylene glycol dinitrate (Stewart et al. 1974). No studies were 

located that discussed methods for measuring meningeal vessel dilation or the resulting headaches in 

humans. However, individuals learn to differentiate this type of headache from ordinary headaches. 

Magnetic resonance imaging and positron emission tomography are noninvasive techniques that may 

be used to measure cerebral blood flow. Laser-Doppler flowmetry has been used to measure cerebral 

blood flow; however, in this method, the skull must be opened to allow the probe to be placed in 

direct contact with the duru mater (Dimagl et al. 1989; Saeki et al. 1989). 
OTTO FUEL II AND ITS COMPONENTS 92 

2. HEALTH EFFECTS
 

Measurement of vasodilation outside of the brain region may be accomplished by monitoring blood 

pressure (Air Force I982b; Stewart et al. 1974); however, in normal healthy individuals, a rapid 

vasoconstriction and increase in heart rate may limit the observation of a fall in blood pressure caused 

by exposure to low concentrations of propylene glycol dinitrate. In fact, in the study by Stewart et al. 

(1974), a reflex increase in vascular tone may have obscured any fall in blood pressure and may have 

accounted for the increase in diastolic pressure that was observed. 

Experimental exposures in humans indicate that alterations in visual evoked responses may be used to 

identify subclinical changes in central nervous system activity (Stewart et al. 1974). However, the 

type of alterations in visual evoked responses produced by propylene glycol dinitrate (increases in the 

peak-to-peak voltage amplitude) were characterized as being typical of the type of changes produced 

by central nervous system depressants. Thus, this type of change in the visual evoked responses may 

be produced by a number of central nervous system depressants. Changes in saccade velocity and 

delay have been observed in workers acutely exposed to Otto Fuel II in the absence of an effect on 

coordination or balance (Horvath et al. 1981). The authors of this study suggest that changes in 

oculomotor responses may be used to detect subclinical changes in central nervous system activity 

caused by Otto Fuel II. However, similar changes are produced by brain lesions such as those caused 

by Huntington’s chorea, brain stem degeneration, and multiple sclerosis, and from the actions of 

tranquilizers or alcohol. Thus, these changes are also not specific to the effects of Otto Fuel II. 

However, in light of a suspected exposure, these tests could be used to assess central nervous system 

involvement. 

A slate-gray cyanosis, appearing first on the mucous membranes, is produced by exposure to relatively 

high concentrations of propylene glycol dinitrate as a result of the reduced oxygen-carrying capacity of 

methemoglobin (Donovan 1990; Jones et al. 1972). Cyanosis is not, however, a specific indicator of 

methemoglobin formation. Cyanosis may also result from increased levels of deoxyhemoglobin in 

pulmonary or cardiac disease. Cyanosis may also result from agents causing sulfhemoglobin 

formation. Distinction between cyanosis due to methemoglobinemia and cyanosis due to increased 

levels of deoxyhemoglobin may be accomplished by shaking a blood sample in the air. In the case of 

elevated levels of deoxyhemoglobin, the blood should turn bright red, whereas, in the case of 

methemoglobinemia, the color of the blood (brown or grayish) should be unaffected. Distinction 

between the cyanosis caused by methemoglobin and that caused by sulfhemoglobin may be achieved 

by diluting blood in deionized water (1 : 100) with a crystal of potassium cyanide. Blood containing 
OTTO FUEL II AND ITS COMPONENTS 93 

2. HEALTH EFFECTS
 

methemoglobin should turn pink because of the formation of cyanomethemoglobin. Indicators of 

methemoglobinemia include a lactate metabolic acidosis and a normal blood oxygen content with low 

oxygen saturation. Methemoglobin concentrations in the blood may also be quantified 

spectrophotometrically. These biomarkers are not, however, specific for the methemoglobinemia 

produced by propylene glycol dinitrate. Heinz bodies in peripheral blood smears may also suggest 

methemoglobinemia (ATSDR 1991). However, Heinz bodies are not specific for methemoglobinemia. 

No information was located regarding possible biomarkers of exposure or effect for 

2-nitrodiphenylamine or dibutyl sebacate. 

2.6 INTERACTIONS WITH OTHER CHEMICALS 

No information was located regarding the influence of other chemicals on the toxicity of Otto Fuel II 

or its components, propylene glycol dinitrate, 2-nitrodiphenylamine, or dibutyl sebacate. 

Intraperitoneal administration of propylene glycol dinitrate was, however, observed to decrease ethanol 

consumption in ethanol-addicted rats (Komura 1974). This decrease in ethanol drinking behavior was 

suggested by Komura (1974) to be related to increased tissue levels of acetaldehyde and ethanol 

caused by propylene glycol dinitrate-induced depression of alcohol dehydrogenase and acetaldehyde 

dehydrogenase activities. 

2.7 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE 

A susceptible population will exhibit a different or enhanced response to Otto Fuel II and its 

components than will most persons exposed to the same level of Otto Fuel II and its components in 

the environment. Reasons include genetic make-up, developmental stage, health and nutritional status, 

and chemical exposure history. These parameters result in decreased function of the detoxification and 

excretory processes (mainly hepatic and renal) or the pre-existing compromised function of target 

organs. 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. 
OTTO FUEL II AND ITS COMPONENTS 94 

2. HEALTH EFFECTS
 

Review of the literature regarding toxic effects of Otto Fuel II or its components, propylene glycol 

dinitrate, 2-nitrodiphenylamine, and dibutyl sebacate, did not reveal any populations that are known to 

be unusually sensitive to these chemicals. However, based on the knowledge of the primary toxic 

effects of propylene glycol dinitrate, vasodilation and methemoglobin formation, a number of groups 

may be proposed as being potentially highly sensitive to this chemical. 

Groups that may be especially sensitive to the vasodilatory effects of propylene glycol dinitrate include 

those with arteriosclerotic or cardiac disease (Donovan 1990). In normal individuals, the vasodilation 

produced by propylene glycol dinitrate is compensated for by a reflex increase in arteriolar constriction 

and heart rate. Persons with arteriosclerosis have blood vessels with a limited ability to constrict 

reflexively. Persons with cardiac disease have a limited ability to enhance the mechanical performance 

of the heart. These groups may experience a greater degree of hypotension than normal individuals 

exposed to propylene glycol dinitrate. 

Individuals with asymptomatic, subclinical coronary heart disease (the majority of the U.S. adult 

population over age 50) who are chronically exposed to propylene glycol dinitrate vapor 

concentrations that exceed the industrial time-weighted average-threshold limit value (TWA-TLV) 

standards, and who develop a tolerance to this exposure, are at risk of experiencing angina pectoris 

and possible heart injury when the exposure is suddenly terminated, as could occur during a long 

weekend or vacation away from the job site. 

A number of populations may also experience greater sensitivity to the methemoglobinemia produced 

by propylene glycol dinitrate. For example, some groups may develop greater-than-normal levels of 

methemoglobin when exposed to propylene glycol dinitrate either as the result of the possession of a 

type of hemoglobin that is especially easily oxidized or resistant to reduction or as the result of 

decreased levels of enzymes or cofactors necessary for reduction of methemoglobin. Such persons 

include infants, persons with the hemoglobin variant, hemoglobin M, and those with congenital 

deficiencies in NADH-dependent methemoglobin reductase, the enzyme responsible for approximately 

95% of the reduction of methemoglobin to hemoglobin. Infants are at increased risk because (1) they 

possess fetal hemoglobin, which has a greater susceptibility to oxidation than adult hemoglobin, (2) 

they are deficient in methemoglobin reductase, and (3) they have low levels of erythrocyte NADH 

(Donovan 1990). Persons with hemoglobin M may have enhanced methemoglobin production because 
OTTO FUEL II AND ITS COMPONENTS 95 

2. HEALTH EFFECTS 

this type of hemoglobin is especially easily oxidized and is resistant to the reductive process (Donovan 

1990). 

The increase in methemoglobin produced by propylene glycol dinitrate may be compounded by the 

concurrent exposure of some groups to other chemicals that cause methemoglobin formation. For 

example, munitions workers may also be exposed to the methemoglobin-producing substances: 

ammonium nitrate, pentaerythritol tetranitrate, and erythrityl tetranitrate because of their use in 

explosives and pyrotechnics. Also, ingestion of inorganic nitrates (primarily in well water 

contaminated with nitrogenous fertilizers, animal waste, or seepage from septic tanks) has been shown 

to cause methemoglobin production. Also, several therapeutic agents such as bismuth subnitrate 

(antidiarrheal); ammonium nitrate (diuretic); nitroglycerin, isosorbide dinitrate,. sodium nitroprusside, 

pentaerythritol, and erythrityl tetranitrate (vasodilators); metoclopramide (antiemetic); prilocaine, 

benzocaine, and lidocaine (anesthetics); phenazopyridine (urinary tract analgesic); and dapsone, 

chloroquine, and primaquine (antimalarials) have been shown to increase methemoglobin levels. 

Abuse of organic nitrites (snappers, poppers) for their enhancement of erections and relaxation of the 

anal sphincter has also been associated with increased methemoglobin production. Also, accidental or 

intentional overdose of chlorate salts (found in toothpastes and throat soothants) may cause 

methemoglobinemia. Finally, exposure to aniline in inks, dyes, shoe polish, paints, varnishes, and 

gasoline additives has also been reported to induce elevated levels of methemoglobin (Donovan 1990). 

The increase in methemoglobin produced by propylene glycol dinitrate may .also be compounded by 

preexisting elevations of methemoglobin due to a medical condition. For example, pregnant women 

experience an elevation of methemoglobin during pregnancy. The level of methemoglobin peaks at 

approximately 10.5% at the 30th week of pregnancy and then declines to normal after delivery. Thus, 

women in the third trimester of pregnancy may be especially sensitive to the increases in 

methemoglobin produced by propylene glycol dinitrate 

Some groups may experience a greater level of tissue anoxia as the result of methemoglobin 

formation. These include persons with an impaired ability either to oxygenate blood (seen in those 

with compromised pulmonary function) or to deliver blood to the tissues (seen in those with impaired 

circulation). In addition, persons suffering from anemia have depressed numbers of red blood cells 

available to carry oxygen to the tissues (Donovan 1990). 
OTTO FUEL II AND ITS COMPONENTS 96 

2. HEALTH EFFECTS
 

Finally, some groups are resistant to the methemoglobin antidote, methylene blue (see also Section 

2.8). These include persons with congenitally low levels of NADPH-dependent methemoglobin 

reductase (the enzyme utilized for the reduction of methylene blue) and those with low glucose-6-

phosphate dehydrogenase activities (an enzyme necessary for NADPH production in red blood cells) 

(Donovan 1990). 

2.8 METHODS FOR REDUCING TOXIC EFFECTS 

This section will describe clinical practice and research concerning methods for reducing toxic effects 

of exposure to Otto Fuel II and its components. 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 Otto Fuel II and its components. When specific exposures have occurred, poison control 

centers and medical toxicologists should be consulted for medical advice. 

2.8.1 Reducing Peak Absorption Following Exposure 

Based on currently available information, the constituent of Otto Fuel II that presents the major health 

concern is propylene glycol dinitrate. Exposure to propylene glycol dinitrate occurs primarily by 

inhalation or through dermal absorption. In an acute exposure situation, general recommendations 

include removing the exposed person from the source of exposure. Dermal absorption may be reduced 

by removing contaminated clothing, blotting any excess liquid material on the skin with an absorbent 

material, and washing the skin with copious amounts of water and mild soap (Bronstein and Currance 

1988; Donovan 1990; Ellenhom and Barceloux 1988; Stutz and Janusz 1988). If the eyes have been 

contaminated, they may be flushed with water or normal saline (Bronstein and Currance 1988; Stutz 

and Janusz 1988). If ingestion of Otto Fuel II or propylene glycol dinitrate has occurred, absorption 

from the gastrointestinal tract may be limited by administering water or milk for dilution and activated 

charcoal to adsorb the material (Bronstein and Currance 1988; Donovan 1990; Ellenhom and 

Barceloux 1988; Stutz and Janusz 1988). The efficacy of gastric decontamination is optimal within 

2-4 hours after ingestion (Donovan 1990). 

2.8.2 Reducing Body Burden 

There are no known specific methods for reducing Otto Fuel II or its components body burden. 
OTTO FUEL II AND ITS COMPONENTS 97 

2. HEALTH EFFECTS 

2.8.3 Interfering with the Mechanism of Action for Toxic Effects 

The most commonly encountered symptom of overexposure to propylene glycol dinitrate (and Otto 

Fuel II) is headache due primarily to the vasodilation of cerebral vessels. Controlled human studies 

have demonstrated that the administration of 100% oxygen by mask, which produces a compensatory 

constriction of cerebral vessels, is efficacious (Stewart et al. 1974). Strong, black coffee with a high 

caffeine content, as well as aspirin, have proven helpful in alleviating head pain when there are no 

contraindications for the administration of either (Stewart et al. 1974). 

No agents are known to interfere with the ability of propylene glycol dinitrate to cause vasodilation or 

cyanosis (resulting from methemoglobin production), but procedures are available and have been 

recommended to counteract these effects. Hypotension may respond to intravenous fluids and 

Trendelenburg’s position, but vasopressors may be required (Donovan 1990; Ellenhorn and Barceloux 

1988). Cyanosis may be treated with high flow (100%) oxygen administration to saturate all 

remaining normal hemoglobin with, oxygen (ATSDR 1991; Donovan 1990; Ellenhom and Barceloux 

1988). Elevated levels of methemoglobin may be decreased by enhancing the rate of conversion of 

methemoglobin to hemoglobin. Methylene blue is the antidote of choice in this situation. Ascorbate 

has been suggested as an alternative reducing agent, but it is believed to have limited efficacy 

(Donovan 1990; Ellenhorn and Barceloux 1988). Methylene blue is administered intravenously. It is 

first reduced to leukomethylene blue by NADPH-dependent methemoglobin reductase in the red blood 

cell. The leukomethylene blue then acts as an electron donor to reduce methemoglobin to hemoglobin 

nonenzymatically. Use of methylene blue is generally indicated when methemoglobin levels exceed 

30% but may be used at lower methemoglobin levels in persons with pulmonary or cardiovascular 

disease or with preexisting anemia (Donovan 1990; Ellenhorn and Barceloux 1988; Goldfrank et al. 

1990). Methylene blue is ineffective in persons with glucose-6-phosphate dehydrogenase deficiency 

and of limited effectiveness in persons with NADPH-dependent methemoglobin reductase deficiencies 

(Donovan 1990; Ellenhom and Barceloux 1988; Goldfrank et al. 1990). Severe hemolytic anemia may 

develop if given to persons with glucose-6-phosphate dehydrogenase deficiency (ATSDR 1991). 

Caution should be also used when administering methylene blue to others because high doses 

(>7 mg/kg) may increase methemoglobin levels and cause hemolysis (Donovan 1990; Ellenhorn and 

Barceloux 1988). In cases of failure of methylene blue therapy, exchange transfusions have been used 

to replace hemoglobin and remove the absorbed toxin (Donovan 1990; Ellenhorn and Barceloux 1988). 
OTTO FUEL II AND ITS COMPONENTS 98 

2. HEALTH EFFECTS
 

Information on the effects of low-level chronic exposure to Otto Fuel II or its components is limited. 

No treatment strategies were located for minimizing the effects of chronic low-level exposures. 

2.9 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 Otto Fuel II and its components 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 Otto Fuel II and its 

components. 

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 or eliminate 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 may 

be proposed. 

2.9.1 Existing Information on Health Effects of Otto Fuel and Its Components 

The existing data on health effects of inhalation, oral, and dermal exposure of humans and animals to 

Otto Fuel II and its components are summarized in Figures 2-5 through 2-8. The purpose of these 

figures is to illustrate the existing information concerning the health effects of Otto Fuel II and its 

components. Each dot in the figure indicates that one or more studies provide information associated 

with that particular effect. The dot does not imply anything about the quality of the study or studies. 

Gaps in this figure should not be interpreted as “data needs.” A data need, as defined in ATSDR’s 

Decision Guide for Identifying Substance-Specific 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. 




OTTO FUEL II AND ITS COMPONENTS 103 

2. HEALTH EFFECTS
 

As can be seen in Figures 2-5 through 2-8, the information available on the health effects of Otto 

Fuel II and its individual components, propylene glycol dinitrate, 2-nitrodiphenylamine, and dibutyl 

sebacate, varies greatly depending on the specific substance under consideration. 

The only information available on the human health effects of Otto Fuel II comes from studies of 

torpedo maintenance workers and incinerator workers occupationally exposed to Otto Fuel II (ATSDR 

1990; Forman 1988; Forman et al. 1987; Horvath et al. 1981). Because occupational exposure could 

occur either as the result of inhalation of fumes arising from Otto Fuel II or as the result of dermal 

contact with Otto Fuel II, the information obtained in these studies is indicated as resulting from both 

inhalation and dermal exposures. One study in rats and rabbits has examined the developmental and 

maternal toxicity of dermal exposure to Otto Fuel II (Cooper et al. 1993). 

The information available on the health effects of propylene glycol dinitrate, the major component of 

Otto Fuel II, is the most comprehensive of all of the components reviewed. However, the information 

on this component is not complete. The human data are limited to a study in which volunteers were 

briefly exposed to propylene glycol dinitrate vapors volatilized from samples of Otto Fuel II (Stewart 

et al. 1974). The bulk of the animal data on propylene glycol dinitrate is from inhalation studies (Air 

Force 1985a; Jones et al. 1972; Mattsson et al. 1981). The only animal data resulting from oral 

exposure are the results of three acute oral toxicity (LD50) studies (Andersen and Mehl 1979; Clark 

and Litchfield 1969; Jones et al. 1972), and the only dermal data are from two single-dose toxicity 

studies (Clark and Litchfield 1969; Jones et al. 1972) and two 3-week studies (Andersen and Mehl 

1979; Jones et al. 1972). 

Very limited information is available on the toxicity of 2-nitrodiphenylamine. The only data located 

on this component of Otto Fuel II were obtained from a review article (Army 1979) and consisted of a 

summary of the results of an oral LD50 study, a dermal LD50 study, and eye and skin irritation studies 

in animals. (These results are included in the profile because they represent the only information 

located on 2-nitrodiphenylamine. Attempts are underway to try to obtain the studies upon which the 

reported results are based.) 

The information on the health effects of dibutyl sebacate is somewhat less comprehensive than the 

information on propylene glycol dinitrate. The human ,data are limited to two dermal irritation and 

skin sensitization studies (Askarova and Muryseva 1975; Mallette and Von Haam 1952b). The animal 
OTTO FUEL II AND ITS COMPONENTS 104 

2. HEALTH EFFECTS 

data come almost exclusively from oral studies (Komarova 1976, 1979; Smith 1953). The dermal data 

from animals consist of information obtained in two skin irritation and sensitization studies (Komarova 

1976, 1979; Mallette and Von Haam 1952b). Although the information available on dibutyl sebacate 

is limited, it indicates that this chemical is not very toxic by the oral or dermal routes and not 

expected to be toxic via other routes. 

2.9.2 Identification of Data Needs 

Acute-Duration Exposure. Populations in areas where Otto Fuel II is disposed of may be 

exposed to this substance for brief periods. Because of the limited volatility of two of the components 

of Otto Fuel II, 2-nitrodiphenylamine and dibutyl sebacate, inhalation exposures will be primarily to 

propylene glycol dinitrate. Insufficient information is available to eliminate any of the components of 

Otto Fuel II as possible water or soil contaminants, and thus, oral and dermal exposures to Otto Fuel II 

and its components must be considered. There are acute-duration inhalation exposure data in humans 

on Otto Fuel II and propylene glycol dinitrate from experimental exposure situations that indicate that 

the cardiovascular and nervous systems are target organs of these substances by the inhalation route 

(Horvath et al. 1981; Stewart et al. 1974). Headaches (most likely of cardiovascular origin) and 

impairment of coordination have been observed (Stewart et al. 1974). An acute-duration inhalation 

MRL for propylene glycol dinitrate was derived based on the NOAEL for visual evoked responses 

defined in this study. In addition, subclinical measures of nervous system activity and oculomotor 

function, have shown effects of low-level inhalation exposure to Otto Fuel II and propylene glycol 

dinitrate (Horvath et al. 1981; Stewart et al. 1974). No information was available regarding inhalation 

effects of 2-nitrodiphenylamine or dibutyl sebacate, but the chances for inhalation exposure to these 

substances is minimal due to their low volatility. No information was available on acute-duration oral 

exposure of humans to Otto Fuel II or any of its components. Acute-duration dermal exposure of 

humans to dibutyl sebacate indicated that this substance was not irritating to the skin (Mallette and 

Von Haam 1952b). Acute-duration occupational exposure to Otto Fuel II, consisting of mixed 

inhalation and dermal exposures, caused changes in subclinical neurologic parameters (Horvath et al. 

1981). However, no information was located on dermal exposure to propylene glycol dinitrate or 

2-nitrodiphenylamine. 

Acute-duration studies of animals (rats, dogs, and, monkeys) exposed to propylene glycol dinitrate by 

inhalation support the identification of the neurological and cardiovascular systems as target organs of 
OTTO FUEL II AND ITS COMPONENTS 105 

2. HEALTH EFFECTS 

this substance by the inhalation route and indicate that the hematological system is also a target of 

propylene glycol dinitrate-induced toxicity (Air Force 1985a; Jones et al. 1972; Mattsson et al. 1981). 

In addition to causing altered neuronal activity and convulsions (Jones et al. 1972; Mattsson et al. 

198 1) and effects attributable to vasodilation (Jones et al. 1972), increased levels of methemoglobin 

and decreased hemoglobin and hematocrit were observed after acute-duration inhalation exposure to 

propylene glycol dinitrate (Air Force 1985a; Jones et al. 1972). Acute-duration studies in rats exposed 

to propylene glycol dinitrate, 2-nitrodiphenylamine, or dibutyl sebacate by the oral route are limited to 

those with death as the end point (Andersen and Mehl 1979; Army 1979; Clark and Litchfield 1969; 

Jones et al. 1972; Smith 1953). Because death was the only end point examined in these studies, 

insufficient information was available to calculate an acute-duration oral MRL. An acute-duration 

study in rats and rabbits showed that high concentrations of this substance may produce moderate-to-marked skin 

irritation, methemoglobinemia, and fetal toxicity (Cooper et al. 1993). Acute-duration 

studies in rats or rabbits exposed to propylene glycol dinitrate, 2-nitrodiphenylamine, or dibutyl 

sebacate by the dermal route indicate that these substances are practically nonirritating to the skin and 

cause limited eye irritation (Army 1979; Jones et al. 1972; Komarova 1976, 1979; Mallette and Von 

Haam 1952b). Acute-duration dermal exposure of rats or rabbits to propylene glycol dinitrate also 

demonstrates the susceptibility of the cardiovascular system to this chemical (Clark and Litchfield 

1969; Jones et al. 1972). There are limited pharmacokinetics data regarding propylene glycol dinitrate; 

however, the data that were obtained do not indicate that route-specific target organs exist. 

Pharmacokinetics dka were extremely limited regarding dibutyl sebacate and 2-nitrodiphenylamine. 

Thus, it is difficult to speculate on whether similar target organs would be affected across the various 

potential routes of exposure. 

The physical properties of 2-nitrodiphenylamine and dibutyl sebacate do not indicate that inhalation 

exposure to these substances in the environment is likely. Thus, additional studies examining the 

effects of acute-duration inhalation exposure to these chemicals are not necessary. Also, lethality 

studies in rats indicate that oral exposure to 2-nitrodiphenylamine and dibutyl sebacate at levels likely 

to be encountered in the environment are relatively innocuous. Thus, additional acute-duration studies 

designed to evaluate the target organs affected by these chemicals do not appear to be necessary. 

However, additional studies examining the effects of acute-duration oral exposure to propylene glycol 

dinitrate may be valuable for defining levels of exposure associated with toxicity thresholds. In 

addition, a study examining the oral and dermal toxicity of the mixture Otto Fuel II would be helpful 

in eliminating the possibility of synergistic toxic effects of the components. Although the components 
OTTO FUEL II AND ITS COMPONENTS 106 

2. HEALTH EFFECTS 

of Otto Fuel II do not appear to cause appreciable dermal or ocular toxicity, additional studies 

examining the acute-duration dermal toxicity of Otto Fuel II and its components on other target organs 

would provide valuable information. 

Intermediate-Duration Exposure. No studies were located regarding the effects of intermediate-duration 

exposure to Otto Fuel II or its components in humans by the inhalation, oral, or dermal 

routes. No studies were located regarding the effects of intermediate-duration exposure to Otto Fuel II 

in animals by the inhalation, oral, or dermal routes. Intermediate-duration inhalation exposure studies 

are limited to studies examining the effects of propylene glycol dinitrate in rats, dogs, monkeys, and 

guinea pigs (Air Force 1985a; Jones et al. 1972; Mattsson et al. 1981). These studies indicate that the 

blood, liver, and kidneys are target organs of such exposures. In these studies, effects on the blood 

(elevated methemoglobin and hemolysis of red blood cells) were observed at lower concentrations than 

effects on the liver or kidneys. An intermediate-duration inhalation MRL was derived for propylene 

glycol dinitrate based on the observation of elevated methemoglobin and decreased hematocrit, 

hemoglobin, red blood cells, and reticulocytes in dogs (Air Force 1985a). No intermediate-duration 

oral studies were located in which animals were exposed to propylene glycol dinitrate, 

2-nitrodiphenylamine, or dibutyl sebacate. Therefore, no intermediate-duration oral MRL was derived. 

Additional animal studies examining the effects of intermediate-duration exposure to dibutyl sebacate 

do not seem warranted at this time since chronic-duration studies showed the substance to be relatively 

nontoxic (Smith 1953). However, additional studies examining the effects of intermediate-duration 

oral exposure to propylene glycol dinitrate, 2-nitrodiphenylamine, and Otto Fuel II would be helpful 

because of the possibility of oral exposures to these substances. The only intermediate-duration 

dermal exposure study that was located examined the effects of propylene glycol dinitrate in the rabbit 

(Jones et al. 1972). This study showed the adverse effects of this chemical on the blood, liver, heart, 

skin, urinary tract, and possibly the respiratory system. These effects, however, were evident after 

only a few applications of the chemical; therefore, the study is better categorized as an acute-duration 

study. Although the effects were produced at relatively high doses, an additional study more clearly 

delineating the doses associated with the histopathological changes would be helpful. In view of the 

relatively low chronic-duration toxicity of dibutyl sebacate by the oral route (Smith 1953), additional 

intermediate-duration studies examining the dermal toxicity of this chemical would not appear to be 

valuable. However, very little is known regarding the effects of 2-nitrodiphenylamine by the 

inhalation, oral, and dermal routes of exposure, so studies examining its intermediate-duration toxicity 

would be helpful. 
OTTO FUEL II AND ITS COMPONENTS 107 

2. HEALTH EFFECTS 

Chronic-Duration Exposure and Cancer. Only a few studies have examined the effects of 

chronic-duration occupational exposure to Otto Fuel II in humans (ATSDR 1990; Forman et al. 1987; 

Horvath et al. 1981). In these studies, exposures were not quantified and may have been by the 

inhalation, dermal, or combined inhalation and dermal routes. These studies have examined the effects 

of such exposures on the likelihood of angina and myocardial infarctions (Forman et al. 1987), the 

incidence of abortions among exposed female personnel (Forman 1988), and performance on tests of 

coordination and balance and oculomotor function (Horvath et al. 1981). The study examining 

myocardial parameters was the only study demonstrating an exposure-related effect (Forman et al. 

1987). However, the other two studies were limited by the small numbers of subjects examined, and 

in the ATSDR study, workers were exposed to other hazardous substances. No studies were located 

regarding chronic-duration exposures of humans to any of the individual components of Otto Fuel II. 

Chronic-duration studies in animals are likewise limited in number. The only chronic-duration studies 

in animals that were located were an inhalation exposure study of the effects of propylene glycol 

dinitrate in rats, mice, and dogs (Air Force 1985a) and an oral exposure study of the effects of dibutyl 

sebacate in rats (Smith 1953). Propylene glycol dinitrate exposure resulted in an increase in 

methemoglobin and decrease in hematocrit, hemoglobin, red blood cells, and reticulocytes in dogs and 

possibly an increase in mild degeneration of the nasal epithehum of rats at the lowest dose tested (Air 

Force 1985a). A chronic-duration inhalation MRL for propylene glycol dinitrate was derived from this 

study based on hematological effects which were observed within several weeks in dogs and continued 

through 14 months of exposure. No studies were available regarding the effects of chronic-duration 

oral or dermal exposure to propylene glycol dinitrate in animals. No chronic-duration oral MRL value 

was derived because of the absence of information on the effects of propylene glycol dinitrate after 

oral exposure. Studies examining the chronic oral and dermal effects of propylene glycol dinitrate 

may provide valuable information regarding toxicity thresholds for persons exposed to propylene 

glycol dinitrate by these routes over an extended period. The absence of toxicokinetic data limits 

cross-route extrapolation of exposure levels and effects. In addition, a study examining the incidence 

of anemia or methemoglobin concentration in human populations exposed to propylene glycol dinitrate 

occupationally may also provide useful information. Long-term consumption of high levels of dibutyl 

sebacate resulted in no adverse effects in rats (Smith 1953). The absence of toxic effects in animals 

after oral exposure indicates that chronic dermal exposure studies and epidemiological studies in 

exposed human populations may not be needed. Based on the absence of information on the effects of 

chronic-duration oral or dermal exposure to 2-nitrodiphenylamine in humans or animals, studies 

examining the effects of such exposures in animals would be valuable. Pending the results of the 
OTTO FUEL II AND ITS COMPONENTS 108 

2. HEALTH EFFECTS 

animal study, an investigation of the effects of chronic exposure of humans to 2-nitrodiphenylamine 

may be desirable. 

No information was located regarding the carcinogenic potential of Otto Fuel II or its components in 

humans. The only animal study that examined the oncogenicity of any of the components of Otto 

Fuel II was a chronic-duration inhalation study of propylene glycol dinitrate exposure in rats and mice 

(Air Force 1985a). While this study did not demonstrate a marked carcinogenic response in rats or 

mice to propylene glycol dinitrate, rare tumors (osteoma and osteosarcoma) were observed in the rats, 

and an increased incidence of a preneoplastic lesion (lymphoid hyperplasia) was observed in the mice. 

These results are suggestive of a carcinogenic effect, and additional studies examining the carcinogenic 

potential following inhalation exposure to propylene glycol dinitrate may be necessary to resolve the 

issue. The duration of the additional studies should be extended to cover the entire lifetime of the 

species selected, since the Air Force study (1985a) examined the effects of 1-year exposures. True 

lifetime exposures may reveal more subtle effects. A chronic-duration oral study in rats reported no 

increase in tumors among animals consuming large amounts of dibutyl sebacate, but the number of 

animals tested may have been too small to adequately test the carcinogenic potential of this compound. 

Additional studies examining cancer incidence in human populations chronically exposed to Otto Fuel 

II or its components and animal studies examining the carcinogenic potential of Otto Fuel II and all 

three of its components by the oral and dermal routes may provide additional valuable information. 

Genotoxicity. Negative results were obtained from well-conducted microbial gene mutation assays 

(in Salmonella typhimurium and Saccharomyces cerevisiae) (Navy 1982b). Findings from mammalian 

cell assays indicated that Otto Fuel II increased the frequency of forward mutations but not sister 

chromatid exchange in mouse lymphoma cells (Navy 1982b). No in vitro cytogenetic studies were 

found. It is doubtful, however, that a clastogenic response would be uncovered in cultured mammalian 

cells since Otto Fuel II up to cytotoxic doses did not induce a genotoxic response or cause cell cycle 

delay on the sister chromatid exchange assay. Because sister chromatid exchange induction frequently 

occurs at much lower doses than are required to produce chromosome aberrations, it is reasonable to 

assume that the cytotoxic activity of Otto Fuel II would preclude the assessment of higher 

concentrations for potential adverse effects on chromosome morphology. Nevertheless, well-conducted 

in vivo studies assessing potential clastogenic activity are needed to complete the genetic toxicology 

profile for Otto Fuel II. The single positive mammalian cell gene mutation assay should be confirmed 

either in the same or a different cell line. Since no valid data were found for the constituents of Otto 
OTTO FUEL II AND ITS COMPONENTS 109 

2. HEALTH EFFECTS
 

Fuel II, a full battery of in vitro and in viva tests evaluating the major genetic end points is required. 

These include gene mutation in microbial and mammalian cells, chromosome aberrations in vitro and 

in vivo, and other mutagenic mechanisms, such as sister chromatid exchange induction in mammalian 

cells and unscheduled DNA synthesis in primary hepatocytes. 

Reproductive Toxicity. One study compared the incidence of spontaneous and induced abortions 

among female Navy personnel who had occupational exposure to Otto Fuel II with two groups of 

enlisted females who were not exposed to Otto Fuel II (Forman 1988). Although no increase in the 

incidence of abortions was observed, the number of women in the exposed group was only five. This 

severely limits the sensitivity of the comparison. No other studies were located that examined the 

reproductive effects in humans of exposure to Otto Fuel II or any of its components by the inhalation, 

oral, or dermal routes of exposure. A single study in laboratory animals has directly examined the 

reproductive effects of oral exposure to dibutyl sebacate (Smith 1953). This study showed no effect 

on fertility, litter size, or litter survival of exposed rats. A single dominant lethal study in mice was 

conducted examining the effects of oral exposure to Otto Fuel II (Navy 1982b); however, no 

conclusions could be drawn from the fertility phase of the assay because the lower than expected 

fertility indices in the historic and concurrent negative controls limited the evaluation of reduced 

fertility in the treatment groups at the majority of mating intervals. No other study has directly 

examined reproductive function following exposure to Otto Fuel II or any of its components by the 

inhalation, oral, or dermal route. Routine gross and histopathological examination of reproductive 

organs (seminal vesicles, prostate, testes, ovaries, uterus, and mammary glands) of mice, rats, and dogs 

revealed no adverse effects on these tissues following chronic inhalation exposure to propylene glycol 

dinitrate (Air Force 1985a). Although the oral study using dibutyl sebacate (Smith 1953) indicates that 

this component of Otto Fuel II has limited reproductive toxicity, other studies examining reproductive 

function would be helpful. A continuation of the epidemiological study described by Forman (1988) 

in which the number of exposed female personnel is increased would be useful because this population 

is expected to have the greatest exposure to Otto Fuel II. In addition, studies in animals examining the 

reproductive function of inhalation, oral, and dermal exposures to Otto Fuel II or its component 

propylene glycol dinitrate and of oral and dermal exposure to 2-nitrodiphenylamine are needed to 

provide information on the possible reproductive effects experienced by persons with these types of 

exposure to Otto Fuel II at hazardous waste sites. 
OTTO FUEL II AND ITS COMPONENTS 110 

2. HEALTH EFFECTS 

Developmental Toxicity. No studies in humans have examined the developmental effects of 

exposure to Otto Fuel II or any of its components. The only information from studies in animals 

regarding developmental effects has come from a study examining the developmental toxicity of 

dermal exposure to Otto Fuel II in rats and rabbits (Cooper et al. 1993) and the reproductive toxicity 

of oral exposure to dibutyl sebacate in rats (Smith 1953). The dermal Otto Fuel II study suggested 

that, at maternally toxic doses, developmental toxicity may occur. The study on dibutyl sebacate 

indicated that this component of Otto Fuel II had only minor adverse effects on the weight gain of 

offspring of parents that had been fed diets containing dibutyl sebacate. Thus, it is likely that dibutyl 

sebacate did not account for the developmental toxicity of Otto Fuel II. Studies examining the 

developmental effects of inhalation and oral exposure of animals to Otto Fuel II, inhalation, oral, and 

dermal exposure to its component propylene glycol dinitrate, and of oral and dermal exposure of 

animals to 2-nitrodiphenylamine could provide information on the possible developmental effects 

experienced by persons with these types of exposure to Otto Fuel II at hazardous waste sites. In 

addition, as the number of women in the military increases and occupational exposure to Otto Fuel II 

among females becomes more widespread, studies examining the development of their children could 

provide information on such effects in a population with known exposure. 

Immunotoxicity. Extremely limited information is available on immune function in humans and 

animals after inhalation, oral, or dermal exposure to Otto Fuel II or any of its components. A skin 

sensitization, study in humans and rabbits examined the dermal sensitization potential of dibutyl 

sebacate and found no sensitization 2 weeks following a 2-day dermal exposure (Mallette and Von 

Haam 1952b). In addition, infrequent observation of sensitization to dibutyl sebacate was reported in 

a study examining the responses of occupationally exposed workers to dibutyl sebacate challenges 

(Askarova and Muryseva 1975). No other studies examined immune function in humans or animals 

after inhalation, oral, or dermal exposure to Otto Fuel II or any of its components. Only indirect 

information regarding the status of the immune system was obtained in animal studies. Results of 

hematological tests indicated no effect of chronic-duration inhalation or intermediate-duration dermal 

exposure to propylene glycol dinitrate on total or differential leukocyte counts in rats, dogs, and 

rabbits (Air Force 1985a; Jones et al. 1972). In addition, the lymph nodes, thymuses and/or spleens of 

animals in these studies were normal at necropsy. Similarly, no histopathologic alterations were 

observed in the spleen of rats and guinea pigs in an intermediate-duration inhalation study (Jones et al. 

1972) or in the spleen of rats in a chronic-duration oral study (Smith 1953). Because little is known 

about the effects of Otto Fuel II or its components on the immune system, studies in animals 
OTTO FUEL II AND ITS COMPONENTS 111 

2. HEALTH EFFECTS
 

examining immune function following inhalation, oral, and dermal exposures to Otto Fuel II or its 

component propylene glycol dinitrate and following oral or dermal exposure to the components 

2-nitrodiphenylamine and dibutyl sebacate would be informative. 

Neurotoxicity. Short-term exposure of humans to Otto Fuel II during torpedo maintenance 

procedures (30-45 minutes per turnaround) and brief experimental inhalation exposures (1-8 hours) to 

propylene glycol dinitrate at low levels have been shown to cause subclinical alterations in central 

nervous system activity (Horvath et al. 1981; Stewart et al. 1974). At higher concentrations, tests of 

coordination were affected, and subjects reported feeling dizzy (Stewart et al. 1974). No studies were 

located that examined the neurological effects of either 2-nitrodiphenylamine or dibutyl sebacate in 

humans after exposure by the inhalation, oral, or dermal route. Studies in monkeys have demonstrated 

central nervous system effects of propylene glycol dinitrate following inhalation exposure only at 

concentrations higher than those used in the human studies (Jones et al. 1972; Mattsson et al. 1981). 

In oral and dermal exposure studies, nervous system effects have also been observed in rats and 

rabbits following administration of large doses of propylene glycol dinitrate (Jones et al. 1972). No 

information was located on the nervous system effects of 2-nitrodiphenylamine in animals following 

exposure by the inhalation, oral, or dermal route. The only data located on the possible effects of 

dibutyl sebacate on the nervous system come from a chronic-duration oral study in rats in which gross 

and histopathological examination of selected nervous system tissues revealed no abnormalities (Smith 

1953). Although humans appear to be more sensitive to the neurological effects of propylene glycol 

dinitrate than animals, continued studies in animals directed toward elucidating a possible mechanism 

of action for the effects of propylene glycol dinitrate would be useful. In addition, studies in animals 

directly examining the effects of 2-nitrodiphenylamine and dibutyl sebacate on neuronal function 

following oral and dermal exposures could provide information on the potential for effects of these 

components on the nervous system from exposures at hazardous waste sites. 

Epidemiological and Human Dosimetry Studies. Very few epidemiological studies examining 

the effects of Otto Fuel II were located (Forman 1988; Forman et al. 1987; Horvath et al. 1981). 

Exposure to Otto Fuel II is known to occur in only a very small segment of the population, namely 

those persons with exposure to torpedo engines and propellants. Thus, collecting sufficient numbers of 

exposed persons for meaningful epidemiological studies is difficult. However, because the population 

most likely to be exposed consists mainly of enlisted personnel, follow-up studies may be more easily 

performed. Thus, additional studies examining immunological, developmental, reproductive, 
OTTO FUEL II AND ITS COMPONENTS 112 

2. HEALTH EFFECTS
 

oncogenic, and long-term neurological effects would be valuable if a sufficient number of exposed 

persons are identified. 

Biomarkers of Exposure and Effect. 

Exposure. Methods are available for the analysis of propylene glycol dinitrate or its metabolites in 

expired air, blood, and urine (see Table 6-1). Although measurement of urinary nitrates has been used 

to indicate exposure to propylene glycol dinitrate, this method is limited by the rapid formation of 

nitrates in the blood, their rapid excretion, and the large number of other chemicals causing elevated 

urinary nitrates (Clark and Litchfield 1969; Donovan 1990). A method is available for the analysis of 

2-nitrodiphenylamine in hand swabs (Bratin et al. 1981). Procedures for measuring dibutyl sebacate in 

body tissues or excreta were not found. The rapid hydrolysis of dibutyl sebacate to common organic 

molecules limits the utilization of measurement of either the parent compound or its metabolites as 

biomarkers of exposure. Studies delineating the metabolism and excretion of 2-nitrodiphenylamine 

may suggest potential biomarkers for exposure to this chemical and to Otto Fuel II. 

Effect. The effects produced by Otto Fuel II and its components include vasodilation, headache (most 

likely the result of meningeal vessel dilation), dizziness, and methemoglobin formation. No 

biomarkers were identified for meningeal vessel dilation or the resulting headaches. Also, monitoring 

blood pressure as a method for detecting vasodilation may be of limited usefulness because of the 

ability of normal healthy individuals to compensate for venous dilation with an increase in arteriolar 

constriction and elevation of heart rate (Air Force 1982b). Methods for spectrophotometrically 

measuring methemoglobin content of the blood are well defined, and methods for distinguishing 

cyanosis caused by events other than methemoglobinemia have been identified (Donovan 1990). 

Neurophysiological parameters such as those assessed by Stewart et al. (1974) and Horvath et al. 

(1981) are commonly used to monitor for subclinical neurological effects; however, neither of these 

methods can distinguish propylene glycol dinitrate-induced changes from changes in brain activity due 

to several other causes. As understanding grows regarding the fundamental mechanism by which Otto 

Fuel II and propylene glycol dinitrate affect neuronal function, tests may be developed to monitor for 

the underlying neurological changes caused by these substances. 

Absorption, Distribution, Metabolism, and Excretion. The only information regarding the 

absorption of Otto Fuel II or its individual components in humans comes from an inhalation exposure 
OTTO FUEL II AND ITS COMPONENTS 113 

2. HEALTH EFFECTS
 

study in which detectable levels of propylene glycol dinitrate were found in the blood of exposed 

subjects (Stewart et al. 1974). Inhalation exposure of animals to propylene glycol dinitrate has also 

been demonstrated to result in detectable levels of this substance in the blood (Mattsson et al. 1981). 

Absorption of all three of the components of Otto Fuel II by the oral route has been indicated by the 

ability of each of these substances to cause death or systemic toxicity when administered by this route 

(Andersen and Mehl 1979; Army 1979; Clark and Litchfield 1969; Jones et al. 1972; Smith 1953). 

Also, dermal absorption of propylene glycol dinitrate has been inferred by the observation of effects 

on blood pressure after dermal application of this substance (Clark and Litchfield 1969; Godin et al. 

1993). True quantitative data on the absorption of propylene glycol dinitrate and dibutyl sebacate 

following administration by the various routes of exposure may be difficult to obtain because of the 

rapid metabolism of these substances (Clark and Litchfield 1969; Kylin et al. 1966; Smith 1953). 

However, information on the relative absorption by the three routes of exposure for propylene glycol 

dinitrate and by oral and dermal absorption of dibutyl sebacate would be helpful for estimating 

absorption in humans and clarifying dose limits, and would relate to the practical use of protective 

clothing. In addition, studies in animals examining absorption of 2-nitrodiphenylamine by the oral and 

dermal routes of exposure could serve as a basis for estimates of the absorption of this substance by 

humans. 

No information was available on the distribution of 2-nitrodiphenylamine or dibutyl sebacate in either 

humans or animals following exposure by the inhalation, oral, or dermal route. The only information 

located on the distribution of propylene glycol dinitrate consists of the observation of this substance in 

the blood of humans and monkeys that were been exposed by inhalation (Mattsson et al. 1981; Stewart 

et al. 1974). Therefore, inhalation studies examining the distribution of propylene glycol dinitrate and 

oral and dermal studies examining the distribution of all three components of Otto Fuel II could 

provide useful information. 

The metabolism of propylene glycol dinitrate and dibutyl sebacate has been studied almost exclusively 

in in vitro studies and/or after parenteral administration (Clark and Litchfield 1969; Godin et al. 1994; 

Smith 1953). However, the metabolic products of propylene glycol dinitrate have been identified only 

through the initial steps of metabolism, and the metabolic products of dibutyl sebacate have not been 

reported. Thus, studies providing the missing information on metabolic products of these chemicals 

would be useful. No studies were located regarding the metabolism of 2-nitrodiphenylamine. 

Therefore, studies designed to identify the metabolic products of 2-nitrodiphenylamine would be 
OTTO FUEL II AND ITS COMPONENTS 114 

2. HEALTH EFFECTS
 

valuable. Also, studies examining the metabolism of the three components of Otto Fuel II after 

exposure by the three routes might provide information on the effects of the route of exposure on the 

relative metabolic rates. Studies designed to identify sex- and species-related differences in 

metabolism would also be valuable. 

The excretion of propylene glycol dinitrate in expired air following inhalation exposure has been 

examined in humans (Stewart et al. 1974). However, outdated methods were used in this study, and 

no other information on the excretion of propylene glycol dinitrate by humans was located. In 

addition, urinary excretion of metabolic products of propylene glycol dinitrate after dermal and 

parenteral administration has been studied in animals (Air Force 1982b; Clark and Litchfield 1969; 

Jones et al. 1972). However, no study has examined combined expired air, urine, and fecal excretion 

of propylene glycol dinitrate following exposure by the inhalation, oral, or dermal route. Also, no 

information exists on excretion of dibutyl sebacate or 2-nitrodiphenylamine from humans or animals 

after exposure by the inhalation, oral, or dermal route. Thus, studies examining excretion of these 

substances and their metabolic products following exposure by at least one route would provide useful 

information on excretory patterns. Studies examining excretion following exposure by more than one 

route could provide information on possible differences in excretion with varying routes of exposure. 

Studies on sex- and species-related differences in excretion would also be useful. 

Comparative Toxicokinetics. Data are available that suggest that species differences exist with 

regard to the doses of propylene glycol dinitrate necessary to cause hematological effects (e.g., dogs 

versus rats) (Air Force 1985a) and neurological effects (e.g., monkeys versus humans) (Mattsson et al. 

1981; Stewart et al. 1974). However, the information available on the toxicokinetics of propylene 

glycol dinitrate in various species is insufficient to speculate on whether the differences are due to 

variations in toxicokinetic parameters or differences in target organ sensitivities (Wyman et al. 1985). 

Additional studies examining the absorption, distribution, metabolism, and excretion of propylene 

glycol dinitrate in the affected species (i.e., following inhalation exposure) may be necessary before 

such conclusions can be reached. 

No data are available on the toxicokinetics of 2-nitrodiphenylamine, and virtually no data are available 

on the toxicokinetics of dibutyl sebacate. Studies examining the absorption, distribution, metabolism, 

and excretion of these chemicals in several species are necessary before comparative evaluations based 

on toxicokinetic differences can be performed. 
OTTO FUEL II AND ITS COMPONENTS 115 

2. HEALTH EFFECTS
 

Methods for Reducing Toxic Effects. There are good data regarding steps that may be taken to 

reduce methemoglobin levels and therapeutic measures that may counteract the effects resulting from 

vasodilation produced by propylene glycol dinitrate. However, additional studies on methods to 

enhance the breakdown of propylene glycol dinitrate in the blood or to block its effects on vascular 

smooth muscle would be valuable. No information was located for dealing with toxic effects 

associated with long-term low-level exposures to Otto Fuel II or its components. Studies examining 

possible means of preventing coronary vasospasm upon termination of long-term exposures to Otto 

Fuel II or its major component propylene glycol dinitrate would be helpful. Also, studies assessing 

appropriate protective equipment (i.e., clothing) and safe methods for handling Otto Fuel II and its 

components would be helpful. 

2.9.3 Ongoing Studies 

No ongoing studies evaluating either the health effects or toxicokinetics of propylene glycol dinitrate, 

2-nitrodiphenylamine, or dibutyl sebacate, were located. However, ATSDR is conducting a study in 

Lenoir, North Carolina to evaluate the prevalence of specific diseases and symptoms of a population 

living within a IS-mile radius of a hazardous waste incinerator where Otto Fuel II was being burned 

(ATSDR 1992). 

OTTO FUEL II AND ITS COMPONENTS 117 

3. CHEMICAL AND PHYSICAL INFORMATION 

3.1 CHEMICAL IDENTITY
 

Information regarding the chemical identity of Otto Fuel II and its components is located in Table 3-1.
 

3.2 PHYSICAL AND CHEMICAL PROPERTIES
 

Information regarding the physical and chemical properties of Otto Fuel II and its components is 

located in Table 3-2. 



OTTO FUEL II AND ITS COMPONENTS 121 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 

4.1 PRODUCTION 

Named after its inventor, Otto Reitlinger (Forman 1988), Otto Fuel II consists of the nitrated ester 

explosive propellant propylene glycol dinitrate (PGDN), to which a desensitizer (dibutyl sebacate) and 

a stabilizer (2-nitrodiphenylamine) have been added (Kessick et al. 1978; Rivera 1974). The chief 

component, propylene glycol dinitrate, accounts for approximately 75% of the mixture, while dibutyl 

sebacate and 2-nitrodiphenylamine account for approximately 23% and 2%, respectively (Air Force 

1985a; Kessick et al. 1978). Wilshire Chemical Co., Inc., of Gardena, California, is the only 

manufacturer or distributor of propylene glycol dinitrate that was located, and production volumes for 

this facility were not available (Van and Deyrup 1991). Information on the manufacture of Otto Fuel 

II was not located. Since Otto Fuel II releases are not required to be reported under SARA Section 

313, there are no data on Otto Fuel II in the 1994 Toxic Release Inventory. 

2-Nitrodiphenylamine is produced by the reaction of 2-chloronitrobenzene and aniline in the presence 

of sodium carbonate (Army 1979). A yield of 96% is obtained by removing water in the form of its 

aniline azeotrope. As of 1978, the only U.S. manufacturer was American Cyanamid Company. There 

were at least four foreign manufacturers, including Bayer AG in Germany, as well as Hickson & 

Welch Ltd., Hopkin & Williams, and Koch-Light Laboratories Ltd. in the United Kingdom. Radford 

Army Ammunition Plant was the only Army ammunition plant employing 2-nitrodiphenylamine at that 

time. Current domestic producers of 2nitrodiphenylamine include the Aceto Corporation of Lake 

Success, New York, and Schweizerhall, Inc., of Piscataway, New Jersey (Van and Deyrup 1991). 

Production volume data, including data on the amounts used by the US. Navy in Otto Fuel II, were 

not located. 

Dibutyl sebacate can be synthesized by at least three methods: (1) reaction of sebacic acid and butanol 

in the presence of an appropriate esterification catalyst; (2) distillation of sebacic acid with butyl 

alcohol in the presence of concentrated hydrochloric acid in a benzene solution; and (3) reaction of 

butyl alcohol with sebacyl chloride (HSDB 1994). Current manufacturers of dibutyl sebacate and their 

production sites include Eastech Chemical Inc., Philadelphia, Pennsylvania; Merrand International 

Corporation, Stow, Ohio; Ivanhoe Industries, Inc., Pennington, New Jersey; Bayer USA Inc., Carteret, 

New Jersey; Union Camp Corp., Chicago, Illinois; The C.P. Hall Company, Dover, Ohio; and Hatco 
OTTO FUEL II AND ITS COMPONENTS 122 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL
 

Chemical Corporation, Fords, New Jersey (SRI 1991; Thomas Publishing 1990a; Van and Deyrup 

1991). U.S. production volumes in 1972 totaled 2.04 million kilograms. The volume increased 

slightly to 2.54 million kilograms by 1975, although this included 2-ethylhexyl sebacate as well 

(HSDB 1994). More current production data could not be located. 

4.2 IMPORT/EXPORT 

Import and export data for Otto Fuel II and its three components could not be located. 

4.3 USE 

Otto Fuel II is a liquid monopropellant (it does not require an atmosphere containing oxygen to 

support combustion) used by the U.S. Navy in MK-46 and MK-48 torpedoes (Rivera 1974) and other 

weapons systems (Air Force 1985a). 

The principal current use of propylene glycol dinitrate is as a propellant in Otto Fuel II (Forman 

1988). Nitrates of polyhydric alcohols, of which propylene glycol dinitrate is an example, have been 

used in medicine for the treatment of angina pectoris, and as explosives since the mid-nineteenth 

century (Litchfield 1971). 

In addition to its use by the U.S. Navy as a stabilizer in the manufacture of Otto Fuel II, 

2-nitrodiphenylamine is employed for similar purposes by the U.S. Army in the manufacture of double 

base solid propellants (Army 1979). It also has civilian applications as a solvent dye (Army 1979; 

Baughman and Perenich 1988). 

Dibutyl sebacate is a desensitizer in Otto Fuel II. However, its major use is as a plasticizer for 

cellulose acetate butyrate plastics, cellulose acetate propionate plastics, polyvinyl butyral plastics, 

polystyrene, and many synthetic rubbers (HSDB 1994). Many of the plastic products containing 

dibutyl sebacate are used in the food packaging industry. Dibutyl sebacate is also used as a 

lubricating ingredient in shaving lotions, and as a synthetic flavoring additive in non-alcoholic 

beverages, ice cream, ices, candy, and baked goods. 
OTTO FUEL II AND ITS COMPONENTS 123 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 

4.4 DISPOSAL 

The available information on the disposal of Otto Fuel II and propylene glycol dinitrate is limited. 

Most of the available information comes from laboratory-scale and pilot pl,ant studies of potential 

treatment methods conducted in the 1970s and early 1980s. Biodegradation studies have provided 

conflicting evidence of the biodegradability of propylene glycol dinitrate (the major component of Otto 

Fuel II) by conventional sewage treatment methods (Army l98la, 1981b: Kessick et al. 1978; Wyman 

et al. 1984). Suggested alternative treatment methods have included carbon absorption techniques 

combined with base hydrolysis of propylene glycol dinitrate to the biodegradable propylene glycol 

(Kessick et al. 1978), and decomposition of propylene glycol dinitrate using sodium sulfide (Smith et 

al. 1983). Bench-scale wet air oxidation screening tests conducted at 280 °C for 60 minutes indicate 

excellent removal of propylene glycol dinitrate from waste streams that are too dilute to incinerate and 

too toxic to biotreat (Dietrich et al. 1985). 

2-Nitrodiphenylamine is only sparingly soluble in water, and thus it can be recovered as a solid in 

effluent stream filters (Army 1979). At the Radford Army Ammunition Plant in Radford, Virginia, it 

was estimated that one-half to two-thirds of the 2-nitrodiphenylamine that is lost during preparation 

and processing operations is recovered in this manner. 

No information on the disposal or treatment of dibutyl sebacate was located. 

OTTO FUEL II AND ITS COMPONENTS 125 

5. POTENTIAL FOR HUMAN EXPOSURE 

5.1 OVERVIEW 

Otto Fuel II is a mixture of three component chemicals, propylene glycol dinitrate, 

2-nitrodiphenylamine, and dibutyl sebacate. Otto Fuel II enters the environment as these three 

components, which partition to the different environmental media according to their individual 

chemical and physical properties. Otto Fuel II is primarily released to water in waste streams from 

Navy facilities that produce it or are involved in torpedo rework operations. There is also a possibility 

that it could be spilled on soil during transfer operations. The limited data located on the 

environmental fate of Otto Fuel II components indicate that propylene glycol dinitrate is removed from 

water primarily by volatilization. Propylene glycol dinitrate is the most water soluble of the three 

components, although its solubility is low and it is not expected to persist in water for more than a 

few days. Neither 2-nitrodiphenylamine nor dibutyl sebacate is volatile or soluble enough for the 

partitioning to air or water to be important fate processes. 2-Nitrodiphenylamine has been found in 

river sediment receiving waste water runoff from an army ammunition plant; this is considered the 

most likely fate for this chemical. The information on dibutyl sebacate is too limited to determine its 

transport and partitioning in the environment. However, it is known to be rapidly biodegraded by a 

wide range of microorganisms. Both propylene glycol dinitrate and 2-nitrodiphenylamine are 

photolyzed and photooxidized in water. It is likely that these substances are similarly broken down in 

the air. The data on biodegradation of propylene glycol dinitrate and 2-nitrodiphenylamine are mixed. 

Some experiments indicate these compounds are readily degraded and others indicate limited 

biodegradation. A bioconcentration factor has been calculated only for 2-nitrodiphenylamine. It 

indicates that this chemical does not bioconcentrate in aquatic organisms or biomagnify in the food 

chain. People working in occupations in which Otto Fuel II is manufactured or used, such as 

personnel involved in clean up operations or waste treatment facilities handling Otto Fuel II, are most 

likely to be exposed to the chemical and its components. Incomplete data on disposal practices and 

levels in the environment prevented a determination of the likelihood of exposure of people !iving or 

working near hazardous waste sites. General population exposure to Otto Fuel II is not expected to 

occur because of the limited manufacture and use of the compound, and the suggested low mobility of 

Otto Fuel II and its components in the environment. However, the general population may be 

significantly exposed to 2-nitrodiphenylamine or dibutyl sebacate as a result of their manufacture and 

use in a number of civilian products. 
OTTO FUEL II AND ITS COMPONENTS 126 

5. POTENTIAL FOR HUMAN EXPOSURE
 

Otto Fuel II has been detected at 2 of the 1,397 NPL sites that have been proposed for inclusion on 

the NPL (HazDat 1994). The frequency of these sites within the United States can be seen in 

Figure 5- 1. 

5.2 RELEASES TO THE ENVIRONMENT 

5.2.1 Air 

There is no information on the release of Otto Fuel II, 2-nitrodiphenylamine, or dibutyl sebacate to air. 

Propylene glycol dinitrate could be released to air during torpedo maintenance procedures, 

manufacturing, transport, etc. However, since the vapor pressure of propylene glycol dinitrate is very 

low, these releases are not expected to be substantial. Azeotropic evaporation of propylene glycol 

dinitrate from Otto Fuel II manufacturing waste water may also release propylene glycol dinitrate into 

the air (Wyman et al. 1984). Experiments conducted using a photochemical smog chamber to simulate 

reactions that might occur in polluted atmospheres indicate that low levels of propylene glycol 

dinitrate (approximately 0.1 ppm or less) are generated when air containing 3 ppm propylene and 

1.5 ppm nitrogen oxide compounds (NO or NO2) are irradiated with high pressure xenon lamps 

(Akimoto et al. 1978, 1980). Further investigation showed that the production of propylene glycol 

dinitrate was a result of the reaction of photochemically generated nitrogen pentoxide (N205) 

(Akimoto et al. 1978, 1980) with atmospheric propylene (Akimoto et al. 1978; Hoshino et al. 1978). 

This suggests that photooxidation of atmospheres containing propylene and nitrogen oxide compounds 

may result in release of propylene glycol dinitrate to the atmosphere. However, the applicability of 

these laboratory experiments to actual events taking place in the atmosphere is uncertain since multiple 

factors that could affect such a reaction (e.g., presence of other compounds, concentrations of 

reactants, turbulence affecting the chance of collisions between potential reactants) are not present in 

the smog chamber. 

5.2.2 Water 

Propylene glycol dinitrate and 2-nitrodiphenylamine are released in waste water effluent streams from 

plants manufacturing and/or using the compounds to formulate special military propellants including 

Otto Fuel II (Army 1979, 1981 a). In 1979, only one facility, Radford Army Ammunition Plant in 

Radford, Virginia, was engaged in the manufacture of propellants containing 2-nitrodiphenylamine 

OTTO FUEL II AND ITS COMPONENTS 128 

5. POTENTIAL FOR HUMAN EXPOSURE
 

(Army 1979). At that time, the level of 2nitrodiphenylamine released in the waste stream from this 

plant was estimated to be 240-670 lbs/per month. Of this amount, about one-half to two-thirds was 

expected to be recovered as particulates from the effluent filters. Approximately 80-200 lbs/per month 

was estimated to be released to the New River, which receives the waste water effluent from the 

Radford Army Ammunition Plant. No information on current releases was located. 

5.2.3 Soil 

Otto Fuel II has been detected in soils (data on levels not available) from two of the 1,397 hazardous 

waste sites that have been proposed for inclusion on the NPL (HazDat 1994). Otto Fuel II 

accidentally spilled on soil during transfer operations could result in additional sites contaminated with 

this monopropellant. 

5.3 ENVIRONMENTAL FATE 

5.3.1 Transport and Partitioning 

Otto Fuel II has a relatively low vapor pressure (8.8×10-2 mm Hg at 25 °C) (Air Force 1985a). Its 

primary component, propylene glycol dinitrate, also has a low vapor pressure (9.8x10-2 mm Hg at 

25 °C) (Crater 1929), which suggests that little evaporation of the compound occurs. In a 

biodegradation study, 80% loss of propylene glycol dinitrate was observed over a 30-day period. 

Since growth curves showed essentially static growth of the microbial culture and no breakdown 

products of biodegradation were detected, the loss could not be attributed to biodegradation. In 

subsequent experiments employing the commercial culture and including a trap to catch released gases, 

61% of the propylene glycol dinitrate added to the culture media was recovered in the exhaust gas 

trap. As in the previous experiments, no metabolites of biodegradation were detected. It was 

concluded that the loss of propylene glycol dinitrate was due to formation of an azeotrope with water. 

The Henry’s law constant for the azeotrope was estimated to be 3.3x102 mm Hg(≈1 x10-2 atm 

m3

/mole) (Wyman et al. 1984). This value of Henry’s law constant would account for the 

volatilization loss of propylene glycol dinitrate from water and indicates that volatilization may be an 

important fate process in water. The vapor pressures of the remaining two components of Otto 

Fuel II, 2-nitrodiphenylamine (1×10-5mm Hg at 25 °C) and dibutyl sebacate (3 mm Hg at 180 °C) 

indicate that evaporation is not a significant fate process ,for these chemicals (Baughman and Perenich 
OTTO FUEL II AND ITS COMPONENTS 129 

5. POTENTIAL FOR HUMAN EXPOSURE
 

1988). However, no values for Henry’s law constants were located that might corroborate the 

volatility characteristic predicted from the vapor pressure data alone. 

Otto Fuel II and its component, dibutyl sebacate are insoluble in water (Air Force 1985a; HSDB 

1994), and 2-Nitrodiphenylamine is insoluble to only slightly soluble (American Cyanamid 1982; 

Army 1979). Therefore, these two compounds are not expected to partition substantially to water and 

these compounds are unlikely to leach from soil to groundwater (Lyman et al. 1982). Propylene 

glycol dinitrate has a solubility of 1.3 g/L (ACGIH 1986) and is expected to partition substantially into 

water, However, since this chemical forms an azeotrope with water that readily volatilizes, it is not 

expected to persist in water for more than a few days. 

2-Nitrodiphenylamine is sparingly soluble in water and was found to precipitate out of waste water 

effluent and sorb to sediment (Army 1979). The chemical has been detected in sediment in a river 

receiving runoff water from an army ammunition plant (Army 1979). An octanol-water partition 

coefficient of 3.07 has been calculated for 2-nitrodiphenylamine (Army 1979). The estimated value of 

octanol-water partition coefficient from EPA’s Graphic Exposure and Modelling System (GEMS) 

(EPA 1986) is 21.7. Both of these values indicate that 2nitrodiphenylamine does not bioaccumulate 

in aquatic organisms and is not likely to biomagnify in the environment. No information on sorption 

to particles, sediments, or soils or on bioaccumulation for Otto Fuel II was located. 

5.3.2 Transformation and Degradation 

5.3.2.1 Air 

No information on the transformation and degradation of Otto Fuel II or its components in air was 

located. However, experiments in aqueous media indicate that both propylene glycol dinitrate and 

2-nitrodiphenylamine are subject to photolysis and photooxidation and that these processes are 

expected to occur in the air as well (Wyman et al. 1984). 

5.3.2.2 Water 

Decomposition of both the propylene glycol dinitrate and 2-nitrodiphenylamine components of Otto 

Fuel II was observed when a solution of the mixture was exposed to ultraviolet (UV) radiation 
OTTO FUEL II AND ITS COMPONENTS 130 

5. POTENTIAL FOR HUMAN EXPOSURE 

(Wyman et al. 1984) under air and under nitrogen. When the tests were conducted in air, >96% of the 

propylene glycol dinitrate was decomposed in 42 hours compared to 57% in the dark controls. 

Decomposition of propylene glycol dinitrate was >89% in 72 hours under nitrogen compared to 9.5% 

in controls. Under both sets of test conditions, 2-nitrodiphenylamine was removed from the solution 

as determined by disappearance of its characteristic peak at 442 nm. However, no quantitative rate 

data on its decomposition were presented. 13C-Nuclear magnetic resonance ( 13C-NMR) detected lactic 

and pyruvic acids in the water-soluble portion of the photolyzed Otto Fuel II. It was concluded that 

UV photolysis of propylene glycol dinitrate produces aldehydes, nitrite esters, nitrogen dioxide, nitric 

oxide and nitrous acid. In the presence of oxidants (oxygen, ozone produced during photolysis), the 

aldehydes possibly oxidize to lactic acid and pyruvic acid (Wyman et al. 1984). The importance of 

photolysis of propylene glycol dinitrate by sunlight can not be ascertained from the study of Wyman et 

al. (1984) since short wavelength UV lights (wavelengths <290 nm) were not filtered out from the 

light source. The observed photolysis may have occurred as a result of interaction with these short 

wavelength UV light that are not available in sunlight (available wavelengths in sunlight are 

>290 nm). 

Limited data suggest that Otto Fuel II may hydrolyze under basic conditions. Incubation of an Otto 

Fuel II-water mixture with calcium hydroxide and with sodium hydroxide resulted in a loss of 

propylene glycol dinitrate from the solution (Kessick et al. 1978). Sixty percent of the propylene 

glycol dinitrate was lost within 4 hours when calcium oxide was added, and no propylene glycol 

dinitrate could be measured following 15 minutes of incubation with sodium hydroxide. The 

significance of this for the actual environmental fate of propylene glycol dinitrate is not known since 

the high pH involved (10.8 or higher) is rarely found in the environment. In addition, work of other 

investigators suggests that the loss of the propylene glycol dinitrate in these experiments could have 

been due to volatilization of the propylene glycol dinitrate-water azeotrope (Wyman et al. 1984). 

There is conflicting evidence for the microbial breakdown of propylene glycol dinitrate. Experiments 

using batch and continuous culture methods with an inoculum of fresh activated sewage sludge from a 

domestic sewage treatment plant revealed evidence of biodegradation of the compound (Army 1981a). 

Loss of propylene glycol dinitrate from the cultures was observed and propylene giycol mononitrate 

was identified as a metabolite of the compound. Loss of propylene glycol mononitrate was also 

observed in this series of experiments. These data indicate that biodegradation occurs by sequential 

cleavage of the nitrate groups resulting in formation of propylene glycol. A companion study showed 
OTTO FUEL II AND ITS COMPONENTS 131 

5. POTENTIAL FOR HUMAN EXPOSURE 

that propylene glycol was also rapidly biodegraded (Army 1981b). In contrast, studies performed with 

pure cultures of Pseudomonas aeruginosa, microorganisms from sewage sludge, and a commercial 

culture of mixed microorganisms specifically designed to degrade recalcitrant substances in waste 

water from treatment plants indicated that propylene glycol dinitrate was not readily biodegraded by 

microorganisms (Wyman et al. 1984). On addition of an inoculum of the culture into the Otto Fuel II 

solution, an initial increase in cells of 1-2 logs was observed over the first 24 hours followed by 

constant cell counts for the remainder of the 30-day study period. The initial increase in cells was 

likely due to degradation of the dibutyl sebacate plasticizer since this chemical has been shown to be 

readily degraded by environmental bacteria and fungi (Klausmeier 1986; Klausmeier and Jones 1960; 

Klausmeier and Osmon 1976; Osmon et al. 1972; Stahl and Pessen 1953). However, since this 

component of Otto Fuel II was not specifically monitored, the increased growth cannot be 

unequivocally attributed to degradation of the dibutyl sebacate. Propylene glycol dinitrate and 

2-nitrodiphenylamine were not considered to be biodegraded as no metabolites were detected. 

Experiments with mixed bacterial cultures from municipal sewage, acclimated to Otto Fuel II by 

preexposure to the compound, did not degrade propylene glycol dinitrate (Kessick et al. 1978). In 

addition, biochemical oxygen demand (BOD) over a 5-day period did not change substantially when 

Otto Fuel II was used as the sole carbon source. These data indicate that Otto Fuel II is not readily 

degraded by microorganisms. Experiments monitoring BOD in the presence of glucose (as the carbon 

source) and increasing concentrations of Otto Fuel II (as measured by propylene glycol dinitrate) 

showed decreased BOD with increasing Otto Fuel II concentration, suggesting that Otto Fuel II was 

toxic to the microbial culture. The authors considered propylene glycol dinitrate to be the toxic 

component, although no data were presented to support this assumption. 2-Nitrodiphenylamine and 

dibutyl sebacate were not monitored in this study. 

5.3.2.3 Sediment and Soil 

No data on the biotransformation and degradation of Otto Fuel II and two of its components, 

propylene glycol dinitrate and dibutyl sebacate, were located. 2-Nitrodiphenylamine has been reported 

to be degraded by mixed cultures of microorganisms when it is available as the sole carbon source 

(Kessick et al. 1978). However, no data were located to support this or to indicate the importance of 

biodegradation on the environmental fate of 2-nitrodiphenylamine. 
OTTO FUEL II AND ITS COMPONENTS 132 

5. POTENTIAL FOR HUMAN EXPOSURE 

5.4 LEVELS MONITORED OR ESTIMATED IN THE ENVIRONMENT 

5.4.1 Air 

Grab samples of air in four U.S. Navy torpedo facilities (Naval Weapons Station, Charleston, South 

Carolina; Naval Weapons Station, Yorktown, Virginia; Naval Submarine Support Facility, New 

London, Connecticut; and Naval Torpedo Station, Keyport, Washington) had levels ranging from 0 to 

0.22 ppm propylene glycol dinitrate (detection limit not reported) (Horvath et al. 1981). No data on 

levels of 2-nitrodiphenylamine or dibutyl sebacate were located. 

5.4.2 Water 

Dibutyl sebacate was detected in one sample of finished water from an advanced waste treatment plant 

in Lake Tahoe, California. The concentration of the dibutyl sebacate was not reported. Since dibutyl 

sebacate is a commonly used plasticizer, it is likely that the dibutyl sebacate found in the water was 

not due to Otto Fuel II contamination (EPA 1984a, 1984b). 

Levels of 2-nitrodiphenylamine ranging from 1 to 14 ppm (mean of 3.5 ppm) have been found in the 

New River, which receives effluent water from the Radford Army Ammunition Plant in Radford, 

Virginia (Army 1979). 

No data on concentrations of propylene glycol dinitrate in water were located. 

5.4.3 Sediment and Soil 

Levels of 0.5-12.2 ppm (mean of 1.5 ppm) 2-nitrodiphenylamine were found in the sediments of the 

New River (Army 1976). The New River receives effluent waste water from the Radford Army 

Ammunition Plant. 

5.4.4 Other Environmental Media 

Limited data were located regarding levels of dibutyl sebacate in food. Samples of hard and processed 

cheese, liver pate, and black pudding purchased from supermarkets in the United Kingdom contained 
OTTO FUEL II AND ITS COMPONENTS 133 

5. POTENTIAL FOR HUMAN EXPOSURE 

levels of dibutyl sebacate ranging from 2.3 to 137 mg/kg (Castle et al. 1988). The lowest levels were 

found in the hard cheese, and the highest levels were in the processed cheese and meat products 

packaged in plastic tubs. The diethyl sebacate in these samples was assumed to have migrated from 

the plastic wrap used to store the foods and known to contain dibutyl sebacate as a plasticizer. The 

plastic containers contained from 3.5% to 4.1% diethyl sebacate that had been added as a plasticizer 

when the containers were manufactured. A sample of leaf lettuce taken from a private garden in 

Finland contained 0.5 ug 2-nitrodiphenylamine/kg fresh weight of lettuce (Wickstrom et al. 1986). 

However, the source of the 2-nitrodiphenylamine was probably reaction of polyaromatic hydrocarbons 

with nitro compounds in the air and not Otto Fuel II contamination. These possible sources of dibutyl 

sebacate and 2-nitrodiphenylamine contamination should be considered when looking for evidence of 

Otto Fuel II contamination in environmental samples. No information on the concentrations of 

propylene glycol dinitrate in other environmental media were located. 

5.5 GENERAL POPULATION AND OCCUPATIONAL EXPOSURE 

There were insufficient data to reliably assess the potential for general population exposure to Otto 

Fuel II and its components. However, given the limited manufacture and use of the compound, 

general population exposure is expected to be limited to persons in the immediate vicinity of waste 

water effluents containing Otto Fuel II or its components. 

Workers employed in occupations in which Otto Fuel II is used (e.g., torpedo maintenance workers) 

may be exposed to airborne propylene glycol dinitrate. A survey of four Navy torpedo facilities 

suggested that, in some instances, the air concentrations might exceed the threshold limit value (TLV) 

of 0.2 ppm in effect at the time the measurements were taken (Horvath et al. 1981). Concentrations 

ranged from 0.0 to 0.22 ppm (one sample exceeded the TLV). However, 88% of the air samples taken 

from the facilities had levels of 0.1 ppm or less, and 50% were <.05 ppm. Alveolar breath analysis 

was conducted on two workers employed in Navy torpedo facilities (Horvath et al. 1981). Propylene 

glycol dinitrate was monitored as an indicator of exposure to Otto Fuel II. A level of 0.001 ppm was 

measured in the breath of one of the workers 5 minutes after exposure to air concentrations ranging 

from 0.01 to 0.026 ppm ceased. No propylene glycol dinitrate was detected 15 minutes after exposure 

ceased. In the second worker, concentrations of 0.0008 and 0.0004 ppm were measured in the expired 

air 5 and 15 minutes, respectively, after exposure to 0.015-0.222 ppm. 
OTTO FUEL II AND ITS COMPONENTS 134 

5. POTENTIAL FOR HUMAN EXPOSURE
 

The National Occupational Exposure Survey (NOES) conducted by NIOSH during 1981-1983 to 

estimate worker exposure to chemicals in different professions did not include any estimate for Otto 

Fuel II or propylene glycol dinitrate (NOES 1991). However, this survey estimated that 4,856 workers 

employed in special contracted trades, miscellaneous manufacturing industries, and personal services 

were potentially exposed to dibutyl sebacate (NOES 1991). Professions included roofers, laundering 

and dry cleaning machine operators, assemblers, construction laborers, and hand packers and 

packagers. None of the exposed persons appeared to be employed in facilities or professions in which 

Otto Fuel II was manufactured or used. These data are not considered relevant to an assessment of 

occupational exposure to Otto Fuel II. 

5.6 POPULATIONS WITH POTENTIALLY HIGH EXPOSURES 

The only populations that appear to be potentially exposed to higher levels of Otto Fuel II and its 

components are people who manufacture Otto Fuel II and/or are involved in torpedo refueling and 

maintenance operations. 

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 Otto Fuel II and its components is available. Where 

adequate information is not available, ATSDR, in conjunction with 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 Otto Fuel II and its components. 

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 or eliminate 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 may 

be proposed. 
OTTO FUEL II AND ITS COMPONENTS 135 

5. POTENTIAL FOR HUMAN EXPOSURE 

5.7.1 Identification of Data Needs 

Physical and Chemical Properties. Several important physical properties of Otto Fuel II and its
 

three components, propylene glycol dinitrate, 2-nitrodiphenylamine, and dibutyl sebacate, have yet to
 

be characterized. These include their octanol-water and organic carbon partition coefficients and
 

Henry’s law constants. These data are important in estimating the fate of released Otto Fuel II in the
 

environment and determining the potential for human exposure.
 

Production, Import/Export, Use, and Release and Disposal. Data were located that
 

described the production of 2-nitrodiphenylamine and dibutyl sebacate (Army 1979; HSDB 1994).
 

Dibutyl sebacate is currently manufactured in the United States (HSDB 1994; SRI 1991; Thomas
 

Publishing 1990a), but no information on the current production of 2-nitrodiphenylamine was located.
 

No information was located discussing the production of either Otto Fuel II or its major component,
 

propylene glycol dinitrate. Import/export data on Otto Fuel II and its components were also missing.
 

Only proposed methods of disposal were found (Army 1979; Dietrich et al. 1985; Kessick et al. 1978;
 

Smith et al. 1983), and no information was located on methods of disposal commonly and/or currently
 

used. These data are necessary to determine the likelihood of human exposure to Otto Fuel II and its
 

components.
 

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 1988, became available in
 

May of 1990. This database will be updated yearly and should provide a list of industrial production
 

facilities and emissions.
 

Environmental Fate. The environmental fate of Otto Fuel II and its components is largely
 

unknown. Otto Fuel II and its components are not extremely volatile or soluble; however, propylene
 

glycol dinitrate does form a volatile azeotrope with water (Wyman et al. 1984). This makes
 

evaporation of propylene glycol dinitrate an important fate process. 2-Nitrodiphenylamine may
 

precipitate from water or sorb to particulates (Army 1979). Dibutyl sebacate is rapidly biodegraded,
 

but the data on biodegradation of propylene glycol dinitrate and 2-nitrodiphenylamine are equivocal.
 

Both of these chemicals are photolyzed by UV light (Wyman et al. 1984). However, the importance
 

of photolysis of propylene glycol dinitrate as a result of interaction with sunlight has not been
 
OTTO FUEL II AND ITS COMPONENTS 136 

5. POTENTIAL FOR HUMAN EXPOSURE 

ascertained. More information on the environmental fate of the mixture and its components is needed 

to fully assess the risk of exposure to populations living near facilities where they may be released. 

Bioavailability from Environmental Media. Experiments in animals have shown that propylene 

glycol dinitrate is absorbed by inhalation, oral, and dermal routes (Andersen and Mehl 1979; Army 

1979; Clark and Litchfield 1969; Jones et al. 1972; Mattsson et al. 1981; Smith 1953; Stewart et al. 

1974). 2-Nitrodiphenylamine and dibutyl sebacate are also absorbed following ingestion (Andersen 

and Mehl 1979; Army 1979; Clark and Litchfield 1969; Jones et al. 1972; Smith 1953). The potential 

for absorption of 2-nitrodiphenylamine and dibutyl sebacate following inhalation or dermal contact 

could not be determined from the data located. No further information on bioavailability is needed for 

dibutyl sebacate because the compound is not toxic. However, propylene glycol dinitrate is toxic, and 

the potential toxicity of 2-nitrodiphenylamine is undetermined. Therefore, more data on the 

bioavailability of these compounds from air, water, soil, and food are needed to assess fully the risk 

posed by these Otto Fuel II components. 

Food Chain Bioaccumulation. An estimated bioaccumulation factor for 2-nitrodiphenylamine 

based on calculations indicates that this chemical does not bioconcentrate (Army 1979). No data were 

located for the remaining two components of Otto Fuel II. More information on the bioconcentration 

potential of these chemicals, including experimental data, is needed to determine the risk of 

biomagnification in the food chain. 

Exposure Levels in Environmental Media. Very little information was located on the levels of 

Otto Fuel II and its components in environmental media (Army 1976, 1979; Castle et al. 1988; EPA 

1984a, 1984b; Horvath et al. 1981; Wickstrom et al. 1986). Most of the data that were located did not 

concern levels of components originating from Otto Fuel II contamination (Castle et al. 1988; EPA 

1984a, 1984b; Wickstrom et al. 1986). This information would be useful in determining the risk to 

populations living or working in the vicinity of facilities releasing Otto Fuel II to water and soil. 

Reliable monitoring data for the levels of Otto Fuel II in contaminated media at hazardous waste sites 

are needed so that the information obtained can be used in combination with the known body burden 

of Otto Fuel II to assess the potential risk of adverse health effects in populations living the vicinity of 

hazardous waste sites. 
OTTO FUEL II AND ITS COMPONENTS 137 

5. POTENTIAL FOR HUMAN EXPOSURE
 

Exposure Levels in Humans. Limited data were located on exposure levels in humans working 

in facilities where Otto Fuel II is used. These data indicate that workers employed in occupations 

where Otto Fuel II is used are exposed to sub-ppm levels of Otto Fuel II (Horvath et al. 1981). 

Alveolar breath samples of two exposed workers had levels of propylene glycol dinitrate of less than 

1 ppb. Additional monitoring studies in occupationally exposed workers would be useful for better 

defining human exposure to Otto Fuel II. This information is necessary for assessing the need to 

conduct health studies on these populations. 

Exposure Registries. No exposure registries for Otto Fuel II or its components were located. 

This substance is not currently one of the substances 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 the exposure to this substance. 

5.7.2 Ongoing Studies 

No ongoing studies were located regarding the potential for human exposure to Otto Fuel II and its 

components. 

OTTO FUEL II AND ITS COMPONENTS 139 

6. ANALYTICAL METHODS 

The purpose of this chapter is to describe the analytical methods that are available for detecting and/or 

measuring and monitoring Otto Fuel II and its components in environmental media and in biological 

samples. The intent is not to provide an exhaustive list of analytical methods that could be used to 

detect and quantify Otto Fuel II and its components. Rather, the intention is to identify wellestablished 

methods that are used as the standard methods of analysis. Many of the analytical methods 

used to detect Otto Fuel II and its components in environmental samples are the methods approved by 

federal organizations such as EPA and the National Institute for Occupational Safety and Health 

(NIOSH). Other methods presented in this chapter may be 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 may be included that refine previously used methods to 

obtain lower detection limits, and/or to improve accuracy and precision. 

6.1 BIOLOGICAL SAMPLES 

The chief component (75%) of Otto Fuel II is propylene glycol dinitrate. The balance of Otto Fuel II 

is composed of 2-nitrodiphenylamine (2%) and dibutyl sebacate (23%). The constituent of Otto Fuel 

II that presents the major health concern is propylene glycol dinitrate. Therefore, exposure levels to 

Otto II fuels have been based on measured propylene glycol dinitrate levels and/or its metabolites 

1-propylene glycol mononitrate and 2-propylene glycol mononitrate. Methods were located for the 

analysis of propylene glycol dinitrate or its metabolites in expired air, blood, urine, and hand swabs. 

However, no methods of detecting the chemical or its metabolites in tissues were found. No 

information was located concerning the detection or quantification of dibutyl sebacate or 

2-nitrodiphenylamine in biological materials. Details of commonly used analytical methods for several 

types of biological media are presented in Table 6-l. 

Two analytical methods exist for detecting propylene glycol dinitrate in expired air. These are gas 

chromatography (GC) with electron capture detector (ECD) (Horvath et al. 1981; Stewart et al. 1974) 

and GC with mass spectrometry (MS) (Air Force 1982b). Very little information on these two 

methods was given. The lower detection limit of the MS method was less than 1 mg/m3

 propylene 

glycol dinitrate in air, but no information on accuracy and precision was reported. Levels of 

propylene glycol dinitrate as low as 0.003 mg/m3

 were reported using the ECD method (Horvath et al. 

OTTO FUEL II AND ITS COMPONENTS 141 

6. ANALYTICAL METHODS 

1981). These limited data suggest that GC/ECD may offer better sensitivity than GC/MS. However, 

GC/MS generally provides better selectivity. 

Methods exist for detecting propylene glycol dinitrate and its metabolites in blood and urine. The 

primary method of analysis for propylene glycol dinitrate and its metabolites in blood and urine is gas 

chromatography with electron capture detection (Litchfield 1968). A disadvantage of this method is 

that sample preparation is time consuming, taking 2-3 hours. However, a more rapid GC method 

enables sample preparation to be completed within 5 minutes (Erk et al. 1982). This rapid method 

reliably detects propylene glycol dinitrate in blood at concentrations ranging from 0.01 μg/mL to 

25 μg/mL. Because propylene glycol dinitrate is rapidly broken down in blood to the corresponding 

mononitrates and inorganic nitrates, extraction from the blood should be carried out immediately after 

the sample is drawn (Litchfield 1968). An outdated but simple method for determining propylene 

glycol dinitrate in blood and urine is calorimetric analysis (Litchfield 1968). Propylene glycol 

dinitrate is determined spectrophotometrically following alkaline hydrolysis and a diazotization and 

coupling reaction. This procedure has several drawbacks; it is time consuming, nonspecific, and 

relatively insensitive. The lower detection limit is only 0.2 μg/mL, more than an order of magnitude 

greater than GCYECD. In addition, the method does not distinguish between individual nitrates in a 

mixture of esters. The use of GC with ECD overcomes this difficulty, and the identification of nitrate 

esters can be achieved. MS with a blood gas catheter was used to detect propylene glycol dinitrate in 

blood; however, the catheter was not useful and had a high retention rate of propylene glycol dinitrate 

(Air Force 1982b). The limit of detection was only 1 μg/mL. 

6.2 ENVIRONMENTAL SAMPLES 

Because of the low threshold limit value (TLV) in the United States of 0.05 ppm for propylene glycol 

dinitrate (ACGIH 1994), effective means of monitoring very low levels of propylene glycol dinitrate 

vapors are needed to monitor workers, and prevent exposure to toxic levels. Various methods such as 

polarography, piezoelectric crystals, high-pressure liquid chromatography (HPLC) with flame 

ionization (FID), electrochemical (EC), or ultraviolet (UV) detector, linear sweep voltammetry (LSV), 

GC with thermal energy analyzer (TEA), FID, or ECD, and thin-layer chromatography (TLC) have 

been investigated for detecting propylene glycol dinitrate in environmental samples. Analytical 

methods were located for monitoring propylene glycol dinitrate in air and water. Details of commonly 

used analytical methods for air and water are presented in Table 6-2. 


OTTO FUEL II AND ITS COMPONENTS 144 

6. ANALYTICAL METHODS 

Various methods have been proposed for detecting propylene glycol dinitrate in air. Coated 

piezoelectric quartz crystal microbalances have been studied as potential selective and sensitive 

detectors for the determination of propylene glycol dinitrate vapor levels (Luoma et al. 1987; 

McCallum 1989; Turnham et al. 1985). A prototype instrument with crystal design containing a trap 

for propylene glycol dinitrate on the reference crystal eliminated many of the frequency, stability, and 

selectivity problems associated with these detectors and produced a detection limit of better than 

0.05 ppm. Air samples have been analyzed using TLC, GC/TEA, GC/FID, and HPLC/EC in the 

reductive mode (Tomkins et al. 1985; Wyman et al. 1984). GC/TEA and HPLC/EC have been used to 

separate and detect mono- and dinitrated propylene glycols, and have been applied to the problem of 

quantifying trace levels of nitrated propylene glycols (Tomkins et al. 1985). Both GC/TEA and 

HPLC/EC are capable of rapidly detecting propylene glycol dinitrate at sub-ppm concentrations in a 

liquid extract. While both methods separated propylene glycol mononitrate from propylene glycol 

dinitrate, GC/TEA possessed the added advantages of better sensitivity and resolution of the propylene 

glycol mononitrate isomers. GC/TEA exhibited a linear range of three orders of magnitude and 

provided detection limits in the μg/mL range or lower for propylene glycol dinitrate and the two 

propylene glycol mononitrate isomers. IHPLC/EC provided a linear response over two orders of 

magnitude and was best suited for the determination of propylene glycol dinitrate. GC/FID and TLC 

could not be compared to other methods because no details on method sensitivity and reliability were 

reported (Wyman et al. 1984). Infrared spectrometry and GC/ECD have been used in the 

quantification of propylene glycol dinitrate in an inhalation exposure chamber (Stewart et al. 1974). 

Propylene glycol dinitrate has also been quantified in a photochemical smog chamber using Fourier 

transform infrared spectrometry (FTIR), GC/ECD, and GC/MS (Akimoto et al. 1978, 1980; Hoshino et 

al. 1978). No data on the sensitivity and reliability of these methods were provided. 

Analytical methods for detecting propylene glycol dinitrate and its metabolites, propylene glycol 

1-mononitrate and propylene glycol 2-mononitrate in effluent water include polarography, GC, and 

linear sweep voltammetry (LSV). GC has been used to measure the concentration of propylene glycol 

dinitrate in waste water (Kessick et al. 1978). No information on the detector, or selectivity and 

sensitivity of this method was provided. GC/ECD has been used to determine propylene glycol 

dinitrate in effluent water (Navy 1976a, 1976b, 1979). This method detected propylene glycol 

dinitrate but not propylene glycol mononitrate. Since propylene glycol dinitrate can hydrolyze rapidly 

to propylene glycol mononitrate in sump water during storage and also during the clean-up operation 

of the purification system, GC/ECD has limited use in the monitoring of effluent water. Single sweep 
OTTO FUEL II AND ITS COMPONENTS 145 

6. ANALYTICAL METHODS 

polarographic equipment has been designed for field use to monitor propylene glycol dinitrate and 

propylene glycol mononitrate in effluent water (Navy 1976a, 1976b, 1977a, 1979). The effluent water 

monitored by the polarograph was obtained from a carbon adsorption system designed to remove 

propylene glycol dinitrate from Otto Fuel II waste water to concentration levels of 1.0 mg/L. 

Sensitivity was in the low ppb range with very good accuracy. LSV has been proposed for use in 

quantifying propylene glycol dinitrate in effluent water by examining the reduction of propylene glycol 

dinitrate at a silver wire electrode (Fine and Miles 1983; Navy 1984a, 1984b). Propylene glycol 

dinitrate was readily detectable at 0.5 mg/L. A procedure using reverse phase HPLC and UV 

detection has been described for the detection and quantification of propylene glycol dinitrate in waste 

water down to 1 mg/L (DREA 1986). Further details, including accuracy, precision, and selectivity of 

the methods, were not provided. TLC and UV spectrophotometry have been used to 

semiquantitatively monitor propylene glycol dinitrate in aqueous culture media (Wyman et al. 1984). 

These methods could also be applied to contaminated waste water. Lactic and pyruvic acids, 

suspected of being metabolites from the photolysis/photooxidation of propylene glycol dinitrate, have 

been identified using nuclear magnetic resonance (NMR) spectrometry (Wyman et al. 1984), but no 

details were reported for this method. 

Analytical methods have been developed for the determination of aqueous components of Otto Fuel II 

other than propylene glycol dinitrate. 2-Nitrodiphenylamine has been measured in effluent water and 

river sediment samples using HPLC/UV and GC/FID (Army 1976). The HPLC-UV method was 

suitable for measuring 2-nitrodiphenylamine at a detection limit of <l0 ppm (<10 mg/L) in water, but 

detection limit for the GC-FID method was not provided. Dibutyl sebacate has been detected in seawater 

and advanced waste treatment effluent water using GC/MS (EPA 1984a; Shishido et al. 1984). 

No information was provided on the sensitivity and reliability of the method; however, when GC/MS 

was combined with three-dimensional mass chromatography (TDMC), dibutyl sebacate was easily 

identified in a contaminated sample for which identification was not possible using GC/MS alone 

(Shishido et al. 1984). 

Limited data were located on the detection of Otto Fuel II components in foods. 

2-Nitrodiphenylamine was measured in lettuce using GC/MS (Wickstrom et al. 1986). The sensitivity 

was in the sub-ppb range. Dibutyl sebacate was detected in packaged foods wrapped in dibutyl 

sebacate-containing plastics using high-resolution gas chromatography (HRGC)/FID (Castle et al. 
OTTO FUEL II AND ITS COMPONENTS 146 

6. ANALYTICAL METHODS
 

1988). The sensitivity for this method was in the low ppb. No other data on the reliability and 

usefulness of these methods were reported. 

2-Nitrodiphenylamine has also been detected in other environmental samples including propellants, 

smokeless powders, explosives, and gunshot residues. GC/FID was used to determine the presence of 

2-nitrodiphenylamine in nitrocellulose propellants (Dykes and Alley 1974). This method had an 

estimated relative standard deviation (RSD) of 0.44% which is excellent repeatability for this type of 

analysis. However, GC methods may not be desirable for the analysis of 2-nitrodiphenylamine as 

N-nitrosodiphenylamine (aging product of nitrodipheylamine) is denitrosated to diphenylamine in the 

heated zone of the chromatograph and remains undetected (Via and Taylor 1992). HPLC/UV using 

reverse phase columns has also been used to determine the presence of 2-nitrodiphenylamine in 

propellants (Army 1986b). The method accurately identified and quantified 2-nitrodiphenylamine in 

the complex propellant mixture. 2-Nitrodiphenylamine in propellants has also been detected using 

reverse phase HPLC/EC (Bergens 1987). The author stated that HPLC/EC is more selective and 

sensitive than HPLC/UV and that it provides a more uniform response compared with UV detection. 

The detection limit was 4.3 μg/L, and the RSD was 1.O-2.0%. Methods for detecting 

2-nitrodiphenylamine in smokeless powders and in gunshot residues have been proposed. For 

smokeless powders, use of HPLC/UV/TEA was investigated (Bender 1983). By using UV/TEA 

detectors in tandem, compounds could be analyzed in the low nanogram range and selectivity was 

increased. HRGC combined with TEA or ECD has been used for analysis of explosives in spiked 

hand swabs (Douse 1985). The author stated that TEA was shown to approach the sensitivity of ECD 

but was more selective, enabling low nanogram levels of explosives in hand swabs to be detected. 

Methods of analysis that were located for explosives and gunshot residues include HPLC/ECD, 

HPLC/UV (Bratin et al. 1981; Dahl and Lott 1987), and micellar electrokinetic capillary 

electrophoresis with UV spectrophotometry (MECE/UV) (Northrop et al. 1991). HPLC/ECD had a 

lower detection limit (4.1 μg/L) than HPLC/UV (45.5 μg/L) (Bratin et al. 1981). MECE/JV is a 

proposed qualitative method for providing rapid and efficient separation and detection of organic 

gunshot and explosive constituents. MECE is an adaptation of capillary electrophoresis where the 

addition of a charged micellar agent to the electrolyte provides a separation of neutral molecules. 

Because each component has a characteristic UV absorption profile, analysis at several different 

wavelengths can provide additional identification of the components. No information on accuracy, 

sensitivity, or specificity was given so the method cannot be compared to other located methods. 

Perhaps the best method available for the analysis of Otto Fuel II components in complex solid 
OTTO FUEL II AND ITS COMPONENTS 147 

6. ANALYTICAL METHODS
 

matrices is supercritical fluid extraction, supercritical fluid chromatography and MS detection and 

quantification. This method assures sample integrity, affords faster analysis time compared to 

conventional methods and enhances the sensitivity of detection (Via and Taylor 1992). 

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 Otto Fuel II and its components is available. Where 

adequate information is not available, ATSDR, in conjunction with 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 Otto Fuel II and its components. 

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 or eliminate 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 may 

be proposed. 

6.3.1 Identification of Data Needs 

Methods for Determining Biomarkers of Exposure and Effect. Methods exist for measuring 

propylene glycol dinitrate in breath, blood, and urine (Air Force 1982b; Erk et al. 1982; Litchfield 

1968; Stewart et al. 1974). Most of the studies did not report enough relevant information on 

sensitivity, accuracy, precision, and selectivity to determine their reliability for monitoring exposure to 

Otto Fuel II and its components. No methods of measuring 2-nitrodiphenylamine or dibutyl sebacate 

in biological media were located. More thorough studies of possible methods for monitoring exposure 

are needed to determine the best biomarkers for monitoring exposure to Otto Fuel II and its 

components. 

The biomarkers of effect for Otto Fuel II and its components are very general and include headache, 

mild metbemoglobinemia, and dizziness (Horvath et al. 1981). Since these effects are nonspecific and 
OTTO FUEL II AND ITS COMPONENTS 148 

6. ANALYTICAL METHODS
 

cannot be quantified, they are not useful biomarkers of effect for Otto Fuel II and its components. A 

specific biomarker of exposure is needed so that monitoring studies of occupationally exposed workers 

and other potentially exposed populations can be conducted. 

Methods for Determining Parent Compounds and Degradation Products in 

Environmental Media. Methods exist for detecting propylene glycol in air and water (Akimoto et 

al. 1980; DREA 1986; McCallum 1989; Navy 1979, 1984a, 1984b; Tomkins et al. 1985; Wyman et al. 

1984), 2nitrodiphenylamine in water, sediment, lettuce, and munitions compounds (Army 1976, 

1986a; Wickstrom et al. 1986; Wyman et al. 1984), and dibutyl sebacate in water and food (Castle et 

al. 1988; EPA 1984a; Shishido et al. 1984). Very few details on the sensitivity, accuracy, precision, 

and selectivity of the methods were provided. More detailed analyses of these methods are needed in 

order to determine their reliability for measuring background and greater levels of Otto Fuel II and its 

components in environmental media. 

6.3.2 Ongoing Studies 

No ongoing studies were located regarding analytical methods for Otto Fuel II or its components, 
OTTO FUEL II AND ITS COMPONENTS 149 

7. REGULATIONS AND ADVISORIES 

The international, national, and state regulations and guidelines regarding Otto Fuel II and its major 

components in air, water, and other media are summarized in Table 7-l. 

ATSDR has derived three MRL values for propylene glycol dinitrate, the major component of Otto 

Fuel II. An acute inhalation MRL of 0.003 ppm was derived for propylene glycol dinitrate based on 

altered visual evoked responses in humans (Stewart et al. 1974). An intermediate and chronic 

inhalation MRL of 0.00004 ppm was derived for propylene glycol dinitrate based on decreased levels 

of hematocrit, hemoglobin, red blood cells, and reticulocytes and increased levels of methemoglobin in 

dogs (Air Force 1985a). There is no EPA reference dose (RfD) or reference concentration (RfC) for 

Otto Fuel II or its major components. 

Under the Hazardous Materials Transportation Act, Otto Fuel II is designated as a hazardous substance 

subject to special requirements for packaging, labeling, and transportation (DOT 1989a, 1989b). 

__________ 

OTTO FUEL II AND ITS COMPONENTS 151 

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*Cited in text 
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Sciences/National Research Council. Washington, DC: National Academy Press, 15-35. 

*NATICH. 1992. National Air Toxics Information Clearinghouse. Data base report on federal, state, 

local, and EPA air toxics activities. U.S. Environmental Protection Agency, Research Triangle Park, 

NC. EPA-453/R-92-008. 

Navy. 1973. Experimental human exposure to propylene glycol dinitrate. Report for the Department 

of the Navy, Bureau of Medicine and Surgery. Document no. AD 766977. 

*Navy. 1976a. Applied polarography for analysis of ordnance materials: Part 1. Determination and 

monitoring for 1,2-propylene glycol dinitrate in effluent water by single-sweep polarography. China 

Lake, CA: Naval Weapons Center. Document no. AD A026468 

*Navy. 1976b. Applied polarography for analysis of ordnance materials: Part 2. An inexpensive 

solid-state field polarograph with digital and analog output. China Lake, CA: Naval Weapons Center. 

Document no. AD A 030038. 

*Navy. 1977a. Carbon treatment of otto fuel wastewater: A laboratory study. Silver Spring, MD: 

Naval Surface Weapons Center. Document no. AD A040986. 

Navy. 1977b. Studies on bacterial degradation of ordnance wastes. In: Young GA, compiler. 

Proceedings of the Second Conference on the Environmental Effects of Explosives and Explosions 

(13-14 October 1976). Dahlgren, VA and Silver Spring, MD: Research and Technology Department, 

Naval Surface Weapons Center. Report no. NSWC/WOLTR 77-36. 

*Navy. 1979. Applied polarography for analysis of ordnance materials: Part 3. Field tests of NWC 

digital polarograph and pollution monitoring system. China Lake, CA: Naval Weapons Center. 

Document no. AD A064424. 

Navy. 1982a. Evaluation of the health risks of ordinance disposal waste in drinking water. Contract 

no. ONR N00014-80-C-0161. Washington, DC: Department of the Navy. Document no. 

PB83-153635. 

*Navy. 1982b. Mutagenicity evaluation of otto fuel number 2 in the Ames Salmonella/microsome 

plate test: Segment report. Arlington, VA: Department of the Navy, Office of Naval Research. 

Document no. AD A112227. 

*Navy. 1984a. Voltammetric analysis of ordnance materials: Part 1. Detection and quantitation of 

nitrate esters and various nitro compounds in water by voltammetry. China Lake, CA: Naval 

Weapons Center. Document no. AD A142269. 
OTTO FUEL II AND ITS COMPONENTS 159 

8. REFERENCES
 

*Navy. 1984b. Voltammetric analysis of ordnance materials: Part 2. A portable digital voltammeter 

for use with a silver wire working electrode. China Lake, CA: Naval Weapons Center. Document 

no. AD A152480. 

Navy. 1985. Morbidity and mortality associated with exposure to otto fuel II in the U.S. Navy 

1966-1979. Bethesda, MD: Naval Medical Research and Development Command, Naval Medical 

Command, National Capital Region. Document no. AD A148726 

*Nickerson M. 1975. Vasodilator drugs. In: Goodman LS, Gilman A, eds. The pharmacological 

basis of therapeutics. 5th ed. New York, NY: MacMillan Publishing Co., Inc., 727-743. 

*NIOSH. 1992. Recommendations for occupational safety and health. Compendium of policy 

documents and statements. Cincinnati, OH: National Institute on Occupational Safety and Health. 

DHHS no. 92-100. p.116. 

*NOES. 1991. Dibutyl sebacate. National Occupational Exposure Survey. U.S. Department of 

Health and Human Services, National Institute for Occupational Safety and Health. Cincinnati, OH. 

September 11, 1991. 

*Northrop DM, Martire DE, MacCrehan WA. 1991. Separation and identification of organic gunshot 

and explosive constituents by micellar electrokinetic capillary electrophoresis. Anal Chem 

63:1038-1042. 

*NRC. 1982. Evaluation of the health risks of ordnance disposal waste in drinking water. 

Washington, DC: National Research Council. Report no. NRC-TOX-P897. NTIS no. PB83-153635. 

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Occupational Safety and Health Administration. Code of Federal Regulations. 29 CFR 1910.1000. 

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*Osmon JL, Klausmeier RE, Jaminson EI. 1972. Rate-limiting factors in biodeterioration of plastics. 

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*OTA. 1990. Neurotoxicity: identifying and controlling poisons of the nervous system. Office of 

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*Parker JO. 1985. Efficacy of nitrogycerin patches: fact or fancy? Ann Intern Med 102:548-550. 

*Pharmackon. 1988. The effect of organic nitrates upon the blood pressure and heart rate of 

spontaneously hypertensive aortic intubated male rats when administered intra-arterially. Waverly, PA: 

Pharmackon Laboratories. 

*Rivera JC. 1974. Otto fuel II: Health hazards and precautions. U.S. Navy Medicine 63:7-10. 

*RTECS. 1994. Registry of Toxic Effects of Chemical Substances. U.S. Department of Health and 

Human Services, National Institute for Occupational Safety and Health, Washington, DC. 
OTTO FUEL II AND ITS COMPONENTS 160 

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*Saeki Y, Sato A, Sato Y, et al. 1989. Stimulation of the rostral ventrolateral medullary neurons 

increases cortical blood flow via activation of the intracerebral pathway. Neurosci Lett 107:26 32, 

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Van Nostrand Reinhold, 2:1126. 

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Van Nostrand Reinhold, 3:2903-2904. 

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Schefer W. 1975. [Water polluting chemicals.] Umwelthygiene 1:13-17. (German) 

Shepson PB, Kleindienst TE, Edney EO, et al. 1985. The mutagenic activity of the products of 

ozone reaction with propylene in the presence and absence of nitrogen dioxide. Environ Sci Technol 

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*Shishido J, Yoshii K, Takubo Y, et al. 1984. Studies on an automated survey system of 

environmental chemicals by gas chromatography-mass spectrometry-computer: II. Three dimensional 

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explosives. Journal of Hazardous Materials 7:303-316. 

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*Stahl WH, Pessen H. 1953. The microbiological degradation of plasticizers. I. Growth on esters 

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*Stutz DR, Janusz SJ. 1988. Hazardous materials injuries: A handbook for pre-hospital care. 2nd 

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*Thomas Publishing Company. 1990a. Thomas register of American manufacturers: Products and 

services section. New York, NY: Thomas Publishing Company, 4:7342. 

Thomas Publishing Company. 1990b. Thomas register of American manufacturers: Company 

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OTTO FUEL II AND ITS COMPONENTS 161 

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*Tomkins BA, Manning DL, Griest WH, et al. 1985. Selective detection of 1,2propylene glycol 

dinitrate, 1-propylene glycol mononitrate and 2-propylene glycol mononitrate using gas 

chromatography/thermal energy analyzer or liquid chromatography/electrochemical detection. 

Analytical Chimica Acta 169:69-78. 

Tuominen J, Wickstrom K, Pyysalo H. 1986. Determination of polycyclic aromatic compounds by 

gas-liquid chromatography-selected ion monitoring technique. J High Resolut Chromatogr Commun 

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*Turnham BD, Yee LK, Luoma GA. 1985. Coated piezoelectric quartz crystal monitor for 

determination of propylene glycol dinitrate vapor levels. Anal Chem 57:2120-2124. 

*Van H, Deyrup CA, eds. 1991. OPD chemical buyers directory: 1992. 79th Annual edition. New 

York, New York: Schnell Publishing Company, Inc. 

Van Lierop JBH, Van Veen RM. 1988. Determination of plasticizers in fat by gas 

chromatography-mass spectrometry. J Chromatogr 477:230-238. 

*Via JC, Taylor LT. 1992. Chromatographic analysis of nonpolymeric single base propellant 

components. J Chromatogr Sci 30: 106-110. 

Welch JF, Siegwarth JD. 1989. Method for processing of organic compounds. Patented August 29, 

1989. U.S. Patent Office, Washington, DC. Patent no. 4861497. 

Wendt TM, Cornell JH, Kaplan AM. 1978. Microbial degradation of glycerol nitrates. Appl Environ 

Microbial 36:693-699. 

*Wickstrom K, Pyysalo H, Plaami-Heikkila S, et al. 1985. Polycyclic aromatic compounds (PAC) in 

leaf lettuce. Z Lebensm Unters Forsch 183: 182-185. 

*Wild D, King M, Gocke E, et al. 1983. Study of artificial flavoring substances for mutagenicity in 

the SalmoneIla/microsome, BASC and micronucleus tests. Food Chem Toxicol 21:707-719. 

Williams DF. 1981. The toxicology of additives in medical plastics. In: Williams DF, ed. Systemic 

aspects of biocompatibility. Boca Raton, FL: CRC Press, 2:145-157. 

Wyman JF, Gray BH, Lee LH, et al. 1985. Interspecies variability in propylene glycol 

dinitrate-induced methemoglobin formation. Toxic01 Appl Pharmacol 81:203-212. 

*Wyman JF, Guard HE, Coleman WM III. 1984. Environmental chemistry of 1,2-propanediol 

dinitrate: Azeotrope formation, photolysis and biodegradability. Arch Environ Contam Toxicol 

13:647-652. 

OTTO FUEL II AND ITS COMPONENTS 163 

9. GLOSSARY
 

Acute Exposure -- Exposure to a chemical for a duration of 14 days or less, as specified in the 

Toxicological Profiles. 

Adsorption Coefficient (Koc) -- 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 minutes 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. 
OTTO FUEL II AND ITS COMPONENTS 164 

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 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 chemical which 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. 
OTTO FUEL II AND ITS COMPONENTS 165 

9. GLOSSARY
 

q1* -- The upper-bound estimate of the low-dose slope of the dose-response curve as determined by 

the multistage procedure. The ql* can be used to calculate an estimate of carcinogenic potency, the 

incremental excess cancer risk per unit of exposure (usually μg/L for water, mg/kg/day for food, and 

μg/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. 311 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 minutes continually. No more than four excursions are allowed per day, and 

there must be at least 60 minutes 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 8-

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 experimental data. 

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 
OTTO FUEL II AND ITS COMPONENTS 166 

9. GLOSSARY 

uncertainty in using LOAEL data rather than NOAEL data. Usually each of these factors is set equal 

to 10. 
OTTO FUEL II AND ITS COMPONENTS A-1 

APPENDIX A 

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 endpoints, and EPA’s estimated range associated with an upperbound 

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-AdverseEffect 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 2-1 and Figure 2-1 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 2-1) 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. 
OTTO FUEL II AND ITS COMPONENTS A-2 

APPENDIX A 

(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 2-1). 

(5)	 Species The test species, whether animal or human, are identified in this column. Section 2.4, 

"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 18), rats were exposed to toxaphene 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 0.0006 ppm (see footnote "c"). 

(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

adverse health 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. 
OTTO FUEL II AND ITS COMPONENTS A-3 

APPENDIX A 

(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 "c" indicates the NOAEL of 3 ppm in key number 18 was used to

derive an MRL of 0.0006 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 0.0006 ppm (see footnote "c"

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 (q1*). 

(19)	 Key to LSE Figure The Key explains the abbreviations and symbols used in the figure. 


OTTO FUEL II AND ITS COMPONENTS A-6 

APPENDIX A 

Chapter 2 (Section 2.4) 

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 endpoints 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 endpoints 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. Minima1 risk levels (MRLs) for noncancer endpoints (if 

derived) and the endpoints 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 2.4, “Relevance to Public Health,” contains basic information known about the substance. 

Other sections such as 2.6, “Interactions with Other Substances,” and 2.7, “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). 
OTTO FUEL II AND ITS COMPONENTS A-7 

APPENDIX A 

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. 
OTTO FUEL II AND ITS COMPONENTS B-1 

APPENDIX B
 

ACRONYMS, ABBREVIATIONS, AND SYMBOLS
 

ACGIH 

ADME 

atm 

ATSDR 

BCF 

BSC 

C 

CDC 

CEL 

CERCLA 

CFR 

CLP 

cm 

CNS 

d 

DHEW 

DHHS 

DOL 

ECG 

EEG 

EPA 

EKG 

F 

F1 

FAO 

FEMA 

FIFRA 

fpm 

ft 

FR 

g 

GC 

gen 

HPLC 

hr 

IDLH 

IARC 

ILO 

In 

Kd 

kg 

kkg 

K oc 

K ow 

American Conference of Governmental Industrial Hygienists 

Absorption, Distribution, Metabolism, and Excretion 

sphere 

Agency for Toxic Substances and Disease Registry 

bioconcentration factor 

Board of Scientific Counselors 

Centigrade 

Centers for Disease Control 

Cancer Effect Level 

Comprehensive Environmental Response, Compensation, and Liability Act 

Code of Federal Regulations 

Contract Laboratory Program 

centimeter 

central nervous system 

day 

Department of Health, Education, and Welfare 

Department of Health and Human Services 

Department of Labor 

electrocardiogram 

electroencephalogram 

Environmental Protection Agency 

see ECG 

Fahrenheit 

first filial generation 

Food and Agricultural Organization of the United Nations 

Federal Emergency Management Agency 

Federal Insecticide, Fungicide, and Rodenticide Act 

feet per minute 

foot 

Federal Register 

gram 

gas chromatography 

generation 

high-performance liquid chromatography 

hour 

Immediately Dangerous to Life and Health 

International Agency for Research on Cancer 

International Labor Organization 

inch 

adsorption ratio 

kilogram 

metric ton 

organic carbon partition coefficient 

octanol-water partition coefficient 
B-2 

L 

OTTO FUEL II AND ITS COMPONENTS 

APPENDIX B
 

LC 

LCLO 

LC50 

LDL0 

LD50 

LOAEL 

LSE 

m 

mg 

min 

mL 

mm 

mm Hg 

mm01 

mo 

mppcf 

MRL 

MS 

NIEHS 

NIOSH 

NIOSHTIC 

ng 

nm 

NHANES 

nmol 

NOAEL 

NOES 

NOHS 

NPL 

NRC 

NTI S 

NTP 

OSHA 

PEL 

pg 

pmo1 

PHS 

PMR 

ppb 

ppm 

ppt 

REL 

RfD 

RTECS 

sec 

SCE 

SIC 

SMR 

liter 

liquid chromatography 

lethal concentration, low 

lethal concentration, 50% kill 

lethal dose, low 

lethal dose, 50% kill 

lowest-observed-adverse-effect level 

Levels of Significant Exposure 

meter 

milligram 

minute 

milliliter 

millimeter 

millimeters of mercury 

millimole 

month 

millions of particles per cubic foot 

Minimal Risk Level 

mass spectrometry 

National Institute of Environmental Health Sciences 

National Institute for Occupational Safety and Health 

NIOSH’s Computerized Information Retrieval System 

nanogram 

nanometer 

National Health and Nutrition Examination Survey 

nanomole 

no-observed-adverse-effect level 

National Occupational Exposure Survey 

National Occupational Hazard Survey 

National Priorities List 

National Research Council 

National Technical Information Service 

National Toxicology Program 

Occupational Safety and Health Administration 

permissible exposure limit 

picogram 

picomole 

Public Health Service 

proportionate mortality ratio 

parts per billion 

parts per million 

parts per trillion 

recommended exposure limit 

Reference Dose 

Registry of Toxic Effects of Chemical Substances 

second 

sister chromatid exchange 

Standard Industrial Classification 

standard mortality ratio 
OTTO FUEL II AND ITS COMPONENTS
 

STEL 

STORET 

TLV 

TSCA 

TRI 

TWA 

U.S. 

UF 

yr 

GHO 

Wk 

> 

> 

= 

< 

< 

% 

μm 

μg 

α

β

δ

Υ
 

B-3 

APPENDIX B 

short term exposure limit 

STORAGE and RETRIEVAL 

threshold limit value 

Toxic Substances Control Act 

Toxics Release Inventory 

time-weighted average 

United States 

uncertainty factor 

year 

World Health Organization 

Week 

greater than
 

greater than or equal to
 

equal to
 

less than
 

less than or equal to
 

percent
 

alpha
 

beta
 

delta
 

gamma
 

micron
 

microgram
 

*U.S. GOVERNMENT PRINTING OFFICE:638-643