TOXICOLOGICAL PROFILE FOR
 

DIETHYL PHTHALATE
 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
 

Public Health Service
 

Agency for Toxic Substances and Disease Registry
 

June 1995 
DIETHYL PHTHALATE 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. 
DIETHYL PHTHALATE iii 

UPDATE STATEMENT
 

A Toxicological Profile for Diethyl Phthalate was released on November 1993. This edition 

supersedes any previously released draft or final profile. 

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

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

Agency for Toxic Substances and Disease Registry
 

Division of Toxicology/Toxicology Information Branch
 

1600 Clifton Road NE, E-29
 

Atlanta, Georgia 30333
 

V 

FOREWORD
 

This toxicological profile is prepared in accordance with guidelines developed by ATSDR and the 

Environmental Protection Agency (EPA) and in support of Department of Defense information needs. The 

original guidelines were published in the Federal Register on April 17, 1987. Each profile will be revised and 

republished as necessary. 

The ATSDR toxicological profile succinctly characterizes the toxicologic and adverse health effects 

information for the hazardous substance being described. Each profile identifies and reviews the key literature 

(that has been peer-reviewed) that describes a hazardous substance’s toxicologic properties. Other pertinent 

literature is also presented, but described in less detail than the key studies. The profile is not intended to be an 

exhaustive document; however, more comprehensive sources of specialty information are referenced. 

Each toxicological profile begins with a public health statement, which describes in nontechnical 

language 

a substance’s relevant toxicological properties. Following the public health statement is information concerning 

levels of significant human exposure and, when known, significant health effects. The adequacy of information 

to determine a substance’s health effects is described in a health effects summary. Data needs that are significant 

to protect public health will be identified by ATSDR and the EPA. The focus of the profiles is on health and 

toxicologic information; therefore, we have included this information in the beginning of the document. 

Each profile must include the following: 

(A) The examination, summary, and interpretation of available toxicologic information and epidemiologic 

evaluations on a hazardous substance in order to ascertain the levels of significant human exposure for the 

substance and the associated acute, subacute, and chronic health effects. 

(B) A determination of whether adequate information on the health effects of each substance is available 

or in the process of development to determine levels of exposure that present a significant risk to human 

health of acute, subacute, and chronic health effects. 

(C) When appropriate, identification of toxicologic testing needed to identify the types or levels of 

exposure that might present significant risk of adverse health effects in humans. 

The principal audiences for the toxicological profiles are health professionals at the federal, state, and 

local levels, interested private sector organizations and groups, and members of the public. 

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

Act (SARA) of 1986 (Public Law 99-499) which amended the Comprehensive Environmental Response, 

Compensationcand.Liability Act of 1980 (CERCLA or Superftmd). Section 211 of SARA also amended Title 10 

of the U. S. Code, creating the Defense Environmental Restoration Program. Section 2704(a) of Title 10 of the U. 

S. Code directs the Secretary of Defense to notify the Secretary of Health and Human Services of not less 

than 25 of the most commonly found unregulated hazardous substances at defense facilities. 

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

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

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

DIETHYL PHTHALATE vii 

CONTRIBUTORS
 

CHEMICAL MANAGER(S)/AUTHORS(S):
 

Malcolm Williams, Ph.D.
 

ATSDR, Division of Toxicology, Atlanta, GA
 

Charles Shore, Ph.D.
 

Sciences International, Inc., Alexandria, VA
 

THE PROFILE HAS UNDERGONE THE FOLLOWING ATSDR INTERNAL REVIEWS:
 

1. Green Border Review. Green Border review assures the 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 endpoints. 

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. 

DIETHYL PHTHALATE ix 

PEER REVIEW
 

A peer review panel was assembled for diethyl phthalate. The panel consisted of the following 

members: 

1. Dr. Martin Alexander, Cornell University, Department of Agronomy, Ithaca, NY 

2. Dr. Fumio Matsumura, University of California, Davis, CA 

3. Dr. John Lech, Medical College of Wisconsin, Department of Pharmacology and Toxicology, 

Milwaukee, WI 

These experts collectively have knowledge of diethyl phthalate’s physical and chemical properties, 

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

quantification of risk to humans. All reviewers were selected in conformity with the conditions for 

peer review specified in Section 104(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. 









DIETHYL PHTHALATE 1 

1. PUBLIC HEALTH STATEMENT
 

This Statement was prepared to give you information about diethyl phthalate and to 

emphasize the human health effects that may result from exposure to it. The Environmental 

Protection Agency (EPA) has identified 1,397 sites on its National Priorities List (NPL). 

Diethyl phthalate has been found in at least 248 of these sites, one of which is located in 

Guam. However, we do not know how many of the 1,397 NPL sites have been evaluated for 

diethyl phthalate. As EPA evaluates more sites, the number of sites at which diethyl 

phthalate is found may change. This information is important for you to know because 

diethyl phthalate may cause harmful health effects and because these sites are potential or 

actual sources of human exposure to diethyl phthalate. 

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 diethyl phthalate, 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. 
DIETHYL PHTHALATE 2 

1. PUBLIC HEALTH STATEMENT 

1.1 	 WHAT IS DIETHYL PHTHALATE? 

Diethyl phthalate is a man-made colorless liquid with a slight aromatic odor and a bitter, 

disagreeable taste. Trade names include neantine, peilatinol A, and solvanol. Diethyl 

phthalate is manufactured for many uses. It is commonly used to make plastics more flexible. 

Because diethyl phthalate is not a part of the chain of chemicals (polymers) which makes up 

the plastics, it can be released fairly easily from these products. These plastics are found in 

products such as toothbrushes, automobile parts, tools, toys, and food packaging. Diethyl 

phthalate is also used in cosmetics, insecticides, and aspirin. For more information on the 

chemical and physical properties of diethyl phthalate, see Chapter 3. For more information 

on its production and use, see Chapter 4. 

1.2 	 WHAT HAPPENS TO DIETHYL PHTHALATE WHEN IT ENTERS THE 

ENVIRONMENT? 

Diethyl phthalate may enter the environment in industrial waste waters, by evaporation into 

the air from disposal sites, directly from consumer products, from the burning of plastic 

products, and by leaking from landfills into soil or water including groundwater. In air, 

diethyl phthalate may break down into other products. It may also be deposited on the 

ground or in water by rain. Diethyl phthalate may also enter the environment by sticking 

onto dust particles. If released into water, diethyl phthalate may travel great distances in 

swiftly moving rivers. In more slowly moving waters, microorganisms in the water or 

sediment may break down some of the diethyl phthalate into nontoxic products. -Sewage 

bacteria from industrial facilities may break down diethyl phthalate in waste waters. In soils 

containing organic matter (matter with high levels of carbon), diethyl phthalate may stick to 

particles where it may eventually break down. If there is little organic matter in the soil, 

diethyl phthalate may move down through the soil and enter the groundwater. Many 

microorganisms are able to break down diethyl phthalate to carbon dioxide and other harmless 
DIETHYL PHTHALATE 3 

1. PUBLIC HEALTH STATEMENT 

products. Small amounts of diethyl phthalate can build up in animals that live in water, such 

as fish and oysters. For further information on what happens to diethyl phthbalate when it 

enters the environment, see Chapters 4 and 5. 

1.3 HOW MIGHT I BE EXPOSED TO DIETHYL PHTHALATE? 

You may be exposed to diethyl phthalate in consumer products and plastics. You may also 

be exposed during the manufacturing or disposal of products that contain diethyl phthalate. 

Most exposure will result from inhalation of contaminated air or swallowing of contaminated 

drinking water or foods. The measured levels of diethyl phthalate in air, water, and soil are 

generally quite low. For example, diethyl phthalate has been measured at hazardous waste 

sites in the groundwater at 0.0125 parts of diethyl phthalate per million parts (ppm) of water, 

in surface water at 0.0121 ppm, and in soil at 0.039 ppm (on a weight basis, a part per 

million is equivalent to one unit of weight, such as one gram, of a chemical, in l,000,000 

grams of a medium, such as water or soil). Diethyl phthalate has been found in drinking 

water at concentrations of 0.00001-0.0046 ppm, in industrial waste waters at 

0.00001-0.060 ppm, in river waters at 0.00006-0.044 ppm, and in sediments from other large 

bodies of water (Chesapeake Bay and Gulf of Mexico) at up to 0.042 ppm. The amount of 

diethyl phthalate in soil is unknown. However, diethyl phthalate will probably be rapidly 

decomposed by soil bacteria, so that little will be taken up into plants. Diethyl phthalate has 

been measured in indoor air (in a telephone switching office) at 0.00018-0.00022 ppm and in 

outdoor air (Newark, New Jersey) at 0.00004-0.00006 ppm. Fish taken from contaminated 

waters had up to about 2 ppm of diethyl phthalate in their tissues. Oysters contained up to 

about 1 ppm. Diethyl phthalate in plastic packaging may get into food and has been found in 

packaged food (quiche) at concentrations of about 2-5 ppm. The daily human intake of 

diethyl phthalate has been estimated to be 4 milligrams (mg) based on food intake, but the 

annual exposure from drinking contaminated drinking water has been estimated to be quite 

low (0.0058 mg/year/person). 
DIETHYL PHTHALATE 4 

1. PUBLIC HEALTH STATEMENT 

Occupational exposure to diethyl phthalate is possible as a result of its use in plastics and 

other products such as cosmetics and insect repellents. The National Occupational Exposure 

Survey estimated that over 239,000 employees could potentially be exposed to diethyl 

phthalate in the workplace. Diethyl phthalate was found in plants that manufacture rubber 

products at concentrations up to 0.0013 ppm. For further information on how you can be 

exposed to diethyl phthalate, see Chapter 5. 

1.4 HOW CAN DIETHYL PHTHALATE ENTER AND LEAVE MY BODY? 

Diethyl phthalate can enter your body when you breathe air, drink water, or eat food 

containing it. It can also enter your body through your skin. It is possible that exposure 

could occur near hazardous waste sites, at manufacturing facilities, or through the use of 

consumer products containing the substance. If you get it on your skin, your body will 

probably absorb only a small amount of it. We do not know how much you will absorb if 

you breathe or eat it. Once it enters your body, it breaks down into other chemicals, some of 

which are harmful. Diethyl phthalate and its breakdown products will leave your body mostly 

in the urine within about 2 days. Only small amounts of the compound or its breakdown 

products will remain in the tissues. For more information on how diethyl phthalate can enter 

and leave your body, see Chapter 2. 

1.5 HOW CAN DIETHYL PHTHALATE AFFECT MY HEALTH? 

No information is available regarding the possible effects caused by diethyl phthalate if you 

breathe, eat, drink, or have skin contact with it. Because no studies involving humans 

exposed exclusively to diethyl phthalate are available, we must rely on studies in laboratory 

animals. Furthermore, there is no information on the effects of breathing diethyl phthalate in 

laboratory animals. Diethyl phthalate has caused death in animals given very high doses by 

mouth, but brief oral exposures to lower doses caused no harmful effects. One effect found 
DIETHYL PHTHALATE 5 

1. PUBLIC HEALTH STATEMENT 

in animals that ate high doses of diethyl phthalate for long periods of time was a decrease in 

weight gain. This effect may have occurred because they ate less food, or because they 

excreted more of the food they ate. The livers and kidneys of these animals were larger than 

normal, but not from any harmful effect. Other studies noted the presence of an extra rib in 

rat fetuses whose mothers were given very high dietary levels of diethyl phthalate, but this 

effect is not considered harmful by all scientists. 

Diethyl phthalate is not known to cause cancer in humans or animals. Unlike other phthalates 

such as di(2-ethylhexyl) phthalate, diethyl phthalate does not appear to affect the ability of 

male animals to father babies (see ATSDR toxicological profile for di[2-ethylhexyl] phthalate 

for more information on this chemical). However, a decrease occurred in the number of live 

babies born to female animals that were exposed to diethyl phthalate throughout their lives. 

Some birth defects occurred in newborn rats whose mothers received high doses 

(approximately 3 g/kg) of diethyl phthalate by injection during pregnancy. However, humans 

are not exposed to diethyl phthalate this way, and no information is available on whether this 

chemical can cause birth defects when given by mouth. 

Diethyl phrhalate can be mildly irritating when applied to the skin of animals. It can also be 

slightly irritating when put directly into the eyes of animals. We have no information on the 

health effects of diethyl phthalate when applied to the skin for long periods of time. For 

more information on the health effects of diethyl phthalate, please refer to Chapter 2. 

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

EXPOSED TO DIETHYL PHTHALATE? 

Chemical tests are available to determine diethyl phthalate levels in semen, fat, and kidney 

tissues. See Chapters 2 and 6 for more information. 
DIETHYL PHTHALATE 6 

1. PUBLIC HEALTH STATEMENT 

1.7 	 WHAT RECOMMENDATIONS HAS THE FEDERAL GOVERNMENT MADE TO 

PROTECT HUMAN HEALTH? 

The government has developed regulations and guidelines for diethyl phthalate. These are 

designed to protect the public from the possible harmful health effects of the chemical. 

Under laws that relate to Superfund sites, EPA has identified diethyl phthalate as a hazardous 

substance. This decision is based primarily on the large number of Superfund sites where 

diethyl phthalate is found. 

The Occupational Safety and Health Administration (OSHA) regulates levels of diethyl 

phthalate in the workplace. The maximum amount of diethyl phthalate allowed in workroom 

air during an 8-hour workday, 40-hour workweek, is 5 milligrams per cubic meter (mg/m3

). 

See Chapter 7 for more information on regulations and guidelines. The National Institute for 

Occupational Safety and Health (NIOSH) also recommends a similar maximum air 

concentration of 5 mg/m3 for workplace exposure. 

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 

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. 
DIETHYL PHTHALATE 7 

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 diethyl 

phthalate and a depiction of significant exposure levels associated with various adverse health effects. 

It contains descriptions and evaluations of studies and describes levels of significant exposure for 

diethyl phthalate based on toxicological studies and epidemiological investigations. 

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, reproductive, 

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

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

more). 

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

figure. The points in the figure showing no-observed-adverse-effect levels (NOAELs) or lowestobserved-adverse-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-users of the documents identify 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 
DIETHYL PHTHALATE 8 

2. HEALTH EFFECTS 

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

officials and project managers concerned with appropriate actions to take at hazardous waste sites may 

want information on levels of exposure associated with more subtle effects in humans or animals 

(LOAEL) or exposure levels below which no adverse effects (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 and 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. 

2.2.1 Inhalation Exposure 

No studies were located regarding the following health effects in humans or animals following 

inhalation exposure to diethyl phthalate. 

2.2.1.l Death 

2.2.1.2 Systemic Effects 

2.2.1.3 Immunological and Lymphoreticular Effects 
 

 

 

 

 

 

 

 

DIETHYL PHTHALATE 9 

2. HEALTH EFFECTS 

2.2.1.4 Neurological Effects 

2.2.1.5 Reproductive Effects 

2.2.1.6 Developmental Effects 

2.2.1.7 Genotoxic Effects 

Genotoxicity studies are discussed in Section 2.4. 

2.2.1.8 Cancer 

No studies were located regarding cancer in humans or animals following inhalation exposure to 

diethyl phthalate. 

2.2.2 Oral Exposure 

2.2.2.1 Death 

No studies were located regarding death in humans following oral exposure to diethyl phthalate. 

The lowest lethal doses of diethyl phthalate in rabbits and guinea pigs administered the compound by 

gavage were determined to be 4,000 and 5,000 mg/kg, respectively (Smyth and Smyth 1931). 

However, this study is limited in that only two to six animals were tested at each dose level and no 

control data were presented. Furthermore, neither the clinical signs exhibited by the animals nor the 

cause(s) of death were stated. No deaths were observed when diethyl phthalate was incorporated into 

the diet of mice for 2 weeks at doses of up to 6,500 mg/kg/day. Thus, based on this information, it 

would appear that diethyl phthalate is relatively nonlethal to orally exposed experimental animals. 

2.2.2.2 Systemic Effects 

No studies were located regarding dermal effects in humans or animals following oral exposure to 

diethyl phthalate. 
DIETHYL PHTHALATE 10 

2. HEALTH EFFECTS 

The highest NOAEL values and all reliable LOAEL values for systemic effects for each species and 

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

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

exposure to diethyl phthalate. Two-to-16-week dietary administration of diethyl phthalate, at 

concentrations up to 3,710 mg/kg/day, had no effect on the gross or microscopic pathology of the 

lungs or trachea in rats (Brown et al. 1978). 

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

following oral exposure to diethyl phthalate. Two-to-16-week dietary administration of diethyl 

phthalate, at concentrations up to 3,710 mg/kg/day, had no effect on the gross or microscopic 

pathology of the hearts or aorta in rats. Administration of 3,160 mg/kg/day to male rats resulted in a 

statistically significant (p<0.01) increase in heart weight (Brown et al. 1978). 

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

following oral exposure to diethyl phthalate. Two-to-16-week dietary administration of high 

concentrations of diethyl phthalate resulted in enlarged stomachs, small intestines, and/or caecums. No 

evidence of histological damage was found in any gastrointestinal tissue. The investigators did not 

consider the effects treatment-related (Brown et al. 1978). 

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

following oral exposure to diethyl phthalate. A statistically significant increase in erythrocyte counts 

was reported in male rats receiving 3,160 mg/kg/day (5% in diet) diethyl phthalate in the diet for 

6 weeks. However, this change was no longer apparent after 16 weeks of dietary administration. In 

addition, no treatment-related effects were noted in packed cell volume, reticulocyte counts, or 

leukocyte counts in male or female rats in this study (Brown et al. 1978). 






DIETHYL PHTHALATE 17 

2. HEALTH EFFECTS 

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

following oral exposure to diethyl phthalate. Two-to-l6-week dietary administration of diethyl 

phthalate, at concentrations up to 3,710 mg/kg/day, had no effect on the gross or microscopic 

pathology of skeletal muscle in rats (Brown et al. 1978). 

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

diethyl phthalate. A number of studies have reported increases in absolute and relative liver weights 

in animals administered up to 3,710 mg/kg/day diethyl phthalate in the diet for an acute exposure 

duration (Brown et al. 1978; Oishi and Hiraga 1980). However, in the absence of biochemical, 

functional, or histopathological evidence of liver damage, the toxicological significance of these 

changes in liver weight is not known. Only slight, but statistically significant, increases in liver 

weight, hepatic peroxisome, and hepatic catalase and camitine acetyltransferase activities occurred in 

rats administered 1,753 mg/kg/day diethyl phthalate in the diet for 3 weeks (Moody and Reddy 1978). 

These changes were minor compared to changes observed after dietary administration of 

di-(2-ethylhexyl)phthalate, di-(2-ethylhexyl)adipate, or di-(2-ethylhexyl)sebacate. Nevertheless, the 

observed changes are considered a less serious LOAEL and were used to derive an intermediateduration MRL of 6 mg/kg/day, as described in Section 2.4. 

Fatty degeneration and slight vacuolation were noted in the liver of some animals fed diethyl phthalate 

for up to 16 weeks (Brown et al. 1978). However, although no incidence data were provided, the 

investigators stated that these changes were not dose related. A dose-related increase in the incidence 

of congestion, cloudy swelling, and scant, moderate, or abundant glycogen was noted in guinea pigs 

administered 250-1,000 mg/kg/day diethyl phthalate in the feed for l-3 months (Smyth and Smyth 

1932). This study is limited, however, in that only two to four animals were tested at each dose. 

Based on the available information, it appears that while diethyl phthalate can induce an increase in 

relative liver weight in experimental animals, the absence of any treatment-related biochemical, 

functional, or histopathological changes in the liver suggests that the increase in liver weight may be 

due to exposure to high oral concentrations rather than to a direct toxic effect of diethyl phthalate. 
DIETHYL PHTHALATE 18 

2. HEALTH EFFECTS 

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

diethyl phthalate. 

An increase in relative kidney weight was observed in male rats administered 5% diethyl phthalate in 

the diet for 2 weeks, and in male and female rats administered 5% diethyl phthalate in the diet for 

16 weeks (Brown et al. 1978). The approximate daily intakes (listed by the authors) were 

3,160 mg/kg/day for male rats and 3,710 mg/kg/day for female rats. There was no evidence that these 

organ weight changes were accompanied by any biochemical, functional, or histopathological renal 

damage. Therefore, the toxicological significance of this change in kidney weight is not known. 

Congestion, cloudy swelling of the tubules, and desquamation were noted in guinea pigs administered 

250-1,000 mg/kg/day diethyl phthalate in the feed for l-3 months (Smyth and Smyth 1932). This 

study is limited, because only three or four animals were tested at each dose. 

Based on the available information, it appears that while diethyl phthalate can induce an increase in 

relative kidney weight in experimental animals, the absence of any reliable treatment-related 

biochemical, functional, or histopathological changes in the kidney suggests that the increase in kidney 

weight was probably not due to a direct toxic effect of diethyl phthalate. 

Endocrine Effects. No studies were located regarding endocrine effects in humans following oral 

exposure to diethyl phthalate. Two-to-16-week dietary administration of diethyl phthalate, at 

concentrations up to 3,710 mg/kg/day, had no effect on the gross or microscopic pathology of the 

pituitary, adrenals, thyroid, or pancreas in rats. Relative organ weights of the adrenals, pituitary, and 

thyroid were slightly to moderately elevated at 3,160 mg/kg/day in males (Brown et al. 1978). 

Ocular Effects. No studies were located regarding ocular effects in humans following oral exposure 

to diethyl phthalate. Two-to-16-week dietary administration of diethyl phthalate, at concentrations up 

to 3,710 mg/kg/day, had no effect on the gross or microscopic pathology of the eye (Brown et al. 

1978). 
 

 

 

DIETHYL PHTHALATE 19 

2. HEALTH EFFECTS 

Body Weight. No studies were located regarding body weight changes in humans following oral 

exposure to diethyl phthalate. 

A number of studies have reported significant (>l0%) decreases in body weight gain in experimental 

animals after acute- and intermediate-duration dietary exposure (Brown et al. 1978; Lamb et al. 1987; 

NTP 1984). In at least one study, the results of a concurrent paired-feeding experiment indicated that 

the inhibition was primarily attributable to lower food consumption and/or poorer food utilization, 

rather than to a direct toxic action of diethyl phthalate (Brown et al. 1978). In a continuous breeding 

study with mice, dietary administration of the equivalent of 3,250 mg/kg/day was associated with a 

47% weight gain inhibition (Lamb et al. 1987). 

2.2.2.3 Immunological and Lymphoreticular Effects 

No studies were located regarding immunological or lymphoreticular effects in humans following oral 

exposure to diethyl phthalate. Two-to-16-week dietary administration of diethyl phthalate, at 

concentrations up to 3,710 mg/kg/day, had no effect on the gross or microscopic pathology of 

(unspecified) lymph nodes or the thymus (Brown et al. 1978). 

2.2.2.4 Neurological Effects 

No studies were located regarding neurological effects in humans following oral exposure to diethyl 

phthalate. Two-to-16-week dietary administration of diethyl phthalate, at concentrations up to 

3,710 mg/kg/day, had no effect on the gross or microscopic pathology of the brain or the sciatic nerve 

(Brown et al. 1978). Exposure to 3,160 mg/kg/day (males) or 3,710 mg/kg/day (females) resulted in 

increased relative brain weights (Brown et al. 1978). 

2.2.2.5 Reproductive Effects 

No studies were located regarding reproductive effects in humans following oral exposure to diethyl 

phthalate. 
DIETHYL PHTHALATE 20 

2. HEALTH EFFECTS 

Several investigators have studied the effects of diethyl phthalate on male reproductive function in rats 

since other phthalic acid esters have been shown to be toxic to the male reproductive system (ATSDR 

1989; Foster et al. 1980, 1983; Gray and Butterworth 1980; Oishi and Hiraga 1980). Testicular and 

accessory gland weight and histopathology were unaffected by treatment of male rats with diethyl 

phthalate at doses up to 1,600 mg/kg/day (Foster et al. 1980; Gray and Butterworth 1980; Oishi and 

Hiraga 1980). In addition, diethyl phthalate had no effect on progesterone binding to testes 

microsomes, testicular cytochrome P-450 content, or testicular steroidogenic enzyme activity, whereas 

other phthalates known to cause testicular toxicity have induced changes in these parameters (Foster et 

al. 1983). The authors concluded that the lack of effect on these parameters is consistent with the lack 

of morphological effects on the testes reported in other studies. 

Acute administration of 2,000 mg/kg/day diethyl phthalate produced ultrastructural evidence of Leydig 

cell mitochondrial swelling, and both focal dilatation and vesiculation of the smooth endoplasmic 

reticulum (Jones et al. 1993). These findings are considered a less serious LOAEL and were used to 

derive an acute oral MRL of 7 mg/kg/day (see Section 2.4). 

In a continuous breeding study in CD-l mice, dietary administration of 2.5% diethyl phthalate (>99% 

pure) (3,250 mg/kg/day) produced physiological effects in F1 parental animals and significantly 

decreased the number of live pups per litter (Lamb et al. 1987). No adverse effects on the physiology, 

fertility, or reproductive performance of the F0 generation animals were observed. The F0 mice were 

fed diets containing the test compound at concentrations of 0, 325, 1,625, or 3,250 mg/kg daily during 

premating, mating, gestation, and lactation; the F1 generation animals received 0 or 3,250 mg/kg/day 

on the same regimen. 

The parental toxicity in the F1 generation was evidenced by a significant decrease in body weight, 

increased prostate weight in males, and increased liver and pituitary weights in females. However, 

histological findings in the liver and pituitary were not reported, rendering the toxicological 

significance of a change in these organ weights uncertain. Although a significant decrease in sperm 

concentration occurred in the males, no adverse effect on the fertility was observed. The total number 

of live pups per litter in the F1 generation was significantly lower by 14% in the test group compared 

to the controls. The study limitations include a lack of data on the histopathological findings of the 
 

DIETHYL PHTHALATE 21 

2. HEALTH EFFECTS 

tissues and failure to assess the effects of the test compound on the F1 generation at the two lower 

doses. Data on the F, generation showed an increase in the number of live pups per litter at the low 

doses. As a result, no NOAEL was established. 

Administration of up to a dose equivalent of 3,710 mg/kg/day diethyl phthalate was associated with no 

gross or microscopic evidence of histopathological damage to the gonads, uterus, or the prostate and 

seminal vesicles of rats. Relative testes weights were significantly elevated at a dose equivalent of 

3,160 mg/kg/day (Brown et al. 1978). 

The highest NOAEL value and the LOAEL value for reproductive effects for each species and 

duration category are recorded in Table 2-l and plotted in Figure 2-1. 

2.2.2.6 Developmental Effects 

No studies were located regarding developmental effects in humans following oral exposure to diethyl 

phthalate. 

A study in mice reported no significant evidence of maternal toxicity or neonatal developmental effects 

due to oral administration of 4,500 mg/kg/day on gestation days 6-13 (Hardin et al. 1987). Newborn 

mice were evaluated for survival, birth weight, and weight gain. A limitation of this study was that 

these results were determined by use of a proposed short-term in vivo developmental toxicity assay, 

and no comparison of this method to conventional assays was available. In rats, dietary administration 

of up to 2.5% diethyl phthalate (1,910 mg/kg/day) produced no embryonic or fetotoxic effects. At a 

dietary level of 5% (3,210 mg/kg/day), treated embryos had an increased number of skeletal variations, 

particularly rudimentary (supernumerary) ribs (Field et al. 1993). However, the significance of this 

finding is obscured by the high incidence of skeletal variations in the controls and the reduced food 

and water consumption of the high-dose dams early in gestation. 

The NOAEL value and LOAEL value for developmental effects after acute exposure to diethyl 

phthalate are recorded in Table 2-1 and plotted in Figure 2-l. 
 

 

 

 

 

DIETHYL PHTHALATE 22 

2. HEALTH EFFECTS 

2.2.2.7 Genotoxic Effects
 

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

diethyl phthalate.
 

Genotoxicity studies are discussed in Section 2.4.
 

2.2.2.8 Cancer
 

No studies were located regarding cancer in humans or animals following oral exposure to diethyl 

phthalate. 

2.2.3 Dermal Exposure 

2.2.3.1 Death 

No studies were located regarding death in humans following dermal exposure to diethyl phthalate. 

At daily application doses of up to 100 μL (mice) or 300 μL (rats), equivalent to 772 mg/kg/day 

(mice) and 855 mg/kg/day (rats), diethyl phthalate did not produce an increased mortality incidence 

when administered 5 days per week for 2 years (NTP 1993 [board draft]). 

2.2.3.2 Systemic Effects 

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

exposure to diethyl phthalate. 

The highest NOAEL values and all reliable LOAEL values for systemic effects for each species and 

duration category are recorded in Table 2-2. 




DIETHYL PHTHALATE 27 

2. HEALTH EFFECTS 

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

dermal exposure to diethyl phthalate. 

Repeated dermal administration of diethyl phthalate had no adverse effects on lung histopathology in 

rats or mice exposed for 4 weeks or 2 years (NTR 1993 [board draft]). 

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

following dermal exposure to diethyl phthalate. 

Repeated dermal administration of diethyl phthalate had no adverse effects on heart histopathology in 

rats or mice exposed for 4 weeks or 2 years (NTP 1993 [board draft]). 

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

following dermal exposure to diethyl phthalate. 

Repeated dermal administration of diethyl phthalate had no adverse effects on the histopathology of 

the esophagus, gallbladder (mouse only), large intestine, small intestine, stomach, or bladder in rats or 

mice exposed for 4 weeks or 2 years (NTP 1993 [board draft]). 

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

following dermal exposure to diethyl phthalate. 

The results of studies in rats and mice indicated no adverse effects on standard hematological 

parameters after repeated dermal application of 100% diethyl phthalate (NTR 1993 [board draft]). 

Hepatic Effects. No studies were located regarding hepatic effects in humans following dermal 

exposure to diethyl phthalate. 
DIETHYL PHTHALATE 28 

2. HEALTH EFFECTS 

Repeated dermal administration of diethyl phthalate had no adverse effects on liver histopathology in 

rats or mice exposed for 4 weeks or 2 years (NTP 1993 [board draft]). In 4-week studies, 

administration of diethyl phthalate did result in increased relative liver weights in both sexes of rats 

and in female mice. However, no adverse effects on clinical indices of liver function were noted 

(NTP 1993 [board draft]). 

Renal Effects. No studies were located regarding renal effects in humans following dermal exposure 

to diethyl phthalate. 

Repeated dermal administration of diethyl phthalate had no adverse effects on kidney histopathology in 

rats or mice exposed for 4 weeks or 2 years (NTP 1993 [board draft]). In 4-week studies, 

administration of diethyl phthalate did result in increased relative kidney weights in both sexes of rats. 

However, no adverse effect on clinical indices of kidney function were noted (NTP 1993 [board 

draft]). 

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

exposure to diethyl phthalate. 

Diethyl phthalate was shown to be very slightly or slightly irritating when applied repeatedly to the 

intact or abraded skin, respectively, of an unidentified species (Dow Chemical 1952). However, the 

criteria to judge irritation were not specified in this study, and none of the protocol details were 

provided. Other data indicate that chronic dermal diethyl phthalate administration is associated with 

mild, nonadverse dermal acanthosis in rats (NTP 1993 [board draft]). One study reported that diethyl 

phthalate caused intradermal irritation evidenced by the presence of inflammation at the site of 

injection in the skin.of rabbits (Galley et al. 1966). 

Ocular Effects. No studies were located regarding ocular effects in humans following dermal 

exposure to diethyl phthalate. 
DIETHYL PHTHALATE 29 

2. HEALTH EFFECTS 

Ocular irritation tests conducted in rabbits indicate that diethyl phthalate is not a primary ocular irritant 

(Dear and Jassup 1978; Lawrence et al. 1975). The compound caused minimal irritation when applied 

to the eye without washing, and was practically non-irritating when the eye was washed after 

instillation (Dear and Jassup 1978). 

Body Weight Effects. No studies were located regarding body weight effects in humans following 

dermal exposure to diethyl phthalate. 

In 2-year rat dermal toxicity studies, diethyl phthalate produced slight body weight gain decrements in 

male and female rats. The equivalent doses administered were 285 and 855 mg/kg/day. Diethyl 

phthalate had no effect on body weight gain in 4-week rat and mouse studies or in 2-year mouse 

studies (NTP 1993 [board draft]). 

2.2.3.3 Immunological and Lymphoreticular Effects 

In a factory that produces shoes from polyvinyl chloride granulate (which contains a compound the 

authors called dioctyl phthalate, but which is probably di-[2-ethylhexyllphthalate), 30 workers with 

dermatitis and 30 workers without dermatitis were patch tested with diethyl phthalate and compared 

with 30 controls that had no known exposure to polyvinyl chloride or phthalates (Vidovic and Kansky 

1985). One worker of the 30 with dermatitis and 1 of the 30 without dermatitis responded positively 

with an allergic contact response to diethyl phthalate. None of the controls had a positive response. 

The authors concluded that the results in the exposed worker populations indicate that the phthalates 

are sensitizers, and that the positive reaction to diethyl phthalate was most likely due to crosssensitization with dioctyl phthalate since very little diethyl phthalate is present in polyvinyl chloride 

(Vidovic and Kansky 1985). In a skin patch test designed to maximize sensitization, none of 

25 healthy adult volunteers showed a positive reaction to diethyl phthalate (Greif 1967). 

The NOAEL and LOAEL values for immunological or lymphoreticular effects in humans following 

dermal exposure are recorded in Table 2-2. 
 

 

 

 

DIETHYL PHTHALATE 30 

2. HEALTH EFFECTS 

Repeated dermal administration of diethyl phthalate had no adverse effects on the histopathology of 

the spleen, thymus, or lymph nodes or on thyroid weight in rats or mice exposure for 4 weeks or 2 

years (NTP 1993 [board draft]). 

2.2.3.4 Neurological Effects 

No studies were located regarding neurological effects in humans following dermal exposure to diethyl 

phthalate. In 4-week and 2-year studies with rats and mice, diethyl phthalate had no adverse effect on 

the histopathology or weight of the brain (NTP 1993 [board draft]). These NOAEL values are 

recorded in Table 2-2. 

2.2.3.5 Reproductive Effects 

No studies were located regarding reproductive effects in humans following dermal exposure to diethyl 

phthalate. 

In 4-week and 2-year studies with rats and mice, diethyl phthalate had no adverse effect on the 

histopathology of male or female reproductive organs (NTP 1993 [board draft]). These NOAEL 

values are recorded in Table 2-2. 

2.2.3.6 Developmental Effects 

No studies were located regarding developmental effects in humans or animals following dermal 

exposure to diethyl phthalate. 

2.2.3.7 Genotoxic Effects 

No studies were located regarding genotoxic effects in humans or animals following dermal exposure
 

to diethyl phthalate.
 

Genotoxicity studies are discussed in Section 2.4.
 
 

 

 

 

 

DIETHYL PHTHALATE 31 

2. HEALTH EFFECTS 

2.2.3.8 Cancer 

No studies were located regarding cancer in humans following dermal exposure to diethyl phthalate. 

The results of a board draft study indicated that male and female rats receiving 100 or 300 μL diethyl 

phthalate (approximately 285 mg/kg/day or 855 mg/kg/day), applied to the intrascapular skin 5 days 

per week for 2 years, did not develop any evidence of carcinogenic activity. Equivocal evidence of 

carcinogenicity was found in both sexes of mice dermally exposed to up to 30 μL diethyl 

phthalate/day, 5 days per week for 2 years. The incidences of combined hepatocellular 

adenoma/carcinoma in the male mice dosed with 0, 7.5, 15, and 30 μL/day (corresponding to 0, 193, 

386, and 772 mg/kg/day) were 9/50, 14/50, 14/50, and 18/50, respectively. The corresponding 

incidences in the female mice were 7/50, 16/51, 19/50, and 12/50, respectively (NTP 1993 [board 

draft]). Because of the absence of a dose-response relationship, these data are not adequate for the 

determination of a cancer effect level. Finally, diethyl phthalate had no tumor initiation or promoting 

capability in l-year mouse studies (NTP 1993 [board draft]). 

2.3 TOXICOKINETICS 

2.3.1 Absorption 

2.3.1.l Inhalation Exposure 

No studies were located regarding absorption of diethyl phthalate in humans or animals following 

inhalation exposure. 

2.3.1.2 Oral Exposure 

No studies were located regarding the absorption of diethyl phthalate in humans or animals following 

oral exposure. 
DIETHYL PHTHALATE 32 

2. HEALTH EFFECTS 

2.3.1.3 Dermal Exposure 

No in vivo studies were located regarding the absorption of diethyl phthalate in humans following 

dermal exposure. The absorption of diethyl phthalate has been measured in vitro through human (from 

abdominal skin) and rat (from dorsal region) epidermal membranes set up in flow-through diffusion 

cells (Hotchkiss et al. 1992; Mint et al. 1992; Scott et al. 1987). The extent of percutaneous 

absorption 72 hours after application to intact, unoccluded human skin was 4.8% of the applied dose 

(Hotchkiss et al. 1992). Application of diethyl phthalate to the epidermal membranes for 8 hours 

resulted in a lag phase of absorption followed by a linear phase. Steady-state absorption rates 

determined for diethyl phthalate for human and rat epidermal membranes showed that diethyl phthalate 

was absorbed more slowly through human epidermal membranes than through rat epidermal 

membranes. For humans, the steady-state absorption rate for diethyl phthalate was 

1.27 ± 0.11 μg/cm2

/hour. The steady-state absorption rate for rats was 41.37 ± 9.28 μg/cm2/hour. The 

human lag time was 6 hours while the lag time for rats was 1 hour. Rat epidermal membrane was 

more permeable to diethyl phthalate than the human epidermal membrane. The permeability constant 

of diethyl phthalate for humans was 1.14x10-5 cm/hour and for rats it was 37x10-5 cm/hour. Dermal 

application of diethyl phthalate to the human epidermis produced no more skin damage than dermal 

application of water did. The authors reported that the differences in absorption between the human 

and rat membranes are to be expected because of the complex differences in the biochemical and 

structural composition of the two membranes (Scott et al. 1987). These results have been confirmed 

by additional in vitro studies that reported 72-hour absorptions of 36.9% and 5.6% of the applied 

doses in unoccluded rat and human skin preparations, respectively (Mint et al. 1992). 

In rodents, diethyl phthalate is absorbed following dermal exposure. The extent of dermal absorption 

of diethyl phthalate -was studied using a single dermal application of radiolabeled (14C) diethyl 

phthalate (5-8 mg/cm2

) to the clipped skin of male rats (Elsisi et al. 1989). The amount of 14C 

radioactivity excreted was taken as an index of the percutaneous absorption. Twenty-four percent of 

the dose was excreted in the first 24 hours. The rate of excretion then decreased so that only 11% of 

the dose was excreted in the next 24 hours. A cumulative total of 50% of the dose was excreted by 

7 days, with urinary excretion volumes exceeding fecal volumes (quantitative data not provided). 
DIETHYL PHTHALATE 33 

2. HEALTH EFFECTS 

Seven days after exposure, 34% of the label was in the area of application and 4.8% was in the plastic 

cap used to protect the application site. Seven other phthalate esters were also tested in the study: 

dimethyl, dibutyl, dihexyl, di(2-ethylhexyl), diisodecyl, and benzyl butyl phthalates. The results 

indicated that the length of the side chain affected the dermal uptake of phthalate esters. Skin 

absorption was inversely proportional to the side chain length-the longer the chain (more than four 

carbons), the lesser the dermal uptake (Elsisi et al. 1989). 

2.3.2 Distribution 

2.3.2.1 Inhalation Exposure 

No studies were located regarding the distribution of diethyl phthalate in humans or animals following 

inhalation exposure. 

2.3.2.2 Oral Exposure 

No studies were located regarding the distribution of diethyl phthalate in humans or animals following 

oral exposure. 

2.3.2.3 Dermal Exposure 

No studies were located regarding the distribution of diethyl phthalate in humans following dermal 

exposure. 

Results of an experiment in which rats were exposed dermally to a single application of 14C-diethyl 

phthalate (5-8 mg/cm2

) showed that distribution of the radioactivity is wide but that diethyl phthalate 

and/or its metabolites are not likely to accumulate to any great extent in tissues (Elsisi et al. 1989). 

Very little of the 14C radioactivity was found in the tissues 1 week after exposure to diethyl phthalate. 

The amounts of label found in the brain, lung, liver, spleen, small intestine, kidney, testis, spinal cord, 

and blood were each less than 0.5% of the administered dose. Adipose tissue, muscle, and skin 

accounted for 0.03%, 0.14%, and 0.06% of the administered 14C radioactivity, respectively. Thirty­
DIETHYL PHTHALATE 34 

2. HEALTH EFFECTS 

four percent remained in the area of application, and 4.8% remained in the plastic cap used to protect 

the application site (Elsisi et al. 1989). 

2.3.2.4 Other Routes of Exposure 

No studies were located regarding the distribution of diethyl phthalate in humans following exposure 

by other routes. 

14C-diethyl phthalate was administered intraperitoneally (2,800 mg/kg) to pregnant rats on either day 5 

or day 10 of gestation (Singh et al. 1975). Results showed that radioactivity from 14C-diethyl 

phthalate is transmitted across the placenta from mother to fetus for at least 15 days postinjection. 

14C radioactivity was widely distributed and was detected (<l%) in maternal blood, placenta, amniotic 

fluid, and developing fetuses at all gestational stages investigated (Singh et al. 1975). 

2.3.3 Metabolism 

No in vivo studies were located regarding the metabolism of diethyl phthalate in humans or animals. 

A diagram of the metabolic pathway of diethyl phthalate is not provided since so few data were 

available. The following elucidation of the metabolism of diethyl phthalate is based on in vitro 

studies, and the studies cited may not represent the in vivo situation either qualitatively or 

quantitatively. 

The first step of metabolism involves hydrolysis to a monoester derivative. This was seen in the in 

vitro metabolism of 14C-diethyl phthalate (5-mmol/L solution) by hepatic and small intestine 

preparations from a rodent (rat), a nonrodent (ferret), and a nonhuman primate (baboon)JLake et al. 

1977). Hepatic postmitochondrial supematant and intestinal preparations from the rat, baboon, and 

ferret were able to catalyze the hydrolysis of diethyl phthalate to its monoester derivative. Enzyme 

activity was expressed as micromoles of product formed per hour per gram of liver (μmol/hour/g) or 

per milligram of intestinal mucosal cell protein (μmol/hour/mg). Quantitative species differences were 

observed in the hepatic and intestinal studies. In the hepatic studies, diethyl phthalate hydrolase 
DIETHYL PHTHALATE 35 

2. HEALTH EFFECTS 

activity decreased in the following order: baboon (516 μmol/hour/g) > rat (231 μmol/hour/g) > ferret 

(45.9 μmol/hour/g). In the intestinal preparation, diethyl phthalate hydrolase activity decreased in the 

same order: baboon (4.33 μmol/hour/mg) > rat (0.648 μmol/hour/mg) > ferret (0.053 μmol/hour/mg). 

Studies were also performed with samples of human duodenum and jejunum tissues. As with the three 

animal species, human intestinal preparations were also active in the metabolism of diethyl phthalate. 

The results obtained with human intestinal preparations were expressed as nanomoles of product 

formed per hour per milligram of intestinal protein (nmol/hour/mg). In the human intestinal 

preparation, the diethyl phthalate hydrolase activity was 31.2-153 nmol/hour/mg in the duodenum and 

129 nmol/hour/mg in the jejunum. Similarly, of the tissues from three rat and one human studied in 

vitro, the rat small intestine hydrolyzed the greatest amount (36.4%) of diethyl phthalate in a 16-hour 

period (Rowland et al. 1977). These results show a qualitative species similarity in the hydrolytic 

metabolism of diethyl phthalate in humans, a rodent, a nonrodent, and a nonhuman primate. 

In both the Lake et al. (1977) and Rowland et al. (1977) studies, attempts were made to identify the 

products of hydrolysis. In all instances, only one metabolic product was formed that had matching 

chromatographic properties in thin-layer chromatographic tests using two different solvent systems. 

These results showed that diethyl phthalate is mono-de-esterified by the liver and intestines. Since 

diethyl phthalate was hydrolyzed by rat, baboon, ferret, and human intestinal preparations, the 

investigators suggested that orally ingested diethyl phthalate would most probably be absorbed from 

the gut of rats, baboons, ferrets, and humans as the corresponding monoester derivative. Any toxic 

effects of orally ingested diethyl phthalate would more likely be governed by the properties of the 

corresponding monoester and/or ethanol rather than by intact diethyl phthalate (Lake et al. 1977). The 

extent of the hydrolysis of diethyl phthalate under in vivo conditions, however, has not been 

established; consequently, the potential effect of intact diethyl phthalate must also be considered. 

Although no data were located specifically regarding the complete in vivo metabolism of diethyl 

phthalate, data concerning alkyl phthalic acid esters in general suggest that the extent of hydrolysis 

depends on the route of administration. Hydrolysis of other phthalate esters is extensive after oral 

ingestion, but is also dose-related such that, at higher doses, a greater proportion of the intact diester is 

absorbed (Albro and Laenhar 1989; Pollack et al. 1985). Furthermore, once formed, the monoester 
 

 

 

DIETHYL PHTHALATE 36 

2. HEALTH EFFECTS 

derivative can be further hydrolyzed in vivo to phthalic acid and excreted or conjugated to glucuronide 

and excreted; the terminal or next-to-last carbon atom in the monoester can be oxidized to an alcohol 

and excreted; or the alcohol can be successively oxidized to an aldehyde, ketone, or carboxylic acid 

and excreted (Albro and Moore 1974; Albro et al. 1973; EPA 1989; Kluwe 1982). 

In another in vitro study, diethyl phthalate inhibited uridine diphosphate glucuronyl transferase 

(UDPGT) activity of rat liver microsomal preparations (Gollamudi et al. 1985). UDPGT is an 

important enzyme involved in the Phase II conjugation and detoxication of many endogenous and 

xenobiotic substances. After incubation of the microsomes for 3 minutes with a 1.35-mmol/L solution 

of diethyl phthalate, p-nitrophenol-glucuronyl transferase activity was significantly inhibited (33%). 

Incubation for 6 minutes resulted in 29% inhibition by a 1.35-mmol/L solution of diethyl phthalate. 

Diethyl phthalate had no effect on rat liver N-acetyltransferase and microsomal cytochrome P-450 in 

vitro (Gollamudi et al. 1985). 

2.3.4 Excretion 

2.3.4.1 Inhalation Exposure 

No studies were located regarding the excretion of diethyl phthalate or its metabolites by humans or 

animals following inhalation exposure. 

2.3.4.2 Oral Exposure 

No studies were located regarding the excretion of diethyl phthalate or its metabolites by humans or 

animals following oral exposure. 

2.3.4.3 Dermal Exposure 

No studies were located regarding the excretion of diethyl phthalate or its metabolites by humans 

following dermal exposure. 
DIETHYL PHTHALATE 37 

2. HEALTH EFFECTS 

Male rats, exposed to a single dermal application of 14C-diethyl phthalate (5-8 mg/cm2), excreted 24% 

of the administered dose in the urine and 1% of the dose in feces within 24 hours (Elsisi et al. 1989). 

Total recovery of the radiolabel in the urine and feces after 7 days was about 50%. No attempt was 

made to characterize the metabolites found in the urine (Elsisi et al. 1989). 

2.3.4.4 Other Routes of Exposure 

No studies were located regarding the excretion of diethyl phthalate or its metabolites by humans 

following exposure by other routes. 

14C-diethyl phthalate (2,800 g/kg) was administered intraperitoneally to pregnant rats on either day 5 or 

day 10 of gestation (Singh et al. 1975). The results showed that radioactivity in the maternal blood 

increased, reaching a peak during the first 24 hours. The concentration of radioactivity then 

diminished quickly. A similar pattern was observed in amniotic fluid and fetal tissues. The reduction 

in concentration of 14C from these tissues as a function of time was found to fit a first-order excretion 

curve. From this model curve, the half-life was calculated to be 2.22 days for diethyl phthalate. 

Although the exact chemical nature of the radioactive compounds was not determined, the 

investigators reported that some of them were probably mixtures of parent compound, monoester, and 

phthalic acid (Singh et al. 1975). 

2.3.5 Mechanisms of Action 

No data regarding the absorption or distribution of diethyl phthalate, after oral or inhalation 

administration, are available, and the results of dermal studies are inadequate to determine a 

mechanism of action. 

2.4 RELEVANCE TO PUBLIC HEALTH 

Populations living in areas surrounding hazardous waste sites may be exposed to diethyl phthalate 

primarily via ingestion of drinking water. Another possible route of exposure is dermal contact with 

contaminated water. For the general population (i.e., including individuals not living in the vicinity of 
DIETHYL PHTHALATE 38 

2. HEALTH EFFECTS 

hazardous waste sites), most exposure to diethyl phthalate occurs by the use of consumer products 

containing it; diethyl phthalate is listed as an ingredient in at least 67 cosmetic formulations at 

concentrations ranging from ≤0.1% to 50%, although most products contain less than 1% diethyl 

phthalate. The products may be applied to skin, eyes, hair, and nails, and exposure of the mucous 

membranes and the respiratory tract can occur. Exposure may be frequent (several times a day) or of 

prolonged duration (years). Exposure can also occur in people receiving medical treatments that 

involve the use of polyvinyl chloride tubing from which diethyl phthalate can leach. Exposure of the 

general population can also occur by ingestion of contaminated foods into which diethyl phthalate has 

leached from packaging materials, ingestion of contaminated seafood, or drinking contaminated water. 

Occupational exposure to diethyl phthalate can occur in industrial facilities where diethyl phthalate is 

used in the manufacture of plastics or consumer products. 

The liver may be the only target organ of diethyl phthalate exposure. Very mild hepatic effects are 

observed only after administration of extremely high doses. Otherwise, the only effects reported in 

animals after acute- and intermediate-duration oral exposure to this compound were death (acute 

exposure only), decreases in body weight gain, and organ weight changes that were not accompanied 

by any biochemical, functional, or histopathological evidence of organ injury. Diethyl phthalate is a 

mild skin irritant in animals and has been reported to cause minimal ocular irritation. In a twogeneration 

continuous breeding dietary study in mice, the only effect observed other than a decrease in 

body weight gain was a reduction in the number of live fetuses born to F, parents. Data on the effects 

of diethyl phthalate following parenteral administration to experimental animals do not provide any 

additional indication of the target organs of toxicity for this compound. While skeletal abnormalities 

(primarily elongated and fused ribs, abnormal or incomplete skull bones, and incomplete or missing 

tail bones) and increased resorptions were observed following intraperitoneal administration of high 

doses of diethylphthalate to pregnant rats, no such effects were observed in mice administered the 

compound orally during gestation. No data are available on the carcinogenicity of diethyl phthalate, 

and in vitro genotoxicity studies gave equivocal, although mostly negative, results. 

In vitro studies suggest that diethyl phthalate inhibits mitochondrial respiration in hepatic microsomes 

by interfering with electron transfer (Haubenstricker et al. 1990; Inouye et al. 1978). While this 
DIETHYL PHTHALATE 39 

2. HEALTH EFFECTS 

finding provides a possible mechanism of action for toxic effects of diethyl phthalate, no functional 

evidence of mitochondrial impairment have been noted in in vivo studies. 

Minimal Risk Levels for Diethyl Phthalate 

Inhalation 

No inhalation MRLs were derived for diethyl phthalate. The only known inhalation study in either 

humans or animals was conducted in an occupational cohort exposed to vapors from organic solvents 

and welding fumes of cellulose acetate, which contained 30% diethyl phthalate (Beving et al. 1990). 

This study was limited because of the small cohort size, co-exposure to other contaminants, 

inappropriate control data, and little exposure information. 

Oral 

•	 An MRL of 7 mg/kg/day has been derived for acute oral exposure to diethyl phthalate. This 

MRL is based on a reproductive study (Jones et al. 1993) in which rats had Leydig cell 

ultrastructural changes after receiving 2,000 mg/kg/day diethyl phthalate for 2 days by gavage. 

This result receives support from findings of decreased testosterone concentrations in diethyl 

phthalate-treated male rats (Oishi and Hiraga 1980). Furthermore, other investigators (Field et al. 

1993) derived a developmental NOAEL of 1,910 mg/kg/day in rats. The acute oral MRL is 

based on the LOAEL of 2,000 mg/kg/day, divided by an uncertainty factor of 300 (3 for the 

conversion of a minimal LOAEL to a NOAEL, 10 for interspecies extrapolation, and 10 for the 

protection of sensitive humans). 

•	 An MRL of 6 mg/kg/day has been derived for intermediate-duration oral exposure to diethyl 

phthalate. This value is based on a minimal LOAEL of 1,753 mg/kg/day for peroxisomal 

proliferation, slightly elevated liver weight, and changes in hepatic enzyme activities in male rats 

(Moody and Reddy 1978). The study receives support from a 13-week mouse dietary study in 
DIETHYL PHTHALATE 40 

2. HEALTH EFFECTS 

which the dose equivalent of 1,625 mg/kg/day was the highest NOAEL for body weight gain 

deficits (Lamb et al. 1987). The LOAEL was divided by an uncertainty factor of 300 (3 for the 

conversion of a minimal LOAEL to a NOAEL, 10 for interspecies extrapolation, and 10 for 

interindividual variation) to arrive at the MRL. 

The database was not adequate for determination of a chronic oral MRL for diethyl phthalate. 

Death. No studies were located regarding death in humans after exposure to diethyl phthalate. 

Minimal lethal doses of diethyl phthalate have been estimated for several species of experimental 

animals following both oral and parenteral administration. These doses range from 1,000 to 

4,000 mg/kg (intraperitoneal administration) in rats, rabbits, guinea pigs, and mice and from 4,000 to 

5,000 mg/kg (oral administration) in rabbits and guinea pigs (Smyth and Smyth 1931). LD50 data 

were available only for parenteral routes of exposure; the intraperitoneal LD50 has been reported to 

range from 2,830 mg/kg in the mouse (Calley et al. 1966) to 8,324 mg/kg in the rat (Singh et al. 1971, 

1972, 1973). 

Although available information is insufficient to determine whether exposure to diethyl phthalate in the 

vicinity of hazardous waste sites could produce death in humans, its widespread use in cosmetic 

formulations without apparent adverse effects and its virtual lack of toxic effects in animal studies 

suggest that it is not likely to be associated with death at the levels present in the vicinity of hazardous 

waste sites. 

Systemic Effects 

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

following inhalation exposure to diethyl phthalate or in humans following oral or dermal exposure to 

diethyl phthalate. The results of oral and dermal studies in laboratory animals suggest that the 

respiratory system is not a target tissue after high dose administration of diethyl phthalate (Brown et 

al. 1978; NTP 1993 [board draft]). 
DIETHYL PHTHALATE 41 

2. HEALTH EFFECTS 

A transient 71% decrease in respiratory rate was observed in rabbits administered a total intravenous 

dose of 100 mg/kg diethyl phthalate over a 2-3-minute period (Calley et al. 1966). Respiratory rate 

returned to baseline within 5 minutes. The mechanism for this effect on respiratory rate is not known. 

This effect should not be considered relevant to human exposure situations because diethyl phthalate 

was administered in a bolus intravenous injection, which is not an anticipated human exposure. 

Histopathological evaluation revealed no evidence of irritation in the lungs of mice given a single 

intraperitoneal injection of 2,464 mg/kg diethyl phthalate (Lawrence et al. 1975), or any 

histopathological changes in the lungs of rodents dermally administered up to 300 μL daily in a 

chronic study (NTP 1993 [board draft]). No change in lung weight was noted in mice administered 

125 mg/kg diethyl phthalate by daily intraperitoneal injection for 6 weeks (Calley et al. 1966). Effects 

seen after parenteral administration may not be relevant to human exposure. 

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

animals following inhalation exposure to diethyl phthalate or in humans following oral or dermal 

exposure to diethyl phthalate. The results of oral and dermal studies in laboratory animals suggest that 

the cardiovascular system is not a target tissue after high dose administration of diethyl phthalate 

(Brown et al. 1978; NTP 1993 [board draft]). 

A transient 22% decrease in blood pressure was observed in rabbits administered a total intravenous 

dose of 100 mg/kg diethyl phthalate over a 2-3-minute period (Calley et al. 1966). Blood pressure 

gradually returned to baseline levels. The mechanism for this effect on blood pressure is not known. 

This effect should not be considered relevant to human exposure situations because diethyl phthalate 

was administered in a bolus intravenous injection, which is not an anticipated human exposure route. 

Histopathological evaluation revealed no evidence of treatment-related effects in the hearts of mice 

given a single intraperitoneal injection of 2,464 mg/kg diethyl phthalate (Lawrence et al. 1975), or any 

histopathological changes in the hearts of rodents dermally administered up to 300 μL daily in a 

chronic board draft study (NTP 1993). No change in heart weight was noted in mice administered 125 

mg/kg diethyl phthalate by daily intraperitoneal injection for 6 weeks (Calley et al. 1966). 
DIETHYL PHTHALATE 42 

2. HEALTH EFFECTS 

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

animals following inhalation exposure to diethyl phthalate or in humans following oral or dermal 

exposure to diethyl phthalate. Although high dietary concentrations have been associated with 

enlarged gastrointestinal organs in rats following oral exposure to diethyl phthalate, these effects are 

apparently not treatment-related (Brown et al. 1978). 

Histopathological evaluation revealed no evidence of irritation in the bowel or pancreas of mice given 

a single intraperitoneal injection of 2,464 mg/kg diethyl phthalate (Lawrence et al. 1975), or any 

histopathological changes in the gastrointestinal tracts of rodents dermally administered up to 300 μL 

daily in a chronic board draft study (NTP 1993). 

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

inhalation, oral, or dermal exposure to diethyl phthalate. 

Limited information available from studies in experimental animals indicates that oral (intermediateduration), dermal (chronic), or parenteral (single-dose) administration of diethyl phthalate had no effect 

on any hematological parameters measured (Brown et al. 1978; Lawrence et al. 1975; NTP 1993 

[board draft]). 

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

animals following inhalation or dermal exposure to diethyl phthalate or in humans following oral 

exposure to diethyl phthalate. High dietary administration of diethyl phthalate to rats did not affect the 

histological appearance of skeletal muscle (Brown et al. 1978). 

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

dermal exposure to diethyl phthalate. 

Studies indicate that, while it appears that diethyl phthalate can induce an increase in relative liver 

weight in experimental animals following oral exposure (Brown et al. 1978; Oishi and Hiraga 1980), 

the absence of any evidence of treatment-related biochemical, functional, or histopathological changes 
DIETHYL PHTHALATE 43 

2. HEALTH EFFECTS 

in the liver suggests that the increase in liver weight may be an adaptive response rather than a direct 

toxic effect of diethyl phthalate. Other studies have demonstrated minor changes in liver weight or 

liver enzyme activity in rats after intermediate-duration oral exposure to diethyl phthalate (Moody and 

Reddy 1978). Results regarding hepatic peroxisomal proliferation after diethyl phthalate treatment are 

equivocal (Moody and Reddy 1978; Okita and Okita 1992). No histopathological evidence of hepatic 

irritation or damage has been found after diethyl phthalate administration in mice and rats (Lawrence 

et al. 1975; NTP 1993 [board draft]). 

Renal Effects. No studies were located regarding renal effects in humans after inhalation, oral, or 

dermal exposure to diethyl phthalate. 

Studies indicate that, while it appears that diethyl phthalate can induce an increase in relative kidney 

weight in experimental animals following oral exposure (Brown et al. 1978), the absence of any 

reliable evidence of treatment-related biochemical, functional, or histopathological changes in the 

kidney suggests that the increase in kidney weight may not be a direct toxic effect of diethyl phthalate. 

Endocrine Effects. No studies were located regarding endocrine effects in humans or animals 

following inhalation or dermal exposure to diethyl phthalate or in humans following oral exposure to 

diethyl phthalate. Dietary administration of high diethyl phthalate concentrations had no effect on the 

histopathology of the adrenals, pancreas, thyroid, parathyroid, and/or pituitary of laboratory rodents 

(Brown et al. 1978). 

Dermal Effects. No studies were located regarding dermal effects in humans or animals following 

inhalation or oral exposure to diethyl phthalate or in humans following dermal exposure to diethyl 

phthalate. 

Diethyl phthalate was shown to be very slightly or slightly irritating when applied repeatedly to the 

intact or abraded skin, respectively, of an unidentified species (Dow Chemical 1952). In rats treated 

dermally with diethyl phthalate for 2 years, a mild, apparently adaptive skin acanthosis was found 
DIETHYL PHTHALATE 44 

2. HEALTH EFFECTS 

(NTP 1993 [board draft]). Dermal irritancy from diethyl phthalate should not be a concern near 

hazardous waste sites. 

Ocular Effects. No studies were located regarding ocular effects in humans or animals following 

inhalation exposure to diethyl phthalate or in humans following oral or dermal exposure to diethyl 

phthalate. Administration of up to 5% dietary diethyl phthalate had no effect on the histology of the 

eye (Brown et al. 1978), and ocular irritation tests conducted in rabbits indicate that diethyl phthalate 

is not a primary ocular irritant (Dear and Jassup 1978; Lawrence et al. 1975). 

Body Weight Effects. No studies were located regarding body weight effects in humans or animals 

following inhalation exposure to diethyl phthalate or in humans following oral or dermal exposure to 

diethyl phthalate. A variety of data from laboratory animal studies indicates body weight gain 

decrement at doses far in excess of those expected at hazardous waste sites (Brown et al. 1978; Lamb 

et al. 1987; NTP 1984, 1993 [board draft]). The available data suggest that the effects are primarily 

attributable to the stress associated with the dosing level rather than to a direct toxic action. 

Although available information is insufficient to determine whether exposure to diethyl phthalate in the 

vicinity of hazardous waste sites could produce systemic toxicity in humans, its widespread use in 

cosmetic formulations without apparent adverse effects and its virtual lack of toxic effects in animal 

studies suggest that it is not likely to be associated with systemic effects at the levels present in the 

vicinity of hazardous waste sites. 

Immunological and Lymphoreticular Effects. A patch test study for allergic contact dermatitis 

was conducted with workers in a factory that produced shoes from polyvinyl chloride granulate (which 

contains dioctyl-phthalate) (Vidovic and Kansky 1985). One of 30 workers with dermatitis and 1 of 

30 without dermatitis responded positively to diethyl phthalate. None of the controls had a positive 

response. The authors concluded that these results indicate that the phthalates are sensitizers, and that 

the positive reaction to diethyl phthalate was most likely due to cross-sensitization with dioctyl 

phthalate since diethyl phthalate is present in very small amounts in polyvinyl chloride. 
DIETHYL PHTHALATE 45 

2. HEALTH EFFECTS 

Although the available information is insufficient to determine whether exposure to diethyl phthalate at 

levels present in the vicinity of hazardous waste sites could induce adverse immunological effects in 

humans, its widespread use in cosmetic formulations without apparent adverse effect suggests that this 

is not likely. 

Neurological Effects. No studies were located regarding neurological effects in humans or animals 

following inhalation exposure to diethyl phthalate or in humans following oral or dermal exposure. 

Oral or dermal administration of high doses had no effect on the histopathological appearance of 

nervous tissue (Brown et al. 1978; NTP 1993). 

Acute-duration parenteral administration studies in mice indicate that diethyl phthalate affected 

pentobarbital-induced sleep (Calley et al. 1966; Lawrence et al. 1975). This effect may be due to a 

direct action of diethyl phthalate on the central nervous system or an effect on the hepatic enzymes 

that metabolize pentobarbital. Neither study had been designed to assess the potential neurotoxicity of 

diethyl phthalate. 

Although the available information is insufficient to determine whether exposure to diethyl phthalate at 

the levels present in the vicinity of hazardous waste sites could induce adverse neurotoxic effects in 

humans, its widespread use in cosmetic formulations without apparent adverse effect suggests that this 

is not likely. 

Reproductive Effects. No in vivo studies were located regarding reproductive effects in humans 

following exposure to diethyl phthalate. In vitro, diethyl phthalate adversely affected measures of 

human sperm motility (Fredricsson et al. 1993). The relationship of the exposure concentrations used 

in this study to expected concentrations resulting from environmental or occupational exposure is 

unknown. 

In a continuous breeding study in CD-l mice, dietary administration of diethyl phthalate produced 

physiological effects in F1 parental animals and significantly decreased their litter size (Lamb et al. 

1987). No adverse effects on the physiology, fertility, or reproductive performance of the F0 
DIETHYL PHTHALATE 46 

2. HEALTH EFFECTS 

generation animals were observed. The parental toxicity in the F1 generation was evident from a 

significant decrease in body weight, increased prostate weight in males, and increased liver and 

pituitary weights in females. However, histological findings in the liver and pituitary were not 

reported, rendering the toxicological significance of a change in these organ weights unknown. 

Although a significant decrease in sperm concentration occurred in the males, no adverse effect on the 

fertility was observed. The total number of live pups per litter was significantly lower in the test 

group compared to the controls. 

Several investigators have studied the effects of diethyl phthalate on male reproductive function in rats 

since other phthalic acid esters have been shown to be toxic to the male reproductive system (ATSDR 

1989; Foster et al. 1980, 1983; Gray and Butterworth 1980; Oishi and Hiraga 1980). Testicular and 

accessory gland weight and histopathology, as well as biochemical parameters of testicular function, 

were unaffected by the oral administration of diethyl phthalate to male rats at doses up to 

1,600 mg/kg/day (Foster et al. 1980, 1983; Gray and Butterworth 1980; Oishi and Hiraga 1980). At 

2,000 mg/kg/day, for 2 days, diethyl phthalate produced mitochondrial swelling and smooth 

endoplasmic reticulum focal dilation and vesiculation in the Leydig cells of rats. These results were 

not replicated when the primary hydrolysis product, monoethyl phthalate, was tested in Leydig cell 

culture (Jones et al. 1993). In cultured rat Sertoli cells, diethyl phthalate had no effect on cyclic 

adenosine monophosphate (AMP) accumulation or basal lactate production (Heindel and Powell 1992). 

Although available information is insufficient to determine whether exposure to diethyl phthalate in the 

vicinity of hazardous waste sites could produce adverse reproductive effects in humans, its widespread 

use in cosmetic formulations without apparent adverse effects and its virtual lack of toxic effects in 

animal studies suggest that it is not likely to be associated with reproductive toxicity at levels present 

in the vicinity of hazardous waste sites. 

Developmental Effects. No studies were located regarding developmental effects in humans after 

exposure to diethyl phthalate. 
DIETHYL PHTHALATE 47 

2. HEALTH EFFECTS 

Maternal rats receiving 3,210 mg/kg/day of diethyl phthalate throughout organogenesis produced 

offspring with an increased incidence of skeletal variations, particularly supernumerary ribs. This 

finding was accompanied by decreased weight gain and decreased food and water consumption in the 

dams. Exposure to this level or lower dietary concentrations resulted in no additional developmental 

effects (Field et al. 1993). The significance of the increased incidence of skeletal variations is highly 

questionable because it occurred only at a dietary concentration associated with maternal effects. 

After oral administration of diethyl phthalate to mice (4,500 mg/kg/day on gestation days 6-13), there 

was no significant evidence of maternal toxicity or neonatal developmental effects in a short-term in 

vivo developmental toxicity screen (Hardin et al. 1987). Developmental toxicity did occur in 

developing rat embryos when the mother was injected intraperitoneally with diethyl phthalate at doses 

of 2,884, 5,667, or 9,442 mg/kg/day on days 5, 10, and 15 of gestation (Singh et al. 1971, 1972, 

1973). Adverse fetal effects included an increase in the number of skeletal abnormalities and 

resorption sites. No gross (external) malformations or fetal deaths were seen. Fetal weights were 

significantly reduced (p<0.01). The relevance of these findings with regard to potential developmental 

toxicity in humans exposed to diethyl phthalate in the vicinity of hazardous waste sites is not known; 

however, the route of exposure used in this animal study is unlikely to occur in humans. 

Genotoxic Effects. No in vivo studies were located regarding genotoxic effects in humans or 

animals following exposure to diethyl phthalate. Data from in vitro studies using prokaryotic and 

cultured mammalian cells are presented in Table 2-3. 

A comparison of the results of in vitro mutagenic assays of diethyl phthalate in various strains of 

Salmonella typhimurium shows contradictory findings. Diethyl phthalate has been shown to be 

mutagenic for L typhimurium strains TA98, TAl00, and TA1535 mostly without metabolic activation 

(Agarwal et al. 1985; De Marini et al. 1987; Kozumbo et al. 1982). Contrary to these findings, diethyl 

phthalate has been found to be nonmutagenic in S. typhimurium strains TA98, Tal00, TA1535, 

TA1537, and TA2637 with or without metabolic activation (Agarwal et al. 1985; DeMarini et al. 1987; 

NTP 1993 [board draft]; Zeiger et al. 1982, 1985). 

DIETHYL PHTHALATE 49 

2. HEALTH EFFECTS 

A well-conducted study investigated the mutagenicity of diethyl phthalate in concentrations ranging 

from 10 to 10,000 μg/plate in a preincubation modification of the Ames test with and without 

exogenous metabolic activation using Aroclor 1254-induced rat liver S9 (Zeiger et al. 1982, 1985). 

The findings indicated that diethyl phthalate was not mutagenic in S. typhimurium strains TA1535, 

TA1537, TA98, or TAl00 with or without metabolic activation. Another Ames test study indicated 

that diethyl phthalate at 1,000 μg/plate was mutagenic in S. typhimurium strain TAl00 but only in the 

absence of activation (Kozumbo et al. 1982). However, the results are not convincing because the 

background reversion frequency was too high (291±20) and because the highest response observed for 

the number of revertants/plate (1.90 ±0.09) was a less than twofold increase. An Ames spot test 

study indicated that a 50-μg dose of diethyl phthalate did not produce mutagenic results with or 

without metabolic activation (Blevins and Taylor 1982). The spot test has the limitation of being a 

qualitative test; a plate incorporation assay should have been conducted before an evaluation of 

mutagenicity was made. An Ames test study using concentrations of diethyl phthalate ranging from 

10 to 2,000 μg/plate showed mutagenicity at 1,500 μg/plate (Agarwal et al. 1985). A threefold 

increase in the number of revertant colonies was seen in TAl00 without activation, and an 

approximate twofold increase was seen in TA1535 without activation. An Ames test study examining 

concentration-response effects in crude wastes and waste extracts containing diethyl phthalate showed 

a twofold or greater increase in mutagenicity with and without activation in TA98 at a dose (100 μg) 

much lower than those of other studies suggesting that other impurities may have been present (De 

Marini et al. 1987). The results of an 8-azaguanine resistance assay in S. typhimurium indicated that 

diethyl phthalate was positive for mutagenicity (Seed 1982). However, the results failed to be 

significant with less than a twofold increase in the number of mutants per one million cells at the 

highest concentration of 3.3 mmol/L. 

Two chromosomal aberration assays with Chinese hamster fibroblasts and ovaries, respectively, 

produced negative mutagenic results for diethyl phthalate at concentrations up to 0.324 mg/mL 

(Ishidate and Odashima 1977; NTP 1993 [board draft]). However, at culture concentrations of 0.05, 

0.167, and 0.5 μg/L, diethyl phthalate produced a concentration-related increase in the number of 

relative sister chromatid exchanges per chromosome. This effect occurred only in the presence of the 

S9 fraction from rat liver homogenates (NTP 1993 board draft]). 
DIETHYL PHTHALATE 50 

2. HEALTH EFFECTS 

In summary, the results of in vitro mutagenicity tests in microbial assays are equivocal. No in vivo 

studies were located. Further studies are required before the genotoxic potential of diethyl phthalate in 

humans living in the vicinity of diethyl phthalate-contaminated hazardous waste sites can be 

determined. 

Cancer. No studies were located regarding cancer in humans following exposure to diethyl phthalate. 

In a recently completed board draft study, dermally applied diethyl phthalate showed no carcinogenic 

potential in a 2-year rat study and in both initiation and promotion studies in mice. The only evidence 

for possible carcinogenicity in a 2-year mouse study was an increased incidence of combined hepatic 

adenomas/carcinomas in both sexes. Growth data suggested that the highest applied dose, 30 μL/day, 

or 772 mg/kg/day, 5 days/week, was slightly below a maximum tolerated dose (NTP 1993 [board 

study]). The tumor incidence was dose-related in males only. In general, the results of this study 

suggest that individuals residing near an NPL site are not at a significant risk of developing cancer 

from diethyl phthalate exposure. 

EPA (IRIS 1994) has classified diethyl phthalate as a Group D chemical--not classifiable as to its 

carcinogenicity--because pertinent data regarding carcinogenicity were not located in the available 

literature. Therefore, the carcinogenic potential of diethyl phthalate for humans exposed in the vicinity 

of hazardous waste sites cannot be determined at this time. 

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 
DIETHYL PHTHALATE 51 

2. HEALTH EFFECTS 

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 diethyl phthalate are discussed in Section 2.5.1. 

Biomarkers of effect are defined as any measurable biochemical, physiologic, or other alteration within 

an organism that, depending on magnitude, can be recognized as an established or potential health 

impairment or disease (NAS/NRC 1989). This definition encompasses biochemical or cellular signals 

of tissue dysfunction (e.g., increased liver enzyme activity or pathologic changes in female genital 

epithelial cells), as well as physiologic signs of dysfunction such as increased blood pressure or 

decreased lung capacity. Note that these markers are 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 diethyl phthalate 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 Diethyl Phthalate 

Diethyl phthalate can be detected and quantified in human semen and in animal fat and tissues (Giam 

and Chan 1976; van Lierop and van Veen 1988; Waliszewski and Szymczymski 1990). Limited data 
DIETHYL PHTHALATE 52 

2. HEALTH EFFECTS 

are available regarding the metabolism of diethyl phthalate. An in vitro study revealed that the first 

step of diethyl phthalate metabolism involves hydrolysis to its monoester derivative, monoethyl 

phthalate (Lake et al. 1977). However, no data are available regarding the identification of this 

metabolite in the urine, blood, or tissues. In one study, radiolabeled diethyl phthalate was dermally 

applied to rats (Elsisi et al. 1989). The radiolabel was recovered in the urine; however, no attempt 

was made to characterize the metabolites found in the urine. Since the monoester derivative of diethyl 

phthalate is a probable urinary metabolite (although not identified), it could be a useful biomarker of 

exposure. There are no other known biomarkers of exposure to diethyl phthalate. 

2.5.2 Biomarkers Used to Characterize Effects Caused by Diethyl Phthalate 

No biomarkers of effects caused by diethyl phthalate have been identified in humans or animals. 

2.6 INTERACTIONS WITH OTHER CHEMICALS 

No studies have been identified that investigated the effects of exposure to diethyl phthalate together 

with other chemicals. 

2.7 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE 

A susceptible population will exhibit a different or enhanced response to diethyl phthalate than will 

most persons exposed to the same level of diethyl phthalate 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.” 
DIETHYL PHTHALATE 53 

2. HEALTH EFFECTS 

Offspring of mice exposed to diethyl phthalate exhibited adverse effects as adults (decreased body 

weight, increased prostate weight, and decreased sperm count in males; increased liver and pituitary 

weights in females) (Lamb et al. 1987). These findings suggest that prenatal exposure to diethyl 

phthalate may be associated with adverse effects in mature offspring. No other information is 

available on populations with above-average sensitivity to diethyl phthalate. 

2.8 METHODS FOR REDUCING TOXIC EFFECTS 

This section will describe clinical practice and research concerning methods for reducing toxic effects 

of exposure to diethyl phthalate. 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 

diethyl phthalate. When specific exposures have occurred, poison control centers and medical 

toxicologists should be consulted for medical advice. 

Following dermal exposure to diethyl phthalate, it has been recommended that the skin be immediately 

washed with copious amounts of soapy water (Stutz and Janusz 1988). If the eyes are exposed to the 

liquid or vapor, it has been suggested that they be thoroughly flushed with water. Following ingestion 

of diethyl phthalate, administration of milk, a dilutant and demulcent, has been recommended. Water 

can be used as an alternative to milk (Haddad and Winchester 1990; Stutz and Janusz 1988). 

Administration of activated charcoal as an absorptive surface for the contaminant has also been 

recommended. If ingestion of large amounts of diethyl phthalate has occurred, the administration of a 

cathartic, such as magnesium sulfate, has been shown to increase the elimination of the substance from 

the gastrointestinal tract. 

2.8.1 Reducing Peak Absorption Following Exposure 

Diethyl phthalate is noncorrosive to tissues. Consequently, removal from the gastrointestinal tract 

either by syrup of Ipecac or by activated charcoal may be possible. These two techniques are effective 

for approximately 4 to 6-1

/2 hours after administration, respectively (Ellenhorn and Barceloux 1988). 

However, because diethyl phthalate has shown little if any toxicological potential, issues regarding 

reduction in peak absorption may be superfluous. 
DIETHYL PHTHALATE 54 

2. HEALTH EFFECTS 

2.8.2 Reducing Body Burden 

Few toxicokinetic data are available on diethyl phthalate. However, even at extremely high exposure 

concentrations, diethyl phthalate does not have the same toxicological properties as its probable 

hydrolysis product, ethanol. Because of its apparent negligible toxicity, it is unlikely that body 

burdens would ever reach levels of concern. 

2.8.3 Interfering with the Mechanism of Action for Toxic Effects 

Few mechanistic data are available on diethyl phthalate. However, as diethyl phthalate shows little 

toxicity in human and animal studies, an understanding of events that interfere with the mechanism of 

action may not be necessary. 

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 dietbyl phthalate 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 diethyl phthalate. 

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. 
DIETHYL PHTHALATE 55 

2. HEALTH EFFECTS 

2.9.1 Existing Information on Health Effects of Diethyl Phthalate 

The existing data on health effects of inhalation, oral, and dermal exposure of humans and animals to 

diethyl phthalate are summarized in Figure 2-2. The purpose of this figure is to illustrate the existing 

information concerning the health effects of diethyl phthalate. 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. 

As can be seen in Figure 2-2, practically no information is available on the health effects of diethyl 

phthalate in humans, and very little information is available in animals. Most of the available 

information on the toxicity of diethyl phthalate in animals comes from studies in which this compound 

was administered by oral, parenteral (i.e., intraperitoneal, intravenous) or dermal routes. In humans, 

the only information available is patch test data demonstrating that diethyl phthalate is associated with 

allergic contact dermatitis in a limited number of polyvinyl chloride workers. Acute oral lethality 

studies are available in animals. An, acute duration in vivo developmental assay and a two-generation 

reproductive toxicity study were conducted with diethyl phthalate by the oral route. The data avai!able 

on the effects of dermally administered diethyl phthalate in animals include a board draft report on 

intermediate duration and chronic exposure studies in rats and mice and additional studies on dermal 

and ocular irritation. 

2.9.2 Identification of Data Needs 

Acute-Duration Exposure. There is no information available to identify target organs in humans 

or animals following acute-duration inhalation or dermal exposure to diethyl phthalate. Although 

diethyl phthalate has a low vapor pressure (1.65x10-3 to 3.45x10-4 mmHg; Grayson and Fosbraey 

1982; Howard et al. 1985) and is relatively nontoxic, airborne vaporization is the major fate process 

DIETHYL PHTHALATE 57 

2. HEALTH EFFECTS 

from disposal sites. Consequently, a data need for inhalation studies exists. Minimal lethal oral doses 

for rabbits and guinea pigs of 4,000-5,000 mg/kg have been reported (Smyth and Smyth 1931), but 

LD50 data are available only for parenteral routes of administration (Galley et al. 1966; Singh et al. 

1971, 1972, 1973). A rat study indicated that high dietary levels of diethyl phthalate were associated 

with ultrastructural testicular changes (Jones et al. 1993). These data were used to calculate an acuteduration oral MRL of 7 mg/kg/day. There are insufficient pharmacokinetic data available to support 

the extrapolation of results obtained after oral administration to other routes of exposure. However, 

given findings of minimal toxicity at high oral or dermal doses administered for periods greater than 

14 days, additional acute-duration exposure studies seem unnecessary. 

Intermediate-Duration Exposure. The only effects seen after a 16-week dietary administration 

study with diethyl phthalate in rats were a decrease in body weight gain with a concomitant decrease 

in food consumption (Brown et al. 1978). In 4-week dermal studies with rats and mice, diethyl 

phthalate produced no observable histopathological changes on any tissue (NTP 1993 [board draft]). 

Experimental studies (Moody and Reddy 1978; Okita and Okita 1992) indicate that high diethyl 

phthalate doses have only slight effects on peroxisomal proliferation and have a minor effect on 

microsomal enzyme induction. The Moody and Reddy (1978) data were used to support an 

intermediate-duration MRL of 6 mg/kg/day. An inhalation toxicity study would help determine routespecific effects via the potentially most significant exposure route. 

Chronic-Duration Exposure and Cancer. No chronic or carcinogenicity studies have been 

conducted in humans or animals exposed orally or by inhalation. The results of a chronic-duration 

dermal application study and initiation-promotion experiments indicate that diethyl phthalate has little 

if any nonneoplastic or neoplastic potential at doses near a Maximum Tolerated Dose (NTP 1993 

[board draft]). Although chronic oral data are lacking, the results from the complete database suggest 

that lifetime exposure near NPL hazardous waste sites would not result in a significant health hazard. 

A long-term inhalation study to address this issue, in a representative animal species, would help to 

validate this conclusion. 
DIETHYL PHTHALATE 58 

2. HEALTH EFFECTS 

Genotoxicity. No in vivo studies were located regarding genotoxic effects in humans or animals 

following inhalation, oral, or dermal exposure to diethyl phthalate. The results of in vitro mutagenicity 

tests in microbial systems are equivocal (Agarwal et al. 1985; DeMarini et al. 1987; Kozumbo et al. 

1982; NTP 1993 [board draft]; Zeiger et al. 1982, 1985). These studies indicate negative findings for 

chromosomal aberrations in mammalian cultures, increased sister chromatid exchange frequencies in 

mammalian cultures, and generally negative incidences of reverse mutation in prokaryotic assays. 

Given the inconsistent nature of the in vitro results, in vivo tests of chromosome aberrations in animals 

exposed to diethyl phthalate would be useful to elucidate the genotoxic potential of this compound. 

Reproductive Toxicity. There is no information on the reproductive effects of diethyl phthalate in 

humans following inhalation, oral, or dermal exposure. This result is consistent with reproductive data 

from other straight chain-substituted phthalate esters. Diethyl phthalate may produce minor adverse 

effects on male reproductive organ function or morphology in experimental animals (Jones et al. 

1993). In a two-generation continuous breeding dietary reproductive toxicity study in mice, no 

adverse effect on any measured parameter of fertility was observed in either generation; however, the 

total number of live pups per litter was significantly lower in litters born to F, parents (Lamb et al. 

1987). Oral administration of diethyl phthalate at 2 g/kg body weight in rats resulted in ultrastructural 

Leydig cell changes, including mitochondrial swelling with focal dilatation of the smooth endoplasmic 

reticulum (Jones et al. 1993). In the same study, however, in vitro Leydig cell testosterone secretion 

was unaffected by 1 millimolar (mM) monoethyl phthalate treatment. At 0.33 mM and above, diethyl 

phthalate adversely affected sperm motility (Fredricsson et al. 1993). Monoethyl phthalate at 0.1 mM 

had no effect on in vitro Sertoli cell function (Heindel and Powell 1992). These data confirm and 

extend the results of previous studies indicating that testicular functional and anatomical changes 

inconsistently occur at high diethyl phthalate exposure levels. Although few results on female 

reproductive effects are available, an analysis of the data from both reproductive and developmental 

studies suggest that no adverse reproductive effects would occur at exposure levels expected near NPL 

sites. Consequently, no data needs currently exist. 
DIETHYL PHTHALATE 59 

2. HEALTH EFFECTS 

Developmental Toxicity. No information is available on the developmental effects of diethyl 

phthalate in humans following inhalation, oral, or dermal exposure. No developmental effects were 

noted in an acute-duration oral in vivo developmental toxicity screen in mice (Hardin et al. 1987). An 

increased incidence of skeletal variations in rat pups, at an oral diethyl phthalate dose of 

3,210 mg/kg/day, may have been associated with either a direct toxic effect or with transient maternal 

malnutrition (Field et al. 1993). However, skeletal abnormalities and an increased number of 

resorptions were noted following intraperitoneal administration of 3,000-9,000 mg/kg/day diethyl 

phthalate to pregnant rats (Singh et al. 1971, 1972, 1973). Because of the administration route and the 

high dose administered, the relevance of this study to human exposure is not known. In general, the 

data from oral studies, using extremely high exposure conditions, indicate that diethyl phthalate would 

not be a developmental hazard at occupational or environmental concentrations. Consequently, no data 

needs currently exist. 

Immunotoxicity. Diethyl phthalate may be a contact sensitizer in a limited number of human 

receptors (Greif 1967; Oliwiecki et al. 1991; Vidovic and Kansky 1985). However, the possibility of 

cross-sensitization with other compounds, including other phthalate esters, renders the significance of 

these findings questionable. No reliable animal data were available. A more comprehensive doseresponse study using well established sensitized and nonsensitized animal models may help clarify the 

potential of diethyl phthalate as an immunotoxic agent. 

Neurotoxicity. No information is available on the neurological effects of diethyl phthalate in 

humans or animals following inhalation, oral, or dermal exposure. Acute-duration parenteral 

administration studies in mice indicate that diethyl phthalate affected pentobarbital-induced sleep 

(Calley et al. 1966; Lawrence et al. 1975). However, this effect may be due to a direct action of 

diethyl phthalate on. the central nervous system or an effect on the hepatic enzymes that-metabolize 

pentobarbital. There currently exists a need for observing overt or histopathological evidence of 

neurological aberrations in a controlled animal study. 
DIETHYL PHTHALATE 60 

2. HEALTH EFFECTS 

Epidemiological and Human Dosimetry Studies. No epidemiological studies are available on 

populations that have been exposed solely to diethyl phthalate. As a result of its use, together with 

other phthalate esters, as a plasticizer for cellulose ester films and in extruded materials and a variety 

of consumer products (including cosmetics and skin care preparations) (Anonymous 1985; Kamrin and 

Mayor 1991), exposure of the general population and of workers in occupational settings is significant. 

Therefore, it is unlikely that both a specific subpopulation exposed only to diethyl phthalate and a 

control population with no known exposure could be identified. Given this inability to find suitably 

exposed subpopulations, as well as diethyl phthalate’s low systemic toxicity and apparent lack of target 

organ effects at occupational or environmental concentrations, epidemiological and human dosimetry 

studies are both unfeasible and unnecessary. A better understanding of the role of the liver as a 

potential target organ should take precedence. 

Biomarkers of Exposure and Effect. Ethanol and phthalic acid, the putative diethyl phthalate 

hydrolysis products, are nonspecific biomarkers. The pharmacokinetics of the only potential specific 

biomarker of exposure, monoethyl phthalate, are unknown. Furthermore, no adverse effects specific to 

diethyl phthalate have been identified. Because of the unlikelihood that the vast proportion of 

individuals occupationally or environmentally exposed to diethyl phthalate will show any adverse 

effects, research to find biomarkers of exposure seems unnecessary. 

Since exposure to diethyl phthalate does not produce a unique clinical disease state, no biomarkers of 

effect have been identified. 

Absorption, Distribution, Metabolism, and Excretion. No studies were located regarding the 

absorption of diethyl phthalate following inhalation or oral exposure in humans or animals. No in vivo 

studies were located regarding absorption of diethyl phthalate following dermal exposure-in humans. 

However, an in vivo animal study (Elsisi et al. 1989) and several in vitro studies (Hotchkiss et al. 

1992; Mint et al. 1992; Scott et al. 1987) indicate that diethyl phthalate is absorbed through the skin of 

humans and rats. Using the amount of radiolabel present as an index of percutaneous absorption, 24% 

of a single dose of 34.89 mg/kg applied dermally to rats was excreted in the first 24 hours (Elsisi et al. 

1989). A cumulative total of 50% was excreted after 7 days. An in vitro study of the absorption of 
DIETHYL PHTHALATE 61 

2. HEALTH EFFECTS 

diethyl phthalate through human and rat epidermal membranes indicates that diethyl phthalate is 

slowly absorbed through both human and rat skin; however, diethyl phthalate was absorbed more 

quickly through rat skin than through human skin. The results showed that rat skin was more 

permeable to diethyl phthalate than human skin. Following contact with diethyl phthalate, there was 

an increase in the permeability for both human and rat skin. However, rat skin showed a much greater 

change in permeability indicating that irreversible alteration of the membrane permeability occurred as 

a result of exposure to diethyl phthalate (Scott et al. 1987). Additional oral and inhalation in vivo 

absorption data would be useful in order to assess the relative rates and extent of absorption and may 

help in the identification of potential mechanisms of action. 

No studies were located regarding the distribution of diethyl phthalate following inhalation or oral 

exposure in humans or animals. No studies were located regarding distribution in humans following 

dermal exposure. Only one study was located regarding distribution in animals following dermal 

exposure (Elsisi et al. 1989). The results of this acute study in rats showed that although tissue 

distribution was wide, diethyl phthalate and/or its metabolites are not likely to accumulate in the 

tissues to any great extent. Less than 5% of the administered dose was found in the tissues (brain, 

lung, liver, spleen, small intestine, kidney, testis, spinal cord, blood, adipose tissue, muscle, and skin). 

An acute intraperitoneal study in rats showed that diethyl phthalate crossed the placenta from mother 

to fetus and was distributed in maternal blood, placenta, amniotic fluid, and fetal tissue; however, very 

little (<1%) of the dose was present (Singh et al. 1975). Limited additional experimental data for both 

humans and animals would be useful in order to adequately assess similarities and differences in the 

distribution of diethyl phthalate and/or its metabolites after oral or inhalation exposure. 

Very limited information is available regarding the metabolism of diethyl phthalate (Gollamudi et al. 

1985; Lake et al. 1977). In vitro studies indicate that the first step in the metabolism of diethyl 

phthalate involves hydrolysis to a monoester derivative (Lake et al. 1977). Although data on the 

metabolism of phthalate diesters as a class were located, more specific data on diethyl phthalate would 

help to adequately characterize the metabolism of this compound. The significance of high dose 

effects observed in toxicity studies may be clarified by metabolism findings. For example, properly 

designed studies would indicate whether metabolic saturation occurs at high doses, which may help 
DIETHYL PHTHALATE 62 

2. HEALTH EFFECTS 

explain the excess metabolic demands that such doses entail. This information may be essential for 

determining whether an MRL can be derived. 

No studies were located for humans or animals regarding the excretion of diethyl phthalate following 

inhalation or oral exposure. Very limited data indicate that diethyl phthalate is excreted primarily in 

the urine following acute dermal exposure in rats (Elsisi et al. 1989). An excretion half-life of 

2.2 days was calculated for diethyl phthalate in rats (Singh et al. 1975). Dose-response information on 

the identity of the metabolites excreted would help clarify the significance of high-dose effects, 

including hepatic peroxisomal proliferation (Moody and Reddy 1978), ultrastructural testicular changes 

(Jones et al. 1993), and body weight gain inhibition (Lamb et al. 1987). 

Comparative Toxicokinetics. Limited in vitro data indicate that both humans and rats absorb 

diethyl phthalate relatively slowly through the skin but that rats seem to absorb the compound more 

quickly than humans (Elsisi et al. 1989; Scott et al. 1987). Few data are available to adequately 

indicate the similarities and/or differences in target organs. Toxicokinetic studies (in vitro) have been 

performed in both humans and animals (multiple species); however, the data are extremely limited. 

Humans and animals (rodent, nonrodent, and nonhuman primate) were qualitatively similar in their 

ability to hydrolyze diethyl phthalate in the intestines and liver. However, quantitative species 

differences were observed in the rates of hydrolase activity of the rodent, nonrodent, and nonhuman 

primate with the order being primate > rodent > nonrodent (Lake et al. 1977). Excretion data 

identifying the metabolites of diethyl phthalate found in the urine and feces of humans and in multiple 

animal species would be useful in order to adequately assess which animals can serve as the best 

models. 

Methods for Reducing Toxic Effects. All of the treatment methods currently available for use in 

diethyl phthalate ingestion or skin contact are supportive in nature and/or involve decreasing 

absorption or hastening elimination of diethyl phthalate (Haddad and Winchester 1990; Stutz and 

Janusz 1988). Since the mechanism of diethyl phthalate toxicity is not known, there are currently no 

methods geared towards mitigating the effects of diethyl phthalate by interfering with its mode of 

action. Therefore, more information on the mechanism of action for diethyl phthalate would be useful 
DIETHYL PHTHALATE 63 

2. HEALTH EFFECTS 

in order to devise methods for the mitigation of any potential toxic effect, such as peroxisomal 

proliferation. 

2.9.3 On-going Studies
 

No on-going studies on the health effects or toxicokinetics of diethyl phthalate were found.
 

DIETHYL PHTHALATE 65 

3. CHEMICAL AND PHYSICAL INFORMATION
 

3.1 CHEMICAL IDENTITY
 

Information regarding the chemical identity of diethyl phthalate is located in Table 3-1.
 

3.2 PHYSICAL AND CHEMICAL PROPERTIES
 

Information regarding the physical and chemical properties of diethyl phthalate is located in Table 3-2.
 



DIETHYL PHTHALATE 69 

4. PRODUCTION, IMPORT, USE, AND DISPOSAL
 

4.1 PRODUCTION 

Diethyl phthalate is produced industrially by the reaction of phthalic anhydride with ethanol in the 

presence of concentrated sulfuric acid catalyst (Anonymous 1985; HSDB 1994). Phthalic anhydride is 

produced by either the oxo process or the Ald-Ox process from ethanol and the oxidation of 

naphthalene or o-xylene (Peakall 1975). The purity of manufactured phthalate esters is reportedly 

between 99.70% and 99.97% with the main impurities being isophthalic acid, terephthalic acid, and 

maleic anhydride (Peakall 1975). The U.S. production volume of diethyl phthalate gradually declined 

from approximately 21 million pounds in 1980 to 19 million pounds in 1987 (USITC 1981, 1988). 

Production volumes increased again in 1988 to 26 million pounds (Kamrin and Mayor 1991). 

Currently the four U.S. facilities that reportedly produce diethyl phthalate are Eastman Chemical 

Company (Kingsport, Tennessee), Reilly Industries, Inc. (Greensboro, North Carolina), BASF 

Corporation (Parsippany, New Jersey), and Huls America, Inc. (Piscataway, New Jersey) (HSDB 1994; 

SRI 1991). Since diethyl phthalate releases are not required to be reported under the Super-fund 

Amendments and Reauthorization Act (SARA) Section 313, there are no data on diethyl phthalate in 

the Toxics Release Inventory (TR188 1991, 1993). 

4.2 IMPORT/EXPORT 

U.S. imports of diethyl phthalate decreased from 610,684 pounds in 1978 to 511,475 pounds in 1982 

(HSDB 1994). More recent data on imports are not available. There are no data available on U.S. 

exports of diethyl phthalate. 
DIETHYL PHTHALATE 70 

4. PRODUCTION. IMPORT, USE, AND DISPOSAL 

4.3 USE 

There is a wide variety of consumer products that contain diethyl phthalate or are covered with diethyl 

phthalate-containing plastic packaging (Kamrin and Mayor 1991). Diethyl phthalate is used as a 

plasticizer for cellulose ester plastic films and sheets (photographic, blister packaging, and tape 

applications) and molded and extruded articles (consumer articles such as toothbrushes, automotive 

components, tool handles, and toys). Diethyl phthalate was reported as an ingredient in 67 cosmetic 

formulations at concentrations ranging from ≤0.1 % to 25-50%. These cosmetics included bath 

preparations (oils, tablets, and salts), eye shadows, toilet waters, perfumes and other fragrance 

preparations, hair sprays, wave sets, nail polish and enamel removers, nail extenders, nail polish, bath 

soaps, detergents, aftershave lotions, and skin care preparations (Anonymous 1985; Kamrin and Mayor 

1991). More specifically, diethyl phthalate is used in nail polish as a solvent for nitrocellulose and 

cellulose acetate, in perfumes as a fixative and solvent, in toilet preparations as an alcohol denaturant, 

and in fingernail elongators as a plasticizer (Anonymous 1985; EPA 1989; Hawley 1987; Verschueren 

1983). In addition, diethyl phthalate is used as a component in insecticide sprays and mosquito 

repellents, as a camphor substitute, as a plasticizer in solid rocket propellants, as a wetting agent, as a 

dye application agent, as an ingredient in aspirin coatings, as a diluent in polysulfide dental impression 

materials, and in adhesives, plasticizers, and surface lubricants used in food and pharmaceutical 

packaging (Anonymous 1985; EPA 1989; Guy and Powers 1977; Hawley 1987; Verschueren 1983). 

4.4 DISPOSAL 

Recommended methods for disposal of diethyl phthalate include incineration and landfill. The best 

techniques for incineration are liquid injection and rotary kiln. The incineration range for the former 

is 650°C to 1,600oC, with a residence time of 0.1 to 2 seconds. The temperature range for rotary kiln 

incineration is 820°C to 1,600oC. Fluidized bed incineration, with a temperature range of 450°C to 

980°C is also a good technique (HSDB 1994). Combustion of diethyl phthalate may be improved by 

mixing with a more flammable solvent (OHM/TADS 1991). Landfill may be implemented after 

adsorption on vermiculite or a similar adsorbent. Before implementing land disposal of waste residue, 

environmental regulatory agencies should be consulted for guidance on acceptable disposable practices 

(HSDB 1994). 
DIETHYL PHTHALATE 71 

5. POTENTIAL FOR HUMAN EXPOSURE 

5.1 OVERVIEW 

As a result of its use as a plasticizer for cellulose ester films and extruded materials and in a variety of 

consumer products, human exposure to diethyl phthalate is expected to be significant. Diethyl 

phthalate may be released to the environment as a result of manufacturing processes, disposal in 

landfills, incomplete incineration, or by leaching or volatilization from products in which it is used. 

Releases are expected to be primarily to water or to soil as a result of leaching from landfills. Diethyl 

phthalate may enter the atmosphere through combustion of plastics and, to a lesser degree, by 

volatilization. Diethyl phthalate partitions to particulate matter in water or sediments, where it can be 

biodegraded either aerobically or anaerobically; other degradation processes are not significant. From 

soils with low organic matter content, diethyl phthalate may enter the underlying groundwater. 

Diethyl phthalate may bioaccumulate to some degree in aquatic organisms, but it is unlikely to 

biomagnify up the food chain. Diethyl phthalate has been identified in 248 of the 1,397 NPL 

hazardous waste sites (HAZDAT 1994). The frequency of these sites within the Unites States can be 

seen in Figure 5-l. Of these sites, 241 are located in the United States, and 1 is located in Guam (not 

shown). 

Diethyl phthalate is likely to undergo biodegradation in the environment. Abiotic degradation 

processes such as hydrolysis, oxidation, and photolysis are unlikely to play significant roles in the 

environmental fate of diethyl phthalate. 

Diethyl phthalate-has-been detected in ambient indoor air, waste waters from industrial facilities, 

surface waters and sediments, and marine waters. Fish and other aquatic biota living in contaminated 

waters have been shown to contain diethyl phthalate in their tissues, although depuration is relatively 

rapid when the organisms are placed in uncontaminated water. 

DIETHYL PHTHALATE 73 

5. POTENTIAL FOR HUMAN EXPOSURE 

Human exposure to diethyl phthalate can result from breathing contaminated air, eating foods into 

which diethyl phthalate has leached from packaging materials, eating contaminated seafood, drinking 

contaminated water, or as a result of medical treatment involving the use of polyvinyl chloride tubing 

(e.g., dialysis patients). The use of diethyl phthalate in consumer products, however, is likely to be 

the primary source of human exposure. Diethyl phthalate has been detected in adipose tissue samples 

taken from people (including children) nationwide. Occupational exposure may occur in industrial 

facilities where diethyl phthalate is used in the manufacture of plastics or consumer products. 

Diethyl phthalate is not included on the Toxics Release Inventory as a reportable chemical. 

Releases to the environment occur primarily as a result of production and manufacturing of diethyl 

phthalate itself and also during use and disposal of products containing diethyl phthalate. Minor 

releases occur as a result of biosynthesis (Pierce et al. 1980). It has been estimated that 7,600 metric 

tons of diethyl phthalate are released annually to the environment (EPA 1981b). 

5.2 RELEASES TO THE ENVIRONMENT 

5.2.1 Air 

Approximately 75% of the total environmental release of phthalate plasticizers from dump sites result 

from low-temperature burning, with subsequent vaporization. Diethyl phthalate may also be released 

directly to the atmosphere as a result of volatilization/evaporation from consumer items such as 

cosmetics and toiletries, insect repellents, and insecticides (Peakall 1975). 

Based on 1977 production data, EPA (1981a) estimated that 200 metric tons of diethyl phthalate would 

be released annually to the air as a result of manufacturing, use, or disposal, and another 200 metric 

tons would be released annually as a result of incineration of diethyl phthalate materials. 
DIETHYL PHTHALATE 74 

5. POTENTIAL FOR HUMAN EXPOSURE 

5.2.2 Water 

Diethyl phthalate was detected in 4.96% of the groundwater samples and 1.42% of the surface water 

samples taken at NPL sites included in the Contract Laboratories Program Statistical Database 

(CLPSD) at mean concentrations of 12.50 and 12.10 μg/L, respectively, in the positive samples 

(CLPSD 1989). Note that the information used from the CLPSD includes data from NPL sites only. 

It has been estimated that the phthalate esters released to the environment may be approximately 1% 

of the phthalate content of plastic materials in direct contact with water or other liquids (Peakall 1975). 

EPA (1981b) estimated that 300 metric tons of diethyl phthalate would be released annually to surface 

water as a result of manufacturing, use, or disposal, based on 1977 production data. 

5.2.3 Soil 

Based on 1977 production data, EPA (1981b) estimated that 6,800 metric tons of diethyl phthalate 

would be released annually to the environment as a result of landfilling activities. 

Diethyl phthalate has been detected in 4.26% of the soil samples taken from the NPL sites included in 

the CLPSD at a mean concentration of 39.06 μg/kg in the positive samples (CLPSD 1989). Note that 

the information used from the CLPSD includes data from NPL sites only. 

5.3 ENVIRONMENTAL FATE 

5.3.1 Transport and Partitioning 

Based on a log octanol water partition coefficient (Kow) ranging from 1.40 (measured, 2.67 estimated; 

Veith et al. 1980) to 3.3 (Laane et al. 1987), diethyl phthalate is considered to be lipophilic and 

consequently may be taken up by lipids in aquatic organisms. However, diethyl phthalate may also be 

degraded by these organisms suggesting that it is unlikely to biomagnify up the food chain (EPA 
DIETHYL PHTHALATE 75 

5. POTENTIAL FOR HUMAN EXPOSURE 

1979). The bioconcentration factor (BCF) for diethyl phthalate using the bluegill sunfish (Lepomis 

macrochirus) in a 21-day study was 117 (log BCF = 2.07; mean water concentration of diethyl 

phthalate = 9.42 μg/L), and the half-life in fish tissue was between 1 and 2 days (Barrows et al. 1980; 

Veith et al. 1980). A study of the uptake of diethyl phthalate through the gills of English sole 

(Purophrys vetulus) indicated that the uptake efficiency was inversely correlated with weight-specific 

ventilation volume and was not correlated with fish weight or with diethyl phthalate exposure 

concentration; the mean uptake was only 11.3% (Boese 1984). 

Air 

No studies were located on the transport and partitioning of diethyl phthalate in the atmosphere. 

Volatilization of diethyl phthalate is expected to be slow based on its low vapor pressure of 1.65x10-3 

mmHg at 25°C (Howard et al. 1985). Diethyl phthalate may be removed from the atmosphere by wet 

or dry deposition (EPA 1989). 

Water 

A computer simulation of the transport of diethyl phthalate in four aquatic systems using the Exposure 

Analysis Modeling System (EXAMS) estimated that, based on a sediment/water partition coefficient 

(Koc) of 4.5x102, >90% of the diethyl phthalate would be distributed to the water column in a river, 

eutrophic lake, or oligotrophic lake ecosystem, with less than 10% found in bottom sediments. In a 

pond, 70% of diethyl phthalate would be in the water column with 30% found in the bottom sediment 

(Wolfe et al. 1980a). 

Major transport-mechanisms for diethyl phthalate include sorption onto suspended particulates and 

biota and possibly the formation of complexes with humic substances in the water (EPA 1979). Based 

on a Henry’s law constant of 7.8x10-7 atm m3

/mol, volatilization from water is not expected to be a 

significant removal process for diethyl phthalate (EPA 1989). 
DIETHYL PHTHALATE 76 

5. POTENTIAL FOR HUMAN EXPOSURE 

Studies of phthalate esters in surface sediment samples of the River Mersey in England (Preston and 

Al-Omran 1989) showed that, in one sample, diethyl phthalate was enriched in the coarser sediment 

fractions with high lipid content (0.102 μg/g dry weight, background 0.050 μg/g); however, in another 

sample, diethyl phthalate was more concentrated in the finer particle fraction (0.060 μg/g, background 

0.013 μg/g). The greater presence of diethyl phthalate in the sediment with high lipid content suggests 

that hydrophobic adsorption can occur, although possible mechanisms were not discussed. A study of 

the presence of diethyl phthalate in waste water and sediments from Canadian coal mines found that 

diethyl phthalate added to distilled water over mine sediment would remain in the water column rather 

than partition onto the sediment (Atwater et al. 1990). 

Diethyl phthalate adsorbs to suspended particles in marine waters, with the maximum adsorption 

occurring onto particles of 353-698 μm in size (Al-Omran and Preston 1987). 

Soil 

Diethyl phthalate is fairly mobile in soil, based on tests of the absorption of diethyl phthalate from 

double-distilled water onto composite soil (1.59% organic carbon); diethyl phthalate moved through 

the soil at half the rate of water (Russell and McDuffie 1987). In undisturbed soil columns, phthalate 

ester transport was determined by both physical and chemical nonequilibrium processes (Zurmuhl et al. 

1991). In general, the chemical disequilibrium was greater in a soil with greater organic carbon 

content than in a low organic carbon-content soil. The investigators attributed this finding to the 

greater sorption capacity of the former soil type. The mobility of diethyl phthalate through the soil 

columns was greater than the mobility of the more lipophilic dibutyl, butyl benzyl, and di(2­

ethylhexyl) phthalate esters. 

The presence of diethyl phthalate in groundwater in Phoenix, Arizona, was studied using a rapid 

infiltration system. Diethyl phthalate, present in the sewage infiltrate at 0.231 μg/L, was reduced to 

0.017 μg/L or less (detected but too low to be quantified) in groundwater samples taken from a 60-foot 

well depth (Tomson et al. 1981). Further studies with this system showed that infiltrate basin water 

containing initial concentrations of diethyl phthalate of 10-20 μg/L decreased by 75-95% after 

infiltration. Removal was greatest in water taken from deeper sampling wells (30 versus 18 feet). The 
 

DIETHYL PHTHALATE 77 

5. POTENTIAL FOR HUMAN EXPOSURE 

ultimate rate of removal was independent of whether the basin water had been chlorinated or not. 

However, chlorination appeared to speed the removal of diethyl phthalate in the shallow well (Bouwer 

et al. 1984). The removal of diethyl phthalate from waste waters using soil as a sorption medium was 

not confirmed by Hutchins et al. (1983), who found that treatment of secondary effluents containing 

diethyl phthalate at 0.19 μg/L by a rapid infiltration system in Fort Polk, Louisiana, resulted in the 

presence of diethyl phthalate in the associated groundwater at 0.26 μg/L. It was suggested that this 

may, in part, be due to the low concentration of diethyl phthalate, which underutilized the 

biodegradation capacity of the soil column. The removal of diethyl phthalate from waste water by 

absorption or biodegradation in the soil is dependent on the soil type and, in some cases, on its ability 

to be transported through soils to underlying groundwaters. 

5.3.2 Transformation and Degradation 

5.3.2.1 Air 

Ultraviolet absorption spectra for diethyl phthalate suggest that, although there is a potential for 

photodegradation in the atmosphere, this is not a significant removal process (EPA 1989). Diethyl 

phthalate may exist in the atmosphere in vapor form and adsorb to airborne particulates. Diethyl 

phthalate reacts photochemically with hjrdroxyl radicals in the air with an estimated half-life of 

22.2 hours (HSDB 1994). 

5.3.2.2 Water 

The use of a computer-simulated model for aquatic ecosystems (EXAMS) indicated that, compared 

with biodegradation, .abiotic hydrolysis and photolysis are minor degradation processes for diethyl 

phthalate in most aquatic ecosystems. Only in an oligotrophic lake was photolysis a more significant 

degradation process than biodegradation for diethyl phthalate. In a river system with a detention time 

of 1 hour, diethyl phthalate would be virtually unchanged and would be lost only by export (Wolfe et 

al. 1980a). The hydrolysis half-life for diethyl phthalate in water at pH 7.0 and 30°C is estimated to 

be greater than 18 years (EPA 1979). The oxidative half-life for alkyl phthalates is estimated to 

exceed 3 years (EPA 1989). Lewis et al. (1984b) studied the degradation of diethyl phthalate in a 
DIETHYL PHTHALATE 78 

5. POTENTIAL FOR HUMAN EXPOSURE 

simulated aquatic ecosystem consisting of microbial growth attached to submerged surfaces or 

suspended as mats or streamers in the water (aufwuchs). Diethyl phthalate did not adsorb to any 

aquatic surfaces (including autoclaved aufwuchs, sediment, and equipment surfaces). It was virtually 

untransformed by photolysis (<l%), and only 10 μg/L of 191 μg/L diethyl phthalate was lost by 

hydrolysis in 12 hours at a pH of 10. Degradation occurred as a result of bacterial transformation 

(95-99% of loss), which was dependent on the surface area colonized by the bacteria and unaffected 

by dissolved organic carbon, nitrogen, and phosphorus. However, as bacterial densities increased in 

the aufwuchs, the rate of transformation decreased, possibly as a result of the increased growth of 

bacteria that were unable to degrade diethyl phthalate (Lewis and Holm 1981). Further studies using 

laboratory microcosms and field-collected microbiota found that while diethyl phthalate was degraded 

in all of the laboratory studies, degradation occurred at only 2 of 10 field sites. The degradation rates 

were similar, however, for both ecosystems (Lewis et al. 1985). Diethyl phthalate was degraded in 

3 hours by Brevibacterium sp. isolated from several lakes and rivers in Georgia. The rate of 

degradation was increased by the addition of spent fungal culture medium to the bacterial culture 

(Lewis et al. 1984a). 

A phthalate ester-hydrolyzing enzyme purified from Nocardia erythropolis, a bacterium found in soils 

and waste waters, had relative enzyme activity using diethyl phthalate of 76.3% (relative to 100% 

enzyme activity for di-[2-ethylhexyl] phthalate). Diethyl phthalate was hydrolyzed to the free phthalic 

acid and alcohol. The phthalic acid would be metabolized by intradiol fission via protocatechuic acid 

to β-ketoadipic acid (Kurane 1986). The soil and waste-water bacterium Pseudomonas acidovoruns 

was found to degrade diethyl phthalate with a half-life of 10.5 days at 30°C (initial concentration of 

3,000 mg/kg) (Kurane et al. 1977). Karegoudar and Pujar (1984b, 1985) isolated two types of 

bacteria, Micrococcus varians and Bacillus sphaericus, from industrial waste water and sewage ponds. 

These bacteria were able to grow aerobically using diethyl phthalate as the sole carbon source. 

Diethyl phthalate is hydrolyzed by the bacterial enzymes to free phthalic acid via the intermediate 

monoester (Karegoudar and Pujar 1984a). Other bacteria found in sewage treatment facilities are also 

able to degrade diethyl phthalate (Gibbons and Alexander 1989). 
DIETHYL PHTHALATE 79 

5. POTENTIAL FOR HUMAN EXPOSURE 

Aerobic degradation of diethyl phthalate by acclimated soil and activated sewage sludge microbes was 

studied by using carbon dioxide (CO2) evolution. Primary biodegradation (loss of parent ester) of 

diethyl phthalate was greater than 99% with a lag phase of 2.3 days, and ultimate biodegradation (CO2 

evolution) was 95%. The half-life for the compound under these conditions was 2.21 days (Sugatt et 

al. 1984). Complete bacterial acclimation to graded concentrations (50 to 410 mg/L) of diethyl 

phthalate was found in an aerobic, activated sludge system (Tokuz 1991). More than 94% of diethyl 

phthalate, however, was biodegraded within 1.1 days using semicontinuous activated sludge treatment 

(O’Grady et al. 1985). Other studies of the aerobic biodegradation of diethyl phthalate indicated that 

using settled domestic waste water as the microbial inoculum in the static culture flask test and 5 or 

10 mg/L of diethyl phthalate, degradation was complete within 1 week of incubation in the dark 

(Tabak et al. 1981). Diethyl phthalate was degraded by activated sludge with an estimated half-life of 

10.5 minutes (Urushigawa and Yonezawa 1979). Investigators found virtually complete primary and 

ultimate biodegradation of diethyl phthalate using semi-continuous sludge and shake flask procedures, 

respectively (Monsanto Corporation 1983). 

The degradation of diethyl phthalate by sewage sludge bacteria indicated that aerobic degradation is 

more rapid than anaerobic degradation; however, aerobic degradation is significantly reduced by low 

dissolved oxygen levels and low temperature. Under less-than-optimal aerobic conditions and 

anaerobic conditions, facultative bacteria will outcompete aerobic bacteria in degrading diethyl 

phthalate Zhang and Reardon 1990). 

All of the diethyl phthalate added to river water at 25 mg/L was degraded within 6 days, while after 

14 days in relatively clean ocean water the degradation rate was between 14% and 20%, and in 

polluted ocean water the degradation rate was 68% (Hattori et al. 1975). Primary degradation using 

river die-away procedures was virtually complete (Monsanto Corporation 1983). 

Diethyl phthalate was aerobically degraded by two of three marine bacteria isolated from waters near 

the Mississippi River delta region (Taylor et al. 1981). 

More than 98% of diethyl phthalate was degraded (original concentration of 4 mg/L) in less than 

8 days by anaerobic sewage sludge (Ziogou et al. 1989). Under anaerobic conditions, diethyl phthalate 
 

DIETHYL PHTHALATE 80 

5. POTENTIAL FOR HUMAN EXPOSURE 

was degraded to CO2 and methane (CH,) (greater than 75% of theoretical CH, production) by a 10% 

sludge solution from a primary digester and partially degraded (30-75% of theoretical CH, production) 

by a 10% sludge solution from a secondary digester (Shelton and Tiedje 1984). Diethyl phthalate 

removal was greater than 90% within 1 week with undiluted sludge (Shelton et al. 1984). 

In other studies of the anaerobic degradation of diethyl phthalate, municipal sewage sludge mixed with 

20 mg/L of diethyl phthalate yielded between 33% and 55% of the theoretical methane production 

after 6 days of incubation. Higher concentrations of diethyl phthalate (100 and 200 mg/L) strongly 

inhibited methane production regardless of the length of the incubation period (O’Conner et al. 1989). 

The degradation of diethyl phthalate under anaerobic conditions appears to be, in part, dependent on 

the type of sewage sludge used. A comparison of anaerobic degradation using two municipal sludges 

showed that one did not mineralize diethyl phthalate after 8 weeks of incubation, whereas a second 

sludge showed 32% of theoretical methane production in 4 weeks (Horowitz et al. 1982). 

5.3.2.3 Soil 

Degradation of diethyl phthalate applied to soil at an initial concentration of 1 mg/kg was 4% at 

24 hours, 11% at 48 hours, 40% at 72 hours, and 86% at 120 hours. Addition of landfill leachate to 

the soil significantly increased the degradation rate with all of the diethyl phthalate being degraded 

within 72 hours (Russell et al. 1985). The biodegradation rate of an aerobic microbial strain in batch 

fermentation and sandy soil column experiments was facilitated at 25°C (relative to 5°C or 15oC) and 

at dissolved oxygen concentrations of 0.85 to 8.5 mg/L (Reardon and Zhang 1992). The degradation 

kinetics of a facultative strain were inhibited by anaerobic conditions, unaffected by the dissolved 

oxygen level, and greater at 15°C than at 25°C under aerobic conditions. Differences in 

biodegradation kinetics were related to the tighter adsorption of the facultative strain. 

A 2-year study of slow-rate land treatment using waste waters containing diethyl phthalate found that 

diethyl phthalate was relatively nonvolatile during spray application. Applied at a rate of 56 μg/L to 

sandy loam and silty loam soils, diethyl phthalate accumulated in the top 5 cm of sandy loam soils to 

concentrations of 1,000-6,700 ng/g and on the surface of the silty soil from below the detection limit 

(1 ng/g) to 2,200 ng/g dry soil. Diethyl phthalate was present in greater concentrations at greater 
DIETHYL PHTHALATE 81 

5. POTENTIAL FOR HUMAN EXPOSURE 

depths in the sandy soil. Although diethyl phthalate was detectable in each soil type down to a depth 

of 150 cm, it was not detected to any significant degree in the percolate from either soil. Diethyl 

phthalate did not appear to volatilize from the soil during spray application of the waste water to the 

soil or thereafter (Parker and Jenkins 1986). 

The soil fungus Fusarium 2P3 was able to use diethyl phthalate as a growth substrate with growth 

being constant after 4 days of incubation (Klausmeier and Jones 1960). 

5.4 LEVELS MONITORED OR ESTIMATED IN THE ENVIRONMENT 

Analytical data regarding diethyl phthalate concentrations in environmental media must be interpreted 

with caution, because of the extensive contamination of laboratory glassware with these chemical 

agents (Lopez-Avila et al. 1990). 

5.4.1 Air 

Diethyl phthalate has been measured in the indoor air of a telephone switching office and in outdoor 

air in Newark, New Jersey, at concentrations ranging from 1.60 to 2.03 μg/m3

 and from 0.40 to 

0.52 μg/m3

, respectively, during a 43-day sampling period (Shields and Weschler 1987). 

5.4.2 Water 

Diethyl phthalate was found in the finished drinking water of 6 of 10 U.S. cities at concentrations of 

0.01 μg/L (Seattle, Washington; Philadelphia, Pennsylvania; New York, New York), 0.04 μg/L 

(Lawrence, Kansas), 0.1 μg/L (Cincinnati, Ohio), and 1.0 μg/L (Miami, Florida) (Keith et al. 1976). 

Diethyl phthalate was identified but not quantified in the Cincinnati drinking water by reverse osmosis 

(Kopfler et al. 1977). A survey of 39 public water wells identified diethyl phthalate at a maximum 

concentration of 4.6 μg/L (EPA 1989). 
DIETHYL PHTHALATE 82 

5. POTENTIAL FOR HUMAN EXPOSURE 

The Storage and Retrieval (STORET) database maintained by EPA contains over 80 million data 

points on water quality. Diethyl phthalate has been found at a median concentration of less than 

10 μg/L in 9.9% of the industrial effluent samples and in 3.0% of the ambient water samples. It has 

also been detected in 10.0% of all sediment samples at a median concentration of less than 500 μg/kg 

dry weight and in 6.0% of aquatic biota samples at a median concentration of less than 2.500 mg/kg 

wet weight (Staples et al. 1985). 

Water samples taken from Galveston Bay, Texas, contained diethyl phthalate, as well as other 

phthalate esters, at unspecified levels; they were among the most abundant pollutants found in the 

samples (Ray and Giam 1984). Surface water samples collected along the length of the Mississippi 

River contained diethyl phthalate in significant concentrations: 190 ng/L at Lake Itasca, Minnesota 

(the source of the Mississippi River); 84 ng/L 25 miles below the inflow of the Ohio River at Cairo, 

Illinois; 350 ng/L 20 miles below Memphis, Tennessee; and 63 ng/L in the industrial corridor in New 

Orleans, Louisiana (DeLeon et al. 1986). Diethyl phthalate concentrations ranged from less than 

1 ng/L to 430 ng/L in subsurface water samples from North Sea estuaries that had been polluted by 

industrial waste (Law et al. 1991). Diethyl phthalate was also detected at 0.7 μg/L in ebb tide water 

of the Inner Harbor Navigation Canal of Lake Pontchartrain, Louisiana (McFall et al. 1985b). 

Diethyl phthalate has been detected in the treated waste waters from various manufacturing facilities: 

textile manufacturing plants at 3.2 μg/L diethyl phthalate (Walsh et al, 1980); a tire manufacturing 

plant at 60 μg/L (Jungclaus et al. 1976); and pulp and paper manufacturers at 50 μg/L (Brownlee and 

Strachan 1977; Voss 1984). River water samples from the lower Tennessee River taken below the 

Calvert City, Kentucky, chemical complex were found to have 11.2 μg/L diethyl phthalate (Goodley 

and Gordon 1976). Diethyl phthalate was detected at 21 ng/L in tap water from the Kitakyushu area 

of Japan. Sources were considered to be domestic sewage and industrial waste (Akiyamaet al. 1980). 

River water samples and sewage effluent collected in 1984 from the Rivers Irwell and Etherow near 

Manchester, England, contained 0.4-0.6 μg/L of diethyl phthalate (Fatoki and Vernon 1990). Cooling 

water discharges from electric generating plants along the California coast contained diethyl phthalate 

in both chlorinated effluents (0.10 μg/L) and unchlorinated effluents (0.01 μg/L). Ocean samples taken 

1 km from the discharge site contained 0.06 μg/L of diethyl phthalate (Grove et al. 1985). The 
DIETHYL PHTHALATE 83 

5. POTENTIAL FOR HUMAN EXPOSURE 

Nationwide Urban Runoff Program, conducted in 1982, detected diethyl phthalate in 4% (3 locations) 

of 86 samples at concentrations of 0.5-l 1.0 μg/L (Cole et al. 1984). 

Diethyl phthalate was found in 28 of 47 waste-water samples taken from a Canadian coal mine with 

6 of the positive samples having concentrations exceeding 10 μg/L. Diethyl phthalate was also found 

in sediments associated with the mine at concentrations of between 5 and 30 μg/g (Atwater et al. 

1990). 

Diethyl phthalate has been detected in sediment samples taken from the Chesapeake Bay at 

concentrations ranging from 11 to 42 μg/kg. A sediment sample taken from the Chester River (which 

flows into the Chesapeake Bay) contained 26 μg/kg, and a sediment sample from a waste-water 

holding pond adjacent to a plasticizer manufacturing plant outfall near the river had less than 100 

μg/kg (Peterson and Freeman 1982a). Further investigation of the Chester River to determine if a 

plasticizer manufacturing plant was responsible for elevating concentrations of phthalate esters in the 

river showed that although diethyl phthalate concentrations ranged from 11 to 44 μg/kg, concentrations 

could not be correlated with intentional or unintentional discharges from the plant (Peterson and 

Freeman 1984). 

Sediment samples taken from tributaries of the Susquehanna River ranged from just above background 

to 35 μg/kg diethyl phthalate (Russell and McDuffie 1983). Diethyl phthalate has also been detected 

in sediment from the San Luis Pass in Galveston Bay, Texas, at an average concentration of 5 μg/kg 

dry weight (Murray et al. 1981). Sediment samples from the Inner Harbor Navigation Canal and Chef 

Menteur tributary to Lake Pontchartrain, Louisiana, contained diethyl phthalate at concentrations of 

25 μg/kg and 65 μg/kg dry weight, respectively (McFall et al. 1985a). 

Sediment core samples taken from the Chesapeake Bay below Baltimore Harbor, Maryland, contained 

diethyl phthalate at levels that reflected increasing water concentrations as a result of industrial 

production of phthalates. The sample taken closest to Baltimore had diethyl phthalate concentrations 

of 19 μg/kg at a core depth corresponding to the years 1923-1929. These levels remained relatively 

constant until 1963-1968, when the diethyl phthalate level jumped to 35 μg/kg; diethyl phthalate was 

detected at the surface core level of 42 μg/kg from 1974-1979. A core sample taken further down 
DIETHYL PHTHALATE 84 

5. POTENTIAL FOR HUMAN EXPOSURE 

the bay at a core depth corresponding to the years 1884-1892 (110-120 cm in depth) had a diethyl 

phthalate concentration of 3.1 μg/kg. Sediment concentrations increased chronologically until they 

reached a maximum of 22 μg/kg for the period 1972-1979. Production volumes were correlated 

(R=0.83) for both the sediment nearest Baltimore and for the more distant sample (R=0.60) (Peterson 

and Freeman 1982b). 

Diethyl phthalate levels in water from the Rhine River in the Netherlands ranged from less than 0.15 

to approximately 0.45 μg/L over a 12-day period; on days 7 through 11, diethyl phthalate 

concentrations in suspended particulate matter from the river stayed relatively constant at 0.1 mg/kg. 

Water samples and suspended particulate matter from Lake Yssel, also in the Netherlands, contained 

diethyl phthalate at 0.02-0.08 μg/L and <0.1-0.8 mg/kg, respectively (Ritsema et al. 1989). River 

water samples and sewage effluent collected in 1984 from the Rivers Irwell and Etherow near 

Manchester, England, contained 0.4-0.6 μg/L of diethyl phthalate (Fatoki and Vernon 1990). 

5.4.3 Soil 

No studies were located on the levels of diethyl phthalate found in soil. 

5.4.4 Other Environmental Media 

Fish collected from Great Lakes tributaries in Wisconsin and Ohio during 1981 had diethyl phthalate 

in all tissue samples at concentrations of less than 0.02 mg/kg to less than 0.30 mg/kg (DeVault 1985). 

Lake trout (Salvelinus namaycush) and whitefish (Coregonus culpeaforms) taken from Lake Superior 

near Isle Royale, Michigan had elevated levels of diethyl phthalate (0.5 and 2.2 μg/g, respectively) 

compared with lake trout and whitefish taken from other parts of Lake Superior (both values below the 

level of quantification of 0.001 μg/g wet weight). Fish taken from Siskiwit Lake on Isle Royale, 

Michigan, a pristine area supposedly unaffected by human activity, also had relatively high 

concentrations of diethyl phthalate in their tissue, 0.4 μg/g for lake trout and 1.7 μg/g for whitefish 

(Swain 1978). Diethyl phthalate was detected but not quantified in whole fish taken from 13 Lake 

Michigan tributaries and Grand Traverse Bay in Michigan (Camanzo et al. 1983). 


DIETHYL PHTHALATE 87 

5. POTENTIAL FOR HUMAN EXPOSURE 

factory; and l-3 μg/m3 in the extrusion area of an electrical cables insulation plant (Cocheo et al. 

1983). 

The National Occupational Exposure Survey, conducted between 1981 and 1983, estimated that 

239,149 workers (including 108,580 women) in 16,408 facilities were exposed to diethyl phthalate in 

the workplace in 1980 with employees in the personal services (hairdressers, cosmetologists) and 

health services industries having the greatest potential exposure (NOES 1990). The American 

Conference of Governmental Industrial Hygienists has established an 8-hour time-weighted average 

threshold limit value of 5 mg/m3 for diethyl phthalate (ACGIH 1990). 

5.6 POPULATIONS WITH POTENTIALLY HIGH EXPOSURES 

People receiving medical treatments that involve the use of polyvinyl chloride tubing may be exposed 

to diethyl phthalate as a result of its leaching from the tubing. Diethyl phthalate was found to be 

leached from polyvinyl chloride dialysis tubing containing aqueous electrolyte solution, human blood, 

or bovine plasma perfusates. The tubing was perfused with the aqueous electrolyte solution for 

22-96 hours, resulting in a level of diethyl phthalate ranging from 18 to 26 mg/L as determined by 

ultraviolet spectrometry. Even with only 1 hour of perfusion, diethyl phthalate levels reached 20 mg/L 

although the levels dropped with extended perfusion time. When the tubing was perfused with either 

human blood or bovine plasma for 8 hours. infrared spectrometry showed diethyl phthalate levels 

2-4 times greater than with water, suggesting that diethyl phthalate has greater solubility in lipidcontaining fluids than in inorganic solutions (Christensen et al. 1976). 

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 diethyl phthalate 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 diethyl phthalate. 
DIETHYL PHTHALATE 88 

5. POTENTIAL FOR HUMAN EXPOSURE 

The following categories of possible data needs have been identified by a joint team of scientists from 

ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that, if met, 

would reduce 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. 

5.7.1 Identification of Data Needs 

Physical and Chemical Properties. The physical and chemical properties of diethyl phthalate are 

sufficiently well defined to allow assessments of the environmental fate of diethyl phthalate to be 

made. Therefore, no additional information is needed at this time. 

Production, Import/Export, Use, and Release and Disposal. Production, import, use, and 

release of diethyl phthalate are thoroughly described in the literature. There are no available data 

reporting U.S. export volumes of diethyl phthalate. The data indicate that the potential for human 

exposure is considerable and is most likely to occur from inhalation of contaminated air or ingestion 

of contaminated drinking water or foods. The two methods of disposal mentioned in the literature are 

landfill and incineration (HSDB 1994). More information on the amounts of diethyl phthalate 

disposed of by each means and the efficiency of each method would be helpful in estimating potential 

exposure. 

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. However, diethyl phthalate is not currently included in the Toxics Release 

Inventory as a reportable chemical. 
DIETHYL PHTHALATE 89 

5. POTENTIAL FOR HUMAN EXPOSURE 

Environmental Fate. Diethyl phthalate released to air, water, or soil partitions to sediment or is 

adsorbed to organic matter in water (EPA 1979, 1989; Tomson et al. 1981; Wolfe et al. 1980a). In 

soils with low organic content, diethyl phthalate may be relatively mobile and consequently may 

percolate down to groundwater (Russell and McDuffie 1986). Diethyl phthalate is aerobically 

biodegraded in soils and with sewage sludge (O’Grady et al. 1985; Sugatt et al. 1984; Tabak et al. 

1981; Urishigawa and Yonezawa 1979). It is also biodegraded under anaerobic conditions but at a 

slower rate (Zhang and Reardon 1990). Up to 75% of the total releases of diethyl phthalate potentially 

result from low-temperature burning at hazardous disposal sites (HSDB 1994). Volatilization will be 

slow because of low vapor pressure. Vapors will react with photochemically generated hydroxyl 

radicals, with an estimated half-life of 22.2 hours at 25°C (HSDB 1994). Further information is 

needed on the volatilization of diethyl phthalate from plastic and other products and its subsequent 

transformation in air. This information would be useful in identifying the most important pathways of 

human exposure to diethyl phthalate. 

Bioavailability from Environmental Media. The limited toxicity data available in animals 

provide indirect evidence that uptake of diethyl phthalate occurs following ingestion (Brown et al. 

1978; Lamb et al. 1987; Smyth and Smyth 1962). Additional information is needed on the absorption 

of diethyl phthalate as a result of inhalation of contaminated air. 

Food Chain Bioaccumulation. Diethyl phthalate has been detected in aquatic organisms and has 

been found to bioconcentrate modestly in these organisms (Camanzo et al. 1983; DeVault 1985; 

McFall et al. 1985a). The database is, however, too limited to determine a representative range of 

bioaccumulation potential throughout the food chain. Further data on the accumulation potential for 

diethyl phthalate, including biomagnification in terrestrial and aquatic food chains, does not seem 

necessary. 

Exposure Levels in Environmental Media. Diethyl phthalate has been detected in ambient and 

workplace air (Shields and Weschler 1987), drinking water (EPA 1989; Keith et al. 1976; Kopfler et 

al. 1977), surface waters (Fatoki and Vernon 1990; Ray and Giam 1984; Staples et al. 1985), 

sediments (Staples et al. 1985), and food (Castle et al. 1988; Giam and Wong 1987); however, limited 
DIETHYL PHTHALATE 90 

5. POTENTIAL FOR HUMAN EXPOSURE 

current monitoring data were found. Diethyl phthalate has been detected in the surface waters, 

groundwater, and soil samples taken at a limited number of NPL sites. Additional information on the 

concentrations of diethyl phthalate in hazardous waste-site media is needed. This information will be 

helpful in identifying the most important exposure pathways for populations living near these sites. 

Exposure Levels in Humans. Detection of diethyl phthalate in human semen, tissue, and fat has 

been used as an indicator of exposure to diethyl phthalate (Giam and Chan 1976; Van Lierop and Van 

Veen 1988; Waliszewski and Szymczymski 1990). Because diethyl phthalate is readily absorbed from 

the gastrointestinal tract, additional information on the concentration of diethyl phthalate in biological 

tissue and fluids of populations living in the vicinity of NPL sites would be helpful in assessing the 

extent to which these populations have been exposed to diethyl phthalate. 

Exposure Registries. No exposure registries for diethyl phthalate were located. This substance is 

not currently one of the compounds for which a subregistry has been established in the National 

Exposure Registry. The substance will be considered in the future when chemical selection is made 

for subregistries to be established. The information that is amassed in the National Exposure Registry 

facilitates the epidemiological research needed to assess adverse health outcomes that may be related 

to the exposure to this substance. 

5.7.2 On-going Studies 

Remedial investigations and feasibility studies currently being conducted at the NPL sites contaminated 

with diethyl phthalate will add to the database on exposure levels in environmental media and in 

humans and will contribute information for exposure registries. Investigations at these sites will also 

increase the current knowledge regarding the transport and transformation of diethyl phthalate at 

hazardous waste sites. No other long-term research studies regarding the environmental fate and 

transport of diethyl phthalate or the occupational and general population exposure to this compound 

were identified. 
DIETHYL PHTHALATE 91 

6. ANALYTICAL METHODS
 

The purpose of this chapter is to describe the analytical methods that are available for detecting and/or 

measuring and monitoring diethyl phthalate 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 diethyl phthalate. Rather, the intention is to identify well-established methods that are used as 

the standard methods of analysis. Many of the analytical methods used to detect diethyl phthalate 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 are those that are approved by groups such as the Association of Official Analytical Chemists 

(AOAC) and the American Public Health Association (APHA). Additionally, analytical methods are 

included that refine previously used methods to obtain lower detection limits, and/or to improve 

accuracy and precision. 

6.1 BIOLOGICAL MATERIALS 

No analytical methods were located for measuring diethyl phthalate in the serum, blood, or urine of 

humans or animals. Gas chromatography (GC), combined with electron capture detection (ECD) or 

mass spectroscopy (MS), has been used to measure diethyl phthalate in human semen (Waliszewski 

and Szmczymski 1990), animal fat (van Lierop and van Veen 1988), and animal tissues (Giam and 

Chan 1976), but the data are too limited to allow a comparison of methods. Because phthalates are so 

pervasive in plastics and elsewhere in the laboratory environment, rigorous control measures are 

needed to prevent contamination of the sample and to maintain a low background. These procedures 

include prewashing columns, use of equipment with purified solvents, and baking at high. temperatures 

to remove organic materials. Investigators have found that contamination from laboratory glassware 

limits the analysis of phthalate esters in the parts-per-billion to parts-per-trillion range and recommend 

concurrent controls for all analytical procedures (Lopez-Avila et al. 1990). Organochlorine pesticides 

and polychlorinated biphenyls (PCBs) cause interference in diethyl phthalate analysis by ECD, 

requiring their removal. 
DIETHYL PHTHALATE 92 

6. ANALYTICAL METHODS 

Preparation steps include extraction with petroleum ether, followed by Florisil® chromatography 

(Giam and Chan 1976; Waliszewski and Szymczymski 1990). The detection limit for semen was 

0.04 mg/kg, and recovery was excellent (95%) (Waliszewski and Szymczymski 1990). Van Lierop 

and Van Veen (1988) recovered diethyl phthalate from fat by purging with nitrogen at high 

temperature, collecting the volatilized material on Tenax®, and extracting with hexane. This method 

was designed to avoid time-consuming methods for removing residual fat, but the low recovery 

(l-10%) and high detection limit (10 mg/kg) limit its usefulness to crude qualitative analysis. 

Burns et al. (1981) described a method for measuring di-(2-ethylhexyl) phthalate in fish lipids with 

79-86% recovery, and suggest it could also be used for measuring diethyl phthalate. Detection is by 

GC/ECD, with a background of 1 ng/injection. The ability to differentiate among different phthalate 

esters was sacrificed for excellent sensitivity (0.1 pg/injection) and good recovery (70-l 10%) in a 

method that involves hydrolyzing all phthalate esters to phthalic acid and converting the acid to 

bis(2,2,2-trifluoroethyl) phthalate, which has an increased ECD response (Takeshita et al. 1977). Table 

6-l summarizes methods available for measuring diethyl phthalate in biological samples. 

6.2 ENVIRONMENTAL SAMPLES 

Diethyl phthalate in environmental samples is most commonly measured using GC with detection by 

MS preferred because it is less prone to interference than is ECD. Other detection methods include 

high-performance liquid chromatography (HPLC) or liquid chromatography with ultraviolet (UV) 

detection. As with biological samples, rigorous cleaning of reagents and equipment is necessary to 

prevent contamination. Methods that use a minimum number of steps and minimal amounts of 

solvents and column materials also help minimize contamination. 

Diethyl phthalate can be collected by pumping an air sample through ethylene glycol (Thomas 1973) 

or directly through an activated Florisil® column (Giam and Chan 1976). Measurements in air can 

also be done by passive sampling on charcoal, which is less expensive than active sampling but 

requires much longer sampling times. Reproducibility for the passive sampling technique was 

DIETHYL PHTHALATE 94 

6. ANALYTICAL METHODS 

l0-15% of the mean value, and the detection limit was estimated to be 0.2 μg/m3 (Shields and 

Weschler 1987). The detection limit for the active sampling techniques was 10 ng per injection, with 

90% recovery using ethylene glycol trapping (Giam and Chan 1976; Thomas 1973). 

Solid phase extraction (SPE) methods using reverse-phase columns are particularly desirable for 

analyzing liquid samples because they eliminate the need for large solvent volumes and the resulting 

potential for contamination (Burkhard et al. 1991; Ritsema et al. 1989). SPE using a membrane 

impregnated with reverse-phase particles achieved 85-100% recovery (Hagen et al. 1990). Ritsema et 

al. (1989) found mass selective detection (MSD) much more selective than ECD and reported 85% 

recovery and a detection limit of 10 ng/L. Other methods involve hexane extraction followed by 

HPLC or GC. The detection limit of the UV detectors used for HPLC (20 ng/injection) is much 

higher than that of GC/ECD (0.5 ng/injection) (Payne and Benner 1981). Lopez-Avila et al. (1989) 

replaced the Florisil® column used in EPA method 3620 (EPA 1986b) with a smaller disposable 

Florisil®cartridge to reduce background and achieved 96% recovery when cartridges were not spiked 

with potential interfering agents. The cartridge could be used to separate diethyl phthalate from 

organochlorine pesticides, diesel hydrocarbons, and corn oil. In a later study, these investigators 

obtained a 55-70% recovery from a solid matrix, after alumina column cleanup (Lopez-Avila et al. 

1991). Method 1625 of EPA’s Industrial Technology Division is part of a group of broad-range 

methods for measuring pollutants in waste water. It includes continuous liquid-liquid extraction, 

followed by gel permeation chromatography and detection by GC/MS (Telliard 1990). EPA (198la) 

achieved over 100% recovery using Florisil® or alumina columns and GC/ECD, with a sensitivity of 

0.13 ng/injection, but found the method inappropriate for certain waste waters because of high 

interference. 

Sludge, sediment, and soil samples are extracted with moderately nonpolar solvents ands.leaned up by 

liquid chromatography (Ritsema et al. 1989; Russell and McDuffie 1983). Soxhlet® extraction or 

extraction using ultrasonication was sometimes used to improve efficiency; some authors found 

ultrasonic extraction resulted in lower blanks and slightly higher efficiency than Soxhlet® extraction 

(Peterson and Freeman 1982a; Zurmiihl 1990). Recovery was over 80% for the few techniques where 

recovery was reported. Sensitivity was reported for only a few of the methods, where it ranged from 

0.1 to 5.3 μg/kg. Diethyl phthalate has been detected in cosmetic preparations using liquid 
DIETHYL PHTHALATE 95 

6. ANALYTICAL METHODS 

chromatography and UV detection, or by direct injection onto the gas chromatograph with flame 

ionization detection (FID) (Hancock et al. 1966). Diethyl phthalate was detected in pharmaceutical 

tablets by thin-layer chromatography (TLC) and HPLC/UV (Cafmeyer and Wolfson 1991). Table 6-2 

summarizes methods available for measuring diethyl phthalate in environmental samples. 

High temperature continuous counter-current gas-liquid chromatography is an effective methodology 

for separating mixtures of high boiling point organics (Watabe et al. 1992). At a column temperature 

of 200°C dimethyl and diethyl phthalates were separated to purities of 99.96% and 99.69% 

respectively. 

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 diethyl phthalate 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 diethyl phthalate. 

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. 




DIETHYL PHTHALATE 100 

6. ANALYTICAL METHODS 

6.3.1 Identification of Data Needs 

Methods for Determining Biomarkers of Exposure and Effect. No methods were located for 

measuring diethyl phthalate or its metabolites in animal or human serum, blood, or urine. Methods are 

available for determining diethyl phthalate in human semen and animal fat and muscle (Giam and 

Chan 1976; Van Lierop and Van Veen 1988; Waliszewski and Szymczymski 1990). Because the 

available data indicate that diethyl phthalate exposure is associated with negligible toxicological 

potential, additional studies to identify specific biomarkers of exposure appear unnecessary. 

Consequently, a data need for identifying biomarkers does not exist. However, additional metabolic 

and/or comparative toxicokinetic studies, recommended in Section 2.9.2 to elucidate high-dose effects, 

may incidentally reveal a specific biomarker of exposure. 

Methods for Determining Parent Compounds and Degradation Products in 

Environmental Media. Methods exist for measuring diethyl phthalate in a variety of 

environmental media, including air (Shields and Weschler 1987), water (EPA 1989; Fatoki and Vernon 

1990; Keith et al. 1976; Kopfler et al. 1977; Ray and Giam 1984; Staples et al. 1985), waste water 

(EPA 1981a), sludge (Zurmtihl 1990), sediment (Peterson and Freeman 1982a; Russell and McDuffie 

1983), soil (Russell and McDuffie 1983), and cosmetics (Hancock et al. 1966). Recovery for most 

methods is over 80%. Furthermore, the failure to identify signs or symptomology of intoxication 

suggests that increased analytical sensitivity for biological or environmental samples is unnecessary. 

Consequently, the refinement of current analytical procedures appears unnecessary. 

6.3.2 On-going Studies 

No on-going studies regarding analytical methods were located for diethyl phthalate. 
DIETHYL PHTHALATE 101 

7. REGULATIONS AND ADVISORIES
 

The national and state regulations and guidelines regarding diethyl phthalate in air, water, and other 

media are summarized in Table 7-l. No international regulations or guidelines were located. 

ATSDR has not derived an MRL for diethyl phthalate. EPA (IRIS 1994) assigned diethyl phthalate a 

reference dose (RfD) of 80x10-1 mg/kg/day with an uncertainty factor of 1,000 based on decreased 

growth rate, food consumption, and altered organ weights (Brown et al. 1978). EPA (IRIS 1994) has 

assigned diethyl phthalate a weight-of-evidence carcinogenic classification of D, which indicates that 

diethyl phthalate is not classifiable as to human carcinogenicity. Diethyl phthalate is on the list of 

chemicals appearing in “Toxic Chemicals Subject to Section 313 of the Emergency Planning and 

Right-to-Know Act of 1986” (EPA 1987e, 1988c). Diethyl phthalate is designated as a hazardous 

substance (EPA 1978, 1987d) and is subject to groundwater monitoring requirements (EPA 1987a, 

1987b). 



____________________ 

DIETHYL PHTHALATE 105 

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DIETHYL PHTHALATE 127 

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. 
DIETHYL PHTHALATE 128 

9. GLOSSARY 

Immediately Dangerous to Life or Health (IDLH) -- The maximum environmental concentration of 

a contaminant from which one could escape within 30 min without any escape-impairing symptoms or 

irreversible health effects. 

Intermediate Exposure -- Exposure to a chemical for a duration of 15-364 days, as specified in the 

Toxicological Profiles. 

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. 
DIETHYL PHTHALATE 129 

9. GLOSSARY 

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. 

q1* -- The upper-bound estimate of the low-dose slope of the dose-response curve as determined by 

the multistage procedure. The q1* 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 min continually. No more than four excursions are allowed per day, and there 

must be at least-60 min between exposure periods. The daily TLV-TWA may not be exceeded. 

Target Organ Toxicity -- This term covers a broad range of adverse effects on target organs or 

physiological systems (e.g., renal, cardiovascular) extending from those arising through a single limited 

exposure to those assumed over a lifetime of exposure to a chemical. 

Teratogen -- A chemical that causes structural defects that affect the development of an organism. 
DIETHYL PHTHALATE 130 

9. GLOSSARY 

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 

uncertainty in using LOAEL data rather than NOAEL data. Usually each of these factors is set equal 

to 10. 
A-l 

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 

upper-bound individual lifetime cancer risk of 1 in 10,000 to 1 in 10,000,000. Use the LSE tables and 

figures for a quick review of the health effects and to locate data for a specific exposure scenario. The 

LSE tables and figures should always be used in conjunction with the text. All entries in these tables 

and figures represent studies that provide reliable, quantitative estimates of No-Observed-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-l and Figure 2-l are shown. The numbers in the left column of the legends 

correspond to the numbers in the example table and figure. 

LEGEND 

See LSE Table 2-1 

(1) Route of Exposure One of the first considerations when reviewing the toxicity of a substance 

using these tables and figures should be the relevant and appropriate route of exposure. When 

sufficient data exists, three LSE tables and two LSE figures are presented in the document. The 

three LSE tables present data on the three principal routes of exposure, i.e., inhalation, oral, and 

dermal (LSE Table 2-1, 2-2, and 2-3, respectively). LSE figures are limited to the inhalation 

(LSE Figure 2-l) and oral (LSE Figure 2-2) routes. Not all substances will have data on each 

route of exposure and will not therefore have all five of the tables and figures. 
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-l). 

(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 0.005 ppm (see footnote “b”). 

(9)	 LOAEL A Lowest-Observed-Adverse-Effect Level (LOAEL) is the lowest dose used in the 

study that caused a harmful health effect. LOAELs have been classified into “Less Serious” and 

“Serious” effects. These distinctions help readers identify the levels of exposure at which 

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. 
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 “b” indicates the NOAEL of 3 ppm in key number 18 was used to 

derive an MRL of 0.005 ppm. 

LEGEND 

See Figure 2-1 

LSE figures graphically illustrate the data presented in the corresponding LSE tables. Figures help the 

reader quickly compare health effects according to exposure concentrations for particular exposure 

periods. 

(13)	 Exposure Period The same exposure periods appear as in the LSE table. In this example, health 

effects observed within the intermediate and chronic exposure periods are illustrated. 

(14)	 Health Effect These are the categories of health effects for which reliable quantitative data 

exists. The same health effects appear in the LSE table. 

(15)	 Levels of Exposure concentrations or doses for each health effect in the LSE tables are 

graphically displayed in the LSE figures. Exposure concentration or dose is measured on the log 

scale “y” axis. Inhalation exposure is reported in mg/m3 or ppm and oral exposure is reported in 

mg/kg/day . 

(16)	 NOAEL In this example, 1% NOAEL is the critical endpoint for which an intermediate 

inhalation exposure MRL is based. As you can see from the LSE figure key, the open-circle 

symbol indicates to a NOAEL for the test species-rat. The key number 18 corresponds to the 

entry in the LSE table. The dashed descending arrow indicates the extrapolation from the 

exposure level of 3 ppm (see entry 18 in the Table) to the MRL of 0.005 ppm (see footnote “b” 

in the LSE table). 

(17)	 CEL Key number 3% 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 (ql*). 

(19)	 Key to LSE Figure The Key explains the abbreviations and symbols used in the figure. 


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. Minimal 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 de 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). 
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.