TOXICOLOGICAL PROFILE FOR 

DI-n-OCTYLPHTHALATE 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Public Health Service 

Agency for Toxic Substances and Disease Registry 

September 1997
DI-n-OCTYLPHTHALATE 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.
DI-n-OCTYLPHTHALATE iii 

UPDATE STATEMENT 

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

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

Agency for Toxic Substances and Disease Registry 

Division of Toxicology/Toxicology Information Branch 

1600 Clifton Road NE, E-29 

Atlanta, Georgia 30333



DI-n-OCTYLPHTHALATE vii 

CONTRIBUTORS 

CHEMICAL MANAGER(S)/AUTHOR(S): 

Jessilynn B. Taylor, M.S. 

ATSDR, Division of Toxicology, Atlanta, GA 

Patricia M. Bittner, M.S. 

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 end points. 

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

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

profile, and makes recommendations for derivation of MRLs.











DI-n-OCTYLPHTHALATE 1 

1. PUBLIC HEALTH STATEMENT 

This Statement was prepared to give you information about di-n-octylphthalate and to 

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

Protection Agency (EPA) has identified 1,416 hazardous waste sites as the most serious in the 

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

long-term federal cleanup activities. Di-n-octylphthalate has been found in at least 300 of 

the sites on the NPL. However, the number of NPL sites evaluated for di-n-octylphthalate is 

not known. As EPA evaluates more sites, the number of sites at which di-n-octylphthalate is 

found may increase. This information is important because exposure to di-n-octylphthalate 

may cause harmful health effects and because these sites are potential or actual sources of 

human exposure to di-n-octylphthalate. 

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

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

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

You may be exposed by breathing, eating, or drinking substances containing the substance or 

by skin contact with it. 

If you are exposed to a substance such as di-n-octylphthalate, many 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, 

gender, nutritional status, family traits, life-style, and state of health. 

1 .1 WHAT IS DI-n-OCTYLPHTHALATE? 

Di-n-octylphthalate, also known as dioctyl phthalate, is a colorless, odorless, oily liquid. It 

does not evaporate easily. There is no evidence that di-n-octylphthalate occurs naturally in
DI-n-OCTYLPHTHALATE 2 

1. PUBLIC HEALTH STATEMENT 

the environment. Di-n-octylphthalate is manufactured for many uses. It is commonly used as 

a plasticizer (a substance added to plastics to keep them soft or more flexible). These plastics 

are found in products such as carpetback coating, packaging films, medical tubing and blood 

storage bags, floor tile, wire, cables, and adhesives. Di-n-octylphthalate is also used in 

cosmetics and pesticides. For more information on the chemical and physical properties of 

di-n-octylphthalate, see Chapter 3. For more information on its production and use, see 

Chapter 4. 

1.2 WHAT HAPPENS TO DI-n-OCTYLPHTHALATE WHEN IT ENTERS THE 

 ENVIRONMENT? 

Di-n-octylphthalate may enter the environment in industrial waste waters, air emissions, and 

solid wastes from manufacturing and processing operations, from evaporation of the 

compound from plastics, from the burning of plastic products, and by leaking from plastics in 

landfills into soil or water, including groundwater. Di-n-octylphthalate is expected to stick 

tightly to soil, sediment, and dust particles once it is released to the environment. If released 

to the atmosphere, the compound may be deposited on the ground or to surface water in rain 

or dust particles. Small amounts of the compound can build up in animals that live in water, 

such as fish and oysters. The compound breaks down into other products mainly by the 

action of microorganisms. Additional ways di-n-octylphthalate is transformed into other 

substances include reaction with sunlight and other chemicals present in the atmosphere, 

reaction with water, and breakdown of the compound in surface waters by sunlight. For 

further information on what happens to di-n-octylphthalate when it enters the environment, 

see Chapters 4 and 5. 

1.3 HOW MIGHT I BE EXPOSED TO DI-n-OCTYLPHTHALATE? 

You may be exposed to di-n-octylphthalate by eating foods contaminated with any of the 

compound that has leaked from plastic containers, by eating certain foods, such as fish, that 

have built up high levels of the compound, and by drinking contaminated water. You may 

also be exposed to di-n-octylphthalate during medical treatments such as blood transfusions
DI-n-OCTYLPHTHALATE 3 

1. PUBLIC HEALTH STATEMENT 

and dialysis that use equipment made of plastics containing di-n-octylphthalate. In addition, 

if you live near a hazardous waste site or an industrial manufacturing or processing facility, 

you may be exposed through contact with air, water, or soil that may have been contaminated 

around these sites. Little information is available about the concentrations of di-noctylphthalate 

in air, water, or soil. The compound has been measured at 0.06-0.94 parts di-n-octylphthalate per trillion 

parts of air (ppt), in rain at 2.6-20 ppt, in river water at l-310 ppt, and in sediment at less than 5-25,000 ppt. 

Workers in the chemicals and plastics industries may also be exposed to di-n-octylphthalate. 

The National Occupational Exposure Survey estimated that 10,393 individuals were exposed 

to the compound in the workplace in 1980. For further information on how you can be 

exposed to di-n-octylphthalate, see Chapter 5. 

1.4 HOW CAN DI-n-OCTYLPHTHALATE ENTER AND LEAVE MY BODY? 

Di-n-octylphthalate can enter your body when you drink water or eat food containing it. We 

do not know if di-n-octylphthalate enters your body when you breathe air containing it or 

when it comes in contact with 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. We do not know how much you will absorb if you eat or drink it. 

Di-n-octylphthalate can also enter your body during medical treatment through the use of 

plastic tubing or storage bags contaminated with di-n-octylphthalate. Once it enters your 

body, it breaks down into other chemicals and the health effects of some of these chemicals 

are not well understood. Di-n-octylphthalate and its breakdown products will leave your body 

mostly in your urine, but we do not know how quickly that happens. We do not know if the 

compound or its breakdown products will remain in the tissues. For more information on 

how di-n-octylphthalate can enter and leave your body, see Chapter 2.
DI-n-OCTYLPHTHALATE 4 

1. PUBLIC HEALTH STATEMENT 

1.5 HOW CAN DI-n-OCTYLPHTHALATE AFFECT MY HEALTH? 

No information is available regarding the possible human health effects caused by di-noctylphthalate if you breathe, eat, drink, or have skin contact with it. Furthermore, there is 

no information on the effects of breathing di-n-octylphthalate in laboratory animals. Di-noctylphthalate has caused death in some rats and mice given very high doses by mouth. 

Mildly harmful effects have been seen in the livers of some rats and mice given very high 

doses of di-n-octylphthalate by mouth for short or intermediate durations of time. Brief oral 

exposures to lower doses of di-n-octylphthalate generally caused no harmful effects. 

We have no information on the health effects of di-n-octylphthalate when applied to the skin 

of humans for long periods of time. Di-n-octylphthalate 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. For more information on the health effects of di-n-octylphthalate, please 

refer to Chapter 2. 

We do not know if di-n-octylphthalate causes cancer in humans or animals. Unlike other 

phthalates such as di(2-ethylhexyl)phthalate, di-n-octylphthalate does not appear to affect the 

ability of male animals to father offspring [see ATSDR toxicological profile for di(2- 

ethylhexyl)phthalate for more information on this chemical]. Some birth defects occurred in 

newborn rats whose mothers received high doses (approximately 5 grams per kilogram of 

body weight [5 g/kg]) of di-n-octylphthalate by injection during pregnancy. However, 

humans are not exposed to di-n-octylphthalate this way, and no harmful effects on developing 

fetuses were seen when mice were given this chemical by mouth. 

Di-n-octylphthalate has not been classified for carcinogenic effects by the Department of 

Health and Human Services, the International Agency for Research on Cancer, or the EPA.
DI-n-OCTYLPHTHALATE 5 

1. PUBLIC HEALTH STATEMENT 

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

 EXPOSED TO DI-n-OCTYLPHTHALATE? 

Di-n-octylphthalate and its principal breakdown products can be measured in urine, blood, ant 

tissues. However, the information available on these tests is so limited that it is not possible 

to know if they are specific for di-n-octylphthalate, if they can be used to determine how 

much you were exposed to, if they can predict whether harmful health effects will occur, or 

how long the test is useful after exposure occurs. These tests are not available in doctors’ 

offices. See Chapters 2 and 6 for more information 

1.7 WHAT RECOMMENDATIONS HAS THE FEDERAL GOVERNMENT MADE 

 TO PROTECT HUMAN HEALTH? 

The government has developed guidelines for di-n-octylphthalate. These are designed to 

protect the public from the possible harmful health effects of the chemical. However, EPA 

has recently determined that there is not enough evidence to say that di-n-octylphthalate 

definitely causes harmful effects in humans or to the environment. See Chapter 7 for more 

information on regulations and guidelines for di-n-octylphthalate. 

1.8 WHERE CAN I GET MORE INFORMATION? 

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

environmental quality department or: 

Agency for Toxic Substances and Disease Registry 

Division of Toxicology 

1600 Clifton Road NE, E-29 

Atlanta, Georgia 30333 

(404) 639-6000
DI-n-OCTYLPHTHALATE 6 

1. PUBLIC HEALTH STATEMENT 

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

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

treatment of illness resulting from exposure to hazardous substances.
DI-n-OCTYLPHTHALATE 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 on the toxicology of di-noctylphthalate. It contains descriptions and evaluations of toxicological studies and epidemiological 

investigations and provides conclusions, where possible, on the relevance of toxicity and toxicokinetic 

data to public health. 

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

2.2 DISCUSSION OF HEALTH EFFECTS BY ROUTE OF EXPOSURE 

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

hazardous waste sites, the information in this section is organized first by route of exposure - 

inhalation, oral, and dermal; and then by health effect - death, systemic, immunological, neurological, 

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

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

or more). 

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

figures. The points in the figures showing no-observed-adverse-effect levels (NOAELs) or 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. “Serious” effects are 

those that evoke failure in a biological system and can lead to morbidity or mortality (e.g., acute 

respiratory distress or death). “Less serious” effects are those that are not expected to cause significant 

dysfunction or death, or those whose significance to the organism is not entirely clear. ATSDR 

acknowledges that a considerable amount of judgment may be required in establishing whether an end 

point should be classified as a NOAEL, “less serious” LOAEL, or “serious” LOAEL, and that in some 

cases, there will be insufficient data to decide whether the effect is indicative of significant 

dysfunction. However, the Agency has established guidelines and policies that are used to classify
DI-n-OCTYLPHTHALATE 8 

2. HEALTH EFFECTS 

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

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

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

identify levels of exposure at which major health effects start to appear. LOAELs or NOAELs should 

also help in determining whether or not the effects vary with dose and/or duration, and place into 

perspective the possible significance of these effects to human health. 

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

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

with appropriate actions to take at hazardous waste sites may want information on levels of exposure 

associated with more subtle effects in humans or animals or exposure levels below which no adverse 

effects have been observed. Estimates of levels posing minimal risk to humans (Minimal Risk Levels 

or MRLs) may be of interest to health professionals and citizens alike. 

Estimates of exposure levels posing minimal risk to humans (Minimal Risk Levels or MRLs) have 

been made for di-n-octylphthalate. An MRL is defined as an estimate of daily human exposure to a 

substance that is likely to be without an appreciable risk of adverse effects (noncarcinogenic) over a 

specified duration of exposure. MRLs are derived when reliable and sufficient data exist to identify 

the target organ(s) of effect or the most sensitive health effect(s) for a specific duration within a given 

route of exposure. MRLs are based on noncancerous health effects only and do not consider 

carcinogenic effects. MRLs can be derived for acute, intermediate, and chronic duration exposures for 

inhalation and oral routes. Appropriate methodology does not exist to develop MRLs for dermal 

exposure. 

Although methods have been established to derive these levels (Barnes and Dourson 1988; EPA 

1990a), 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.
DI-n-OCTYLPHTHALATE 9 

2. HEALTH EFFECTS 

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

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

The toxicity information presented in this chapter focuses on studies that have identified with 

reasonable certainty that their test material is di-n-octylphthalate or its monoester metabolite, mono-noctylphthalate. Unfortunately, use of the nonspecific term “di-octylphthalate” has contributed to 

significant confusion and misinformation in the technical and governmental literature with respect to 

di-n-octylphthalate and its much more common isomer, di(2-ethylhexyl)phthalate. Although frequently 

interpreted as referring to di-n-octylphthalate, it is apparent that in almost all cases “di-octylphthalate” 

and “DOP” have in fact been used as synonyms for di(2-ethylhexyl)phthalate. Throughout this chapter 

whenever possible, an assessment of the level of certainty that the test compound was di-noctylphthalate 

will be made. 

2.2.1 inhalation Exposure 

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

exposure to di-n-octylphthalate: 

2.2.1.1 Death 

2.2.1.2 Systemic Effects 

2.2.1.3 Immunological and Lymphoreticular 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 2.5.
DI-n-OCTYLPHTHALATE 10 

2. HEALTH EFFECTS 

2.2.1.8 Cancer 

No studies were located regarding cancer in humans or animals after inhalation exposure to di-noctylphthalate. 

2.2.2 Oral Exposure 

2.2.2.1 Death 

No studies were located regarding death in humans after oral exposure to di-n-octylphthalate. 

In animals, the reported oral LD50 values are 53,700 mg/kg body weight for male albino rats (Dogra 

et al. 1987), 13,000 mg/kg for Swiss albino mice (Dogra et al. 1989), and >12,800 mg/kg for mice 

(Eastman Kodak Company 1978). Dosing was by gavage in these studies. No additional studies were 

located regarding death in animals after oral exposure to di-n-octylphthalate. 

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

in Table 2-l and plotted in Figure 2- 1. 

2.2.2.2 Systemic Effects 

No studies were located regarding respiratory, cardiovascular, musculoskeletal, dermal, or ocular 

effects in humans or animals after oral exposure to di-n-octylphthalate. The systemic effects observed 

after oral exposure are discussed below. The highest NOAEL values and all LOAEL values from each 

reliable study for observed systemic effects in each species and duration category are recorded in 

Table 2-l and plotted in Figure 2-1. 

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

exposure to di-n-octylphthalate. 

One study reported that feeding di-n-octylphthalate to groups of four male Wistar albino rats at 

average doses of 2,266 mg/kg/day for 3 days, 2,078 mg/kg/day for 10 days, or 1,096 mg/kg/day for 

21 days did not result in any gross pathological changes in the pancreas (Mann et al. 1985). No










DI-n-OCTYLPHTHALATE 21 

2. HEALTH EFFECTS 

analytical data were reported, but it is reasonably certain that the test compound was di-n-octylphthalate 

(purity was reported to be 99.5%). 

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

exposure to di-n-octylphthalate. 

One study in Sprague-Dawley rats (10/sex/group) reported that feeding di-n-octylphthalate at 

concentrations up to 5,000 ppm (350.1 or 402.9 mg/kg/day in males or females, respectively) for 

13 weeks did not affect hematological parameters (Poon et al. 1995). 

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

Several studies were located that reported a variety of hepatic effects in rats and mice usually after 

large oral doses were administered for acute or intermediate durations. These include effects of di-noctylphthalate on liver appearance, structure, and function. 

Gross Appearance and Organ Mass. Upon dietary exposure of groups of four male Wistar albino rats 

to 1,906-2,266 mg/kg/day of di-n-octylphthalate for 3-21 days, livers were reported to be pale and 

greasy in appearance (Mann et al. 1985). When compared with control values, no change in liver 

weight was observed after 3 days of treatment, although small but significant (p < 0.01) increases in 

relative liver weight (liver weight as a percentage of body weight) were noted after 10 days (4.7% 

versus 4.0%, or a 19% change from control) and 21 days (4.1% versus 3.2%, or a 28% change from 

control) of treatment. Similarly, absolute (15%) or relative (16%) liver weights were increased 

significantly in 10 male Wistar rats after 7 days of dietary exposure to 1,000 mg/kg/day (Oishi and 

Hiraga 1980). Relative liver weight was significantly increased in 6 male Sprague-Dawley rats after 

14 days of exposure by gavage to 1,000 or 2,000 mg/kg/day (Lake et al. 1984, 1986). No changes in 

absolute or relative liver weights were noted after Sprague-Dawley rats (10/sex/group) were fed 

concentrations of up to 5,000 ppm (350.1 or 402.9 mg/kg/day in males and females, respectively) in 

the diet for 13 weeks (Poon et al. 1995). 

Male rats, initiated with a single intraperitoneal dose of the carcinogen diethylnitrosamine and then 

partially hepatectomized, did not experience any liver weight gain after 10 weeks of dietary exposure
DI-n-OCTYLPHTHALATE 22

2. HEALTH EFFECTS

to 500 mg/kg/day of di-n-octylphthalate (DeAngelo et al. 1986). When exposure was extended to

26 weeks, small increases in absolute liver weight that were not significant (p < 0.05) were observed

at di-n-octylphthalate doses of 250 mg/kg/day (2% increase) and 500 mg/kg/day (8% increase).

However, when combined with diminished body weight gains, relative liver weight gains were

increased by 5-16% when compared with control values (Carter et al. 1992). These results should be

considered independently of the other studies discussed because the animals were surgically altered

and chemically treated with diethylnitrosamine.

Dietary exposure for 85-105 days (including lactation during exposure of the dams) to

8,640 mg/kg/day of di-n-octylphthalate also induced significant (p < 0.05) absolute liver weight gains

in male and female CD-l mice (Heindel et al. 1989; Morrissey et al. 1989; NTP 1985). All three of

these papers reported the same study; the dose specified here is from the Morrissey et al. (1989)

report. A l-week dietary exposure to 1,000 mg/kg/day of mono-n-octylphthalate was also reported to

induce liver enlargement in seven male Wistar rats (Oishi and Hiraga 1982). Whether those modest

liver weight increases resulted primarily from hyperplasia or from hypertrophy is not clear. However,

the absence of increased hepatic mitotic activity in two of four rats after di-n-octylphthalate exposure

in the Mann et al. (1985) study noted above suggests that significant hyperplasia may not be a factor.

Morphology, Histopathology, and Biochemistry. Aside from the pale, greasy appearance noted above,

livers from male Wistar rats exposed for 3 days to 2,266 mg/kg/day of di-n-octylphthalate in the diet

displayed a loss of centrilobular glycogen (Mann et al. 1985). Proliferation and dilation of the smooth

endoplasmic reticulum accompanied by some loss of rough endoplasmic reticulum were noted, as were

shortened microvilli in some bile canaliculi. No significant changes were noted in parameters

associated with hepatic peroxisomal activity (cyanide-insensitive palmitoyl CoA oxidase, α-glycerophosphate dehydrogenase, and total or peroxisomal catalase activities), plasma membrane integrity

(plasma membrane 5’-nucleotidase activity), mitochondrial respiration (succinate dehydrogenase

activity), endoplasmic reticular function (glucose-6-phosphatase activity and level of cytochrome

P-450), or in the level of nonenzymic reductants. When exposure time was increased to 10 or 21 days

(average doses of 2,078 or 1,906 mg/kg/day di-n-octylphthalate, respectively), the centrilobular

reduction in glycogen became more severe and was associated with fat accumulation and some

necrosis. However, the almost total loss of liver glycogen that was observed when using similar doses

of di(2-ethylhexyl)phthalate did not occur. Lipid droplets were observed in hepatocytes, along with a

possible small increase in the number of peroxisomes; the endoplasmic reticulum morphology
DI-n-OCTYLPHTHALATE 23

2. HEALTH EFFECTS

alterations remained apparent. Small but significant (p < 0.01 or 0.05) increases were found in

hepatic cyanide-insensitive palmitoyl CoA oxidase and peroxisomal catalase activities but not in

α-glycerophosphate dehydrogenase or total catalase activities. Significant reductions were noted in

5’-nucleotidase, succinate dehydrogenase, and glucose-6-phosphatase activities compared to the

controls. In contrast to di-n-octylphthalate treatment, similar doses of di(2-ethylhexyl)phthalate

resulted in a dark, enlarged liver, and an initial burst of mitosis was noted at day 3 in two out of four

rats. A lesser degree of early centrilobular glycogen loss was noted with di(ethylhexyl)phthalate, but

almost total liver glycogen loss occurred after 21 days along with periportal rather than centrilobular

fat accumulation, no centrilobular necrosis, pronounced peroxisome proliferation, greater smooth

endoplasmic reticulum proliferation, mitochondrial matrix changes, and larger reductions in

5’-nucleotidase, glucose-6-phosphatase, and nonenzymic reductant activities.

Sprague-Dawley rats (10/sex/group) fed 0, 5, 50, 500, or 5,000 ppm of di-n-octylphthalate in the diet,

corresponding to intakes of 0, 0.4, 3.5, 36.8, and 350.1 mg/kg/day (males) or 0, 0.4, 4.1, 40.8, and

402.9 mg/kg/day (females), for 13 weeks showed significant increases in hepatic ethoxyresorufin-Odemethylase activities at the highest dose (Poon et al. 1995). There were histopathologic changes in

hepatic architecture noted at 5,000 ppm, however, which included a moderate degree of accentuation

of zonation in all animals of both sexes and mild-to-moderate perivenous cytoplasmic vacuolation in

9/10 males and 5/10 females (Poon et al. 1995). These effects were not observed at 500 ppm, which

represents the NOAEL. There was no visual increase in peroxisomes noted at any dose level and no

changes in activities of either amino-N-demethylase or aniline hydrolase.

Rats exposed to dietary concentrations of mono-n-octylphthalate equivalent to 1,000 mg/kg/day

exhibited a variety of significant alterations in serum lipid composition, reflecting a possible effect on

the hepatic metabolism of lipids (Oishi and Hiraga 1982). With respect to control values, serum

concentrations of phospholipids and nonesterified fatty acids were increased, while those of

triglycerides and total cholesterol were decreased. Levels of free cholesterol, lipoperoxides, and

1ecithin:cholesterol acyltransferase activity were not significantly affected. Mono-n-octylphthalate

exposure increased palmitic acid content while decreasing stearic acid content in serum phospholipid;

increased oleic acid content in serum phospholipid, cholesteryl ester, and triglyceride; decreased

linoleic acid content in serum triglyceride; and decreased arachidonic acid content in serum

phospholipid. Several other monophthalates were also evaluated, with mono-2-ethylhexylphthalate

being generally somewhat more potent than mono-n-octylphthalate. The compositional effects of
DI-n-OCTYLPHTHALATE 24 

2. HEALTH EFFECTS 

mono-2-ethylhexylphthalate on serum cholesteryl ester were broader and more pronounced than those 

of mono-n-octylphthalate, while the reverse was true for serum triglyceride (mono-2- 

ethylhexylphthalate was without significant effect). Such effects could result in part from altered 

gastrointestinal digestion and absorption of dietary fat, but as suggested by the previously noted 

accumulation of fat in the liver (Mann et al. 1985), they may reflect altered hepatic metabolism of 

fatty acids and cholesterol. The toxicological significance of these alterations in lipid metabolism is 

not known. The study authors noted that the general trend of these serum lipid changes and the 

attendant increases in liver size are significantly similar to the effects observed after exposure to di(2- 

ethylhexyl)phthalate (see also ATSDR 1992), thus implicating the monoesters or subsequent 

metabolites, rather than the diesters, as the active compounds inducing these effects. 

Treating male Sprague-Dawley rats with di-n-octylphthalate (2,000 mg/kg/day) or mono-n-octylphthalate 

(750 and 1,000 mg/kg/day) by gavage for 14 days (5 rats/dose) did not induce hepatic 

peroxisome proliferation (Lake et al. 1984). Similar treatment with 1,000 mg/kg/day di-n-octylphthalate or 

715 mg/kg/day mono-n-octylphthalate did not significantly increase (cyanide-insensitive palmitoyl-CoA 

oxidase and heat-liable enoyl-CoA hydratase) or reduce (O-amino acid 

oxidase) hepatic enzyme activities associated with peroxisome proliferation (Lake et al. 1984, 1986). 

Both di-n-octylphthalate and mono-n-octylphthalate significantly reduced (p < 0.05) hepatic 

microsomal-7-ethoxyresorutin O-deethylase activity, and di-n-octylphthalate reduced 7-ethoxycoumarin 

O-deethylase activity, but neither di-n-octylphthalate nor mono-n-octylphthalate significantly affected 

other mixed function oxidase activities (ethylmorphine n-demethylase, lauric acid 11-and 

12-hydroxylases), microsomal cytochrome P-450 content, microsomal hemoprotein spectral properties, 

or sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles of hepatic whole homogenates 

and microsomes. Again, these results were substantially different from those obtained with doses of 

1,000 mg/kg di(2-ethylhexyl)phthalate and 500 mg/kg of the hypolipidemic drug clofibrate. 

Two additional rat studies designed to investigate the reproductive effects of di-n-octylphthalate 

exposure provide another observation on the hepatic effects of di-n-octylphthalate. Contrary to what is 

observed with di(2-ethylhexyl)phthalate, the concentration in liver of the essential element zinc was 

found not to be significantly reduced after 4 days of gavage exposure to 2,800 mg/kg/day of di-noctylphthalate (Foster et al. 1980), or 7 days of dietary exposure to 1,000 mg/kg/day of di-n-octylphthalate 

(Oishi and Hiraga 1980).
DI-n-OCTYLPHTHALATE 25 

2. HEALTH EFFECTS 

The only oral study located that evaluated the presence of hepatic effects in a species other than rats 

was a reproductive-developmental toxicity study conducted according to the NTP Continuous Breeding 

Protocol (Heindel et al. 1989; Morrissey et al. 1989; NTP 1985). F1 generation CD-l mice (offspring 

from the fifth litter of a treated F0 generation) were exposed via lactation to di-n-octylphthalate (from 

dams exposed to approximately 7,460 mg/kg/day) and then via feed after weaning until they were 

85-105 days old. The average di-n-octylphthalate dose over this period was calculated by the study 

authors to be 8,640 mg/kg/day. As might be expected from prior rat data, statistically significant 

increases in absolute liver weight (24%) were noted. The study authors reported that no gross 

morphological or histopathological alterations were observed in the treated livers. This is despite 

substantially higher doses and longer treatment times than were used in the rat studies and despite a 

fourfold lower acute oral LD50 reported for mice than for rats (Dogra et al. 1987, 1989). As has been 

noted for di(2-ethylhexyl)phthalate (ATSDR 1992), the degree and nature of hepatotoxicity resulting 

from exposure to di-n-octylphthalate may vary considerably with species and also with dosage 

procedures. Dogra et al. (1987, 1989) employed oral gavage with rats and mice, whereas the NTP 

study employed dietary feeding with mice. 

In summary, the liver appears to be a primary target organ for the toxic effects of acute- and 

intermediate-duration high-dose exposure to di-n-octylphthalate (and mono-n-octylphthalate), at least in 

the rat and mouse. Unlike its branched-chain isomer di(2-ethylhexyl)phthalate, di-n-octylphthalate 

presents a liver toxicity profile only weakly suggestive of the hypolipidemic peroxisome proliferators 

(e.g., clofibrate). Instead, the liver changes associated with exposure to di-n-octylphthalate are 

characterized by marked centrilobular accumulation of fat and loss of glycogen, accompanied by 

reduced glucose-6-phosphatase, cytoplasmic vacuolation, accentuation of zonation, and some 

centrilobular necrosis. However, although these effects have been noted in two studies (Mann et al. 

1985; Poon et al. 1995), they were not seen in a multigeneration study in mice by NTP (Heindel et al. 

1989; Morrissey et al. 1989; NTP 1985) or in other studies in rats (Lake et al. 1984, 1986; Oishi and 

Hiraga 1980). It should be mentioned here that di-n-octylphthalate has been shown to induce 

additional liver effects associated with preneoplastic alteration; these are discussed below under 

“Cancer.”
DI-n-OCTYLPHTHALATE 26

2. HEALTH EFFECTS

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

Few animal studies were located that report any observations on the renal toxicity of di-n-octylphthalate.

In a study examining the effects of di-n-octylphthalate on testicular function, rats that

had received 2,800 mg/kg/day by gavage for 4 days were observed to have a small (9%) but not

statistically significant reduction in kidney zinc concentration when compared with controls (Foster

et al. 1980). Total urinary excretion of zinc was reduced to 85% of controls, but again this was not

significant. When expressed as a percentage of zinc excretion on day 0 (i.e., prior to di-noctylphthalate

administration), the 4-day urinary excretion profile of zinc in the di-n-octylphthalate-treated

rats was virtually identical to that of controls. No effect on kidney weight was observed. In

contrast, these parameters were generally elevated after treatment with n-alkylphthalates that induced

testicular pathology (di-n-butylphthalate, di-n-pentylphthalate, and di-n-hexylphthalate; see

“Reproductive Effects,” below). These findings are supported by another study in rats in which dietary

exposure of male Wistar rats for 1 week to 1,000 mg/kg/day of di-n-octylphthalate did not affect the

concentration of zinc in the kidney (phthalic acid slightly increased it) nor significantly (p < 0.05)

reduce kidney weight as did di(2-ethylhexyl)phthalate (Oishi and Hiraga 1980). No gross pathological

changes were observed in the kidneys of male Wistar rats following 3-, 10-, or 21-day exposure to 2%

di-n-octylphthalate in the diet (2,266, 2,078, or 1,906 mg/kg/day, respectively) (Mann et al. 1985). No

effects on absolute or relative kidney weight were noted when Sprague-Dawley rats of both sexes were

fed di-n-octylphthalate for 13 weeks at concentrations up to 5,000 ppm (350.1 or 402.9 mg/kg/day in

males and females, respectively) (Poon et al. 1995).

One reproductive-developmental toxicity study in CD-l mice also examined the renal effects of di-noctylphthalate exposure (Heindel et al. 1989; Morrissey et al. 1989; NTP 1985). Following the NTP

Continuous Breeding Protocol, F1 mice taken from the last litter of treated F1 parental mice

(7,460 mg/kg/day for 105 days, including the mating period) were exposed for 85-105 days to an

average calculated di-n-octylphthalate dose of 8,640 mg/kg/day (first via lactation, then feed).

Although no gross morphological or histopathological changes in the kidney were noted, absolute

kidney weight was significantly (p < 0.05) elevated in female (1l%), but not male, mice.
DI-n-OCTYLPHTHALATE 2 7 

2. HEALTH EFFECTS 

Despite the absence of data on organ function, these limited results suggest that acute or intermediate 

oral exposure to even very high doses of di-n-octylphthalate is not likely to result in substantial renal 

toxicity. 

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

exposure to di-n-octylphthalate. 

There is some evidence in animals that suggests that oral administration of di-n-octylphthalate may 

affect the thyroid gland. Serum from four male Wistar rats that were fed di-n-octylphthalate at a 

concentration of 2% in the diet (approximately 2,000 mg/kg/day) in a previous study (Mann et al. 

1985) was reassayed (Hinton et al. 1986). After 3, 10, and 21 days of treatment, significant decreases 

in thyroxine (T4) levels were noted compared to the controls. T4 levels were 47%, 59%, and 76% of 

control values after 3, 10, and 21 days of treatment, respectively. No significant effects on 

triiodothyronine (T3) levels were noted compared to the controls (Hinton et al. 1986). In addition, 

marked ultrastructural changes were noted in the thyroids of these animals, including increases in the 

numbers and size of lysosomes, enlargement of the Golgi apparatus, and apparent damage to the 

mitochondria (Hinton et al. 1986). This study was limited, however, in that only one concentration 

was tested. 

Groups of 10 male and 10 female Sprague-Dawley rats that were administered di-n-octylphthalate in 

the diet for 13 weeks at concentrations of 0, 5, 50, 500 and 5,000 ppm, corresponding to intakes of 0, 

0.4, 3.5, 36.8, and 350.1 mg/kg/day (males) and 0, 0.4, 4.1, 40.8, and 402.9 mg/kg/day (females) 

showed reductions in the size of thyroid follicles and mild decreases in colloid density at 

5,000 ppm (Poon et al. 1995). Changes in these parameters was also noted at 500 ppm, but it is not 

whether this concentration represents a LOAEL, because statistical analysis of the data was not 

performed. 

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

exposure to di-n-octylphthalate. 

Data from various studies consistently indicate that acute or intermediate oral exposures to high doses 

(l,000-15,000 mg/kg/day) of di-n-octylphthalate do not adversely affect either body weight gain or 

food consumption in rats or mice (Carter et al. 1992; Heindel et al. 1989; Mann et al. 1985; Morrissey
DI-n-OCTYLPHTHALATE 28 

2. HEALTH EFFECTS 

et al. 1989; NTP 1985; Oishi and Hiraga 1980, 1982). In male Wistar rats receiving di-noctylphthalate 

at a concentration of 2% in the diet (approximately 2,000 mg/kg/day), food intake was 

significantly (p < 0.01) increased after 3 days when compared with controls (13.7 versus 

19.5 g/kg/rat), and body weight was significantly (p < 0.05) increased after 10 days relative to controls 

(204 versus 220 g/rat). By days 11-21, however, the values for both parameters returned to control 

levels (Mann et al. 1985). Male rats subjected to a single intraperitoneal dose of diethylnitrosamine, 

partial hepatectomy, and 26 weeks of dietary exposure to 250 or 500 mg/kg/day of di-n-octylphthalate 

apparently experienced small reductions (3-7%) in body weight gain (Carter et al. 1992). Male Wistar 

rats fed 1,000 mg/kg/day of the monoester mono-n-octylphthalate for 1 week were reported to have 

depressed body weight gains during the first 2 days and reduced body weights at the experiment’s end, 

but quantitative data were not provided (Oishi and Hiraga 1982). 

Other Systemic Effects. No studies were located regarding other systemic effects in humans after oral 

exposure to di-n-octylphthalate. 

After a 14-day exposure of CD-l mice to 1,800, 3,600, 7,500, or 15,000 mg/kg/day, a rough hair coat 

was noted in four to six out of eight animals of both sexes at 15,000 mg/kg/day (Heindel et al. 1989; 

NTP 1985). 

2.2.2.3 Immunological and Lymphoreticular Effects 

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

exposure to di-n-octylphthalate. 

Limited data suggest that di-n-octylphthalate can exert immunotoxic effects in rats and mice after acute 

oral exposure to relatively high doses. Male rats exposed by gavage once per day for 5 days to 0, 

2,685, 5,370, or 10,740 mg/kg/day of di-n-octylphthalate (acute LD50 was 53,700 mg/kg) did not 

display any signs of overt toxicity, but did exhibit a depletion of cells in the periarteriolar lymphoid 

sheet of the spleen that the study authors noted as dose dependent, although doses at which these 

effects were observed were not identified (Dogra et al. 1987). Dose-dependent cellularity changes in 

the thymus resulted in a loss of distinction between the cortex and the medulla, and germinal center 

activity was diminished in regional and peripheral lymph nodes. In response to the intraperitoneal 

injection of sheep red blood cells (SRBC), the number of IgM-producing spleen cells was significantly
DI-n-OCTYLPHTHALATE 29

2. HEALTH EFFECTS

(p < 0.001) reduced to approximately 10% or 5% of the control value in rats exposed to the mid- and

high-doses, respectively. There was a concomitant, dose-dependent, 1,000-fold reduction in serum

anti-SRBC antibodies. Phagocytic and metabolic activities of peritoneal exudate cells were also

reduced by up to 30-40%. When challenged by subcutaneous inoculation of 1,000 larvae from the

parasite Nippostrangylus brasiliensis, 10-day worm counts were indicated to be significantly elevated

by mid- and high-dose treatments (19% and 30%, respectively) when compared with controls. Finally,

mortality was increased from 2- to 2.5-fold in rats treated with 10,740 mg/kg/day di-n-octylphthalate

(versus controls) when they were subsequently challenged with intravascular injections of 125 or

250 pg of lipopolysaccharide endotoxin from Escherichia coli.

The immune system of the mouse may also be susceptible to the effects of acute oral exposures to

di-n-octylphthalate (Dogra et al. 1989). Three-month-old Swiss albino mice were exposed to di-noctylphthalate by gavage for 5 days at 0, 650, or 2,600 mg/kg/day (acute LD50 was 13,000 mg/kg).

Mice were subsequently exposed by intraperitoneal injection to either encephalomyocarditis virus or

the malarial protozoan, Plasmodium berghei. Maximum mortality levels were reached 8-10 days after

viral infection and were 20% (0 mg/kg/day), 40% (650 mg/kg/day), and 70% (2,600 mg/kg/day).

Malarial lethality reached plateau levels 4-l 1 days postinfection of approximately 20% (0 mg/kg/day),

25% (650 mg/kg/day), and 70% (2,600 mg/kg/day), then increased to 55%, 70%, and 85%,

respectively, by postinfection day 19. Respective mean survival times were calculated to be 13.50,

12.15, and 6.25 days. During the first 14 days after protozoa1 infection, the percentage of mouse

erythrocytes infected with the parasite in the high-dose group was consistently and significantly

(p < 0.01 or 0.05) higher than in the control group. Significant increases were generally not observed

in the low-dose group.

Both of these studies did not contain positive controls, and both omitted experimental details and much

quantitative data. In addition, no proof of compound identity was provided and the dose levels might

be considered high enough to risk inducing overt or generalized systemic toxicity. However, the

authors indicated that no signs of gross or other organ toxicity were observed, and previously

discussed studies appear, in general, to indicate only adverse hepatic effects following acute oral

exposure to di-n-octylphthalate. In combination, these studies suggest that acute oral exposure to high

doses of di-n-octylphthalate, at least in the rat and the mouse, may result in compromised immune

responses to bacterial, viral, protozoan, or other parasitic infection.
DI-n-OCTYLPHTHALATE 30 

2. HEALTH EFFECTS 

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

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

2.2.2.4 Neurological Effects 

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

di-n-octylphthalate. 

Limited data from one study on CD-l mice indicate that acute and intermediate dietary exposures to 

di-n-octylphthalate at doses of up to 15,000 mg/kg/day produced virtually no effect on clinical signs of 

toxicity (Heindel et al. 1989; Morrissey et al. 1989; NTP 1985). No clinical signs of neurotoxicity 

were noted after a 14-day exposure to 1,800, 3,600, 7,500, or 15,000 mg/kg/day; rough hair coats were 

noted at the highest dose. No clinical signs of neurotoxicity were observed in the mice following 

exposure to 1,820, 3,520, or 7,460 mg/kg/day for 105 days, nor in the offspring of the high-dose 

group that were exposed via lactation followed by feed for 85-105 days to an average di-n-octylphthalate 

dose of 8,640 mg/kg/day. 

2.2.2.5 Reproductive Effects 

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

di-n-octylphthalate. 

The results of several acute- or intermediate-duration rodent studies indicate that the potential of 

di-n-octylphthalate exposure to cause adverse reproductive effects is very low. When male rats were 

exposed by gavage to 2,800 mg/kg/day of di-n-octylphthalate for either 4 or 10 days, no testicular 

atrophy (weight loss or histological lesions), testicular zinc loss, or weight loss of the prostate or 

seminal vesicles were observed (Foster et al. 1980; Gray and Butterworth 1980). Such effects were 

induced by di-n-butylphthalate, di-n-pentylphthalate, di-n-hexylphthalate, and di(2-ethylhexyl)phthalate, 

but not by the methyl, ethyl, n-propyl, or n-heptylphthalate diesters. No adverse effects on testis 

weight or histopathology were found in male rats exposed to up to 5,000 ppm (402.9 mg/kg/day) of 

di-n-octylphthalate in the diet for 13 weeks (Poon et al. 1995). Similarly, no effect on testis weight, 

gross morphology, or histopathology was found in male rats receiving dietary exposure to 

approximately 2,000 mg/kg/day for 10 or 21 days (Mann et al. 1985). In another study in which male
DI-n-OCTYLPHTHALATE 31 

2. HEALTH EFFECTS 

rats were fed a diet containing 1,000 mg/kg/day of di-n-octylphthalate for 1 week, the absence of 

effect on absolute and relative testis weight was confirmed, and no effect was found on testicular 

concentrations of testosterone or dihydrotestosterone; however, a significant (15%, p < 0.05) reduction 

in testicular zinc concentration was observed (Oishi and Hiraga 1980). One or more of these 

parameters was also altered by di-o-butylphthalate, diisobutylphthalate (DiBP), dimethyl phthalate 

(DMP), diethyl phthalate (DEP), di(2-ethylhexyl)phthalate, and phthalic acid (PA). These data are 

insufficient to clarify the precise relationship among testicular atrophy, high testosterone, and low zinc, 

but the study authors speculated that testicular atrophy may depend on phthalate induction of elevated 

levels of testosterone in the testis, accompanied by reduced zinc levels in both the testis and the liver. 

Some small, but statistically significant (p < 0.05), changes in testicular mitochondrial respiratory 

functions were observed in 35-day-old male rats 6 hours after they had received a single oral dose of 

2,000 mg/kg di-n-octylphthalate by gavage (Oishi 1990). Oxygen consumption of mitochondrial 

preparations from the testis during state 3 respiration (succinate respiration in the presence of 

adenosine diphosphate [ADP]; phosphorylation) was reduced by 20% when compared with untreated 

control values, and the respiratory control ratio of state 3 to state 4 respiration (“resting” succinate 

respiration in the absence of ADP), which is a measure of respiration dependency on ADP, was also 

slightly reduced by 8%. Pyruvate and lactate concentrations were not changed, nor was 

phosphorylative activity (the state 3 ratio of ADP to oxygen consumption). These effects were 

generally less extensive than those induced by di(2-ethylhexyl)phthalate treatment. Routine 

histopathological examination showed no changes in the seminiferous tubule structure in 6-8 week old 

Wistar rats after single gavage doses of 2,000 mg/kg/day on each of 2 consecutive days (Jones et al. 

1993). However, electron microscopic examination revealed vesiculation of the smooth endoplasmic 

reticulum and increased stacking into parallel cistemae in some Leydig cells, but no mitochondrial 

swelling or degeneration. This study is limited, however, because the tabular listing of effects noted 

for di-n-octylphthalate in this paper shows no vesiculation of smooth endoplasmic reticulum (Jones et 

al. 1993). 

Finally, one mouse reproductive-developmental toxicity study performed according to the NTP 

Continuous Breeding Protocol was reported in three papers (Heindel et al. 1989; Morrissey et al. 1989; 

NTP 1985). Dietary exposure of F0 generation male and female CD-l mice for 105 days to doses of 

0, 1,820, 3,620, or 7,460 mg/kg/day of di-n-octylphthalate failed to cause any reduction in fertility 

index (percent fertile pairs) or number of litters/pair. In contrast, at least one of these parameters was
DI-n-OCTYLPHTHALATE 32 

2. HEALTH EFFECTS 

significantly reduced after exposure to di-n-propylphthalate or di-n-pentylphthalate (8,600 mg/kg/day 

of di-n-propylphthalate and 2,160 mg/kg/day of di-n-pentylphthalate completely inhibited fertility). 

Similarly, F1 generation mice exposed via lactation and then feed to an average di-n-octylphthalate 

dose of 8,640 mg/kg/day for 85-105 days exhibited a statistically significant (p < 0.05) reduction in 

seminal vesicle weight, but no significant changes were noted for testis, cauda epididymis, or prostate 

weights, or for sperm concentration, percent mobile sperm, or percent abnormal sperm. In female 

mice, estrous cycle length was not altered, and no reproductive tract organ weight or histopathological 

changes were observed. These findings confirm that di-n-octylphthalate has a low potential for 

inducing reproductive toxicity following oral exposure. 

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

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

2.2.2.6 Developmental Effects 

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

di-n-octylphthalate. 

In a preliminary developmental toxicity screening study, female CD-l mice received 9,780 mg/kg/day 

of di-n-octylphthalate by gavage once per day during gestation days 6-13 (Hardin et al. 1987; NIOSH 

1983). The following data were recorded: the number of pups born alive; total litter weight, pup 

survival, and litter weight gain immediately after birth and on postpartum day 3; maternal survival and 

weight gain from gestation day 6 to postpartum day 3; and the number of viable litters. The test 

material given was undiluted di-n-octylphthalate; the maximum feasible dose was considered to have 

been administered because an oral LD10 (the preferred dose) could not be established due to a lack of 

toxicity. The di-n-octylphthalate group varied significantly (p < 0.05) from its concurrent corn oil 

control group only in reduced number of livebom pups per litter (10.2+2.8 versus 11.5+1.7; 11% less 

than control) and reduced pup weight gain (0.6+0.l g versus 0.7+0.2 g; 14% change from control). 

However, the concurrent control values for these two parameters (especially for the number of liveborn 

pups per litter) were unusually high, and the authors reported that these two parameters were generally 

higher than those of other control groups from the same study, thus casting additional uncertainty on 

the biological relevance of these statistically significant changes.
DI-n-OCTYLPHTHALATE 33 

2. HEALTH EFFECTS 

The only other oral study located that examined developmental effects was the NTP Continuous 

Breeding Protocol study previously discussed in Section 2.2.2.5 (Heindel et al. 1989; Morrissey et al. 

1989; NTP 1985). F0 generation CD-l mice were exposed to di-n-octylphthalate doses of 0, 1,820, 

3,620, or 7,460 mg/kg/day for 105 days. F1 generation mice (from the F0 high-dose group) were 

subsequently exposed via lactation and then via feed to an average di-n-octylphthalate dose of 

8,640 mg/kg/day for 85-105 days. In neither case were any significant effects noted for the number 

of live pups per litter, the proportion of pups born alive, pup sex ratio, or the live pup mean weight. 

The combined results of these two studies indicate that di-n-octylphthalate probably has a very low 

potential to induce developmental toxicity, especially in view of the very high doses that were 

evaluated. The highest NOAEL values and all LOAEL values from each reliable study for 

developmental effects in each species and duration category are recorded in Table 2-l and plotted in 

Figure 2- 1. 

2.2.2.7 Genotoxic Effects 

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

di-n-octylphthalate. 

Genotoxicity studies are discussed in Section 2.5. 

2.2.2.8 Cancer 

No studies were located regarding cancer in humans after oral exposure to di-n-octylphthalate. 

Two studies were located in which rats received di-n-octylphthalate dietary exposures of 250 or 

500 mg/kg/day for either 10 or 26 weeks (Carter et al. 1992; DeAngelo et al. 1986). Five male rats 

were first initiated with a single subcarcinogenic intraperitoneal dose of diethylnitrosarnine (30 mg/kg), 

followed by partial hepatectomy. Di-n-octylphthalate caused substantial increases in gammaglutamyltranspeptidase (GGT) positive liver foci when compared with the controls (e.g., from 3.5 to 

20.8 foci/cm2

) or in hepatic levels of marker enzymes for altered cellular foci (GGT and glutathione 

S-transferase [GST]). Only a slight increase (threefold) was observed for carnitine acetyltransferase 

(CAT) activity, a marker for peroxisome proliferation. In contrast, while inducing CAT activity
DI-n-OCTYLPHTHALATE 34

2. HEALTH EFFECTS

37-40-fold, di(2-ethylhexyl)phthalate and mono(ethylhexyl)phthalate actually inhibited the foci-associated

parameters. These results, although not definitive, suggest that di-n-octylphthalate may

promote preneoplastic lesions in the rat liver, probably by a mechanism that does not rely on

peroxisome proliferation.

2.2.3 Dermal Exposure

2.2.3.1 Death

No studies were located regarding death in humans or animals following dermal exposure to di-noctylphthalate.

2.2.3.2 Systemic Effects

No studies were located regarding respiratory, cardiovascular, gastrointestinal, hematological,

musculoskeletal, hepatic, or renal effects in humans or animals after dermal exposure to di-noctylphthalate.

Dermal and ocular effects observed after dermal exposure are discussed below.

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

exposure to di-n-octylphthalate.

In a toxicity summary submitted by Eastman Kodak Company (1978), di-n-octylphthalate was reported

to be a slight skin irritant when applied to the depilatated skin of guinea pigs. However, di-noctylphthalate was not a skin sensitizer in guinea pigs.

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

exposure to di-n-octylphthalate.

In a toxicity summary submitted by Eastman Kodak Company (1978), ocular administration of di-noctylphthalate resulted in slight conjunctival irritation and no cornea1 damage. No further details were

provided.
DI-n-OCTYLPHTHALATE 35 

2. HEALTH EFFECTS 

2.2.3.3 Immunological and Lymphoreticular Effects 

No studies were located regarding immunological and lymphoreticular effects in humans following 

dermal exposure to di-n-octylphthalate. 

Di-n-octylphthalate was negative in a skin sensitization test in guinea pigs (Eastman Kodak Company 

1978). No further details were provided in this summary report. 

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

exposure to di-n-octylphthalate: 

2.2.3.4 Neurological Effects 

2.2.3.5 Reproductive Effects 

2.2.3.6 Developmental Effects 

2.2.3.7 Genotoxic Effects 

Genotoxicity studies are discussed in Section 2.5. 

2.2.3.8 Cancer 

No studies were located regarding cancer in humans or animals following dermal exposure to di-noctylphthalate. 

2.3 TOXICOKINETICS 

No studies were located regarding the toxicokinetics of di-n-octylphthalate in humans or animals 

following inhalation or dermal exposure. Information on the toxicokinetics of di-n-octylphthalate in 

humans following oral exposure is not available. There are studies that provide indirect evidence for 

the oral absorption of di-n-octylphthalate in animals (Albro and Moore 1974; Oishi 1990; Poon et al. 

1995); however, quantitative information is lacking on the rate and extent of absorption following oral 

exposure to di-n-octylphthalate. Information on the distribution of di-n-octylphthalate is limited to oral 

studies in rats by Oishi (1990), which reported the identification of mono-n-octylphthalate in blood and
DI-n-OCTYLPHTHALATE 36

2. HEALTH EFFECTS

testes within 1-24 hours (plasma peak at 3 hours, testes peak at 6 hours) after dosing, and by Poon et

al. (1995), which reported di-n-octylphthalate residues in liver and adipose tissue. The metabolism of

di-n-octylphthalate following acute exposure has been studied in animals in vivo and in vitro

(Albro and Moore 1974; Brodsky et al. 1986; Lake et al. 1977), and the data indicate that, like most

phthalate esters, di-n-octylphthalate can be hydrolyzed at one or both ester linkages to produce the

monoester as well as phthalic acid (minor metabolite). As with other phthalates, subsequent oxidation of

the remaining arylester to short-chained carboxyls, alcohols, and ketones has been demonstrated.

Although one study seems to indicate that urine is the major elimination route of di-n-octylphthalate

metabolites following oral exposure (Albro and Moore 1974), no quantitative information on the rate

and extent of excretion is available. No information is available on the mechanism of action of di-noctylphthalate with respect to its absorption, distribution, metabolism, or excretion.

2.3.1 Absorption

2.3.1.1 Inhalation Exposure

No studies were located regarding the absorption of di-n-octylphthalate in humans or animals

following inhalation exposure.

2.3.1.2 Oral Exposure

No studies were located regarding the absorption of di-n-octylphthalate in humans following oral

exposure.

Evidence of oral absorption in rats is demonstrated in the studies by Albro and Moore (1974), Oishi

(1990), and Poon et al. (1995). Forty-eight hours after a gavage dose of di-n-octylphthalate,

metabolites were detected in the urine. The major metabolite (60% of the metabolites in urine) was

derived from the monoester (Albro and Moore 1974). The mono-n-octylphthalate metabolite was

found in the blood and testes of rats from l-24 hours after oral dosing with peak levels reported at

3 hours (for blood) and 6 hours (for testes) (Oishi 1990). Di-n-octylphthalate was found in the liver

and adipose tissue of rats after they were fed this compound for 13 weeks in dietary concentrations up

to 5,000 ppm, indicating its absorption (Poon et al. 1995). Although there are insufficient quantitative

data for estimating the oral absorption rate, di-n-octylphthalate appears to be absorbed readily;
D-n-OCTYLPHTHALATE 37 

2. HEALTH EFFECTS 

however, it may have to be converted to mono-n-octylphthalate for intestinal absorption to occur (Lake 

et al. 1977). 

2.3.1.3 Dermal Exposure 

No studies were located regarding the absorption of di-n-octylphthalate in humans or animals 

following dermal exposure. 

2.3.2 Distribution 

2.3.2.1 Inhalation Exposure 

No studies were located regarding the distribution of di-n-octylphthalate in humans or animals 

following inhalation exposure. 

2.3.2.2 Oral Exposure 

No studies were located regarding the distribution of di-n-octylphthalate in humans following oral 

exposure. 

Following a single oral dose of 2,000 mg/kg of di-n-octylphthalate in rats, mono-n-octylphthalate was 

detected in blood with peak levels observed at 3 hours and in the testes with peak levels observed at 

6 hours (Oishi 1990). The biological half-life and mean residence time of mono-n-octylphthalate in 

blood were 3.3 and 5.4 hours, respectively. After 13 weeks of oral exposure of rats to di-n-octylphthalate 

in the diet at concentrations up to 5,000 ppm (350 and 403 mg/kg/day in males and 

females, respectively), the livers contained di-n-octylphthalate residues that were either below or just 

slightly above the detection limit (<3 ppm) (Poon et al. 1995). The adipose tissue of rats fed 

5,000 ppm showed di-n-octylphthalate residue levels of 15 ppm (males) and 25 ppm (females). This 

study is limited in that it did not analyze tissues for the presence of metabolites.
DI-n-OCTYLPHTHALATE 38 

2. HEALTH EFFECTS 

2.3.2.3 Dermal Exposure 

No studies were located regarding the distribution of di-n-octylphthalate in humans or animals 

following dermal exposure. 

2.3.3 Metabolism 

Di-n-octylphthalate is readily converted to mono-n-octylphthalate, its major metabolite, by hydrolysis 

of a single ester group. Mono-n-octylphthalate is detected in the blood of rats within an hour after 

oral administration of 2,000 mg/kg di-n-octylphthalate (Oishi 1990). Hydrolysis of di-n-octylphthalate 

at both ester linkages to produce phthalic acid (minor metabolite) may also occur, but this conversion 

does not occur readily. 

As shown in Figure 2-2, mono-n-octylphthalate can undergo ω-, ω-l, α- and β-oxidation to form 

phthalate monoesters (carboxy, keto, or hydroxy esters), which are the major metabolites detected in 

the urine (Albro and Moore 1974). Forty-eight hours after the administration of a gavage dose of 

559 mg/kg/day of di-n-octylphthalate in male CD rats for 2 days, 31% of the administered dose was 

recovered in the urine as derivatives of the monoester varying in the length of the alkyl side chains 

(with terminal or subterminal carboxyl, keto, or hydroxyl moieties). The principal urinary metabolite 

[-(CH2)3COOH side chain] resulted from an initial ω-oxidation and two β-oxidations of the n-octyl 

side chain (Albro and Moore 1974). The remaining amount detected in the urine was represented by 

free phthalic acid and mono-n-octylphthalate. The unmetabolized parent compound was not detected. 

Evidence of the formation of mono-n-octylphthalate and phthalate ester metabolites has been shown in 

in vitro studies. The appearance of mono-n-octylphthalate was observed with preparations of human 

small intestine, rat liver and intestine, ferret liver and intestine, and baboon liver and intestine (Lake et 

al. 1977). However, the amount of phthalic acid and other metabolites in these preparations was either 

minimal or not detected. The study authors concluded that di-n-octylphthalate is probably absorbed 

primarily as mono-n-octylphthalate (Lake et al. 1977). An in vitro study reported the formation of 

five keto acids and two diols when metabolic oxidation of the alkyl groups of di-n-octylphthalate was 

simulated abiotically (Brodsky et al. 1986). Therefore, the in vivo and in vitro data indicate that major 

oxidation may occur in the remaining alkyl chain after di-n-octylphthalate has been hydrolyzed to the

DI-n-OCTYLPHTHALATE 40 

2. HEALTH EFFECTS 

monoester. It is not known for certain whether di-n-octylphthalate is absorbed by the intestine or 

whether it must first be converted to mono-n-octylphthalate. 

2.3.4 Excretion 

2.3.4.1 Inhalation Exposure 

No studies were located regarding the excretion of di-n-octylphthalate in humans or animals following 

inhalation exposure. 

2.3.4.2 Oral Exposure 

No studies were located regarding the excretion of di-n-octylphthalate in humans following oral 

exposure. 

Following gavage administration of 559 mg/kg/day of di-n-octylphthalate to rats, metabolites 

accounting for 31% of the administered dose were detected in the urine at 48 hours postexposure 

(Albro and Moore 1974). 

2.3.4.3 Dermal Exposure 

No studies were located regarding the excretion of di-n-octylphthalate in humans or animals following 

dermal exposure. 

2.4 MECHANISMS OF ACTION 

No studies were located regarding mechanisms of action for absorption or distribution of di-noctylphthalate in humans or animals following inhalation, oral, or dermal exposure. 

Di-n-octylphthalate has been shown to be a mild liver toxin at high doses in acute- and intermediateduration studies in rodents. While the mechanism of action for these hepatic effects is not known, dinoctylphthalate does not appear to behave like other phthalate esters such as di(2-ethylhexyl)phthalate, 

which have been shown to be hypolipidemic peroxisome proliferators. Instead, the liver changes
DI-n-OCTYLPHTHALATE 41 

2. HEALTH EFFECTS 

associated with exposure to di-n-octylphthalate are characterized by marked centrilobular accumulation 

of fat and loss of glycogen, accompanied by reduced glucose-6-phosphatase activity and some 

centrilobular necrosis. However, these effects have been noted in only one study (Mann et al. 1983, 

and were not seen in the multigeneration study in mice by NTP (Heindel et al. 1989; Morrissey et al. 

1989; NTP 1985) or other studies in rats (Lake et al. 1984, 1986; Oishi and Hiraga 1980). 

2.5 RELEVANCE TO PUBLIC HEALTH 

Populations living in areas surrounding hazardous waste sites may be exposed to di-n-octylphthalate 

primarily via ingestion of drinking water. Other possible routes of exposure are inhalation of 

contaminated air or dermal contact with contaminated water. For the general population (i.e., 

including individuals not living in the vicinity of hazardous waste sites), most exposure to di-noctylphthalate occurs through the use of consumer products containing it. For example, exposure to 

di-n-octylphthalate can occur in people receiving medical treatments that involve the use of polyvinyl 

chloride tubing from which di-n-octylphthalate can leach. Exposure of the general population can also 

occur by ingestion of contaminated foods into which di-n-octylphthalate has leached from packaging 

materials, by ingestion of contaminated seafood, by drinking contaminated water, or by inhalation of 

contaminated air. Occupational exposure to di-n-octylphthalate can occur in industrial facilities where 

it is used in the manufacture of plastics or consumer products. 

No information is available on the possible health effects of di-n-octylphthalate in humans. The liver 

is the only target organ that has been identified for di-n-octylphthalate in animals following acute- and 

intermediate-duration oral and parenteral exposure. Acute parenteral studies in animals provided data 

that suggest that di-n-octylphthalate may have adverse effects on the immune system, but the relevance 

of this route of exposure to humans exposed to di-n-octylphthalate at hazardous waste sites is not 

known. Di-n-octylphthalate does not appear to induce reproductive toxicity as do other phthalate 

esters [e.g., di(2-ethylhexyl)phthalate], and oral developmental toxicity studies with di-n-octylphthalate 

have yielded negative results. A decrease in fetal weight and an increase in the incidence of visceral 

malformations were noted in the offspring of rats administered high doses of di-n-octylphthalate by 

intraperitoneal injection, but the relevance of this study to humans is not known. The only available 

data on the potential carcinogenicity of di-n-octylphthalate suggest that it may be a tumor promoter, 

but nothing is known about the ability of this compound to induce cancer by itself. In vitro
DI-n-OCTYLPHTHALATE 42 

2. HEALTH EFFECTS 

genotoxicity data indicate that di-n-octylphthalate is not genotoxic, but there is no information on the 

in vivo genotoxic potential of this compound. 

Minimal Risk Levels for Di-n-octylphthalate 

Inhalation 

No inhalation MRLs were derived for di-n-octylphthalate. No data exist on the effects of acute-, 

intermediate-, or chronic-duration inhalation exposure to di-n-octylphthalate. 

Oral 

Since no human studies were available, animal studies were used for the derivation of the MRL. 

• An MRL of 3 mg/kg/day has been derived for acute oral exposure to di-n-octylphthalate. This 

MRL is based on liver effects observed in rats administered di-n-octylphthalate via gavage at a 

dose of 1,000 mg/kg/day (Lake et al. 1986). The hepatic effects consisted of a statistically 

significant (p<0.01) 17% increase in relative liver weight and a statistically significant (p<0.05) 

reduction in enzyme (7-ethoxycoumarin O-deethylase) activities. The LOAEL was divided by an 

uncertainty factor of 300 (3 for use of a minimal LOAEL, 10 for extrapolation from animals to 

humans, and 10 for human variability). The choice of liver toxicity as the basis for the acute 

oral MRL is supported by necrosis and mild hepatic fatty changes seen in other acute- and 

intermediate-duration studies in rats (DeAngelo et al. 1986; Lake et al. 1984; Mann et al. 1985; 

Poon et al. 1995). 

• An MRL of 0.4 mg/kg/day has been derived for intermediate-duration oral exposure to di-noctylphthalate. This MRL is based on a NOAEL of 40.8 mg/kg/day for liver effects that were 

observed in rats fed di-n-octylphthalate in the diet at a dose of 350.1 mg/kg/day (males) or 

402.9 mg/kg/day (females) (Poon et al. 1995). These hepatic effects consisted of a statistically 

significant (p<0.05) increase in hepatic ethoxyresorufin-0-deethylase activity and histological 

changes in hepatic architecture, including accentuation of zonation and perivenous cytoplasmic 

vacuolation. Thyroid toxicity (decreased colloid density and reduced follicle size) was also noted 

at this concentration. The NOAEL was divided by an uncertainty factor of 100 (10 for
DI-n-OCTYLPHTHALATE 43 

2. HEALTH EFFECTS 

extrapolation from animals to humans and 10 for human variability). Support for the use of 

hepatic toxicity as the basis of the intermediate MRL is provided by other studies that show 

necrosis and other fatty changes after acute- and intermediate-duration exposure of rats 

(DeAngelo et al. 1986; Lake et al. 1984, 1986; Mann et al. 1985). 

No chronic oral MRLs were derived for di-n-octylphthalate because no reliable data exist on adverse 

effects of chronic-duration oral exposure to di-n-octylphthalate. 

Death. No studies were located regarding death in humans after exposure to di-n-octylphthalate. 

LD50 values in rodents have been reported for di-n-octylphthalate following both oral and parenteral 

administration. Oral LD50 values are reported to be 53,700 mg/kg for rats (Dogra et al. 1987) and 

13,000 mg/kg for mice (Dogra et al. 1989). The intraperitoneal LD50 in rats is >48,900 mg/kg (Singh 

et al. 1972). These values indicate that di-n-octylphthalate is relatively nonlethal and should not 

present a risk for death in individuals exposed to this compound in the vicinity of hazardous waste 

sites. 

Systemic Effects 

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

animals following inhalation or dermal exposure to di-n-octylphthalate. No studies were located 

regarding gastrointestinal effects in humans following oral exposure to this compound. 

No pathological changes of the pancreas were exhibited by rats following intermediate-duration 

exposure to di-n-octylphthalate in the diet (Mann et al. 1985). The available information is 

insufficient to assess whether adverse gastrointestinal effects are likely to occur in humans exposed to 

di-n-octylphthalate in the vicinity of hazardous waste sites, but the limited information discussed above 

suggests that such effects are unlikely. 

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

following inhalation or dermal exposure to di-n-octylphthalate. No studies were located regarding 

hematological effects in humans following oral exposure to this compound.
DI-n-OCTYLPHTHALATE 44

2. HEALTH EFFECTS

The data from one intermediate-duration oral study in rats suggests that di-n-octylphthalate does not

cause any hematological effects (Poon et al. 1995), but due to the limited data available, this cannot be

stated with certainty.

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

inhalation or dermal exposure to di-n-octylphthalate. No studies were located regarding hepatic effects

in humans following oral exposure to this compound.

Results from acute- and intermediate-duration oral studies in small numbers of rats conducted at

relatively high doses suggest that the liver is a target for di-n-octylphthalate-induced toxicity. Hepatic

effects noted in these studies include gross changes in appearance, small but statistically significant

increases in relative organ weight, ethoxyresorufin-O-deethylase activity, alteration in the activity of

several hepatic microsomal enzymes, loss of centrilobular glycogen, cytoplasmic vacuolation,

accentuation of zonation, proliferation and dilation of the smooth endoplasmic reticulum accompanied

by some loss of rough endoplasmic reticulum, fat accumulation, and occasional necrosis (Lake et al.

1984, 1986; Mann et al. 1985; Oishi and Hiraga 1980, 1982; Poon et al. 1995). In addition, rats

exposed to dietary concentrations of mono-n-octylphthalate equivalent to 1,000 mg/kg/day exhibited a

variety of significant alterations in serum lipid composition, reflecting a possible effect on hepatic

metabolism of lipids (Oishi and Hiraga 1982). However, di-n-octylphthalate does not appear to

behave like other phthalate esters such as di(2-ethylhexyl)phthalate, which has been shown to be a

hypolipidemic peroxisome proliferator. Based on these results, adverse hepatic effects may occur in

individuals living in the vicinity of hazardous waste sites if di-n-octylphthalate is present at sufficiently

high levels in the substances consumed (e.g., water).

Renal Effects. No studies were located regarding renal effects in humans or animals following

inhalation or dermal exposure to di-n-octylphthalate. No studies were located in humans following

oral exposure to this compound.

Limited information obtained from oral studies in rats and mice suggests that exposure to di-noctylphthalate, even at relatively high doses, does not affect the kidney, as evidenced by a lack of

change in kidney weight or kidney gross and microscopic pathology (Foster et al. 1980; Heindel et al.

1989; Mann et al. 1985; Morrissey et al. 1989; NTP 1985; Oishi and Hiraga 1980; Poon et al. 1995),

although one study noted increased absolute kidney weight in rats with no gross or microscopic
DI-n-OCTYLPHTHALATE 45 

2. HEALTH EFFECTS 

change in the kidney (Heindel et al. 1989; Morrissey et al. 1989; NTP 1985). Therefore, based on this 

limited information, it does not appear that exposure to di-n-octylphthalate at the levels expected to be 

present in the vicinity of hazardous waste sites is likely to induce adverse renal effects in humans. 

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

following inhalation or dermal exposure to di-n-octylphthalate. No studies were located in humans 

following oral exposure to this compound. 

Data from acute- and intermediate-duration studies in rats suggests that di-n-octylphthalate may cause 

adverse effects on the thyroid gland. The effects observed include decreased thryoxine levels, 

histopathological changes (reduced follicle size and colloid density), and ultrastructural changes 

(enlargement of lysosomes and Golgi apparatus, mitochondrial damage) (Hinton et al. 1986; Poon et 

al. 1995). Further data are necessary to determine whether thyroid effects might occur in persons 

living in the vicinity of hazardous waste sites as a result of exposure to di-n-octylphthalate. 

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

inhalation or dermal exposure to di-n-octylphthalate. No studies were located in humans following 

oral exposure to this compound. 

In a toxicity summary submitted by Eastman Kodak Company (1978), di-n-octylphthalate was reported 

to be a slight skin irritant when applied to the depilatated skin of guinea pigs, but not a skin sensitizer 

in guinea pigs. No further details were provided; however, it does not appear that di-n-octylphthalate 

is likely to cause dermal irritation. 

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

inhalation or dermal exposure to di-n-octylphthalate. No studies were located in humans following 

oral exposure to this compound. 

In a toxicity summary submitted by Eastman Kodak Company (1978), ocular administration of di-noctylphthalate in guinea pigs resulted in slight conjunctival irritation and no cornea1 damage. No 

further details were provided; however, it does not appear that di-n-octylphthalate is likely to cause 

ocular irritation.
DI-n-OCTYLPHTHALATE 46 

2. HEALTH EFFECTS 

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

following inhalation or dermal exposure to di-n-octylphthalate. No studies were located in humans 

following oral exposure to this compound. 

Data from various acute- and intermediate-duration oral studies in rats and mice conducted at relatively 

high doses indicate that exposure to di-n-octylphthalate does not adversely affect body weight gain or 

food consumption (Carter et al. 1992; Heindel et al. 1989; Mann et al 1985; Morrissey et al. 1989; 

NTP 1985; Oishi and Hiraga 1980, 1982; Poon et al. 1995). 

Other Systemic Effects. No studies were located regarding other systemic effects in humans or 

animals following inhalation or dermal exposure to di-n-octylphthalate. No studies were located in 

humans following oral exposure to this compound. 

Although a rough hair coat was observed in mice fed 15,000 mg/kg/day for 14 days (Heindel et al. 

1989; NTP 1985), it is not expected that other systemic signs of toxicity would be observed in 

individuals exposed to di-n-octylphthalate in the area surrounding hazardous waste sites. 

Immunological and Lymphoreticular Effects. No studies were located regarding immunological 

or lymphoreticular effects in humans or animals following inhalation exposure to di-n-octylphthalate, 

or in humans following oral or dermal exposure to this compound. 

Limited data in rats and mice suggest that di-n-octylphthalate can exert immunotoxic effects following 

acute oral or parenteral exposure to relatively high doses. These effects are reflected in changes in the 

weight and morphology of various lymphoreticular organs (thymus, spleen, and lymph nodes), altered 

activity of humoral antibody-forming cells and cellular mediators of immunity, and reduced resistance 

to bacterial, viral, protozoan, and other parasitic infection (Dogra et al. 1985, 1987, 1989). 

The available information suggests that exposure to di-n-octylphthalate may adversely affect immune 

function in individuals living in the vicinity of hazardous waste sites if the individuals ingest 

sufficiently high levels. Because of its low vapor pressure, exposure to high levels of di-n-octylphthalate 

by inhalation is not likely.
DI-n-OCTYLPHTHALATE 47 

2. HEALTH EFFECTS 

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

following inhalation or dermal exposure to di-n-octylphthalate. No studies were located regarding 

neurological effects in humans following oral exposure to di-n-octylphthalate. 

No clinical signs of neurotoxicity were noted in acute- and intermediate-duration dietary exposure 

studies using mice (Heindel et al. 1989; NTP 1985). Although these data are limited, it is not believed 

that the low-level exposure to di-n-octylphthalate that occurs at hazardous waste sites will result in 

neurotoxicity. 

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

following inhalation or dermal exposure to di-n-octylphthalate. No studies were located in humans 

following oral exposure to this compound. However, di-n-octylphthalate has been shown to cause 

significant decreases in human sperm motility in vitro (Fredricsson et al. 1993). 

The results of several acute- and intermediate-duration oral studies in rodents indicate that the potential 

of di-n-octylphthalate to cause adverse reproductive effects is low. Unlike other phthalate esters such 

as di(2-ethylhexyl)phthalate, di-n-octylphthalate does not appear to adversely affect testicular function 

or morphology (Foster et al. 1980; Gray and Butterworth 1980; Heindel et al. 1989; Morrissey et al. 

1989; NTP 1985; Oishi 1990; Oishi and Hiraga 1980; Poon et al. 1995). However, some 

ultrastructural alterations in Leydig cells, including vesiculation of the smooth endoplasmic reticulum, 

were noted in rats administered di-n-octylphthalate by gavage on 2 consecutive days (Jones et al. 

1993). Leydig cells obtained from rats that were cultured and stimulated by LH to measure cellular 

integrity by examining testosterone output showed decreased testosterone production when incubated 

with mono-n-octylphthalate, the major metabolite of di-n-octylphthalate (Jones et al. 1993). 

Examination of these cells exposed in vitro showed that mono-n-octylphthalate caused an increase in 

filopodial proliferation from the cell stroma and basal lamellar processes, dilatation of the smooth 

endoplasmic reticulum, and mitochondrial swelling and degeneration. No adverse effects on the 

female estrous cycle or on any index of reproductive function were seen in a multigeneration study in 

mice (Heindel et al. 1989; Morrissey et al. 1989; NTP 1985). Thus, it is unlikely that individuals 

exposed to di-n-octylphthalate in the vicinity of hazardous waste sites are at risk for adverse 

reproductive effects resulting from exposure to this compound.
DI-n-OCTYLPHTHALATE 48

2. HEALTH EFFECTS

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

animals following inhalation or dermal exposure to di-n-octylphthalate. No studies were located in

humans following oral exposure to this compound.

The results of two oral studies in mice (one being a multigeneration reproductive toxicity study)

indicate that di-n-octylphthalate has a very low potential to induce adverse developmental effects,

especially in view of the very high doses that were evaluated in these studies (Hardin et al. 1987;

Heindel et al. 1989; Morrissey et al. 1989; NIOSH 1983; NTP 1985). No statistically significant

and/or biologically significant effects were observed with respect to the incidence of skeletal or

visceral malformations in offspring exposed in utero. A significant decrease in fetal survival was

reported in one study (Hardin et al. 1987) of mice given 9,780 mg/kg/day di-n-octylphthalate by

gavage during gestation days 6-13. A small but significant decrease in average fetal weight and a

significantly increased incidence of gross fetal malformations were observed in the offspring of rats

administered 4,890 mg/kg/day of di-n-octylphthalate by intraperitoneal injection (Singh et al. 1972).

Given that the effects seen following parenteral administration may not be relevant to human exposure

(e.g., different metabolism), the available information suggests that adverse developmental effects are

not likely to occur in humans exposed to di-n-octylphthalate in the vicinity of hazardous waste sites.

Genotoxic Effects. No studies were located that assessed the potential, if any, of

di-n-octylphthalate to induce genotoxic effects in either humans or animals exposed via the inhalation,

oral, or dermal routes. No mammalian cell assays on di-n-octylphthalate were found.

There is, however, a relatively sizable database of well-conducted microbial assays. As part of the

NTP, a series of 34 phthalates or related compounds, including di-n-octylphthalate (98%), were

evaluated for their potential to induce reverse gene mutations in the Salmonella

typhimurium/mammalian microsome preincubation assay (Zeiger et al. 1982, 1985). Concentrations of

di-n-octylphthalate ranging from 100 to 10,000 ug/plate in either the presence or absence of exogenous

metabolic activation derived from Aroclor 1254-induced rat or hamster liver fractions were not

mutagenic in S. typhimurium TA1535, TA1537, TA98, or TAL00. Similar evidence that

di-n-octylphthalate is not a mutagen for S. typhimurium strains has been reported in other

preincubation suspension assays (Seed 1982; Shibamoto and Wei 1986) and in plate incorporation

assays (Florin et al. 1980; Goodyear 1981a; Sato et al. 1994; Shibamoto and Wei 1986).

Di-n-octylphthalate levels ranging from 100 to 2,000 μg/mL (without S9), and 2,000 μg/mL (with
DI-n-OCTYLPHTHALATE 49

2. HEALTH EFFECTS

S9, Aroclor 1254-induced rat liver) did not induce deoxyribonucleic acid (DNA) damage in

DNA-repair deficient E. coli p3478 (Goodyear 1981b). Di-n-octylphthalate also showed a negative

response in a prokaryotic SOS chromotest assay (Sato et al. 1994). However, the mutagenicity was

increased two-fold in the presence of di-n-octylphthalate (Sato et al. 1994).

Extracts of waste water, drinking water, soil, or sediment samples collected from various municipal

and industrial solid and/or waste water sites were found to be mutagenic in S. typhimurium TA98 and

TAL00 (Wang et al. 1990). Although di-n-octylphthalate (8.9 μg/L) was identified as one the

18 contaminants in the National Bureau of Standards reference sludge sample, several well-characterized

mutagens were among the contaminants. It is, therefore, unlikely that the mutagenic

activity uncovered in these samples was associated with di-n-octylphthalate but rather with the known

mutagens that were listed among the 18 contaminants.

Overall, the results of microbial testing indicate that di-n-octylphthalate is not a mutagen. Although

the database for in vitro genetic toxicology testing is limited, the majority of reported studies were

well conducted and showed a high degree of concordance. Based on the available information, there

is sufficient valid in vitro data to conclude that di-n-octylphthalate is devoid of genotoxic activity in

bacterial test systems. No conclusions can be reached regarding potential effects on other systems in

vitro or in vivo.

Summarized findings from the in vitro genotoxicity studies are presented in Table 2-2.

Cancer. No studies were located regarding cancer in humans or animals following inhalation or

dermal exposure to di-n-octylphthalate, and no studies were located in humans following oral exposure

to this compound.

Rats exposed to di-n-octylphthalate in the diet for either 10 or 26 weeks following a single

subcarcinogenic intraperitoneal injection of diethylnitrosamine and partial hepatectomy exhibited

increases in GGT-positive liver foci that were not associated with peroxisome proliferation (Carter et

al. 1992; DeAngelo et al. 1986). These results suggest that di-n-octylphthalate may be effective in

promoting preneoplastic lesions in the rat liver, probably by a mechanism that does not rely on

peroxisome proliferation.

DI-n-OCTYLPHTHALATE 51

2. HEALTH EFFECTS

The carcinogenic potential of di-n-octylphthalate has not been categorized by either IARC, NTP, or

EPA.

2.6 BIOMARKERS OF EXPOSURE AND EFFECT

Biomarkers are broadly defined as indicators signaling events in biologic systems or samples. They

have been classified as markers of exposure, markers of effect, and markers of susceptibility

(NAS/NRC 1989).

Due to a nascent understanding of the use and interpretation of biomarkers, implementation of

biomarkers as tools of exposure in the general population is very limited. A biomarker of exposure is

a xenobiotic substance or its metabolite(s), or the product of an interaction between a xenobiotic agent

and some target molecule(s) or cell(s) that is measured within a compartment of an organism

(NAS/NRC 1989). The preferred biomarkers of exposure are generally the substance itself or

substance-specific metabolites in readily obtainable body fluid(s) or excreta. However, several factors

can confound the use and interpretation of biomarkers of exposure. The body burden of a substance

may be the result of exposures from more than one source. The substance being measured may be a

metabolite of another xenobiotic substance (e.g., high urinary levels of phenol can result from

exposure to several different aromatic compounds). Depending on the properties of the substance

(e.g., biologic half-life) and environmental conditions (e.g., duration and route of exposure), the

substance and all of its metabolites may have left the body by the time 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 di-n-octylphthalate are discussed in Section 2.6.1.

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

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

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

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

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

decreased lung capacity. Note that these markers are not often substance specific. They also may not

be directly adverse, but can indicate potential health impairment (e.g., DNA adducts). Biomarkers of

effects caused by di-n-octylphthalate are discussed in Section 2.6.2.
DI-n-OCTYLPHTHALATE 52

2. HEALTH EFFECTS

A biomarker of susceptibility is an indicator of an inherent or acquired limitation of an organism’s

ability to respond to the challenge of exposure to a specific xenobiotic substance. It can be an

intrinsic genetic or other characteristic or a preexisting disease that results in an increase in absorbed

dose, a decrease in the biologically effective dose, or a target tissue response. If biomarkers of

susceptibility exist, they are discussed in Section 2.8, Populations That Are Unusually Susceptible.

2.6.1 Biomarkers Used to Identify or Quantify Exposure to Di-n-octylphthalate

Animal studies have shown that di-n-octylphthalate metabolites (primarily the corresponding phthalate

monoesters) can be measured in the urine of rats orally exposed to di-n-octylphthalate. Therefore,

these phthalate monoesters could be useful biomarkers of exposure. There are no other known

biomarkers of exposure to di-n-octylphthalate.

2.6.2 Biomarkers Used to Characterize Effects Caused by Di-n-octylphthalate

No biomarkers of effects caused by di-n-octylphthalate have been identified in humans or animals.

2.7 INTERACTIONS WITH OTHER SUBSTANCES

No studies have been identified that investigated the effects of exposure to di-n-octylphthalate together

with other chemicals. An in vivo assay using S. typhimurium TA98 showed that di-n-octylphthalate

enhanced the mutagenicity of two tryptophan pyrolysis products, which is suggestive of increased

mutagenic activity in high-temperature cooking if di-n-octylphthalate is present (Sato et al. 1994). .

2.8 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE

A susceptible population will exhibit a different or enhanced response to di-n-octylphthalate than will

most persons exposed to the same level of di-n-octylphthalate in the environment. Reasons include

genetic make-up, developmental stage, age, health and nutritional status (including dietary habits that

may increase susceptibility, such as inconsistent diets or nutritional deficiencies), and substance

exposure history (including smoking). These parameters may result in decreased function of the

detoxification and excretory processes (mainly hepatic, renal, and respiratory) or the pre-existing

compromised function of target organs (including effects or clearance rates and any resulting
DI-n-OCTYLPHTHALATE 53 

2. HEALTH EFFECTS 

end-product metabolites). For these reasons we expect the elderly with declining organ function and 

the youngest of the population with immature and developing organs will generally be more vulnerable 

to toxic substances than healthy adults. Populations who are at greater risk due to their unusually high 

exposure are discussed in Section 5.6, Populations With Potentially High Exposure. 

Studies in animals suggest that, unlike some other phthalate esters, the potential for adverse 

reproductive or developmental effects following exposure to di-n-octylphthalate by the route most 

relevant to human exposure (oral) is very low (Foster et al. 1980; Gray and Butterworth 1980; Hardin 

et al. 1987; Heindel et al. 1989; Mann et al. 1985; Morrissey et al. 1989; NIOSH 1983; NTP 1985; 

Oishi 1990; Oishi and Hiraga 1980). Therefore, it does not appear that individuals of child-bearing 

age or embryos/fetuses are likely to be unusually susceptible to the effects of di-n-octylphthalate. No 

other information is available on populations with above-average susceptibility to di-n-octylphthalate. 

2.9 METHODS FOR REDUCING TOXIC EFFECTS 

This section describes clinical practice and research concerning methods for reducing toxic effects of 

exposure to di-n-octylphthalate. 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 di-noctylphthalate. When specific exposures have occurred, poison control centers and medical 

toxicologists should be consulted for medical advice. 

2.9.1 Reducing Peak Absorption Following Exposure 

Following dermal exposure to di-n-octylphthalate, it has been suggested that the skin be washed 

immediately with copious amounts of soapy water (Stutz and Ulin 1992). If the eyes are exposed to 

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

ingestion of di-n-octylphthalate, it has been suggested that one to two glasses of water should be 

administered (Stutz and Ulin 1992). 
DI-n-OCTYLPHTHALATE 54

2. HEALTH EFFECTS

2.9.2 Reducing Body Burden

Administration of activated charcoal as an absorptive surface for di-n-octylphthalate has been

suggested (Stutz and Ulin 1992). If ingestion of large amounts of di-n-octylphthalate 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 (Stutz and Ulin 1992).

2.9.3 Interfering with the Mechanism of Action for Toxic Effects

Di-n-octylphthalate has been shown to be a liver toxin at high doses in acute- and intermediate-duration

animal studies. Di-n-octylphthalate does not appear to behave like other phthalate esters, such

as di(2-ethylhexyl)phthalate, which have been shown to be hypolipidemic peroxisome proliferators.

Rather, its effects on the liver are more characteristic of other “classic hepatotoxins” (Lake et al. 1984,

1986; Mann et al. 1985). However, the specific mechanism(s) of action for inducing the hepatotoxic

effects of di-n-octylphthalate is not known. Therefore, there are currently no methods available for

interfering with the mechanism of action for the toxic effects of di-n-octylphthalate.

2.10 ADEQUACY OF THE DATABASE

Section 104(i)(5) of CERCLA, as amended, directs the Administrator of ATSDR (in consultation with

the Administrator of EPA and agencies and programs of the Public Health Service) to assess whether

adequate information on the health effects of di-n-octylphthalate 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 di-n-octylphthalate.

The following categories of possible data needs have been identified by a joint team of scientists from

ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that if met would

reduce the uncertainties of human health assessment. This definition should not be interpreted to mean

that all data needs discussed in this section must be filled. In the future, the identified data needs will

be evaluated and prioritized, and a substance-specific research agenda will be proposed.
DI-n-OCTYLPHTHALATE 55 

2. HEALTH EFFECTS 

2.10.1 Existing Information on Health Effects of Di-n-octylphthalate 

The existing data on health effects of inhalation, oral, and dermal exposure of humans and animals to 

di-n-octylphthalate are summarized in Figure 2-3. The purpose of this figure is to illustrate the 

existing information concerning the health effects of di-n-octylphthalate. Each dot in the figure 

indicates that one or more studies provide information associated with that particular effect. The dot 

does not necessarily imply anything about the quality of the study or studies, nor should missing 

information in this figure be interpreted as a “data need.” A data need, as defined in ATSDR’s 

Decision Guide for Identifying Substance-Specific Data Needs Related to Toxicological Profiles 

(ATSDR 1989a), 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 2-3, no information is available on the health effects of di-n-octylphthalate in 

humans, and very little information is available in animals. All of the available information on the 

toxicity of di-n-octylphthalate in animals comes from studies in which this compound was 

administered by either the oral or parenteral route; no information is available from animal studies on 

the toxicity of di-n-octylphthalate following inhalation or dermal exposure. Acute oral and parenteral 

lethality studies are available in animals, and the hepatic, immunological, reproductive, and 

developmental toxicity of di-n-octylphthalate has been studied following acute- and intermediate-duration 

parenteral and/or oral exposure in rats and mice. Among reliable studies, the longest duration 

found for di-n-octylphthalate exposure by any route is in a multigeneration reproductive toxicity oral 

gavage study (85-105 days) in mice and a promotion test dietary study (182 days) in rats. 

2.10.2 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 di-n-octylphthalate. No 

information is available on the effects of acute-duration oral exposure to di-n-octylphthalate in humans. 

Therefore, the data are not sufficient to derive an acute inhalation MRL. An oral LD50 of di-noctylphthalate of 53,700 mg/kg has been reported for male rats (Dogra et al. 1987). An oral LD50 of 

13,000 mg/kg has been reported for mice (Dogra et al. 1989). LD50 values are also available for

DI-n-OCTYLPHTHALATE 57

2. HEALTH EFFECTS

intraperitoneal exposure (Dogra et al. 1985). The liver appears to be the target organ following acuteduration oral exposure to di-n-octylphthalate, and an acute oral MRL of 3 mg/kg/day was calculated

based on increased relative liver weight and enzyme changes (Lake et al. 1986). Gross and

microscopic changes in the liver were observed in rats fed di-n-octylphthalate for 10 days (Mann et al.

1985). Decreased thyroxine levels and ultrastructural changes in the thyroid were noted in rats fed di-noctylphthalate in the diet (2,000 mg/kg/day) for 3 days in the Mann et al. (1985) study (Hinton et al.

1986).

The Mann et al. (1985) study is limited in that too few animals were used, organs other than the liver

were not adequately evaluated, and only males were studied. Although an adequate acute-duration oral

study would be useful to corroborate or refute the thyroid effects seen in the Mann et al. (1985) study,

this does not represent a data need, since an acute oral MRL has been derived. Ingestion of contaminated

drinking water is expected to be the predominant route of exposure for individuals living in the

vicinity of hazardous waste sites. However, acute-duration inhalation and dermal studies in animals

are needed to assess the potential toxicity of di-n-octylphthalate following exposure via these routes

because there are insufficient pharmacokinetic data available to support the extrapolation of data

obtained after oral administration to other routes of exposure.

Intermediate-Duration Exposure. There is no information available to identify target organs in

humans or animals following intermediate-duration inhalation or dermal exposure to di-n-octylphthalate.

Therefore, the data are not sufficient to derive an intermediate-duration inhalation

MRL. No information is available on the effects of intermediate-duration oral exposure to di-noctylphthalate in humans. The liver appears to be the target organ following intermediate-duration oral

exposure to di-n-octylphthalate (DeAngelo et al. 1986; Mann et al. 1985; Poon et al. 1995). An

intermediate-duration oral MRL of 0.4 mg/kg/day was calculated based on increases in hepatic

ethoxyresorufin-O-deethylase activity and histopathological changes in the liver of rats (Poon et al.

1995). Mild microscopic changes were also noted in the thyroid in this study (Poon et al. 1995).

Effects on the thyroid (decreased thyroxine levels, reduction in follicle size and colloid density, and

ultrastructural changes) have been reported in rats fed diets containing di-n-octylphthalate for 21 days

in the Mann et al. (1985) study (Hinton et al. 1986) or 13 weeks (Poon et al. 1995). Both the Mann

et al. (1985) and the DeAngelo et al. (1986) studies are limited in that too few animals were used,

organs other than the liver were not adequately evaluated, and only males were studied. Because

statistical analysis was not performed on the data in the Poon et al. (1995) study and the thyroid
DI-n-OCTYLPHTHALATE 58 

2. HEALTH EFFECTS 

effects that were observed were mild, it is difficult to determine at which concentration the LOAEL for 

these particular effects occurred. Although ingestion of contaminated drinking water is expected to be 

the predominant route of exposure for individuals living in the vicinity of hazardous waste sites, 

intermediate-duration inhalation and dermal studies in animals are needed to assess the potential 

toxicity of di-n-octylphthalate following these routes of exposure because there are insufficient 

pharmacokinetic data available to support the extrapolation of data obtained after oral administration to 

other routes of exposure. 

Chronic-Duration Exposure and Cancer. There is no information available to identify target 

organs in humans following chronic-duration inhalation, oral, or dermal exposure to di-n-octylphthalate. 

Therefore, the data are not sufficient to derive a chronic-duration inhalation MRL. 

Chronic-duration oral toxicity studies using di-n-octylphthalate are needed to identify target organs and 

to establish the levels at which effects may occur. Oral studies are needed because ingestion of 

contaminated drinking water is expected to be the predominant route of exposure for individuals living 

in the vicinity of hazardous waste sites. 

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

exposure to di-n-octylphthalate, and no studies were located in humans following oral exposure to this 

compound. Rats exposed to di-n-octylphthalate in the diet for either 10 or 26 weeks following a 

single subcarcinogenic intraperitoneal injection of diethylnitrosamine and partial hepatectomy exhibited 

increases in GGT-positive liver foci that were not associated with a peroxisome proliferation (Carter et 

al. 1992; DeAngelo et al. 1986). These results suggest that di-n-octylphthalate may be effective in 

promoting preneoplastic lesions in the rat liver, probably by a mechanism that does not rely on 

peroxisome proliferation. An oral cancer bioassay would be useful to establish whether di-n-octylphthalate 

has the potential to be carcinogenic to humans. 

Genotoxicity. There is convincing evidence from microbial assays that di-n-octylphthalate is not a 

mutagen in S. typhimurium (Florin et al. 1980; Goodyear 1981a; Sato et al. 1994; Seed 1982; 

Shibamoto and Wei 1986; Zeiger et al. 1982, 1985) and does not induce DNA damage in E. coli 

(Goodyear 1981b). Although genetic toxicology testing, particularly in mammalian cell systems, is 

limited, the reported studies were well conducted and uniformly negative. It is, therefore, doubtful 

whether further investigation of these end points in other mammalian cell lines would alter the 

negative conclusions. Of greater importance, however, is the demonstrated lack of mutagenesis of the
DI-n-OCTYLPHTHALATE 59

2. HEALTH EFFECTS

rodent hepatocarcinogen, di(2-ethylhexyl)phthalate in a similar battery of in vitro tests. The inactivity

of this carcinogenic phthalate suggests that in vitro genetic toxicology assays may have limited value

for predicting the carcinogenic potential of other phthalates such as di-n-octylphthalate. Nevertheless,

data from whole-animal studies using di-n-octylphthalate are needed since no literature exists on

potential adverse genetic effects in vivo.

Reproductive Toxicity. No studies were located regarding reproductive effects in humans or

animals following inhalation or dermal exposure to di-n-octylphthalate. No studies were located in

humans following oral exposure to this compound. Di-n-octylphthalate caused significant decreases in

human sperm motility in vitro (Fredricsson et al. 1993). The results of several acute- and

intermediate-duration oral studies in rodents indicate that the potential of di-n-octylphthalate to cause

adverse reproductive effects is low. Unlike other phthalate esters such as di(2-ethylhexyl)phthalate, di-noctylphthalate does not appear to adversely affect testicular function or morphology (Foster et al.

1980; Gray and Butterworth 1980; Heindel et al. 1989; Morrissey et al. 1989; NTP 1985; Oishi 1990;

Oishi and Hiraga 1980; Poon et al. 1995). However, some ultrastructural alterations in Leydig cells,

including vesiculation of the smooth endoplasmic reticulum, were noted in rats administered di-noctylphthalate by gavage on 2 consecutive days (Jones et al. 1993). Leydig cells obtained from rats

that were cultured and stimulated by LH to measure cellular integrity by examining testosterone output

showed decreased testosterone production when incubated with mono-n-octylphthalate, the major

metabolite of di-n-octylphthalate (Jones et al. 1993). Examination of these cells exposed in vitro

showed that mono-n-octylphthalate caused ultrastructural changes in several organelles, including the

smooth endoplasmic reticulum dilatation and mitochondrial degeneration. No adverse effects on the

female estrous cycle or on any index of reproductive function were seen in a multigeneration study in

mice (Heindel et al. 1989; Morrissey et al. 1989; NTP 1985). Although it is fairly well established

that di-n-octylphthalate does not induce adverse effects on male reproductive organs or reproductive

performance in either males or females, data on reproductive organ pathology, including ultra-structural

pathology, are needed in any 90-day studies that may be conducted with di-n-octylphthalate.

Developmental Toxicity. No studies were located regarding developmental effects in humans or

animals following inhalation or dermal exposure to di-n-octylphthalate, and no studies were located in

humans following oral exposure to this compound. The results of two oral studies in mice (one being

a multigeneration reproductive toxicity study) indicate that di-n-octylphthalate has a very low potential

to induce adverse developmental effects, especially in view of the very high doses that were evaluated
DI-n-OCTYLPHTHALATE 60 

2. HEALTH EFFECTS 

in these studies (Hardin et al. 1987; Heindel et al. 1989; Morrissey et al. 1989; NIOSH 1983; NTP 

1985). No statistically significant and/or biologically significant effects were observed with respect 

either to embryo or fetal survival or growth, or to the incidence of skeletal or visceral malformations 

in offspring exposed in utero. However, a significant decrease in average fetal weight and a 

significantly increased incidence in gross fetal malformations were observed in the offspring of rats 

administered 4,890 mg/kg/day of di-n-octylphthalate by intraperitoneal injection (Singh et al. 1972). 

However, the effects seen following high-dose parenteral administration may not be relevant to human 

exposure. Well-conducted oral developmental toxicity studies in animals are needed to determine 

whether the negative results obtained in the two studies discussed above (one being a screen and the 

other being a multigeneration reproductive toxicity study not designed specifically to assess 

developmental toxicity) are valid, or if the effects seen after intraperitoneal administration of high 

doses of di-n-octylphthalate are likely to occur after oral administration. There are insufficient 

pharmacokinetic data available to support the extrapolation of data obtained after oral administration to 

other routes of exposure. However, oral studies would be the most useful since ingestion of 

contaminated drinking water is expected to be the predominant route of exposure for individuals living 

in the vicinity of hazardous waste sites. 

Immunotoxicity. No studies were located regarding immunological effects in humans or animals 

following inhalation or dermal exposure to di-n-octylphthalate, or in humans following oral exposure 

to this compound. Limited data in rats or mice suggest that di-n-octylphthalate can exert immunotoxic 

effects following acute oral or parenteral exposure to relative high doses. These effects are reflected in 

changes in the weight and morphology of various lymphoreticular organs (thymus, spleen, and lymph 

nodes), altered activity of humoral antibody-forming cells and cellular mediators of immunity, and 

reduced resistance to bacterial, viral, protozoan, or other parasitic infection (Dogra et al. 1985, 1987, 

1989). Additional data are needed to measure lymphoreticular organs and blood components of the 

immune system in any 90-day study that may be conducted with di-n-octylphthalate because the 

limited information available from animal studies suggests that this compound may exert immunotoxic 

effects. 

Neurotoxicity. No information is available on the neurological effects of di-n-octylphthalate in 

humans or animals following inhalation or dermal exposure or in humans following oral exposure. No 

clinical signs of neurotoxicity were noted in acute and intermediate duration dietary exposure studies 

using mice (Heindel et al. 1989; NTP 1985). Although these data are limited, it is not believed that
DI-n-OCTYLPHTHALATE 61 

2. HEALTH EFFECTS 

the low-level exposure to di-n-octylphthalate that occurs at hazardous waste sites will result in 

neurotoxicity. Because there is no information to suggest that the central nervous system is a target of 

di-n-octylphthalate, no additional information is needed at this time. 

Epidemiological and Human Dosimetry Studies. No epidemiological studies are available on 

populations that have been exposed solely to di-n-octylphthalate. As a result of its use, together with other 

phthalate esters, as a plasticizer in the production of polyvinyl chloride (PVC) resins and cellulose ester 

and polystyrene resins (EPA 1993a; HSDB 1995; Mannsville Chemical Products 

Corporation 1989) 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 di-n-octylphthalate 

and a control population with no known exposure could be identified. However, if 

suitable subpopulations could be found, then a well-conducted and controlled epidemiological study is 

needed to determine the potential target organs of di-n-octylphthalate toxicity in humans and the levels 

at which effects might be expected to occur. In addition, individuals at risk in the vicinity of 

hazardous waste sites could be identified and monitored. 

Biomarkers of Exposure and Effect 

Exposure. The monoester derivatives of di-n-octylphthalate and mono-n-octylphthalate or the 

oxidation products of mono-n-otylphthalates could potentially be used as a biomarker of exposure; 

however, only a few studies have been located that measure these metabolites in body tissues or fluids 

following exposure to di-n-octylphthalate (Albro and Moore 1974; Oishi 1990). Studies that 

investigate the fate and/or elimination of these metabolites are needed to determine its value as a 

biomarker of exposure for di-n-octylphthalate. Additional information on the metabolism of di-noctylphthalate could help identify other potential biomarkers of exposure. 

Effect. Since exposure to di-n-octylphthalate does not produce a unique clinical disease state, no 

biomarkers of effect have been identified. Additional information on the potential health effects of di-noctylphthalate is needed to identify biomarkers of exposure to this compound.
DI-n-OCTYLPHTHALATE 62

2. HEALTH EFFECTS

Absorption, Distribution, Metabolism, and Excretion. No studies were located regarding the

absorption of di-n-octylphthalate in humans and animals following inhalation and dermal exposure.

Information on absorption in humans following oral exposure is not available. There are studies

that suggest oral absorption of di-n-octylphthalate occurs in animals (Albro and Moore 1974; Oishi 1990;

Poon et al. 1995); however, quantitative information is lacking. Additional information, primarily

quantitative data, on absorption of di-n-octylphthalate for all routes of exposure is needed to

understand and predict effects.

Information on the distribution of di-n-octylphthalate is limited to oral studies in rats, one by Oishi

(1990), which reported the identification of mono-n-octylphthalate in blood and testes with peak levels

observed at 3 hours for blood and at 6 hours for testes after dosing, and the other by Poon et al.

(1995), which reported di-n-octylphthalate in the liver that was either below or slightly above detection

limits; higher levels (15-25 ppm) of residue were also found in adipose tissue. However, this latter

study was limited because metabolite levels were not measured. The metabolism of di-n-octylphthalate

following acute exposure has been studied in animals in vivo and in vitro (Albro and

Moore 1974; Brodsky et al. 1986; Lake et al. 1977). Metabolism studies following longer term

exposures are needed in order to determine if metabolic pathways become saturated or altered.

Although the Albro and Moore (1974) study seems to indicate that urine is the major elimination route

of di-n-octylphthalate, additional excretion studies are needed to provide quantitative information.

Additional studies on the mechanism involved in absorption and distribution of the compound are

needed to provide information on how to increase elimination of the compound from the body.

Comparative Toxicokinetics. Based on the rat study by Albro and Moore (1974), di-n-octylphthalate

appears to be readily absorbed following oral administration, metabolized extensively,

and excreted primarily in the urine. Because of the lack of human data and limited animal data on the

absorption, distribution, metabolism, and excretion of di-n-octylphthalate, additional studies are needed

in order to make comparisons on the toxicokinetics across species.

Methods for Reducing Toxic Effects. All of the treatment methods currently available for use

in di-n-octylphthalate ingestion or skin contact are supportive in nature and/or involve decreasing the

absorption or increasing the rate of elimination of di-n-octylphthalate (Stutz and Ulin 1992). Since the

mechanism of di-n-octylphthalate toxicity is not known, there are currently no methods that focus on

mitigating the effects of di-n-octylphthalate by interfering with its mode of action. Therefore, more
DI-n-OCTYLPHTHALATE 63 

2. HEALTH EFFECTS 

information on the mechanism of action for di-n-octylphthalate is needed in order to devise methods 

for the mitigation of its toxic effects. 

2.10.3 On-going Studies 

No on-going studies on the health effects or toxicokinetics of di-n-octylphthalate were found.

DI-n-OCTYLPHTHALATE 65 

3. CHEMICAL AND PHYSICAL INFORMATION 

3.1 CHEMICAL IDENTITY 

Information regarding the chemical identity of di-n-octylphthalate is located in Table 3-l. 

3.2 PHYSICAL AND CHEMICAL PROPERTIES 

Information regarding the chemical and physical properties of di-n-octylphthalate is located in 

Table 3-2. 

There is conflicting information for many of these properties in the literature. A possible explanation 

for the inconsistencies, as discussed in Chapter 2, may come from the use of the nonspecific term “dioctylphthalate.” This conflict has contributed to significant confusion and misinformation in the 

literature with respect to di-n-octylphthalate and the much more common isomer, di(2- 

ethylhexyl)phthalate. Although frequently being interpreted as referring to di-n-octylphthalate, it is 

apparent that in almost all cases “di-octylphthalate” and “DOP” have in fact been used as synonyms 

for di(2-ethylhexyl)phthalate. Therefore, many of the properties found for di-n-octylphthalate or dioctylphthalate may possibly be for di(2-ethylhexyl)phthalate.



DI-n-OCTYLPHTHALATE 69 

4. PRODUCTION, IMPORT, USE, AND DISPOSAL 

4.1 PRODUCTION 

Di-n-octylphthalate is produced commercially as a component of mixed phthalate esters, including 

straight- chain C6, C8, and Cl0 phthalates (EPA 1993a). Di-n-octylphthalate is produced at 

atmospheric pressure or in a vacuum by heating an excess of n-octanol with phthalic anhydride in the 

presence of an esterification catalyst such as sulfuric acid or p-toluenesulfonic acid. The process may 

be either continuous or discontinuous (EPA 1993a; HSDB 1995). Di-n-octylphthalate can also be 

produced by the reaction of n-octylbromide with phthalic anhydride. 

The most recent report available on di-n-octylphthalate lists three commercial producers: Vista 

Chemical Company, Houston, Texas; Aristech Chemical Corporation, Neville Island, Pennsylvania; 

and Teknor Apex Company, Hebronville, Massachusetts and Brownsville, Texas (EPA 1993a). 

Additional reported producers include: Eastman Kodak Company, Rochester, New York (USITC 

1994); Tenneco Chemical, Inc., Chestertown, Maryland (EPA 1987a); Alfa Products, Morton Thiokol, 

Inc., Danvers, Massachusetts; Primachem, Inc., Englewood Cliffs, New Jersey; and GCA Chemical 

Corp., Stamford, Connecticut (HSDB 1995). Table 4-1 lists the U.S. facilities that manufacture or 

process di-n-octylphthalate. 

The current annual production of di-n-octylphthalate is difficult to estimate because of confusion in 

nomenclature regarding the octylphthalate isomers and reported data describing only the entire group 

of dioctyl orthophthalates. A total of 122,384 metric tons of total dioctylphthalates were produced in 

1992 (USITC 1994). The amount of di-n-octylphthalate included in this group was not reported 

because of the possible revelation of confidential business information. 

Table 4-l lists data from the Toxics Release Inventory (TRI) regarding U.S. companies that reported 

the manufacture and use of di-n-octylphthalate in 1992 (TR192 1994). The TRI data should be used 

with caution since only certain types of facilities are required to report. This is not an exhaustive list.



DI-n-OCTYLPHTHALATE 73 

4. PRODUCTION, IMPORT, USE, AND DISPOSAL 

4.2 IMPORT/EXPORT 

In 1988, 6 million pounds of di-octylphthalates (i.e., di-n-octylphthalate and di[2-ethylhexyl]phthalate) 

were imported and 37 million pounds were exported. No data were located on specific quantities for 

di-n-octylphthalate (Mannsville Chemical Products Corporation 1989). 

4.3 USE 

Di-n-octylphthalate is principally used as a plasticizer in the production of plastics (Sittig 1991) and 

PVC resins. When used as a plasticizer, di-n-octylphthalate can represent 5-60% of the total weight 

of the plastics and resins. It increases flexibility and enhances or alters the properties of the material. 

It is also used for cellulose ester and polystyrene resins, as a dye carrier in plastic production 

(primarily PVC), and as a chemical intermediate in the manufacture of adhesives, plastisols, and 

nitrocellulose lacquer coatings (EPA 1993a; HSDB 1995; Mannsville Chemical Products Corporation 

1989). It is a registered active ingredient in pesticides (EPA 1987b) and is found in cosmetics and 

colorants (EPA 1992a). Di-n-octylphthalate also serves as a carrier for catalysts or initiators and as a 

substitute for electrical capacitor fluid (EPA 1992a). 

Flexible PVC resins and other dioctylphthalate-containing plastics and resins are used in a variety of 

industrial and domestic products: plastisols for carpetback coating (EPA 1987b), film, wire, cables, 

and adhesives (HSDB 1995). Additional end-use products are automobile and furniture upholstery, 

wall coverings, window shades, garden hoses, shower curtains, tablecloths, rainwear, shoes, dolls, and 

toys (Mannsville Chemical Products Corporation 1989). 

4.4 DISPOSAL 

Di-n-octylphthalate, including waste containing di-n-octylphthalate, is classified as a hazardous waste 

product by EPA. Generators of waste containing this contaminant must conform to EPA regulations 

for treatment, storage, and disposal (see Chapter 7). Rotary kiln or fluidized bed incineration methods 

are acceptable disposal methods for these wastes. Liquid injection incineration may also be used 

(HSDB 1995).
DI-n-OCTYLPHTHALATE 74 

4. PRODUCTION, IMPORT, USE, AND DISPOSAL 

According to the TRI, 240,609 pounds of di-n-octylphthalate were transferred to landfills and/or 

treatment/disposal facilities in 1992 (see Section 5.2) (TR192 1994). Of this quantity, about 

1,475 pounds were discharged to publicly owned treatment works. A total of 15,302 pounds was 

released to air, land, and water by manufacturing and processing facilities. No di-n-octylphthalate was 

released for underground injection.
DI-n-OCTYLPHTHALATE 75

5. POTENTIAL FOR HUMAN EXPOSURE

5.1 OVERVIEW

Di-n-octylphthalate is released mainly to the atmosphere and to some extent to surface waters in

industrial effluents (TRI92 1994). The compound may be released to soils in the disposal of plastics

wastes. Di-n-octylphthalate is expected to partition mainly to soils and sediment upon release to the

environment (EPA 1979, 1992c). The compound is also bioconcentrated by aquatic organisms,

although biomagnification in aquatic food chains is not expected to be significant (EPA 1992d).

Aerobic biodegradation is the most important transformation process in soils and surface waters (EPA

1992a, 1992c). Other transformation processes include photooxidation in the atmosphere and

photolysis in surface waters (EPA 1992a). As a result of confusion with its branched isomer, di(2-

ethylhexyl)phthalate, limited unambiguous monitoring data are available for di-n-octylphthalate. The

compound has been detected in ambient air, rain, runoff, groundwater, surface water, and sediment.

Human exposure to the compound is expected to occur primarily in workplace settings (HSDB 1995).

General population exposure pathways include inhalation of the volatilized plasticizer, ingestion of

foods contaminated as a result of leaching of di-n-octylphthalate from plastic containers, ingestion of

aquatic organisms that have bioconcentrated the compound, and ingestion of contaminated drinking

water (EPA 1992c). Populations living near hazardous waste sites contaminated with di-n-octylphthalate

may also be exposed through dermal contact with and ingestion of contaminated

groundwater and sediments (ATSDR 1988, 1989b, 1989c). Populations with potentially high

exposures to di-n-octylphthalate include workers in the chemical manufacturing and plastics

manufacturing and processing industries, individuals requiring routine medical care, such as blood

transfusions and kidney dialysis treatments, and individuals living in the vicinity of industrial

manufacturing and processing facilities that may manufacture or use di-n-octylphthalate or of

hazardous waste sites containing di-n-octylphthalate or plastics (HSDB 1995).

Di-n-octylphthalate has been identified in at least 300 of the 1,416 hazardous waste sites on the EPA

National Priorities List (NPL) (HazDat 1995). However, the number of sites evaluated for di-noctylphthalate is not known. The frequency of these sites within the United States can be seen in
DI-n-OCTYLPHTHALATE 76

5. POTENTIAL FOR HUMAN EXPOSURE

Figure 5-1. Of these sites, 298 are located in the United States and 2 are located in the

Commonwealth of Puerto Rico (not shown).

5.2 RELEASES TO THE ENVIRONMENT

Considerable confusion exists in the literature about the TRI release reporting data and monitoring data

available for di-n-octylphthalate and its more common branched isomer, di(2-ethylhexyl)phthalate

(EPA 1992a; Vista Chemical 1992). The confusion exists because the terms “dioctyl phthalate” and

“DOP” are often used as synonyms for di(2-ethylhexyl)phthalate, which is the largest volume

plasticizer used in PVC. Consequently, some of the historical release and monitoring data reported in

the literature as “dioctyl phthalate” and “DOP” refer to the more common branched isomer rather than

di-n-octylphthalate. Therefore, releases of di-n-octylphthalate and concentrations of the compound in

ambient media may actually be lower than historical data suggest. Di-n-octylphthalate was withdrawn

from the TRI effective in 1993 (EPA 1995h). Thus, the data for TRI92 (1994) is the most recent data

that is available from the Toxic Release Inventory for di-n-octylphthalate.

5.2.1 Air

Di-n-octylphthalate may be released to the atmosphere through volatilization of the compound from

plastics, as a result of manufacturing processes, and through incineration (Vista Chemical 1992).

According to TR192 (1994), an estimated total of 15,011 pounds of di-n-octylphthalate, amounting to

about 98% of the total environmental release, were discharged to the atmosphere from manufacturing

and processing facilities in the United States in 1992 (see Table 5-l). The TRI data listed in

Table 5-l should be used with caution since only certain types of facilities are required to report. This

is not an exhaustive list. Furthermore, as noted above, the precise chemical identity of the reported

releases is questionable.

5.2.2 Water

Di-n-octylphthalate is released to surface waters in industrial waste waters from production and use

processes and as a result of spills during its transport, storage, and use (Mathur 1974a). For example,

di-n-octylphthalate was found in one of five industrial process waste waters sampled at an average




DI-n-OCTYLPHTHALATE 81

5. POTENTIAL FOR HUMAN EXPOSURE

concentration of 3,700 μg/L (EPA 1981). Releases to surface waters are expected to undergo

secondary treatment at publicly owned treatment works or at on-site National Pollutant Discharge

Elimination System (NPDES) permitted facilities. Such waste-water treatment systems are expected to

remove 80-90% of the influent di-n-octylphthalate through a combination of adsorption and aerobic

biodegradation by acclimated microorganisms (EPA 1992c Petrasek et al. 1983). The compound is

also released to surface waters from nonpoint sources, such as surface runoff. For example, di-noctylphthalate was found in runoff samples collected in 1982 from Little Rock, Arkansas, Bellevue,

Washington, and Eugene, Oregon, at a 4% frequency of detection in the collected samples and at

concentrations of 0.4-l μg/L. This sampling was conducted as part of the Nationwide Urban Runoff

Program (Cole et al. 1984).

According to TR192 (1994), an estimated total of 41 pounds of di-n-octylphthalate were discharged to

surface waters from manufacturing and processing facilities in the United States in 1992 (see

Table 5-l). An estimated total additional 1,475 pounds were transferred to publicly owned treatment

works. The TRI data listed in Table 5-l should be used with caution since only certain types of

facilities are required to report. This is not an exhaustive list. Furthermore, as noted above, the

precise chemical identity of the reported releases is questionable.

5.2.3 Soil

According to TR192 (1994), an estimated total of 250 pounds of di-n-octylphthalate, amounting to

about 2% of the total environmental release, was discharged to soils from manufacturing and

processing facilities in the United States in 1992 (see Table 5-l). An estimated total additional

239,134 pounds were transferred to off-site waste treatment, storage, and disposal facilities. The TRI

data listed in Table 5-l should be used with caution since only certain types of facilities are required

to report. This is not an exhaustive list. Furthermore, as noted above, the precise chemical identity of

the reported releases is questionable.
DI-n-OCTYLPHTHALATE 82 

5. POTENETIAL FOR HUMAN EXPOSURE 

5.3 ENVIRONMENTAL FATE 

5.3.1 Transport and Partitioning 

Upon release to surface waters, di-n-octylphthalate is expected to partition mainly to sediments and to 

suspended particulates. In a pilot-scale waste-water treatment system, di-n-octylphthalate partitioned 

mainly to primary treatment sludge (Petrasek et al. 1983). The compound strongly adsorbs to organic 

matter contained in soils and sediments; adsorption is probably the most important transport process 

for the compound in surface waters (EPA 1979, 1992c). Volatilization from surface waters is expected 

to be a slow and unimportant process. For example, the estimated volatilization half-life from a model 

river 1 meter deep with a current of 1 meter/second and a wind speed of 3 meters/second is 13 days 

(HSDB 1995). In a pilot-scale study of a typical waste-water treatment plant employing both primary 

and secondary activated sludge treatment processes, no di-n-octylphthalate was lost from the system by 

air stripping (Petrasek et al. 1983). However, in a study simulating the behavior of di-n-octylphthalate 

in different aquatic systems, volatilization was estimated to account for up to 20% of the losses of the 

compound from certain standing surface water systems characterized by long water detention times 

(e.g., ponds, lakes), especially in relatively pristine lakes where loss by biodegradation is not likely to 

be important (Wolfe et al. 1980). This same study suggests that in running surface waters, such as 

rivers, di-n-octylphthalate is most likely to be lost by transport out of the system. 

Di-n-octylphthalate also strongly adsorbs to soils and does not undergo leaching to groundwater, as 

indicated by its estimated soil organic carbon/water partition coefficient (Koc) of about 19,000. 

Volatilization from soils is not expected to be significant (HSDB 1994; Vista Chemical 1992). 

Di-n-octylphthalate released to the atmosphere may partition to soils and surface waters through wet 

(Ligocki et al. 1985) and dry (Vista Chemical 1992) deposition processes. 

Di-n-octylphthalate is bioconcentrated by aquatic organisms (EPA 1992d). In a 33-day combined 

terrestrial-aquatic model ecosystem study, the following di-n-octylphthalate bioconcentration factors 

(BCFs) were reported: (1) algae - 28,500; (2) daphnids - 2,600; (3) fish and mosquitoes - 9,400; and 

(4) snails - 13,600. However, the half-life for the disappearance of di-n-octylphthalate from this model 

system was estimated to be about 5 days as the result of metabolism of the compound. An EPA 

(1992d) hazard assessment stated that although di-n-octylphthalate does bioconcentrate in aquatic
DI-n-OCTYLPHTHALATE 83

5. POTENTIAL FOR HUMAN EXPOSURE

organisms, the compound is not expected to biomagnify in aquatic food chains; however, this citation

did not contain, and does not reference any studies that provide, a basis for this conclusion. In

greenhouse studies using radiolabeled di-n-octylphthalate added to soils, the compound was not

bioconcentrated by crop plants (BCF <1) (EPA 1986e). In a more recent screening study that

examined the potential of contaminants contained in sewage sludge to transfer into agricultural

products on the basis of their physical/chemical properties, di-n-octylphthalate was judged to have a

high potential to adsorb to soil, sludge solids, and plant root surfaces, and a low potential for leaching,

uptake and translocation by plants, and transfer to animal tissues by foliage ingestion (Wild and Jones

1992).

5.3.2 Transformation and Degradation

5.3.2.1 Air

The most important transformation process for di-n-octylphthalate present in the atmosphere as an

aerosol is reaction with photochemically produced hydroxyl radicals. The half-life for this reaction has

been estimated to be 4.5-44.8 hours (Howard et al. 1991). Actual atmospheric half-lives may be

longer since phthalate esters sorbed to wind-entrained particulates may have long atmospheric

residence times (Vista Chemical 1992). Direct photolysis in the atmosphere is not expected to be an

important process (EPA 1993a; HSDB 1995).

5.3.2.2 Water

Phthalate esters undergo a step-wise alkaline hydrolysis to monoesters and then to dicarboxylic acids.

As a result of the relatively slow rates of this reaction at pH 6-9 and the low water solubility of di-noctylphthalate, chemical hydrolysis of the compound is not an environmentally important

transformation process (EPA 1992a). Hydrolytic half-lives at 25°C and pH 7 and 9 have been

estimated to be 107 and 7 years, respectively (Howard et al. 1991).

Biodegradation is the primary process by which phthalate esters are removed from surface waters;

rates are strongly dependent on acclimation of microbial communities (EPA 1992a, 1992~). Wolfe et

al. (1980) predicted that biodegradation would be the most important mechanism by which di-noctylphthalate would be removed from eutrophic lakes. In static culture flask biodegradation screening
DI-n-OCTYLPHTHALATE 84

5. POTENTIAL FOR HUMAN EXPOSURE

tests, about 93-94% of di-n-octylphthalate was metabolized after 3 weeks only after serial subculturing

of acclimated microorganisms (Tabak et al. 1981). Enzymatic hydrolysis is the mechanism used by

microbes in the aerobic biotransformation of di-n-octylphthalate. The ester is hydrolyzed to soluble

intermediates, presumably via a pathway producing a phthalic acid monoester (EPA 1993a); however,

data on the identity of biodegradation products were not available. Aerobic biodegradation half-lives

range from 1 to 4 weeks in surface waters and from 2 weeks to 1 year in groundwater (Howard et al.

1991). Biodegradation under anaerobic conditions occurs at a slower rate (EPA 1993a); it has been

predicted that di-n-octylphthalate will accumulate in natural sediments because it is persistent under

anaerobic conditions (EPA 1992d). For example, in anaerobic digester studies using diluted and

undiluted sewage treatment plant sludge, between 40% and 75% of di-n-octylphthalate remained

undegraded after a 10-week incubation period (Shelton et al. 1984). Anaerobic half-lives for aquatic

systems have been predicted to range from 6 months to 1 year (Howard et al. 1991).

Di-n-octylphthalate may also undergo photolysis in surface waters as a result of its absorption of

electromagnetic radiation at wavelengths less than 290 nm. The estimated photolytic half-life of the

compound in surface water is 144 days (EPA 1992a). Photolysis was predicted to be the most

important removal mechanism after volatilization for di-n-octylphthalate losses from oligotrophic lakes

(Wolfe et al. 1980).

5.3.2.3 Sediment and Soil

As discussed above, aerobic biotransformation is expected to be the most important process in the

removal of di-n-octylphthalate from soils; anaerobic biodegradation occurs in sediments (EPA 1992a).

However, because of its persistence under anaerobic conditions, di-n-octylphthalate is expected to

accumulate in sediments (EPA 1992d). Di-n-octylphthalate has been reported to undergo

biodegradation by a variety of acclimated soil microorganisms (HSDB 1995; Mathur 1974b); however,

data on the identity of biodegradation products were not located.

5.4 LEVELS MONITORED OR ESTIMATED IN THE ENVIRONMENT

As previously discussed, considerable confusion exists in the literature about the monitoring data

available for di-n-octylphthalate and di(2-ethylhexyl)phthalate. Only monitoring data that clearly
DI-n-OCTYLPHTHALATE 85

5. POTENTIAL FOR HUMAN EXPOSURE

concerned di-n-octylphthalate were included in this section of the profile; data from ambiguous studies

were not included.

5.4.1 Air

Di-n-octylphthalate was detected in five of seven ambient air and six of seven rainwater samples

collected during rain events that occurred in February through April 1984 in Portland, Oregon. Di-noctylphthalate concentrations ranged from 2.6 to 20 ng/L in rain samples and from 0.06 to 0.94 ng/m3

in air samples (Ligocki et al 1985).

5.4.2 Water

Di-n-octylphthalate was detected in 4% of the urban runoff samples collected from a total of 15 cities.

Di-n-octylphthalate was detected at three cities at concentrations of 0.4-l μg/L (Cole et al. 1984). The

compound was found in water samples collected at four locations along the entire length of the

Mississippi River at concentrations of 24-310 ng/L (DeLeon et al. 1986). At the Butler Mine Tunnel

NPL Site located in Pittston, Pennsylvania, di-n-octylphthalate was detected in on-site oil/groundwater

samples at concentrations of ll0-792,000 ppb (ATSDR 1989b). Di-n-octylphthalate was detected at a

concentration of 1 ppb in a water sample collected from the discharge pond of a phthalate ester plant

located on the Chester River in Maryland (Peterson and Freeman 1984). Di-n-octylphthalate was

found at 0.001-0.02 ppm in water samples taken from a river that received industrial waste water from

a specialty chemical manufacturing plant (Jungclaus et al. 1978).

Estimates of di-n-octylphthalate concentrations in receiving waters located downstream from two plants

reporting releases of the compound to the TRI have been developed by EPA (1992c). Mean flow

concentrations of about 3-9 μg/L and 7-year Ql0 low-flow concentrations of about 90-390 μg/L were

estimated for the surface waters receiving effluent from the on-site treatment facility used at one plant

and the publicly owned treatment facility that handles the effluent from the other plant.

Concentrations of di-n-octylphthalate in drinking water utility influents have been estimated to be less

than 0.5 ppb (EPA 1992c).
DI-n-OCTYLPHTHALATE 86 

5. POTENETIAL FOR HUMAN EXPOSURE 

5.4.3 Sediment and Soil 

In the sediment of a discharge pond of a phthalate ester plant located on the Chester River in 

Maryland, di-n-octylphthalate was detected at a concentration of 12,000 ppb. In sediment samples 

from the Chester River taken 2 km and 8 km downstream from the plant, the compound was found at 

concentrations of 62 and <5 ppb, respectively (Peterson and Freeman 1984). In the sediment of a 

river that received industrial waste water from a specialty chemical manufacturing plant, di-noctylphthalate was detected at concentrations ranging from 1.5 to 25 ppm (Jungclaus et al. 1978). At 

the Dixie Caverns Landfill NPL site located in Salem, Virginia, di-n-octylphthalate was detected on-site at 

a concentration of 80 ppm (ATSDR 1988); however, the media in which this concentration was 

detected was not specified. Off-site sediment samples collected at the Revere Chemical Company 

NPL site located in Revere, Pennsylvania, were found to contain 2,300 ppb di-n-octylphthalate 

(ATSDR 1989c). 

EPA (1992c) developed estimates of di-n-octylphthalate concentrations in the sediments of surface 

waters located downstream from two plants reporting releases of the compound to the TRI. The 

surface waters received effluents from an on-site treatment facility and a publicly owned treatment 

facility. Steady-state sediment concentrations were estimated to exceed 10 mg/kg and possibly 

>50 mg/kg downstream from the two facilities. 

5.4.4 Other Environmental Media 

Di-n-octylphthalate is produced as a decomposition product of the pesticide dinocap (HSDB 1995). 

5.5 GENERAL POPULATION AND OCCUPATIONAL EXPOSURE 

Humans are expected to be exposed to di-n-octylphthalate mainly in the workplace (HSDB 1994). 

The National Occupational Exposure Survey (NOES), conducted between 1981 and 1983; estimated 

that 10,393 workers (including 1,434 women) in 1,177 facilities were exposed to di-n-octylphthalate in 

the workplace in 1980 (NIOSH 1993). 

Exposure of the general population to di-n-octylphthalate may occur through ingestion of foods 

contaminated by leaching of the compound from plastic containers, transfusions of blood or other
DI-n-OCTYLPHTHALATE 87

5. POTENTIAL FOR HUMAN EXPOSURE

fluids through medical tubing, ingestion of aquatic organisms that have bioconcentrated the compound,

and consumption of contaminated drinking water (EPA 1992c; HSDB 1995). An additional potential

source of human exposure is contact with contaminated media at hazardous waste sites. For example,

di-n-octylphthalate has been detected in on-site sediment and groundwater samples and off-site

sediment samples collected at NPL hazardous waste sites. The human exposure pathways of concern

at these sites include ingestion of contaminated groundwater and sediment (ATSDR 1988, 1989b,

1989c). Since data are not available on the dermal absorption of di-n-octylphthalate, it is not known

whether dermal contact with di-n-octylphthalate at hazardous waste sites would represent an exposure

pathway of concern.

In an early report of the 1982 annual results of the National Human Adipose Tissue Survey (NHATS),

a compound identified as di-n-octylphthalate was reportedly detected in 31% of the composite human

adipose tissue samples taken in the various regions of the United States that year. Concentrations in

lipid ranged from below the level of detection (9 ng/sample) to a maximum of 850 ng/g (EPA 1986d).

However, a later report of the 1982 results stated that the chemical detected was not di-n-octylphthalate,

but was actually diethylhexyl phthalate (EPA 1989b).

5.6 POPULATIONS WITH POTENTIALLY HIGH EXPOSURES

Patients receiving regular dialysis on a kidney machine or receiving blood transfusions may be the

populations with the highest potential exposure to di-n-octylphthalate. Workers in industries that

produce or use plastics, especially materials processed at high temperatures, are also expected to have

potentially high exposure to di-n-octylphthalate especially via inhalation of the volatilized plasticizer.

Members of the general population living in the vicinity of industrial facilities that manufacture or

process the compound or plastic materials containing the compound, as well as individuals living near

hazardous waste sites known to be contaminated with di-n-octylphthalate, are also expected to have

potentially high exposures through contact with contaminated environmental media (HSDB 1995).

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 di-n-octylphthalate is available. Where adequate
DI-n-OCTYLPHTHALATE 88 

5. POTENETIAL FOR HUMAN EXPOSURE 

information is not available, ATSDR, in conjunction with the NTP, is required to assure the initiation 

of a program of research designed to determine the health effects (and techniques for developing 

methods to determine such health effects) of di-n-octylphthalate. 

The following categories of possible data needs have been identified by a joint team of scientists from 

ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that if met would 

reduce the uncertainties of human health assessment. This definition should not be interpreted to mean 

that all data needs discussed in this section must be filled. In the future, the identified data needs will 

be evaluated and prioritized, and a substance-specific research agenda will be proposed. 

5.7.1 Identification of Data Needs 

Physical and Chemical Properties. The physical and chemical properties of di-n-octylphthalate are 

sufficiently well defined to allow assessments of the environmental fate of the 

compound to be made. Therefore, no additional information is needed a this time. 

Production, Import/Export, Use, Release, and Disposal. Because of the general 

confusion in the literature about the nomenclature for octylphthalate esters, historical information about 

the production and import/export of di-n-octylphthalate is not readily available. These values generally 

must be estimated as a percentage of di(2-ethylhexyl)phthalate production or import/export. The 

compound is used principally as a plasticizer additive to plastics and PVC resins. It is also used as a 

dye carrier in plastics production and as a chemical intermediate (EPA 1993a; HSDB 1995; Mannsville 

Chemical Products Corporation 1989; Sittig 1991). Limited information is available about releases of 

di-n-octylphthalate to environmental media. Even the TRI data, which comprise the most current 

information available, contain errors as a result of the nomenclature confusion (EPA 1993a; Vista 

Chemical 1992). Data are available about the disposal and regulatory status of the compound (see 

Chapters 4 and 7). More information on the production and releases of di-n-octylphthalate is needed 

to estimate potential exposure to the compound. 

According to the Emergency Planning and Community Right-to-Know Act of 1986, 42 U.S.C. Section 

11023, industries are required to submit substance release and off-site transfer information to the EPA. 

The Toxics Release Inventory (TRI), which contains this information for 1993, became available in 

May of 1995. This database will be updated yearly and should provide a list of industrial production
DI-n-OCTYLPHTHALATE 89 

5. POTENETIAL FOR HUMAN EXPOSURE 

facilities and emissions. However, di-n-octylphthalate was withdrawn from the TRI effective in 1993 

(EPA 1995h). 

Environmental Fate. Di-n-octylphthalate partitions primarily to soils and sediment upon release to 

the environment. The compound is expected to be strongly sorbed to soil and sediment particulates; 

therefore, it should have limited mobility (EPA 1979, 1992c). Biodegradation half-lives of l-4 weeks 

have been estimated for aerobic surface waters and soils. Biodegradation also takes place in 

sediments; half-lives under anaerobic conditions have been estimated to range from of 6 months to 

1 year (Howard et al. 1991). The compound may also undergo photolysis in surface waters (estimated 

half-life of 144 days) and photooxidation in the atmosphere (estimated half-life of about 5-45 hours) 

(Howard et al. 1991). Di-n-octylphthalate may persist in sediments as a result of its limited rate of 

biotransformation and preferential partitioning to this medium. 

However, although degradation is known to occur under both aerobic and anaerobic conditions, data 

are not available on the identity of degradation products. Because the limited studies on the 

mechanisms of injury from di-n-octylphthalate suggest that mono-n-octylphthalate is the proximate 

toxicant, it is important to know whether the reduction of di-n-octylphthalate is coupled with the 

accumulation of mono-n-octylphthalate. The environmental fate of di-n-octylphthalate and its 

metabolites is not sufficiently understood to allow assessments of its exposure potential to be made. 

Additional data are needed on the identify and fate of degradation products of di-n-octylphthalate. No 

additional information is needed about the transport and partitioning of the compound at this time. 

Bioavailability from Environmental Media. No information was found regarding the 

absorption of di-n-octylphthalate by humans or laboratory animals following inhalation or dermal 

exposures. No information is available about absorption following oral exposure in humans. However, 

indirect evidence from animal studies suggests that the compound is readily absorbed by this route (Albro 

and Moore 1974; Oishi 1990). Additional information is needed on the absorption of di-n-octylphthalate 

as a result of inhalation of contaminated air, ingestion of contaminated food and water, and dermal 

contact with contaminated soils and sediments.
DI-n-OCTYLPHTHALATE 90 

5. POTENETIAL FOR HUMAN EXPOSURE 

Food Chain Bioaccumulation. Di-n-octylphthalate bioconcentrates in aquatic organisms. 

However, as a result of metabolism of the compound, biomagnification in aquatic food chains does not 

occur (EPA 1992d). It appears that the compound is not bioconcentrated by terrestrial plants or 

animals or biomagnified in terrestrial food chains (EPA 1986e; Wild and Jones 1992). However, the 

Wild and Jones (1992) study is limited to mathematical modeling results. Thus, only limited data are 

available regarding the bioaccumulation and biomagnification of di-n-octylphthalate, and the potential 

for human exposure resulting from the bioaccumulation of the compound is not well understood. 

Therefore, additional data are needed to validate the Wild and Jones (1992) model. Also, an 

estimation of animal uptake from soil ingestion is needed to support this study. 

Exposure Levels in Environmental Media. Reliable monitoring data for the levels of di-noctylphthalate in contaminated media at hazardous waste sites are needed so that the information 

obtained on levels of di-n-octylphthalate in the environment can be used in combination with the 

known body burden of di-n-octylphthalate to assess the potential risk of adverse health effects in 

populations living in the vicinity of hazardous waste sites. Di-n-octylphthalate has been detected in 

ambient air, rain, surface water, groundwater, and sediment. However, as a result of the confusion 

about the nomenclature for octylphthalate esters, much of the historical monitoring data available 

actually pertain to the branched isomer, di(2-ethylhexyl)phthalate (Vista Chemical 1992). Therefore, 

little current information specific to the n-octyl isomer is available regarding concentrations of the 

compound in foods, drinking water, and environmental media, particularly with respect to media at 

hazardous waste sites. The lack of monitoring data precludes the estimation of human exposure via 

intake of or contact with contaminated media. 

Exposure Levels in Humans. This information is necessary for assessing the need to conduct 

health studies on these populations. Di-n-octylphthalate has historically been reported to have been 

found in human adipose tissue (EPA 1986d). However, more recent information indicates that the 

compound detected was actually the branched di(Zethylhexy1) isomer (EPA 1989b). Additional 

information on the concentrations of di-n-octylphthalate in human tissues and fluids, parficularly for 

populations living near hazardous waste sites, is needed to assess potential human exposure to the 

compound.
DI-n-OCTYLPHTHALATE 91 

5. POTENETIAL FOR HUMAN EXPOSURE 

Exposure Registries. No exposure registries for di-n-octylphthalate were located. This substance 

is not currently one of the compounds for which a subregistry has been established in the National 

Exposure Registry. The substance will be considered in the future when chemical selection is made 

for subregistries to be established. The information that is amassed in the National Exposure Registry 

facilitates the epidemiological research needed to assess adverse health outcomes that may be related 

to exposure to this substance. 

5.7.2 On-going Studies 

No information was found in the available literature concerning on-going studies dealing with the 

environmental fate or human exposure potential of di-n-octylphthalate.

DI-n-OCTYLPHTHALATE 93 

6. ANALYTICAL METHODS 

The purpose of this chapter is to describe the analytical methods that are available for detecting, and/or 

measuring, and/or monitoring di-n-octylphthalate, its metabolites, and other biomarkers of exposure 

and effect to di-n-octylphthalate. The intent is not to provide an exhaustive list of analytical methods. 

Rather, the intention is to identify well-established methods that are used as the standard methods of 

analysis. Many of the analytical methods used for environmental samples are the methods approved 

by federal agencies and organizations such as EPA and the National Institute for Occupational Safety 

and Health (NIOSH). Other methods presented in this chapter are those that are approved by groups 

such as the Association of Official Analytical Chemists (AOAC) and the American Public Health 

Association (APHA). Additionally; analytical methods are included that modify previously used 

methods to obtain lower detection limits, and/or to improve accuracy and precision. 

6.1 BIOLOGICAL MATERIALS 

Very limited data were found regarding the measurement of di-n-octylphthalate and its metabolites in 

biological fluids. Table 6-l summarizes the methods that are available. Analytical methods were 

located for measuring di-n-octylphthalate and its metabolites in urine, blood, and tissues (Albro and 

Moore 1974; Lanina et al. 1992; Oishi 1990). These methods include gas chromatography (GC) 

combined with mass spectrometry (MS) and high-performance liquid chromatography (HPLC) 

combined with an ultraviolet detector (UV). No comparisons can be made between methods since no 

data were given regarding sensitivity, recovery, or precision. 

6.2 ENVIRONMENTAL SAMPLES 

Table 6-2 summarizes the various methods available for measuring di-n-octylphthalate in 

environmental samples. GC/MS and GC combined with electron capture detection (ECD’) can be used 

to measure di-n-octylphthalate in water, waste water, groundwater, soil, and solid waste (APHA 1992; 

Eichelberger et al. 1983; EPA 1981, 1986a, 1986b, 1986c, 1990b; Furtmann 1994; Lopez-Avila et al. 

1989; Ritsema et al. 1989; Valkenburg et al. 1989).





DI-n-OCTYLPHTHALATE 99 

6. ANALYTICAL METHODS 

Generally, sample preparation procedures involved extraction with methylene chloride at pH <2 and 

pH >11. The removal of interferents such as organochlorine pesticides and polychlorinated biphenyls 

has been approached though the addition of a clean-up step using Florisil columns (EPA 1981) and 

more recently solid-phase extraction alone with Florisil or other solid-phase matrices have been used 

(Furtmann 1994; Lopez-Avila et al. 1989; Ritsema et al. 1989). Sensitivity is in the low-ppb (μg/L) 

range for water samples using GC/MS (APHA 1992; Eichelberger et al. 1983; EPA 1986a, 1986b, 

1990b; Furtmann 1994; Valkenburg et al. 1989). GC/MS provided slightly better sensitivity than did 

GC/ECD. For water samples, recoveries are good for GC/MS and GC/ECD (Eichelberger et al. 1983; 

EPA 1981; Furtmann 1994; Ritsema et al. 1989; Valkenburg et al. 1989). Precision was adequate 

(<13-21% relative standard deviation [RSD]) (Eichelberger et al. 1983; Valkenburg et al. 1989). For 

soil and solid waste samples, sensitivity was in the ppm (μg/L) range using GC/MS and GC/ECD. For 

the standard analytical methods approved by EPA (Test Methods 1625, 8060, 8250, and 8270) and 

APHA, recovery and precision varied greatly for both water and soil samples (APHA 1992; EPA 

1986a, 1986b, 1986c, 1990b). 

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 di-n-octylphthalate is available. Where adequate 

information is not available, ATSDR, in conjunction with the NTP, is required to assure the initiation 

of a program of research designed to determine the health effects (and techniques for developing 

methods to determine such health effects) of di-n-octylphthalate. 

The following categories of possible data needs have been identified by a joint team of scientists from 

ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that if met would 

reduce the uncertainties of human health assessment. This definition should not be interpreted to mean 

that all data needs discussed in this section must be filled. In the future, the identified data needs will 

be evaluated and prioritized, and a substance-specific research agenda will be proposed.
DI-n-OCTYLPHTHALATE 100 

6. ANALYTICAL METHODS 

6.3.1 Identification of Data Needs 

Methods for Determining Biomarkers of Exposure and Effect 

Exposure. Methods for Determining Parent Compounds and Degradation Products in Environmental 

Media.Methods are available for measuring di-n-octylphthalate and/or its metabolites (primarily the 

corresponding phthalate monoesters) in urine, blood, and tissues (Albro and Moore 1974; Lanina et al. 

1992; Oishi 1990); however, the data are very limited. More information on the accuracy, precision, 

and sensitivity of these methods is needed to evaluate the value of using the levels of di-n-octylphthalate 

and its metabolites (particularly in urine) as indicators of exposure. The lack of data for 

these methods makes it difficult to assess whether these methods are sufficiently sensitive to measure 

levels at which health effects might occur, as well as background levels in the population. 

Effect. No biomarkers of effects caused by di-n-octylphthalate have been identified in humans or 

animals, 

Methods for Determining Parent Compounds and Degradation Products in 

Environmental Media. Methods exist for measuring di-n-octylphthalate in water, groundwater, 

waste water, soil, and solid waste (APHA 1992; Eichelberger et al. 1983; EPA 1981, 1986a, 1986b, 

1986c, 1990b; Furtmann 1994; Lopez-Avila et al. 1989; Ritsema et al. 1989; Valkenburg et al. 1989); 

however, the database is limited. More information on the accuracy and precision of these methods is 

needed to accurately compare them. No data were located for measuring di-n-octylphthalate in air. 

The lack of data on background levels in the environment, as well as levels at which health effects 

might occur, prevents an evaluation of whether the methods are sensitive enough. Research 

investigating the relationship between environmental levels and observed health effects could increase 

confidence in existing methods and indicate where improvements are needed. Analytical methods are 

needed for determining degradation products in all environmental media. 

6.3.2 On-going Studies 

No on-going analytical methods studies were located.
DI-n-OCTYLPHTHALATE 101 

7. REGULATIONS AND ADVISORIES 

The international, national, and state regulations and guidelines regarding di-n-octylphthalate in air, 

water, and other media are summarized in Table 7-l. 

ATSDR has derived an MRL of 3 mg/kg/day for acute-duration oral exposure in humans; this MRL is 

based on a LOAEL of 1,000 mg/kg/day in rats (Lake et al. 1986). 

ATSDR has derived an MRL of 0.4 mg/kg/day for intermediate-duration oral exposure in humans; this 

MRL is based on a NOAEL of 40.8 mg/kg/day in rats (Poon et al. 1995). 

An oral reference dose (RfD) is currently pending by EPA (IRIS 1995). 

Neither EPA or IARC has classified di-n-octylphthalate as to its carcinogenicity.

DI-n-OCTYLPHTHALATE 103 

8. REFERENCES 

Al-Badry MS, Knowles CO. 1980. Phthalate-organophosphate interactions: Toxicity, penetration, and 

metabolism studies with house flies. Arch Environ Contam Toxicol 9:147-161. 

Alaimo LH, Hartman TG, Rosen RT, et al. 1990. Nonpriority analysis of the wastewater streams of 

four dye manufacturing facilities. Res J WPCF 62:665-669. 

*Albro PW, Moore B. 1974. Identification of the metabolites of simple phthalate diesters in rat urine. 

J Chromatogr 94:209-218. 

*Albro PW, Thomas R, Fishbein L. 1973. Metabolism of diethylhexyl phthalate by rats: Isolation and 

characterization of the urinary metabolites. J Chromotogr 76:321-330. 

*APHA. 1992. American Public Health Association. Standard methods for the examination of water 

and wastewater. 18th Edition. Washington, DC: American Public Health Association. 

Armstrong VC, Newhook RC. 1992. Assessing the health risks of priority substances under the 

Canadian environmental protection act. Regulatory Toxicol Pharmacol 15:111-121. 

*ATSDR. 1988. Health assessment for Dixie Caverns Landfill, Salem, Virginia. Agency for Toxic 

Substances and Disease Registry, Atlanta, GA. PB90-144478. 

ATSDR. 1989a. Decision guide for identifying substance-specific data needs related to toxicological 

profiles. Agency for Toxic Substances and Disease Registry. Federal Register 54:37618-37634. 

*ATSDR. 1989b. Health assessment for Butler Mine Tunnel, Pittson, Pennsylvania. Agency for Toxic 

Substances and Disease Registry, Atlanta, GA. PB90-143603. 

*ATSDR. 1989c. Health assessment for Revere Chemical Company National Priorities List (NPL) site, 

Revere Bucks County, Pennsylvania. Agency for Toxic Substances and Disease Registry, Atlanta, GA. 

PB90-144759. 

*ATSDR. 1992. Toxicological profile for di(2-ethylhexyl)phthalate. Agency for Toxic Substances and 

Disease Registry, Atlanta, GA. 

*Barnes DG, Dourson M. 1988. Reference dose (RfD): Description and use in health risk 

assessments. Regul Toxicol Pharmacol 8:471-486. -. 

Bennett GF. 1989. Impact of toxic chemicals on local wastewater treatment plant and the environment. 

Environ Geol Water Sci 3:201-212. 

_____________________ 

*Cited in text
DI-n-OCTYLPHTHALATE 104

8. REFERENCES

Bernstein ME. 1984. Agents affecting the male reproductive system: Effects of structure on activity.

Drug Metab Rev 15:941-996.

Bower RK, Haberman S, Minton PD. 1970. Teratogenic effects in the chick embryo caused by esters

of phthalic acid. J Pharmacol Exp Ther 171:314-324.

*Brodsky J, Andersson JT, Ballschmiter K. 1986. Chemical degradation of xenobiotics: II.

Simulation of the biotic transformation of bis(Zethylhexy1) phthalate and dioctylphthalate by abiotic

means. Chemosphere 15:139-147.

Brunetti G, Moscato G. 1984. Bronchial asthma due to occupational exposure to DOP. Med Lav

75:120-124.

Carmignani GM, Bennett JP. 1976. Leaching of plastics used in closed aquaculture systems.

Aquaculture 7 :89-9 1.

*Carter JH, Richmond RE, Carter HW, et al. 1992. Quantitative image cytometry of hepatocytes

expressing gamma-glutamyl transpeptidase and glutathione S-transferase in diethylnitrosamine-initiated

rats treated with phenobarbital and/or phthalate esters. J Histochem Cytochem 40: 1105-l 115.

*Clayton GD, Clayton FE, eds. 1981. Patty’s industrial hygiene and toxciology. Volume 2A:

Toxicology. 3rd revised ed. New York, NY: John Wiley and Sons, 2343-2351.

*Cole RH, Frederick RE, Healy RP, et al. 1984. Preliminary findings of the priority pollutant

monitoring project of the Nationwide Urban Runoff Program. Journal WPCF 56(7):898-908.

Comu MC, Lhuguenot JC, Brady AM, et al. 1992. Identification of the proximate peroxisome

proliferators derived from di(ethylhexy1) adipate and species differences in response. Biochem

Pharmacol 43:2129-2134.

*DeAngelo AB, Garrett CT, Manolukas LA, et al. 1986. Di-n-octyl phthalate (DOP), a relatively

ineffective peroxisome inducing straight chain isomer of the environmental contaminant di(2-

ethylhexyl)phthalate (DEHP), enhances the development of putative preneoplastic lesions in rat liver.

Toxicology 41:279-288.

*DeLeon IR, Byrne CJ, Peuler EA, et al. 1986. Trace organic and heavy metal pollutants in the

Mississippi River. Chemosphere 15(6):795-805.

Dillingham EO, Autian J. 1973. Teratogenicity, mutagenicity, and cellular toxicity of phthalate esters.

Environ Health Perspect 81-89.

Dirven HA, Theuws JL, Jongeneelen FJ, et al. 1991. Non-mutagenicity of 4 metabolites of di(2-

ethylhexyl)phthalate (DEHP) and 3 structurally related derivatives of di(2-ethylhexyl)adipate (DEHA) in

the salmonella mutagenicity assay. Mutat Res 260:121-130.

*Dogra RK, Chandra K, Chandra S, et al. 1989. Di-octyl phthalate induced altered host resistance:

Viral and protozal models in mice. Industrial Health 27:83-87.
DI-n-OCTYLPHTHALATE 105 

8. REFERENCES 

*Dogra RK, Khanna S, Nagale SL, et al. 1985. Effect of dioctyl phthalate on immune system of rat. 

Indian J Exp Bio 23:315-319. 

*Dogra RK, Khanna S, Shukla L, et al. 1987. Modification of the immune response in rats by di-octyl 

phthalate. Industrial Health 25:97-101. 

*Eastman Kodak Company. 1978. Toxicity and health hazard summary. Rochester, NY: EPA/OTS 

Document No. 878214345. 

*Eichelberger JW, Kerns EH, Okynyk P, et al. 1983. Precision and accuracy in the determination of 

organics in water by fused silica capillary column gas chromatography/mass spectrometry and packed 

column gas chromatography/mass spectrometry. Anal Chem 55:1471-1479. 

*EPA. 1979. Water-related environmental fate of 129 priority pollutants. Volume II. Washington, 

DC: Monitoring and Data Support Division, U.S. Environmental Protection Agency. EPA Report No. 

440/4-79-029b, 94: l-28. 

EPA. 1980. U.S. Environmental Protection Agency. Federal Register 45:33132-33133. 

*EPA. 1981. Determination of phthalates in industrial and municipal waste waters. Technical report. 

Cincinnati, OH: U.S. Environmental Protection Agency. EPA-600/4-81-063. 

EPA. 1982. Aquatic fate process data for organic priority pollutants. Washington, DC: Monitoring 

and Data Support Division, Office of Water Regulations and Standards, U.S. Environmental Protection 

Agency. EPA Report No. 440/4-81-014. 

EPA. 1985. U.S. Environmental Protection Agency. 40 CFR 122.1, 122 Appendix D. 

*EPA. 1986a. Test methods for evaluating solid waste (SW-846). Volume IC: Laboratory manual 

physical/chemical methods. Method 8270. Washington, DC: U.S. Environmental Protection Agency, 

Office of Solid Waste and Emergency Response. 

*EPA. 1986b. Test methods for evaluating solid waste (SW-846). Volume IC: Laboratory manual 

physical/chemical methods. Method 8250. Washington, DC: U.S. Environmental Protection Agency, 

Office of Solid Waste and Emergency Response. 

*EPA. 1986c. Test methods for evaluating solid waste (SW-846). Volume IC: Laboratory manual 

physical/chemical methods. Method 8060. Washington, DC: U.S. Environmental Protection Agency, 

Office of Solid Waste and Emergency Response. 

*EPA. 1986d. Broad scan analysis of the FY82 national human adipose tissue survey specimens. 

Washington, DC: U.S. Environmental Protection Agency, Office of Toxic Substances. 

*EPA. 1986e. Toxic and priority organics in municipal sludge land treatment systems. Cincinnati, 

OH: Washington, DC: U.S. Environmental Protection Agency, Office of Research and Development, 

Wastewater Engineering Research Laboratory. EPA/600/2-86/010. 

*EPA. 1987a. Health and environmental effects profile for phthalic acid esters (PAEs). Cincinnati, 

OH: U.S. Environmental Protection Agency, Office of Research and Development. PB89-120158.
DI-n-OCTYLPHTHALATE 106

8. REFERENCES 

*EPA. 1987b. Health effects assessment for selected phthalic acid esters. Cincinnati, OH: U.S. 

Environmental Protection Agency, Office of Research and Development. PB88-178934. 

EPA. 1987c. U.S. Environmental Protection Agency. Part II. Federal Register 52:25942-25953. 

EPA. 1987d. U.S. Environmental Protection Agency. Part II. Federal Register 52:13370, 13379- 

13381. 

EPA. 1988a. U.S. Environmental Protection Agency. 40 CFR 401.16, 403, APPENDIX B 

EPA. 1988b. U.S. Environmental Protection Agency. Part II. Federal Register 53:4500-4507. 

EPA. 1988c. U.S. Environmental Protection Agency. Part V. Federal Register 53:38642-38654. 

EPA. 1989a. U.S. Environmental Protection Agency final report. NHATS broad scan analysis: 

Population estimates from fiscal year 1982 specimens. Washington, DC: U.S. Environmental 

Protection Agency, Office of Pesticides and Toxic Substances. EPA 560/5-90-001. 

*EPA. 1989b. U.S. Environmental Protection Agency. Part V. Federal Register 54:33418-33419, 

33457. 

*EPA. 1990a. Interim methods for development of inhalation reference doses. Washington, DC: U.S. 

Environmental Protection Agency. EPA/600/8-90/066A. 

*EPA. 1990b. Method 1625 revision B. Semivolatile organic compounds by isotope dilution GCYMS. 

U.S. Environmental Protection Agency. Code of Federal Regulations. 40 CFR Ch.l:516-536. 

EPA. 1990c. U.S. Environmental Protection Agency. Part II. Federal Register 55:22520-22537, 

22593, 22712. 

EPA. 1991a. U.S. Environmental Protection Agency. 40 CFR 261, Appendix VIII. 

EPA. 1991b. U.S. Environmental Protection Agency. Part II. Federal Register 55:3864-3910. 

*EPA. 1992a. Chemistry report on di-n-octylphthalate. Washington, DC: Industrial Chemistry 

Branch, Economics and Technology Division, Office of Toxic Substances, U.S. Environmental 

Protection Agency. 

*EPA. 1992b. Heast Table 1: Subchronic and chronic toxicity (other than carcinogenicity). Health 

Effects Assessment Summary Tables. U.S. Environmental Protection Agency. NTIS Order No. PB92- 

921199. 

*EPA. 1992c. Di-n-octylphthalate exposure report for delisting petition. U.S. Environmental Protection 

Agency, Washington, DC. Memorandum from Annett Nold, Exposure Assessment Branch, Exposure 

Evaluation Division, Office of Pollution Prevention and Toxics to Ken Mitchell, Toxics Release 

Inventory Management Staff, Economics and Technology Division, Office of Pollution Prevention and 

Toxics. September 21, 1992.
DI-n-OCTYLPHTHALATE 107 

8. REFERENCES 

*EPA. 1992d. Transmittal of hazard assessment of di-n-octyl phthalate. Washington, DC: U.S. 

Environmental Protection Agency, Washington, DC. Memorandum from Lorraine Randecker, Chemical 

Review and Evaluation Branch, Health and Environmental Review Division, Office of Pollution 

Prevention and Toxics to Ken Mitchell, Toxics Release Inventory Management Staff, Economics and 

Technology Division, Office of Pollution Prevention and Toxics. July 15, 1992. 

*EPA. 1993a. Di-n-octyl phthalate; toxic chemical release reporting; community right-to-know. U.S. 

Environmental Protection Agency. Federal Register 58(8):4133-4137. 

*EPA. 1993b. Di-n-octyl phthalate; toxic chemical release reporting; community right-to-know. U.S. 

Environmental Protection Agency. Federal Register 58(191):51785-51786. 

EPA. 1993c. U.S. Environmental Protection Agency. Code of Federal Regulations 40 CFR 372 

Subpart D. 

*EPA. 1995a. U.S. Environmental Protection Agency. Code of Federal Regulations 40 CFR 712.30. 

*EPA. 1995b. U.S. Environmental Protection Agency. Code of Federal Regulations 40 CFR 716.120. 

*EPA. 1995c. U.S. Environmental Protection Agency. Code of Federal Regulations 40 CFR 122 

Appendix D. 

*EPA. 1995d. U.S. Environmental Protection Agency. Code of Federal Regulations 40 CFR 403 

Appendix B . 

*EPA. 1995e. U.S. Environmental Protection Agency. Code of Federal Regulations 40 CFR 268. 

*EPA. 1995f. U.S. Environmental Protection Agency. Code of Federal Regulations 40 CFR 261 

Appendix VIII. 

*EPA. 1995g. U.S. Environmental Protection Agency. Code of Federal Regulations 40 CFR 264 

Appendix IX. 

*EPA. 1995h. U.S. Environmental Protection Agency. Code of Federal Regulations 40 CFR 372. 

*EPA. 19951. U.S. Environmental Protection Agency. Code of Federal Regulations 40 CFR 175.105. 

FDA. 1977. Food and Drug Administration, Health and Human Services. 21 CFR 175.105. 

FDA. 1992. Food and Drug Administration, Health and Human Services. 21 CFR 177.2600. 

*FDA. 1995a. U.S. Food and Drug Administration. Code of Federal Regulations 21 CI% 175.105. 

*FDA. 1995b. U.S. Food and Drug Administration. Code of Federal Regulations 21 CFR 177.2600. 

Ferrario JB, DeLeon IR, Tracy RE. 1985. Evidence for toxic anthropogenic chemicals in human 

thrombogenic coronary plaques. Arch Environ Contam Toxicol 14:529-534.
DI-n-OCTYLPHTHALATE 108 

8. REFERENCES 

*Florin I, Rutberg L, Curvall M, et al. 1980. Screening of tobacco smoke constituents for mutagenicity 

using the Ames test. Toxicology 18219-232. 

*Foster PM, Thomas LV, Cook MW, et al. 1980. Study of the testicular effects and changes in zinc 

excretion produced by some n-alkyl phthalates in the rat. Toxicol Appl Pharmacol 54:392-398. 

Fracasso A, Bazzato G, Kurtzman NA, et al. 1986. Plasticizers from peritoneal dialysis tubing and 

bags inhibit water transport in vitro. Clinical Res 34:729A. 

*Fredricsson B, Moeller L, Pousette A, et al. 1993. Human sperm motility is affected by plasticizers 

and diesel particle extracts. Pharmacol Toxicol (Copenhagen) 72(2):128-133. 

*Furtmann K. 1994. Phthalates in surface water-a method for routine trace level analysis. Fresenius’ 

Journal of Analytical Chemistry 348(4):291-296. 

Gangolli SD. 1982. Testicular effects of phthalate esters. Environ Health Perspect 45:77-84. 

Garrett NE, Lewtas J. 1983. Cellular toxicity in Chinese hamster ovary cell cultures: I. Analysis of 

cytotoxicity endpoints for twenty-nine priority pollutants. Environ Res 32:455-465. 

Geertz W, Dyer K, Johnson D, et al. 1974. Polyvinyl chloride biomedical products: Toxicity testing 

and identification of additives. Trans Am Sot Artif Int Organs 42-46. 

Gesler RM. 1973. Toxicology of di-2-ethylhexyl phthalate and other phthalic acid ester plasticizers. 

Environ Health Perspect 73-79. 

Giam CS, Wong MK. 1987. Plasticizers in food. J Food Protection 50:769-782. 

Goldstein DB, Feistner GJ, Faull KF, et al. 1987. Plasticizers as contaminants in commercial ethanol. 

Alcoholism: Clinical and Experimental Research 11:521-524. 

*Goodyear Tire and Rubber Company. 1981a. Mutagenicity evaluation of dopine (dioctyl phthalate), 

BASF, Tank 28. Salmonella typhimurium/microsome bioassay. Akron, OH: Goodyear Tire and 

Rubber Company Laboratory Report No. 80-l l-5. 

*Goodyear Tire and Rubber Company. 1981b. DNA Damage by dioctyl phthalate BASF, Tank 28 in 

the E. coli Pol A,- Assay. Akron, OH: Goodyear Tire and Rubber Company Laboratory Report No. 

81-42-2. 

*Gray TJ, Butterworth KR. 1980. Testicular atrophy produced by phthalate esters. Arch Toxicol 

Suppl 4:452-455. 

Guess WL, Haberman S. 1968. Toxicity profiles of vinyl and polyolefinic plastics and their additives. 

J Biomed Mater Res 2:313-335. 

*Hardin BD, Schuler RL, Burg JR, et al. 1987. Evaluation of 60 chemicals in a preliminary 

developmental toxicity test. Teratogenesis Carcinogen Mutagen 7:29-48.
DI-n-OCTYLPHTHALATE 109 

8. REFERENCES 

*HazDat. 1995. Agency for Toxic Substances and Disease Registry (ATSDR), Atlanta, GA. 

*Heindel JJ, Gulati DK, Mounce RC, et al. 1989. Reproductive toxicity of three phthalic acid esters in 

a continuous breeding protocol. Fundam Appl Toxicol 12:508-518. 

*Hinton RH, Mitchell FE, Mann A, et al. 1986. Effects of phthalic acid esters on the liver and thyroid. 

Environ Health Perspect 70:195-210. 

*Howard PH, Boethling RS, Jarvis WF, et al., eds. 1991. Handbook of environmental degradation 

rates, New York, NY: Lewis Publishers. 

*HSDB. 1995. Hazardous Substances Data Bank. National Library of Medicine, National ToxicologyInformation Program, Bethesda, MD. 

Hüls AG. 1989. Phthalic acid, di-n-octylphthalate, n-decyl ester: Bacterial mutation assay. 

Huntingdon Research Centre. Huntingdon, England. DNN 64/901441. 

*IRIS. 1995. Integrated Risk Information System. U.S. Environmental Protection Agency, 

Washington, DC. March 13, 1995. 

Johnson BT, Heitkamp MA, Jones JR. 1984. Environmental and chemical factors influencing the 

biodegradation of phthalic acid esters in freshwater sediments. Environ Pollut 8:101-l 18. 

Jones AE, Kahn RH, Groves JT, et al. 1975. Phthalate ester toxicity in human cell cultures. Toxicol 

Appl Pharmacol 31:283-289. 

*Jones HB, Garside DA, Liu R, et al. 1993. The influence of phthalate esters on Leydig cell structure 

and function in vitro and in vivo. Exp Mol Path01 58(3):179-193. 

Jones TD, Walsh PJ, Zeighami EA. 1985. Permissible concentrations of chemicals in air and water 

derived from RTECS entries: A “rash” chemical scoring system. Toxicol Ind Health 1:213-234. 

*Jungclaus GA, Lopez-Avila V, Hites RA. 1978. Organic compounds in an industrial wastewater: A 

case study of their environmental impact. Environ Sci Technol 12:88-96. 

Kalman DA. 1986. Survey analysis of volatile organics released from plastics under thermal stress, 

Am Ind Hyg Assoc J 47:270-275. 

Kandala JC, DeAngelo AB, Reddy TV, et al. 1993. Transcriptional changes in hepatic tumors of rats 

induced by di(2-ethylhexyl) phthalate and di-n-octyl phthalate. Environmental Science (Tokyo) 

2(3):147-159. 

Kaya K, Nohara K. 1987. Effect of di-n-octyl phthalate on fatty acid composition of 

phosphatidylcholine in tetrahymena. Chem Biol Interactions 64:93-101. 

Khanna S, Dogra RK, Bhatnagar MC, et al. 1989. Light and electronmicroscopic changes in testis of 

di-octyl phthalate treated rats. J Environ Biol 10:355-362.
DI-n-OCTYLPHTHALATE 110

8. REFERENCES

Klaunig JE, Ruth RJ, DeAngelo AB, et al. 1988. Inhibition of mouse hepatocyte intercellular

communication by phthalate monoesters. Cancer Lett 43:65-71.

Kluwe WM. 1982. Overview of phthalate ester pharmacokinetics in mammalian species. Environ

Health Perspect 45:3-9.

Kluwe WM, McConnell EE, Huff JE, et al. 1982. Carcinogenicity testing of phthalate esters and

related compounds by the National Toxicology Program and the National Cancer Institute. Environ

Health Perspect 45:129-133.

Kondyli E, Demertzis PG, Kontominas MG. 1992. Migration of dioctylphthalate and dioctyladipate

plasticizers from food-grade PVC films into ground-meat products. Food Chem 45:163-168.

Kool HJ, van Kreijl CF, Zoeteman CJ. 1983. Toxicology assessment of organic compounds in drinking

water. CRC Criteria1 Reviews in Environmental Control 12:307-357.

Korhonen A, Hemminki K, Vainio H. 1983a. Embryotoxic effects of phthalic acid derivatives,

phosphates and aromatic oils used in the manufacturing of rubber on three day chicken embryos. Drug

Chem Toxicol 6:191-207.

Korhonen A, Hemminki K, Vainio H. 1983b. Toxicity of rubber chemicals towards three-day chicken

embryos. Stand J Work Environ Health 9:115-119.

*Lake BG, Gray TJ, Gangolli SD. 1986. Hepatic effects of phthalate esters and related compounds - in

vivo and in vitro correlations. Environ Health Perspect 67:283-290.

*Lake BG, Phillips JC, Linnell JC, et al. 1977. The in vitro hydrolysis of some phthalate diesters by

hepatic and intestinal preparations from various species. Toxicol Appl Pharmacol 39:239-248.

*Lake BG, Rijcken WR, Gray TJ, et al. 1984. Comparative studies of the hepatic effects of di- and

mono-n-octyl phthalates, di-(Zethylhexyl) phthalate and clofibrate in the rat. Acta Pharmacol Toxicol

54:167-176.

*Lanina SY, Strakhova NM, Lappo VG. 1992. Toxicological estimate of polyvinyl chloride containers

for preparation and storage of blood, its components, preservatives and infusion solutions. Med Prog

Tech 18:19-22.

*Ligocki MP, Leuenber C, Pankow JF. 1985. Trace organic compounds in rain: II. Gas scavenging

of neutral organic compounds. Atmospheric Environ 19(10):1609-1617.

*Lopez-Avila V, Milanes J, Dodhiwala NS, et al. 1989. Cleanup of environmental sample extracts

using florisil solid-phase extraction cartridges. J Chromatogr Sci 27(5):209-220.

Mabey WR, Smith JH, Pod011 RT, et al. 1982. Aquatic fate process data for organic priority pollutants.

Report to U.S. Environmental Protection Agency, Office of Water Regulations and Standards,

Washington, DC, by SRI International, Menlo Park, CA. EPA 440/4-81-014.

Mallette FS, von Haam E. 1952. Studies on the toxicity and skin effects of compounds used in the

rubber and plastics industries. Ind Hyg Occup Med 231-236.
DI-n-OCTYLPHTHALATE 111

8. REFERENCES

*Mann AH, Price SC, Mitchell FE, et al. 1985. Comparison of the short-term effects of di(2-

ethylhexyl) phthalate, di(n-hexyl)phthalate, and di(n-octyl)phthalate in rats. Toxicol Appl Pharmacol

77:116-132.

*Mannsville Chemical Products Corporation. 1989. Dioctyl phthalate. Chemical products synopsis,

Mannsville Chemical Products Corporation, Asbury Park, NJ.

*Mathur SP. 1974a. Phthalate esters in the environment: Pollutants or natural products? J Environ

Qua1 3(3):189-197.

*Mathur SP. 1974b. Respirometric evidence of the utilization of di-octyl and di-2-ethylhexyl phthalate

plasticizers. J Environ Quality 3:207-209.

*Morrissey RE, Lamb JC, Morris RW, et al. 1989. Results and evaluations of 48 continuous breeding

reproduction studies conducted in mice. Fundam Appl Toxicol 13:747-777.

*NAS/NRC. 1989. Biologic markers in reproductive toxicology. National Academy of

Sciences/National Research Council. Washington, DC: National Academy Press, 15-35.

Nematollahi J, Guess WL, Autian J. 1967. Plasticizers in medical application: I. Analysis and

toxicity evaluation of dialkyl benzenedicarboxylates. J Pharmacol Sci 56:1446-1453.

*NIOSH. 1983. Screening of priority chemicals for potential reproductive hazard. Atlanta, GA:

National Institute for Occupational Safety and Health, Centers for Disease Control. NTIS Order No.

PB85-220143.

*NIOSH. 1993. National Occupational Exposure Survey. Cincinnati, OH: National Institute for

Occupational Safety and Health, Centers for Disease Control. March 10, 1993.

*NIOSH RTECS. 1987. Registry of toxic effects of chemical substances. 1985-1986 Edition. Volume

4. Department of Health and Human Services, Public Health Service, Centers for Disease Control,

National Institute for Occupational Safety and Health, 3461.

NTP. 1982a. NTP technical bulletin. Research Triangle Park, NC: National Toxicology Program,

U.S. Department of Health and Human Services, 7.

NTP. 1982b. NTP technical bulletin. Research Triangle Park, NC: National Toxicology Program,

U.S. Department of Health and Human Services, 8.

*NTP. 1985. Di-n-octylphthalate: Reproduction and fertility assessment in CD-l mice when

administered in feed. Research Triangle Park, NC: National Institute of Environmental Health

Sciences, National Toxicology Program. NTP-85-140. NTIS Order No. PB85-218147.

*Oishi S. 1990. Effects of phthalic acid esters on testicular mitochondrial functions in the rat. Arch

Toxicol 64:143-147.

*Oishi S, Hiraga K. 1980. Testicular atrophy induced by phthalic acid esters: Effect on testosterone

and zinc concentrations. Toxicol Appl Pharmacol 53:35-41.
DI-n-OCTYLPHTHALATE 112

8. REFERENCES

*Oishi S, Hiraga K. 1982. Effects of monoesters of O-phthalic acid on serum lipid composition of rats.

Toxicol Lett 14:79-84.

Perwak, Goyer M, Schimke G, et al. 1980. An exposure and risk assessment for phthalate esters.

Final draft report. Washington, DC: U.S. Environmental Protection Agency, Office of Water and

Waste Management.

*Peterson JC, Freeman DH. 1984. Variations of phthalate ester concentrations in sediments from the

Chester River, Maryland. Inter J Environ Anal Chem 18:237-252.

*Petrasek AC, Kugelman IJ, Austern BM, et al. 1983. Fate of toxic organic compounds in wastewater

treatment plants. J WPCF 55:1286-1296.

Phillips LJ. 1992. Regional relationships between toxic releases, and environmental and human

exposure to toxic substances. Bull Environ Contam Toxicol 48:795-802.

*Peon R, Lecavalier P, Mueller R, et al. 1995. Subchronic oral toxicity of di-n-octylphthalate and di(2-

ethylhexyl)phthalate in the rat. [ATSDR peer-reviewed draft].

*Ritsema R, Cofino WP, Frintop PCM, et al. 1989. Trace-level analysis of phthalate esters in surface

water and suspended particulate matter by means of capillary gas chromatography with electron-capture

and mass-selective detection. Chemosphere 18:2161-2175.

Russell D, McDuffie B. 1986. Chemodynamic properties of phthalate esters: Partitioning and soil

migration. Chemosphere 15:1003-1021.

Sabatini S, Fracasso A, Bazzato G, et al. 1989. Effect of phthalate acid esters on transport in toad

bladder membrane. J Pharmacol Exp Ther 250:910-914.

Sanborn JR, Metcalf RL, Yu CC, et al. 1975. Plasticizers in the environment: The fate of di-n-octyl

phthalate (DOP) in two model ecosystems and uptake and metabolism of DOP by aquatic organisms.

Arch Environ Contam Toxicol 3:244-255.

*Sato T, Nagase H, Sato K, et al. 1994. Enhancement of the mutagenicity of amino acid pyrolysates

by phthalate esters. Environ Mol Mut 24:325-331.

*Sax NI, Lewis RJ Sr. 1989. Dangerous properties of industrial materials. Volume II, 7th ed. New

York, NY: Van Nostrand Reinhold, 1465-1466.

Schwartz BS, Ford DP, Bolla KI, et al. 1990. Solvent-associated decrements in olfactory function in

paint manufacturing workers. Am J Ind Med 18:697-706.

*Seed JL. 1982. Mutagenic activity of phthalate esters in bacterial liquid suspension assays. Environ

Health Perspect 45:111-114.

Shafer KH, Cooke M, DeRoos F, et al. 1981. WCOT capillary column GC/FT-IR and GC/MS for

identifying toxic organic pollutants. Appl Spectroscopy 35:469-472.
DI-n-OCTYLPHTHALATE 113 

8. REFERENCES 

*Shelton DR, Boyd SA, Tiedje JM. 1984. Anaerobic biodegradation of phthalic acid esters in sludge. 

Environ Sci Technol 18:93-97. 

*Shibamoto T, Wei CI. 1986. Mutagenicity of materials extracted from synthetic rubber. Agric Biol 

Chem 50:513-514. 

*Singh AR, Lawrence WH, Autian J. 1972. Teratogenicity of phthalate esters in rats. J Pharm Sci 

61(1):51-55. 

*Sittig M. 1991. Handbook of toxic and hazardous chemicals and carcinogens. Volume 1, 3rd ed. 

Park Road, NJ: Noyes Publications, 674-675. 

*Stutz DR, Ulin S. 1992. Hazardous materials injuries: A handbook for pre-hospital care. Third 

edition. Beltsville, MD: Bradford Communications Corporation, 258-259. 

Sugawara N. 1974. Toxic effect of a normal series of phthalate esters on the hatching of shrimp eggs. 

Toxicol Appl Pharmacol 30:87-89. 

*Tabak HH, Quave SP, Mashni CI, et al. 1981. Biodegradability studies with organic priority pollutant 

compounds. J Water Quality 1503-1517. 

Takagi A, Sai K, Umemura T, et al. 1990. Significant increase of 8-hydroxyguanosine in liver DNA of 

rats following short-term exposure to the peroxisome proliferators di(2-ethylhexyl)phthalate and di(2- 

ethylhexyl)adipate. Jpn J Cancer Res 81:213-215. 

Takahashi T. 1977. Biochemical studies on phthalic esters: II. Effects of phthalic esters on 

mitochondrial respiration of rat liver. Biochem Pharmacol 26: 19-24. 

Teranishi H, Kasuya M. 1980. The effects of phthalate esters on fibroblasts in primary culture. 

Toxicol Lett 6:11-15. 

*TRI92. 1994. Toxic Chemical Release Inventory. U.S. Environmental Protection Agency, Office of 

Toxic Substances, Washington, DC. 

Urushigawa Y, Yonezawa Y. 1979. Chemico-biological interactions in biological purification systems: 

VI. Relation between biodegradation rate constants of di-n-alkyl phthalate esters and their retention 

times in reverse phase partition chromatography. Chemosphere 5:317-320. 

USITC. 1986. Synthetic organic chemicals: United States production and sales. Washington, DC: 

United States International Trade Commission. 

USITC. 1989. Synthetic organic chemicals: United States production and sales. Washington, DC: 

United States International Trade Commission. 

*USITC. 1994. Synthetic organic chemicals: United States production and sales. Washington, DC: 

United States International Trade Commission.
DI-n-OCTYLPHTHALATE 114 

8. REFERENCES 

*Valkenburg CA, Munslow WD, Butler LC. 1989. Evaluation of modifications to extraction 

procedures used in analysis of environmental samples from Superfund sites. J Assoc Off Anal Chem 

72(4):602-608. 

*Vista Chemical Company. 1992. Petition to delist di-n-octylphthalate under Section 313 of the 

Emergency Planning and Community Right-to-Know Act of 1986. Submitted to U.S. Environmental 

Protection Agency. Austin, TX. 

Walker JD. 1990. Review of chemical fate testing conducted under section 4 of the toxic substances 

control act: Chemicals, tests, and methods. J Bacterial 13:78-90. 

*Wang YY, Marsden PJ, Flessel CP, et al. 1990. Evaluation and validation of protocols for 

measurement of the mutagenicity of environmental samples. In: Friedman D, ed. Waste testing and 

quality assurance: Second volume. STP 1062. 

*Wild SR, Jones KC. 1992. Organic chemicals entering agricultural soils in sewage sludges: 

Screening for their potential to transfer to crop plants and livestock. Sci Total Environ 119:85-l 19. 

Williams DF. 1981. The toxicology of additives in medical plastics. In: Williams DF, ed. Systemic 

aspects of biocompatibility. Volume II. Boca Raton, FL: CRC Press, Inc., 145-157. 

*Wolfe NL, Burns LA, Steen WC. 1980. Use of linear free energy relationships and an evaluate model 

to assess the fate and transport of phthalate esters in the aquatic environment. Chemosphere 9:393-402. 

Yu X, Wang X, Bartha R, et al. 1990. Supercritical fluid extraction of coal tar contaminated soil. 

Environ Sci Technol 24:1732-1738. 

*Zeiger E, Haworth S, Mortelmans K, et al. 1985. Mutagenecity testing of di(Zethylhexyl)phthalate 

and related chemicals in salmonella. Environ Mutagen 7:213-232. 

*Zeiger E, Haworth S, Speck W, et al. 1982. Phthalate ester testing in the National Toxicology 

Program’s environmental mutagenesis test development program. Environ Health Perspect 45:99-101.
DI-n-OCTYLPHTHALATE 115 

9. GLOSSARY 

Acute Exposure -- Exposure to a chemical for a duration of 14 days or less, as specified in the 

Toxicological Profiles. 

Adsorption Coefficient (Koc) -- The ratio of the amount of a chemical adsorbed per unit weight of 

organic carbon in the soil or sediment to the concentration of the chemical in solution at equilibrium. 

Adsorption Ratio (Kd) -- The amount of a chemical adsorbed by a sediment or soil (i.e., the solid 

phase) divided by the amount of chemical in the solution phase, which is in equilibrium with the solid 

phase, at a fixed solid/solution ratio. It is generally expressed in micrograms of chemical sorbed per 

gram of soil or sediment. 

Bioconcentration Factor (BCF) -- The quotient of the concentration of a chemical in aquatic organisms 

at a specific time or during a discrete time period of exposure divided by the concentration in the 

surrounding water at the same time or during the same period. 

Cancer Effect Level (CEL) -- The lowest dose of chemical in a study, or group of studies, that 

produces significant increases in the incidence of cancer (or tumors) between the exposed population 

and its appropriate control. 

Carcinogen -- A chemical capable of inducing cancer. 

Ceiling Value -- A concentration of a substance that should not be exceeded, even instantaneously. 

Chronic Exposure -- Exposure to a chemical for 365 days or more, as specified in the Toxicological 

Profiles. 

Developmental Toxicity -- The occurrence of adverse effects on the developing organism that may 

result from exposure to a chemical prior to conception (either parent), during prenatal development, or 

postnatally to the time of sexual maturation. Adverse developmental effects may be detected at any 

point in the life span of the organism. 

Embryotoxicity and Fetotoxicity -- Any toxic effect on the conceptus as a result of prenatal exposure 

to a chemical; the distinguishing feature between the two terms is the stage of development during 

which the insult occurred. The terms, as used here, include malformations and variations, altered 

growth, and in utero death. 

EPA Health Advisory -- An estimate of acceptable drinking water levels for a chemical substance 

based on health effects information. A health advisory is not a legally enforceable federal standard, but 

serves as technical guidance to assist federal, state, and local officials. 

Immediately Dangerous to Life or Health (IDLH) -- The maximum environmental concentration of a 

contaminant from which one could escape within 30 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.
DI-n-OCTYLPHTHALATE 116 

9. GLOSSARY 

Immunologic Toxicity -- The occurrence of adverse effects on the immune system that may result from 

exposure to environmental agents such as chemicals. 

In vitro -- Isolated from the living organism and artificially maintained, as in a test tube. 

In Vivo -- Occurring within the living organism. 

Lethal Concentration(LO) (LC LO) -- 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) ( LD LO) -- The lowest dose of a chemical introduced by a route other than inhalation 

that is expected to have caused death in humans or animals. 

Lethal Dose(50) (LD50) -- The dose of a chemical which has been calculated to cause death in 50% of a 

defined experimental animal population. 

Lethal Time(50) (LT50) -- A calculated period of time within which a specific concentration of a 

chemical is expected to cause death in 50% of a defined experimental animal population. 

Lowest-Observed-Adverse-Effect Level (LOAEL) -- The lowest dose of chemical in a study, or group 

of studies, that produces statistically or biologically significant increases in frequency or severity of 

adverse effects between the exposed population and its appropriate control. 

Malformations -- Permanent structural changes that may adversely affect survival, development, or 

function. 

Minimal Risk Level -- An estimate of daily human exposure to a dose of a chemical that is likely to be 

without an appreciable risk of adverse noncancerous effects over a specified duration of exposure. 

Mutagen -- A substance that causes mutations. A mutation is a change in the genetic material in a 

body cell. Mutations can lead to birth defects, miscarriages, or cancer. 

Neurotoxicity -- The occurrence of adverse effects on the nervous system following exposure to 

chemical. 

No-Observed-Adverse-Effect Level (NOAEL) -- The dose of chemical at which there were no 

statistically or biologically significant increases in frequency or severity of adverse effects seen between 

the exposed population and its appropriate control. Effects may be produced at this dose, but they are 

not considered to be adverse. 

Octanol-Water Partition Coefficient (Kow) -- The equilibrium ratio of the concentrations of a chemical 

in n-octanol and water, in dilute solution. 

Permissible Exposure Limit (PEL) -- An allowable exposure level in workplace air averaged over an 

8-hour shift.
DI-n-OCTYLPHTHALATE 117

9. GLOSSARY

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. 3 11 of the Clean Water Act. Quantities

are measured over a 24-hour period.

Reproductive Toxicity -- The occurrence of adverse effects on the reproductive system that may result

from exposure to a chemical. The toxicity may be directed to the reproductive organs and/or the related

endocrine system. The manifestation of such toxicity may be noted as alterations in sexual behavior,

fertility, pregnancy outcomes, or modifications in other functions that are dependent on the integrity of

this system.

Short-Term Exposure Limit (STEL) -- The maximum concentration to which workers can be exposed

for up to 15 min continually. No more than four excursions are allowed per day, and there must be at

least 60 min between exposure periods. The daily TLV-TWA may not be exceeded.

Target Organ Toxicity -- This term covers a broad range of adverse effects on target organs or

physiological systems (e.g., renal, cardiovascular) extending from those arising through a single limited

exposure to those assumed over a lifetime of exposure to a chemical.

Teratogen -- A chemical that causes structural defects that affect the development of an organism.

Threshold Limit Value (TLV) -- A concentration of a substance to which most workers can be

exposed without adverse effect. The TLV may be expressed as a TWA, as a STEL, or as a CL.

Time-Weighted Average (TWA) -- An allowable exposure concentration averaged over a normal

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.

DI-n-OCTYLPHTHALATE A-l 

APPENDIX A 

MINIMAL RISK LEVEL WORKSHEETS 

Chemical Name: Di-n-octylphthalate 

CAS Number: 117-84-0 

Date: December 1995 

Profile Status: Post-Public Comment - Draft 3 

Route: [ ] Inhalation [x] Oral 

Duration: [x] Acute [ ] Intermediate [ ] Chronic 

Graph Key: 5 

Species : Rat 

Minimal Risk Level: 3 [x] mg/kg/day [ ] ppm 

Reference: Lake et al. 1986 

Experimental design: Di-n-octylphthalate was administered (1,000 mg/kg/day) once/day for 14 days to 

a group of 4-6 male Sprague-Dawley rats. A group of male rats, administered the corn oil vehicle, 

served as controls. Following the last dose, animals were starved overnight and killed by cervical 

dislocation. Livers were excised to be weighed, then used for biochemical assays; histopathological 

examination was not performed. 

Effects noted in study and corresponding doses: Liver effects were observed in treated rats. The 

hepatic effects consisted of a statistically significant (p < 0.01) increase (17 %) in relative liver weight 

and a reduction (approximately 30%) in 7-ethoxycoumarin O-deethylase activity relative to the vehicle 

control. Enzymatic indicators of peroxisome proliferation (KCN-insensitive palmitoyl-CoA oxidation 

or enoyl-CoA hydratase heat labile activity) were not significantly altered compared to controls. No 

significant changes in P-450 content or in the following activities were noted: ethylmorphine-Ndemethylase, lauric acid 1 1-hydroxylation, and lauric acid 12-hydroxylation. 

Dose and end point used for MRL derivation:

[ ] NOAEL [x] LOAEL (DOSE: 1000 mg/kg/day) 

Uncertaintv Factors used in MRL derivation:

[x] 3 for use of a minimal LOAEL 

[x] 10 for extrapolation from animals to humans 

[x] 10 for human variability 

Was a conversion used from ppm in food or water to a mg/body weight dose? No. If so, explain: 

If an inhalation study in animals. list the conversion factors used in determining human equivalent dose:

Other additional studies or pertinent information which lend support to this MRL: The choice of liver 

toxicity as the basis for the acute oral MRL is supported by similar effects seen in other acute- and 

intermediate-duration studies in rats (DeAngelo et al. 1986; Lake et al. 1984; Mann et al. 1985).
DI-n-OCTYLPHTHALATE A-2 

APPENDIX A 

Chemical Name: Di-n-octylphthalate 

CAS Number: 117-84-0 

Date: December 1995 

Profile Status: Post-Public Comment - Draft 3 

Route: [ ] Inhalation [x] Oral 

Duration: [ ] Acute [x] Intermediate [ ] Chronic 

Graph Key: 2 1 

Species: Rat 

Minimal Risk Level: 0.4 [x] mg/kg/day [ ] ppm 

Reference: Poon et al. 1995 

Experimental design: Groups of 10 male and 10 female Sprague-Dawley rats were maintained on diets 

containing 0, 5, 50, 500, or 5,000 ppm di-n-octylphthalate (DNOP) in the diet for 13 weeks. The 

study authors determined that these dietary concentrations corresponded to doses of 0, 0.4, 3.5, 36.8, 

350.1 mg/kg/day (males) and 0, 0.4, 4.1, 40.8, 402.9 mg/kg/day (females). Control animals received 

feed containing 4% corn oil. The rats were examined daily for clinical signs of toxicity, while food 

consumption and body weight data were collected weekly. At the end of the study, the animals were 

anesthetized with an i.p. injection of pentobarbital. Blood was collected from the aortic artery for 

hematological and biochemical determinations; enzymatic activity assays and comprehensive 

histopathological examinations were performed (although only data on the liver, thyroid, testis, and 

epididymis were presented). 

Effects noted in study and corresponding doses: No clinical signs of toxicity or reduction in food 

consumption or body weight gain were noted. No treatment-related changes in organ weights were 

noted. At 5,000 ppm, increased (p < 0.05) calcium was noted in males. Liver effects observed in rats 

administered di-n-octylphthalate in the diet at a concentration of 5,000 ppm; the study authors 

calculated the doses at this concentration to be 350.1 mg/kg/day (males) and 402.9 mg/kg/day (females) 

(Peon et al. 1995). The hepatic effects consisted of a significant (p < 0.05) increases in 

ethoxyresorufin-0-deethylase activity (12-fold, males; 3-fold, females); no significant changes were 

noted in liver aminopyrine-N-demethylase or aniline hydrolase activities. Also, at 5,000 ppm, 

histopathological changes in hepatic architecture were noted, including moderate accentuation of 

zonation and mild-to-moderate increases in perivenous cytoplasmic vacuolation. Mild histological 

changes in the thyroid were also noted at 5,000 ppm that consisted of reduction in the follicle size and 

decreased colloid density. No effects were observed at 500 ppm (36.8 mg/kg/day for males and 40.8 

mg/kg/day for females). The MRL was derived by dividing the NOAEL value of 40.8 mg/kg/day for 

hepatic effects by an uncertainty factor of 100 (10 for extrapolation from animals to humans and 10 for 

human variability). 

Dose and end point used for MRL derivation:

[x] NOAEL (DOSE: 40.8 mg/kg/day) [ ] LOAEL 

Uncertainty Factors used in MRL derivation:

[ ] 10 for use of a LOAEL 

[x] 10 for extrapolation from animals to humans 

[x] 10 for human variability
DI-n-OCTYLPHTHALATE A - 3 

APPENDIX A 

Was a conversion used from ppm in food or water to a mg/body weight dose? No. 

If so, explain: 

If an inhalation study in animals, list the conversion factors used in determining human equivalent dose:

Other additional studies or pertinent information which lend support to this MRL: The choice of liver 

toxicity as the basis of the MRL is supported by necrosis and mild hepatic fatty changes seen in other 

acute- and intermediate-duration studies in rats (DeAngelo et al. 1986; Lake et al. 1984, 1986; Mann et 

al. 1985). Thyroid toxicity (decreased thyroxine levels and ultrastructural changes) was observed after 

rats were fed 2,000 mg/kg/day of di-n-octylphthalate in the diet for 3, 10, or 21 days (Hinton et al. 

1986).

DI-n-OCTYLPHTHALATE B-1 

APPENDIX B 

USER’S GUIDE 

Chapter 1 

Public Health Statement 

This chapter of the profile is a health effects summary written in non-technical language. Its intended 

audience is the general public especially people living in the vicinity of a hazardous waste site or 

chemical release. If the Public Health Statement were removed from the rest of the document, it would 

still communicate to the lay public essential information about the chemical. 

The major headings in the Public Health Statement are useful to find specific topics of concern. The 

topics are written in a question and answer format. The answer to each question includes a sentence 

that will direct the reader to chapters in the profile that will provide more information on the given 

topic. 

Chapter 2 

Tables and Figures for Levels of Significant Exposure (LSE) 

A table (2-l) and figure (2-l) are used to summarize health effects and illustrate graphically levels of 

exposure associated with those effects. These levels cover health effects observed at increasing dose 

concentrations and durations, differences in response by species, minimal risk levels (MRLs) to humans 

for noncancer end points, and EPA’s estimated range associated with an upper- bound individual 

lifetime cancer risk of 1 in 10,000 to 1 in 10,000,000. Use the LSE tables and figures for a quick 

review of the health effects and to locate data for a specific exposure scenario. The LSE tables and 

figures should always be used in conjunction with the text. All entries in these tables and figures 

represent studies that provide reliable, quantitative estimates of No-Observed-Adverse- Effect Levels 

(NOAELs), Lowest-Observed-Adverse-Effect Levels (LOAELs), or Cancer Effect Levels (CELs). 

The legends presented below demonstrate the application of these tables and figures. Representative 

examples of LSE Table 2-l and Figure 2-l are shown. The numbers in the left column of the legends 

correspond to the numbers in the example table and figure. 

LEGEND 

See LSE Table 2-1 

(1) Route of Exposure One of the first considerations when reviewing the toxicity of a substance 

using these tables and figures should be the relevant and appropriate route of exposure. When 

sufficient data exists, three LSE tables and two LSE figures are presented in the document. The 

three LSE tables present data on the three principal routes of exposure, i.e., inhalation, oral, and 

dermal (LSE Table 2-1, 2-2, and 2-3, respectively). LSE figures are limited to the inhalation (LSE 

Figure 2-l) and oral (LSE Figure 2-2) routes. Not all substances will have data on each route of 

exposure and will not therefore have all five of the tables and figures. 

(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
DI-n-OCTYLPHTHALATE B-2 

APPENDIX B 

example, an inhalation study of intermediate exposure duration is reported. For quick reference to 

health effects occurring from a known length of exposure, locate the applicable exposure period 

within the LSE table and figure. 

(3) Health Effect The major categories of health effects included in LSE tables and figures are death, 

systemic, immunological, neurological, developmental, reproductive, and cancer. NOAELs and 

LOAELs can be reported in the tables and figures for all effects but cancer. Systemic effects are 

further defined in the “System” column of the LSE table (see key number 18). 

(4) Key to Figure Each key number in the LSE table links study information to one or more data 

points using the same key number in the corresponding LSE figure. In this example, the study 

represented by key number 18 has been used to derive a NOAEL and a Less Serious LOAEL 

(also see the 2 “18r” data points in Figure 2-l). 

(5) Species The test species, whether animal or human, are identified in this column. Section 2.5, 

“Relevance to Public Health,” covers the relevance of animal data to human toxicity and Section 

2.3, “Toxicokinetics,” contains any available information on comparative toxicokinetics. Although 

NOAELs and LOAELs are species specific, the levels are extrapolated to equivalent human doses 

to derive an MRL. 

(6) Exposure Frequency/Duration The duration of the study and the weekly and daily exposure 

regimen are provided in this column. This permits comparison of NOAELs and LOAELs from 

different studies. In this case (key number IS), rats were exposed to 1,1,2,2-tetrachloroethane via 

inhalation for 6 hours per day, 5 days per week, for 3 weeks. For a more complete review of the 

dosing regimen refer to the appropriate sections of the text or the original reference paper, i.e., 

Nitschke et al. 1981. 

(7) System This column further defines the systemic effects. These systems include: respiratory, 

cardiovascular, gastrointestinal, hematological, musculoskeletal, hepatic, renal, and dermal/ocular. 

“Other” refers to any systemic effect (e.g., a decrease in body weight) not covered in these 

systems. In the example of key number 18, 1 systemic effect (respiratory) was investigated. 

(8) NOAEL A No-Observed-Adverse-Effect Level (NOAEL) is the highest exposure level at which 

no harmful effects were seen in the organ system studied. Key number 18 reports a NOAEL of 3 

ppm for the respiratory system which was used to derive an intermediate exposure, inhalation 

MRL of 0.005 ppm (see footnote “b”). 

(9) LOAEL A Lowest-Observed-Adverse-Effect Level (LOAEL) is the lowest dose used in the study 

that caused a harmful health effect. LOAELs have been classified into “Less Serious” and 

“Serious” effects. These distinctions help readers identify the levels of exposure at which 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. 

(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
DI-n-OCTYLPHTHALATE B-3 

APPENDIX B 

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 38r is 1 of 3 studies for which Cancer Effect Levels were derived. The 

diamond symbol refers to a Cancer Effect Level for the test species-mouse. The number 38 

corresponds to the entry in the LSE table. 

(18) Estimated Upper-Bound Human Cancer Risk Levels This is the range associated with the 

upper-bound for lifetime cancer risk of 1 in 10,000 to 1 in 10,000,000. These risk levels are 

derived from the EPA’s Human Health Assessment Group’s upper-bound estimates of the slope of 

the cancer dose response curve at low dose levels (q1*). 

(19) Key to LSE Figure The Key explains the abbreviations and symbols used in the figure.


DI-n-OCTYLPHTHALATE B-6 

APPENDIX B 

Chapter 2 (Section 2.5) 

Relevance to Public Health 

The Relevance to Public Health section provides a health effects summary based on evaluations of 

existing toxicologic, epidemiologic, and toxicokinetic information. This summary is designed to present 

interpretive, weight-of-evidence discussions for human health end points by addressing the following 

questions. 

1. What effects are known to occur in humans? 

2. What effects observed in animals are likely to be of concern to humans? 

3. What exposure conditions are likely to be of concern to humans, especially around hazardous 

 waste sites? 

The section covers end points in the same order they appear within the Discussion of Health Effects by 

Route of Exposure section, by route (inhalation, oral, dermal) and within route by effect. Human data 

are presented first, then animal data. Both are organized by duration (acute, intermediate, chronic). In 

vitro data and data from parenteral routes (intramuscular, intravenous, subcutaneous, etc.) are also 

considered in this section. If data are located in the scientific literature, a table of genotoxicity 

information is included. 

The carcinogenic potential of the profiled substance is qualitatively evaluated, when appropriate, using 

existing toxicokinetic, genotoxic, and carcinogenic data. ATSDR does not currently assess cancer 

potency or perform cancer risk assessments. Minimal risk levels (MRLs) for noncancer end points (if 

derived) and the end points from which they were derived are indicated and discussed. 

Limitations to existing scientific literature that prevent a satisfactory evaluation of the relevance to 

public health are identified in the Data Needs section. 

Interpretation of Minimal Risk Levels 

Where sufficient toxicologic information is available, we have derived minimal risk levels (MRLs) for 

inhalation and oral routes of entry at each duration of exposure (acute, intermediate, and chronic). 

These MRLs are not meant to support regulatory action; but to acquaint health professionals with 

exposure levels at which adverse health effects are not expected to occur in humans. They should help 

physicians and public health officials determine the safety of a community living near a chemical 

emission, given the concentration of a contaminant in air or the estimated daily dose in water. MRLs 

are based largely on toxicological studies in animals and on reports of human occupational exposure. 

MRL users should be familiar with the toxicologic information on which the number is based. Chapter 

2.5, “Relevance to Public Health,” contains basic information known about the substance. Other 

sections such as 2.7, “Interactions with Other Substances,” and 2.8, “Populations that are Unusually 

Susceptible” provide important supplemental information. 

MRL users should also understand the MRL derivation methodology. MRLs are derived using a 

modified version of the risk assessment methodology the Environmental Protection Agency (EPA) 

provides (Barnes and Dourson 1988) to determine reference doses for lifetime exposure (RfDs).
DI-n-OCTYLPHTHALATE B-7 

APPENDIX B 

To derive an MRL, ATSDR generally selects the most sensitive endpoint which, in its best judgement, 

represents the most sensitive human health effect for a given exposure route and duration. ATSDR 

cannot make this judgement or derive an MRL unless information (quantitative or qualitative) is 

available for all potential systemic, neurological, and developmental effects. If this information and 

reliable quantitative data on the chosen endpoint are available, ATSDR derives an MRL using the most 

sensitive species (when information from multiple species is available) with the highest NOAEL that 

does not exceed any adverse effect levels. When a NOAEL is not available, a lowest-observed-adverseeffect 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.