# NTP-CERHR Monograph on the **Potential Human Reproductive and Developmental Effects**  **of Di-Isodecyl Phthalate (DIDP)**

April 2003 NIH Publication No. 03-4485 

# ����������������������������������� **���������������������** ��������������������������� ��������������������������������������������

## Table of Contents

Preface

............................................................... ............................................................... ............... i

Introduction

............................................................... ............................................................... ....... ii

NTP Brief on Di-Isodecyl Phthalate (DIDP)

............................................................... .................... 1

References

............................................................... ............................................................... .......... 3

Appendix I. NTP-CERHR Phthalates Expert Panel Preface

............................................................... ............................................................... I-1 Expert Panel

............................................................... ....................................................... I-2

Appendix II. Phthalates Expert Panel Report on DIDP Preface

............................................................... .............................................................. II-i Chemistry, Usage and Exposure

............................................................... ....................... II-1 General Toxicological and Biological Parameters

......................................................... II-4 Developmental Toxicity Data

............................................................... ......................... II-10 Reproductive Toxicity

............................................................... .................................... II-14 Data Summary & Integration

............................................................... ......................... II-17 References

............................................................... ...................................................... II-31 Tables

............................................................... ............................................................. II-35

Appendix III. Public Comments on the Phthalates Expert Panel Reports AdvaMed

............................................................... ......................................................... III-1 American Chemistry Council (12-7-2000)

............................................................... ..... III-5 American Chemistry Council (12-11-2000)

............................................................... ... III-7 American Chemistry Council (4-13-2001)

............................................................... ... III-58 Discovery Medical, Inc

............................................................... ................................. III-66 Environmental Working Group (11-3-2000)

............................................................... . III-67 Environmental Working Group (12-8-2000)

............................................................... . III-69 William Faber

............................................................... ................................................ III-71 Healthy Environments & Product Safety Branch

........................................................ III-81 Health Care Without Harm

............................................................... ........................... III-83 Beverly Smith

............................................................... ................................................ III-87 Swedish Chemical Inspection Agency

............................................................... .......... III-88i The National Toxicology Program (NTP) established the NTP Center for the Evaluation of Risks to Human Reproduction (CERHR) in 1998. The CERHR is a publicly accessible resource for information about adverse repro

ductive and/or developmental health effects associated with exposure to environmental and/or occupational chemicals. The CERHR is located at the National Institute of Envi

ronmental Health Sciences (NIEHS) of the National Institutes of Health and Dr. Michael Shelby is the director. 1

The CERHR broadly solicits nominations of chemicals for evaluation from the public and private sectors. The CERHR follows a formal process for review and evaluation of nominated chemicals that includes multiple opportunities for public comment. Chemicals are selected for evaluation based upon several factors including the following:

• potential for human exposure from use and occurrence in the environment.

• extent of public concern.

• production volume.

• availability of scientific evidence for reproductive and/or developmental tox

icity.

The CERHR convenes a scientific expert panel that meets in a public forum to review, discuss, and evaluate the scientific literature on the selected chemical. Public comment is invited prior to and during the meeting. The expert panel produces a report on the chemical’s reproductive and developmental toxicities and provides its opinion of the degree to which exposure to the chemical is hazard

ous to humans. The panel also identifies areas of uncertainty and where additional data are needed. The CERHR expert panels use explicit guidelines to evaluate the scientific literature and prepare the expert panel reports. Expert panel reports are made public and comments are solicited.

Next, the CERHR prepares the NTP-CERHR monograph. The NTP-CERHR monographincludes the NTP brief on the chemical evaluated, the expert panel report, and all public comments. The goal of the NTP brief is to provide the public, as well as government health, regulatory, and research agencies, with the NTP’s interpretation of the potential for the chemical to adversely affect human repro

ductive health or children’s health. The NTPCERHR monograph is made publicly available electronically on the CERHR web site and in hard copy or CD-ROM from the CERHR. 

### Preface

1 Information about the CERHR is available on the web at < http://cerhr.niehs.nih.gov > or by contact

ing the director: P.O. Box 12233, MD EC-32, NIEHS, Research Triangle Park, NC 27709 919-541-3455 [phone] 919-316-4511 [fax] shelby@niehs.nih.gov [email] Information about the NTP is available on the web
at < http://ntp-server.niehs.nih.gov > or by contact

ing the NTP Office of Liaison and Scientific Re

view at the NIEHS: liaison@starbase.niehs.nih.gov [email] 919-541-0530 [phone]i i iii In 1999, the CERHR Core Committee, an advi

sory committee composed of representatives from NTP member agencies, recommended seven phthalates for expert panel review.

These chemicals were selected because: (a) there is the potential for human exposure from their widespread use and occur

rence within the environment, (b) they have a high production volume, (c) there is substantial scientific literature addressing the reproductive and/or developmental toxicities of these chemi

cals, and (d) they are of concern to the public.

These seven phthalates are as follows:

• di(2-ethylhexyl)phthalate (DEHP)

• di-isononyl phthalate (DINP)

• di-isodecyl phthalate (DIDP)

• di-n-butyl phthalate (DBP)

• butyl benzyl phthalate (BBP)

• di-n-octyl phthalate (DnOP)

• di-n-hexyl phthalate (DnHP)

Phthalates are a group of similar chemicals widely used to soften and increase the flex

ibility of plastic consumer products such as shower curtains, medical devices, upholstery, raincoats, and soft squeeze toys. They are not bound to the plastics and can leach into the sur

rounding environment. The scientific literature on the reproductive and developmental toxici

ties of several phthalates is extensive. In addi

tion, there is widespread public concern about the safety of phthalates.

As part of the evaluation of phthalates, the CERHR convened a panel of scientific experts (Appendix I) to review, discuss, and evaluate the scientific evidence on the potential repro

ductive and developmental toxicities of each phthalate. There were three public meetings of this panel (August 17-19 and December 15- 17, 1999 and July 12-13, 2000). The CERHR received numerous public comments on the phthalates throughout the evaluation process.

The NTP has prepared an NTP-CERHR mono

graph for each phthalate. This monograph includes the NTP brief on DIDP, a list of the expert panel members (Appendix I), the expert panel’s report on DIDP (Appendix II), and all public comments received on the expert panel’sreports on phthalates (Appendix III). The NTPCERHR monograph is intended to serve as a single, collective source of information on the potential for DIDP to adversely affect human reproduction or development. Those interested in reading this report may include individuals, members of public interest groups, and staff of health and regulatory agencies.

The NTP brief included within this report presents the NTP’s interpretation of the poten

tial for exposure to DIDP to cause adverse reproductive or developmental effects in peo

ple. It is based upon information about DIDP provided in the expert panel report, the public comments, and additional scientific informa

tion available since the expert panel meetings. The NTP brief is intended to provide clear, balanced, scientifically sound information on the potential for DIDP exposures to result in adverse health effects on development and reproduction. 

### Introductioni i iii While there are biological and practical rea

sons for considering developmental toxicity and reproductive toxicity as 2 separate is

sues, it is important to keep in mind that life in mammals, including humans, is a cycle. In brief, the cycle includes the production of sperm and eggs, fertilization, prenatal de

velopment of the offspring, birth, post-natal development, sexual maturity, and, again, production of sperm and eggs.

In the past, toxic effects were often stud

ied in a “life stage specific” manner. Thus, concerns for developmental toxicity were addressed by exposing pregnant mothers and looking for adverse effects in fetuses. Developmental toxicity was detected as death, structural malformations, or reduced weights of the fetuses just prior to birth. Re

productive toxicity was studied by exposing sexually mature adults to the chemical of in

terest and effects were detected as impaired capacity to reproduce. Over the years, toxi

cologists realized that exposure during one part of the life cycle could lead to adverse effects that might only be apparent at a dif

ferent part of the life cycle. For example, ex

posure of a sexually mature individual to an agent capable of inducing genetic damage in eggs or sperm might have no apparent effect on the exposed individual. However, if a genetically damaged egg or sperm from that individual is involved in fertilization, the induced genetic damage might lead to death or a genetic disorder in the offspring. In this example, chemical-induced damage is detected in the next generation. In con

trast, the reproductive system begins devel

oping well before birth and continues until sexual maturity is attained. Thus, exposure of sexually immature animals, either before or following birth, to agents or conditions that adversely affect development of the reproductive system can result in structural or functional reproductive disorders. These effects may only become apparent after the exposed individual reaches the age of pu

berty or sexual maturity.

Thus, in the case of genetic damage induced in eggs or sperm, what might be considered reproductive toxicity gives rise to develop

mental disorders. Conversely, in the case of adverse effects on development of the reproductive tract, developmental toxicity results in reproductive disorders. In both these examples it is difficult to make a clear distinction between developmental and re

productive toxicity. This issue is important in considering the phthalate evaluations because evidence of developmental toxic

ity affecting reproductive capacity in later stages of the life cycle is reported for at least 3 of the phthalates -BBP, DBP, and DEHP. 

### Developmental Toxicity versus Reproductive Toxicity1NTP Brief What is DIDP? DIDP is a complex, oily substance manufactured by reaction of phthalic anhydride and isodecyl alcohol in the presence of a catalyst. It contains a mixture of branched, primarily C-10 phthalate isomers such as the one shown in Fig. 1. The average chemical formula for the mixture is C 28 H 46 O 4 . It is one of a group of industrially important chemicals known as phthalates. Phthalates are used primarily as plasticizers to add flexibility to plastics. DIDP is used as a plasticizer in a wide variety of polyvinyl chloride (PVC) plastic products. These include coverings on wires and cables, artificial leather, toys, carpet backing, and pool liners. It has only limited use in food packaging or handling and is not used in medical devices.

The expert panel report notes that approximately 135,000 metric tons (~298 million pounds) of DIDP were used in the U.S. in 1998.

Are People Exposed to DIDP?* Yes. There are several ways that people may be exposed to DIDP at home or at work. Human exposure to DIDP can occur during the manufacture of DIDP, during the manufacture of DIDP-containing products, during the use of such products, or through the presence of DIDP in the environment. Environmental exposures can occur through air, water, or contact with DIDP-containing products. Several studies have shown that DIDP is not detectable in food. Studies to determine the extent of human DIDP exposures have not been conducted. Because of inadequate information on human exposure to DIDP, the expert panel took the conservative position of assuming that general population exposures in the U.S. would be less than 3-30 μg/kg bw/day (micrograms per kilogram body weight per day). This is the range of exposures estimated for the more widely used phthalate, DEHP. By comparison, a small drop of water weighs approximately 30,000 μg and a grain of table salt weighs approximately 60 μg.

Can DIDP Affect Human Development or Reproduction? Possibly. Although there is no direct evidence that exposure of people to DIDP adversely affects reproduction or development, studies with rats have shown that exposure to DIDP can cause adverse developmental effects, but it does not affect reproduction (Fig. 2).

Scientific decisions concerning health risks aregenerally based on what is known as “weightof-the-evidence.” In this case, recognizing the lack of human data and the evidence of effects in laboratory animals, the NTP judges the scientific evidence sufficient to conclude that DIDP is a developmental toxicant and could adversely affect human development if the levels of exposure were sufficiently high. The scientific evidence indicates that DIDP will not adversely affect human reproduction. (Fig. 3).

Summary of Supporting Evidence As presented in the expert panel report, DIDP studies in rats addressed effects on both 

### NTP Brief on Di-Isodecyl Phthalate (DIDP)

O O

O O **Figure 1.** Chemical structure of the diisodecyl phthalate isomer, di-(8-methylnonyl) phthalate

* Answers to this and subsequent questions may

be: Yes, Probably, Possibly, Probably Not, No or Unknown2NTP Brief

3NTP Brief

Clear evidence of adverse effects

Some evidence of adverse effects

Limited evidence of adverse effects

Insufficient evidence for a conclusion

Limited evidence of no adverse effects

Some evidence of no adverse effects

Clear evidence of no adverse effects Developmental Toxicity development and reproduction. These studies reported that exposure of pregnant dams to relatively high doses of DIDP causes abnormal development of the fetal skeleton, and reduced weight gain and survival of pups. In some instances, DIDP exposure was also associated with abnormalities of the urinary tract. The data also show that lactational exposure can contribute to reduced weight gain in pups. A mouse developmental toxicity study was reported in which only one high exposure level was employed. No evidence of maternal or fetal toxicity was observed.

Two thorough studies of DIDP’s effects on reproduction in rats found no evidence of effects on the structure or function of the male or female reproductive systems. There was no evidence of an antiandrogenic effect of DIDP in male rat pups. It is important to note that DIDP exposure levels used in the rodent studies discussed above are generally far higher than those experienced by people.

Are Current Exposures to DIDP High Enough to Cause Concern? Probably not. Although no data are available on general population exposures to DIDP, its chemical properties and uses make it unlikely that human exposures are any greater than to DEHP. If this is true, the scientific evidence does not point to an immediate concern for adverse

Developmental Toxicity **Figure 2.** The weight of evidence that DIDP causes adverse developmental or reproductive effects in laboratory animals

Clear evidence of adverse effects

Some evidence of adverse effects

Limited evidence of adverse effects

Insufficient evidence for a conclusion

Limited evidence of no adverse effects

Some evidence of no adverse effects

Clear evidence of no adverse effects Developmental Toxicity

Reproductive Toxicity



### Figure 3. NTP conclusions regarding the possibilities that human development or reproduction might be adversely affected by exposure to DIDP

Serious concern for adverse effects

Concern for adverse effects

Some concern for adverse effects

Minimal concern for adverse effects Negligible concern for adverse effects
Insufficient hazard and/or exposure data 

### Reproductive effects 

### Developmental effects2NTP Brief

3NTP Brief reproductive or developmental effects. Thus, the NTP offers the following conclusions.

**The NTP concurs with the CERHR Phthalates Expert Panel that there is minimal concern for**  **developmental effects in fetuses and children**

**The NTP concurs with the CERHR Expert Panel that there is negligible concern for**  **reproductive toxicity in exposed adults.**

These conclusions are based on the assumption that the general US population is exposed to DIDP at less than 30 μg/kg bw/day.

Information is not available on the levels of exposure in children mouthing DIDP-containing objects or in pregnant women occupationally exposed to DIDP. Thus, no conclusions can be reached concerning the possible hazards for these exposure circumstances. 

### References:

No new publications were located.

These conclusions are based on the information available at the time this brief was prepared. As new information on toxicity and exposure accumulate, it may form the basis for either lowering or raising the levels of concern ex

pressed in the conclusions.I-1Appendix I 

### Appendix I. NTP-CERHR Phthalates Expert Panel Report on DIDP
A 16-member panel of scientists covering dis

- ciplines such as toxicology, epidemiology, and medicine was recommended by the Core Com

- mittee and approved by the Associate Director of the National Toxicology Program. Over the course of a 16-month period, the panel criti

- cally reviewed more than 500 documents on 7 phthalates and identified key studies and issues for plenary discussions. At three public meet

- ings 1 , the expert panel discussed these studies, the adequacy of available data, and identified data needed to improve future assessments. At the final meeting, the expert panel reached con

- clusions on whether estimated exposures may result in adverse effects on human reproduction or development. Panel assessments were based on the scientific evidence available at the time of the final meeting. The expert panel reports were made available for public comment on October 10, 2000, and the deadline for public comments was December 11, 2000 ( Federal Register 65:196 [10 Oct. 2000] p60206). The Phthalates Expert Panel Report on DIDP is provided in Appendix II and the public com

- ments received on that report are in Appendix III. Input from the public and interested groups throughout the panel’s deliberations was in

- valuable in helping to assure completeness and accuracy of the reports. The Phthalates Expert Panel Reports are also available on the CERHR website < http://cerhr.niehs.nih.gov >.

1 Phthalate Expert Panel meeting dates were: August 17-19, 1999, in Alexandria, VA; December 15-17, 1999, in Research Triangle Park, NC; and July 12-13, 2000, in Arlington, VA.I-2Appendix I Robert Kavlock, Ph.D. (chair) EPA/ORD Research Triangle Park, NC

Kim Boekelheide, M.D., Ph.D. Brown University Providence, RI

Robert Chapin, Ph.D. NIEHS Research Triangle Park, NC

Michael Cunningham, Ph.D. NIEHS Research Triangle Park, NC

Elaine Faustman, Ph.D. University of Washington Seattle, WA

Paul Foster, Ph.D. Chemical Industry Institute of Toxicology Research Triangle Park, NC

Mari Golub, Ph.D. Cal/EPA Davis, CA

Rogene Henderson, Ph.D. Inhalation Toxicology Research Institute Albuquerque, NM Irwin Hinberg, Ph.D. Health Canada Ottawa, Ontario, Canada

Ruth Little, Sc.D. NIEHS Research Triangle Park, NC

Jennifer Seed, Ph.D. EPA/OPPT Washington, DC

Katherine Shea, M.D. North Carolina State University Raleigh, NC

Sonia Tabacova, M.D., Ph.D. FDA Rockville, MD

Shelley Tyl, Ph.D. Research Triangle Institute Research Triangle Park, NC

Paige Williams, Ph.D. Harvard University Cambridge, MA

Tim Zacharewski, Ph.D. Michigan State University, East Lansing, MI 

### Appendix I. NTP-CERHR Phthalates Expert Panel **(Name and Affiliation)**

# ����������������������������������� **���������������������** ��������������������������� ��������������������������������������������Appendix II 

# NTP-CERHR EXPERT PANEL REPORT

on Di-Isodecyl Phthalate

October 2000 NTP-CERHR-DIDP-00

### TABLE OF CONTENTS

1.0 CHEMISTRY, USAGE, AND EXPOSURE

............................................................... ................................... 1

1.1 Chemistry

............................................................... ............................................................... ...... 1 1.2 Exposure and Usage

............................................................... ..................................................... 1

2.0 GENERAL TOXICOLOGICAL AND BIOLOGICAL PARAMETERS

..................................................... 4

2.1 General Toxicity

............................................................... ........................................................... 4 2.2 Toxicokinetics

............................................................... .............................................................. 7 2.3 Genetic Toxicity

............................................................... ........................................................... 8

3.0 DEVELOPMENTAL TOXICITY DATA

............................................................... ..................................... 10

3.1 Human Data

............................................................... ............................................................... . 10 3.2 Experimental Animal Toxicity

............................................................... .................................... 10

4.0 REPRODUCTIVE TOXICITY

............................................................... .................................................... 14

4.1 Human Data

............................................................... ............................................................... . 14 4.2 Experimental Animal Toxicity

............................................................... .................................... 14

5.0 DATA SUMMARY & INTEGRATION

............................................................... ....................................... 17

5.1 Summary

............................................................... .............................................................. 17 5.1.1 Human Exposure

............................................................... .............................................. 17 5.1.1.1 Utility of Data to the CERHR Evaluation

........................................................... 17 5.1.2 General Biological and Toxicological Data

............................................................... ..... 17 5.1.2.1 Utility of Data to the CERHR Evaluation

........................................................... 20 5.1.3 Developmental Toxicity

............................................................... ................................... 21 5.1.3.1 Utility of Data to the CERHR Evaluation

........................................................... 23 5.1.4 Reproductive Toxicity

............................................................... ...................................... 26 5.1.4.1 Utility of Data to the CERHR Evaluation

........................................................... 26 5.2 Integrated Evaluation

............................................................... ................................................. 28 5.3 Expert Panel Conclusions

............................................................... .......................................... 29 5.4 Critical Data Needs

............................................................... .................................................... 30

6.0 REFERENCES

............................................................... ............................................................... .............. 31

7.0 TABLES

............................................................... ............................................................... ........................ 35Appendix IIAppendix II

II-i 

## PREFACE

The National Toxicology Program (NTP) and the National Institute of Environmental Health Sciences established the NTP Center for the Evaluation of Risks to Human Reproduction (CERHR) in June, 1998. The purpose of the Center is to provide timely, unbiased, scientifically sound evaluations of human and experimental evidence for adverse effects on reproduction, including development, caused by agents to which humans may be exposed.

The following seven phthalate esters were selected for the initial evaluation by the Center: butyl benzyl phthalate, di(2-ethylhexyl) phthalate, di-isodecyl phthalate, di-isononyl phthalate, di-n-butyl phthalate, di-n-hexyl phthalate, and di-n-octyl phthalate. Phthalate esters are used as plasticizers in a wide range of polyvinyl chloride-based consumer products. These chemicals were selected for the initial evaluation by the CERHR based on their high production volume, extent of human exposures, use in children’s products, published evidence of reproductive or developmental toxicity, and public

concern.

This evaluation is the result of three public Expert Panel meetings and 15 months of deliberations by a 16-member panel of experts made up of government and non-government scientists. This report has been reviewed by the CERHR Core Committee made up of representatives of NTP-par

ticipating agencies, by CERHR staff scientists, and by members of the Phthalates Expert Panel. This report is a product of the Expert Panel and is intended to (1) interpret the strength of scientific evidence that a given exposure or exposure circumstance may pose a hazard to reproduction and the health and welfare of children; (2) provide objective and scientifically thorough assessments of the scientific evidence that adverse reproductive/development health effects are associated with expo

sure to specifi c chemicals or classes of chemicals, including descriptions of an y uncertainties that would diminish confidence in assessment of risks; and (3) identify knowledge gaps to help establish research and testing priorities.

The Expert Panel Reports on phthalates will be a central part of the subsequent NTP report that will also include public comments on the Panel Reports and any relevant information that has become available since completion of the Expert Panel Reports. The NTP report will be transmitted to the appropriate Federal and State Agencies, the public, and the scientific community.

The NTP-CERHR is headquartered at NIEHS, Research Triangle Park, NC and is staffed and administered by scientists and support personnel at NIEHS and at Sciences International, Inc., Alexandria, Virginia.

Reports can be obtained from the website < http://cerhr.niehs.nih.gov / > or from: CERHR Sciences International, Inc. 1800 Diagonal Road, Suite 500 Alexandria, VA 22314-2808 Telephone: 703-838-9440II-iiAppendix II 

### A Report of the CERHR Phthalates Expert Panel :

Name Affiliation

Robert Kavlock, PhD (Chair) National Health and Environmental Effects Research Laboratory/ USEPA, Research Triangle Park, NC Kim Boekelheide, MD, PhD Brown University, Providence, RI Robert Chapin, PhD NIEHS, Research Triangle Park, NC Michael Cunningham, PhD NIEHS, Research Triangle Park, NC Elaine Faustman, PhD University of Washington, Seattle, WA Paul Foster, PhD Chemical Industry Institute of Toxicology, RTP, NC Mari Golub, PhD California Environmental Protection Agency, Sacramento, CA Rogene Henderson, PhD Lovelace Respiratory Research Institute, Albuquerque, NM Irwin Hinberg, PhD Health Canada, Ottawa, Ontario, Canada Ruth Little, ScD NIEHS, Research Triangle Park, NC Jennifer Seed, PhD Office of Toxic Substances/USEPA, Washington, DC Katherine Shea, MD, MPH Duke University, Durham, NC Sonia Tabacova, MD, PhD Food and Drug Administration, Rockville, MD Rochelle Tyl, PhD, DABT Research Triangle Institute, Research Triangle Park, NC Paige Williams, PhD Harvard University, Boston, MA Timothy Zacharewski, PhD Michigan State University, East Lansing, MI

With the Support of CERHR Staff:

**NTP/NIEHS**

Michael Shelby, PhD Director, CERHR Christopher Portier, PhD Acting Associate Director, NTP Gloria Jahnke, DVM Technical Consultant Lynn Goldman, MD Technical Consultant

**Sciences International, Inc**

**.**
John Moore, DVM, DABT Principal Scientist Annette Iannucci, MS Toxicologist Ann Walker, MS, ELS Information Specialist and Technical EditorAppendix II

II-1 

### 1.0 CHEMISTRY, USAGE, AND EXPOSURE

**1.1 Chemistry** 
**Figure 1:** Chemical Structure of a Di-isodecyl Phthalate Isomer (Di-(8-methylnonyl) phthalate)

Commercial diisodecyl phthalate (DIDP) is a complex substance that is assigned two CAS Registry Numbers (26761-40-0 and 68515-49-1) ( 1 ). A synonym is 1,2-benzenedicarboxylic acid, di-C9- 11branched alkyl esters, C10 rich. DIDP is manufactured by reaction of phthalic anhydride and isodecyl alcohol in the presence of an acid catalyst ( 1 ). The alcohol manufacturing processes are stable (essentially the same feed stock, propylene, and butene), so although the substances are complex, they are not variable ( 1 ). DIDP is an oily, viscous liquid at standard temperature and
pressure.

**Table 1: Physicochemical Properties of DIDP Property**  **Value** Chemical Formula C 28 H 46 O 4 Molecular Weight 447 Melting Point -48 o C Boiling Point 370 o C Specific Gravity 0.97 Solubility in Water Insoluble (< 0.001 mg/L) Log K ow ~10 (2)

**1.2 Exposure and Usage** 

Humans may be exposed to DIDP by the oral, dermal, and inhalation routes of exposure. Occupa

tional exposure occurs primarily through inhalation and dermal contact, while consumer exposure occurs primarily by oral and dermal routes. .

**Occupational Exposure** DIDP, like other phthalate esters, is manufactured within a closed system that is under negative pressure. However, some exposures may occur during the loading and unloading of railroad cars 

### O O

O OII-2Appendix IIAppendix II

II-3 and trucks. Somewhat higher exposures may occur during the production of polyvinyl chloride (PVC) products because of elevated temperatures and more open processes. The American Chemistry Council (ACC, formerly CMA) ( 1 ) cites six studies that indicate that exposures are below 1 mg/m 3 during production of phthalates and below 2 mg/m 3 during production of PVC. As discussed in Section 2.2, dermal exposure is not expected to result in significant absorption into the body.

**Consumer Exposure** The range of products that contain DIDP is quite broad. The amounts produced and the use categories for DIDP in 1998 are given in the Table 2.

**Table 2: Calculated 1998 US Consumption of DIDP** (thousands of metric tons)

**End Use Subtotal**  **Total** Film and Sheet 20 Skins – Unsupported 7 Pool Lining 9 Other 4 Artificial leather 20 Coated Fabrics 1 Dip Coating/Slush Molded 4 Toys 2 Traffic Cones <2 Other ~1 Tubings 9 Wire and Cables 45 Under-body Coating 36
**GRAND TOTAL 135**  ( 1 )

Since DIDP, like other phthalates, is not bound in PVC, it can be released throughout the lifecycle of a product. Some end products do not result in direct consumer contact b ut may contribute to releases into the environment. Such uses include automobile undercoating, building materials, wires, and cables ( 1 ). Products which humans may contact directly include shoes, carpet backing, pool liners, and gloves ( 1 ). Direct exposure may also occur through food as a result of uptake by food animals, certain vegetables, and migration of DIDP from food packaging.

Food: DIDP was not detected in 74 samples of composite fatty foods from the UK at a detection limit of 0.01 mg/kg ( 3 ). These retail samples consisted of carcass meat, meat products, offal, poultry, eggs, fish, fats and oils, milk, and milk products. DIDP was not detected in 39 samples of infant formula from the UK at an analytical limit of 0.1 mg/kg ( 4 ). In an earlier study ( 5 ), DIDPII-2Appendix IIAppendix II

II-3 was not detected in 59 samples of 15 different brands of infant formula analyzed at a typical detection limit of 0.01 mg/kg wet weight. Because DIDP concentrations in foods and infant formulas were below detection limits in the surveys conducted by Ministry of Agricultural Fisheries and Food (MAFF) ( 3-5 ), the ACC ( 1 ) considered dietary exposure to humans negligible. The results of sampling infant formulas for phthalates by the US Food and Drug Administration ( 6 ) suggests that phthalates are present in lower frequency and concentrations in the US than in Europe.

Toys : In a Dutch survey of teething rings and toy animals, DIDP levels were measured at a concentration of 1.4–15% ( 7 ). Surveys conducted by the UK government found DIDP in 6 of 18 toys in 1990, 4 of 27 toys in 1991, 0 of 16 toys in 1992, and 0 of 29 toys in 1996 ( 7 ). In a Danish survey of 17 children’s toys, those without PVC did not contain phthalates. DIDP was detected in 4 of the 7 PVC toys (3 teethers and 1 doll) at concentrations ranging from 0.7 to 10.1% by weight. Higher concentrations of DINP were also present. Precision measuring concentration is somewhat uncertain because the analytical method used (gas chromatography) did not cleanly resolve the peaks for DIDP and DINP ( 8 ). The Consumer Product Safety Commission (CPSC) did not detect DIDP in a sample of 35 toys that contained PVC. DINP was the predominant phthalate found. Although not specifically stated, the analytical methodology (GC/MS) used should have identified DIDP if present; lower levels of several phthalates were detected in some samples ( 9 ).

**Exposure Estimate** Based on the physicochemical characteristics of DIDP and limited monitoring data, the Expert Panel believes it reasonable to assume that exposure to DIDP in the general adult population is lower than exposure to DEHP, which is estimated at 3–30 μ g/kg bw/day ( 10 ). While no in vitro

or in vivo data on DIDP leaching from toys are available, it is reasonable to postulate exposures several-fold higher than the general population in infants and toddlers who mouth DIDP-containing products.

**The summary for Section 1 is located in Section 5.1.1.**II-4Appendix IIAppendix II

II-5 

### 2.0 GENERAL TOXICOLOGICAL AND BIOLOGICAL PARAMETERS

**2.1 General Toxicity** 

Oral The British Industrial Biological Research Association (BIBRA) ( 11 ) administered groups of 5 male and 5 female F344 rats (41–44 days old) dietary concentrations of 0, 0.3, 1.2, and 2.5% DIDP for 21 days. The authors calculated daily intake of DIDP as 0, 304, 1,134, and 2,100 mg/kg bw/day for males and 0, 264, 1,042, and 1,972 mg/kg bw/day for females. A fifth group was given diets containing 1.2% DEHP which corresponded to 1,077 mg/kg/day for males and 1,002 mg/kg bw/day for females. The level of cyanide-insensitive palmitoyl-CoA oxidation was determined. At nec

ropsy, clinical chemistry was conducted, and liver, kidney, and testes weights were recorded and the organs were preserved in 10% formalin for histologic examination.

There was a significant reduction in food consumption and mean body weight in male rats fed 2,100 mg/kg bw/day beginning on day 3 and continuing throughout the study (69–82% of control). In female rats fed 1,972 mg/kg bw/day, mean body weight was reduced beginning on day 10 and continuing throughout the study (83–87% of control). Absolute and relative liver weights were significantly increased at all doses in males and at the two highest doses in females. In males, absolute weights were 121, 186, and 172% of controls at low to high doses, respectively, and relative weights were 121, 201, and 254%, respectively. In females receiving the two highest doses, absolute weights were 160 and 192% of controls and relative weights were 176 and 238%, respectively. In low-dose males, absolute and relative weights were 121% of controls. A variety of other effects were observed at the two highest doses; these included a reduction in hepatocyte cytoplasmic basophilia in both sexes, an increase in eosinophilia (high dose only), reduced serum triglycerides and cholesterol levels in males (no dose-response relationship was apparent), and a significant increase in cyanide-insensitive palmitoyl-CoA oxidation in both sexes. There was a significant increase in the 11- and 12-hydroxylation (11- and 12-OH) of lauric acid (all treated males), and in the 12-OH level in females at the high dose of DIDP. Electron microscopic examination of hepatic peroxisomes showed a marked but variable increase in size and number in both sexes at the high dose, but the response was less marked in females. There was a significant decrease in kidney weight in both sexes at the high dose, but no histological changes were observed. Absolute testes weights were slightly, but significantly, reduced at 2,100 mg/kg bw/day, but relative testes weights were greater than controls; no histological changes were observed.

This study provides evidence that the liver is a target organ of DIDP. A similar pattern of effects noted with DEHP is seen: increased liver weight, induction of hepatic peroxisome proliferation, depressed serum triglycerides and cholesterol levels, and increased activity of hepatic metabolizing enzymes. The testes do not appear to be a target organ at these dose levels. The study provided a LOAEL of 1,042 mg/kg bw/day in females and 304 mg/kg bw/day in males. A NOAEL of 264 mg/ kg bw/day was identified for females but no NOAEL was identified for males due to increased liver weight and 11- and 12-OH activity at all dose levels.

In a 4-week study ( 12 ), groups of 5 male F344 rats (42 days old) were given dietary concentrations of 0, 0.02, 0.05, 0.1, 0.3, or 1.0% DIDP (made up of equal parts Hexaplas [ICI], Jayflex [Exxon],II-4Appendix IIAppendix II

II-5 and Palatinol Z [BASF]). These dose levels were reported to correspond to doses of 0, 25, 57, 116, 353, and 1,287 mg/kg bw/day. Another group was given a diet of 1% DEHP. Food consumption and body weights were recorded twice weekly. At necropsy, organ weights were recorded, cyanide-insensitive palmitoyl-CoA oxidation activity was measured, and tissues were preserved in formalin for histologic examination. At doses of 116 mg/kg bw/day and higher, there was a significant increase in relative liver weight, and at doses of 353 mg/kg bw/day and higher, absolute liver weights were significantly increased. The cyanide-insensitive palmitoyl-CoA activity was significantly increased at doses of 353 mg/kg bw/day and higher. Testes weight was not affected by treatment and there were no histological changes.

The study provides evidence that the liver is a target organ of DIDP and the effects seen are consistent with those observed with other studies of DIDP and with DEHP. The testes do not appear to be a target. The study provides a LOAEL of 353 mg/kg bw/day and a NOAEL of 116 mg/kg bw/ day.

BASF ( 13 ) administered groups of 20 male and 20 female Sprague-Dawley rats dietary concentrations of 5,000 or 10,000 Palatinol Z for 28 days. This corresponded to average daily doses of 600 and 1,250 mg/kg bw/day for males and 1,100 and 2,100 mg/kg bw/day for females. A control group of 10 males and 10 females was fed the basal diet. Blood samples were taken from 5/sex/group on day 14 or 15 for hematological assessment and urinalysis was conducted on day 23 or 24. At necropsy, liver, kidney, and heart weights were recorded, and the liver and kidneys were examined histologically. Absolute and relative liver weights were significantly increased at both dose levels in both sexes, but there were no histologic changes. No other effects were noted.

Based on this 28-day study, BASF ( 14 ) administered groups of 20 male and 20 female SpragueDawley rats dietary concentrations of 800, 1,600, 3,200, or 6,400 ppm DIDP (Palatinol Z) for 90 days. These levels were equivalent to average daily doses of 55, 100, 200, and 400 mg/kg bw/day for males and 60, 120, 250, and 500 mg/kg bw/day for females, respectively. A control group of 10 males and 10 females was fed the basal diet. An additional group was fed the 6,400 ppm diet for 90 days, followed by a recovery period of 21 days. Hematology and urinalysis were conducted on days 32–36 and 74–78. At necropsy, liver, kidney, and heart weights were recorded, and the tissues were preserved in 10% formalin. In male rats, there was a slight lag in body weight gain in the 100, 200, and 400 mg/kg bw/day groups from day 77 onward. This finding was still present in the 400 mg/kg bw/day group following the 21-day recovery period. In males, absolute liver weights were significantly increased at the highest (400 mg/kg bw/day) dose and relative liver weights were significantly higher in all groups; this effect persisted after the recovery period. In females, absolute liver weights were significantly increased at 250 and 500 mg/kg bw/day, and relative liver weights were significantly increased at doses of 120 mg/kg bw/day and higher. Relative kidney weights were significantly increased in males in all groups and in females at 120 and 250, but not 500, mg/ kg bw/day doses. No histological lesions were noted in testes, ovaries, liver, or kidneys.

The study offers support that the liver is a target organ of DIDP based on liver weight, but not histological, changes. The testes do not appear to be a target. A NOAEL in males of 200 mg/kg bw/day was assumed since an increase in absolute liver weight was reported at the highest dose. In females, a NOAEL of 120 mg/kg bw/day was assumed based on increased absolute and relativeII-6Appendix IIAppendix II

II-7 liver weights at the two higher doses.

Hazelton ( 15 ) administered groups of 10 male and 10 female Charles River CD rats dietary levels of 0, 0.05, 0.3, or 1% DIDP for 90 days. Based on body weights, rats were assumed to be young adults. Based on food intake rates and body weights reported by authors, doses of 0, 28, 170, and 586 mg/kg bw/day and 0, 35, 211, and 686 mg/kg bw/day were calculated for males and females, respectively. At necropsy, clinical chemistry was conducted, organ weights were recorded, and the tissues were preserved in 10% formalin. There were no significant effects on food consumption, body weights, or clinical chemistry. Absolute and relative liver weights were significantly increased at the high dose in both sexes. Relative kidney weights were significantly increased in males at the two higher doses. There were no histologic changes in the testes, liver, or kidney. A minimal increase in thyroid activity was observed at the highest dose level; the activity was judged to be higher when the follicles were more uniform and smaller in size with a lighter colloid along with a tall cuboidal or columnar epithelium.

The study provides confirming evidence that the liver is a target organ of DIDP. The testes do not appear to be a target as no testicular lesions were observed in the high-dose group. The study provides a LOAEL of 586(M)–686(F) mg/kg bw/day and a NOAEL of 170(M)–211(F) mg/kg bw/ day.

Hazelton ( 16 ) administered groups of 3 male and 3 female young adult beagle dogs dietary levels of 0, 0.05, 0.3, or 1% DIDP for 90 days. Based on food intake rates and body weights reported by authors, doses of 0, 15, 77, and 307 mg/kg bw/day and 0, 16, 88, and 320 mg/kg bw/day were calculated for males and females, respectively. There were no effects on food consumption, hematology, clinical chemistry (including ALT, AST, and BSP clearance), or urinalysis. Testicular lesions were not observed in microscopic slides prepared from Bouin’s-fixed testes in high-dose dogs. Three dogs (2 male, 1 female) in the 307

− 320 mg/kg bw/day group showed slight-tomoderate weight loss. At necropsy, there was a dose-related increase in absolute liver weights, but the small sample size precluded statistical analysis. The mean liver weights were 253, 248, 274, and 317 g (males) and 190, 212, 220, and 287 g (females) for the 0, 0.05, 0.3, and 1% groups, respectively. The authors also reported a slightly elevated liver to body weight ratio in 5 of 6 dogs at the highest dose tested. Swollen and vacuolated hepatocytes were noted in two mid-dose males, two mid-dose females, one high-dose male, and three high-dose females. The Expert Panel concluded that the small sample size in this study precludes the determination of a NOAEL. A LOAEL of 77(M)–88(F) mg/kg bw/day was identified based on liver effects.

Inhalation General Motors Research Laboratories ( 17 ) exposed 8 adult male Sprague Dawley rats by inhalation (aerosol) to 505 mg/m 3 (MMAD: 0.98μm) 6 hours/day, 5 days/week for 2 weeks. There were six control rats. After a subsequent 3-week observation period, the rats were killed and necropsied. There were no clinical signs of toxicity or effects on body weight. Effects in the lungs included a moderate increase in the width of alveolar septa with slight interstitial mixed inflammatory reactions, alveolar macrophages and type II pneumocytes were increased in number, and the peribronchial lymphoid tissue appeared slightly more prominent. No histological changes were noted in the liver, kidney, or spleen.II-6Appendix IIAppendix II

II-7 **2.2 Toxicokinetics** 

Phthalate Moiety Toxicokinetics

**Absorption (Rodents)** Rodents: Dermal absorption of phthalates decreases with increasing side chain length beyond four carbons ( 18 ). In rats, 80% of dermally applied 14 C-DIDP (ring-label) was recovered at the site of application 7 days after the application. Only 2% of the applied dose was recovered in other tissues or excreta with a total recovery of only 82% reported. In another study in rats in which total recoveries were better (94% or greater) ( 19 ), similar results were obtained. 14 C-DIDP was applied to the skin and the dose site was occluded. At 1, 3, and 7 days, 96, 92, and 93% of the doses, respectively, were still at the application site. Only trace amounts of radioactivity were found in other tissues and excreta. The total absorbed dose was approximately 4% of the administered dose. DIDP dermal absorption has not been tested in humans, but an in vitro study conducted with DEHP suggests that the DIDP absorption rate through human skin is likely lower than the absorption rate for rat skin ( 20 ). Studies conducted by Deisinger et al. ( 21 ) have demonstrated that dermal absorption of DEHP from a plasticized film is slower than dermal absorption of neat DEHP. It is reasonable to assume that these results apply to DIDP.

Oral: A study ( 22 ) conducted in rats evaluated the effect of oral dose on the toxicokinetics of 14 CDIDP (labeled carboxyl groups). The doses, which were administered by gavage in corn oil, were 0.1, 11.2, or 1,000 mg/kg bw. The amounts absorbed can be estimated from the total radioactivity excreted in urine and bile or retained in the carcass at the end of 72 hours, and were 56, 46, and 17% for the low, medium, and high doses, respectively. The remainder of the radiolabeled activity was excreted in the feces with evidence, from bile radioactivity, of some enterohepatic uptake. The study indicated that at low doses at least 56% of orally-administered DIDP is absorbed. The data suggest partial saturation of DIDP metabolism by esterases in the gut in rats within the dose range administered in the study (0.1

− 1,000 mg/kg).

Inhalation: Six male Sprague Dawley rats were exposed for 6 hours by inhalation (head only) to 91 mg/m 3 of 14 C-DIDP ( 17 ). Excreta were collected over a 72-hour period and 3 animals were analyzed for radioactivity immediately after the exposure and at 72 hours after the exposure. Assuming a minute volume of 200 mL for the rats, the estimated total amount of DIDP inhaled would be approximately 14.4 μmoles. The initial body burden was 8.3 μmoles, indicating that approximately 58% of what was inhaled was retained in the body. Twelve percent of the initial body burden was in the gut and 85% was in the lung. Seventy-three percent of the dose to the lung was cleared during the first 72 hours, indicating that absorption of DIDP or its metabolites from the lung into the rest of the body was about 73%.

**Biotransformation** Bacterial: Ejlertsson et al. ( 23 ) reported no degradation of DIDP by microorganisms in a laboratory scale landfill reactor during 100 days of incubation.

Rodent: In rats orally administered 14 C-DIDP ( 22 ), the major metabolites detected in urine were phthalic acid and the oxidized monoester derivative, but no DIDP or monoisodecyl phthalateII-8Appendix IIAppendix II

II-9 (MIDP) were detected over a wide range of doses (0.1

− 1,000 mg/kg). The relative amounts of each metabolite varied with dose with the monoester derivative increasing with increasing dose from 52% at the low dose to 72% at the high dose, while the phthalic acid decreased from 38 to 18%. The monoester oxidized derivative, MIDP, and DIDP were all detected in feces in dose-dependent amounts. The parent compound increased from 30 to 55 and 60% after doses of 0.1, 11, and 1,000 mg/kg, and the percentage of the oxidative derivative of the monoester and of MIDP at the same doses were, respectively, 25 and 30%, 14 and 26%, and 13 and 13%. The data suggest a metabolic scheme comparable to the one reported for DEHP, that is, de-esterification to the monoester form and an alcohol moiety by pancreatic lipase and intestinal mucosa esterase prior to absorption. The high content of MIDP in feces is consistent with such a scheme. The data also suggest saturation of the metabolism of DIDP in rats at a dose lower than 11 mg/kg.

**Distribution** In studies conducted in rodents by either the oral ( 22 ) or the dermal ( 18 ) route, there was limited distribution to the tissues. Seven days after dermal administration, only trace amounts of DIDP were left in the body and showed no specific tissue distribution. Three days after oral administration of doses up to 1,000 mg/kg, less than 1% of the DIDP was found in the tissues. Following inhalation ( 17 ), the major sites of DIDP-derived material were the lung and the gut immediately after exposure. The next highest levels were found in the liver, kidney, and brain. At 3 days following administration, 27, 8, 9, and 10% of the initial burdens in the lung, gut, liver, and kidney remained. No DIDP-derived material was left in the brain after 3 days.

**Excretion** In all studies in rodents, the major routes of excretion for absorbed DIDP are via the urine and feces. In orally-administered DIDP, fecal excretion increased from 58% of the total body burden at a dose of 0.1 mg/kg to 82% at a dose of 1,000 mg/kg. The remaining material was excreted in urine with less than 1% of the dose remaining in the animal after 3 days. There is evidence of excretion into the bile; the percentage of total administered dose that was recovered in bile decreased with increasing dose from 14% at a dose of 0.1 mg/kg to 4.7% at a dose of 1,000 mg/kg.

In rats exposed by inhalation, 45 and 41% of the absorbed dose were excreted via urine and feces, respectively. The excretion via the urine indicated an elimination half-life of 16 hours, with an elimination rate constant K e of 0.042/hour. The elimination half-life for all routes of excretion (rate of decline in body burden) was 26 hours with an elimination rate constant of 0.027/hour.

Side Chain-associated Toxicokinetics A major metabolite of DIDP, MIDP, is further oxidized.

**2.3 Genetic Toxicity**  The mutagenicity of DIDP has been examined in a number of bacterial ( 24-26 ), mammalian cell, and cell transformation assays. A bone marrow micronucleus test in CD-1 mice has also been performed ( 27 ). A recent OECD meeting ( 28 ) accepted the following conclusions “DIDP is not mutagenic in vitro in bacterial mutation assays (with and without metabolic activation) and is negative in a mouse lymphoma assay. It is not clastogenic in a mouse micronucleus assay in vivo

. This suggests that DIDP is a non-genotoxic agent.” DIDP tested negative in the L5178Y mouseII-8Appendix IIAppendix II

II-9 lymphoma mutation assay and the Balb/3T3 cell transformation assay ( 29 ). The data from the mutation and cell transformation assay were reviewed by OECD.

**The summary for Section 2, including general toxicity, toxicokinetics, and genetic toxicity, is located in Section 5.1.2.** II-10Appendix IIAppendix II

II-11 

### 3.0 DEVELOPMENTAL TOXICITY DATA

**3.1 Human Data**  There were no human data located for Expert Panel review.

**3.2 Experimental Animal Toxicity**  Three studies were found, two in rats and one in mice, that evaluated prenatal developmental toxicity following exposure by gavage to DIDP.

Hardin et al. ( 30 ) evaluated 60 chemicals, including 9 phthalates in the Chernoff-Kavlock assay in CD-1 mice. This is a screening protocol to prioritize chemicals for subsequent definitive developmental toxicity evaluations and to compare relative potencies. DIDP (CAS No. 26761-40- 0) was administered by gavage on gestation day (gd) 6–13 at 0 or 9,650 mg/kg bw/day (undiluted chemical, 10 mL/kg bw/day) to 50 mice/group. The dams delivered their litters, and dams and pups were terminated on postnatal day (pnd) 3. There was no maternal mortality; there were no weight change effects and no effects on numbers of live litters, litter size, litter survival, birth weight, or weight gain.

Waterman et al. (Table WEB-1) ( 31 ) administered DIDP (CAS No. 68515-49-1) to 25 SpragueDawley rats/group on gd 6–15 by gavage at 0, 100, 500, and 1,000 mg/kg bw/day. The dams were sacrificed on gd 21 and implantation sites were evaluated. Fetuses were weighed and examined for external, visceral, and skeletal malformations. At 1,000 mg/kg bw/day, maternal toxicity was indicated by decreased weight gain and food consumption. Effects on fetal mortality or weight were not observed at any dose. Signs of developmental toxicity were seen in fetuses from dams that received 500 and 1,000 mg/kg bw/day. There was a statistically significant increase in the percent litters with 7 th cervical ribs at the 1,000 mg/kg bw/day dose; a numerical increase in litter incidence with increasing dose (8.0, 18.2, 25, 41.7%) was also observed. A dose-related increase in the percent fetuses with a 7 th cervical rib was observed, with the incidence at the two highest doses attaining statistical significance (1.0, 2.3, 6.2, 9.2%). A second skeletal variant, rudimentary lumbar (14th) rib(s), showed increased incidence at the two highest doses that was significant on a percent litter basis at the highest dose and on a percent fetus basis at the tw o highest doses. Litter incidence values were 40.0, 36.4, 62.5, and 95.8%, while fetal incidence was 8.2, 9.0, 21.2, and 52%. Waterman et al. ( 31 ) interpreted their results as indicating a LOAEL for maternal and developmental toxicity at 1,000 mg/kg bw/day and a NOAEL of 500 mg/kg bw/day. The Expert Panel concurred with the maternal NOAEL but selected a developmental NOAEL of 100 mg/kg bw/day based on the significant incidence of cervical and accessory 14 th ribs. The Expert Panel informed the sponsor of the Waterman et al. study that the Panel believed that there were more recent and superior methods for the analysis of pup incidence. The sponsor statistically reanalyzed findings of toxicological interest using the generalized estimating equation (GEE) approach to the linearized model ( 32 ) and shared its reanalysis results with the Panel ( 33 ). This is a puplevel analysis within a model that uses the GEE approach to account for the litter effect, i.e., the correlation between outcomes measured on pups within the same litter. The dose groups were tested pair-wise versus controls; this gave similar results to a trend test based on a dose-response model fit with all dose levels up to that of interest included. The results, presented in tabular form below, are consistent with the interpretation of the Expert Panel.II-10Appendix IIAppendix II

II-11 The sponsor also provided benchmark doses at the 5 and 10% excess risk level, based on a multiplicative (or ‘extra’) excess risk function. At the 5% excess risk level, the benchmark doses (and their 95% lower confidence limits estimated by bootstrap methods) were estimated as 188 (169), 258 (238), and 645 (515) mg/kg bw/day for rudimentary lumbar ribs, skeletal variants, and supernumerary cervical ribs, respectively.

**Table 3: Mean Percent of Pups in Litter with Effect of Interest**  (significance level)
**Dose Group (DIDP mg/kg bw/day)**

0 100 500 1,000

Skeletal Variations 19.8 20.6 (0.70) 31.9* (0.05) 64.1** (0.001) Rudimentary Lumbar Ribs 8.4 9.4 (0.70) 21.9** (0.01) 51.9** (0.001) Supernumerary Cervical Ribs 1.1 3.1 (0.28) 6.2* (0.03) 10.2** (0.004) * p ≤ 0.05, ** p ≤ 0.01

Hellwig et al. ( 34 ) investigated the comparative developmental toxicity of a number of phthalates. They administered DIDP (CAS No. 26761-40-0) by gavage in olive oil at 0, 40, 200, and 1,000 mg/kg bw/day to Wistar rats on gd 6–15 in 7–10 pregnant rats per group (Table WEB 2). The dams were sacrificed on gd 20 and implantation sites were evaluated. Fetuses were weighed and examined for external, visceral, and skeletal malformations. At 1,000 mg/kg bw/day, there was maternal toxicity expressed as reduced feed consumption, vaginal hemorrhage in 3 dams, and increased absolute and relative liver weights. Kidney weight was unaffected. Developmental effects included increased incidences of percent fetal variations per litter (24.3, 37.2, 38.4, and 44.2% at 0, 40, 200, and 1,000 mg/kg bw/day, respectively) with the values at 200 and 1,000 identified as statistically significant. In the high-dose group, there were clear increases in rudimentary cervical ribs and accessory 14 th ribs. An increased incidence of dilated renal pelves and hydroureter was observed at all treatment levels which apparently contributed to a statistically significant increase in the mean percent of fetuses affected per litter with variations at the 200 and 1,000 mg/kg bw/day doses. The data at 200 mg/kg bw/day are at odds with the authors’ statement that “no substance-related effects were observed on dams, gestational parameters or fetuses among the two lower dose groups.” Since there were increased incidences of total fetal variations at both 200 and 1,000 mg/kg bw/day, the Expert Panel concluded that 40 mg/kg bw/day was the developmental NOAEL and 200 mg/kg bw/day the maternal NOAEL. The factors that led to the selection of these values, which differ from those of the authors, are discussed in Section 5.1.3.

Developmental effects were also observed in one- and two-generation reproductive toxicity studies in rats that are discussed in full detail under Section 4 ( 35, 36 ) (Table WEB-3). In both studies, dams were exposed to DIDP through diet from 10 weeks prior to mating through gestation and lactation. Dietary dose levels were 0, 0.25, 0.5, 0.75, and 1% for the one-generation study and 0,II-12Appendix IIAppendix II

II-13 0.2, 0.4, and 0.8% for the two-generation study. In the one-generation study, fetal body weights were lower in groups exposed to 0.5% DIDP and higher. There was no effect on offspring survival. For the two-generation study, developmental effects in F 1 offspring included a decrease in live pups at birth and on pnd 4 and a decrease in pup birth weight and weight gain in the high-dose group on pnd 0, 7, 14, and 21 for both sexes and also on pnd 4 for males. In F 1 pups, relative liver weights were significantly increased in females in the mid- and high-dose groups and males in the high-dose group. Liver cell hypertrophy and eosinophilia were also observed in the mid- and high-dose groups. F 1 females in the mid- and high-dose groups experienced a delay in vaginal opening (33.5 and 34.2 days, respectively, vs 32.2 days in control). The age of preputial separation was not affected in males, but the frequency of evaluation was not sufficient to rule out an effect. Developmental effects in F 2 pups were similar to those observed in F 1 pups. F 2 pup survival was reduced on pnd 1 and 4 in all treated groups, and also on pnd 7 and at weaning in the high-dosegroup. An unusually high incidence of pup deaths in 4, 2, and 4 litters of the low-, mid-, and highdose groups respectively was noted; it was opined that reduced survival is usually observed in small numbers of pups distributed over many litters. F 2 pup birth weight was reduced in males of the high-dose group and postnatal weight gain was reduced in all pups of the high dose-group on pnd 1, 4, 7, 14, and 21. Four high-dose male pups had undescended testes, an effect that was probably related to delayed development. Although F 2 pup liver weight was not increased, liver cell hypertrophy and eosinophilia were observed in mid- and high-dose males and females. Because postnatal survival was reduced in all treated F 2 pups, a NOAEL was not identified for this study. The 0.2% dose (131

− 152 mg/kg bw/day and 162

− 379 mg/kg bw/day in F 0 and F 1 dams during gestation and lactation, respectively) was identified as the developmental LOAEL.

The two generation study was repeated by ExxonMobil Biomedical ( 36 ) using lower doses of 0, 0.02,0.06, 0.2, and 0.4% in feed (Table WEB-4). In addition to lower doses, this study incorporated measurement of anogenital distance on day of birth and assessment of nipple retention on pnd 13 or 14, on all offspring of both generations. Age at which vaginal patency and preputial separation occurred was noted for 2 rats/sex/dose for both F 1 and F 2 offspring. Dams were exposed for 10 weeks prior to mating throughout pregnancy and gestation. Complete details of the study, including a description of reproductive effects in parents and offspring, are included in Section 4. In the F 1 offspring there were no effects on pup survival, body weight, or organ weights. However, an increased incidence of dilated renal pelves (8/29 vs 0/30) were noted in adult F 1 males of the high-dose group (0.4%). The authors did not consider the effect to be biologically significant. Developmental results in F 2 offspring were consistent with findings of the previous 2-generation study ( 35 ). Effects at the 0.2% dose level included significant reductions in F 2 pup survival on pnd 1 and 4 and significant decreases in body weights of female F 2 pups on pnd 14 and male pups on pnd 35. At the 0.4% dose level, F 2 pup survival was significantly decreased on pnd 1 and 4 and body weights were significantly lower for female F 2 pups on pnd 14 and 21 and for males F 2 pups on pnd 14, 28, and 35. At the high dose, the liver to body weight ratio was increased in F 2 female pups sacrificed on pnd 21, but authors stated that the result was not biologically significant due to a lack of absolute organ weight change. A histological examination was not conducted. No treated F 1 and F 2 pups experienced differences from controls in either anogenital distance or abnormal nipple retention. A developmental NOAEL of 0.06% (38–44 and 52–114 mg/kg bw/day during pregnancy and lactation, respectively) was identified by the study authors.II-12Appendix IIAppendix II

II-13 In order to determine if postnatal developmental effects in pups are due to lactational transfer of DIDP, a cross-fostering and switched-diet experiment was conducted by Exxon Biomedical Sciences ( 35 ). For the experiments, 20 CRl:CDBR VAF Plus rats/group were fed diets with 0 or 0.8% DIDP for 10 weeks prior to mating throughout the gestation and lactation periods. Approximate doses received by the dams for the premating, gestation, and lactation periods were 508–775, 524–551, and 641–1,582 mg/kg bw/day, respectively. For the cross-fostering portion of the study, the pups from ten treated dams were switched with pups from ten control dams. Nursing continued until weaning and the pups were then fed diets consistent with their lactational exposure for 10 weeks. For the switched-diet study, pups from control dams were fed the high-dose diet following weaning, and pups from treated dams were fed control diets after weaning for 10 weeks. Body weights were measured in both experiments.

Pups that were not exposed to DIDP in utero , but were nursed by treated dams, had lower body weights on pnd 14 and 21 than did controls (not exposed to DIDP during any portion of the study). The body weights of the pups remained lower (7–11%) during the 10-week period that they were fed DIDP-treated diets. Absolute and relative right testes weights and absolute left testes weights were reduced in these pups, but a histological examination was not conducted. No changes in body weights were noted for pups that were exposed to DIDP in utero but were then fostered by unexposed dams. In the switched-diet experiment, pups exposed to DIDP during gestation and lactation began to recover body weight and display normal growth patterns once they began to receive control diets at weaning. A slight decrease in body weight gain was observed in pups that were not exposed to DIDP during gestation and lactation but were fed DIDP-treated diets at weaning.

**The summary for Section 3 is located in Section 5.1.3.**II-14Appendix IIAppendix II

II-15 

### 4.0 REPRODUCTIVE TOXICITY

**4.1 Human Data**  There were no human data located for Expert Panel review.

**4.2 Experimental Animal Toxicity**  Exxon Biomedical ( 35 ) conducted a one-generation reproductive range finding assay in rats. The rats were fed diets containing 0, 0.25, 0.5, 0.75, and 1% DIDP. There were no effects on reproductive indices. Toxicity in parents was limited to reduced body weight gain and/or reduced food intake in the 0.75 and 1% dose groups. Based on the results of the range finding assays, doses were selected for a two-generation study.

For the two-generation reproductive study, 30 Crl:CDBR VAF Plus rats/sex/group were fed diets containing 0, 0.2, 0.4, and 0.8% DIDP for 10 weeks prior to mating and during the mating period ( 35 ) (Table WEB-3). Treatment of the females continued through gestation and lactation. Authorestimated doses for the premating period were 103–198, 211–405, and 427–781 mg/kg bw/day for males and 127–203, 253–416, and 508–775 mg/kg bw/day for females. Doses received by females during the gestation and lactation periods were estimated at 131–149, 262–287, and 524–551 mg/ kg bw/day and 172–361, 359–734, and 641–1582 mg/kg bw/day, respectively. Body weight and food intake were recorded weekly and estrous cycles were evaluated. Parental males were killed after mating and females were killed at weaning. A histological examination was conducted for reproductive and other key organs (testes fixed in Bouin’s). Primordial oocytes were counted in control and high-dose females. Sperm count, morphology, and motility were evaluated in males. F 1 pups were selected for mating at weaning and were fed diets with the same DIDP concentration as parental rats. Estimated doses for the F 1 rats were 117–216, 229–437, and 494–929 mg/kg bw/ day in males and 135–218, 273–433, and 566–927 mg/kg bw/day in females during the premating period. Estimated dose levels for F 1 females during gestation and lactation were 135–152, 262–297, and 574–611 mg/kg bw/day and 162–379, 334–761, and 637–1,424 mg/kg bw/day, respectively. Vaginal opening and preputial separation were examined only in F 1 pups that were selected for mating. All other details for the F 1 mating experiment were the same as those for the first generation study.

Similar systemic effects were observed in the F 0 and F 1 adults. Weight gain and food intake were reduced in high-dose F 0 and F 1 females during the lactation period. Kidney to body weight ratios were increased in all treated males and mid- and high-dose females of both generations. Liver to body weight ratios were increased in mid- and high-dose parental rats from both generations. Histological effects included dilated renal pelves in high-dose F 1 males and renal casts observed mostly in high-dose F 0 and F 1 males. In the liver, centrilobular or diffuse hypertrophy and eosinophilia were noted in all treated parental rats of both generations. Mucosal erosion was also observed in the stomach of the mid- and high-dose F 0 females. Thymus atrophy (possibly related to decreased weight gain) was observed in high-dose F 0 and F 1 females. The length of estrous cycles was reduced in F 0 females of the high-dose group. In F 0 males, there was a significant, but small and non-dose related, decrease (<1.4%) in normal sperm in all treated groups. However, in F 1 rats there were no effects on estrous cycle length or sperm morphology. There were no effects on F 0 andII-14Appendix IIAppendix II

II-15 F 1 mating, fertility, fecundity, and gestational indices. There were no lesions in the reproductive organs of F 0 and F 1 males and females and no differences in primordial oocyte or sperm counts. The decrease in absolute uterine weight and absolute and relative ovary weight in high-dose F 0 females and increases in relative weights of epididymis in mid- and high-dose males and testes in high-dose males were considered incidental due to a lack of histological effects.

In F 1 rats, there were no adverse effects on mating, fertility, fecundity, and gestational indices. There were no lesions in the reproductive organs of males and females and no differences in primordial oocyte or sperm counts. Increases in relative weights of epididymis and seminal vesicles in mid- and high-dose F 1 males and testes in high-dose males were considered incidental due to a lack of histological effects.

Developmental effects including decreased pup weight gain in the one-generation study and decreased pup weight gain and increased pup mortality in the two-generation study are discussed in detail under Section 3.0.

In a second two-generation reproductive study, 30 Crl:CDBR VAF Plus rats/sex/group were fed diets containing 0, 0.02, 0.06, 0.2, and 0.4% DIDP for 10 weeks prior to mating and during the mating period ( 36 ) (Table WEB-4). Treatment of the females continued through gestation and lactation. Author-estimated doses for the premating period were 12–23, 33–68, 114–225, and 233– 453 mg/kg bw/day for males and 14–21, 40–58, 139–202, and 274–406 mg/kg bw/day for females. Doses received by females during the gestation and lactation periods were estimated at 13–15, 39–43, 127–147, and 254–295 mg /kg bw/day and 19–37, 57–112, 178–377, and 356–744 mg/kg bw/day, respectively. Body weight and food intake were recorded weekly. Parental males were killed after mating and females were killed at weaning. F 1 pups were examined for survival and growth during the lactation period. On pnd 4 litters were culled to four rats/sex. One F 1 pup/sex/ litter was killed and necropsied on pnd 21. Another F 1 pup/sex/litter was selected for mating and at weaning was fed a diet with the same DIDP concentration as parental rats. Estimated doses for the F 1 rats were 32, 94, 313, and 635 mg/kg bw/day in males and 32, 95, 313, and 645 mg/kg bw/day in females during the first 2 weeks post-weaning and 11–26, 33–76, 114–254, and 235–516 mg/kg bw/day in males, and 14–25, 41–77, 137–266, and 271–524 mg/kg bw/day in females during the premating period. Estimated dose levels for F 1 females during gestation and lactation were 13–15, 38–44, 134–151, and 256–286 mg/kg bw/day and 19–40, 52–114, 166–352, and 356–747 mg/kg bw/day, respectively.

The only systemic effects observed in F 0 and F 1 adults were increases in liver and kidney weights at the two highest doses as illustrated in Table WEB-4. In both generations of parental rats, there were no effects on mating, fertility, fecundity, or gestational indices at any dose level. F 1 and F 2 pups did not experience differences in the age of vaginal opening. The age of preputial separation was similar to controls in all F 1 pups but increased by 1.2 days in the high-dose F 2 pups; this modest change was not considered biologically significant by the authors. A fertility NOAEL of 0.4% (233–635 [M] and 271–645 [F] mg/kg bw/day) was selected by the authors.

Developmental effects including decreased pup weight gain and increased mortality were observed and are discussed in detail under Section 3.0.II-16Appendix IIAppendix II

II-17 **Mode of Action** The estrogenic activity of DIDP has been examined using a battery of short-term in vitro and in vivo assays. Several studies have examined the ability of selected phthalate esters to compete with labeled estradiol (E2) for binding to the estrogen receptor (ER). Sources of ER protein included rat uterine cytosol ( 37 ), rainbow trout hepatic cytosol ( 38 ), recombinant human ERs (rhER) overexpressed in SF9 insect cells using the baculovirus system ( 39, 40 ) and rainbow trout ERs expressed in yeast ( 41 ). Triated E2 was used in the tissue cytosol binding assays while a high affinity fluorescent E2 derivative was used in the rhER binding assays. Selected phthalate esters have been examined in a number of in vitro gene expression assays systems. The assays have used stably transfected cells ( 37 ), transiently transfected cells ( 37, 38 ), yeast based assays ( 37, 41-43 ) and vitellogenin induction in rainbow trout hepatocyte cultures ( 41 ). DIDP did not compete with tritiated estradiol for binding to the rat uterine cytosolic estrogen receptor and did not induce the transcription of estrogen dependent genes ( 37, 43 ). DIDP, in contrast to the positive control estradiol, did not significantly induce an in vivo vaginal cornification response or increase in uterine weight at any of the concentrations tested (20, 200, and 2,000 mg/kg bw/day) over the course of a 5-day experiment using immature and adult ovariectomized Sprague Dawley rats ( 37 ). The lack of nipple retention and a normal anogenital distance in male offspring of rats exposed to DIDP at up to 295 mg/kg bw/day during gestation suggests a lack of antiandrogenic activity at that dose ( 36 ).

**The summary for Section 4 is located in Section 5.1.4.**II-16Appendix IIAppendix II

II-17 

### 5.0 DATA SUMMARY & INTEGRATION

**5.1 Summary** 

5.1.1 Human Exposure DIDP, a complex substance of branched, predominantly C-10 isomers, is a general-purpose plasticizer for flexible PVC with a broad range of applications. It is widely used in construction and in general consumer product markets. Uses that result in general population exposure include artificial leather (shoes, gloves, clothing) and pool linings. DIDP is also used in children’s vinyl toys. It has limited use in food packaging and is not used for medical applications ( 1 ).

There are no regulatory occupational limits, but manufacturers are reported to recommend 5mg/m 3

, the ACGIH value for DEHP ( 1 ). Environmental monitoring data are scant. However, the monitoring data for DIDP in air, drinking water, and surface and ground waters have usually yielded negative results (i.e., concentrations below detection limits). In the few studies of food and infant formula, the levels of DIDP have been at or below the detection limit (0.01–0.1 mg/kg). Exposure through mouthing of toys is a unique circumstance. While no in vitro or in vivo data on DIDP leaching from toys are available, it is reasonable to postulate exposures several-fold higher than the general population in infants and toddlers who mouth DIDP-containing products. By analogy to DINP estimates, these exposures may be an order of magnitude higher for infants and young toddlers than exposures to older children and adults.

5.1.1.1 Utility of Data to the CERHR Evaluation The Expert Panel believes it is reasonable to assume, based on the physicochemical characteristics of DIDP and existing, though limited, monitoring data, that the general population exposure level to DIDP is lower than to DEHP, which is estimated at 3–30 μ g/kg bw/day (10). Exposure in children could represent an important exception to the propriety of extrapolating DIDP exposures from DEHP data. Potential unique exposures from mouthing toys and other objects that may contain DIDP permit only modest confidence in the adequacy of using DEHP estimates for estimating DIDP exposure in infants and toddlers.

5.1.2 General Biological and Toxicological Data
**General Toxicity.** Human data were not found for the categories presented in this section.

General toxicity studies for DIDP consist of a 21-day dietary study in rats, two 4-week dietary studies in rats, two 90-day dietary studies in rats, a 90-day dietary study in dogs, and a 2-week inhalation study in rats. The NOAELs, LOAELs, and effects from the feeding studies are listed in Table 4. Young adult rats (6 weeks old) were used in the 21- and 28-day feeding studies conducted by BIBRA ( 11, 12 ). The ages of rats in the other studies were not given, but body weights indicate they were equivalent to young adults. Animal age and weight were not available for the BASF rat studies. With the exception of one 28-day study in rats ( 13 ), histological examinations of testes were conducted. As noted, testicular histology was unaffected at doses up to 2,100, 1,287, and 586II-18Appendix IIAppendix II

II-19 mg/kg bw/day in the 21-day, 28-day, and 90-day studies, respectively. Increases in liver weight were consistently observed in all studies. The increases in liver weight were accompanied by biochemical evidence of peroxisomal proliferation at doses of 304 and 353 mg/kg bw/day in the 21-day and 28-day studies, respectively, conducted by BIBRA ( 11 ) and Lake ( 12 ). Additional liver effects that were reported in the 21-day rat study ( 11 ) included change in serum triglycerides and cholesterol and a change in hepatocyte cytoplasm staining properties. Increases in kidney weight and thyroid activity (as indicated by histological observations of follicle size, colloid, and epithelium) were only reported in the 90-day feeding study in rats at a dose of 586(M)

− 686(F) mg/kg bw/day.

General systemic effects were also studied in young adult dogs fed diets with up to 307(M)

− 320(F) mg/kg bw/day for 90 days. Hepatocellular swelling and vacuolization was observed in dogs at 77

− 320 mg/kg bw/day; effects were not observed at 15 mg/kg bw/day. Lesions were not observed in testes.

In an inhalation study, rats (ages not specified) were exposed to 505 mg/m 3 DIDP for 2 weeks ( 17 ). There were no systemic effects observed and toxicity was limited to local inflammatory changes in the lung.

The liver was identified as a target organ due findings in rats and dogs that were qualitatively consistent (e.g., increases in liver weight and the observance of vacuolated hepatocytes). As noted in Table 4, the NOAELs are fairly consistent for all dietary rat studies (116–264 mg/kg bw/day).

**Toxicokinetics.** DIDP administered orally to adult male rats is rapidly but incompletely absorbed (~56% at a dose of 0.1 mg/kg bw) and rapidly excreted via urine and feces with no accumulation in tissues ( 22 ). There was evidence of dose-limited absorption since ~46 and ~17% were absorbed after doses of 11 and 1,000 mg/kg bw, respectively. The data suggest partial saturation of the metabolism of DIDP to the monoester in rat intestines within the dose range administered in the study (0.1

− 1,000 mg/kg bw). Saturation of intestinal esterase and pancreatic lipase ma y result in absorption of some unmetabolized parent compound, but no DIDP was detected, suggesting that most of the parent compound was excreted in the feces. Distribution to tissues was proportional to absorbed dose,suggesting that accumulation is not a factor. The major metabolites are the monoester and its sidechain oxidation products as well as phthalic acid. Dermal uptake over a 7-day period was quite low (

∼ 2%) in the rat ( 18, 19 ). In vitro studies with DEHP using human and rat skin ( 44 ) revealed that absorption was slower through human skin. Thus, it is reasonable to assume that dermal absorption of DIDP in humans would not be greater than that seen in rat dermal studies. Inhalation exposure of adult male Sprague Dawley rats to a single 6-hour dose of 91 mg/m 3 revealed initial high concentrations in lung with 27% of the concentration (radioactivity) still present after 72 hours. Distribution to other tissues was followed by rapid excretion via urine and feces ( 17 ).

**Genetic Toxicity**

. OECD ( 28 ) recently concluded that DIDP is a non-genotoxic agent based on negative results in bacterial mutation assays, a mouse lymphoma assay, and a mouse micronucleus assay. In a subsequent publication negative results were obtained in the mouse lymphoma mutation and cell transformation assays conducted by Barber ( 29 ).II-18Appendix IIAppendix II

II-19 Table 4. Summary of NOAELs and LOAELs and Major Effects in General Toxicity Studies

**Protocol and DIDP Doses (mg/kg bw/day)**  **NOAEL (mg/kg bw/**  **day) LOAEL**  **(mg/kg bw/day)**

**and Effects Major effects**  **at higher doses**

21-day repeat-dose dietary study in Fischer 344 rats. 6 weeks old at start of study, 5 rats/sex/group.
Doses

M: 0, 304, 1,134, 2,100 F: 0, 264, 1,042, 1,972 ( 11 ) M: None
F: 264 M: 304; F: 1042 ↑ Liver weight. Peroxisomal proliferation. Basophilic liver changes (F). ↑ Liver weight. Peroxisomal proliferation. ↓ Serum triglycerides and

cholesterol. Basophilic and eosinophilic

liver changes.

No testicular lesions.

28-day repeat-dose dietary study in Fischer 344 rat. 6 weeks old at start of study, 5 male rats/group. Doses: 0, 25, 57, 116, 353, 1,287 ( 12 ) 116 353 ↑ Liver weight. Peroxisomal proliferation. ↑ Liver weight. Peroxisomal proliferation.
No testicular lesions.

28-day repeat dose dietary study in Sprague-Dawley Rats. Age not known, 20/sex/group.
Doses

M: 0, 600, 1,250; F:1,100, 21,00 ( 13 ) None M: 600; F: 1,100 ↑ Liver weight. ↑ Liver weight.

90-day repeat dose dietary study in Sprague-Dawley rats. Age not known, 20/sex/group.
Doses

M: 0, 55, 100, 200, 400 F: 0, 60, 120, 250, 500 ( 14 ) M: 200
F: 120 M: 400 ; F: 250 ↑ Liver weight. ↓ Weight gain in males. ↑ Liver weight. ↓ Weight gain in males.
No testicular or ovarian lesions.

90-day repeat dose dietary study in Charles river CD rats Assume young adult based on body weight, 10/sex/group.
Doses

M: 0, 28, 170, 586 F: 0, 35, 211, 686 ( 15 ) M: 170
F: 211 M: 586; F: 686 ↑ Liver weight. ↑ Kidney weight (M). ↑ Thyroid activity (slight

histologic evidence).

No testicular lesions. No higher doses.

90-day repeat dose dietary study in young adult dogs, 3/sex/group.
Doses

M: 0, 15, 77, 307 F: 0, 16, 88, 320 ( 16 ) Sample size inadequate for evaluation of

NOAEL M: 77; F: 88 ↑ Liver weight, histological

effects. ↓ Body weight. ↑ Liver weight, histological

effects.

No testicular lesions.II-20Appendix IIAppendix II

II-21 5.1.2.1 Utility of Data the CERHR Evaluation The oral subchronic studies in rat and dog are adequate for the evaluation of general toxicity induced by DIDP and indicate that the liver is a target organ. Some studies were conducted according to GLP standards and relevant exposure routes were utilized. Although sample sizes tended to be small in these studies, the results are generally consistent and reproducible, lending credence to the adequacy of the dataset. A modest concern is that rodent testes were preserved in formalin, which can lead to histopathological artifacts that may obscure subtle structural changes. However, reproductive organs in a two-generation rat study (discussed under Section 5.1.4) were preserved in Bouin’s fixative and the histological observations observed were consistent with those from the general toxicity studies. Testes evaluation in the 90-day dog study was based on sections from Bouin’s-fixed tissue. Peroxisomal proliferation was not examined in the 90-day exposure studies; however, it was present at 21 and 28 days in rat studies.

There is adequate general toxicokinetic data for DIDP, consisting of absorption, distribution, metabolism, and excretion, over a range of oral doses in the rat. There is also data on dermal and inhalation exposure in rats. While studies of toxicokinetics in humans have not been located, the DIDP toxicokinetic data in rats are consistent with the large body of data on phthalates that includes data on rodents and primates. It is reasonable to assume that the DIDP rodent data is relevant to humans.II-20Appendix IIAppendix II

II-21 5.1.3 Developmental Toxicity Human data were not located for Expert Panel review.

Two published prenatal developmental toxicity studies in rats were available for DIDP ( 31, 34 ). The protocols for the 2 studies were similar and included dosing of dams by gavage on gd 6–15 with sacrifice and evaluation of fetuses on gd 20–21, although the group sizes differed. Developmental toxicity was also evaluated in a one-generation and in 2 two-generation toxicity studies ( 35, 36 ). The effects on pups from these studies are discussed below and summarized in Table 5; the reproductive effects from the one-generation and two-generation studies are described in Section 5.1.4.

Hellwig et al. ( 34 ) tested DIDP (CAS no. 26761-40-0) in Wistar rats (10/group) at doses of 0, 40, 200, and 1,000 mg/kg bw/day. Maternal toxicity was observed at the 1,000 mg/kg bw/day group and included increased liver weights and vaginal hemorrhage. Fetal variations per litter were increased in the 200 and 1,000 mg/kg bw/day dose groups. These included increased rudimentary cervical ribs and increased accessory 14 th ribs at 1,000 mg/kg bw/day; specific types of variations were not reported for the 200 mg/kg bw/day group. Hellwig et al. ( 34 ) reported “no substancerelated effects” in dams or fetuses at doses up to 200 mg/kg bw/day, the middle dose tested. The Expert Panel did not find that the data supported a developmental NOAEL at 200 mg/kg bw/day given the reported statistically significant increase in total fetal variations at this dose, and agreed that the NOAEL is 40 mg/kg bw/day.

Of the two prenatal toxicity studies reviewed by the Expert Panel, Waterman et al. ( 31 ) was more informative due to the number of animals per test group (n=25) and completeness of data reported. Waterman et al. ( 31 ) tested DIDP (CAS no. 68515-49-1) in Sprague-Dawley rats (25/group) at doses of 0, 100, 500, or 1,000 mg/kg bw/day. Maternal toxicity at the highest dose consisted of decreased food consumption and weight gain. The effects on the offspring were presented as percent affected fetuses and percent affected litters. The percent fetuses with rudimentary cervical ribs was significantly increased at the two highest doses with a dose-related increase in litter incidence significant at the highest dose. There was a similar pattern of effect for accessory 14 th ribs. Waterman et al. ( 31 ) interpreted their results as indicating a LOAEL for maternal and developmental toxicity at 1,000 mg/kg bw/day and a NOAEL of 500 mg/kg bw/day. The Expert Panel concurred with the maternal NOAEL but selected a developmental NOAEL of 100 mg/kg bw/day based on the significant incidence of cervical and accessory 14 th ribs. A reanalysis of these Waterman et al. data by the study sponsor (see Section 3.2), using the GEE approach to the linearized model ( 32 ), provided results that are consistent with the Expert Panel interpretation.

The sponsor also provided benchmark doses at the 5 and 10% excess risk level, based on a multiplicative (or ‘extra’) excess risk function. At the 5% excess risk level, the benchmark doses (and their 95% lower confidence limits estimated by bootstrap methods) were estimated as 188 (169), 258 (238), and 645 (515) mg/kg bw/day for rudimentary lumbar ribs, skeletal variants, and supernumerary cervical ribs, respectively.

The Expert Panel noted that developmental toxicity was observed in the two rat studies where thereII-22Appendix IIAppendix II

II-23 was prenatal exposure and pups were examined just prior to birth. Developmental toxicity was also observed in both generations of the two-generation study in rats discussed below. In both prenatal studies, the skeletal system was the target for effects causing an increased incidence of cervical ribs and accessory 14 th (lumbar) ribs. While effects at both sites are relevant to an assessment of development, the effect on cervical ribs is of greater toxicological concern. Cervical ribs are seen infrequently in controls, but more importantly, their presence may indicate a disruption of gene expression. In addition, some scientists express concern that cervical ribs may interfere with normal nerve function and blood flow. Rib responses were identical at the common dose of 1,000 mg/kg bw/day in the 2 studies. In the study where there was a larger group size (n=25), the litter incidence at this dose for each effect (cervical and lumbar) achieved statistical significance. In this same study, when incidence was expressed on a percent fetus basis (the proper term for analysis

 percent affected fetuses per litter

 was not reported) statistical significance was observed for each effect at the two highest doses. A numeric trend of increased incidence with increased dose was seen at all doses. In the study with fewer maternal rats per dose group (n=7

− 10), an increase in the incidence of hydroureter and of dilated renal pelves occurred in all treatment groups. This effect is at least indicative of a delay in maturation and while not clear in the publication, is thought to account partially for the reported increase in affected fetuses per litter with variation that achieved statistical significance at the two highest doses. The Panel further noted that this urinary tract effect occurred in the absence of reduced fetal weight; the absence of reduced fetal weight, which is usually a corollary to the urinary tract effect, provides a rationale for assuming maturational delay. The Panel further notes that LOAELs of 500 and 200 mg/kg bw/day and NOAELs of 100 and 40 mg/kg bw/ day from these studies are reasonably consistent, the differences most likely reflect differences in dose selection between the two studies. Finally, it is noted that LOAELs for developmental toxicity occur at doses at which there were no demonstrable maternal effects.

Developmental effects were also observed in 2 two-generation reproductive toxicity studies. Details of the study procedures are addressed in Section 5.1.4. In the fi rst study, rats were fed diets with 0, 0.2, 0.4, or 0.8% DIDP for 10 weeks prior to mating and throughout gestation and lactation ( 35 ). Hepatic hypertrophy and eosinophilia were observed in F 1 and F 2 male and female pups in the midand high-dose groups. Postnatal body weight gains were reduced in high-dose F 1 pups (pnd 0, 7, 14, and 21 for both sexes and pnd 4 for males) and F 2 pups (pnd 1, 4, 7, 14, and 21 for both sexes and pnd 0 for males). A reduction in postnatal survival was observed in F 1 pups of the high-dose group on pnd 0 and 4. In F 2 pups, postnatal survival was reduced on pnd 1 and 4 in all treatment groups and also on pnd 7 and 21 in the high-dose group. This increase in pup mortality was not observed in the one-generation range-finding study, but pup body weights were reduced in the three highest dose groups ( 35 ). Because a NOAEL could not be identified due to increased pup mortality in all dose groups, the study was repeated with lower doses of 0, 0.02, 0.06, 0.2, and 0.4% DIDP in the diet ( 36 ). No developmental effects were observed in the F 1 pups. However, increased mortality was noted in the F 2 pups of the two highest dose groups on pnd 1 and 4. Reductions in pup body weight gain were also noted for F 2 pups in the 0.2% dose group (females on pnd 14 and males on pnd 35) and 0.4% dose group (females on pnd 14 and 21, and males on pnd 14, 28, and 35). Hormonally-mediated endpoints such as anogenital distance and nipple retention in males were not observed at doses up to 0.4% in diet. Maternal effects were limited to increased liver weight with mild histological effects.II-22Appendix IIAppendix II

II-23 Cross-fostering and switched-diet satellite studies with rats fed the 0.8% diet indicated that lactational exposure is a meaningful factor in the reduction of body weight gain in pups ( 35 ). The data are sufficient to conclude that DIDP, administered through diet, is a developmental toxicant in rats based on reduced fetal survival and body weight observed in two studies. A developmental NOAEL of 0.06% (38–44 and 52–114 mg/kg bw/day during pregnancy and lactation, respectively) was identified by the study authors.

A screening-design study in mice ( 30 ), where an oral gavage dose of 9,650 mg/kg bw/day was administered on gd 6–13, did not report any developmental or maternal toxicity through pnd 3. This study is insufficient to conclude that DIDP is not a developmental toxicant in mice since a full teratological examination was not performed. It does indicate that a dose almost 10-fold greater than that which caused effects in rats does not affect pregnancy outcome or early postnatal survival and growth in mice.

5.1.3.1 Utility of Data to the CERHR Evaluation There are adequate data available in rats to determine that prenatal oral exposure to DIDP results in developmental toxicity. The results of the Waterman et al. ( 31 ) and the Hellwig et al. ( 34 ) studies were remarkably consistent and included increases in lumbar and cervical ribs. In addition, the effective dose levels were similar. The data from the 2 two-generation dietary studies are sufficient to demonstrate an effect on postnatal survival and growth.II-24Appendix IIAppendix II

II-25 **Table 5: Summaries of NOAELs and LOAELs and Major Effects in Developmental Toxicity Studies**

**Protocol and Study NOAEL**  **[Benchmark Dose ED**  **05 ]**  **(mg/kg bw/day) LOAEL (mg/kg bw/day)**  **Developmental Effects Observed at Higher**  **Dose Levels Maternal**  **Developmental**

Prenatal gavage study in Wistar rats. 10/group received 0, 40, 200, or 1,000 mg/kg bw/day on gd 6–15. Dam and pups exam

ined in late gestation. ( 34 ) 200 (maternal) 40 (developmental***) 1,000

↑ Liver weights

and vaginal hemorrhage. 200

↑ Variations. (No specific type of variation reported.) ↑ Variations (cervical and lumbar ribs).

Prenatal gavage study in Sprague-Dawley rats. 25 per group received 0, 100, 500, or 1,000 mg/ kg bw/day on gd 6–15. Dams & pups examined in late gestation. ( 31 ) 500 for maternal

100 (developmen

tal***) [MLE(95%LCL): 258 (238) for skeletal variants, 188 (169) for lumbar ribs, 646 (515) for cervical ribs.] 1,000

↓ Weight gain. 500

↑ Fetuses with

variations (lumbar and cervical ribs). ↑ Fetuses and litters with variations (lumbar and cervical ribs).

Two-generation repro

ductive dietary study in Crl:CDBR, VAF Plus
rats. 30 dams/group were fed diets with 0, 0.2, 0.4, or 0.8% DIDP from 10 weeks prior to mat

ing through gestation (131

− 152, 262

− 297, 524

− 611 mg/kg bw/ day*) and lactation 162

− 379, 334

− 761, 637

− 1,582 *). ( 35 )** None for maternalor developmental 131

− 379

Hepatocyte enlargement. 131

− 379

↓ Postnatal survival

in F 2 . ↓ Postnatal survival in F 1 and F 2 . ↓ Postnatal weight gain

in F 1 and F 2 .II-24Appendix IIAppendix II

II-25 **Table 5 (continued)**

**Protocol and Study NOAEL**  **(mg/kg bw/day) LOAEL (mg/kg bw/day)**  **Developmental Effects Observed at Higher**  **Dose Levels Maternal**  **Developmental**
Two generation repro

ductive dietary study in Crl:CDBR, VAF Plus
rats. 30/group were fed diets with 0, 0.02, 0.06, 0.2, or 0.4% DIDP from 10 weeks prior to mating through gesta

tion (13

− 15, 38

− 44, 127

− 151, or 254

− 295 mg/kg bw/day*) and lactation (19

− 40, 52

− 114, 166

− 377, 356

− 747*). ( 36 )** 38–114 for Maternal and developmental 127–377

↑ Liver weight. 127–377

↓ Postnatal survival

in F 2 . ↓ Decreased weight

gain in F 2 . ↓ Postnatal survival in F 2 . ↓ Decreased weight

gain in F 2 .

Prenatal gavage toxicity screening assay in CD-1 mice. 50 dams/group received 0 or 9,650 mg/kg bw/ day on gd 6

− 13. Dams and pups evalu

ated on pnd 3 for litter size and survival and body weight changes only. ( 30 ) 9,650 for maternal and developmental.

(Note – there was no examination of fetal variations or malfor

mations.) No higher doses. No higher doses. No higher doses.

* Combined doses for F 0 and F 1 dams during gestation and lactation. ** Only maternal and developmental effects were listed in this Table. Reproductive and male systemic effects are listed in Table 6. *** NOAEL selected by Expert Panel is lower than study author’s selection.II-26Appendix IIAppendix II

II-27 5.1.4 Reproductive Toxicity Human data were not located for Expert Panel review.

Structural and functional reproductive effects were examined in a one-generation (dose setting) and 2 two-generation studies in rats that included in utero exposure for the duration of pregnancy ( 35, 36 ). In the one-generation study, rats were administered dietary levels of 0, 0.25, 0.5, 0.75, and 1% DIDP. In the two-generation studies, rats were administered dietary levels of 0, 0.2, 0.4, and 0.8% DIDP or 0, 0.02, 0.06, 0.2, and 0.4% DIDP ( 35, 36 ). In the two-generation studies, there were no effects on F 0 or F 1 mating, fertility, fecundity, and gestational indices at doses up to 427

− 929 and 508

− 927 mg/kg bw/day in males and females, respectively. A small, non dose-related decrease in normal sperm (<1.4%) was seen in all treated F 0 males and a reduced length of estrous cycles occurred in F 0 females that received the highest dose, but those effects were not observed in the F 1 rats. There were no histologic lesions in the reproductive organs of F 0 or F 1 males and females and no differences in primordial oocyte or sperm counts. The lack of effects on reproductive function was consistent with effects observed in the one-generation range-finding study. In the two-generation reproductive toxicity study with higher doses, systemic effects in parental rats included hepatocyte hypertrophy at all dose levels, increased kidney weights in low-dose males and all mid- and high-dose animals, and dilated renal pelves and renal casts in high-dose males ( 35 ). Developmental effects included hepatic hypertrophy and reduced postnatal survival and are discussed in detail in Section 5.1.3. Parental systemic and developmental toxicity were similar to those described in the second two generation reproductive toxicity study ( 36 ).

DIDP did not appear to have effects on male reproductive tract development or function. An increase in seminal vesicle to body weight ratio in F 1 males of the 0.4% group and epididymis to body weight ratio in F 0 and F 1 males at the 0.4% dose was not considered adverse because reproductive function was unaffected and there were no histopathological effects ( 35 ). Thus, the highest dose of 0.8% (M: 427

− 929 mg/kg bw/day and F: 508

− 927 mg/kg bw/day) was identified as the NOAEL for reproductive toxicity.

**Mode of Action** DIDP exhibited no activity in in vitro assays that measured binding of phthalates to rat uterine cytosolic estrogen receptors and in an assay of estrogen-induced gene expression ( 37, 43 ). The monoester of DIDP was not tested in vitro

. In vivo assays demonstrated that DIDP does not increase uterine wet weight or vaginal epithelial cell cornification in immature or mature ovariectomized rats ( 37 ). The lack of nipple retention and a normal anogenital distance in male offspring of rats exposed to DIDP at up 295 mg/kg bw/day during gestation suggests a lack of antiandrogenic activity at that dose ( 36 ).

5.1.4.1 Utility of Data to the CERHR Evaluation Data are sufficient to indicate that oral DIDP exposures are not associated with detectable effects on reproduction at doses up to 427

− 929 mg/kg bw/day in male and 508

− 927 mg/kg bw/day in female rats. Testicular lesions were not observed in histological examination of testes in dogs exposed to doses of 307 mg/kg bw/day in a 90-day study. The data from the two-generation studies were collected utilizing a protocol acceptable to the US, EU, and other OECD countries. They wereII-26Appendix IIAppendix II

II-27 performed in accordance with GLP requirements. Reproductive organs were preserved in Bouin’s fixative, a method which reduces histological artifacts. One of the studies included an evaluation of hormonally-mediated postnatal effects that were found to be the most sensitive indicators of toxicity for other phthalates. Thus, the data provide a valuable database for evaluating reproductive toxicity potential in rats.

**Table 6: Summaries of NOAELs, LOAELs, and Major Effects in Reproductive Toxicity Studies**

**Protocol & Study NOAEL**  **(mg/kg bw/day) LOAEL (mg/kg bw/day)**  **and Effects Effects**  **Observed at Higher Dose**  **Levels**
**Reproductive Systemic**  **Reproductive**

One-generation reproductive screen

ing assay in WU rats. 10 pairs/group received 0, 250, 500, or 1,000 mg/kg bw/day by gavage from 2 weeks prior to mating for a total of 29 days (males) or until pnd 6 (females). (48) Reproductive: 500 Systemic:

500 1,000

↓ Fertility
Testicular lesions ↓ Litter size 1,000

↓ Weight gain No higher doses in study

One-generation dietary reproductive toxicity assay in Wistar rats with 12 males and 24 females/group. Males were treated 10 weeks prior to mat

ing with 0, 108, 206, or 418 mg/kg bw/day. Females were treated from 2 weeks prior to mating (0, 106, 217, or 446 mg/kg bw/day), through gestation (0, 116, 235, or 458 mg/kg bw/day) and lactation (0, 252, 580, or 1,078 mg/kg bw/day). (50) Reproductive: 418 (M); 446 (F) Systemic:

206 (M); 217 (F) No structural or functional effects at any dose 418 (M); 446 (F)

↓ Weight gain (F) ↑ Liver weight No higher doses in study

* Doses during the premating period – combined for F 0 and F 1 rats ** Only effects in parental rats and effects in the reproductive system are listed. Developmental effects are listed in Table 5. *** Doses during the premating period and first 2 weeks postweaning for F 1 rats - combined for F 0 and F 1 rats.II-28Appendix IIAppendix II

II-29 **5.2 Integrated Evaluation**  DIDP is a complex substance of branched, predominantly C-10 isomers. There are no human data from which to assess the health effects associated with DIDP exposure; studies of DIDP toxicity are limited to laboratory animals. In the absence of human data to the contrary, it is assumed that the effects observed in laboratory animals are relevant to humans.

Based upon the physicochemical similarities between DIDP and DEHP, and on limited DIDP monitoring data, general population exposure is expected to be lower than that of DEHP, which is estimated at 3

− 30 μg/kg bw/day. It is reasonable to presume that humans would be exposed primarily through the oral route. Although data are scant, the ingestion of DIDP through food does not appear to be common. Children may have higher levels of exposure to DIDP than adults because infants and small children mouth toys and other objects that may contain DIDP which can migrate into saliva and be swallowed. There is no use of DIDP in medical devices, therefore intravenous exposure does not occur.

Orally-administered DIDP is metabolized by intestinal luminal enzymes and the resulting metabolites are absorbed into the blood and further metabolized or conjugated and quickly excreted into urine or feces. Persistence or accumulation in the body is not expected. Toxicokinetic studies in rats have demonstrated that DIDP has limited dermal absorption and does not persist or accumulate in the body.

There are data available in rodents from which to evaluate developmental and reproductive effects associated with oral DIDP exposure. Developmental studies in rats include assessment of prenatal exposure on prenatal effects. Postnatal developmental effects following prenatal exposure have also been assessed using endpoints that have been adversely affected in studies with other phthalates. Two prenatal gavage exposure studies in rats with treatment of dams from gd 6

− 15 did not cause structural malformations but did consistently demonstrate developmental toxicity (increased fetal cervical and lumbar ribs) at doses of 200

− 500 mg/kg bw/day and higher. The more robust of the two studies was determined by the Expert Panel to have a maternal NOAEL of 500 mg/kg bw/day and a developmental toxicity NOAEL of 100 mg/kg bw/day , while a second study determined a developmental NOAEL of 40 mg/kg bw/day. Developmental toxicity was observed and replicated in 2 two-generation reproductive dietary studies in rats where adverse effects on pup growth or survival were observed at gestational doses of 127–151 mg/kg bw/day and higher and a lactational dose of 166

− 377 mg/kg bw/day and higher; the developmental NOAEL is in the range of 38–44 mg/kg bw/day (gestational) and 52

− 114 mg/kg bw/day (lactational). A prenatal exposure-screening study in mice in which an oral gavage dose of 9,650 mg/kg bw/day was administered did not report any developmental or maternal toxicity. While insufficient to conclude that DIDP is not a developmental toxicant in mice, it does indicate that a dose that is almost 10-fold greater than that which caused effects in rats does not affect pregnancy outcome or early postnatal survival and growth in mice.

Reproductive performance and histological effects on sex organs were assessed. Parental doses of up to 0.8% in feed (

∼ 427

− 929 in males and 508

− 927 mg/kg bw/day in females) did not affect fertility or sex organ histology in either the parents or F 1 male or female pups. Sub-chronic studies (21–90 day exposure) gave no gross or histologic evidence of effects on testes at doses up to 2,100II-28Appendix IIAppendix II

II-29 mg/kg bw/day in rats and 307 mg/kg bw/day in dogs. These doses did produce liver hypertrophy, mild evidence of toxicity, and clear signs of peroxisome proliferation in rats. The Expert Panel notes that the liver was consistently identified as the target organ in general toxicity studies with adult rats and in developmental and multigeneration studies. Hepatic effects in offspring exposed in
utero were principally associated with liver enlargement observed at weaning and in adults.

**5.3 Expert Panel Conclusions**  DIDP is used in construction and in general consumer products. DIDP was detected in older surveys of toys, but recent surveys have not detected DIDP in toys. In surveys of retail food samples, DIDP concentrations were below the detection limits. Although data are scant, exposure through food appears to be lower than for DEHP. Therefore, the Expert Panel believes that adult exposure to DIDP will not exceed levels of 3

− 30 μ g/kg bw/day, the estimates derived for DEHP. Exposures to DIDP are likely to be below this level, but the Panel could not quantitate how far below. Occupational exposures could occur through inhalation and dermal contact. Limited studies of occupational exposures suggest that inhalation exposure is below 1 mg/m 3 during production of DIDP and below 2 mg/m 3 during production of PVC. Although estimates of dermal exposure are not available, the Expert Panel is confident that dermal exposure would not result in significant absorption into the body. Exposure of children to DIDP could also occur through contaminated food. However, DIDP has not been detected in surveys of infant formula.

The toxicology database is sufficient to determine that oral maternal exposure to DIDP can result in developmental toxicity to the conceptus. In rats, two prenatal developmental studies have shown effects on the developing skeletal system following oral exposure to DIDP. The NOAEL for these studies was 40

− 100 mg/kg bw/day. In addition, developmental toxicity was noted in two oral twogeneration reproductive toxicity studies in rats. Both studies showed effects on pup survival and growth. These effects may be due to prenatal and/or lactational exposures to DIDP. The NOAELs for the studies were 38

− 44 mg/kg bw/day during pregnancy and 52

− 114 mg/kg bw/day during lactation. Based on the results of the toxicology studies, oral exposure to pregnant humans and oral exposure to children should be examined. To date, the only available oral exposure information is based on the conservative estimate derived for DEHP of 3

− 30 μ g/kg bw/day. The Expert Panel has minimal concern for children and fetuses due to exposure to ambient levels of DIDP. The Expert Panel cannot judge the potential health effects in children from mouthing of objects containing DIDP due to the lack of exposure information. In addition, the Expert Panel cannot judge the potential hazards to unborn children following maternal occupational exposures due to the lack of toxicology data following inhalation exposures and the lack of occupational exposure information.

The oral prenatal developmental toxicity studies and the oral two-generation reproductive toxicity studies have shown no effects on the reproductive system in rats. The Expert Panel noted that the endpoints of reproductive development that have been shown to be sensitive with other phthalates were examined in one of the two-generation reproductive toxicity studies. The NOAEL for reproductive toxicity ranges from 427

− 929 mg/kg bw/day. Therefore, the Expert Panel has minimal concern about DIDP resulting in reproductive toxicity in humans.II-30Appendix IIAppendix II

II-31 **5.4 Critical Data Needs**  Critical data needs are discussed under two categories: experimental studies and human exposure.

**Experimental Studies** The Expert Panel recommends a sequential approach for future studies that would focus on obtaining the most critical information first. Subsequent studies would be dependent upon the results of the initial study. The Panel further recognized that data gathering should be an iterative process and that the recommendations may change as initial tiers of data are gathered. The Expert Panel recommends that the following sequential steps be considered.

A perinatal developmental study by the oral route in a non-rodent species. There are species differences in the developmental toxicity associated with other phthalates. The developmental effects of DIDP have only been examined in the rat and in a mouse screening study. Therefore, there is some uncertainty whether other species would exhibit similar responses and whether the rat is an appropriate model for assessing potential human risk.

**Human Exposure** 1) Human exposure to DIDP has not been well studied; there are no reports of levels in biological materials (blood, urine, etc.), and the environmental data consist primarily of estimates.

2) Patterns of use, expected environmental levels, and vulnerability of exposed population groups should dictate decisions about measuring DIDP in environmental media. For example, deter

mining DIDP exposures in young children is of highest priority, based on the use patterns and vulnerability described above. Workers producing PVC products are a second priority.

3) Collection of biological samples de novo should be accompanied by environmental measure

ments to provide information on exposure sources. Existing biological samples should be uti

lized where available if they can provide useful information about exposure.

4) Although information about exposure of young children is a critical data need, manufacturers of children’s toys should be polled to determine if their products will continue to contain DIDP in the future. If so, an estimate of the DIDP content should be made b y the manufacturer and confirmed by independent studies. Salivary extraction of DIDP itself is important in order to evaluate the exposure directly, and not by use of a proxy (DINP). Better estimates of mouth

ing behavior, especially within the potentially highest risk group of 3

− 12 months, using larger samples of children, are also needed. The initial assessment of DIDP in toys is particularly important because no DIDP was found in a US sample of 35 toys, and the UK studies of 1992 and 1996 reported the same negative result.II-30Appendix IIAppendix II

II-31 

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II-35 

### 7.0 TABLES

7.1 DIDP Developmental Toxicity, Rats

............................................................... ....................... 36 7.2 DIDP Developmental Toxicity, Rats

............................................................... ....................... 37 7.3 DIDP Reproductive Toxicity, Rats

............................................................... .......................... 38 7.4 DIDP Reproductive Toxicity, Rats

............................................................... .......................... 40 7.5 References

............................................................... ............................................................... 42II-36Appendix IIAppendix II

II-37Table 7-1: DIDP Developmental Toxicity, Rats**Species, Strain, and Source** **Experimental Regimen Number** **a Dose** ***Maternal effects Fetal effects** Sprague-Dawley RatWaterman et al. 1999(2)Prenatal developmental toxicitystudy. DIDP administered in oilby gavage on gd 6−15. Sacrificed on gd 21. Dams weighedon gd 0, 6, 9, 12, 15, 18, and21. Maternal uterus and ovarieswere weighed, corpora luteawere counted and implantationsites examined. Fetuses wereweighed, sexed, and examinedfor gross external malformations. Half of the fetuses wereexamined for visceral malformations and the other half for skeletal malformations.25022100NOAELb24500NOAEL↑% Fetuses with cervicalribs (6.2 vs 1%).↑% Fetuses with lumbarribs (21.2 vs 8.2%).241,000↓Weight gain.↓Food Intake.↑% Litters with cervicalribs (41.7 vs 8%).↑% Litters with lumbarribs (95.8 vs 40%).↑% Fetuses with cervicalribs (9.2 vs 1.0%).↑Fetuses with lumbarribs (52 vs 8.2%).*Dose measured in mg/kg/bw/day.aNumber of litters examined.bNOAEL selected by Expert Panel is lower than study author’s selection.↑=Statistically Significant Increase↓=Statistically Significant DecreaseII-36Appendix IIAppendix II

II-37Table 7-2: DIDP Developmental Toxicity, Rats**Species, Strain, and Source** **Experimental Regimen Number** **a Dose** ***Maternal Effects Fetal Effects** Wistar RatHellwig et al. 1997(1)Prenatal developmental toxicity study. DIDP administeredin oil by gavage on gd 6−15.Dams weighed on gd 0, 6, 10,15, and 20 and sacrificed ongd 20. Maternal uteri wereweighed, corpora lutea werecounted and implantationsites examined. Fetuses wereweighed and examined forgross external malformations.Half of the fetuses were examined for visceral malformationsand the other half for skeletalmalformations.100840NENOAELb7200NOAEL↑Fetuses/litter withvariations (38 vs 24%).101,000↑Liver to body weightratios.Vaginal hemorrhage in 3dams.↓Food intake.↑Fetuses/litter withvariations (44 vs 24%).↑Cervical ribs (15 fetusesin 6 litters vs 1 fetuses).↑14thribs (21 fetuses in 8litters vs 1 fetus).*Dose measured in mg/kg/bw/day.aNumber of litters examined.bNOAEL selected by Expert Panel is lower than study author’s selection.↑=Statistically Significant Increase↓=Statistically Significant DecreaseII-38Appendix IIAppendix II

II-39Table 7-3: DIDP Reproductive Toxicity, Rats**Species, Strain, and Source** **Experimental Regimen Number** **a Dose** ***Parental Effects******Offspring Effects Crl:CDBR, VAFPlus RatsExxon Biomedical1997(3)Two-generation reproductivetoxicity study.DIDP administered in feedfor 10 weeks prior to matingat levels of 0, 0.2, 0.4, and0.8%. Males treated throughmating period and femalesthrough gestation and lactation.Body weight and food intakewas measured weekly.Estrous cycles were evaluated.F0dams were killed at theend of lactation and maleswere killed following birth oflast litter.Reproductive and other keyorgans were examined histologically.Primordial oocytes werecounted in females and spermwas evaluated in males.Details of the second generation breeding experiment arelisted on the next page.40030103−198 /127−203 /131−149 /172−361↓Normal sperm in F0(<1.4%).↑Liver hypertrophy in F0.↑Kidney to body weight ratio in F0males.30211−405 /253−416 /262−287 /359−734↓Normal sperm in F0(<1.4%).↑Epididymis to body weight ratio in F0.↑Liver to body weight ratio withhypertrophy in F0.↑Kidney to body weight ratio in F0.↑Stomach lesions in F0females.↑Liver to body weightratio (F) withhypertrophy in F1.Delayed vaginal openingin F1(33.5 vs 32.2days).40427−781 /508−775 /524−551 /641−1,582No effects on F0mating, fertility,fecundity, or gestational indices, noreproductive organ lesions, and noeffect on oocyte or sperm counts at anydose.↓Normal sperm in F0(<1.4%).↓Estrous cycle length in F0.↓Ovary to body weight ratio in F0.↑Epididymis and testes to body weightratio in F0.↓Weight gain in F0during lactation.↑Liver to body weight ratio withhypertrophy in F0.↑Kidney to body weight ratio in F0withhistological changes in males.↑Stomach lesions and thymus atrophy inF0females.↓F1pup birthweight.↓F1pup survival at birthand pnd 4.↑Liver to body weightratio with hypertrophyin F1.Delayed vaginal openingin F1(34.2 vs 32.2days).II-38Appendix IIAppendix II

II-39Table 7-3: DIDP Reproductive Toxicity, Rats (continued)** Species, Strain,****and Source Experimental Regimen** **Number a** **Dose*****Parental Effects******Offspring Effects Crl:CDBR, VAFPlus RatsExxon Biomedical1997(3)Sexual maturation was monitored in F1pups selected forsecond generation breeding.Upon weaning the pups werefed diets with the same DIDPconcentrations as parentalrats. The same parametersexamined in the F0rats wereexamined in the F1rats.30030117–216 /135–218 /135–152 /162–379↑Liver to body weight ratio (F).↑Hypertrophy in F1.↑Kidney to body weight ratio in F1(M).↓F2pup survival on pnd1 and 4.30229–437 /273–433 /262–297 /334–761↑Epididymis and seminal vesicles tobody weight ratio in F1.↑Liver to body weight ratio in F1withhypertrophy.↑Kidney to body weight ratio in F1.↓F2pup survival on pnd1 and 4.↑Liver hypertrophy in F2pups.30494–929/566–927 /574–611 /637–1424No effects on F1mating, fertility,fecundity, or gestational indices, noreproductive organ lesions, and no effecton oocyte or sperm counts at any dose.↑Epididymis, seminal vesicle, and testesto body weight ratio in F1.↓Weight gain in F1during lactation.↑Liver to body weight ratio withhypertrophy in F1.↑Kidney to body weight ratio in F1withhistological changes in males.↑Thymus atrophy in F1females.↓F2pup birthweight.↓F2pup survival on pnd1, 4, 7 and at weaning.Undescended testes in 4pups.↑Liver hypertrophy in F2pups.aNumber of breeding pairs.** Parental effects are discussed in Section 4and offspring effects in Section 3.*Doses in mg/kg bw/day for:Males during premating /Females during premating /Females during gestational period /Females during lactational period.↑=Statistically Significant Increase↓=Statistically Significant DecreaseII-40Appendix IIAppendix II

II-41Table 7-4: DIDP Reproductive Toxicity, Rats**Species, Strain, and Source** **Experimental Regimen Number** **a Dose** ***Parental Effects*******Offspring Effects*****Crl:CDBR, VAFPlus RatsExxonBiomedical 2000(4)Two-generation reproductivetoxicity study.DIDP administered in feed for10 weeks prior to mating atlevels of 0, 0.02, 0.06, 0.2, and0.4%. Males treated throughmating period and femalesthrough gestation and lactation.Body weight and food intakewere measured weekly.F0dams were killed andnecropsied at the end oflactation and males were killedand necropsied after mating.Pups were examined for survivaland sexual maturation.One pup/sex/litter wasnecropsied at pnd 21.Histological examinations werenot conducted.Details of the second generationbreeding experiment are listedon the next page.3003012–23 /14–21/13–15 /19–37NENE3033–68 /40–58 /39–43 /57–112NENE30114–225 /139–202 /127–147 /178–377NENE30233–453 /274–406/254–295 /356–744↑Liver and kidney to body weightratio.No effects on mating, fertility,fecundity, or gestational indicesat any dose.No effects on survival, bodyweight gain, organ weights, anogenital distance, nipple retention,preputial separation, vaginalopening, or malformations.aNumber of breeding pairs.***Parental effects are discussed in Section 4and offspring effects in Section 3.*Doses in mg/kg bw/day for:Males during premating /Females during premating /Females during gestational period /Females during lactational period.**Doses in mg/kg bw/day for:Males during first two weeks postweaning /Males during first two weeks postweaning /Males during premating /Females during premating /Females during gestational period /Females during lactational period.NE=No Effect↓=Statistically Significant DecreaseII-40Appendix IIAppendix II

II-41Table 7-4: DIDP Reproductive Toxicity, Rats (continued)**Species, Strain, and Source** **Experimental Regimen Number** **a Dose** ****Parental Effects*******Offspring Effects*****Crl:CDBR, VAFPlus RatsExxonBiomedical 2000(4)Upon weaning the pups werefed diets with the same DIDPconcentrations as parental rats.The remaining details are asdescribed for the 1stgeneration.3003932 /32 /11–26 /14–25 /13–15 /19–40NENE3094 /95/33–76 /41–77 /38–44 /52–114NENE30313 /313 /114–254 /137–266 /134–151 /166–352↑Kidney to body weight ratio in(M).↑Liver to body weight ratio (F).↓Pup survival on pnd 1 and 4.↓Pup body weight on pnd 14 (F)and pnd 35(M).30635 /645 /235–516 /271–524 /256–286 /356–747↑Kidney to body weight ratio(M).↑Liver to body weight ratio.No effects on mating, fertility,fecundity, and gestationalindices at any dose.↓Pup survival on pnd 1 and 4.↓Pup body weight on pnd 14 ,pnd 21 (F), pnd 28 (M), andpnd 35(M).↑Liver to body weight ratio (F).↑Age of preputial separation(+1.2 days).No effects on anogenital distance,nipple retention, or vaginalopening, and no malformations.See footnotes from first generation breeding experiments.II-42Appendix II 

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2. Waterman SJ, Ambroso JL, Keller LH, Trimmer GW, Nikiforov AI, Harris SB. Developmen

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3. Exxon Biomedical Sciences Incorporated. Two generation reproduction toxicity study in rats with di-isodecyl phthalate (DIDP; MRD-94-775). East Millstone, NJ: Exxon Chemical Company; Exxon Chemical Europe, Inc., 1997.

4. Exxon Mobil Biomedical Incorporated. Two generation reproduction toxicity study in rats with MRD-94-775. Project Number: 1775355A. East Millstone, NJ: Exxon Mobil Chemi

cal Company, Inc.; Exxon Mobil Chemical Europe, Inc., 2000.Appendix III 

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