United States
Environmental Protection
1=1 m m Agency
EPA/690/R-07/01 IF
Final
7-26-2007
Provisional Peer Reviewed Toxicity Values for
p,p'- Dichlorodiphenyldichloroethylene (p,p'-DDE)
(CASRN 72-55-9)
Superfund Health Risk Technical Support Center
National Center for Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268

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Acronyms and Abbreviations
bw	body weight
cc	cubic centimeters
CD	Caesarean Delivered
CERCLA	Comprehensive Environmental Response, Compensation and
Liability Act of 1980
CNS	central nervous system
cu.m	cubic meter
DWEL	Drinking Water Equivalent Level
FEL	frank-effect level
FIFRA	Federal Insecticide, Fungicide, and Rodenticide Act
g	grams
GI	gastrointestinal
HEC	human equivalent concentration
Hgb	hemoglobin
i.m.	intramuscular
i.p.	intraperitoneal
IRIS	Integrated Risk Information System
IUR	inhalation unit risk
i.v.	intravenous
kg	kilogram
L	liter
LEL	lowest-effect level
LOAEL	lowest-observed-adverse-effect level
LOAEL(ADJ)	LOAEL adjusted to continuous exposure duration
LOAEL(HEC)	LOAEL adjusted for dosimetric differences across species to a human
m	meter
MCL	maximum contaminant level
MCLG	maximum contaminant level goal
MF	modifying factor
mg	milligram
mg/kg	milligrams per kilogram
mg/L	milligrams per liter
MRL	minimal risk level
MTD	maximum tolerated dose
MTL	median threshold limit
NAAQS	National Ambient Air Quality Standards
NOAEL	no-ob served-adverse-effect level
NOAEL(ADJ)	NOAEL adjusted to continuous exposure duration
NOAEL(HEC)	NOAEL adjusted for dosimetric differences across species to a human
NOEL	no-ob served-effect level
OSF	oral slope factor
p-IUR	provisional inhalation unit risk
p-OSF	provisional oral slope factor
1

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p-RfC
provisional inhalation reference concentration
p-RfD
provisional oral reference dose
PBPK
physiologically based pharmacokinetic
ppb
parts per billion
ppm
parts per million
PPRTV
Provisional Peer Reviewed Toxicity Value
RBC
red blood cell(s)
RCRA
Resource Conservation and Recovery Act
RDDR
Regional deposited dose ratio (for the indicated lung region)
REL
relative exposure level
RfC
inhalation reference concentration
RfD
oral reference dose
RGDR
Regional gas dose ratio (for the indicated lung region)
s.c.
subcutaneous
SCE
sister chromatid exchange
SDWA
Safe Drinking Water Act
sq.cm.
square centimeters
TSCA
Toxic Substances Control Act
UF
uncertainty factor
l^g
microgram
[j,mol
micromoles
voc
volatile organic compound
11

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7-26-2007
PROVISIONAL PEER REVIEWED TOXICITY VALUES FOR
P,P'-DICHLORODIPHENYDICHLOROETHYLENE (P,P'-DDE) (CASRN 72-55-9)
Background
On December 5, 2003, the U.S. Environmental Protection Agency's (EPA's) Office of
Superfund Remediation and Technology Innovation (OSRTI) revised its hierarchy of human
health toxicity values for Superfund risk assessments, establishing the following three tiers as the
new hierarchy:
1.	EPA's Integrated Risk Information System (IRIS).
2.	Provisional Peer-Reviewed Toxicity Values (PPRTV) used in EPA's Superfund
Program.
3.	Other (peer-reviewed) toxicity values, including:
~	Minimal Risk Levels produced by the Agency for Toxic Substances and Disease
Registry (ATSDR),
~	California Environmental Protection Agency (CalEPA) values and
~	EPA Health Effects Assessment Summary Table (HEAST) values.
A PPRTV is defined as a toxicity value derived for use in the Superfund Program when
such a value is not available in EPA's Integrated Risk Information System (IRIS). PPRTVs are
developed according to a Standard Operating Procedure (SOP) and are derived after a review of
the relevant scientific literature using the same methods, sources of data, and Agency guidance
for value derivation generally used by the EPA IRIS Program. All provisional toxicity values
receive internal review by two EPA scientists and external peer review by three independently
selected scientific experts. PPRTVs differ from IRIS values in that PPRTVs do not receive the
multi-program consensus review provided for IRIS values. This is because IRIS values are
generally intended to be used in all EPA programs, while PPRTVs are developed specifically for
the Superfund Program.
Because new information becomes available and scientific methods improve over time,
PPRTVs are reviewed on a five-year basis and updated into the active database. Once an IRIS
value for a specific chemical becomes available for Agency review, the analogous PPRTV for
that same chemical is retired. It should also be noted that some PPRTV manuscripts conclude
that a PPRTV cannot be derived based on inadequate data.
Disclaimers
Users of this document should first check to see if any IRIS values exist for the chemical
of concern before proceeding to use a PPRTV. If no IRIS value is available, staff in the regional
Superfund and RCRA program offices are advised to carefully review the information provided
in this document to ensure that the PPRTVs used are appropriate for the types of exposures and
3

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7-26-2007
circumstances at the Superfund site or RCRA facility in question. PPRTVs are periodically
updated; therefore, users should ensure that the values contained in the PPRTV are current at the
time of use.
It is important to remember that a provisional value alone tells very little about the
adverse effects of a chemical or the quality of evidence on which the value is based. Therefore,
users are strongly encouraged to read the entire PPRTV manuscript and understand the strengths
and limitations of the derived provisional values. PPRTVs are developed by the EPA Office of
Research and Development's National Center for Environmental Assessment, Superfund Health
Risk Technical Support Center for OSRTI. Other EPA programs or external parties who may
choose of their own initiative to use these PPRTVs are advised that Superfund resources will not
generally be used to respond to challenges of PPRTVs used in a context outside of the Superfund
Program.
Questions Regarding PPRTVs
Questions regarding the contents of the PPRTVs and their appropriate use (e.g., on
chemicals not covered, or whether chemicals have pending IRIS toxicity values) may be directed
to the EPA Office of Research and Development's National Center for Environmental
Assessment, Superfund Health Risk Technical Support Center (513-569-7300), or OSRTI.
INTRODUCTION
No verified chronic reference dose (RfD) or reference concentration (RfC) forp,p '-
dichlorodiphenyldichloroethylene (p,p -DDE) is available on IRIS (U.S. EPA, 2007), the
Drinking Water Standards and Health Advisories list (U.S. EPA, 2006), or the HEAST (U.S.
EPA, 1997). The U.S. EPA's Chemical Assessments and Related Activities (CARA) list (U.S.
EPA, 1991, 1994) does not indicate any documents relating to the health effects of p,p '-DDE.
ATSDR (2002) prepared a toxicological profile for DDT, DDE and DDD. ATSDR did not
develop any Minimal Risk Levels (MRLs) forp,p '-DDE. There was no explanation as to why
MRLs were not developed for p,p '-DDE. The American Conference of Governmental Industrial
Hygienist (ACGIH, 2006), Occupational Safety and Health Administration (OSHA, 2006) and
National Institute for Occupational Safety and Health (NIOSH, 2006) have not adopted
occupational exposure limits for p,p '-DDE. The NTP status report (NTP, 2006) and World
Health Organization documents (WHO, 1979, 1989) were consulted for relevant information.
Both a cancer weight-of-evidence classification and an oral slope factor for p,p '-DDE are
available on IRIS (U.S. EPA, 2007). The cancer assessment, verified in 1988, classifiesp,p '-
DDE in category B2 (probable human carcinogen under 1986 Guidelines for Carcinogen
Assessment) based on liver tumors in both mice and hamsters and thyroid tumors in female rats
after dietary exposure. IRIS (U.S. EPA, 2007) reports an oral slope factor of 0.34 per mg/kg-day
based on hepatocellular carcinomas and hepatomas in mice and hamsters exposed via the diet
(NCI, 1978; Tomatis et al., 1974; Rossi et al., 1983). IRIS does not report an inhalation unit risk
forp,p '-DDE. The IRIS carcinogenicity assessment forp,p '-DDE is derived from a Hazard
Assessment Report on DDT, DDD, and DDE (U.S. EPA, 1980) and the Carcinogen Assessment
4

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7-26-2007
Group's Calculation of the Carcinogenicity of Dicofol (Kelthane), DDT, DDE, and DDD (TDE)
(U.S. EPA, 1985). p,p '-DDE is not included in the National Toxicology Program's (NTP) 11th
Report on Carcinogens (NTP, 2006). The International Agency for Research on Cancer (IARC,
1991) classifies DDT and associated compounds (includingp,p -DDE) in Group 2B (possibly
carcinogenic to humans), citing inadequate evidence in humans, but sufficient evidence in
animals for the carcinogenicity of DDT. The present document does not include a cancer
assessment forp,p '-DDE, as one is available on IRIS.
To identify toxicological information pertinent to the derivation of provisional toxicity
values forp,p '-DDE, references from the 2002 ATSDR Toxicological Profile for DDT, DDE and
DDD were screened for publications pertinent to the toxicity of p,p '-DDE. Update searches
were conducted in August, 2006 for literature dating from 2000 to 2006 using the following
databases: MEDLINE, TOXLINE, BIOSIS, TSCATS, CCRIS, DART/ETIC, GENETOX,
HSDB and Current Contents.
REVIEW OF PERTINENT DATA
Human Studies
A large number of human epidemiological studies have evaluated the noncarcinogenic
effects of p,p '-DDE in recent years. A table containing summaries of the epidemiological
studies (of noncancer endpoints) conducted between 2001 and 2006 is appended to this report
(Appendix A). For each study, the table reports the study type, number of participants, endpoints
assessed and general findings based on a review of the abstract for that study. The endpoints
examined in the majority of the studies can be grouped into the following categories:
reproductive or developmental outcomes, lactation function, neurodevelopment, postnatal
growth, effects on male or female hormones or reproductive function, osteoporosis and immune
system function. In large part, the studies used concentrations ofp,p '-DDE in blood or milk as
measures of exposure. As the table indicates, many of the studies were cross-sectional in nature
and/or used very small sample sizes. Most of the studies were potentially confounded by co-
exposure to other organochlorine compounds. Only a few studies reported a significant
association between the endpoint examined and exposure top,p '-DDE. Among these, there was
no consistent finding of an association with one or more particular endpoints. Three larger
studies with positive findings are discussed further below.
Among the three larger studies (n > 1000) of more rigorous design (case-control or
cohort), that reported a statistically significant response, there was suggestive evidence of an
effect of p,p '-DDE on the incidence of preterm birth (Longnecker et al., 2001), birth defects
(Salazar-Garcia et al., 2004) and growth through 7 years of age (Ribas-Fito et al., 2006). In a
U.S. study, Longnecker et al. (2001) found a significant increase in the odds of preterm birth
(OR =1.5, 95% CI = 1.0-2.3) at serum p,p '-DDE levels of 15-29 |ig/L, with increasing ORs as
DDE levels increased. Odds ratios (ORs) for small-for-gestational age also increased with DDE
levels, but the trend was not statistically significant. Blood samples collected for this analysis
were mostly from the 1960s, when DDT use in the U.S. was at its peak (Longnecker et al.,
2001). Limited support for an association with preterm birth is provided by three smaller studies
5

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that reported statistically non-significant increased ORs for preterm birth with higherp,p '-DDE
levels (Farhang et al., 2005; Torres-Arreola et al., 2003) or higher serump,p '-DDE in preterm
birth cases than in controls (Ribas-Fito et al., 2002). In a large (n = 9,187) retrospective cohort
study of male malaria control workers in Mexico, Salazar-Garcia et al. (2004) reported a
significantly increased odds ratio for birth defects (OR = 4.15, 95% CI = 1.38-12.46) when the
estimated maternal fat concentration ofp,p '-DDE was about 82 ppb. The concentration ofp,p '-
DDE in maternal fat was estimated based on occupational history; concentrations were not
measured analytically (Salazar-Garcia et al., 2004). There are no other studies evaluating the
possible association between birth defects andp,p '-DDE. A statistically significant decrease in
growth (height) through age 7 years was observed in children whose mothers' serump,p '-DDE
levels were at least 60 |ig/L (Ribas-Fito et al., 2006). Karmaus et al. (2002) also reported a
decrease in height among German girls in the highest quartile of serum p,p '-DDE levels when
compared with the lowest quartile; there was no effect in boys. In contrast to the latter findings,
however, Gladen et al. (2000) reported that both height and weight of boys whose maternal fat
p,p '-DDE levels were greater than 4 ppm were increased over boys with the lowest levels (< 1
ppm).
Both Longnecker et al. (2001) and Ribas-Fito et al. (2006) studies were potentially
confounded by coexposure to other organochlorine compounds, which were not controlled for in
either study. Salazar-Garcia et al. (2004) controlled for coexposure to other pesticides and
chemicals; however, this study was conducted in a population with high levels of exposure and
the authors acknowledged that the relevance of the findings to lower level exposures was
uncertain. Further, for the purpose of the study, birth defects were broadly defined as
"congenital malformations", a term which includes a wide range of endpoints with potentially
varying etiologies. Finally, because DDE is a metabolite of DDT and is relatively persistent in
the body (ATSDR, 2002), it is not possible to determine whether biological measurements of
DDE reflect exposure to DDE, or metabolism of DDT. As a result, none of these studies is
considered adequate for the purpose of deriving provisional toxicity values.
Animal Studies
Oral Exposure
Subchronic Studies — In preparation for the chronic cancer bioassay, NCI (1978)
conducted a subchronic dietary toxicity study ofp,p '-DDE in Osborne-Mendel rats and B6C3F1
mice. p,p '-DDE (>95% pure) in corn oil was mixed with feed and administered ad libitum to
groups of 5 male and 5 female rats and mice per concentration for 6 weeks, followed by a 2-
week observation period. Diets containing 0, 316, 562, 1000, 1780 or 3160 ppmp,p '-DDE were
given to rats (0, 28, 49, 87, 156, or 276 mg/kg-day in males, and 0, 30, 53, 95, 168, or 299
mg/kg-day in females1), while mice received diets containing 0, 139, 193, 269, 363 or 519 ppm
(0, 25, 35, 49, 65, or 94 mg/kg-day in males, and 0, 27, 38, 52, 71, or 101 mg/kg-day in
females1). Only mortality and body weight changes were evaluated; no animals were
necropsied.
1 Based on reference values for food consumption and body weight (U.S. EPA, 1988).
6

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One female rat treated at 1000 ppm died and all of the female rats exposed to higher
concentrations died by week 6; in contrast, no male rats died (NCI, 1978). Mean body weights
were reduced in all dose groups among male rats (11% lower than controls at 1000 ppm and 22%
lower at 1780 ppm), but were not affected among female rats. Among mice, one control male
and one male exposed to 269 ppm p,p '-DDE died, as well as four males and two females
receiving 363 ppm. p,p '-DDE did not affect body weights in the exposed mice. In rats, 1000
ppm in the diet (95 mg/kg-day) represents a Frank Effect Level (FEL) based on one female death
(all female rats exposed to higher concentrations died). In mice, the FEL is 269 ppm (49 mg/kg-
day), also based on a single death. Although one death may not represent an increase over
controls (one control mouse also died), the pronounced mortality (4/5 males and 2/5 females) at
the next higher dose (363 ppm or 65 mg/kg-day in males) suggests that the death of the one male
at 49 mg/kg-day could be a result of treatment; however, no mice exposed to 519 ppm was
reported to have died. Individual variability in susceptibility to the lethal effects ofp,p-DDE
may have contributed to the differences in survival rate, especially since only a small number of
animals was tested. Due to the absence of gross and microscopic pathology examinations in the
subchronic portion of the NCI study, other effect levels cannot be assigned based on these data.
Chronic Exposure — Tomatis et al. (1974) evaluated the carcinogenicity ofp,p '-DDE in
CF-1 mice treated via the diet for a lifetime. The authors administeredp,p '-DDE in the diet (0 or
250 ppm) to 60 male and 60 female mice (6-7 weeks old) for up to 123 weeks; 100 males and 90
females were maintained on a control diet. A dietary concentration of 250 ppm corresponds to
an estimatedp,p '-DDE dose of 37.5 mg/kg-day (for both males and females) based on the
standard reference value for average lifetime mouse food consumption of 15% of body weight
per day. The test compound was 99% pure and was dissolved in acetone prior to being mixed
with powdered food and converted to pellets. Groups of four animals (gender not specified)
were sacrificed either between weeks 65 and 74 of treatment or between weeks 94 and 118 of
treatment for analysis ofp,p '-DDE levels in the liver and interscapular fat (and sometimes in
liver tumors and kidney). All animals dying spontaneously or killed humanely were necropsied;
remaining animals were sacrificed at 130 weeks of age. Histopathology evaluation was
restricted to the lungs, heart, thymus, liver, kidneys, spleen, brain and any organs with gross
abnormalities.
Survival was lower in thep,p '-DDE-treated group than in controls, especially among
males (Tomatis et al., 1974). Only 53% of males treated withp,p '-DDE survived to 70 weeks,
compared with 88% of control males. The authors did not present a statistical analysis of
mortality. However, the incidence of hepatomas was higher inp,p '-DDE-treated mice and mice
with hepatomas died earlier than others. Thus, the reduced survival time of treated mice likely
resulted from the hepatomas. Clinical signs of toxicity (convulsions and tremors) were observed
in three female mice treated withp,p '-DDE. The symptoms preceded death in all three cases.
Male mice treated withp,p '-DDE gained weight more slowly than controls. Terminal body
weight was about 11% lower (based on graphical presentation of the data), but non-significant in
thep,p '-DDE-treated male mice than in control males. The authors reported neither a statistical
comparison of body weights nor raw data. The only nonneoplastic lesion reported was an
increased incidence in treated males of myocardial necrosis with diffuse hemorrhages, leukocytic
infiltration and fibroblastic reaction (1/98 control males vs 22/53 treated males, p<0.001, Fisher
Exact test performed for this review). Myocardial effects also occurred in male rats in the NCI
7

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(1978) chronic study (see below). Thep,p '-DDE exposure level in this study (250 ppm or 37.5
mg/kg-day) appears to be an FEL based on reduced survival of male mice as well as
convulsions/tremors and death in females; however, the survival differences may be confounded
by the early appearance and high incidence of hepatomas.
NCI (1978) conducted a carcinogenicity bioassay of p,p '-DDE in Osborne-Mendel rats
and B6C3F1 mice. p,p '-DDE (>95% pure) in corn oil was mixed with feed at varying
concentrations and rats were fed ad libitum. Nominal concentrations, durations of exposure at
these concentrations, and weighted average concentration and dose estimates are given in Table
1. As the table indicates, the exposure concentration was changed several times during the
dosing period. In rats, signs of toxicity during week 24 prompted the investigators to decrease
the exposure concentrations in all groups. A further reduction was made in the high-dose groups
(beginning week 56 in females and week 60 in males) by suspending exposure for one-week
periods followed by 4 weeks of exposure at the previous concentration. This pattern continued
until the exposure period was completed at 78 weeks. Rats were observed for up to 33 weeks
after exposure termination and prior to sacrifice. Mice appeared to tolerate the initial
concentrations well, so the investigators increased the exposure concentrations during week 8.
Beginning in week 37, the dose reduction pattern used in high-dose rats (1 week off, 4 weeks
exposed) was applied to high-dose mice. Mice were observed for up to 15 weeks after the 78-
week exposure period and prior to sacrifice. Weighted average exposure concentrations and
daily doses shown in Table 1 are averaged over the 78 week exposure period and do not take into
account the post-exposure observation period.
Body weight and food consumption measurements, clinical observations and palpations
for masses were conducted weekly for 10 weeks and monthly thereafter; daily mortality checks
were performed (NCI, 1978). Necropsy was performed on all animals, but organ weights were
not recorded. Histopathologic examination was initially limited to control animals, animals with
visible tumors and at least 10 grossly normal males and females from each group. Later in the
study, the protocol was altered to include tissues from other animals; however, the authors did
not indicate how the other animals were selected, how many were included or when the protocol
change was initiated. Nearly 30 tissues were subjected to microscopic examination. The authors
noted that tissues were not examined from some animals that died early, and that some animals
were missing, cannibalized or in an advanced state of autolysis precluding histopathologic
examination. Incidence of lesions was reported using the number of animals for which that
specific tissue was examined as the number at risk, except where lesions were observed grossly
or could appear at multiple sites (e.g., lymphoma), in which cases the number of animals
necropsied was used.
In rats, clinical signs of toxicity began during week 8 and included hunched or thin
appearance, respiratory signs, urine staining, ocular signs, body sores, bloating and alopecia
(incidences and doses not reported), as well as isolated occurrences of tremors, ataxia, loss of
equilibrium, hyperactivity and vaginal discharge in one or two exposed rats (NCI, 1978). p,p '-
DDE-treatment significantly decreased survival in both genders. Survival to 92 weeks was 80%,
68%) and 52% for control, low-, and high-dose males, and 100%, 84%, and 72% in females. A
number of the high-dose deaths (including 9 of the 14 females that died prior to week 92)
occurred prior to the dose reduction during week 24. Analysis of survival curves indicated
8

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Table 1. Group Sizes, Dietary Concentrations and Dose Estimates for NCI (1978) Cancer
Bioassay for />,/j'-DDE in rats
Group
Group
Size
Nominal
Concentration
(ppm)
Duration at
this
Concentration
(weeks)
Untreated
Duration
(weeks)
Weighted
Average
Concentration"
(ppm)
Weighted
Average
Daily Doseb
(mg/kg-day)
Male Rats
Control
20
0

111

0
Low Dose
50
675
338
0
23
55
33
437
22
High Dose
50
1350
675
675c
0
23
36
15
4
33
839
42
Female Rats
Control
20
0

111

0
Low Dose
50
375
187
0
23
55
34
242
12
High Dose
50
750
375
375°
0
23
32
18
5
34
462
23
Male Mice
Control
20
0

92

0
Low Dose
50
125
150
0
7
71
14
148
22
High Dose
50
250
300
300°
0
7
29
33
9
14
261
39
Female Mice
Control
20
0

92

0
Low Dose
50
125
150
0
7
71
15
148
22
High Dose
50
250
300
300°
0
7
29
33
9
15
261
39
a.	Calculated by the authors as the sum of concentration x time averaged over 78 weeks.
b.	Calculated using weighted average concentration and standard reference values for food consumption (5% and 15%
of body weight per day for rats and mice, respectively).
c.	Administered as 1 dose-free week followed by 4 weeks at this level.
Source: NCI, 1978.
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that survival among low-dose females fell below controls after week 70; in low dose males,
survival dropped below control survival around week 90. The authors reported treatment-related
reductions in body weight, but did not present statistical comparisons of group mean body
weights or raw data. Based on graphical presentation of the data, the body weight decrements at
the high dose appear to range from 10 to 15% below controls over the course of the study; in
general, lower reductions occurred in the low-dose group.
Histopathology evaluation showed evidence of hepatotoxicity in rats of both genders
(NCI, 1978). Centrilobular necrosis and fatty metamorphosis of the hepatocytes were observed
in both males and females at the incidences shown in Table 2. Dose-related increases in the
incidences of lung hemorrhage and myocardial degeneration were also observed in male rats
(Table 2); these effects were not observed in females. The authors did not provide statistical
analyses of the nonneoplastic lesions. Statistical tests conducted for this review indicate
significant dose-related trends for centrilobular necrosis of the liver in female rats, as well as
fatty metamorphosis of the liver, lung hemorrhage and myocardial degeneration in male rats.
Pairwise comparisons are given in Table 2. The lowest dose in this study (12 mg/kg-day)
represents a FEL based on reduced survival of female rats after 70 weeks. A NOAEL was not
established in this study.
Table 2. Incidence of Nonneoplastic Lesions
in Rats Exposed to p,p'~DDE.

Centrilobular
necrosis of liver
Fatty
metamorphosis of
liver
Lung
hemorrhage
Myocardial
degeneration
Dose
Group
Males
Females
Males
Females
Males
Females
Males
Females
Control
0/20
l/20a
2/20a
11/20
0/20a
5/20
10/20a
11/20
Low dose
2/40
7/34
25/40b
3/34
3/21
11/29
18/24
12/29
High dose
3/40
10/33b
20/40b
10/33
6/23 b
5/28
21/25 b
8/22
a.	Significant trend by Cochran-Armitage test (p<0.05) conducted for this review.
b.	Significantly different from control by Fisher's exact test (one-sided p<0.05) conducted for this review.
Source: NCI, 1978.
In mice, there were no clinical signs of toxicity until week 22, when a majority (60-85%,
dose not specified) of the male mice appeared hunched; this continued until the intermittent
dosing period was instituted during week 34 (NCI, 1978). Reduced survival of female mice was
significantly (p<0.001) associated with increasingp,p '-DDE exposure. Survival to 75 weeks
was 95%), 94%o and 56% for control, low- and high-dose females. Survival of male mice was
better in the treated groups than in the control group; however, survival of control male mice was
low. Only 25% (5/20) of male controls survived at least 70 weeks, compared with 70% of low-
dose and 62%o of high-dose males. The high control male mortality can probably be attributed to
intercurrent disease that also produced high incidences of amyloidosis of the spleen, kidneys and
liver in control males. The incidence of amyloidosis was lower in the exposed groups than in
controls; one other study (Rossi et al., 1983) also suggested a protective effect ofp,p '-DDE
exposure on the incidence of amyloidosis. Body weights and weight gain of exposed male mice
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did not differ from controls. In contrast, body weights of female mice were reduced in both dose
groups, with differences increasing throughout the exposure period. The authors did not present
statistical comparisons of group mean body weights or raw data. Based on graphical
presentation of the data, the maximum decrement from control weights (near the end of the
exposure period) was approximately 10-15% in the low dose females and 15-20% in the high-
dose females. The body weight differences in females persisted throughout the 15-week post-
exposure observation period.
The authors reported that nonneoplastic lesions in the exposed mice were "similar in
number and kind to those lesions naturally occurring in aged B6C3F1 mice" (NCI, 1978).
Examination of the summary data on incidence of nonneoplastic lesions suggested the possibility
of a dose-related trend in chronic inflammation of the kidney (2/19, 11/41, 16/45) among male
mice. Statistical tests conducted for this review indicated a statistically significant dose-related
trend and a significant increase over controls at the high dose. Without historical control
incidence data, it is not possible to determine whether these incidences are within the normal
range for this strain of mouse. The LOAEL for this study, based on body weight reductions of
10-15%) in female mice and clinical signs of toxicity (hunched or thin appearance) in male mice,
is 26 mg/kg-day, the lowest dose tested; a NOAEL cannot be determined from these data.
A dose-related increase in the incidence of hepatocellular carcinomas in mice of both
sexes was observed (NCI, 1978). The incidence of other tumor types was not increased with
exposure.
Rossi et al. (1983) treated Syrian golden hamsters withp,p '-DDE in the diet for life (up
to 128 weeks). The test article was 99%> pure and was dissolved in 3%> olive oil prior to being
mixed in the diet at concentrations of 0, 500 or 1000 ppm (about 0, 48, or 97 mg/kg-day for both
males and females2). Groups of at least 40 male and female hamsters/concentration were given
the diet ad libitum beginning at 8 weeks of age. Weekly measurements of body weight and food
consumption were made through the first 20 weeks and biweekly measurements thereafter.
Animal health observations were recorded with the same frequency. Animals found dead or
moribund were necropsied and any surviving to 128 weeks of age were sacrificed and necropsied
at that time. Gross examination of all organs and histological examination of the liver, spleen,
kidneys, adrenal glands, urinary bladder, thyroid, lungs, testes, ovaries and organs with gross
lesions was performed.
Although statistical analysis did not indicate a difference in mortality among the groups,
animals treated withp,p '-DDE lived longer, on average, than controls (Rossi et al., 1983). The
authors attributed this to a protective effect of p,p '-DDE against amyloidosis of the liver, kidney
and adrenal glands (amyloidosis occurred with greater incidence in controls than in treated
animals). Another study (NCI, 1978) supports a protective effect ofp,p '-DDE exposure on
amyloidosis incidence. Body weight gain was reduced in a dose-related fashion among thep,p '-
DDE-treated groups. The authors did not present a statistical comparison of body weights, nor
the raw data to permit statistical analysis. Based on graphical presentation of the body weight
data, the terminal body weight was approximately 23%> lower than controls among males in the
2 Based on reference values for body weight and food consumption (U.S. EPA, 1988).
11

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high-dose group, and 16% lower than controls among females in the high-dose group. In
addition, terminal body weight was about 9% lower than controls among males treated at the low
dose, but was not different from controls among females at the low dose. Body weight
differences began about 10 weeks after study commencement among males, but not until 30
weeks of treatment among females. Food consumption was not affected by treatment. The
authors suggested that the lower weight gain may have resulted from liver necrosis, which was
more severe in the 1000 ppm groups than in those treated at 500 ppm (incidence and severity not
reported for either group). The incidence of hyperplastic foci of the liver was increased in
hamsters treated at 1000 ppm p,p '-DDE; these lesions are assumed to be preneoplastic. The
incidences of liver and adrenal gland tumors were increased in males and females treated with
p,p '-DDE.
The primary aim of this study was to evaluate the carcinogenic potential of p,p '-DDE
(Rossi et al., 1983). Little information was given regarding noncancer effects; for example, liver
necrosis was noted inp,p '-DDE treated animals, but the incidence and severity were not
reported. Nevertheless, there was a clear effect of treatment on body weight gain and males
treated at the low dose (500 ppmp,p -DDE) had terminal body weight reductions averaging 9%.
Importantly, the body weight differences in males appeared long before the first tumor appeared
(55 weeks in males), so the body weight decrements were not secondary effects of tumors. Thus,
the low dose of this study (500 ppm or 48 mg/kg-day) is considered a LOAEL for body weight
reductions in males and possible increases in liver necrosis. No NOAEL can be determined from
this study.
Reproductive/Developmental Studies — In a reproductive study, Kornbrust et al.
(1986) treated female Sprague-Dawley rats withp,p '-DDE (purity >99%) in corn oil by gavage.
Groups of 54 and 51 rats were given vehicle or 10 mg/kg (respectively) 5 days/week, for 5 weeks
prior to mating (with untreated males), during gestation and during lactation through either
postnatal day (PND) 8 or 19. Body weights were recorded weekly until mating. Reproductive
parameters were assessed after parturition, including: percent sperm positive, percent pregnant,
gestation duration, litter size and sex ratio. Litter weights were measured on PND 0, 2, 8, 14 and
19. Litters designated for lactation studies were normalized to six male and six female pups.
Lactation parameters were assessed just prior to sacrifice on PND 9 or 20 and included milk
production (decrease in body weight after nursing) and milk composition; milk and blood were
collected forp,p '-DDE analysis. Upon sacrifice, left-side mammary glands were removed for
histologic examination, while right-side glands were used for determination of DNA and RNA
content. Liver, kidneys, thymus, ovaries and uterus of the dams were removed, weighed and
examined microscopically. There were four pups per litter that were also examined
histologically.
Treatment with p,p '-DDE had no significant effect on the percentage of females that were
sperm positive or pregnant, or on litter size, length of gestation, sex distribution of offspring or
growth of litters (Kornbrust et al., 1986). In the first 8 days following parturition, mortality was
slightly higher in the pups from treated dams (3.8%) than in pups from control dams (2.2%), but
was within the range of historical controls. Most pup deaths occurred on the day of birth and
there were no more than three deaths in any litter. The investigators concluded that pup
mortality was unrelated to treatment. In the dams, treatment withp,p '-DDE had no effects on
12

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organ weights or on indices of lactation capacity (including mammary gland weight). No gross
lesions were seen during necropsy of the dams. Histopathological examination revealed
hepatocellular changes in thep,p '-DDE-treated dams, including: swelling, inflammation,
increased eosinophilia, increased mitoses, and occasional focal necrosis and hemorrhage. The
hepatic lesions were considered to be mild by the investigators. Treatment-related histological
changes were not seen in other maternal organs or in the pups. The concentrations ofp,p '-DDE
in (whole) milk from thep,p '-DDE-treated dams were 24.4 ppm on PND 9 and 21.9 ppm on
PND 20. The only dose tested, 10 mg/kg-day, constitutes a LOAEL for hepatic effects in the rat
dams in this study. A NOAEL can not be determined from these data.
The antiandrogenic effects ofp,p '-DDE on fetal, pubertal and adult rats were investigated
by Kelce et al. (1995). A series of experiments was reported in a brief letter, with few details of
each individual experiment. In one experiment, groups of 8 pregnant Long-Evans hooded rats
were given vehicle or 100 mg/kgp,p '-DDE (purity not specified) in corn oil via gavage on
gestational days (GD) 14-18. The anogenital distance in male pups of treated dams was
significantly reduced (p<0.04 by analysis of litter means) and these pups retained thoracic
nipples to postnatal day 13. The incidence of the latter effect was not reported; however, the
authors did not observe this effect in control offspring. This experiment provides a LOAEL of
100 mg/kg-day based on demasculinization of male offspring (reduced anogenital distance and
presence of thoracic nipples); no NOAEL can be identified.
In studies on the effects in pubertal rats, weanling3 male rats (12/group) were given
vehicle or 100 mg/kg-day p,p '-DDE (exposure route assumed to be gavage as with the other
experiments) until after puberty (to day 57; exposure duration of either 32 or 36 days3; Kelce et
al., 1995). Serum testosterone levels in exposed rats were not different from controls (timing of
samples not reported). However, the onset of puberty (defined as the age at preputial separation)
was significantly delayed (5 days later than controls, p<0.005) in treated rats. The authors noted
that, since treated rats had higher body weights than controls, the pubertal delay was not
confounded by growth retardation. This experiment suggests a LOAEL of 100 mg/kg-day for
delayed puberty; no NOAEL can be identified as only one dose was tested.
In the final experiment, adult (120 days old) male rats (6/group) were castrated and
implanted with testosterone-containing capsules (to provide constant serum androgen levels) and
then treated by gavage with doses of 0 or 200 mg/kg-day for 4 days (Kelce et al., 1995). Seminal
vesicle and ventral prostate weights in treated rats were significantly (p<0.01) lower than
controls (16% and 30%, respectively); the authors did not report when these weights were
evaluated. Increases in androgen-repressed testosterone-repressed prostatic message 2 (TRPM-
2) mRNA levels (13-fold higher than controls) and decreases in androgen-induced prostate
binding protein subunit 3 mRNA levels (35% lower than controls) in treated rats provided
evidence for the anti androgenic effect of p,p '-DDE on adult rats. Serum testosterone levels were
not affected by treatment. Effect levels were not determined from these data due to the
confounding effects of castration and hormone supplementation.
3 Kelce et al. (1995) report in the text of the publication that the rats were 21 days old at exposure commencement;
in the caption for Figure 1, the age is reported as 25 days.
13

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Antiandrogenic effects of gestational p,p '-DDE exposure in Long-Evans (LE) hooded
and Sprague-Dawley (SD) rats were assessed by You et al. (1998). Groups of 8 to 11 pregnant
LE and SD rats were givenp,p '-DDE (purity not specified, administered in corn oil) via gavage
in doses of 0, 10 or 100 mg/kg on GD 14-18. A separate group of rats was given flutamide as a
positive control. Three pregnant rats from each of the p,p '-DDE-treated groups were sacrificed
on GD 20 for analysis ofp,p '-DDE in maternal serum, brain, liver, fat and placenta and in fetal
liver. Remaining dams were allowed to give birth. Pup weights and anogenital distances were
measured on PND 2. External examination of male offspring for thoracic nipple retention was
conducted on PND 14. Both male and female pups were examined for sex organ development
(preputial separation and vaginal opening).
On PND 21 ,p,p '-DDE-treated dams, as well as 2 male and 1 female pups from each litter
were sacrificed (You et al., 1998). p,p '-DDE content was measured in blood, liver and fat of
both dams and pups and in brains of the dams. Testes, prostate and epididymis were removed
from one of the 2 male pups from each litter. One testis was used for Northern blot analysis of
androgen receptor mRNA, while the other testis and the remaining organs were subjected to
immunohistochemistry for the androgen receptor. On PND 57, 2 males from each treated litter
were sacrificed for analysis of testosterone levels in blood and p,p '-DDE content of blood, liver
and fat.
Pup body weights did not differ among the groups in either strain of rat (You et al.,
1998). Anogenital distance in male pups was reduced by 14% and 8% in high-dose SD and LE
rats, respectively; the difference was statistically significant in the LE rats (p=0.026) and
marginal in the SD rats (p=0.065). Thoracic nipple retention was significantly increased at the
high dose in both strains and at the low dose in SD rats only. Based on graphical representation
of the data, the mean numbers of nipples per pup was approximately 0.4, 1.2 and 3.8 in control,
low-dose and high-dose SD rats and approximately 0.6, 0.8 and 3 in LE rats. p,p '-DDE
treatment did not affect vaginal opening or preputial separation time and hypospadias was not
observed in any p,p '-DDE treatment group. There was no significant difference in weights of
the testis, epididymis, seminal vesicles or ventral prostate among thep,p '-DDE treated and
control groups. p,p '-DDE treatment did not result in statistically significant differences in serum
testosterone levels measured on PND 57.
Immunohistochemistry for the androgen receptor in SD rats showed decreased staining
intensity in the testicular tissues of male offspring of high-dose p,p '-DDE treated rats, but no
observable difference in low-dose offspring (You et al., 1998). Staining was also reduced in the
epithelial cells of the epididymal duct and the glanular acini of the prostate. The authors
indicated that the number of Sertoli cells showing staining for the receptor was lower in the high
p,p '-DDE dose group than in controls. In LE rats, there were no observable differences in
staining intensity between the p,p '-DDE-treated and control groups. Androgen receptor mRNA
was increased in LE rats in the highp,p '-DDE dose group, but not in SD rats. Analysis ofp,p '-
DDE levels in organs and blood showed higher levels in both dams and offspring of the LE
strain compared with SD rats, especially in blood concentrations measured in dams on GD 20.
14

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This study identifies a developmental LOAEL of 10 mg/kg-day for impaired sexual
development (demasculinization represented by retention of thoracic nipples) in male SD pups.
No NOAEL can be identified from this study.
You et al. (1999a) conducted a follow-up study to evaluate whether in utero and
lactational exposure to p,p '-DDE modified the effect of adult exposure top,p '-DDE on the
prostate. Groups (number not reported) of pregnant LE rats given gavage doses of 0, 10 or 100
mg/kgp,p '-DDE (>99% pure, in corn oil) on GD 14-18 were allowed to give birth. Male pups
from all groups were weaned on PND 21 and body weights were measured twice a week from
weaning until PND 80. At that time, the male pups were divided into two subgroups (5-8 per
subgroup) and treated either with corn oil alone or with 70 mg/kg-day p,p '-DDE by gavage for
four days. One day after the final treatment, the rats were sacrificed andp,p '-DDE content of
liver and perirenal fat was analyzed. Trunk blood was collected and analyzed for serum
testosterone and luteinizing hormone by radioimmunoassay. The testes, epididymides, seminal
vesicles, ventral prostates and kidneys were weighed. Finally, levels of mRNA for two
androgen-regulated genes (the C3 subunit of the prostatic secretory prostatein and testosterone-
repressed prostatic message-2 [TRPM-2]) and a housekeeping gene (glyceraldehyde 3-phosphate
dehydrogenase) were measured in ventral prostate tissues via Northern blot analysis. TRPM-2 is
an androgen-repressed gene whose expression has been associated with cell death during
prostatic involution (You et al., 1999a).
Adult body weights were not affected by either in utero or adult treatment with p,p '-DDE
(You et al., 1999a). Ventral prostate weights were reduced by 18% and 31% in the low- and
high-dose groups (respectively) treated in utero alone, when compared with controls not treated
in utero. Neither change was statistically significant (p=0.076 for high-dose group). However,
in rats treated with 70 mg/kg-day as adults and not treated in utero, there was a statistically
significant (p<0.05) reduction (31%) in ventral prostate weight when compared with controls
untreated at either time. Weights of seminal vesicles and epididymis were also significantly
(p<0.05) reduced (32% and 11%, respectively) in rats treated as adults but not treated in utero.
Adult treatment did not affect prostate, seminal vesicle or epididymis weight in rats previously
exposed to p,p '-DDE in utero. One rat treated at the high dose in utero and not treated as an
adult had suppurative inflammation of the prostate.
Although in utero treatment with p,p '-DDE resulted in expression of TRPM-2, adult
treatment withp,p '-DDE did not (You et al., 1999a). The authors reported that the C3 mRNA
was apparent in all treatment groups and group-related differences were difficult to discern.
Serum testosterone levels were higher in rats treated with p,p '-DDE as adults, but the increases
were not statistically significant at either dose. No effect levels were identified from this study.
Few endpoints were examined in the animals treated in ///era/during lactation (only), precluding
the identification of an effect level from these data. Effects in adult rats treated for 4 days only at
70 mg/kg-day would be considered acute effects given the very brief exposure duration.
Loeffler and Peterson (1999) administered p,p '-DDE (99% pure, in 95% corn oil/5%
acetone vehicle) by daily gavage to groups of 6 pregnant Holtzman rats between GD 14 and 18.
Administered doses were 0, 1, 10, 50, 100 or 200 mg/kg. Body weights of dams were measured
daily until parturition. After parturition, litters were weighed and sex ratio and number of live
15

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pups were recorded. Litters were then culled to 10 pups, maximizing the number of male pups.
On PND 1 and 4, crown-rump length and anogenital distances were measured. Thoracic nipple
retention was evaluated on PND 13. Body weights were recorded on PND 1, 4, 7, 14, 21, 32, 49
and 63. After weaning, dams were sacrificed and the number of uterine implant sites was
recorded. Daily examination for preputial separation was conducted beginning on PND 38. On
PND 21, 32, 49 and 63, one or two male rats/litter were sacrificed, at which times ventral
prostate, dorsolateral prostate, seminal vesicles, epididymides and testes were weighed.
Body weight data were not reported (Loeffler and Peterson, 1999). Although the
wording of the paper was not clear, it appears that dams exposed to the highest dose of p,p '-DDE
had significantly lower body weights (9-17%) on GD 17-21, but returned to normal by PND 1.
p,p '-DDE treatment significantly (p<0.05) reduced anogenital distance (as a ratio of crown-rump
length) in male pups of rats exposed to doses of 50 mg/kg-day and higher; however, this
difference persisted to PND 4 only in the 200 mg/kg-day group. In addition, there was a dose-
related increase in the number of nipples per male pup on PND 13. Preputial separation was
significantly delayed only among offspring of the high-dose group. On PND 21 (weaning),
relative weight of the ventral prostate was significantly (p<0.05) lower than control values in
offspring of dams exposed to 50 mg/kg-day or higher. On PND 32 (prepuberty), ventral prostate
weights were reduced in a dose-related fashion, but no statistically significant differences were
observed. Dorsolateral prostate weight was significantly (p< 0.05) decreased in offspring of the
high-dose group on PND 21 and in offspring of all treated groups on PND 32 but not on PND 49
or PND 63. Based on graphical representation of the data, relative dorsolateral prostate weights
(on PND 32) were approximately 85% of control values at 1, 10, 50 and 100 mg/kg-day and
about 60% of controls at 200 mg/kg-day. No differences in ventral or dorsolateral prostate
weights were observed on PND 49 (puberty) or PND 63 (postpuberty). Weights of seminal
vesicles, testes and epididymes did not differ from controls at any time.
Even though statistically significant, the small reduction (on PND 32) in the relative
weight of the dorsolateral prostate (DLP) to be at doses below 200 mg/kg-day are not considered
adverse. The 15% reduction in relative weight was constant across two order of magnitude of
dose and was possibly the result of an anomalously high relative DLP weight in the control
animals. Furthermore, the DLP relative weight profile across dose groups for PND 32 is similar
to the profiles at other PND measurements, for which no weight reduction below 200 mg/kg-day
was observed. Finally, the ventral prostate weight was not affected at PND 32 and only was
reduced at 50 mg/kg-day and higher at PND 21. No other anti-androgenic effects were observed
below 50 mg/kg-day. The bulk of the evidence suggests that there are no effects of p,p'-DDE
below 50 mg/kg-day, at the least. As a conservative estimate, the study establishes a
developmental LOAEL of 50 mg/kg-day for male reproductive effects, with a NOAEL of 10
mg/kg-day. The LOAEL is primarily defined by the transitory 20% reduction in ventral prostate
weight at PND 21 and nipple retention, although there is a suggestion of a reduction in DLP
relative weight at 50 mg/kg-day at PND 63, as well.
Gray et al. (1999) also assessed the antiandrogenic effects ofp,p '-DDE, using both LE
and SD rats treated during gestation. Pregnant rats were given p,p '-DDE (99% pure, in corn oil)
at gavage doses of 0 or 100 mg/kg-day on GD 14-18 and allowed to give birth. Group sizes were
8 control and treated LE rats, 11 control and 9 treated SD rats. Maternal weight gain was
16

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monitored throughout pregnancy, but the frequency of weight measurements was not reported.
The examination of offspring and timing of sacrifice are not clearly described in the publication.
Based on the results, it appears that the male offspring were examined for reproductive organ
development, including external abnormalities (number and location of retained nipples, cleft
phallus, vaginal pouch and hypospadias) and internal abnormalities (ectopic or atrophic testes,
agenesis of the gubernaculums, epididymides, sex accessory glands and ventral prostate;
epididymal granulomas, hydronephrosis and enlarged bladder with stones). Male offspring were
sacrificed for necropsy either at 5 or 15 months of age; it is not clear from the report. Based on
the description for a parallel study, it appears that body weight and the following organ weights
were recorded: pituitary, adrenal, kidneys, liver, ventral prostate, seminal vesicles, testes and
epididymis. Histologic examination appears to have been limited to the ventral prostate and
seminal vesicles.
The authors reported that maternal weight gain was reduced by 35 g (compared with
controls) during treatment withp,p '-DDE, but weight gain returned to normal after treatment
ended (Gray et al., 1999). There were no effects of treatment on pup weight measured at
postnatal day 2. There were clear antiandrogenic effects ofp,p '-DDE treatment on development
of male sex organs. Table 3 shows the parameters affected by p,p '-DDE treatment. As the table
shows, maternal exposure to p,p '-DDE resulted in significant increases in the percent of male
offspring with areolas, mean number of retained nipples and incidence of prostate atrophy, while
decreasing the mean weight of the ventral prostate in LE rats. In SD rats, the effects were more
pronounced; p,p '-DDE exposure resulted in a significant decrease in anogenital distance and
decreased weights of the glans penis, cauda epididymis, ventral prostate and levator ani-
bulbocavernosus muscles. In addition, a significantly increased percent of male SD offspring
had areolas and the mean number of retained nipples was increased. Finally, 7.8% of male SD
offspring of treated dams had hypospadias, while no controls displayed this effect. Despite the
reporting limitations in this study, it shows a clear effect on the development of male
reproductive organs; thus, the dose used (100 mg/kg-day) is a free-standing LOAEL both for
maternal toxicity (decreased weight gain) and for antiandrogenic effects on male reproductive
organ development. A NOAEL can not be determined from these data as only a single dose was
used.
Inhalation Exposure
There are no data on the effects in laboratory animals ofp,p '-DDE exposure via
inhalation.
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7-26-2007
Table 3. Effects of Maternal Exposure top,p'~DDE on Male
Reproductive Organ Development
Parameter
Long-Evans hooded
Spra
£u c-Daw Icy
Control
100 mg/kg-day
Control
100 mg/kg-day
Number of litters
8
8
9
11
Number of males examined externally
61
42
49
83
Number of males necropsied
26
27
44
70
Percent with areolas
0
21±10a
0
71±9a
Mean number of retained nipples
0
0.74±0.15a
0
3.13±0.5a
Weight glans penis (mg)
nd
nd
112 ±2.9
102±1.5a
Weight cauda epididymis (mg)
nd
nd
331±9.6
305±6.2a
Weight ventral prostate (mg)
529±25
417±23a
747±36
575±29a
Weight levator ani-bulbocavernosus
muscle (mg)
nd
nd
1400±40
1204±23a
Percent with hypospadias
0
0
0
7.8±7.8a
Incidence prostate atrophy
0/26
8/27a
nd
nd
a. Significantly different from control (p<0.05)
nd = no data
Source: Gray etal., 1999
Other Studies
Immunotoxicity — Banerjee et al. (1996) evaluated the effects of dietary p,p '-DDE
exposure on humoral and cell-mediated immune response in Wistar rats. Male rats were given
either the control diet or a diet containing 200 ppm p,p '-DDE (99% pure) for 6 weeks (20 mg/kg-
day), assuming a food-consumption factor of 10% of body weight per day. General condition,
food consumption and body weights were recorded weekly. Three weeks before the end of the
exposure period, half of each group was immunized by subcutaneous administration of 3 mg
ovalbumin; the other half was left unstimulated. At the end of the exposure period, rats were
sacrificed and blood samples collected. The liver, spleen and thymus from each animal were
removed and weighed. The humoral immune response was quantified by measuring
immunoglobulin levels (IgM and IgG), estimating the albumin/globulin ratio and measuring the
ovalbumin antibody titer by ELISA. Cell-mediated response was assessed in vivo, by
quantifying the delayed type hypersensitivity reaction (measuring footpad thickness after
ovalbumin challenge) and in vitro by measuring leukocyte and macrophage migration inhibition.
The latter tests assess whether chemical exposure results in suppression of lymphokine
production. Body weights did not differ between treated and control groups. p,p '-DDE-exposed
rats had significantly (p<0.05) higher relative liver weights (17%) than control animals; spleen
and thymus weights were not affected by treatment. p,p '-DDE treatment resulted in depression
of both humoral and cell-mediated immune responses, based on significant (p<0.05) reductions
in all seven measures. Simultaneous studies with DDT, DDD and DDA showed thatp,p '-DDE
was the most potent immunotoxin. This study establishes a LOAEL of 20 mg/kg-day for
immunotoxicity in male rats fed p,p'-DDE for 6 weeks. A NOAEL was not established.
Mechanistic — You et al. (1999b) evaluated the effect of in utero and lactational
exposure to p,p '-DDE on the postnatal expression of specific hepatic cytochromes that are
involved in testosterone metabolism. Pregnant Sprague-Dawley rats were gavaged with 0, 10 or
100 mg/kg-day ofp,p '-DDE (>99% purity) in corn oil from GD 14 to 18. Exposure to the high
18

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7-26-2007
dose significantly increased the hepatic expression of CYP2A1 enzyme at PND 10 and CYP3A1
enzyme at PND 10 and 21 in male and female offspring; both doses induced the expression of
CYP2B1 at PND 10 and 21 in both genders. These changes were associated with significant
increases in testosterone hydrolase (an enzyme that inactivates testosterone) activity in high-dose
males and females; increases in low-dose rats were not statistically significant.
DERIVATION OF PROVISIONAL SUBCHRONIC AND CHRONIC
ORAL RfD VALUES FORDDK
A few larger human epidemiological studies (Longnecker et al., 2001; Salazar-Garcia et
al., 2004; Ribas-Fito et al., 2006) provide suggestive evidence for an effect ofp,p '-DDE on
preterm birth, birth defects and/or postnatal growth. However, these studies are not considered
adequate for deriving provisional subchronic and chronic RfDs forp,p '-DDE due to potential
confounding and other study design issues (see Human Studies section).
Chronic animal toxicity studies of p,p '-DDE toxicity are available for derivation of an
RfD. In the NCI (1978) study in Osborne-Mendel rats and B6C3F1 mice, the usefulness of the
data is somewhat compromised, however, by the long observation period, which would allow for
recovery from or reversal of some effects and by the substantial adjustments in dietary levels
during the course of treatment. For rats, the lowest TWA dose tested, 12 mg/kg-day in females,
was a FEL associated with liver toxicity and decreased survival. For mice, the lowest TWA dose
tested, 22 mg/kg-day, was a LOAEL for suppression of body weight gain in females and clinical
signs in males. The findings in mice are somewhat compromised by low survival and a high
incidence of amyloidosis in male controls. In the chronic feeding study in Syrian hamsters
(Rossi et al., 1983), also compromised by reduced survival and a high incidence of amyloidosis
in controls, the lowest dose tested, 48 mg/kg-day, constituted a LOAEL for hepatic effects. In
the chronic feeding study in CF-1 mice (Tomatis et al., 1974), the only dose tested, 43 mg/kg-
day, appeared to be an FEL, although the observed mortality may have been largely a result of
the carcinogenic response. Taken together, the chronic studies fail to define a LOAEL or
NOAEL on which an RfD could be based.
A number of developmental studies showed male reproductive effects. The lowest
LOAEL of those studies was 10 mg/kg-day for male reproductive effects in rats (You et al.,
1998). That LOAEL was matched for maternal toxicity (hepatic lesions) in another rat
developmental study (Kornbrust et al., 1986). The only other study suitable as the basis for an
RfD is the immunotoxicity study of Baneijee et al. (1996), in which a LOAEL of 20 mg/kg-day
was established following a 6-week exposure to p,p'-DDE in food.
However, given the mortality observed at 12 mg/kg-day in the NCI (1978) study, none of
the NOAELs or LOAELs established in other studies are low enough to provide adequate
protection. Therefore, the data are judged to be inadequate for the derivation of either a
subchronic or chronic provisional RfD
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DERIVATION OF PROVISIONAL SUBCHRONIC AND CHRONIC
INHALATION p-RfC VALUES FOR DDK
Provisional inhalation RfCs cannot be derived forp,p '-DDE because there are no data
regarding inhalation exposure in humans or animals.
PROVISIONAL CARCINOGENICITY ASSESSMENT FOR
/;,/;'-DDE
IRIS (U.S. EPA, 2007) provides an OSF; no IUR. Inhalation data does not exist to
develop an IUR. No values developed.
REFERENCES
ACGIH (American Conference of Governmental Industrial Hygienists). 2006. Threshold Limit
Values for Chemical Substances and Physical Agents and Biological Exposure Indices. ACGIH,
Cincinnati, OH.
Ahamed, M., M. Anand, A. Kumar et al. 2006. Childhood aplastic anaemia in Lucknow, India:
incidence, organochlorines in the blood and review of case reports following exposure to
pesticides. Clin. Biochem. 39:762-766.
Akkina, J.E., J.S. Reif, T.J. Keefe et al. 2004. Age at natural menopause and exposure to
organochlorine pesticides in Hispanic women. J. Toxicol. Environ. Health A. 67:1407-1422.
Asawasinsopon, R., T. Prapamontol, O. Prakobvitayakit, Y. Vaneesorn, A Mangklabruks and B.
Hock. 2006. Plasma levels of DDT and their association with reproductive hormones in adult
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APPENDIX A. RECENT HUMAN EPIDEMIOLOGICAL STUDIES OF THE
NONCANCER EFFECTS OF p,p'-DDE
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Table A-l. Recent (2001-2006) Human Epidemiological Studies ofp,p'-DDE (Noncancer Effects Only)
Reference
Study Type
Endpoint(s)
Findings
Reproductive/Developmental Outcomes
Axmon etal., 2006
Retrospective
cohort (n=2283)
Time-to-pregnancy
(TTP)
Longer TTP "seemed" to be associated withp,p '-DDE in Greenland group but not in
groups from Warsaw, Kharkiv, and Sweden.
Cohn et al., 2003
Retrospective
cohort (n=289)
Time-to-pregnancy in
daughters
Probability of pregnancy increased 16% per 10 |ig/L p,p '-DDE in maternal serum
Law et al., 2005
Retrospective
cohort (n=390)
Time-to-pregnancy
Fecundability OR* =0.65 (0.32-1.31) for serump,p '-DDE>60 |ig/L: weak/inconclusive
finding
Charlier and Foidart,
2005
Case-control
(n=82 cases and
73 controls)
Male Infertility
p,p '-DDE levels in maternal serum (mothers of infertile men) significantly higher than
controls; serum levels of adult men not different from controls
Karmaus et al., 2002
Cross-sectional
(n=208)
Offspring sex ratio
No result reported in abstract; assume negative for paternal serum p,p '-DDE
Korrick et al., 2001
Case-control
(n=15 cases and
15 controls)
Spontaneous abortion
OR increase of 1.13 (1.02-1.26) for each ng/g increase in serump,p '-DDE
Longnecker et al.,
2005
Retrospective
cohort (n=1717)
Prior fetal loss
Suggestion of adverse effect associated with maternal serum p,p '-DDE but inconclusive
Sugiura-Ogasawara et
al., 2003
Case-control
(n=45 cases and
30 controls)
Recurrent miscarriage
No difference between cases and controls in serum p,p '-DDE levels
Torres-Arreola et al.,
2003
Case-cohort
(n=233)
Preterm birth
Nonsignificant increased risk with increase in maternal serum p,p '-DDE
Farhang et al., 2005
Retrospective
cohort (n=420)
Preterm birth, small-
for-gestational-age,
birth weight,
gestational age
OR for preterm birth was 1.28 (0.73- 2.23) and OR for small-for-gestational-age was
0.75 (0.44- 1.26) per 25 |ig/L of maternal serump,p '-DDE. No significant findings.
Longnecker et al.,
2001
Retrospective
cohort (n=2380)
Preterm birth, small-
for-gestational-age
The adjusted ORs of preterm birth increased with increasing concentration of serum
p,p -DDE (ORs=l, 1.5, 1.6, 2.5, 3.1; trend p<0.0001). Adjusted OR of small-for-
gestational-age also increased, but less consistently (ORs=l, 1.9, 1.7, 1.6, 2.6; trend
p=0.04).
Ribas-Fito et al., 2002
Retrospective
cohort (n=98)
Prematurity, birth
length
Premature newborns had higherp,p '-DDE in cord serum compared with full-term babies
(2.40 vs. 0.80 ng/mL, p<0.05). No association with birth length.
Khanjani and Sim,
2006
Cross-sectional
(n not reported)
Reproductive outcomes
Weak significant correlation (-0.1) between low birth weight in female offspring and
p,p '-DDE in milk
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Table A-l. Recent (2001-2006) Human Epidemiological Studies ofp,p'-DDE (Noncancer Effects Only)
Reference
Study Type
Endpoint(s)
Findings
Fenster et al., 2006
Retrospective
cohort (n=385)
Length of gestation,
birth weight, crown-
heel length
No association between maternal serum p,p '-DDE and any measures.
Karmaus and Zhu,
2004
Retrospective
cohort (n=168)
Birth weight
No significant effect of maternal serum p,p '-DDE.
Gladen et al., 2003
Retrospective
cohort (n=197)
Birth weight
No association between p,p '-DDE in maternal milk and birthweight.
Salazar-Garcia et al.,
2004
Retrospective
cohort (n=9187)
Birth defects,
spontaneous abortion,
sex ratio
Compared with the lowest quartile of estimated p,p '-DDE in fat, the ORs for birth
defects were 2.48 (95% CI, 0.75-8.11), 4.15 (95% CI, 1.38-12.46), and 3.76 (95% CI,
1.23-11.44) for quartiles 2, 3, and 4, equivalent to p,p '-DDE in fat of 50, 82, and 298
Hg/g fat, respectively.
Siddiqui et al., 2003
Case-control (30
cases, 24
controls)
Intra-uterine growth
retardation (IUGR)
IUGR significantly associated with maternal serump,p '-DDE (OR=1.21, 1.03-1.42)
after adjustment for confounders. Birth weight negatively correlated (p<0.05) with both
maternal serum p,p '-DDE and cord blood p,p '-DDE.
Weisskopf et al., 2005
Retrospective
cohort (n=143)
Birth weight
Increased maternal serum p,p '-DDE associated with lower birth weight
Weisskopf et al., 2003
Cross-sectional
(n=385)
Offspring sex ratio
No association with maternal serum p,p '-DDE
Lactation



Karmaus et al., 2005
N.B.: Effect of DDE
on lactation attributed
to o,p-DDE
Retrospective
cohort (n=176)
Lactation initiation and
duration
Incidence ratio of breast-feeding initiation was 0.45 (0.15, 0.94) and 0.42 (0.10, 1.03) for
maternal serum DDE of 5-10 |ig/L and >10 |ig/L. respectively, compared with lowest
DDE exposure group.
Breast-feeding duration was shorter when DDE concentrations were higher: 13 weeks
for >10 |ig/L DDE, compared with 21.7 weeks for lower DDE
Neurodevelopment
Darvill et al., 2000
Prospective
cohort (n= 230
and 216)
Infant intelligence at 6
and 12 months of age
No association between cord blood p,p '-DDE and test scores
Eskenazi et al., 2006
Prospective
cohort (n=360)
Mental and
psychomotor
development at 6, 12,
and 24 months of age
Psychomotor scores decreased 2 points with 10-fold increase in maternal serump,p
DDE at 6 months but not at 12 or 24 months.
30

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7-26-2007
Table A-l. Recent (2001-2006) Human Epidemiological Studies ofp,p'-DDE (Noncancer Effects Only)
Reference
Study Type
Endpoint(s)
Findings
Ribas-Fito et al., 2003
Prospective
cohort (n=92)
Mental and
psychomotor
development at 13
months of age
Mental scale scores decreased 3.5 points and psychomotor scale scores decreased 4.01
points with doubling p,p '-DDE concentration in cord serum.
Postnatal growth
Gladen et al., 2000
Prospective
cohort (n=594)
Pubertal growth and
development
Height of boys at puberty, and weight adjusted for height were greater (increases of 6.3
cm and 6.9 kg) at highest maternalp,p '-DDE levels (4+ ppm fat) than lowest levels (0-1
ppm). No difference with lactational exposures. No effect on girls.




Gladen et al., 2004
Retrospective
cohort (n=304)
Anthrometric and
pubertal measures in
males
No associations between maternal serum p,p '-DDE and any measures.
Karmaus et al., 2002
Cohort (n=343)
Height from birth to
age 10 years
Height reduced by 1.8 cm (p<0.0275) for girls in the highestp,p '-DDE serum
concentration quartile (>0.44 |ig/L) compared with girls in the lowest quartile (0.08-0.2
|ig/L). No effect in boys.
Ribas-Fito et al., 2006
Prospective
cohort (n=1712)
Height at age 1, 4, and
7 years
Highest maternal serump,p '-DDE (> 60 |ig/L) associated with decreased height at age
1,4, and 7 years
Male Reproductive/Hormonal Effects
Asawasinsopon et al.,
2006
Cross-sectional
(n=97)
Reproductive hormones
in men
Significant negative association of plasma E2 levels with plasma p,p '-DDE levels;
association characterized as weak.
Bhatia et al., 2005
Case-control
(n=145 cases,
283 controls)
Cryptorchidism and
hypospadias
Boys with maternal serump,p '-DDE levels >61.0 ng/mL had OR of 1.34 [0.51-3.48] for
cryptorchidism and 1.18 (0.46-3.02) for hypospadias compared with boys with maternal
serum p,p '-DDE levels < 27.0 ng/mL. No significant association.
Damgaard et al., 2006
Nested case-
control (n=62
cases, 68
controls)
Cryptorchidism
(undescended testicles)
No significant difference in maternal milk p,p '-DDE levels between cases and controls.
De Jager etal., 2006
Cross-sectional
(n=116)
Semen characteristics
Percentage of motile sperm decreased with higher serum p,p '-DDE, and percentage of
sperm with morphological tail defects increased with higher p,p '-DDE. The most severe
category of incomplete DNA condensation was also positively correlated with p,p '-p,p
DDE concentration.
Flores-Luevano et al.,
2003
Pilot case-
control (n=41
cases, 28
controls)
Hypospadias
No association between maternal serump,p '-DDE and hypospadias.
31

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7-26-2007
Table A-l. Recent (2001-2006) Human Epidemiological Studies ofp,p'-DDE (Noncancer Effects Only)
Reference
Study Type
Endpoint(s)
Findings
Hauser etal., 2003
Cross-sectional
(n=212)
Semen parameters
Limited evidence of inverse association between serump,p '-DDE and sperm motility.
Longnecker et al.,
2002
Nested case-
control (n=585
cases, 552
controls)
Cryptorchidism,
hypospadias, polythelia
(extra nipples)
Compared with boys whose maternal serum p,p '-DDE level was less than 21.4 |ig/L,
boys with maternal levels greater than or equal to 85.6 |ig/L had adjusted odds ratios of
1.3 (0.7, 2.4) for cryptorchidism, 1.2 (0.6, 2.4) for hypospadias, and 1.9 (0.9, 4.0) for
polythelia. Results inconclusive.
Martin et al., 2002
Cross-sectional
(n=137)
Serum androgens
Total testosterone and free androgen index lower (23% and 22%, respectively) among
men in top tenth percentile of serum p,p '-DDE. Not statistically significant.
Rignell-Hydbom et
al., 2004
Retrospective
cohort (n=195)
Semen characteristics
and reproductive
hormones
No significant associations between p,p '-DDE and any parameters.
Rignell-Hydbom et
al., 2005a
Cross-sectional
(n=176)
Sperm chromatin
integrity
Tendency to lower DNA fragmentation index with lower serum p,p '-DDE but not
statistically significant.
Rignell-Hydbom et
al., 2005b
Cross-sectional
(n=157)
Reproductive gland
function
No significant associations between serum p,p '-DDE and prostate-specific antigen,
neutral alpha-glucosidase, fructose, and zinc in semen.
Rylander et al., 2006
Cross-sectional
(n=196)
Endocrine effects
Significant positive association between serum p,p '-DDE and TSH. TSH increase of
0.03mU/L for each 100 ng/g lipid of p,p '-DDE. Significant negative association
betweenp,p '-DDE and estradiol. Estradiol decrease of 0.57 pmol/L associated with each
lOOng/g lipid increase in p,p '-DDE.
Spano et al., 2005
Cross-sectional
(n=707)
Sperm chromatin
integrity
No association with serum p,p '-DDE.
Tiido et al., 2005
Cross-sectional
(n=149)
Sperm X:Y
chromosome
distribution
Log transformed p,p '-DDE (blood and/or semen) significantly positively associated with
Y chromosome fractions (p<0.001).
Tiido et al., 2006
Cross-sectional
(n=547)
Sperm X:Y
chromosome
distribution
Log-transformed p,p '-DDE (blood and/or semen) was significantly positively associated
with Y-chromosome fractions (p <0.001) in Swedish cohort but not Greenland, Warsaw,
or Kharkiv cohorts.
Toft et al., 2006
Cross-sectional
(n=763)
Semen quality
Blood p,p '-DDE negatively associated with sperm motility in Greenland population and
in compiled dataset.
Turyk et al., 2006
Cross-sectional
(n=56)
Endocrine effects
Significant negative association between estrone sulfate and p,p '-DDE.
Female Reproductive/Hormonal Effects
Akkina et al., 2004
Cross-sectional
(n=219)
Age at natural
menopause
Adjusted mean age at menopause was 1.7 yr earlier in women with serum p,p '-DDE >
23.6 ppb than in women with serump,p '-DDE levels < 5.5 ppb. No consistent dose-
response effect.
32

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Table A-l. Recent (2001-2006) Human Epidemiological Studies ofp,p'-DDE (Noncancer Effects Only)
Reference
Study Type
Endpoint(s)
Findings
Cooper et al., 2002
Case-control
(n=1407)
Age at natural
menopause
Hazard ratio for rate of onset of natural menopause was 1.4 (0.9-2.1) for the top decile of
serum p,p '-DDE compared with values below the median. Association not significant.
Cooper et al., 2005
Retrospective
cohort (n=2314)
Menstrual cycle
characteristics
Some evidence of association between pregnancy levels of serum p,p '-DDE and
irregular cycles. No association with bleeding duration, heavy bleeding, or
dysmenorrhea.
Denham et al., 2005
Retrospective
cohort (n=138)
Age at menarche
No association betweenp,p '-DDE and age at menarche.
Krstevska-
Konstantinova et al.,
2001
Case-control
(n=26 cases and
28 controls)
Precocious puberty
p,p '-DDE levels higher in foreign girls with precocious puberty compared with Belgian
native girls with idiopathic or organic precocious puberty. Statistical comparison not
reported.
Lu et al., 2006
Case-control
(n=79 cases, 42
controls)
Precocious puberty
p,p '-DDE in serum significantly higher in cases than in controls (p<0.01). p,p '-DDE and
volume of uterus showed a positive correlation (r = 0.306, p< 0.01).
Vasiliu et al., 2004
Retrospective
cohort (n=151)
Age at menarche
Increase in maternal serum p,p '-DDE levels of 15 |ig/L reduced age at menarche by 1
year (P = 0.04); however, when body size at menarche was controlled for (subsample of
102 women), p,p '-DDE association was no longer significant.
Windham et al., 2005
Cross-sectional
(n=50)
Reproductive hormones
and menstrual cycle
parameters
Mean luteal phase length was shorter by 1.5 days at highest quartile of serum p,p '-DDE.
With doubling of p,p '-DDE level, cycle length decreased 1.1 day and luteal phase length
decreased 0.6 days. Levels of progesterone metabolites during luteal phase decreased
with higher p,p '-DDE concentration.
Osteoporosis
Beard et al., 2000
Cross-sectional
(n=68)
Bone mineral density in
women
Log of serum p,p '-DDE significantly correlated with reduced bone mineral density (r=-
0.27, p=0.03)
Bohannon et al., 2000
Prospective
cohort (n=103)
Bone mineral density in
women
No correlation betweenp,p '-DDE and bone density in measurements made at 6-month
intervals over 2 years.
Glynn et al., 2000
Cross-sectional
(n=115)
Bone mineral density in
men
Weak association between serump,p '-DDE and decreased bone mineral density.
Wallin et al., 2005
Cross-sectional
(n=380)
Bone mineral density
and bone metabolism
No association between serum p,p '-DDE and bone mineral density or metabolism
markers.
Immune System Function
Cooper etal., 2004
Cross-sectional
(n=137)
Immune system
markers
No association between serump,p '-DDE and IgA. IgG levels decreased with increasing
p,p '-p,p '-DDE levels, 50% decrease in the highest two categories (>6.0 |ig/L) compared
with values <3.0 |ig/L. Prevalence of antinuclear antibodies was somewhat increased
with highest p,p '-DDE exposure but difference was not statistically significant.
Dallaire et al., 2004
Retrospective
cohort (n=199)
Acute infections
Detailed findings forp,p '-DDE not reported; incidence rate ratios apparently somewhat
increased.
33

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7-26-2007
Table A-l. Recent (2001-2006) Human Epidemiological Studies ofp,p'-DDE (Noncancer Effects Only)
Reference
Study Type
Endpoint(s)
Findings
Dewailley et al., 2000
Retrospective
cohort (n=171)
Acute infections
Risk of otitis media increased with higher early breast milk levels of p,p '-DDE. The RR
for 4- to 7-month-old infants in the highest tertile of p,p '-DDE exposure as compared to
infants in the lowest tertile was 1. 87 (1.07-3.26). The RR of otitis media over the entire
firstyearof life also increased with p,p '-DDE (RR, 1.52; 1.05-2.22).
Karmaus et al., 2001
Cross-sectional
(n=340)
Infections and atopic
disorders
p,p '-DDE associated with significantly higher odds ratio for asthma (OR =3.71; 1.10 -
12.56) and immunoglobulin E concentrations above 200 kU/L (OR = 2.28; 1.20- 4.31).
Karmaus et al., 2003
Retrospective
cohort (n=338)
Atopic manifestations
Serum p,p '-DDE modified the protective effect of breast feeding on asthma.
Sunyer et al., 2005
Prospective
cohort (n=468)
Asthma
Wheezing at 4 years of age increased with cord blood p,p '-DDE concentration,
especially at the highest quartile [9% in the lowest quartile (< 0.57 ng/mL) vs. 19% in
the highest quartile (1.90 ng/mL); RR= 2.63 (1.19-4.69)1
Vine et al., 2001
Cross-sectional
(n=302)
Immune system
markers
Individuals with higher plasma p,p '-DDE levels had lowered mitogen-induced
lymphoproliferative activity (p = 0.03) and modestly increased total lymphocytes (p =
0.05) and immunoglobulin A levels (p = 0.04).
Other Endpoints
Ahamed et al., 2006
Case-control
(n=25 cases, no.
controls not
reported)
Aplastic anemia
Serump,p '-DDE higher in cases than in controls but not significant difference.
Rylander et al., 2005
Cross-sectional
(n=380)
Diabetes
Serump,p '-DDE significantly associated with diabetes prevalence (increase of 100 ng/g
lipid corresponded to an OR of 1.05, 95% CI 1.01, 1.09, p = 0.006). Association more
consistent among women than among men.
Schantz et al., 2001
Cross-sectional
(n=180)
Memory and learning
in adults
No association between serum p,p '-DDE and measures of memory and learning.
OR = Odds Ratio
RR = Relative Risk
34

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7-26-2007
APPENDIX B. DETAILS OF BENCHMARK DOSE MODELING
OF NIPPLE RETENTION DATA REPORTED BY LOEFFLER AND PETERSON (1999)
AND YOU ET AL. (1998)
The model fitting procedure for continuous data is as follows. The simplest model
(linear) is first applied to the data while assuming constant variance. If the data are consistent
with the assumption of constant variance (p>0.1), then the fit of the linear model to the means is
evaluated. If the linear model adequately fits the means (p>0.1), then it is selected as the model
for BMD derivation. If the linear model does not adequately fit the means, then the more
complex models are fit to the data while assuming constant variance. Among the models
providing adequate fit to the means (p>0.1), the one with the lowest AIC for the fitted model is
selected for BMD derivation. If the test for constant variance is negative, the linear model is run
again while applying the power model integrated into the BMDS to account for nonhomogenous
variance. If the nonhomogenous variance model provides an adequate fit (p>0.1) to the variance
data, then the fit of the linear model to the means is evaluated. If the linear model does not
provide adequate fit to the means while the nonhomogenous variance model is applied, then the
polynomial, power and Hill models are fit to the data and evaluated while the variance model is
applied. Among those providing adequate fit to the means (p>0.1), the one with the lowest AIC
for the fitted model is selected for BMD derivation. If the test for constant variance is negative
and the nonhomogenous variance model does not provide an adequate fit to the variance data,
then the data set is considered unsuitable for modeling.
Loeffler and Peterson (1999) Nipple Retention on PND 13
Following the above procedure, continuous-variable models in the EPA BMDS (version
1.3.2) were fit to the data shown in Table 3 (page 19) for mean number of nipples retained per
pup (PND 13) in rats exposed to p,p-DDE in utero. Using these data, the constant variance
model did not provide adequate fit to the variance data, nor did the variance model built into the
software. Thus, the full dataset was not considered appropriate for benchmark dose modeling.
Elimination of the highest dose group did not result in a dataset for which the variance could be
properly modeled. Elimination of additional dose groups was not considered, as it would result
in the elimination of all doses that resulted in a statistically significant increase in mean number
of nipples retained per pup. In summary, the nipple retention data reported by Loeffler and
Peterson (1999) were not suitable for benchmark dose modeling. Table B-l shows the results of
the modeling efforts.
35

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7-26-2007
Table B-l. Model predictions for nipple retention on PND 13 in male rats
exposed to p,p'-DDE in utero (Loeffler and Peterson, 1999)
Model
Variance
/>-valuea
Means
p-valueb
BMDiSd
(mg/kg-day)
BMDLiSd
(mg/kg-day)
All dose groups
Linear (constant variance)
<0.0001
0.01256
34.80
21.36
Linear (modeled variance)
<0.0001
<0.0001
0
failed
No high dose group
Linear (constant variance)
<0.0001
0.198
42.29
26.30
Linear (modeled variance)
<0.0001
<0.0001
1.19E-7
1.19E-7
aValues <0.05 fail to meet conventional goodness-of-fit criteria.
bValues <0.10 fail to meet conventional goodness-of-fit criteria.
You et al. (1998) Nipple Retention on PND 13 in Sprague-Dawley rats
Following the above procedure, continuous-variable models in the EPA BMDS (version
1.3.2) were fit to the data for mean number of nipples retained per pup (PND 13) in Sprague-
Dawley rats exposed top,p-DDE in utero. You et al. (1998) reported the means and standard
deviations graphically, and the values were estimated visually for modeling purposes. Table B-2
shows the data as estimated from the graphic presentation.
Table B-2. Number of nipples/pup retained on PND 13 by
Sprague-Dawley rats (You et al., 1998)
Dose
(mg/kg-day)
No. of Nipples/Pup
(mean ±SD)
Number of
Litters
0
0.4 ±0.2
9
10
1.2 ±0.4
8
100
3.8 ±0.6
9
Using these data, the constant variance model did not provide adequate fit to the variance
data. Adequate fit to the variance data was achieved using the variance model built into the
software, but the linear model did not provide adequate fit to the means. There were too few
dose groups to apply the remaining continuous-data models (polynomial, power, or Hill). Thus,
no model provided adequate fit to the data on nipple retention reported by You et al. (1998).
Table B-3 shows the results of the modeling efforts.
36

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7-26-2007
Table B-3. Model predictions for nipple retention on PND 13 in male
Sprague-Dawley rats exposed to p,p'-DDE in utero (You et al., 1998)
Model
Variance
/>-valuea
Means
p-valueb
BMDiSd
(mg/kg-day)
BMDLiSd
(mg/kg-day)
Linear (constant variance)
0.009335
0.02119
14.06
11.20
Linear (modeled variance)
0.6219
0.0007703
9.94
6.71
Polynomial (modeled
variance)
NAC
NA
NA
NA
Power (modeled variance)
NA
NA
NA
NA
Hill (modeled variance)
NA
NA
NA
NA
aValues <0.05 fail to meet conventional goodness-of-fit criteria.
bValues <0.10 fail to meet conventional goodness-of-fit criteria.
cNot applicable; too few dose groups to apply these models.
37

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