September 1992
HEALTH ADVISORY FOR
DIMETHYL METHYLPHOSPHONATE
(DMMP)
Office of Water
U.S. Environmental Protection Agency
Washington, DC 20460
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HEALTH ADVISORY FOR
DIMETHYL METHYLPHOSPHONATE
(DUMP)
AUTHORS:
Jess C. Rowland, M.S.
Margaret E. Brower, Ph.D.
Wei ford C. Roberts, Ph.D.
PROJECT OFFICER:
Krishan Khanna, Ph.D.
Health and Ecological Criteria Division
Office of Science and Technology
Office of Water
U.S. Environmental Protection Agency
Washington, DC 20460
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PREFACE
This report was prepared in accordance with the Memorandum of
Understanding between the Department of the Army, Deputy for Environment
Safety and Occupational Health (OASA(IL&E)), and the U.S. Environmental
Protection Agency (EPA), Office of Water (OW), Office of Science and
Technology for the purpose of developing drinking water Health Advisories
(HAs) for selected environmental contaminants, as requested by the Army.
Health Advisories provide specific advice on the levels of contaminants
in drinking water at which adverse health effects would not be anticipated and
which include a margin of safety so as to protect the most sensitive members
of the population at risk. A Health Advisory provides health effects
guidelines and analytical methods, and recommends treatment techniques on a
case-by-case basis. These advisories are normally prepared for One-day,
Ten-day, Longer-term and Ufetime exposure periods where available
toxicological data permit. These advisories do not condone the presence of
contaminants in drinking water, nor are they legally enforceable standards.
They are not issued as official regulations and they may or may not lead to
the issuance of national standards or Maximum Contaminant Levels (MCLs).
This report is the product of the foregoing process. Available
toxicological data, as provided by the Army and as found in open literature
sources, on the munitions chemicals dimethyl methyiphosphonate (DMMP) have
been reviewed, and relevant findings are presented in this report in a manner
so as to allow for an evaluation of the data without continued reference to
the primary documents. This report has been submitted for critical internal
and external review by the EPA.
I would like to thank the authors who provided the extensive technical
skills required for the preparation of this report. I am grateful to the
members of the EPA Toxicology-Review Panel who took time to review this report
and to provide their valuable input, and I would like to thank Dr. Edward
Ohanian, Chief, Human Risk Assessment Branch, and Ms. Margaret Stasikowski,
Director, Health and Ecological Criteria Division, for providing me with the
opportunity and encouragement to be a part of this project.
The preparation of this Health Advisory was funded in part by
Interagency Agreement (lAG) 85-PP5869 between the U.S. EPA and the U.S. Army
Medical Research and Development Command (USAMRDC). This JAG was conducted
with the technical support of the U.S. Army Biomedical Research and
Development Laboratory (USABRDL), Dr. Howard 1. Bausum, Project Manager.
Krishan Khanna, Ph.D.
Project Officer
Office of Water
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I.
II.
III.
IV.
V.
VI.
111
Paae
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tv-i
V-i
VI -1
Number
TABLE OF CONTENTS
LIST OF TABLES
EXECUTIVE SUMMARY
INTRODUCTION
GENERAL INFORMATION
SOURCES OF EXPOSURE
ENV I RONMENTAL FATE
TOXICOKINETICS
HEALTH EFFECTS
A. Humans VI-1
B. Animal Experiments VI-i
1. Short-term Exposure (<4-week studies) VI-I
a. Acute VI-1
b. Primary Irritation and Skin Sensitization VI-5
c. Subacute VI-6
2. Longer-term Exposure VI-9
a. 13-Week Studies VI-9
b. Lifetime Studies VI-14
3. Reproductive Effects VI- 16
4. Developmental Toxicity VI-22
5. Carcinogenicity VI-23
6. Genotoxicity VI-25
7.Neurotoxicity VI-28
VII. HEALTH ADVISORY DEVELOPMENT VII-1
A. Sunmiary of Health Effects Data Vu-i
B. Quantification of Toxicological Effects. VI 1-4
1. One-day Health Advisory VII-5
2. Ten-day Health Advisory VII-5
3. Longer-term Health Advisory VII-7
4. Lifetime Health Advisory VII-8
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C. Quantification of Carcinogenic Potential VIl-lO
1. Dose-Response Data (Carcinogenicity, Oral Exposure) . . . . Vu-li
2. Summary of Risk Estimates VII-13
3. Drinking Water Concentrations at Specified Risk Levels. . . VII-13
4. Discussion of Confidence (Carcinogenicity,
Oral Exposure) VII-14
VIII. OTHER CRITERIA, GUIDANCE, AND STANDARDS VIII-i
IX. ANALYTICAL METHODS IX-i
X. TREATMENT TECHNOLOGIES X-i
XI. CONCLUSIONS fl-i
XII. REFERENCES XII-1
APPENDIX: Data Deficiencies/Problem Areas and Recommendations for
Additional Data Base Development for DMMP
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LIST OF TABLES
Table No. Page
11-1 General Chemical and Physical Properties of Dimethyl
Methylphosphonate 11-2
VI-l Acute ID 50 Values for DMMP in Laboratory Animals VI-2
VI-2 Summary of Studies: Short-term Exposure of Animals
t0DMMP VI-3
VI-3 Number of Mice With Stomach Lesions After
Oral Administration of DMMP for 15 Consecutive
Days VI-8
VI-4 Summary of Studies: Longer-term Exposure of Animals
to DMMP VI-lo
VI-5 Histopathological Changes In Rats After Oral
Administration of DMMP for 13 Weeks (Study 1) VI-12
VI-6 Histopathological Changes in Rats After Oral
Administration of DMMP for 13 Weeks (Study 2) VI-13
VI-7 Incidences of Kidney Lesions Observed in Male F344N Rats
After Oral Administration of DMMP for 103 Weeks VI-17
VI-8 Analysis of Sperm From Male Fischer-344 Rats
After Oral Administration of DMMP for 90 Days VI-19
VI-9 Changes in the Reproductive Function of Male
Fischer-344 Rats After Oral Administration of
DMMP for 90 Days VI-20
VI-lO Severity and Time Course of Lesions Observed in the
Testes and Epididymis of Male Fischer-344 Rats During
Oral Administration of DMMP for up to 12 Weeks VI-21
VI-il Incidences of Preneoplastic and Neoplastic Lesions
Observed in the Kidneys of Male F344/N Rats After
Oral Administration of DMMP for 103 Weeks VI-24
VI-12 Incidence of Mononuclear Cell Leukemia Observed in
Male F344/N Rats After Oral Administration of DMMP
for 103 Weeks VI-26
VI-13 Mutagenicity of DMMP in Various Test Systems VI-27
Vu-i Summary of Data Used to Quantitate the Carcinogenic
Potential of DMMP VII-12
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EXECUTIVE SUMMARY
Dimethyl methyiphosphonate (DMMP) is a colorless liquid used both in
commercial and military applications. Conunercial uses Include formulations of
resins, latex, coatings, and flame retardants. The military uses DMMP to
simulate nerve agents for testing chemical agent detection equipment and
techniques.
No studies were found in the available literature on the toxicokinetics
of DMMP. However, acute, subchronic, and chronic oral toxicity studies in
mice and rats indicate that DMNP is absorbed via the gastrointestinal tract.
No Information was available on occupational exposure to DMMP. Potential
exposure may occur primarily under occupational settings at production sites
where DMMP is used as a flame retardant and as a viscosity depressant in
polyester and epoxy resins. Military field uses and effluents from commercial
production facilities are potential sources that could contaminate water
sources. Dimethyl methyiphosphonate has been detected in groundwater at one
military installation at levels that range from 6.5 Lg/L to 1,300 g/L.
In a repeated insult patch test with humans, aqueous solutions of DMMP
produced mild skin irritation at a concentration of 10% (v/v) and moderate to
severe irritation at the 20% (v/v) level.
Acute toxicity studies indicate that DMMP exhibits little toxicity when
administered to mice and rats via the oral route; LD 50 values were >6,810
mg/kg in mice and 10,190 mg/kg in rats. Animals exhibited ataxia, tremors,
unsteady gait, muscular hypertonia and hypotonia, prostration, and reductions
in spontaneous motility. DMMP was slightly toxic by the intravenous route;
LU 50 values were 912 and 1,050 mg/kg in mice and rats, respectively. DMMP
elicited mild skin irritation and minimal ocular irritation in rabbits. OMMP
was negative as a skin sensitizer in rabbits.
Oral administration of DMMP in tapwater at 0, 1, 10, 100, or 1,000
mg/kg/day for 3 days to male and female rats produced no adverse effects on
mortality, clinical signs, body weight, or food consumption. Plasma
cholinesterase levels were depressed only in rats treated with 1,000
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mg/kg/day; approximate reductions of 30% in males and 40-50% in females were
observed over a 4-hour period as compared with control values taken at the
same time. No effects on plasma cholinesterase levels were observed in rats
at the other dose levels. The No-Observed-Adverse-Effect Level (NOAEL) was
100 mg/kg/day based on plasma cholinesterase activity depression.
The profile of some kidney effects observed in the DMMP-treated male rats
is consistent with that of alpha-2-microglobulin (alpha 2 globulin)
nephrotoxicity. This protein is synthesized in the liver of the male rat and
has not been detected in female rats. It has not been detected in any other
species, including humans. Because this protein appears to occur only in the
male rat, alpha 2 globulin nephrotoxicity, and subsequent effects, are not
expected to occur in other species. Thus, some DMMP-induced renal
noncarcinogenic and carcinogenic effects were not considered to be relevant to
humans.
In a 15-day study with a limited number of mice and rats
(five/sex/species), histologic changes were observed in the stomachs of male
mice receiving 1,250 mg DMMP/kg/day by oral intubation and in females
receiving 5,000 mg/kg/day. The Lowest-Observed-Adverse-Effect Level (LOAEL)
was 1,250 mg/kg/day, based on the histologic changes in the stomach of male
mice. No gross pathological changes were seen in male or female rats at
levels up to 15,000 mg/kg/day; however, mortality was seen in both sexes dosed
at 5,O00 mg/kg/day. Neither a NOAEL nor LOAEL was established in rats
because a target organ for toxicity was not identified and histopathology was
not conducted.
In a 4-week dietary study with rats, DMMP caused an increase in the
protein resorption droplets (hyaline droplets) in the proximal convoluted
epithelium of the kidneys of males fed diets containing 2,000, 6,000, or
20,000 ppm (178, 535, or 1,790 mg/kg/day, respectively); the effect in males
was more pronounced with increasing levels of DMMP and was not observed in
females. The LOAEL for this study is 6,000 ppm (535 mg/kg/day) based on
increased kidney weights in female rats; the NOAEL is 2,000 ppm (178
mg/kg/day).
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In a subchronic toxicity study, male and female mice were administered
OMMP, by gavage, at doses ranging from 250 to 8,000 mg/kg, 5 days/week for 13
weeks. Except for mortality in both sexes at higher (4,000 or 8,000 mg/kg)
dose levels, no adverse effects on body weight, clinical signs, food
consumption, gross necropsy, or histopathology were observed. The stomach
lesions observed in the 15-day study were not seen in this study. No
compound-related cause for the mortality at the two upper levels was reported.
Therefore, neither a NOAEL nor LOAEL was established.
In a subchronic toxicity study, male and female rats were administered
OMMP, by gavage, at doses ranging from 250 to 4,000 mg/kg, 5 days/week for 13
weeks. DMMP, at doses 2,000 mg/kg, caused decreased survival, body weight
gain, and increased liver-to-body weight ratios in males and females.
Histopathology revealed kidney changes (nephrosis and hyaline droplet
generation) in males at all dose levels starting at 250 mg/kg; no
histopathological changes were seen in the kidneys of females. The kidney
lesions are considered to be associated with alpha 2 globulin found only in
male rats and therefore not appropriate for determining a LOAEL. The minimal
to mild hypospermatogenesis seen in the testes of treated rats was not dose
dependent. Based on increased relative liver weights in males and females,
the LOAEL is 2,000 mg/kg/day and the NOAEL is 1,000 mg/kg/day.
In a chronic toxicity study, DMMP was administered, by gavage, at doses
of 0, 1,000, or 2,000 mg/kg, 5 days/week for 103 weeks, to male and female
mice. Survival was decreased in males at both dose levels and in females at
the high dose because of fighting in males and dosing errors in females. Mean
body weights were decreased in both sexes in the high-dose group, and the
incidence of hepatocytomegaly was increased in treated males at both levels
compared with vehicle controls. No increases in nonrieoplastic liver lesions
were seen in female mice. This study was judged to be inadequate owing to
poor survival; therefore, neither a NOAEL nor LOAEL was established.
DMMP was administered, by gavage, at doses of 0, 500, or 1,000 mg/kg to
male and female rats, 5 days/week for 103 weeks. Survival and mean body
weights were decreased in both sexes at the high dose. Treatment-related
kidney changes observed in males at both levels included nephropathy and
calcification of the renal papilla. No kidney lesions were seen in females.
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Discounting the kidney lesions observed in males due to alpha 21 globulin, the
LOAEL is 1,000 mg/kg/day and the NOAEL is 500 mg/kg/day based on decreased
body weights in both sexes.
DMMP was found to be noncarcinogenic to female F344/N rats and male or
female B6C3F 1 mice. However, on the basis of poor survival in both sexes (see
discussion above), the study with mice was judged to be inadequate to evaluate
the carcinogenic potential of DMMP.
DMMP was carcinogenic to male F344/N rats, as shown by an increased
incidence of mononuclear cell leukemia, hyperplasia of the transitional
epithelium, and transitional cell papilloma or carcinoma (combined) of the
kidneys following oral administration at doses of 500 or 1,000 mg/kg, 5
days/week for 103 weeks. Increased incidences of tubular cell hyperplasia and
adenocarcinomas were considered to be related to alpha 2 globulin and not
relevant to estimating human cancer risk. DMMP is classified in Group C:
Possible Human Carcinogen.
OMMP exhibited mutagenicity by inducing forward mutations in mouse
lymphoma cells in the absence of metabolic activation and sister chromatid
exchanges in Chinese hamster ovary (CHO) cells with and without activation.
It gave limited evidence of clastogenicity in CHO cells in the absence of
metabolic activation. jj viva , DMMP induced sex-linked recessive lethal
mutations in Drosophila . DMMP was nonmutagenic in bacterial mutagenicity
tests in several strains of Salmonella , did not Increase neoplastic
transformations in BALB/c 313 cells, and did not Induce reciprocal
translocations in Drosophila j. vivo . DMMP gave positive results in dominant-
lethal assays in mice and rats.
DMtIP was shown to be toxic to the male reproductive system. DMMP induced
dose-dependent decreases in sperm motility, sperm counts, and the male
fertility index in male rats following oral administration at doses ranging
from 250 to 2,000 mg/kg, 5 days/week for 90 days. Histologic changes were
observed in the testes, epididymis, and prostate glands. OMMP altered
reproductive functions at all dose levels by causing a decrease in the number
of live fetuses per litter and an increase in the percentage of resorptlons.
The LOAEL for reproductive effects was the lowest dose tested, 250 mg/kg/day.
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In an inhalation study, exposure of male rats to DMMP vapors at concentrations
of 25 or 250 ppm continuously for 90 days induced histologic changes in the
testes and epididymis.
DMMP was not found to be teratogenic. No developmental effects were
observed In mice following oral administration at 4,175 mg/kg/day on gestation
days 6-13. In another study, when administered to rats during gestation days
6-15, DMMP induced minimal fetotoxicity (reduced fetal weight and delayed
skeletal maturation) only at maternally toxic (1,000 or 2,000 mg/kg/day)
doses. No maternal toxicity, embryotoxicity, or fetotoxicity was observed at
the 100-mg/kg/day dose. Fetal anomalies were within the historical range and
were not considered to be compound related.
No delayed neurotoxicity was seen In hens observed for 21 days following
oral administration of 1,999 or 3,998 my DMMP/kg initially and after 21 days.
However, birds exhibited acute toxicity, including ataxia, curved position,
apathy or sedation, and fluttered feathers. In another study, a single
intraperitoneal injection of 50 my DMMP/kg daily for 10 days produced no
delayed neurotoxicity in hens.
Based on increased relative liver weights In rats administered DMMP via
gavage, the longer-term Health Advisory (HA) for exposure in a 10-kg child is
2 mg/I (2,000 g/L). In the absence of adequate animal data to determine a
One-day or Ten-day Health Advisory, the Longer-term HA for a 10-kg child,
2 mg/I (2,000 gig/I), is used as a conservative estimate of the One-day or
Ten-day HA. The Longer-term HA for an adult is 6 mg/L (6,000 j. g/L). The
Lifetime HA of 0.1 mg/L (100 jLg/L) is for a 70-kg adult, based on a Drinking
Water Equivalent Level (DWEL) of 7 mg/L (7,000 g/L). The DWEL is based on a
Reference Dose (RfD) of 0.2 mg/kg/day. The RfD is based on a LOAEL of 179
mg/kg/day, where the effect was increased resorptions in female rats that were
impregnated by males that had been gavaged with DMMP for 13 weeks.
DMMP is classified as Group C: possible human carcinogen. Its cancer
potential was considered in the development of the lifetime HA. The estimated
cancer risk associated with lifetime exposure to drinking water containing
DMMP at the level of the DWEL (7 mg/L) is approximately 1 x i0 (the actual
calculated value is 7 x 1O ). Derived by the linearized multistage
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extrapolation method, the slope factor that was derived from oral exposure
studies (oral slope factor, q 1 *) for DMMP is 5 x I0 (mg/kg/day)’ and the
drinking water unit risk is 1 x iO per g/L. At concentrations of 700 g/L,
70 g/L, and 7 g/L, excess cancer risks are estimated to be iO 4 , 10 , and
106, respectively, based on equivocal evidence of carcinogenicity. For
comparison, drinking water concentrations associated with a 106 cancer risk
are 2 g/L by the one hit model and less than 1 x i0 g/L for the multihit,
probit, logit, and Weibull models.
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I. INTRODUCTION
The Health Advisory (HA) Program, sponsored by the Office of Water (OW),
provides information on the health effects, analytical methodology, and
treatment technology that would be useful in dealing with the contamination of
drinking water. Health Advisories describe nonregulatory concentrations of
drinking water contaminants at which adverse health effects would not be
anticipated to occur over specific exposure durations. Health Advisories
contain a margin of safety to protect sensitive members of the population.
Health Advisories serve as informal technical guidance to assist
Federal, State, and local officials responsible for protecting public health
when emergency spills or contamination situations occur. They are not to be
construed as legally enforceable Federal standards. HAs are subject to change
as new information becomes available.
HAs are developed for One-day, Ten-day, Longer-term (approximately 7
years, or 10% of an individual’s lifetime), and Lifetime exposures based on
data describing noncarcinogenic endpoints of toxicity. For those substances
that are known or probable human carcinogens, according to the Agency
classification scheme (Group A or B), Lifetime HAs are not recommended. The
chemical concentration values for Group A or B carcinogens are correlated with
carcinogenic risk estimates by employing a cancer potency (unit risk) value
together with assumptions for lifetime exposure and the consumption of
drinking water. The cancer unit risk is usually derived from the linear
multistage model with 95% upper confidence limits. This provides a low-dose
estimate of cancer risks to humans that is considered unlikely to pose a
carcinogenic risk in excess of the stated values. Excess cancer risk
estimates may also be calculated using the one-hit, Weibull, logit, and probit
models. Current understanding of the biological mechanisms involved iii cancer
does not suggest that any one of these models is able to predict risk more
accurately than another. Because each model is based upon differing
assumptions, the estimates that are derived can differ by several orders of
magnitude.
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II. GENERAL INFORMATION
Dimethyl inethyiphosphonate (CAS No. 756-79-6), commonly known as DMMP,
is a low-viscosity, colorless liquid that is miscible in a variety of
industrial solvents and miscible to soluble in water (Aldrich, 1988; U.S. EPA,
1983). It contains high levels of phosphorus (25% by weight), and is
therefore highly efficient, on a weight basis, as a flame retardant. The
general chemical and physical properties of DMMP are presented in Table TI-i.
DMMP is used for a variety of purposes In both commercial and military
activities. Fyrol DMMP, an additive, high-phosphorus flame retardant, may be
used in formulations where its good solvent power, low viscosity, and high
phosphorus content are desired. Recommended applications include use in epoxy
resins, acrylic latexes, unsaturated polyester, urethane coatings, urethane
rigid foam, and vinyl copolymers (Stauffer, 1980, as cited in U.S. EPA, 1983).
DMMP is also a nerve gas “simulant” (i.e., structural analog of nerve
agents but with much lower acute toxicity). DMMP is structurally similar to
the nerve gas GB (isopropyl methyiphosphonofluoride) and is used as a simulant
in testing methods for trapping and destruction of nerve gas in air (Berkowitz
et al., 1978). Nerve gas simulants are used in the military to test equipment
such as chemical protective masks and chemical detection systems (Dunnick et
al., 1984a). DMMP has been used by the U.S. Armed Forces in experimental
situations (Dunnick et al., 1983), which have included releasing DMMP
canisters at geographically isolated proving grounds and then monitoring the
dispersion of the plume.
Other applications of DMMP, which revolve around its viscosity-
depressant effect and its volatility, include use as a solvent, reaction
medium, or catalyst; methylating reagent; preignition additive for gasoline;
antifoam agent; plasticizer and stabilizer; textile conditioner and antistatic
agent; additive in solvents and low-temperature hydraulic fluids; and chemical
intermediate in the production of other flame retardants. DMMP is also used
in heavy metal extraction and solvent separation (Kirk-Othmer, 1980; U.S. EPA,
1983).
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Table Il-i. General Chemical and Physical Properties of Dimethyl Methyiphosphonate
Property Value Reference
CAS Registry Number 756-79-6 Aldrich (1988)
Synonyms Dimethyl methanephosphonate; U.S. EPA (1983)
DMMP;
Fyrol DMMP;
Methanephosphonic acid dimethyl ester;
Phosphonic acid, methyl-, dimethyl
ester
Molecular Formula CH 3 P(0)(OCH 3 ) 2 Aldrich (1988)
Molecular Weight 124.08 Aldrich (1988)
Chemical Structure
H,CO— P—OCX,
C X,
Physical State Colorless liquid Aibright and Wilson
(1982)
Melting Point <50°C Stauffer (1980a)
Boiling Point 181°C Aldrich (1988)
Density 1.145 Aldrich (1988)
Vapor Pressure <0.1 torr @ 20C U.S. EPA (1983)
1.0 torr @ 30°C
1.1 torr 0 10°C
2.4 torr 0 25°C
5.4 torr 0 37.8°C
10.0 torr 0 62.5°C
20.0 torr @ 65°C
Solubility
Water Soluble Albright and Wilson
(1982)
Soluble U.S. EPA (1983)
Solvents Miscible in alcohol, ether, benzene, Aibright and Wilson
acetone, carbon tetrachioride; (1982)
insoluble in heavy mineral oil.
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Table 11-1 (cont.)
Property
Value
Reference
Refractive Index
1.411
U.S.
EPA (1983)
Log P octanol/water
(estimated)
0.46
U.S.
EPA (1983)
Log octanol/water
partition coefficient
(K 0 ) (Fragment method)
-1.88
PMRMA
(1990)
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DMMP is produced by the molecular rearrangement of trimethyiphosphite,
in a reaction catalyzed by a halogenated organic compound (Kirk-Othmer, 1980;
U.S. EPA, 1983). Mobil Chemical Company in Charleston, SC, is the only
current U.S. manufacturer of DMMP listed In the available literature.
Production estimates for 1977 were reported to be from 100,000 to 1 million
pounds (U.S. EPA, 1983).
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III. SOURCES OF EXPOSURE
No information concerning occupational or environmental DMMP exposure
concentrations was found in the available literature. However, considering
its low acute toxicity and irritancy , and its high vapor pressure, little
warning of exposure to DMMP may be given; therefore, there is a potential for
high exposure (U.S. EPA, 1983).
Potential water contamination could occur from military and commercial
sources. When OMMP is used by the military as a nerve gas simulant, it may be
released to the environment (U.S.EPA, 1983). During production, DMMP may be
released to the environment in waste effluent. Quantitative data on military
or commercial environmental releases is limited. In 1989, DMMP was detected
in groundwater at the Rocky Mountain Arsenal (RIIA), Colorado, at
concentrations that ranged from 6.5 Mg/I to 1,300 jig/L (PMRMA, 1991).
In 1991, OMMP was detected in groundwater at two RMA sites at concentrations
of 490 g/L and 760 g/L, respectively.
DMMP has high water solubility and volatility. It evaporates slowly
from aqueous solutions and, therefore, should enter air and water in the
environment (U.S. EPA, 1983).
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IV. ENVIRONMENTAL FATE
Little information is available concerning the environmental fate of
DMMP. The dialkyl alkyiphosphonates (e.g., DMMP) are characterized as neutral
esters that undergo few chemical reactions. The group is resistant to oxygen,
oxidizing agents, and reducing agents (U.S. EPA, 1983). DMMP is, however,
subject to hydrolysis and ultraviolet (uv) photolysis.
Christol et al. (1968) studied the hydrolysis of phosphonates by alkali
in aqueous dioxane. The pK values at 20’C in water and water:dioxane (50:50)
are reported to be 2.37 and 3.11, respectively. Mabey and Mill (1978)
conducted a critical literature review of the hydrolysis of organic compounds
in water under environmental conditions. Their objective was to use this data
to estimate persistence in freshwater aquatic systems. The hydrolysis of
pentavalent phosphorus compounds (e.g., DMMP) occurs by nucleophilic
displacement at the phosphorus- or carbon-oxygen bond with the formation of
leaving groups. Phosphorus-oxygen cleavage is more common with base
hydrolysis; as pH is lowered, a decrease in the overall rate of hydrolysis is
observed. Estimated environmental acid and base hydrolysis rate constants for
DMMP were 1.36 x iO and 2.5 x iO M’s 1 , respectively. The reported
environmental half-life is est mated to be 88 years at 298°K and pH 7.
Extrapolations from studies of DMMP hydrolysis to reaction temperatures of 80,
90, and 98°C indicate a half life of 13 years at 15°C (Berkowitz etal.,
1978).
Laser-induced photodestruction of DMMP was studied by Radziemski (1981).
Experiments were carried out with the liquid and gaseous forms of DMMP.
Liquid DMMP irradiated (time not reported) at 266 nm had a carbon atom quantum
yield of 1.0%, and gaseous DMMP irradiated at 193 nm for 30 minutes had a
yield of 8.4%. Dissociation products were simple hydrocarbon gases, CO, CO 2 .
H 2 , and H 2 0.
The average half-life of DMMP on Cheat grass, in soil, and in water were
estimated in environmental chambers (U.S. EPA, 1983). Corresponding values
for the above media were a few hours, 12.4 days, and 1 to 30 weeks. The half-
life values (not given) indicated a more rapid disappearance at higher
temperatures. Various environmental fate processes may have been represented
IV- I
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(hydrolysis, photolysis, biodegradation), and the major fate mechanism may
have been volatilization.
Based on the available data, DMMP would be expected to be stable in
aqueous environments. Photolysis is not expected to be a major fate, and
hydrolysis is extremely slow; therefore, DMMP is expected to be moderately
persistent in the environment.
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V. TOXICOKINETICS
No information was found in the available literature on the
toxicokinetics (absorption, distribution, metabolism, and excretion) of DMMP
in animals or humans. However, acute, subchronic, and chronic oral toxicity
studies in mice and rats indicate that DMMP is absorbed via the
gastrointestinal tract.
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VI. HEALTH EFFECTS
A. HUMANS
In a repeated-insult patch test with humans, a series of nine 24-hour
occluded induction patches of DMMP were applied to 50 subjects (25 males and
25 females). DMMP (0.05 ml) was tested initially as a 20% (v/v) aqueous
solution; after the sixth application, the dose was reduced to the 10% (v/v)
level for the remaining applications. The induction phase was followed 12
days later by a single challenge with DMMP to detect sensitization. At the
20% level, DMMP induced moderately severe skin irritation by the sixth
application; at the 10% level, DMMP caused very slight to mild skin
irritation. One subject showed a Grade 4 irritation after the challenge dose.
The reaction did not persist beyond 24 hours; consequently, this was not
considered to be a sensitizing response. DMMP was classified a moderate
irritant at a concentration of 20% and a mild irritant at 10%. DMMP was
classified as a non-skin-sensitizer (Ciba-Geigy, 1976a).
B. ANIMAL EXPERIMENTS
1. Short-tern ExDosure (<4-week studies )
a. Acute
The acute toxicity data are summarized in Table VI-1. A summary of
short-term studies for DMMP is presented in Table VI-?. DMMP exhibits little
toxicity when administered to rats and mice via the oral route; the acute oral
LD 50 values are 10,190 mg/kg in rats and >6,810 mg/kg in mice.
In an oral toxicity study, groups of five male and five female Tif:RAIf
rats were given a single dose, by gavage, of undiluted DMMP at 1,000, 3,000,
4,500, 6,000, 8,000, 10,000, or 15,000 mg/kg, and the animals were observed
for 15 days. No deaths were seen in rats dosed at 1,000 to 6,000 mg/kg.
Mortality occurred in one female dosed at 8,000 mg/kg, in one male and four
females dosed at 10,000 mg/kg, and in all animals dosed at 15,000 mg/kg. Rats
at all dose levels exhibited ataxia, muscular hypotonia, prostration,
hypoventilation, and reduced spontaneous motility. Pharmacotoxic signs lasted
VI -1
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Table VI-1. Acute LD 50 Values for DMMP in Laboratory Animals
Species
Strain
Sex
Route
Vehicle
1D
(mg/kg)
Reference
Mouse
86C3F ,
M.F
Oral
Corn oil
>6.810
NIP (1987)
Mouse
hf: MAGf
14.F
Intravenous
O lstilled
water
912
Ciba-Geigy
(1977a)
Rat
Tif: RAIf
M.F
Oral
None
10.190
(9.140—11 ,360)
Ciba-Geigy
(19mb)
Rat
F344/N
M ,F
Oral
Corn oil
‘6.810
NIP (1987)
Rat
M.F
Oral
--
‘5,000
Stauffer
(1983)
Rat
hf: RAIf
M.F
Intravenous
DistlUed
water
1.050
(940—1.180)
CIba-Geigy
(1977a)
Rat
hf: RAIf
M.F
Dermal
Undiluted
‘4.600
Ciba—Geigy
(1976c)
Rabbit
--
——
Dermal
-—
‘2.000
Stauffer
(1983)
The values in parenthesis are 95% confidence limits.
bData not reported.
VI -2
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Table VI-2 Sumary of Studies: Short-term Exposure of Animals to DMMP
Reference
SDecies
Dose
(mg/kg/day) 8
Route
Duration
(days) 8
Ciba-Geigy 197Gb
Rat
1,000 - 15.000
Oral
LD
Stauffer. 1983
Rat
5.000
Oral
LD
Rabbit
2.000
Derinal
LD ,
NIP, 1987
Rat, Mouse
1,470 - 6,810
Oral
LD
Ciba-Geigy. 1977a
Rat
600 - 1,500
Intravenous
LD
Mouse
100 - 930
Intravenous
LD
Ciba-Geigy. 1977b
Rat
1.355 ± 107 mg/rn’
2.589 ± 176 mg/rn’
(rn)
(f)
Inhalation
1 ( 14 )b;
Ic ,.
Ciba-Geigy, 1976c
Rat
4 mL/kg
Dermal
1(8)
Ciba-Geigy. 1978a
Rat
1, 10. 100. 1.000
Oral
3
Ciba-Geigy, 1976d
Rabbit
278 - 337
Dermal
1(3)
Ciba-Geigy, 1976e
Rabbit
0.5n1 (1. 10. 20,
50% sol)
Dermal
1(3)
Ciba-Geigy, 1976f
Rabbit
0.1 g
Ocular
1(14)
Ciba-Geigy, 19769
Guinea Pig
0.5 ml (10% sol)
Dermal
1(14)
NTP, 1987
Rat
0, 1, 250, 2.500,
10,000, 15,000
5.000,
Oral
15
Mouse
0, 1, 250. 2,500.
10,000. 15.000
5,000,
Oral
15
Ciba-Geigy, 1977c
Rat
0, 178, 535
Diet
30
aUnless otherwise stated.
bn(n) = days dosed (total days).
-------
for >6 hours and were not seen after 24 hours. Rats receiving the high dose
exhibited cyanosis in addition to all the above signs and died within 24 hours
(Ciba-Geigy, 1976b). The acute oral LD 50 in male and female rats was reported
to be >5,000 mg/kg and a dermal LD 50 in rabbits was 2,000 mg/kg; study details
(species, number of animals, effects, etc.) were not provided (Stauffer,
1983).
The National Toxicology Program (NTP) conducted single-dose toxicity
studies in male and female B6C3F 1 mice and F344/N rats. Groups of five males
and five females of each species were administered DMMP in corn oil, by
gavage, at doses of 1,470, 2,150, 3,160, 4,640, or 6,810 mg/kg. Animals were
observed for 14 days. Mortality occurred in two of five female mice at the
highest dose; no other deaths were seen. Mice at the two highest dose levels
exhibited transitory inactivity 1 to 4 hours postdosing. In rats, no
treatment-related deaths occurred at doses up to 6,810 mg/kg. Clinical signs
observed 1 to 4 hours postdosing in all but the lowest dose (1,470 mg/kg)
included transitory Inactivity, unsteady gait, and prostration (NIP, 1987).
Ciba-Geigy (1977a) studied the toxicity of DMMP following intravenous
(iv) injection to Tif:MAGf mice and Tif:RAIf rats. Groups of five male and
five female mice were given a single iv injection of DMMP diluted in distilled
water at 100, 300, 600, 800, 900, 910, 920, or 930 mg/kg. DMMP was slightly
toxic by this route; the LD 50 in mice was 912 mg/kg. Mice at all dose levels
exhibited ataxia, roughness of the hair coat, restlessness, humpback, tremors,
ventricumbency, labored respiration, muscular hypertonia, exophthalmos,
twitching muscles, salivation, lacrimation, convulsions, and reduced
spontaneous motility.
In the study with rats, groups of five males and five females were given
a single iv injection of 600, 800, 1,000, 1,200, or 1,500 mg/kg DMMP diluted
in distilled water. DMMP was slightly toxic; the ID 50 was 1,050 mg/kg.
Mortality occurred in all but the lowest dose. Clinical signs of toxicity
observed in rats at all dose levels were similar to those observed in mice
(Ciba-Geigy, 1977a).
In an inhalation study, groups of 10 male and 10 female Tif:RAIf (SPF)
rats were exposed, nose-only, to aerosol concentrations of 1,355 ± 107 or
VI -4
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2,589 ± 176 mg OMMP/m 3 for 4 hours and observed for 14 days. No mortality was
seen at either concentration. Rats at both concentrations exhibited
convulsions, exophthalmos, lateral or ventral position, and ruffled fur.
These signs became more pronounced with increased concentration, but the rats
recovered within 6 to 7 days. Necropsy revealed hemorrhages in the lungs and
“congested organs” (Ciba-Geigy, 1977b).
In a dermal toxicity study, five male and five female Tif:RAIf (SPF)
rats received a single 24-hour derrnal application of undiluted DMMP (4.0
mL/kg) on their shaved backs. No deaths were seen during an 8-day observation
period, and the animals exhibited neither local effects nor systemic toxicity
(Ciba-Geigy, 1976c).
Ciba-Geigy (1978a) assessed the effects of DMMP on plasma cholinesterase
activity in Sprague-Dawley rats. Groups of five males and five females were
orally administered, by gavage, DMIIP mixed in tapwater at doses of 1, 10, 100,
or 1,000 mg/kg body weight (bw) once daily for 3 days. The dose volume was 10
mi/kg. A control group of 10 males and 10 females received only tapwater at
the same rate. Blood samples for plasma cholinesterase measurements were
taken pretest, and 0.5, 1, 2, and 4 hours after the third administration. All
survivors were sacrificed after 3 days, but no necropsies were performed. No
mortality occurred, and no differences were observed in daily body weight or
food consumption. Rats showed no signs of clinical toxicity. Plasma
cholinesterase levels were depressed only in rats treated with 1,000 mg/kg/day
DMMP. Approximate reductions of 30% in males and 40 to 50% in females were
observed over a 4-hour period as compared with control values taken at the
same time. No effects on plasma cholinesterase levels were observed in rats
at the other dose levels. In this study, the NOAEL of DMMP for plasma
cholinesterase depression was 100 mg/kg/day.
b. Primary irritation and skin sensitization
DMMP (0.5 mL) elicited minimal irritation when applied to the intact
skin and slight irritation when applied to the abraded skin of three male and
three female Russian rabbits (weighing 1.7 to 2.0 kg) under 24-hour occlusive
patch conditions. Assuming 100% purity of the test compound, the dose ranged
VI -5
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from approximately 278 mg/kg to 337 mg/kg. No irritation was noted 72 hours
postapplication (Ciba-Geigy, 1976d).
In a primary skin irritation test, groups of two albino rabbits (sex not
reported) received a dermal application of 0.05 ml of DMNP at concentrations
of 1, 10, 20, or 50% in tapwater. Test sites were scored at 24 and 72 hours.
DMIIP was a nonirritant at 1, 10, or 20%. A slight irritation was noted at the
50% level (mean primary irritation score = 0.8/8.0) after 24 hours, which
disappeared 72 hours postapplication (Ciba-Geigy, 1976e).
DMMP caused minimal ocular irritation when instilled (0.1 g) into the
conjunctival sac of the left eye of three male and three female rabbits for I
minute before being washed off. The irritation consisted of conjunctival and
corneal reaction (Ciba-Geigy, 1976f).
In a skin sensitization test, DMMP was shown to be a non-skin-
sensitizer. Ten albino guinea pigs were exposed to 0.5 ml of a 10% (w/v)
aqueous solution of DMMP for 5 hours followed 2 weeks later with a challenge
dose of DMMP (Ciba-Geigy, 1976g).
c. Subacute
The National Toxicology Program (NTP, 1987) conducted a subacute
(15-day) oral toxicity study of DMMP in male and female B6C3F 1 mice and F344/N
rats. Groups of five males and five females of each species were administered
DMMP in corn oil, by gavage, at 0, 1,250, 2,500, 5,000, 10,000, or 15,000
mg/kg/day for 15 consecutive days. The 15,000-mg/kg dose for mice was
administered neat, i.e., without vehicle. All animals were observed twice
daily, and body weight measurements were taken on study days 0 and 15 for mice
and on day 0 for rats. Necropsies were performed on all animals; the stomachs
of all mice underwent histopathological examination.
Mortality occurred in 4/5 male and 5/5 female mice at the 10,000-
mg/kg/day level and in all mice at the 15,000-mg/kg/day level. Mice that died
at these levels exhibited inactivity, prostration, and shallow breathing
before death. Histopathology revealed increased incidence of stomach (fore-
or glandular section not specified) lesions (gastropathy, gastritis,
VI-6
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hyperkeratosis, or epithelial ulceration) in females in the three highest dose
groups and in males (squamous atrophy, gastropathy, or gastritis) in all dose
groups (Table VI-3). Treatment-related deaths were seen in 4/5 male rats and
4/5 female rats dosed at 5,000 mg/kg and in all rats in the two highest dose
groups. Rats treated at 2,500 mg/kg/day were inactive after dosing, and
animals treated at 5,000 or 10,000 mg/kg/day had unsteady gait. No treatment-
related gross pathology was seen.
In this study, based on stomach lesions, the IOAEL was 1,250 mg/kg/day
for male mice and 5,000 mg/kg/day for female mice. Since histopathology was
not performed and no target organs were identified in the rats, a LOAEL or
NOAEL cannot be established.
The toxic effects of subacute (4-week) dietary administration of DMMP
were evaluated in Sprague-Dawley rats (Ciba-Geigy, 1977c). DMMP was included
in the daily diets of five rats/sex/dose for a 1-month period at the following
concentrations: 0, 2,000, or 6,000 ppm (0, 178, or 535 mg/kg/day,
respectively). An additional group of 10 male and 10 female rats were fed
diets containing 20,000 ppm (1,790 mg/kg/day) for the same period; 10 rats
(5 males and 5 females) from this group were retained for 4 weeks on a control
diet after cessation of treatment (recovery group). Animals were observed
daily, and body weights and food consumption were measured weekly.
Ophthalmological examinations were performed on all rats prior to initiation
of treatment and on five males and five females from the 20,000-ppm group
during study weeks 5 and 8. A battery of hematological and clinical chemistry
tests and urinalyses was conducted on all rats at study termination. All
animals underwent gross necropsy, and the adrenals, kidneys, heart, brain,
liver, and gonads were weighed. All major organs underwent histopathological
examination.
No deaths were seen during the study at any dietary level. Body weights
and food consumption were within normal limits, and no signs of toxicity were
observed. Hematology, clinical chemistry, urinalysis, and eye exams revealed
no treatment-related effects. At the 20,000-ppm level, kidney weights in both
sexes and liver weights in males were significantly (p <0.05) increased on
both an absolute and relative basis. At the 6,000-ppm level, kidney weights
VI-7
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Table VI-3. Number of Mice With Stomach Lesions After Oral
Administration of DMMP for 15 Consecutive Day?
Lesion
Dose
(ma/ka)
0
1.250
2.500
5.000
10.000
15.000
Males
No. of animals examined
5
5
5
5
5
5
Insufficient tissue for
evaluation
0
0
1
0
1
0
Autolysis
0
0
0
0
1
0
Epithelial necrosis
0
0
1
0
1
0
Submucosal necrosis
0
0
0
0
1
0
Squamous atrophy
0
0
0
0
1
3
Hyperplastic gastropathy
0
1
0
1
0
1
Hyperplastic gastritis,
acute/chronic
0
0
1
0
2
0
Hyperkeratosis
0
0
0
0
0
0
Epithelial ulceration
0
0
0
0
0
0
Females
No. of animals examined
5
5
5
5
5
5
Autolysis
0
0
0
0
0
0
Epithelial necrosis
0
0
0
0
0
0
Submucosal necrosis
0
0
0
0
0
0
Squamous atrophy
0
0
0
0
0
0
Hyperplastic gastropathy
0
0
0
2
0
1
Hyperplastic gastritis.
acute/chronic
0
0
0
1
3
0
Hyperkeratosis
0
0
0
0
0
2
Epithelial ulceration
0
0
0
0
3
0
eAnimals with more than one type of stomach lesion may have been counted more than once. Since individual
data were not reported, the reviewers were unable to determine which animals were counted more than once.
SOURCE: NIP (1987).
v’- e
-------
in females were increased (p <0.05) on both an absolute and relative basis.
Histopathology showed a moderate increase in protein resorption droplets
(hyaline droplets) in the proximal convoluted epithelium of the kidneys in
male rats in the 2,000-ppm group. No other evidence of kidney damage was
seen. Markedly and moderately increased protein resorption was also observed
in the 6,000- and 20,000-ppm groups. No protein resorption droplets were seen
in the kidneys of rats fed a control diet. No other treatment-related changes
were seen in males or females. Rats in the recovery group showed no adverse
effects following cessation of treatment. Because of the relationship between
the presence of alpha 2 globulin in male rats, and the development of kidney
lesions (Baetcke et al., 1991), the LOAEL is not based on male kidney effects.
Because this protein appears to occur only in the male rat, alpha 2 globulin
associated renal tubular cancers are not expected to be relevant to humans.
The LOAEL for this study is 6,000 ppm (535 mg/kg/day) based on increased
absolute and relative kidney weights in female rats. The NOAEL is 2,000 ppm
(178 mg/kg/day).
2. Longer-term ExDosure
a. 13-Week studies
A summary of longer-term studies for DMMP is presented in Table VI-4.
NTP (1987) conducted 13-week oral toxicity studies in male and female B6C3F 1
mice and F344/N rats. DMMP in corn oil was administered, by gavage, to the
animals 5 days/week for 13 weeks. All animals were observed daily, and body
weights and food consumption were recorded weekly. Necropsies were performed
on all animals, and histopathological examination of all major organs was
conducted on all animals that died, on vehicle controls, on high-dose group
rats, and on two high-dose group mice.
In the study with mice, groups of 10 males and 10 females received DMMP
at 0, 250, 500, 1,000, 2,000, 4,000, or 8,000 mg/kg/day. Only seven males and
six females were dosed at the 8,000-mg/kg level. Treatment-related deaths
occurred in nine males and nine females dosed at the 4,000-mg/kg level and in
seven males and five females dosed at the 8,000-mg/kg/day level. DMMP had no
effect on body weight, food consumption, clinical signs, gross pathology, or
histopathology. The stomach lesions observed in the 15-day study were not
vI-9
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Table VI-4 Summary of Studies: Longer-term Exposure of Animals to DMMP
Ciba-Geigy, 1978d
Hollinghaus. 1981
aunless otherwise stated.
b ( ) days dosed (total days).
Cooses were adiiinistered on days
a
Reference
Species
Dose
(mg/Kg/day)a
Route
Duration
(days)
NIP, 1987
Rat
0, 250. 500. 1.000
2,000, 4,000, 8,000
Oral
90
Rat
0, 250. 500. 1.000
2.000. 4.000. 8.000
Oral
90
Mouse
0, 250. 500, 1.000
2.000. 4.000. 8.000
Oral
90
Dunnick, 1984a
Rat
0, 250. 500. 1,000.
2,000
Oral
90
Chapin, 1984
Rat
0, 1,750
Oral
12 ( 14 )b
Hattie, 1987
Rat
127. 1269 mg/rn 3
Inhalation
90
Hardin, 1987
Mouse
4. 175
Oral
1 Generation
6-13 Gestation
Ciba-Geigy, 1978b
Rat
100. 1.000. 2.000
Oral
1 Generation
6—15 Gestation
Rat
2.000
Oral
1 Generation
6—15 Gestation
Rat
2,500
Oral
6-10 Gestation
Dunnick, 1984b
House
0, 250. 500. 1,000.
2.000
Oral
90 (105)
Dunnick, 1988,
NTP. 1987
Rat
0, 500. 1.000
Oral
103 Weeks
Mouse
Chicken
Chicken
0, 1,000, 2.000
1.999, 3.998
50
Oral
Oral
Intraperitoneal
103 Weeks
2 ( 42 )C
10
1 and 21 and chickens were observed through 42 days.
-------
seen in this study. Histopathology did not identify target tissues.
No compound-related cause for the high mortality at the two upper levels was
reported. Therefore, in the absence of any other data, a NOAEL or LOAEL
cannot be determined.
In the study with rats, groups of 10 males and 10 females received DMMP
at 0, 250, 500, 1,000, 2,000, 4,000, or 8,000 mg/kg/day. Treatment-related
mortality occurred in rats dosed at 2,000 mg/kg/day; deaths observed at lower
levels were due to technical error during the dosing regimen. The final body
weights of rats in the 4,000-mg/kg group were more than 10% lower than those
of the vehicle controls. Rats dosed at 8,000 mg/kg/day had rough hair coats,
and decreased activity was seen in rats dosed at both 4,000 and 8,000
rug/kg/day. Histopathology revealed lesions in the kidneys (nephrosis), testes
(atrophy and degeneration), and epididymis (degeneration) of treated males,
and atrophy of the salivary glands in males and females (Table VI-5) (NTP,
1987).
A second 13-week study was conducted with rats because of dosing errors
in the first study (NTP, 1987; discussed above). Groups of 10 males and 10
females were given, by gavage, DMMP in corn oil at 0, 250, 500, 1,000, 2,000,
or 4,000 mg/kg/day, 5 days/week for 13 weeks. Experimental design was
identical to the first study. All rats at the 4,000-mg/kg/day level died
during week 1, and six males and three females at the 2,000-mg/kg/day level
died during the study. The final body weights of rats dosed at the 2,000-
mg/kg/day level were 6% lower than those of the vehicle controls for males and
7% lower for females. The liver-to-body weight ratio was significantly
(p <0.01) increased in rats in this group. No clinical signs of toxicity were
observed. Histopathology revealed an increased incidence of kidney nephrosis
in treated males compared with vehicle control rats; however, the severity of
the lesions was similar between the treated and vehicle control rats. The
kidney lesions were not considered to be life threatening. Accumulation of
hyaline droplets was observed in the convoluted tubules of the renal cortex in
treated males at all dose levels. The minimal to mild hypospermatogenesis
seen in the testes of treated males was not dose-dependent (Table VI-6) (NTP,
1987). Because of an association with alpha 2 , globulin (Baetcke et al., 1991),
kidney lesions that occurred in males at all dose levels were not considered
for a LOAEL. The results of this study indicated a Frank-Effect-Level (FEL)
VI-”
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Table VI-5. Histopathological Changes in Rats After Oral
Administration of DMMP for 13 Weeks (Study 1)
Site/lesion
Vehicle
control
Dose
(malka]
250
500
1.000
2.000
4.000
8,000
Males
Kidney nephrosls
0/lOa
N ’
N
N
0/10
0/10
4/10’
Testes
Atrophy
0/10
1/10
2/10
2/10
3/9
10/10
2/9’
Degeneration
0/10
0/10
0/10
0/10
0/9
0/10
2/9c
Epididymis
Degeneration
0/10
0/10
0/10
0/10
0/10
9/10
3/9’
Salivary gland
Atrophy
0/10
N
N
N
0/10
0/10
6110’
Females
Salivary gland
Atrophy
0/10
N
N
0/2
0/10
0/10
4/10
• No. of rats with changes/No. of rats examined.
Not examined
Nine of 10 rats dead by week 2; 10th rat dead by week 5.
SOURCE: NIP (1987).
V1-12
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Table VI-6. Histopathological Changes in Rats After Oral
Administration of DMMP for 13 Weeks (Study 2)
Site/lesion
Vehicle
control
Dose ImQ/kQ)
250
500
1,000
2,000
4,000
Males
Kidney
Nephrosis
2/10
9110
10/10
10/10
5/9
0110°
Hyaline droplet
degeneration
0/10
8/10
10/10
10/10
4/9
3/10
Hemorrhage
0/10
0/10
0/10
0/10
1/9
2/10
Testes
Hypospermatogenesls
0/10
1/10
0/10
2/10
4/9
1/10
Giant cell
degeneration
0/10
0/10
0/10
1/10
0/9
0/10
Salivary gland
Acute nflanination
0/10
t(
H
0/10
0/10
2/10
Females
Salivary gland
Acute inflamatlon
0/10
N
N
N
1/10
1/10°
No. of rats with changes/No. of
100% mortality by week 1.
Not examined.
SOURCE: NIP (1987).
rats examined.
VI-13
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of 2000 mg/kg/day based on mortality and increased liver-to-body weight ratios
in both sexes. The NOAEL is 1000 mg/kg/day due to the absence of mortality
and liver changes.
Dunnick et al. (1984a) observed histopathological changes in the testes,
prostate glands, and kidneys of male Fischer-344 rats (20 rats/group)
administered oral doses of DMMP in corn oil at 0, 250, 500, 1,000, or 2,000
mg/kg/day, 5 days/week for 90 days. This study is discussed in detail in
section VI.B.3, Reproductive Effects. Rats in the high-dose group showed a
significant (p <0.01) decrease in total body weight gain (about 11%) relative
to the control. The kidney-to-body weight ratios were significantly (p <0.01)
increased in rats in the 1,000- and 2,000-mg/kg/day groups. The kidney
lesions observed at all dose levels included varying degrees of regeneration,
hyaline droplet degeneration, cytoplasmic hyaline bodies, and cellular
infiltrate, primarily lymphocytes, into the interstitium. Because of an
association with alpha globulin (Baetcke, 1991), male rat kidney lesions were
not appropriate for determining a LOAEL. The LOAEL in this study is based on
reproductive effects as discussed in section VI.B.3.
Dunnick et al. (1984b) studied the effect of DMMP on dominant lethal
mutations in male B6C3F 1 mice (discussed in section VI.B.6, Genotoxicity).
The mice were gavaged with DMMP in water at doses up to 2,000 mg/kg/day for
13 weeks. At the conclusion of the study, there was no mortality, nor any
chemically related effects on body weight or relative weights for the testis,
epidydimis, prostate, and kidney. Histological examination of selected
organs, sperm concentration and morphology, and levels of plasma
cholinesterase, follicle stimulating hormone (FSH), and luteinizing hormone
(LH) did not demonstrate DMMP related effects.
In an inhalation study (discussed in section VI.B.3, Reproductive
Effects), male Fischer-344 rats exposed continuously to DMMP vapors at 25 or
250 ppm for 90 days showed gross and histopathological testicular changes
(Mattie et al., 1987).
b. Lifetime studies
DMMP in corn oil was administered by gavage at doses of 0, 1,000, or
2,000 mg/kg to groups of 50 male and 50 female B6C3F 1 mice and at doses of 0,
VI-14
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500, or 1,000 mg/kg to groups of 50 male and 50 female F334/N rats, 5
days/week for 103 weeks. All animals were observed twice daily, clinical
signs were recorded weekly, and body weights were measured once each week
during the first 13 weeks and once each month thereafter. Necropsy and
histopathological examinations were performed on all animals (NTP, 1987;
Dunnick et al., 1988).
In mice, the decrease in survival of the high-dose (2,000 mg/kg) group
was partially attributed to fighting among males. There was an apparent
overdose in both sexes on week 45 (dose mixture had a concentration 134%
greater than the targeted amount) which caused the deaths of 17 and 22
high-dose males and females, respectively. However, when these deaths were
censored from the analysis, survival of the treated groups was reduced in both
sexes. At termination, 29/50 vehicle control males, 12/50 low-dose males, and
0/50 high-dose males were alive; 41/50, 30/50, and 2/50 females survived.
Mean body weights of males in the high-dose group were 7-16% 1ower than those
of the vehicle controls between study weeks 36 and 76; the females at this
dose level showed 6-12% lower body weights between study weeks 88 and 103. No
treatment-related clinical signs were observed. Histopathology revealed
congestion of the lungs in the mice that died at weeks 45 and 75 but not in
those surviving to the end of the studies. The lung congestion was associated
with early deaths, dosing errors, and gavage accidents. The incidence of
hepatocytomegaly was increased in treated males (17/50, low-dose group; 10/46,
high-dose group) compared with vehicle control males (5/50). No increases in
nonneoplastic liver lesions were seen in female mice (NIP, 1987; Dunnick et
al. 1988).
In rats, survival was lower for males at both dose groups; final
survival was 27/50, vehicle control; 17/50, low-dose group; and 4/50, high-
dose group. The decrease in survival was partially due to treatment-induced
renal toxicity. Survival of the low-dose females was comparable to that of
the vehicle controls. However, the final survival of the high-dose females
(23/50) was significantly (p <0.05) lower than that of the vehicle controls
(30/50). At the 1,000-mg/kg/day level, the mean body weights of males were
5-10% lower than those of the vehicle controls between weeks 28 and 76, and
the mean body weights were 10-24% lower between weeks 80 and 104; females
showed an 8-12% decrease after week 80. Mean body weights of both sexes of
rats at the 500-mg/kg/day dose level were comparable with those of the vehicle
VI-15
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controls. Treatment-related nonneoplastic lesions observed in the kidneys of
male rats are sumarized in Table VI-7. Females showed no treatment-related
nonneoplastic lesions (NTP, 1987; Dunnick et al., 1988).
In summary, the study with mice was considered to be inadequate owing to
poor survival in males at both levels and in females at the high dose.
Therefore, it is difficult to estimate a LOAEL or a NOAEL. In rats, DMMP
induced mortality, body weight loss, and kidney lesions in males at both dose
levels. Male kidney lesions are not considered to be relevant to humans
because of the association with alpha 2 g1obu1in (Baetcke et al., 1991) and
were not considered as adequate endpoints for a LOAEL. Females at the high
dose showed decreases in survival and mean body weights toward the end of the
study. The LOAEL is 1,000 mg/kg/day based on significant body weight
decreases in males and females; the NOAEL is 500 mg/kg/day.
3. Reoroductive Effects
Dunnick et al. (1984a) assessed the reproductive toxicity of DMMP in
groups of 20 male Fischer-344 rats following oral (gavage) administration of
DMMP in corn oil at doses of 0, 250, 500, 1,000, or 2,000 mg/kg, 5 days/week
for a total of 63 doses during a 90-day period. All female rats were
sacrificed on day 100; their uteri were removed and examined for the number of
live and dead pups and the number of resorptions. At day 84, each treated
male was housed with two untreated female Fischer-344 (i.e., 40/group) rats
for five days. The males were sacrificed on day 90, and the reproductive and
genito-urinary systems underwent histopathological examination. Sperm samples
were analyzed at sacrifice for sperm count, sperm motility, and sperm
morphology. DMMP had no effect on survival, and no clinical signs or
neurotoxicity were observed. Rats dosed at 2,000 mg/kg showed significantly
(p <0.01) decreased total body weight gain relative to the control group.
A significant (p <0.01) increase was observed in the kidney-to-body weight
ratio in the two highest dose groups, and there was a decrease in the
epididymis/body weight ratio in the high-dose group. No alterations were seen
in the plasma levels of luteinizing hormone or follicle-stimulating hormone at
any dose. Testicular lesions observed in 18 of 20 rats (90%) in the high-dose
group were characterized by lack of spermatogenesis and by degeneration,
vacuolization, and necrosis. Changes observed in the prostate of one rat
dosed at 1,000 mg/kg/day and four rats dosed at 2,000 mg/kg/day included
VI-16
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Table VI-7. Incidences of Kidney Lesions Observed in Male
F344N Rats After Oral Administration of DMMP
for 103 Weeks
Lesion
Dose level (mg/kg)
0
500
1,000
Nephropathy
36/50a ( 72 )b
43/50 (86)
40/49 (82)
Severity of nephropathyc
1.9
2.5
2.8
Calcification of renal
papilla
12/50 (24)
41/50 (82)
36/49 (73)
Cortical tubular cell
hyperplasia
0/50 (0)
8/50 (16)
9/49 (18)
Pelvic epithelial
hyperplasia
0/50 (0)
23/50 (46)
21/49 (43)
a No. of rats with lesions/No, of rats examined.
b The numbers in parentheses are percentages.
C Mean severity of lesions graded from 1 to 4, minimal to marked.
SOURCE: NTP (1987); Dunnick et al. (1988).
VI-17
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multifocal infiltration of lymphocytes and plasma cells into the interstitium,
and dilation of acini containing cellular debris.
DMMP was shown to be toxic to the male reproductive system. DMMP
induced dose-dependent decreases in sperm motility and sperm counts; the
decrease reached statistical significance (p <0.01) at the high-dose level.
Sperm head abnormalities characterized by headless sperm and sperm heads
without a hook or with a blunt hook were significantly (p <0.01) increased at
the high-dose level (Table VI-8). DMMP altered reproductive functions at all
dose levels, as shown In Table VI-9. Fertility was completely arrested at the
high-dose level; rats failed to impregnate females at this level. A
significant (p <0.01), dose-dependent decrease was observed in the number of
live fetuses per litter at doses 500 mg/kg. Treatment also caused
significant (p <0.05) dose-dependent increases in the percentage of
resorptions. DMMP was shown to be a reproductive toxin. The LOAEL for
reproductive effects was the lowest dose tested, 250 mg/kg/day (179 mg/kg/day
when adjusted from a 5-day to a 7-day exposure) (Dunnick et al., 1984a).
Chapin et al. (1984) examined DMMP-induced development of reproductive
lesions by light and electron microscopy. Groups of 49 male Fischer-344 rats
were orally administered, by gavage, DMMP dissolved in tapwater at
1,750 mg/kg, 5 days/week for up to 12 weeks; a group of fourteen control rats
received tapwater only. After 3, 4, 5, 7, 9, and 12 weeks of treatment,
groups of seven treated and two control rats were sacrificed, and the testes
and epididymis were examined. The remaining animals (seven treated and two
controls) were allowed to recover for 14 weeks on a control diet, and the
tissues were processed as above. Body weights of treated rats were lower than
those of the vehicle control rats after week 5 of the treatment period. DMMP
did not reduce testes weights but did impair epididymal weight gain. Changes
in the testes and epididymis were first observed 5 weeks posttreatment. The
approximate severity and the time course of the lesions seen in these tissues
are presented in Table VI-lO. DMMP also induced morphological alterations in
Sertoli cells and elongating spermatids, as well as functional defects in
spermatozoa. Animals left to recover for 14 weeks showed approximately 80%
normal tubules; affected tubules varied in their degree of recovery, but all
showed loss of normal epithelial organization, a characteristic of DMMP
treatments.
VI-18
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Table VI-8. Analysis of Sperm From Male Fischer-344 Rats
After Oral Administration of DMMP for 90 Days
Sperm count x 106
Dosea
% Motile spermb
(mean ± SE per g
caudal epididymal
Sperm-head
abnormalities
(mg/kg)
(mean ± SEM)
tissue)
(mean ± SEM)
0
80.2 ± 2.7
541.4 ± 25.1
4.5 ± 0.3
250
80.5 ± 3.0
515.2 ± 38.9
5.6 ± 0.7
500
79.7 ± 3.6
459.2 ± 35.2
5.9 ± 0.5
1000
71.5 ± 3.1*
432.2 ± 38.5
6.9 ± 0.7
2000
35.8 ± 5•5**
219.6 ± 34•Q**
41.7 ± 5.1**
alwenty rats per group.
bpercent of sperm with any movement.
*Signifjcantly different from control value (p <0.05).
**s.jgnjf.jcantly different from control value (p <0.01).
SOURCE: Dunnick et al. (1984a).
VI-19
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Table VI-9. Changes in the Reproductive Function of Male
Fischer-344 Rats After Oral Administration
of DMMP for 90 Days
% of
males
No. of males
with
impregnatIng 0,
Total No.
No. of
live
sperm-
Male
1. or 2 females
(%) of
fetuses
per
Dose
(mg/kg)
positiv
females
ferti ity
index CX)
0 1 2
pregnant
females
litter
± SEM)
(mean d
% Resorptions
0 75 (15/20) 70 (14/20) 6 8 6 20 (50) 7.6 ± 0.7 6.1 (10/163)
250 85 (17/20) 75 (15/20) 5 11 4 19 (47.5) 7.8 ± 0.4 14.9 (26/174)*
500 60 (12/20) 60 (12/20) 8 7 5 17 (42.5) 5.7 ± 0.6** 394 ( 53 ( 15 Q)e.
1000 50 (10/20) 40 (8/20) 12 5 3 11 (27.5) 0.82 ± 0.5** 79 1 (34/43)**
2000 55 (11/20) 0** 20 0 0 0 (0.0)** 0.0 ± 0.0 -—
[ (No. of males with 1 or 2 sperm-posItive females)/(N=20)] x 100.
[ (No. of males with 1 or 2 pregnant females)/(N=20)] x 100. This value also Included pregnant females
that did not have sperm—positive smears.
Total of 40 females were exposed to 20 males (2 females per male) for each group.
[ (No. of resorptions)/(total fetuses + total no. of resorptions)] x 100; statistical analysis based on
e resorptions per litter.
Includes 4 dead fetuses from 2 lItters.
* Significantly different from control value (p <0.05).
** Significantly different from control value (p <0.01).
SOURCE: Dunnick et al. (1984a).
VI-20
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Table VI-lO. Severity and Time Course of Lesions Observed in
the Testes and Epididymis of Male Fischer-344
Rats After Oral Administration of DMMP for up
to 12 Weeks
Effects
Weeks after treatment
5
7
9
12
Testes
Foc l exfoliation
PAS -positive round bodies
+a
+
+
+
+ +b
+ +
+ +
+ +
Epididymi s
Regions 1-3
PAS -positive round bodies
Luminal spermatocytes
Decreased sperm density
Regions 5-6
Luminal spermatocytes
+
+
+
+ +
+ +
+
+ +
+ +
+
+ +
+
+
+
+ +
+
+ +
Number of affected animals
5/7
7/7
7/7
7/7
aM lid.
bModerate
cSevere
dperiodic acid and
Schiff’s Stain
SOURCE: Chapin et al. (1984).
VI-21
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Mattie et al. (1987) exposed male Fischer-344 rats (number per group not
reported) to DMMP vapors at concentrations of 25 or 250 ppm (127 and 1269
mg/rn 3 , respectively) continuously for 90 days. Light microscopy showed
segmental to diffuse degeneration of the seminiferous epithelium; the
degeneration observed also was seen in rats sacrificed 1 year later.
Ultrastructurally, the testes of rats exposed to 250 ppm DMMP vapors showed an
increased number of lipid droplets in cells lining the seminiferous tubules,
increased numbers of lysosomes in Sertoli cells, dilation of mitochondria,
presence of multinucleate giant cells, and a decreased number of spermatogenic
cells.
4. Develoømental Toxicity
In a short-term screening assay, 50 female CD-i mice were given, by
gavage, DMMP in corn oil at doses of 4,175 mg/kg/day on gestation days 6-13.
The control group received corn oil only. Dams were allowed to litter. DMMP
had no effect on the dams, did not reduce the number of live pups per litter,
and did not affect pup survival or fetal body weight gain. However, pup birth
weight was significantly (p <0.05) lower in the treated (1.5±0.1 g) group when
compared with the vehicle control (1.6±0.2 g) (Hardin et al., 1987).
Ciba-Geigy (1978b) evaluated the teratogenic potential of DMMP in female
Sprague-Dawley rats following oral (gavage) administration. Groups of 25 rats
were dosed with DMMP in 2% carboxymethylcellulose (CMC) at 100, 1,000, or
2,000 mg/kg/day on gestation days 6-15; dams were sacrificed on day 21.
Maternal toxicity observed at the 2,000-mg/kg/day dose included decreases in
body weight gain and food consumption. Dams at the 1,000-mg/kg/day level
showed slightly decreased feed intake. No maternal toxicity was observed at
the 100-mg/kg/day level. No embryotoxicity or fetotoxicity was seen at the
low dose. Fetal toxicity seen at the higher levels included reduced fetal
weight and delayed skeletal maturation (ossification) and were considered
attributable to the maternal toxicity seen at these levels. DMMP did not
alter the incidence of fetal anomalies.
In another experiment (Ciba-Geigy, 1978b), groups of 25 female Sprague-
Dawley rats received oral intubation of DMMP in 2% CMC at 2,000 mg/kg/day on
gestation days 6-15 and at 2,500 mg/kg/day on gestation days 6-10. Food
VI-22
-------
consumption was decreased at both levels, and maternal body weight was
decreased at the 2,500-mg/kg/day level. Fetal body weight was slightly
reduced and ossification was increased in both dose groups. No gross
malformations and no visceral or skeletal anomalies were detected in the
2,000-mg/kg/day group. The few anomalies in the fetuses from the higher level
were considered to be within the normal range of this strain of rats.
5. Carcinoaenicitv
DMMP was carcinogenic to male F344/N rats, inducing transitional cell
papillomas or carcinomas (combined) of the pelvic epithelium in the kidneys.
In addition, DMMP increased the incidence of mononuclear cell leukemia in male
rats. Male rats also developed renal tubular cell adenocarcinomas; however,
this effect is considered to be associated with alpha 2 globulin and not
relevant to humans (Baetcke et a]., 1991). DMMP was not carcinogenic to male
and female B6C3F 1 mice, but the study was considered to be inadequate owing to
decreased survival in both sexes (NIP, 1987).
In the NTP (1987) study (reviewed in detail in Section VI.B.2.b,
Lifetime Studies), DMMP in corn oil was administered, by gavage, to B6C3F 1
mice at doses of 0, 1,000, or 2,000 mg/kg/day and to F344/N rats at doses of
0, 500, or 1,000 mg/kg/day in groups of 50 animals/sex/species, 5 days/week
for 103 weeks. No treatment-related neoplastic lesions were observed in male
or female mice. However, owing to poor survival, NIP considered the study to
be inadequate to assess the carcinogenic potential of DMMP.
DMMP was not found to be carcinogenic following oral (gavage)
administration to female F344/N rats. DMMP exhibited some evidence of
carcinogenicity in male F344/N rats as shown by increased incidence of tubular
cell hyperplasia, renal tubular cell adenocarcinomas, hyperplasia of the
transitional cell epithelium, and transitional cell papillomas or carcinomas
(combined) of the pelvic epithelium in the kidneys (Table VI-il). These
tumors are rarely seen in this strain of rat and, therefore, are believed to
be treatment related. The historical incidence of tubular cell adenomas or
adenocarcinomas in NIP studies was 8/1,448 (0.6%), and the incidence of
transitional cell papillomas was 1/1,448 (<0.01%). This is supported by the
finding that the incidence of cortical tubular cell hyperplasia often
VI-23
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Table VI-il. Incidences of Preneoplastic and Neoplastic Lesions
Observed in the Kidneys of Male F344/N Rats After
Oral Administration of DMMP for 103 Weeks
Type
Dose level (mg/kg/day)
0
500
1,000
Cortical tubular cell
hyperplasia
0/50(0)
8/50(16)
9/49(18)
Pelvic epithelial
hyperplasia
0/50(0)
23/50(46)
21/49(43)
Tubular cell adenocarcinoma
0 / 50 a( 0 )b
2/50(4)
3/49(6)*
Transitional cell papilloma
0/50(0)
7/50(14)**
3/49(6)*
Transitional cell carcinoma
0/50(0)
1/50(2)
0/49(0)
Transitional cell papilloma
or carcinoma
0/50(0)
8/50(16)**
3/49(6)*
aNo with tumors/No. examined.
blhe numbers in parentheses are percentages.
*Signjfjcantly different from control value (p <0.05).
**Signifjcantly different from control value (p <0.001).
SOURCE: NTP (1987); Dunnick et al. (1988).
VI-24
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increases in association with the induction of tubular cell neoplasm,
suggesting morphological progression from hyperplasia to adenomas to
adenocarcinomas. Similarly, there is a morphologic spectrum from hyperplasia
of the transitional epithellum to paplllonia and carcinoma of the renal pelvis.
No tubular cell or transitional cell neoplasms or other treatment-related
neoplasms were seen in female rats. The incidence of mononuclear cell
leukemia was significantly increased (p <0.001) in high-dose male rats
(vehicle control, 10/50; low dose, 11/50; high dose, 17/50), and the incidence
exceeded the highest incidence seen in historical vehicle control groups
(14/50) in the NIP studies (Table VI-12) (NIP, 1987).
The profile of some kidney effects observed in the DMMP-treated male
rats is consistent with that attributed to alpha 2 globulin (Baetcke et al.,
1991; NIP, 1987). This protein is synthesized in the liver of the male rat
and has not been detected in female rats. It has not been detected in any
other species, including humans. Because this protein appears to occur only
in the male rat, alpha 2 globulin associated renal tubular cancers are not to
be expected to occur in other species. Thus, such effects are not considered
to be relevant to humans.
In summary, DMMP was carcinogenic to male rats but not to female rats.
Based on the EPA Guidelines for Carcinogenic Risk Assessment, DMMP is
classified in Group C: Possible Human Carcinogen.
6. Genotoxicitv
Table VI-13 summarizes the results of the genetic toxicology assays with
OMMP. DMMP was nonmutagenic in the Ames assay using several Salmonella
tvDhimurium strains both in the presence and absence of metabolic activation
(Ciba-Geigy, 1976h, 1978c; Sivak, 1983; Mortelmans et al., 1986).
DMMP induced forward mutations in a mouse lymphoma 15178Y/TK+/- assay in
the absence of metabolic activation (NTP, 1987). DMMP did not induce
mutations in the Chinese hamster ovary (CHO) cell HGPRT assay in the absence
of activation (Sivak, 1983). lice (1990) reported that DMMP induced forward
mutations in this same assay in both the presence and absence of metabolic
activation.
VI -25
-------
Table VI-12. Incidence of Mononuclear Cell Leukemia Observed
in Male F344/N Rats After Oral Administration
of DMMP for 103 Weeks
Site
Dose
level (mci/kg/day)
0
500
1,000
Multiple
organs
10 / 5 0 a( 20 )b
11/50
(22)
7/50
(34)C
Spleen
0/50 (0)
1/50
(2)
0/50
(0)
Total
10/50 (20)
12/50
(24)
17/50
(34)C
aNo with tumors/No. examined.
blhe numbers in parentheses are percentages.
Csignificantly different from control value (p <0.001)
V1-26
-------
Table VI-13. Mutagenicity of DMMP in Various Test Systems
Dose
or
Endpoint response
Assay Test System concentration range
(with S9/without S9) Reference
1. Gene mutation
Ames assay Salmonella typhimurium 10 pg to 10 mg/plate -I- Ciba-Geigy (1976h)
TA1535, TA1538
. typhimurium 25 to 2.025 pg/0.l ml -I - Ciba—Geigy (1978c)
TA98, TA100, TAIS3S. TA1537
. typhimurium 0.16 to 200 p1/plate -I - Sivak (1983)
TA98, TA100, TAIS3S, TA1537,
TA 1538
S tvphimurium 0 to 10.000 pg/plate -I - Mortelmans et al. (1986)
TA98, TA19Q. 1A1535. TA1537
Mouse lyniphoma assay 15178Y/TK cells 0.25 to 5 p1/mI b ,÷ NIP (1987)
25 to 45 p1/m I +1 + lice (1990)
CHO/RGPRT assay Chinese hamster ovary (CR0) cells 125 to 1.000 pg/mt b , Sivak (1983)
1 ) 2. Chromosomal aberration CR0 cells 2,000 to 5.000 pg/niL -I - NIP (1987)
14.300 to 22.000 pg/mL -I - NIP (1987)
CR0 cells 125 to 1.000 pg/mt b , Sivak (1983)
3 Sister chromat d exchange CR0 cells 125 to 1.000 pg/mI b/_ S lvak (1983)
CR0 cells 160 to 5,000 pg/mt -/+ NIP (1987)
1,100 to 22.000 pg/mI +/ 4 . NIP (1987)
4. Sex-linked recessive Drosophila melanopaster 23,135 ppm (SLRI) NIP (1987)
lethal (SIRL)
mutation and recIprocal 23.500 ppm (RI) e NIP (1987)
translocation (RI)
5. In vitro neoplastic BALB/c 313 cells 0.8 to 100 pg/mL Sivak (1983)
transformation
aNetabolic activation not applicable
bEither not tested with S9 metabolic activation, or activation not applicable for test.
-------
Limited evidence of clastogenicity was seen in CHO cells; DMMP induced
chromosomal aberrations at the highest concentration tested (1 mg/mL) without
activation (Sivak, 1983), but did not induce aberrations when tested by NTP at
concentrations up to 22 mg/mL either with or without activation (NIP, 1987).
Conflicting results were obtained in assays inducing sister chromatid
exchanges (SCEs) in CHO cells. Sivak (1983) observed no significant increases
in SCEs at doses up to 1 mg/mL. On the other hand, NIP (1987) reported
positive results both in the absence (over a concentration range of 0.16-11
mg/mL) and presence (1.1-22 mg/mL) of metabolic activation.
In an J.n vitro cell transformation assay, DMMP did not induce neoplastic
transformations in BALB/c 3T3 cells (Sivak, 1983).
In fl vivo genotoxic studies, when DMMP was fed to Drosoohila it induced
significant increases in the frequency of sex-linked recessive lethal
mutations but did not induce reciprocal translocations (NIP, 1987).
DMMP was shown to induce dominant lethal mutations in male B6C3F 1 mice
when orally administered at 0, 250, 500, 1,000, or 2,000 mg/kg/day, 5
days/week for 13 weeks. The chemical was administered in water by gavage to
treatment groups consisting of 40, 20, 20, 40, and 40 animals, respectively.
After 4, 8, and 12 weeks of treatment, mice were mated with untreated CD-i
mice. Half the males dosed at 0, 1,000, or 2,000 mg/kg were mated after a
15-week recovery period on a control diet. DMMP at the two highest dose
levels (1,000 or 2,000 mg/kg) caused dominant lethal mutations (early
resorptions). The dominant lethal index was significantly (p <0.001)
increased in the 4, 8, and 12 week mating trials 1, 2, and 3 (40, 37, and 44%,
respectively) at the 2,000-mg/kg/day level; and in the 4 and 12 week mating
trials 1 and 3 (12 and 13%, respectively) at the 1,000-mg/kg/day level.
Groups of mice mated after a 15-week recovery period had a resorption rate
comparable to that of the vehicle control group (Ounnick et al., 1984b).
7. Neurotoxicity
Groups of 20 White leghorn hens were administered, by gavage, 1,999 (1/2
L0 50 ) or 3,998 mg DMMP/kg (LD 50 ) as a 60% dilution in 2% CMC twice, initially
VI-28
-------
and after 21 days. The animals were observed throughout a 42 day period.
Acute toxicity observed Included ataxia, curved position, and fluttered
feathers in birds at the low dose, and ataxia, apathy or sedation, curved
position, and fluttered feathers in birds at the high dose. The surviving
birds partially recovered from the symptoms. Histopathology of the spinal
cord and peripheral nerve of dosed hens showed no evidence of delayed
neurotoxicity. It was concluded that DMMP did not cause delayed neurotoxicity
(Ciba-Geigy, 1978d).
Hollinghaus et al. (1981) observed no delayed neurotoxicity in groups of
three adult White leghorn hens following daily intraperitoneal injection of
DMMP in corn oil at doses of 50 mg/kg for 10 days.
In a 3-day oral intubation study with rats, DMMP decreased plasma
cholinesterase levels (30% in males and 40-50% in females) at a dose of 1,000
mg/kg/day over a 4-hour period when compared with control values taken during
the same time period; no decreases in plasma cholinesterase levels were seen
in rats dosed at 1, 10, or 100 mg/kg/day (Ciba-Geigy, 1978a). Mice dosed for
90 days at 250, 500, 1,000 or 2,000 mg/kg/day also did not have increased
plasma cholinesterase levels (Dunnick et al., 1984b) (See detailed discussion
of rat intubation study on page VI-5 and mouse study on page VI-28).
VI-29
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VII. HEALTH ADVISORY DEVELOPMENT
A. SUMMARY OF HEALTH EFFECTS DATA
Data on the systemic toxicity of DMMP in humans were not found in the
available literature; patch testing with aqueous solutions of DMMP produced
mild to moderate skin irritation in human subjects. DMMP was not a skin
sensitizer (Ciba-Geigy, 1976a).
Acute toxicity studies indicate oral LD 50 values of >6,810 mg/kg in both
mice and rats (NIP, 1987). Ciba-Geigy (1976b) reported an oral LD 50 of 10,190
mg/kg in rats. Animals exhibited ataxia, ventricumbency, unsteady gait,
muscular hypertonia and hypotonia, tremors, prostration, and reduction in
spontaneous motility. DMMP was slightly toxic by the intravenous route; the
LD 50 was 912 mg/kg in mice and 1,050 mg/kg in rats (Ciba-Geigy, 1977a). The
acute dermal LD 50 of DMMP was reported to be >4,600 mg/kg in rats (Ciba-Geigy,
1976c) and >2,000 mg/kg in rabbits (Stauffer, 1983). DMMP (0.5 mL) elicited
mild skin irritation in rabbits (Ciba-Geigy, 1976d) and produced mild ocular
irritation when instilled (0.1 g) into the eyes of rabbits (Ciba-Geigy,
1976f). DMMP was negative as a sensitizer in guinea pigs (Ciba-Geigy, 1976g).
In a 3-day oral intubation study with rats, DMMP decreased plasma
cholinesterase levels (30% in males and 40-50% in females) at a dose of 1,000
mg/kg/day over a 4-hour period when compared with control values taken during
the same time period; no decreases in plasma cholinesterase levels were seen
in rats dosed at 1, 10, or 100 mg/kg/day (Ciba-Geigy, 1978a). Mice dosed for
90 days at 250, 500, 1,000 or 3,000 mg/kg/day also did not have increased
plasma cholinesterase levels (Dunnick et al., 1984b).
In a 15-day study with mice, histopathological changes were observed in
the stomachs of males receiving 1,250 mg/kg/day and in females receiving
5,000 mg/kg/day; no stomach lesions were seen in females dosed at 2,500
mg/kg/day (NIP, 1987).
In a 15-day study with rats, no gross pathological changes were observed
at levels up to 15,000 mg DMMP/kg/day; however, mortality was seen in both
VII-1
-------
sexes dosed at . 5,O0O mg/kg/day. No histopathological examination was
conducted (NIP, 1987).
The profile of some kidney effects observed in the DMMP-treated male
rats is consistent with that of alpha 2 globulin nephrotoxicity (Baetcke,
1991). This protein is synthesized in the liver of the male rat and has not
been detected in female rats. It has not been detected in any other species,
including humans. Because this protein appears to occur only in the male rat,
alpha 2 globulin nephrotoxicity, and subsequent effects, are not expected to
occur in other species. Thus, some DMMP-induced renal noncarcinogenic and
carcinogenic effects were not considered to be relevant to humans.
Subsequently, such endpoints are not used to develop advisory values to
protect human health.
In a 4-week dietary study with rats, DMMP caused an increase in the
protein resorption droplets (hyaline droplets) in the proximal convoluted
epithelium of the kidneys of males fed diets containing 2,000, 6,000, or
20,000 ppm (178, 535, or 1,790 mg/kg/day); the effect was more pronounced with
increasing levels of DMMP. No kidney changes were seen in females (Ciba-
Geigy, 1977c).
In a 13-week study with male and female mice, oral administration of
OMMP in corn oil at levels between 250 and 8,000 mg/kg/day produced no adverse
effects on body weight gain, clinical signs, food consumption, or gross or
histopathology. Mortality was seen in both sexes at the higher (4,000 or
8,000 mg/kg) dose levels (NIP, 1987).
In a 13-week study with rats, oral administration of DMMP in corn oil at
2,000 mg/kg/day caused decreased survival and body weight gain and increased
liver-to-body weight ratio in males and females. Histopathology revealed
kidney changes in males at all dose levels starting at 250 mg/kg/day; no
kidney changes were seen in females at levels up to 2,000 mg/kg (NIP, 1987).
In a chronic study, male and female B6C3F 1 mice received oral intubation
of 1,000 or 2,000 mg DMMP/kg, 5 days/week for 103 weeks. Mean body weights
were decreased in both sexes in the high-dose group, and the incidence of
hepatocytomegaly was increased in males. Females showed no treatment-related
VII-2
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nonneoplastic lesions. However, this study was considered to be inadequate
owing to decreased survival In both sexes, which was attributed to fighting
among males and dosing errors in females (NTP, 1987).
Oral administration of DMMP at 500 or 1,000 mg/kg, 5/days/week for 103
weeks, to male and female F344/N rats caused an increase in kidney lesions in
males at both levels. No kidney lesions were seen in females at either level.
Both males and females at the high dose showed lower survival and decreased
body weight gain (NIP, 1987).
DMMP was not carcinogenic in female F344/N rats or male or female B6C3F 1
mice. However, the study with mice was judged to be inadequate to evaluate
the carcinogenic potential of DMMP owing to poor survival in both sexes (NIP,
1987).
DMMP was carcinogenic in male F344/N rats as shown by increased
incidences of mononuclear cell leukemia, hyperplasia of the transitional
epithelium, and transitional cell papilloma or carcinoma (combined) of the
kidneys. The males also developed renal tubular cell hyperplasia and
adenocarcinoma which is considered to be in response to the presence of
alpha 21 globulin, a protein found only in male rats (Baetcke, 1991). DMMP is
classified in Group C; Possible Human Carcinogen.
OMMP was nonmutagenic in bacteria (Ciba-Geigy, 1976h, 1978c; Sivak,
1983; Mortelmans et al., 1983). It induced forward mutations in mouse
lymphoma cells (NTP, 1987) but did not induce mutations in CHO cells in the
CHO/HGPRT assay (Sivak, 1983). DMMP showed limited evidence for
clastogenicity in CHO cells. In one study, it induced chromosomal aberrations
at a concentration of 1 mg/mL (Sivak, 1983), but it did not do so at
concentrations up to 22 mg/mL when tested by NIP (1987). Conflicting results
were obtained in the sister chromatid exchange assays; Sivak (1983) observed
no increases in SCEs, whereas NIP (1987) reported positive results. DMMP did
not induce neoplastic transformations in the BALB/c 3T3 cell assay (Sivak,
1983). vivo , DMMP increased the frequency of sex-linked recessive lethal
mutations but did not induce reciprocal translocations in Drosophila (NTP,
1987). DMMP gave positive results in the dominant-lethal assays in mice and
rats (Dunnick et al., 1984a,b).
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DMMP was shown to be a reproductive toxin following oral administration
to male rats. It caused decreases in sperm count, sperm motility, and male
fertility index, and also induced histopathological changes in the testes,
epididymis, and prostate glands. DMMP altered reproductive functions in male
Fischer-344 rats at all levels (250 to 2,000 mg/kg, 5 days/week for 13 weeks)
(Dunnick et al., 1984a). Inhalation exposure of rats to DMMP vapors (25 or
250 ppm) induced lesions in the testes and epididymis (Mattie et al., 1987).
DMMP was not found to be teratogenic; no developmental effects were
observed following oral administration of 4,175 mg/kg/day during gestation
days 6-13 (Hardin et al., 1984). DMMP at maternally toxic doses (1,000 or
2,000 mg/kg/day on gestation days 6-15) induced fetal toxicity that included
reduced fetal weight and delayed skeletal maturation; no fetal anomalies were
seen. In another study, DMMP at 2,000 or 2,500 mg/kg/day, administered on
gestation days 6-13, reduced fetal weight but did not induce gross
malformations or visceral or skeletal anomalies (Ciba-Geigy, 1978b).
DMMP did not induce delayed neurotoxicity in White leghorn hens
following oral administration at 1,999 or 3,998 mg/kg (Ciba-Geigy, 1978d) or
intraperitoneal injection at 50 mg/kg/day for 10 days (Hollinghaus et a].,
1981).
B. QUANTIFICATION OF TOXICOLOGICAL EFFECTS
Health Advisories are generally determined for One-day, Ten-day, longer-
term (approximately 7 years), and Lifetime exposures if adequate data are
available that identify a sensitive noncarcinogenic endpoint of toxicity. The
HAs for noncarcinogenic toxicants are derived using the following formula:
HA — ( NOAEL or LOAEL) (bw ) = _____ mg/L (____ j. g/L)
— (UF) (____ 1/day)
where:
NOAEL or LOAEL = No- or Lowest-Observed-Adverse-Effect Level (in mg/kg
bw/day).
bw = assumed body weight of a child (10 kg) or adult (70
kg).
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UF = uncertainty factor (10, 100, or 1,000), in accordance
with NAS/EPA guidelines.
L/day - assumed daily water consumption of a child (1 L/day) or
adult (2 L/day).
1. One-day Health Advisory
The 3-day gavage study in rats (Ciba-Geigy, 1978a) was considered for
derivation of a One-day HA. Plasma cholinesterase levels in Sprague-Dawley
rats, 5/sex/dose, were measured at pretest, and 0.5, 1, 2, and 4 hours after
the third administration of DMMP in tapwater at doses of 1, 10, 100, or 1,000
mg/kg/day. Plasma cholinesterase levels were depressed at the 1,000-mg/kg/day
level only. In males, there was an approximate reduction of 30% over the 4-
hour period when compared with vehicle control values taken at the same time
period, and in females there was a 40-50% reduction. No effect on plasma
cholinesterase levels was observed in the other groups. Based on the
decreases in plasma cholinesterase levels in both sexes at the high dose, the
NOAEL was 100 mg/kg/day. Since only plasma cholinesterase (butyl
cholinesterase) but not brain or erythrocyte cholinesterase (acetyl
cholinesterase) was measured, data gaps exist for acetylcholinesterase
inhibition. The study is limited further by the small number of animals used
per sex and treatment group, and the lack of a dose-response curve.
Therefore, the Ciba-Geigy (1978a) study is limited in its use to derive a
One-day HA. However, cholinesterase depression was considered in the
assessment of effects from a one-day exposure to DMMP; the recommended One-day
HA is protective of cholinesterase effects.
Since these data are judged unsuitable for derivation of a One-day HA,
it is recommended that the Longer-term HA for a 10-kg child (2 nig/L) be used
as a conservative estimate for the One-day HA value.
2. Ten-day Health Advisory
The 15-day gavage study with mice (NTP, 1987) was considered and
rejected for the derivation of a Ten-day HA. This study was conducted on a
limited number of animals (five/sex/dose), and histopathology revealed lesions
(gastropathy, gastritis, squamous atrophy, hyperkeratosis, or epithelial
VII -5
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ulcerations) in the stomach (foreor glandular not specified) of both male and
female mice; the males were more sensitive than the females. Based on stomach
lesions, the LOAEL was 1,250 mg/kg/day for males and 5,000 mg/kg/day for
females. However, stomach lesions seen in this study were not observed in
mice following oral administration of DMMP at comparable dose levels for 13
weeks (doses: 250 - 8,000 mg/kg/day) or 103 weeks (doses: 1,000 and 2,000
mg/kg/day). Therefore, it is difficult to attribute these effects to DMMP or
to the method of administration (oral intubation), and the NIP report did not
discuss the significance of the presence (in the 15-day study) or the absence
(13- or 103-week studies) of the stomach lesions.
The 15-day study with rats (NIP, 1987) was judged unacceptable for use
in derivation of a Ten-day HA, since no clear treatment-related pattern of
toxicity was observed except for mortality. No histopathological examination
was conducted, and no target organ was identified. Therefore, a LOAEL or
NOAEL was not established.
The 4-week dietary study (Ciba-Geigy, 1977c) was considered and rejected
for derivation of a len-day HA. This study was conducted with a limited
number (five/sex/dose) of animals. Histopathology revealed an increase in
protein resorption droplets in the proximal convoluted epithelium of the
kidneys in male rats. No histological changes were seen in female kidneys
(however, kidney weights were increased significantly in the high-dose group).
Similar findings (accumulation of hyaline droplets in the convoluted tubules
of the renal cortex) were seen in the kidneys of male rats in a 13-week oral
intubation study (NTP, 1987). The 4-week study was judged unsuitable because
of the association between male rat kidney lesions and alpha 2 Mglobulin
(Baetcke et al., 1991) and the small number of animals tested.
Since these data were not judged suitable for derivation of a Ten-day
HA, it is recommended that the Longer-term HA for a 10-kg child (2 mg/I) be
used as a conservative estimate for the Ten-day HA value.
VII-6
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3. Longer-term Health Advisory
The 90-day reproductive toxicity study by Dunnick et al. (1984a), the
basis for the Lifetime HA, is used to derive the Longer-term HA. The LOAEL
for the study is 250 mg/kg/day (adjusted to 179 mg/kg/day) based upon
DMMP-related resorptions in the female rats impregnated by treated males.
Using the adjusted study dose LOAEL of 179 mg/kg/day, the Longer-term HA
for a 10-kg child is calculated as follows:
Longer-term HA = ( 179 mg/kg/day) (10 kg) = 1.79 mg/L (rounded off to
(child) (1000) ( 1 L/day) 2 mg/L or 2,000 g/L)
where:
179 mg/kg/day = LOAEL, based on increased resorptions in female rats that
were impregnated by DMMP treated male rats.
10 kg = assumed weight of a child.
1000 = uncertainty factor (UF), chosen in accordance with
NAS/EPA guidelines in which a NOAEL from an animal
study is employed. This UF includes a factor of 10
for interspecies variability, a factor of 10 for
intraspecies variability, and a factor of 10 for
use of a LOAEL in the absence of a NOAEL.
1 L/day = assumed daily water consumption of a 10-kg child.
The Longer-term HA for a 70-kg adult is calculated as follows:
Longer-term HA ( 179) mci/kg/day) (70 kg ) = 6.27 mg/L (rounded off to 6
(adult) ( ) C / mg/L or 6,000
g/L)
where:
179 mg/kg/day = LOAEL, based on increased resorptions in female rats that
were impregnated by DMMP treated male rats.
70 kg = assumed weight of an adult.
1000 = uncertainty factor (UF), chosen in accordance with NAS/EPA
guidelines in which a NOAEL from an animal study is
employed. This UF includes a factor of 10 for
interspecies variability, a factor of 10 for intraspecies
variability, and a factor of 10 for use of a LOAEL in the
absence of a NOAEL.
2 1/day = assumed daily water consumption of a 70-kg adult.
VII-7
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4. Lifetime Health Advisory
The Lifetime HA represents that portion of an individual’s total
exposure that is attributed to drinking water and is considered protective of
noncarcinogenic adverse health effects over a lifetime exposure. The Lifetime
HA is derived in a three-step process. Step 1 determines the Reference Dose
(RfO), formerly called the Acceptable Daily Intake (Aol). The RfD is an
estimate of a daily exposure to the human population that is likely to be
without appreciable risk of deleterious effects over a lifetime, and is
derived from the NOAEL (or LOAEL), is identified from a chronic (or
subchronic) study, divided by an uncertainty factor(s). From the RfD, a
Drinking Water Equivalent Level (DWEL) can be determined (Step 2). A DWEL IS
a medium-specific (i.e., Drinking water) lifetime exposure level, assuming
100% exposure from that medium, at which adverse, noncarcinogenic health
effects would not be expected to occur. The DWEL is derived from the
multiplication of the RfD by the assumed body weight of an adult and divided
by the assumed daily water consumption of an adult. The Lifetime HA is
determined in step 3 by factoring in other sources of exposure, the relative
source contribution (RSC). The RSC from drinking water may be based on actual
exposure data or, if data are not available, a value of 20% is assumed.
If the contaminant is classified as a Group A or B carcinogen, according to
the Agency’s classification scheme of carcinogenic potential (U.S. EPA, 1986),
then action should be exercised in assessing the risks associated with
lifetime exposure to this chemical.
The 103-week chronic studies in B6C3F 1 mice and F344/N rats (NIP, 1987;
Dunnick et al., 1988) were available for use in deriving the Lifetime HA.
However, the study with mice was judged to be unacceptable for use in deriving
the Lifetime HA because it was considered inadequate owing to poor survival in
both sexes. The decreased survival was not treatment-related and was due to
fighting in males and dosing errors in females.
In the study with rats, DMMP was orally administered at doses of 500 or
1,000 mg/kg, 5 days/week for 103 weeks. In males, an increased incidence of
kidney lesions was noted at both dose levels. No kidney lesions were seen in
females at either level. However, decreased survival and body weight gains
were seen in females at the high-dose level. At the 1000 mg/kg/day level,
VII-8
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body weights were decreased significantly in males and females. Thus, a LOAEL
of 1000 mg/kg/day and a NOAEL of 500 mg/kg/day was determined based on body
weight.
No data on pharmacokinetics in either humans or animals were available.
Therefore, it cannot be determined which species most closely resembles humans
in absorption, metabolism, and excretion of DMMP.
Groups of 20 male Fischer 344 rats were administered dimethyl
methyiphosphonate (DMMP) in corn oil by gavage at doses of 0, 250, 500, 1000,
or 2000 mg/kg/day, 5 days/week during a 90-day period (Dunnick et al., 1984a).
At day 84, treated rats were mated with untreated female Fischer 344 rats.
Reproductive functions were altered at all dose levels. In the 2000-mg/kg/day
dose group, fertility was completely arrested; male rats completely failed to
impregnate females. At 500-, 1000-, and 2000-mg/kg/day levels, there were
significant (p <0.01), dose-dependent decreases in the number of live fetuses
per litter. Animals dosed at 250 mg/kg/day and above had significant (p <0.05
or 0.01) dose-dependent increases in the percentage of resorptions. The LOAEL
for this study is 250 mg/kg/day (179 mg/kg/day when adjusted from a 5-day to a
7-day exposure) based upon the increases in resorption. A NOAEL was not
identified because adverse effects occurred at all dose levels.
The actual study dose of 179 mg/kg/day will be used as the LOAEL for the
calculation of the DWEL. The DWEL is derived as follows:
Step 1: Determination of the Reference Dose (RfD)
RfD = ( 179 ma/ku/day ) = 0.179 mg/kg/day
( ‘ ) (roundeci to
0.2 mg/kg/day or 200 j. g/kg/day)
where:
179 mg/kg/day LOAEL, based on adverse reproductive effects.
1,000 = uncertainty factor (UF), chosen in accordance with
NAS/EPA guidelines using a LOAEL from an animal study.
This UF includes a factor of 10 for interspecies
variability, a factor of 10 for intraspecies
vII-9
-------
variability, and a factor of 10 for use of a LOAEL in
the absence of a NOAEL. An additional factor for use
of a less-than-lifetime study was not applied because
adequate chronic and lifetime studies are available
and were reviewed. A single well conducted chronic
study (NIP, 1987) resulted in a NOAEL double that of
the LOAEL for reproductive effects. The reproductive
toxicity study used as a basis for the RfD
demonstrated the most sensitive toxic endpoint.
Step 2: Determination of the Drinking Water Equivalent Level (DWEL)
OWEL = ( 0.2 (70 ka ) = 7.0 mg/I or 7,000 g/L
where:
0.2 mg/kg/day = RfD.
70 kg = assumed body weight of an adult.
2 I/day = assumed daily water consumption of an adult.
Step 3. Determination of Lifetime Health Advisory
Lifetime HA = ( 7.0 mci L) (0.2 ) = 0.14 mg/I
(rounded off to 0.1 mg/L
or 100 j. g/L)
where:
7 mg/L = Drinking Water Equivalent Level (DWEL).
0.2 = assumed Relative Source Contribution (RSC) (20%) if
actual data are not available; assumed contribution from
drinking water.
10 = OW policy, additional factor of 10 to account for
possible (equivocal) evidence of human carcinogenicity
for Group C chemicals.
C. QUANTIFICATION OF CARCINOGENIC POTENTIAL
The carcinogenic potential of DMMP has been evaluated for male and
female B6C3F 1 mice and F344/N rats. DMMP was not carcinogenic in female rats
or in male or female mice. However, it was carcinogenic in male rats as shown
by increased incidences of tubular cell hyperplasia, tubular cell
adenocarcinomas, hyperplasia of the transitional cell epithelium, and
vu-b
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transitional cell papillomas or carcinomas (combined) of the kidney. In
addition, an increased incidence of mononuclear cell leukemia was seen in male
rats (NIP, 1985).
DMMP administered by gavage, to F344/N rats at 0, 500, or 1,000
mg/kg/day in groups of 50 animals/sex/species, 5 days/week for 103 weeks (NIP,
1987), had an increased incidence of mononuclear cell leukemia in high-dose
male rats (vehicle control, 10/50 [ 20%]; low dose, 11/50 [ 22%]; high dose,
17/50 [ 34%]) which exceeded the incidence of that seen in historical vehicle
controls (6-28%). The male rats also exhibited an increased incidence of
transitional cell papillomas and carcinomas (combined) (8/50 low dose, 3/49
high dose) of the pelvic epithellum In the kidneys. Other kidney cancers that
developed in the male rat, i.e., renal tubular carcinomas, were not considered
to be relevant to humans, because of an association with alpha 2 g1obulin
(Baetke et al., 1991).
1. Dose-ResDonse Data (Carcinogenicity. Oral ExDosure )
Individual and combined organ cancer incidence from the NIP (1987) study
are shown in Table Vu-i.
Tumor Type: Mononuclear Cell Leukemia, Kidney Transitional
Cell Papillomas and Carcinoma
Test Animals: Rat, F344/N, Male
Route: Oral, Gavage
Reference: NIP, 1987
Dose
Human
Administered Equivalent* Tumor
( m /ka/dav) ( ma/ku/day) mci dence**
0 0 10/43
357 67 18/41
714 130 20/43
* Administered Dose + (70 kg/rat weight) O•33; Rat weights were averaged
from study day 44 to 105 and were 0.476 kg, 0.465 kg, and 0.420 kg for
the control, low- and high-dose groups, respectively.
** Animals that died before 60 days were excluded from the risk estimate.
VII- 11
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Table VU-i. Summary of Data Used to Quantitate the Carcinogenic
Potential of DMMP
Dose Groups (Adjusted Dose)’
(ma/ka/dav)
0 500
(357) 1000 (714)
Number of Animals 50(43)” 50 (41) 50 (43)C
Mononuclear Cell Leukemia (MCL):
- Multiple Organs 10 10 17
- Spleen 0 1 0
- Combined Multiple Organs 10 11
and Kidney
Kidney Transitional Cell:
- Papilloma 0 7****** 3*
- Carcinoma 0 1 0
- Combined Papilloma and 0 8 3
Carcinoma
Combined MCL and Kldne? 10 18*,**.*** 20*
Actual dose adjusted from a 5—day/week exposure to a 7-day/week exposure. i.e.. Dose x 5/7.
“The number In parenthesis is the number of animals that were included in the risk estimate after
excluding those that died before the first case of cancer.
‘Only 49 animals were examined for kidney effects.
‘Number of tumor bearing animals. One animal in the 500 mg/kg/day group had both MCL and kidney cell
cancer, it was counted only once In the combined totals.
Significant by Life Table Tests (p cO.05 or p <0.001) (NIP. 1987).
**Signlflcant by Incidental Tumor Test (p <0.05 or p <0.001) (NIP. 1987).
***Signiflcant by Fisher Exact Test (p <0.05) (NTP. 1987).
Source: NIP. 1987
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The administered doses are time-weighted averages adjusted for frequency
of exposure (5/7 days). Human equivalent doses were adjusted for the actual
weights of the animals averaged from study day 45 to termination (0.476 kg,
controls; 0.465 kg, low-dose group; 0.420 kg, high-dose group). The incidence
of mononuclear cell leukemia in the vehicle control group was used in
modeling. Vehicle controls did not develop transitional cell papilloma and
carcinoma.
2. Summary of Risk Estimates
Oral Slope Factor (mg/kg/day)’ -- 5E-3
Drinking Water Unit Risk (per g/L) -- 1E-7
Extrapolation Method -- Linearized Multistage Procedure, Extra
Risk
3. Drinking Water Concentrations at Soecified Risk Levels
Risk Level
E-4 (1 in 10,000) 7E + 2 g/L
E-5 (1 in 100,000) 7E + 1 &g/L
E-6 (1 in 1,000,000) 7E + 0 g/L
The multistage model was used for high- to low-dose extrapolation (Crump
and Watson, 1979; Howe and Crump, 1982). GLOBAL86 was used to fit the data in
the experimental dose range and to obtain upper 95% confidence limits on risk.
The multistage model conforms to a biological model of tumor initiation and
promotion (Crump et al., 1977) and provided an adequate fit to the dose-
response data for DMMP. The relationship of the concentration ( g/L) of a
chemical in drinking water to cancer risk is expressed as follows:
35.000 x R = C
q 1 *
where:
35,000 = conversion factor for mg to g and exposure assumption
that a 70-kg adult consumes 2 L of water/day.
ql* = (mg/kg/day)’, human slope factor.
VII -13
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R = i0 , i0 , 106, etc.
C = concentration of chemical in g/L.
For comparison purposes, drinking water concentrations associated with
an excess cancer risk of 106 are 2 g/L for the one-hit model, and
significantly less than 0.0001 g/L for the multihit, probit, logit, and
Weibull models, respectively. The parameter estimates for these models were
computed with RISK81 (Kovar and Krewski, 1981) and MULTI8O (Rai and VanRyzin,
1980; Lavenhar, 1986).
4. Discussion of Confidence (Carcinogenicity Oral Exposure )
There are two carcinogenicity assays with DMMP, both conducted with
rodents, rats and mice (NIP, 1987). Positive evidence in both studies are
limited; male rat kidney effects are complicated by an association with
alpha 211 globulin, and results in mice are inconclusive due to decreased
survival. There is an increased incidence of mononuclear cell leukemia in
only the high-dose group of male rats. Transitional cell papilloma and
carcinoma in the renal pelvis also occur in male rats of both dose groups; the
appearance of this additional tumor type increases the confidence in the
Group C (possible human carcinogen) classification. Female rats did not
develop cancer from DMMP exposure.
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VIII. OTHER CRITERIA, GUIDANCE, AND STANDARDS
No information concerning other criteria, guidance, and standards for
DMMP were found in the available literature.
VIII-1
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IX. ANALYTICAL METHODS
Traditional methods used in the analysis of organophosphorus compounds
involved mass spectrometry (MS) analysis using electron impact ionization and
chemical ionization (CI). Electron impact ionization generally leads to
extensive fragmentation, while detection limits (2.0 x 10”g, DMMP) are
estimated based on CI studies utilizing methane. Since neither method
exhibits the necessary selectivity for organophosphorus compounds, they are
usually used together with gas chromatography (GC) (Groenewold and Todd,
1985). Van der Veken and Herman (1983) used GC with an infrared detector to
determine the existence of possible conformers of DMMP. DMMP was found to
exist in the gas phase as a single conformer. Aurian-Blajemi and Boucher
(1989) used fourier transform infrared (FuR) spectroscopy to study the gas-
solid interactions of DMMP with metal oxides. This method is a variation of
traditional infrared GC analysis. However, GC/MS analysis does not allow for
continuous analysis, and it is difficult to impossible when unknown
inseparable interferents are present. Additional analytical methods for DMMP
include nuclear magnetic resonance (NMR) and plasma chromatography (Berkowitz
et al., 1978).
In an attempt to develop a mass spectrometry ionization method that is
selective for organophosphorus compounds and would have the sensitivity of CI,
Groenewold and Todd (1985) used molecular secondary ion mass spectrometry
(SIMS) for the detection of gaseous organophosphorus compounds. The best
matrix for the detection of DMMP was polyphosphoric acid, and the limit of
detection was estimated to be 1.6 x 10 g.
IX- 1
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X. TREATMENT TECHNOLOGIES
There were no specific treatment technologies for removing DMMP from
water reported in the literature. The following describe studies that
resulted in the destruction or removal of DMMP in laboratory settings; the
methods may not be appropriate for removal of the contaminant from drinking
water sources.
Radziemski (1981) studied the laser-induced photodestruction of DMMP in
vapor and liquid phases. Photodissociation was observed at all wavelengths,
but was most efficient with argon-fluoride (ArF) in the vapor phase in the
presence of oxygen. DMMP irradiated at 266 nm had a carbon atom quantum yield
of 1.0%, while gaseous DMMP irradiated at 193 nm had a yield of 8.4%.
Decomposition products included hydrocarbon gases, CU, C0 2 , H 2 , and H 2 0.
Fraser et al. (1985) studied the decomposition mechanisms and products
of DMMP in an alternating current discharge. DMMP vapor was placed in a
helium stream in an atmospheric pressure alternating current discharge.
Efficiency has been determined to be 50-100% and is dependent upon the input
concentration and flow rate. Primary discharge products were trimethyl
phosphite and methanol.
As part of a program to investigate catalytic methods for the removal of
toxic chemicals from air, Graven et al. (1966) studied the catalytic
conversion of DMMP vapor over two types of platinum-alumina catalysts. Values
for temperatures, residue times, and catalyst particle sizes were 300-500°C,
0.15-2.7 seconds, and 0.31-2.4 mm, respectively. Product analyses indicated
that the initial reaction was hydrolysis to yield methanol and a phosphorus
acid.
Aurian-Blajemi and Boucher (1989) studied the gas-solid interactions of
DMMP with metal oxide surfaces at various temperatures (25-102°C) for various
periods (0.5 hours to several days). In an activated process, DMMP adsorbed
to the oxide surface. The adsorption was virtually irreversible; therefore,
no significant catalysis was observed. The authors concluded that the metal
oxides were good for the concentration stage of decontamination.
x- 1
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Even though DMMP strongly adsorbs to activated carbon (Berkowitz et al.,
1978), the use of granular activated carbon (GAC) treatment, a common
techno ogy for removing organic contaminants from water, was not found in the
literature.
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XI. CONCLUSIONS
Based on the adverse liver effects in rats following oral (gavage)
administration of DMMP for 13 weeks, the One-day, Ten-day, and Longer-term HA
for exposure in a 10-kg child is 2 mg/L (2,000 j. g/L); the Longer-term HA for
exposure in a 70-kg adult is 6 mg/L (6,000 g/L). A Lifetime HA of 0.1 mg/L
(100 g/L) for a 70-kg adult is based on a Drinking Water Equivalent Level
(DWEL) of 7 mg/L (7,000 .&g/L). The DWEL is based on a Reference Dose (RfD)
of 0.2 mg/kg/day. The RfD is based on a LOAEL of 179 mg/kg/day, where the
effect was reproductive toxicity in rats orally administered DMMP for 90 days.
Based on the study by NTP (1987), DMMP is classified as Group C: Possible
Human Carcinogen. The classification of DMMP in EPA Group C is based on
limited (equivocal) evidence of carcinogenicity in animals and the absence of
human data.
A comparison report “Data Deficiencies/Problem Areas and Recommendations
for Additional Data Base Development for OMMP” (see Appendix) summarizes the
scope of existing data reviewed for this HA. This comparison report
delineates the areas where additional data and/or a clarification of existing
data would be appropriate for a sound HA.
XI-’
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XII. REFERENCES
Aibright and Wilson, Inc. 1982. Dialkyl Alkyiphosphonates. Product Information
Bulletin No. OPB-2A. Aibright and Wilson, Americas Inc.
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reproductive tract lesions in Male F344 rats after treatment with dimethyl
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submitted by Ciba-Geigy to Office of Toxic Substances, EPA, Washington, DC. FYI-
OTS-0784-0242. November 19.
Ciba-Geigy. 1976b. Acute Oral 1050 in the Rat of FAT 80021/B.
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DC. FYI-OTS-0784-0242. March 18.
Ciba-Geigy. 1976c. Acute Dermal 1D50 in Rats (of FAT 80021/B). Report submitted
by Ciba-Geigy to Office of Toxic Substances, EPA, Washington, DC. FYI-OTS-0784-
0242. March 31.
Ciba-Geigy. 1976d. Skin Irritation on Rabbits Upon Single Application (of FAT
80021/B). Report submitted by Ciba-Geigy to Office of Toxic Substances, EPA,
Washington, DC. FYI-OTS-0784-0242. January 8.
Ciba-Geigy. 1976e. Primary Skin Irritation Tests With FAT 80021/B in Albino
Rabbits. Report submitted by Ciba-Geigy to Office of Toxic Substances, EPA,
Washington, DC. FYI-OTS-0784-0242. November 19.
Ciba-Geigy. 1976f Irritation in the Rabbit Eye (of FAT 80021/B). Report
submitted by Ciba-Geigy to Office of Toxic Substances, EPA, Washington, DC.
FYI-OTS-0784-0242. January 8.
XII-1
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Ciba-Geigy. 1976g. Skin Sensitization Test With FAT 80021/B in Albino Guinea
Pigs. Report submitted by Ciba-Geigy to Office of Toxic Substances, EPA,
Washington, DC. FYI-OTS-0784-0242. September 27.
Ciba-Geigy. 1976h. Testing for Mutagenic Activity in FAT 80021/B and FAT
90055/B. Report submitted by Ciba-Geigy to Office of Toxic Substances, EPA,
Washington, DC. FYI-OTS-0784-0242. March 1.
Ciba-Geigy. 1977a. Acute Intravenous LD5O in the Mouse and in the Rat of FAT
80021/B. Report submitted by Ciba-Geigy to Office of Toxic Substances, EPA,
Washington, DC. FYI-OTS-0784-0242. November 29.
Ciba-Geigy. 1977b. Acute Inhalation Toxicity in the Rat of FAT 80021/B. Report
submitted by Ciba-Geigy to Office of Toxic Substances, EPA, Washington, DC. FYI-
OTS-0784-0242. June 2.
Ciba-Geigy. 1977c. One Month Dietary Toxicity Study in Rats with Compound FAT
80021/B. Report submitted by Ciba-Geigy to Office of Toxic Substances, EPA,
Washington, DC. FYI-OTS-0784-0242. June 28.
Ciba-Geigy. 1978a. Effects of 3-Day Oral Treatment on Plasma Cholinesterase
Activity in Rats. Report submitted by Ciba-Geigy to Office of Toxic Substances,
EPA, Washington, DC. FYI-OTS-0784-0242. March 7.
Ciba-Geigy. 1978b. Reproduction Study - FAT 80021/B - Rat - Seg. II. Report
submitted by Ciba-Geigy to Office of Toxic Substances, EPA, Washington, DC. FYI-
OTS-0784-0242. January 16.
Ciba-Geigy. 1978c. SalmonellalMammalian - microsome mutagenicity test with FAT
80021/B. Report submitted by Ciba-Geigy to Office of Toxic Substances, EPA,
Washington, DC. FYI-OTS-0784-0242. June 16.
Ciba-Geigy. 1978d. Acute Oral Toxicity and Neurotoxicity Study of FAT 80021/B
in the Domestic Fowl. Report submitted by Ciba-Geigy to Office of Toxic
Substances, EPA, Washington, DC. FYI-OTS-0784-0242. July 10.
Dunnick JK, Harris MW, Gupta BN, Chapin RE, Lamb JC. 1983. Reproductive
toxicity of dimethyl methyiphosphonate (DMMP) in the male Fischer 344 rat.
Toxicologist 3(1) :19. (Abstract only.)
Dunnick JK, Gupta BN, Harris MW, Lamb JC. 1984a. Reproductive toxicity of
dimethyl methyiphosphonate (DMMP) in the male Fischer 344 rats. Toxicol. Appi.
Pharmacol. 72:379-387.
Dunnick JK, Solleveld HA, Harris MW, Capin R, Lamb JC. 1984b. Dimethyl
methyiphosphonate induction of dominant lethal mutations in male mice. Mutat.
Res. 138:213-218.
Dunnick JK, Eustis SL, Haseman JK. 1988. Development of kidney tumors in the
male F344/N rat after treatment with Dimethyl methyiphosphonate. Funda. Appl.
Toxicol. 11:91-99.
Fraser ME, Eaton HG, Sheinson RS. 1985. Initial decomposition mechanisms and
products of dimethyl methyiphosphonate in an alternating current discharge.
Environ. Sd. Technol. 19(10):946-949.
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Groenewold GS, Todd PJ. 1985. Detection of gaseous organophosphorus compounds
using secondary ion mass spectrometry. Anal. Chem. 57:886-890.
Hardin BD, Schuler RL, Burg JR, Booth GM 1 Hazelden KP, Mackenzie KM, Piccirillo
VJ, Smith KN. 1987. EvaluatIon of 60 chemicals in a preliminary developmental
toxicity test. Teratogen. Carcinogen. Mutagen. 7:29-48.
Kirk-Othmer. 1980. Encyclopedia of Chemical Technology. Vol. 10, 3rd Ed. New
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Hollingshaus JG, Armstrong D, Tola RF, McCould 1, Fukuto TR. 1981. Delayed
toxicity and delayed neurotoxicity of phosphorothioate and phosphonothioate
esters. J. Toxicol. Environ. Health 8:619-627.
Mabey W, Mill 1. 1978. Critical review of hydrolysis of organic compounds in
water under environmental conditions. J. Phys. Chem. Ref. Data 7(2):383-415.
Mattie Dr, Hixson CJ, Gaworski CL, Thorson GR. 1987. Toxic effects of inhaled
dimethyl methyiphosphonate (DMNP) on the testes of Fischer-344 rats. Toxicology
47:23 1-232.
Mortelmans K, Haworth S. Lawlor 1, Speck W, Tamer B, Zeiger E. 1983.
Salmonella inutagenicity tests; II. Results from the testing of 270 chemicals.
Environ. Mutagen. 8(SuppL7):1-119.
NIP. 1987. National Toxicology Program. Toxicology and Carcinogenesis Studies
of Dimethyl Methyiphosphonate (CAS No. 756-79-6) in F344/N Rats and 66C3F1 Mice.
(Gavage Studies). NTP TR 323, NTP, Research Triangle Park. NIH Publication No.
88-2579, U.S. Department of Health and Human Services. Public Health Service,
National Institutes of Health.
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Exposure Assessment for Rocky Mountain Arsenal, Volume II, Toxicity Assessment,
Version 4.]. Contract No. DMA 15-88-0-0024. Available from Program Manager for
Rocky Mountain Arsenal, AMXRM-PM, Commerce City, CO.
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(First Year), August 1991. Contract No. DAM 15-88-0-0022. Commerce City, CO:
U.S. Army Program Manager for Rocky Mountain Arsenal.
Radziemski U. 1981. Laser-induced photodestruction of the organ-phosphates:
DIMP and IJMMP. J. Environ. Sd. Health B16(3):337-361.
Sivak A. 1983. Evaluation of Dimethyl Methylphosphonate and Exotetrahydrodi-
(cyclopentadiene) in a Battery of j.fl vitro Short Term Assays. Final Report.
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Medical Research Laboratory, AMD, AFSC, Wright-Patterson Air Force Base, OH.
Available from NTIS, Springfield, VA. AD-A124785.
XII-3
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Stauffer Chemical Co. 1983. FYROL DMMP (dimethyl mehtylphosphnate). Letter from
Stauffer Chemical Company. Submitted to Office of Toxic Substances, EPA,
Washington, DC. FYI-OTS-0483-0242. April 7.
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Repository No. 90-33/90-34. Contract No. DAADO5-89-C0224. Research Triangle
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Information Profile: Dimethyl Methyiphosphonate. Draft: Prepared by Dynamac
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Risk Assessment. Fed. Reg. 51(188): 33992-34003. September 24.
Van der Veken BJ, Herman MA. 1983. An infrared study of the gas-phase
conformation of dimethyl methylphosphonate. J. Mol. Structure 96:233-245.
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APPENDIX
Data Deficiencies/Problem Areas and Recommendations
for Additional Data Base Development for DMMP
-------
DATA BASE DEVELOPMENT
A. OBJECTIVES
The objective of this document is to provide an evaluation of data
deficiencies and/or problem areas encountered in the review process for DMMP
and to make recommendations, as appropriate, for additional data base
development. This document is presented as an independent analysis of the
current status of DMMP toxicology, as related to its possible presence in
drinking water, and it includes a summary of the background information used
in development of the Health Advisory (HA). For greater detail on the
toxicology of DMMP, the Health Advisory on DMMP should be consulted.
B. BACKGROUND
Dimethyl methyiphosphonate (DMMP) is a colorless liquid used in military
munitions formulations.
No studies were found in the available literature on the pharmacokinetics of
DMMP. However, acute, subchronic, and chronic oral toxicity studies in mice
and rats indicate that DMMP is absorbed via the gastrointestinal tract.
No information was available on human occupational exposure to DMMP. Exposure
may occur primarily under occupational settings at production sites where DMMP
is used as a flame retardant and as a viscosity depressant in polyester and
epoxy resins. Dimethyl methyiphosphonate has been detected in groundwater at
one military installation at levels that range from 6.5 .&g/L to 1,300 g/L
(PMRMA, 1991).
In a repeated-insult patch test with humans, aqueous solutions of DMMP
produced mild skin irritation at a concentration of 10% (v/v) and moderate to
severe irritation at the 20% (v/v) level (Ciba-Geigy, 1976a).
Acute toxicity studies indicate that DMMP is practically nontoxic when
administered to mice and rats via the oral route with LD 50 values of >6,810
mg/kg in mice (NTP, 1987) and 10,190 mg/kg in rats (Ciba-Geigy, 1976b).
Animals exhibited ataxia, tremors, ventricumbency, unsteady gait, muscular
A- 2
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hypertonia and hypotonia, prostration, and reductions in spontaneous motility.
DMMP was slightly toxic by the intravenous route with LD 50 values of 912 and
1,050 mg/kg in mice and rats, respectively (Ciba-Geigy, 1977a). DMMP elicited
mild skin irritation and minimal ocular Irritation in rabbits. DMMP was not a
skin sensitizer in rabbits (Ciba-Geigy, 1976c,d,e,f,g).
Oral administration of DMMP in tapwater at 0, 1, 10, 100, or 1,000 mg/kg/day
for 3 days to male and female rats produced no adverse effects on mortality,
clinical signs, body weight, or food consumption. Plasma cholinesterase
levels were depressed only in rats treated with 1,000 mg/kg/day; approximate
reductions of 30% in males and 40-50% in females were observed over a 4-hour
period as compared with control values taken at the same time. No effects on
plasma cholinesterase levels were observed in rats at the other dose levels.
The No-Observed-Adverse-Effect level (NOAEL) was 100 mg/kg/day for plasma
cholinesterase (Ciba-Geigy, 1978a). By comparison, mice dosed by gavage with
DMMP in water at doses up to 2,000 mg/kg/day for 90 days did not exhibit
depressed plasma cholinesterase levels (Dunnick et al., 1984b).
In a 15-day study with a limited number of mice and rats (five/sex/species),
histologic changes were observed in the stomachs of male mice orally
administered 1,250 mg DMMP/kg/day and in females orally administered 5,OO0
mg DMMP/kg/day. The Lowest-Observed-Adverse-Effect Level (LOAEL) was 1,250
mg/kg/day, based on the stomach changes in males. No gross pathological
changes were seen in male or female rats at levels up to 15,000 mg/kg/day;
however, mortality was seen in both sexes dosed at 5,O0O mg/kg/day. Neither
a NOAEL nor LOAEL was established in rats because a target organ for toxicity
was not identified and histopathology was not conducted (NIP, 1987).
In a 4-week dietary study with rats, DMMP caused an increase in the protein
resorption droplets in the proximal convoluted epithelium of the kidneys of
males fed diets containing 2,000, 6,000, or 20,000 ppm (178, 535, or 1,790
mg/kg/day, respectively); the effect was more pronounced with increasing
levels of DMMP. No kidney changes were observed in females (Ciba-Geigy,
1977C).
In a subchronic toxicity study, male and female mice were administered DMMP,
by gavage, at doses ranging from 250 to 8,000 mg/kg/day, 5 days/week for 13
A-3
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weeks. Except for mortality in both sexes at higher (4,000 or 8,000
mg/kg/day) dose levels, no adverse effects were observed on body weight,
clinical signs, food consumption, gross necropsy, or histopathiogy. The
stomach lesions observed in the 15-day study were not seen in this study. No
compound-related cause for the mortality at the two upper levels was reported.
Therefore, neither a NOAEL nor LOAEL was established (NIP, 1987).
In a subchronic toxicity study, male and female rats were administered DMMP,
by gavage, at doses ranging from 250 to 4,000 mg/kg, 5 days/week for 13 weeks.
DMMP, at doses 2,000 mg/kg/day, caused decreased survival, body weight gain,
and increased liver-to-body weight ratios in males and females.
Histopathology revealed kidney changes (nephrosis and hyaline droplet
generation) in males at all dose levels starting at 250 mg/kg; no kidney
changes were seen in females. The minimal to mild hypospermatogenesis seen in
the testes of treated rats was not dose-dependent. Based on the increased
relative liver weights in males and females, the LOAEL is 2,000 mg/kg/day and
the NOAEL is 1,000 mg/kg/day (NIP, 1987).
In a chronic study, DMMP was administered, by gavage, to male and female mice
at doses of 0, 1,000, or 2,000 mg/kg, 5 days/week for 103 weeks. Survival was
decreased in males at both dose levels and in females at the high dose. The
decreased survival was not treatment-related; it was due to fighting In males
and dosing errors in females. Mean body weights were decreased in both sexes
in the high-dose group, and the incidence of hepatocytomegaly was increased in
treated males at both levels compared with vehicle controls. No increases in
nonneoplastic liver lesions were seen in female mice. This study was judged
to be inadequate owing to poor survival; therefore, neither a NOAEL nor LOAEL
was established (NIP, 1987; Ounnick et al., 1988).
DMMP was administered, by gavage, at doses of 0, 500, or 1,000 mg/kg to male
and female rats, 5 days/week for 103 weeks. Survival and mean body weights
were decreased in both sexes at the high dose. Treatment-related kidney
changes observed in males at both levels included nephropathy and
calcification of the renal papilla. No kidney lesions were seen in females.
Based on the significant body weight decreases, the LOAEL is 1,000 mg/kg/day
(NTP, 1987; Dunnick et al., 1988) and the NOAEL is 500 mg/kg/day.
A-4
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DMMP was found to be noncarcinogenic to female F344/N rats and male or female
B6C3F 1 mice. However, the study with mice was judged to be inadequate to
evaluate the carcinogenic potential of DMMP owing to poor survival in both
sexes (see discussion above) (NIP, 1987).
Following oral administration at doses of 500 or 1,000 mg/kg, 5 days/week for
103 weeks, DMMP was carcinogenic to male F344/N rats, inducing transitional
cell papillomas or carcinomas (combined) of the pelvic epithelium in the
kidneys. In addition, DMMP increased the incidence of mononuclear cell
leukemia in male rats. Male rats also developed renal tubular cell
adenocarcinomas; however, this effect is considered to be associated with
alpha 216 globulin and not relevant to humans (Baetcke et al., 1991). DMMP was
not carcinogenic to male and female B6C3F 1 mice, but the study was considered
to be inadequate owing to decreased survival in both sexes (NIP, 1987). DMMP
is classified in Group C: Possible Human Carcinogen (NIP, 1987).
DMMP was found to be mutagenic by inducing forward mutations in mouse lymphoma
cells in the absence of metabolic activation and sister chromatid exchanges in
Chinese hamster ovary (CHO) cells with and without activation (NTP, 1987). It
gave limited evidence of clastogenicity in CHO cells in the absence of
metabolic activation (Sivak, 1983; NIP, 1987). lice (1990) demonstrated that
DMMP induced forward mutations in the CHO cell HGPRT assay with and without
metabolic activation. hi vivo , DMMP induced sex-linked recessive lethal
mutations in Drosoohila (NIP, 1987). DMMP was nonmutagenic in bacterial
mutagenicity tests in several strains of Salmonella (Ciba-Geigy, 1976h, 1978c;
Sivak, 1983; Mortelmans et al., 1986), did not increase neoplastic
transformations in BALB/c 313 cells (Sivak, 1983), and did not induce
reciprocal translocations In DrosoiThila j . vivo (NIP, 1987). DMMP gave
positive results in dominant-lethal assays in mice and rats (Dunnick et al.,
1984a,b).
DMMP was shown to be toxic to the male reproductive system. In male rats
following oral administration at doses ranging from 250 to 2,000 mg/kg, 5
days/week for 90 days, DMMP induced dose-dependent decreases in sperm
motility, sperm counts, and male fertility index. Histologic changes were
observed in the testes, epididymis, and prostate glands. DMMP altered
reproductive functions at all dose levels by causing a decrease in the number
A-5
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of live fetuses per litter, and an increase in the percentage of resorptions.
The LOAEL for reproductive effects was the lowest dose tested, 250 mg/kg/day
(Dunnick et al., 1984a). In an inhalation study, exposure of male rats to
DMMP vapors at concentrations of 25 or 250 ppm continuously for 90 days
induced histologic changes in the testes and epididymis (Mattie et al., 1987).
DMMP was not found to be teratogenic. No developmental effects were observed
in mice following oral administration of 4,175 mg/kg/day on gestation days
6-13 (Hardin et al., 1987). DMMP induced minimal fetotoxicity (reduced fetal
weight and delayed skeletal maturation) only at maternally toxic (1,000 or
2,000 mg/kg/day) doses in rats dosed during gestation days 6-15. No maternal
toxicity, embryotoxicity, or fetotoxicity was observed at the 100-mg/kg/day
dose. DMMP did not alter fetal anomalies (Ciba-Geigy, 1978b).
No delayed neurotoxicity (based on histopathology) was seen in hens following
oral administration of 1,999 or 3,998 mg DMMP/kg initially and after 21 days
(Ciba-Geigy, 1978d). Birds exhibited acute toxicity including ataxia, curved
position, apathy or sedation, and fluttered feathers. In another study, an
intraperitoneal injection of 50 mg DMMP/kg for 10 days produced no delayed
neurotoxicity in hens (Hollingshaus et al., 1981).
Based on the adverse liver effects of rats administered DMMP via gavage, the
Longer-term Health Advisory (HA) for exposure in a 10-kg child has been
determined to be 70 mg/I (70,000 ag/I). In the absence of adequate animal
data to determine a One-day or Ten-day Health Advisory, the Longer-term HA for
a 10-kg child, 70 mg/L (70,000 mg/L), is used as a conservative estimate of
the One-day or Ten-day HA. The Longer-term HA for an adult is 250 mg/L
(250,000 g/L). A lifetime HA of 0.1 mg/I (100 Mg/I) for a 70-kg adult was
determined based on a Drinking Water Equivalent level (DWEL) of 7 mg/L (7,000
g/L). The DWEL is based on a Reference Dose (RfD) of 0.2 mg/kg/day.
The RfD is based on a LOAEL of 179 mg/kg/day where the toxic endpoint was
adverse reproductive effects in rats following oral (gavage) administration
for 90 days.
A-6
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C. DISCUSSION
Available data on the pharmacokinetics, health effects, analysis, and
treatment of DMMP have been reviewed.
No data were available on the pharmacokinetics of DMNP either in humans or
animals. Acute, subchronic, and chronic toxicity studies in mice and rats
indicate that DMMP is absorbed via the oral route. Therefore, the data gap on
pharmacokinetics needs to be filled in evaluating the pharmacokinetics of
DMMP.
Human exposure data were not available. No studies evaluating the systematic
toxicity of DMMP were available. Only one study evaluating the skin
irritation and sensitization potential of DMMP in humans was available.
Further studies are needed to fill the data gap in humans.
Acute toxicity studies for DMMP administered via the oral, inhalation,
intravenous, and dermal routes in mice, rats, and rabbits were available.
OMMP was practically nontoxic via the oral and dermal routes and slightly
toxic via the intravenous route.
Fifteen-day oral toxicity studies in mice and rats were available. Effects
were seen in the stomachs of both sexes of mice, with males being more
sensitive than females. However, similar treatment-related effects were not
seen in mice treated for 13 or 103 weeks in followup studies.
A 30-day dietary study with rats showed renal effects in male rats; no renal
or other effects were seen in female rats.
Five longer term studies (90 days) were available: four examined the effects
of DMMP following gavage administration (mice and rats) and, in the fifth,
rats were exposed via inhalation to DMMP vapors. In the study with mice,
except for mortality at high levels, no treatment-related systemic toxicity
was observed. Histopathology from three of the studies revealed kidney
nephrosis and accumulation of hyaline droplets in the convoluted tubules of
the renal cortex in treated males; no kidney lesions were seen in females.
The kidney lesions are associated with alpha 21 globulin found only in male rats
A-7
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and, therefore, are not relevant to humans. These studies indicated a LOAEL
of 250 mg/kg/day for reproductive toxicity. An inhalation study showed
testicular lesions.
Two lifetime studies (mice and rats) evaluated the chronic toxicity and
carcinogenicity of DMMP following oral (gavage) administration for 103 weeks.
Except for an increase In the incidence of hepatocytomegaly in male mice, no
chronic toxicity or carcinogenicity was observed in mice. However, the study
was considered inadequate owing to poor survival in both sexes; this was
attributed to fighting among males and dosing errors in females. DMMP did not
induce chronic toxicity and was not carcinogenic to female rats. It was,
however, carcinogenic to male rats, inducing hyperplasia of the transitional
epithelium, and transitional cell papillomas or carcinomas (combined) of the
pelvic epithelium in the kidneys and mononuclear cell leukemia. Renal tubular
cell hyperplasia and carcinoma are considered to be associated with alpha 2 -
globulin and not relevant to humans. Based on significant body weight
decreases in male and female rats, the lifetime studies indicated a LOAEL of
1,000 mg/kg/day and a NOAEL of 500 mg/kg/day.
Three studies in male rats (two gavage studies and one inhalation study)
examined the reproductive toxicity of DMMP. DMMP was shown to be a
reproductive toxin. It induced lesions in the testes, epididymis, and
prostate glands and affected reproductive functions in males. The LOAEL
established was 250 mg/kg/day.
Available developmental toxicity studies in mice and rats found DMMP not to be
a teratogen. Not all categories of genotoxicity were investigated. A
mutagenicity test in an eukaryotic microorganism with and without activation
and tests for DNA damage/repair would fulfill this data.
Available acute neurotoxicity studies (oral and intraperitoneal) in hens
showed that DMMP was not a neurotoxin. However, additional studies (21 days)
are needed to substantiate this finding.
A-8
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D. CONCLUSIONS/RECOMMENDATIONS
Based on the above discussion, the following conclusions/recommendations can
be made:
1. The available studies on DMMP toxicity are adequate for development of
Longer-term and Lifetime Health Advisories and estimating One-day and
Ten-day Health Advisories which are useful in dealing with the potential
contamination of drinking water. it is recommended that appropriate
subacute studies be performed to address emergency exposure for One- and
Ten-day Health Advisories.
2. It is recommended that a 21-day neurotoxicity study be performed in hens
and that brain and blood (RBC and plasma) cholinesterase studies be
performed for a minimum of 14 days in appropriate animal models.
3. It Is recommended that toxicokinetic studies be performed in animals and
humans.
4. It is recommended that a teratology study be performed in rabbits.
5. It is recommended that additional genotoxicity studies be performed in
microbial and nonmicrobial cell systems.
6. It is recommended that epidemiological studies of people exposed
occupationally to DMMP be conducted to elucidate specific health
effects.
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E. REFERENCES
Baetcke, K.P., G.C. Hard, I.S. Rodgers, and R.E. McGaughy. 1991. Alpha 2 -
globulin: association with chemically induced renal toxicity and neoplasia in
the male rat. U.S. Environmental Protection Agency, Washington, DC
EPA/625/3-91-019F.
Ciba-Geigy. 1976a. Human Repeated Insult Patch Test With FAT 80021/B.
Report submitted by Ciba-Geigy to Office of Toxic Substances, EPA, Washington,
DC. FYI-OTS-0784-0242. November 19.
Ciba-Geigy. 1976b. Acute Oral 1D50 in the Rat of FAT 80021/B.
Report submitted by Ciba-Geigy to Office of Toxic Substances, EPA, Washington,
DC. FYI-OTS-0784-0242. March 18.
Ciba-Geigy. 1976c. Acute Dermal 1050 in Rats (of FAT 80021/B). Report
submitted by Ciba-Geigy to Office of Toxic Substances, EPA, Washington, DC.
FYI-OTS-0784-0242. March 31.
Ciba-Geigy. 1976d. Skin Irritation on Rabbits Upon Single Application (of
FAT 80021/B). Report submitted by Ciba-Geigy to Office of Toxic Substances,
EPA, Washington, DC. FYI-OTS-0784-0242. January 8.
Ciba-Geigy. 1976e. Primary Skin Irritation Tests With FAT 80021/B in Albino
Rabbits. Report submitted by Ciba-Geigy to Office of Toxic Substances, EPA,
Washington, DC. FYI-OTS-0784-0242. November 19.
Ciba-Geigy. 1976f Irritation in the Rabbit Eye (of FAT 80021/B). Report
submitted by Ciba-Geigy to Office of Toxic Substances, EPA, Washington, DC.
FYI-OTS-0784-O242. January 8.
Ciba-Geigy. 1976g. Skin Sensitization Test with FAT 80021/B in Albino Guinea
Pigs. Report submitted by Ciba-Geigy to Office of Toxic Substances, EPA,
Washington, DC. FYI-OTS-0784-0242. September 27.
Ciba-Geigy. 1976h. Testing for Mutagenic Activity in FAT 80021/B and FAT
90055/B. Report submitted by Ciba-Geigy to Office of Toxic Substances, EPA,
Washington, DC. FYI-OTS-0784-0242. March 1.
Ciba-Geigy. 1977a. Acute Intravenous LD5O in the Mouse and in the Rat of FAT
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