United States Office of Pesticides and Toxic Substances
Environmental Protection Office of Pesticide Programs (TS-766C)
Agency Washington, DC 20460
vvEPA Pesticide
Fact Sheet
Name of Chemical: METHOXYCHLOR
Reason for Issuance: REGISTRATION STANDARD
Date ISSUed: December 1988
Fact Sheet Number: is?
1. DESCRIPTION OF CHEMICAL
Generic name: 1,1,l-trichloro-2,2-bis(4-
methoxyphenyl) ethane
Common name: Methoxychlor
Trade Names: Marlate, Prentox, and Methoxcide
Other Chemical Nomenclature: 1,1,l-trichloro-2,2-di(4-
methoxyphenyl)ethane; 1,1-
(2,2,2-tri chloroethylidene)-
bis[4-methoxybenzene]; 1,1,1-
trichloro-2,2-bis(p-
methoxyphenyl)ethane; 2,2-
b i s)p-methoxypheny1) -1,1,1 -
trichloroethane
CAS Registry No.: 72-43-5
EPA Pesticide Chemical Code (Shaughnessy Number): 034001
Empirical Formula: C16H15C13°2
Molecular Weight: 345.7
Year of initial registration: 1948
Pesticide type: Insecticide/Acaricide
Chemical family: Chlorinated Hydrocarbon
U.S. Registrants: Chemical Formulators; Prentiss Drug &
Chemical Co., J.R. Simplot Co.;
Dynachem Industries; Clover Chemical
Co.; Drexel Chemical Co.; Kincaid
Enterprises; and Wesley Industries
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Enterprises; and Wesley Industries
2. USE PATTERNS AND FORMULATIONS
Registered
Uses:
TERRESTRIAL FOOD CROP use: (1) seed treatment only use
on grains and various vegetables; (2) foliar application
(including seed treatment) use on vegetables and fruits;
and (3) foliar application only use on vegetables and
fruits
TERRESTRIAL NON-FOOD CROP use on grasses, ornamentals and
trees
GREENHOUSE FOOD CROP use on mushrooms
DOMESTIC AND NON-DOMESTIC OUTDOOR use around dwellings
and for garbage and sewer areas, general urban outdoor
use
AQUATIC FOOD use on cranberry
AQUATIC NON-FOOD use for mosquito larvae control in
aquatic sites, such as beaches, lakes, marshes and
rivers
FORESTRY use on forest trees
INDOOR use on: (1) postharvest stored grain commodity
and premise treatment; (2) direct animal treatment for
dogs, cats, and farm animals; (3) agricultural premise
use; (4) kennelst dug sleeping quarters and cat sleeping
quarters; (5) indoor domestic dwellings for use on
household contents such as human clothing (including
woolens); (6) direct application to humans; (7)
commercial and industrial use in food processing, storage
transportation areas and equipment
Pests Controlled: various nuisance species (some of public
health significance) including cockroaches,
mosquitoes, flies and chiggers; various
arthropods attacking field crops,
vegetables, fruits, ornamentals, stored
grain, livestock and domestic pets
Methods of Application: sprays, fogs, paints,
ground and aerial equipment,
animal dust-bags, dips, sprays
and back-rubbers
Formulations: Wettable powders, dusts, emulsifiable
2
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concentrates, flowable concentrates„
liquid soluble concentrates, granules,
ready-to-use products (liquids) and
pressurized liquids
3. SCIENCE FINDINGS
Summary Science Statement
With the-exception of one mutagenicity study, there are n;
acceptable acute, subchronic, or long-term
toxicology/oncogenicity studies available to support technical
methoxychlor. In the acceptable mutagenicity study, an
unscheduled DNA synthesis assay in mammalian cells in cult-ire, no
abnormal DNA synthesis was noted at any of the dose levels
tested.
Based on acceptable laboratory data, technical methoxycn ;.ur
is characterized as very highly toxic to fish and aquatic
invertebrates, and practically nontoxic to birds and bees. Hase-'i
on theoretical calculations, both terrestrial and aquatic use'; oi
methoxychlor may pose a hazard to aquatic organisms, although
there is no field evidence to support this. The impacts oi
methoxychlor use to nontarget organisms will be assessed upon
receipt of ecological effects and environmental fate data,
The environmental fate of methoxychlor cannot be
characterized because acceptable data are lacking. Prelimi*)^.y
data suggest that methoxychlor is unlikely to contaminate
groundwater because of its low solubility and high rate of
adsorption to soil particles.
The nature of the residues of methoxychlor in plants and
animals is not adequately understood. None of the tclerar-c-
for methoxychlor is adequately supported. Plant and angina1
metabolism studies, residue studies, analytical methorlo ;oy^
processing studies, and storage stability data are needed be -co
the Agency can determine the adequacy of current tolerance-
levels.
Chemical/Physical Characteristics of the Technical M.F.-;,e:±j±)_
Chemical/Physical
Characteristics:
Color: Data Gap
Physical State: Crystalline solid (>?c.rir«
Chemicals, 1987)
Odor: Data Gap
Melting Point: 89 °C (Farm Chemicals,,
1987)
Specific Gravity: Data Gap
Solubility: Very soluble in aromatic-
chlorinated, or ketonic i e < v.->
-------
somewhat soluble in paraffinic
types; essentially insoluble
in water (Farm Chemicals, 1987)
Vapor Pressure: Data Gap
Flammability: Data Gap
pH: Data Gap
Toxicology Characteristics
With the exception of one mutagenicity study, there are no
acceptable acute, subchronic or long-term toxicology/oncogenicity
studies available to support technical methoxychlor. In the
mutagenicity study, a mammalian cell in culture unscheduled DMA
synthesis assay (UDS assay), no increase in abnormal DNA
synthesis was noted.
Environmental Characteristics
The Agency is unable to assess the environmental fate of
methoxychlor because acceptable data are lacking. Preliminary
data indicate that methoxychlor is stable to hydrolysis (half-
life > 200 days); photodegradation in water (half-life of 4.5
months); and aerobic soil metabolism (half-life > 3 months in
sandy loam soil). The half-life for anaerobic soil metabolism is
reported at less than 1 month in sandy loam soil. Preliminary
data also indicate that methoxychlor has a high adsorption rate
to soil sediment (Kd value is 620).
Ecological Characteristics
Based on acceptable laboratory data, technical methoxychlor
is characterized as practically nontoxic to birds on both an
acute oral and subacute dietary basis and very highly toxic to
fish and aquatic invertebrates on an acute basis. There is
sufficient information to characterize methoxychlor as
relatively nontoxic to honey bees. The acute toxicity value = 24
ug/bee.
- Acute LD50 (bobwhite):
>2510 mg/kg
- Dietary LC50
>5620 ppm (upland gamebird)
- Freshwater invertebrates toxicity (96-hr LC50) for
daphnid .78 ppb
- Fish acute toxicity (96-hr LC50) for rainbow trout:
1.31 ppm
- Fish acute toxicity (96-hr LC50) for brook trout:
0.009 ppm
Tolerance Assessment
Tolerances have been established for residues of
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methoxychlor in a variety of raw agricultural commodities, in
meat, fat and meat byproducts (40 CFR 180.120). Tolerances are
expressed in terms of methoxychlor per se.
The nature of the residues of methoxychlor in plants and
animals is not adequately understood. None of the tolerances
for methoxychlor is adequately supported. Plant and animal
metabolism studies, residue studies, analytical methodology,
processing studies, and storage stability data are needed before
the Agency can determine the adequacy of current tolerance
levels.
The Preliminary Limiting Dose (PLD) of methoxychlor is .005
mg/kg/day. This is based on a rabbit teratology study with a No
Observed Effect Level (NOEL) of 5 mg/kg/day for increased loss
of litters and an uncertainty factor of 1000 to account for
inter- and intraspecies differences, poor quality of the study
used and total incompleteness of the subchronic and chronic
toxicity data base. The study is not considered to be adequate
to define a NOEL for purposes of setting an Acceptable Daily
Intake, since the experimental design was considered to be
inadequate. It is being used on an interim basis for calculation
of the PLD. The Agency is unable to complete a tolerance
assessment of methoxychlor because of the incompleteness of the
toxicology and residue chemistry data bases.
4. SUMMARY OF REGULATORY POSITIONS AND RATIONALES
Methoxychlor is not being placed into Special Review at
this time. Since there are so few acceptable studies available
to support registration of products containing methoxychlor, the
Agency is not yet able to make a determination as to whether any
of the criteria of 40 CFR 154.7 have been met or exceeded.
The Agency will not approve any new food uses, including
minor uses for this chemical since none of the tolerances are
adequately supported.
- The Agency is unable to assess methoxychlor's potential for
contaminating groundwater. When data required in the Standard
have been received and evaluated, the Agency will assess the
potential for methoxychlor to contaminate groundwater.
- Updated worker safety rules are required for end-use product
labels.
-The Agency is not establishing a longer reentry interval lot
agricultural uses of methoxychlor beyond the minimum reentry
interval (sprays have dried, dusts have settled, and vapors have
dispersed).
- Revised and updated fish and wildlife statements ar^
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required for end-use product labels. Since methoxychlor is
practically nontoxic to bees, the bee statement imposed under
under PR Notice 68-19 is no longer appropriate. Registrants must
remove the bee statement from the labeling.
- The Agency is not classifying methoxychlor as a restricted
use pesticide at this time, since it is unable to determine if
this pesticide meets any of the risk criteria of 40 CFR 152.170.
Upon receipt of data required under this Standard, the Agency
will apply the criteria of 40 CFR 152.170 to determine if any
uses of methoxychlor warrant restricted use classification.
- Since methoxychlor is an analogue of DDT, the Agency is
requiring specific analysis of methoxychlor for the potential
impurities 1,1,l-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT)
and other structurally similar compounds.
SUMMARY OF OUTSTANDING DATA REQUIREMENTS
Toxicology
Acute Oral Toxicity
Acute Dermal Toxicity
Acute Inhalation Toxicity
Eye Irritation
Dermal Irritation
Dermal Sensitization
21-Day Dermal Toxicity
Chronic Testing (rodent)
Chronic Testing (non-rodent)
Oncogenicity (rat)
Oncogenicity (mouse)
Teratogenicity (rat)
Teratogenicity (rabbit)
Reproduction
Gene Mutation
Other Mechanisms of
Mutagenicity
Metabolism
Time Frame
9 Months
9 Months
9 "
9 "
9 "
9 "
9 "
50 "
50 "
50 "
50 "
15 "
15 "
39 "
9 "
12 "
24 "
Environmental Fate/Exposure
Hydrolysis
Photodegradation in Water
Photodegradation on Soil
Aerobic Soil Metabolism
Anaerobic Soil Metabolism
Anaerobic Aquatic Metabolism
Aerobic Aquatic Metabolism
Leaching and Adsorption/
Desorption
9 Months
9 "
9 "
27 "
27 "
27 "
27 "
12 "
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Aquatic Dissipation
Forestry
Soil, Long-term
Confined Rotational Crop
Accumulation in Irrigated Crops
Accumulation in Fish
Accumulation in Aquatic
Nontarget Organisms
Fish and Wildlife
Avian Reproduction
Freshwater Fish LC5Q Studies (TEP)
Freshwater Invertebrate LC5Q Studies (TEP)
Estuarine and Marine
Organisms LC5Q Studies (TEP)
Fish Early Life Stage
and Invertebrate Life Cycle
Simulated or Actual Field
Testing-Aquatic Organisms
Seed Germination/Seedling
Emergence
Aquatic Plant Growth
Residue Chemistry
Residue data - Raw Agricultural Commodities
Processing Studies
Plant and Animal Metabolism
Storage Stability
Residue Analytical Methods
Product Chemistry
All Data
27 "
27 "
39 "
39 "
39 "
12 "
12 "
24 Months
9 "
9 "
12 "
15 "
24 "
9 "
9 "
18 Months
24 "
18 "
15 "
15 "
9 -15 Months
6. Contact Person at EPA
Dennis H. Edwards Jr.
Product Manager (12)
Insecticide-Rodenticide Branch
Registration Division (TS-767)
Environmental Protection Agency
Washington, DC 20460
Tel. No. (703) 557-2386
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DISCLAIMER: The information presented in this Chemical
Information Fact Sheet is a summary only and may not be used to |
fulfill data requirements for pesticide registration and "
reregistration.
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&EPA
U.S. Environmental Protection Agency
Office of Pesticide Program (TS-757C)
PMSD, Information Services Branch
401 M Street, S.W.
Washington, D.C. 20460
Official Business
Penalty for Private Use $300
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