United Statai Office of Pwtlctdat end Toxic Sutatances
Environmental Protection Office of Pesticide Programs (TS-766CI
Agency Washington, DC 20460
v>EPA Pesticide
Fact Sheet
Name of Chemical: CHLORPYRIFOS
Reason for Issuance:
Date Issued: September 30, 1984
Fact Sheet Number: 37
DESCRIPTION OF CHEMICAL
Generic Name: 0,0-diethyl 0-(3,5,6-trichloro-2-pyridyl)
phosphorothioate
Common Name: Chlorpyrifos
Trade Name: Dursban for household products, Lorsban for
agricultural products
EPA Shaughnessy Code: 059101
Chemical Abstracts Service (CAS) Number: 2921-88-2
Year of Initial Registration: 1965
Pesticide Type: Insecticide
Chemical Family: Organophosphate
U.S. and Foreign Producers: Dow Chemical U.S.A.
Makhteshim-Beer Shviva
All India Medical Corp
Planters Products, Inc.
USE PATTERNS AND FORMULATIONS
Application Sites: Grain crops, nut crops, bananas, cole
crops, citrus, pome and strawberry
fruits, forage, field and vegetable crops,
lawns and ornamental plants, poultry,
beef cattle, sheep and dogs, livestock
premise treatment, domestic dwellings,
terrestrial structures, and direct ap-
lication to stagnant water etc.
Types of Formulations: Baits, dusts, granules, wettable
powders, flowables, impregnated
plastics and pressurized liquids.
Types of Methods of Application: Ground and aerial, sprays
and dust applications
Application Rates: Range from 0.5 Ibs. a.i./A to 3 Ibs.
a.i./A and crack and crevice treatment
to broadcast treatment for indoor uses.
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Usual Carriers: Synthetic clays, talc, various solvents
3. SCIENCEYINDINGS
Summary Science Statement
Chiorpyrifos has moderate mammalian toxicity. It is not
considered to be oncogenic, mutagenic or teratogenic.
However, the oncogenicity and mutagenicity studies used to
draw these conclusions are not up to current Agency standards.
Additional information from these studies is required.
The Agency is imposing a 24—hour reentry restriction for crop
uses until appropriate reentry studies are submitted and
evaluated and a decision is reached whether a different time
interval is more appropriate. The 24—hour interval also
coincides with the requirements of California.
Data are insufficient to fully assess the environmental fate
of chlorpyrifos. The Agency is requesting necessary data
to make this assessment and also to specifically assess
whether or not chlorpyrifos has a potential to leach into
groundwater. Data are also insufficient to measure human
exposure in outdoor and indoor applications.
Chlorpyrifos is extremely toxic to tish, birds and other
wildlife. It is highly toxic to honey bees. Use precautions
and restrictions are being imposed to reduce potential hazards.
A full tolerance reassessment cannot be completed. The
previous ADI (at 94% of the TMRC) was established based on a
2—year rat feeding study. The present ADI (313% of the TMRC)
was calculated using a human study. Chronic feeding studies
are required as well as metabolism and residue data on numerous
commodities.
Chemical Characteristics
Physical State: Crystalline solid
Color: White to tan
Odor: Mild mercaptan
Melting point: 41.5—43.5 °C
Vapor Pressure: 1.87 x lO mm Hg at 20°C
Flash Point: None
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Toxicology Characteristics
Acute Oral: 163 mg/kg, Toxicity Category II
Acute Dermal: 1505 mg/kg, Toxicity Category II
Primary Dermal Irritation: No irritation, Toxicity
Category III
Primary Eye Irritation: Conjunctival irritation at 24 hours.
Cleared at 48 hours. Toxicity Category III
Acute Inhalation: Data gap
Neurotoxicity: Not an acute delayed rieurotoxic agent at
doses up to 100 mg/kg (highest dose tested).
Oncogenicity: Two studies submitted but neither meet Agency
standards. Neither suggest oncogenicity potential.
Teratogenicity: Three studies have been evaluated to deter-
mine the teratogenic potential of chlorpyrifos. The Agency
has determined that this chemical is not teratogenic at
levels up to 25 mg/kg/day.
Reproduction—2 generation: Two studies adequately demon-
strate that chlorpyrifos does not produce reproductive effects.
No effects were demonstrated at dose levels up to 1.2 mg/kg/day.
Metabolism: The submitted studies suggest that chlorpyrifos
is rapidly absorbed and metabolized to 3,5,6—trichloro—2—pyri=
dinal (TCP). The parent compound and metabolite are rapidly
excreated in the urine. The submitted studies do not meet
Agency standards.
Mutagenicity: Data Gap
Physiological and Biochemical Behavioral Characteristics
Mechanism of Pesticidal Action: An insecticide which is
active by contact, ingestion, and vapor action and almost
irreversibly causes phosphorylation of the acetylcholin—
esterase enzyme of tissues, allowing accumulation of acetyl—
chloline at cholinergic neuroeffector junctions (muscarinic
effects), and at skeletal muscle myoneural junctions and
autonomic ganglia. Poisoning also impairs the central nervous
system function.
Symptoms of poisoning include: headache, dizziness, extreme
weakness, ataxia, tiny pupils, twitching, tremor, nausea,
slow heatbeat, pulmonary edema, and sweating. Continual
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absorbtion at intermediate dosages may cause influenza—like
illness which includes symptoms like weakness, anorexia, and
malaise.
Metabolism and Persistence in Plants and Animals :
The metabolism of chiorpyrifos in plants and animals is
not adequately understood. The major metabolite is 3,5,6—
trichloro—2—pyridinol (TCP). The Agency does not have
adequate data on TCP to determine if this metabolite should
continue to be a part of the tolerance expression.
Environmental Characteristics
Available data are insufficient to fully assess the environ-
mental fate of chiorpyrifos. Data gaps exist on all required
studies except for aerobic and anaerobic soil studies.
Adsorption and Leaching in Basic Soil Types: The Agency is
requesting data to determine if chlorpyrifos will contaminate
groundwater.
Microbial Breakdown: Depending on the soil type, microbial
metabolism of chlorpyrifos may have a half—life of up to 279
days.
Ecological Characteristics
Avian oral:
Mallard duck——76.6 mg/kg
Ring necked pheasarit——17.7 mg/kg
Avian dietary:
Mallard duck——136 ppm
Bobwhite quail——721 ppm
Freshwater Fish:
Coldwater fish (rainbow trout)——3.O ppm
Warmwater fish (bluegill sunfish)——2.4 ppm
Acute Freshwater Invertebrates:
Daphnia——O.176 ppb
Acute Estuarine and Marine Organisms:
Oyster——O.27 ppm
Grass shrimp——l.5 ppm
Killifish——3.2 ppm
Precautionary language is being required for hazards to birds,
fish, and aquatic organisms. Chronic effects to non—target
aquatic invertebrate species are not adequately characterized
and therefore appropriate studies are required.
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Tolerance Assessment
The Agency is unable to complete a full tolerance reassess-
ment because of certain residue chemistry and toxicology
data gaps.
Tolerances:
Commodity Parts Per Million
Alfalfa, green forage 4.0
Alfalfa, hay 15.5
Almonds 0.05
Almonds, hull 0.05
Apples 1.5
Bananas (whole) 0.25
Bananas, pulp with peel removed 0.05
Bean forage 1.0
Beans, lima 0.05
Beans, lima, forage 1
Beans, snap 0.05
Beans, snap, forage 1
Beets, sugar, roots 1.0
Beets, sugar, tops 8.0
Broccoli 2
Brussels sprouts 2
Cabbage 2
Cattle, fat 2.0
Cattle, meat by—products (mbyp) 2.0
Cattle, meat 2.0
Cauliflower 2
Cherries 2.0
Citrus fruits 1.0
Corn, field, grain 0.1
Corn, fresh (inc. sweet corn; kernel 0.1
plus cob with husk removed)
Corn, fodder 10.0
Corn, forage 10.0
Cottonseed 0.5
Cranberries 1.0
Cucumbers 0.1
Eggs 0.1
Figs 0.1
Goats, fat 1.0
Goats, mbyp 1.0
Goats, meat 1.0
Grapes 0.5
Hogs, fat 0.5
Hogs, mbyp 0.5
Hogs, meat 0.5
Horses, fat 1.0
Horses, mbyp 1.0
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Tolerances (con’t)
Commodity Parts Per Million
Horses, meat 1.0
Milk, fat (reflecting 0.02 ppm 0.5
in whole milk)
Mint, hay 1.0
Nectarines 0.05
Onions (dry bulb) 0.5
Pea forage 1.0
Peaches 0.05
Peanuts 0.5
Peanut hulls 15
Pears 0.05
Peppers 1.0
Plums (fresh prunes) 0.05
Poultry, fat (inc turkeys) 0.5
Poultry, mbyp (inc turkeys) 0.5
Poultry, meat (inc turkeys) 0.5
Pumpkins 0.1
Radishes 3
Seed and pod vegetables 0.1
Sheep, fat 1.0
Sheep, mbyp 1.0
Sheep, meat 1.0
Sorghum, fodder 6
Sorghum, forage 1.5
Sorghum, grain 0.75
Soybeans 0.5
Soybeans, forage 8.0
Soybeans, straw 15.0
Strawberries 0.5
Sunflower, seeds 0.25
Sweet potatoes 0.1
Tomatoes 0.5
Turnips (roots) 3
Turnips (greens) 1
Based on established tolerances the theoretical maximum
residue contribution (TMRC) for chiorpyrifos residues in the
human diet is calculated to be 0.5637 mg/day. The acceptable
daily intake (ADI) of chiorpyrifos is 0.003 mg/kg/day. The
maximum permissible intake (MPI) is 0.18 mg/day. The percent
utilized ADI is 313%. To provide for conformity between
U.S. tolerances for chiorpyrifos and tolerances established
by the Codex Alimentarius , Canada and Mexico, the expres-
sion of the U.S. tolerances for chiorpyrifos would have to
exclude the major metabolite TCP, but the Agency is not
recommending this now.
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U.S. tolerances for most raw agricultural commodities are
supported by current residue chemistry data. In some cases
however, more data are required.
4. SUMMARY OF REGULATORY POSITION AND RATIONALE
The Agency has determined that it should continue to allow
the registration of chiorpyrifos. Adequate studies are
available to assess the acute toxicological effects of
chiorpyrifos to humans. None of the criteria for unreason-
able adverse effects listed in section 162.11(a) of Title 40
of the U.S. Code of Federal Regulations have been met or
exceeded. However, because of certain gaps in the data base
a full risk assessment of chlorpyrifos cannot be completed.
Also, a full tolerance reassessment cannot be completed
because of certain residue chemistry and toxicology data gaps.
The Agency is concerned whether or not the potential total
human exposure to chiorpyrifos and its metabolites, from its
widespread use and its ADI being exceeded three—fold, poses
any unacceptable hazards. To resolve this concern, additional
residue, metabolism and exposure data are required, and until
it is resolved no significant new tolerances or uses will be
granted.
A federal 24—hour reentry interval is established for treated
crop areas until reentry data are submitted, as required, and
the Agency decides on the most appropriate time interval.
Available data are insufficient to fully assess the environ-
mental fate of chlorpyrifos. The Agency is requesting data
to determine if chlorpyrifos will contaminate groundwater.
5. SUMMARY OF MAJOR DATA GAPS
Additional residue data on various processed commodities are
being required. Also, additional chronic toxicity, oncogen—
icity and mutagenicity testing is needed to better define the
long term effects of this chemical. Plant, animal and exposure
data are required to better qualify and quantify human exposure
to residues from dietary and nondietary sources.
Other requirements:
Acute inhalation
General metabolism
Hydrolysis study
Photodegradat ion studies
Soil metabolism studies
Mobility studies
Dissipation studies
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Other Requirements (con’t)
Accumulation studies
Fish embryo—larvae study
Large scale field testing
Monitoring for crop runoff
Phytotoxic effects on algae and other aquatic plants
Indoor monitoring
6. CONTACT PERSON AT EPA
Jay S. Ellenberger
Product Manager (12)
Insecticide—Rodenticide Branch
Registration Division (TS—767C)
Office of Pesticide Programs
Environmental Protection Agency
401 M Street, S. W.
Washington, D. C. 20460
Office location and telephone number:
Room 202, Crystal Mall #2
1921 Jefferson Davis Highway
Arlington, VA 22202
(703) 557—2386
DISCLAIMER: The information presented in this Chemical Information
Fact Sheet is for informational purposes only and may not be used
to fulfill data requirements for pesticide registration and
rereg istrat ion.
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