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Chlorpyrifos - Chemical Fact Sheet 9/84

                           CHEMICAL FACT SHEET FOR:
                                 CHLORPYRIFOS

FACT SHEET NUMBER:  37

DATE ISSUED:  SEPTEMBER 30, 1984

                      1. DESCRIPTION OF CHEMICAL

- Generic Name:  O,O-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
  Shiva, All India Medical Corp., Planters Products, Inc.

                    2. 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, bee' cattle, sheep and dogs,
  livestock premise treatment, domestic dwellings, terrestrial
  structures, and direct application to stagnant water, etc.
- Types of formulations:  Baits, dusts, granules, wettable powders,
  flowables, impregnated plastics, and pressurized liquids.
- Types and methods of application: Ground and aerial, sprays and dust
  applications
- Application rates:  Range from 0.5 lbs. a.i./A to 3 lbs. a.i./A, and
  crack and crevice treatment to broadcast treatment for indoor uses.
- Usual carriers: Synthetic clays, talc, various solvents

                         3. SCIENCE FINDINGS

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 10-5 mm Hg at 20 C
- Flash point:  none

- Toxicological 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 neurotoxic 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 determine 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 demonstrate 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-pyridinal (TCP). The
  parent compound and metabolite are rapidly excreted 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 acetylcholinesterase enzyme of tissues,
  allowing accumulation of acetylcholine 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 heartbeat,
  pulmonary edema, and sweating. Continual absorption at intermediate
  dosages may cause influenza-like illness which includes symptoms like
  weakness, anorexia, and malaise.
- The metabolism of chlorpyrifos in plants and animals is not adequately
  understood. The major metabolite is 3,5,6-trichloro-2pyridinol (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 environmental fate
  of chlorpyrifos. 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 pheasant --17.7
  mg/kg
- Avian dietary:  Mallard duck -- 136 ppm; Bobwhite quail -- 721 ppm
- Freshwater fish:  Coldwater fish (rainbow trout) -- 3.0 ppm; Warmwater
  fish (bluegill sunfish) -- 2.4 ppm
- Acute freshwater invertebrates:  Daphnia -- 0.176 ppb
- Acute estuarine and marine organisms:  Oyster -- 0.27 ppm; Grass
  shrimp -- 1.5 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.

Tolerance Assessment

- The Agency is unable to complete a full tolerance reassessment 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 (including 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
Horses, meat....................................1.0
Milk, fat (reflecting 0.02 ppm.in whole milk)...0.5
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 (including turkeys)................0.5
Poultry, mbyp (including turkeys)...............0.5
Poultry, meat (including 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 chlorpyrifos residues in the human diet is
  calculated to be 0.5637 mg/day. The acceptable daily intake (ADI) of
  chlorpyrifos 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 chlorpyrifos and tolerances
  established by the Codex Alimentarius, Canada and Mexico, the
  expression of the U.S. tolerances for chlorpyrifos would have to
  exclude the major metabolite TCP, but the Agency is not recommending
  this now.
- U.S. tolerances for most raw agricultural commodities are supported
  by current residue chemistry data.  In some cases, however, more
  data are required.

Summary Science Statement

- Chlorpyrifos 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 fish, birds, and other wildlife. It
  is highly toxic to honeybees. 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 fat 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.

          4.  SUMMARY OF REGULATORY POSITION AND RATIONALE

- The Agency has determined that it should continue to allow the
  registration of chlorpyrifos. Adequate studies are available to assess
  the acute toxicological effects of chlorpyrifos to humans. None of the
  criteria for unreasonable 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 chlorpyrifos 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 environmental 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, oncogenicity, 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
  - Photodegradation studies
  - Soil metabolism studies
  - Mobility studies
  - Dissipation studies
  - 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, DC 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 NOT TO BE USED TO FULFILL
DATA REQUIREMENTS FOR PESTICIDE REGISTRATION AND REREGISTRATION.