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Fact Sheet
Name of Chemical: PARATHION
Reason for Issuance: ISSUANCE OF GUIDANCE DOCUMENT
Date Issued: 12/1986
Fact Sheet Number: 116
DESCRIPTION OF CHEMICAL
Generic Name: O,O-diethyl-O-p-nitrophenyl phosphorothioate
Common Name: Parathion
Trade Names Alkron, Aileron, Aphamite, Bladan, Corothion,
and other Ethyl Parathion, Folidol E-605, Fosferno 50,
names: Niran, Orthophos, Panthion, Paramar, Paraphos,
Parathene, Parawet, Phoskil, Rhodiatox, Sopra-
thion, Stathion, Thiophos
EPA Shaughnessy Code: 057501
Chemical Abstracts Service (CAS) Number: 56-38-2
Year of Initial Registration: 1948
Pesticide Type: Insecticide
Chemical Family: Organophosphate
U.S. and Foreign Producers: Monsanto U.S.A.; Bayer A.G., West
Germany; and Cheminova, Denmark
USE PATTERNS AND FORMULATIONS
Application Sites: Vegetable crops, field crops orchard crops
ornamentals, aquatic crop and non-crop
sites
Types of Formulations: Emulsifiable concentrates, granulars,
dusts, baits, wettable powders and
impregnated materials.
Types of Methods of Application: Ground applications; broadcast,
band, and aerial application
Application Rates: 0.1 to 10.0 Ibs/active ingredient per acre
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Usual Carriers: petrb1 eum sb].vents, clay carriers
3. SCIENCE FINDINGS
Summary Science Statement
Parathion is a Toxicity Category I organophosphate compound
which is extremely toxic to laboratory mammals.
The chemical has demonstrated adverse chronic effects
such as tumors in the adrenal glands, retinal atrophy
and degeneration, and degeneration of the sciatic nerve.
The Agency has carried out a weight-of-the—evidence analysis
and has concluded that parathion is a Category C oncogen
(possible human carcinogen). Parathion was not shown to
be teratogenic. Parathion is extremely toxic to fish and
birds. Parathion is entering the Special Review process
because of acute effects to both humans and birds. Human
poisoning from parathion exposure have occurred during
mixing/loading, application, early reentry into treated
fields, equipment repair and hanling, and contact with
spray drift.
Chemical Characteristics of the Technical Material
Physical State: Liquid
Color: Dark Brown
Odor: Garlic—like
Molecular weight and formula: 291.26 — C 10 H 14 N0 5 PS
Boiling point: 157-162 at 0.6 mm Hg
Vapor Pressure: 0.42 u hg at 25’ C (pure active ingredient)
Solubility in various solvents: Miscible in most all organic
solvents and oils, only
slightly soluble in water
Toxicoloqy Characteristics
Acute toxicity: Parathion is extremely toxic to mammals by
all routes of exposure and is classified in Toxicity Category
I (1.75- 15.0 mg/kg). Additional acute toxicity tests have
been waived because they would not alter this classification.
Major routes of exposure: Inhalation and dermal.
Delayed neurotoxicity: Data gap- To be filled via the published
literature.
Oncogenicity: This chemical is classified as a Category C
oncogen.
Chronic Effects: Retinal degeneration and sciatic nerve
degeneration in life-time feeding studies
in the rat.
Metabolism: Data gap.
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Chronic Effects: RetThal and sciatic nerve damage at high
dose levels was observed in the rat.
Cho1ine terase inhibition.
Teratogenicity: Parathion was not teratogenic at levels up
to 1.5 and 16 mg/kg in the rat and rabbit,
respectively
Reproduction: Data gap
Mutagenicity: Positive for induction of DNA repair in
Unscheduled DNA Synthesis (UDS) assay in
a human cells study. Additional genotoxicity
studies are required to determine the mutagenic
potential of parathion.
Physiological and Biochemical Characteristics
Mechanism of pesticidal action: This insecticide is active
by contact, ingestion, and vapor action. Parathion in humans
acts by causing irreversible inhibition of cholinesterase
enzyme, allowing accumulation of acetyicholine at cholinergic
neuroeffector junctions and autonomic ganglia. Poisoning
also impairs the central nervous system function. Symptoms
of poisoning include headaches, nausea, vomiting, cramps,
weakness, blurred vision, pin-point pupils, tightness in
chest, labored breathing, nervousness, sweating, watering of
eyes, drooling or frothing of mouth and nose, muscle spasms,
coma and death.
Environmental Characteristics
Available data provide insufficient information for the
analysis of the environmental fate of parathion.
Parathion has little or no potential to contaminate
ground water. This chemical was not included on the list
of potential ground water contaminaters.
Ecological Characteristics
Aviari oral toxicity: 1.3 mg/kg for house sparrows and pigeons
Avian dietary toxicity: 76 to 336 ppm for mallard and ring-
necked pheasant, respectively
Avian reproduction: Data gap
Freshwater fish acute toxicity: 0.32 to 2.65 ppm for
mosquitofish and channel
catfish, respectively
Aquatic freshwater invertebrate toxicity: 0.04 to 5 ppb for
most species
Marine and estuarine toxicity: 1.0 (48—hr) to 17.8 (96—hr) ppb
for brown shrimp and striped
bass, respectively
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Endangered Species: Previous consultations with the Office
of Endangered Species have resulted in jeopardy opinions and
labeling for crops (alfalfa, apples, barley, corn, cotton,
pears, and wheat), rangeland and pastureland, silvacultural
sites, aquatic sites, and noncropland use. Labeling is being
imposed to reduce the risk to endangered species.
4. Summary of Requlatory Position and Rationale
A. The Agency anticipates initiating a Special Review based
upon its adverse acute effects to both humans and birds.
B. The Agency is requiring avian reproduction and terrestrial
full field testing and simulated or full field aquatic
testing to better define the extent of exposure and
hazard to wildlife.
C. No new tolerances or new food uses will be considered
until the Agency has received data sufficient to
assess existing tolerances for parathion.
D. The Agency is concerned about the potential for human
poisonings (cholinesterase inhibition) from the use of
parathion. The Agency will continue to classify
for restricted use (due to very high acute toxicity
to humans and birds). The Certified applicator must be
physically present during mixing, loading, equipment
repair, and equipment cleaning . Information from the
California Department of Food and Agriculture reported
incidents of worker poisonings and illnesses during mixing,
loading, and application. EPA is requiring more stringent
“Worker Safety Rules”, including protective clothing, to
reduce exposure.
E. A reentry interval of 7 days is required for apple, citrus,
peach, nectarine and grapes in the states of Arizona,
California, Nevada, New Mexico, Oklahoma, Texas and Utah.
A 48-hour reentry interval will remain on other crops and
the crops listed above in all other states.
F. The Agency has classified parathion as a class C oncogen.
5. Required Unique Labeling Summary
All manufacturing-use and end-use parathion products must bear
appropriate labeling as specified in 40 CFR 162.10. In
addition, the following information must appear on the labeling:
All parathion products will continue to be classified for
restricted use and the restricted use label will specify
the reason (High acute toxicity to humans and birds).
A reentry interval of 7 days is required for apple, citrus,
peach, nectarine and grapes in the states of Arizona,
California, Nevada, New Mexico, Oklahoma, Texas and Utah.
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A 48-hour reentry •intervak will remain on other crops and
the crops listed above in all other states.
Additional labeling requirements are imposed to protect
fish, birds and other wildlife, including endangered species.
Effluent containing parathion may not be discharged
into lakes, streams, ponds, estuaries, oceans or public
waters unless this product is specifically identified in an
NPDES permit. Discharge of effluent containing this product
is forbidden without prior notice to the sewage treatment
plant authority.
Protective clothing requirements are being standardized to
protect applicators, fieldworkers and mixer/loaders.
Human flaggers are prohibited during aerial application.
6. Tolerance Assessment
U.S., Canadian, Mexican, and Codex tolerances for negligible
residues parathion in or on raw agricultural commodities can
be reviewed on attachment I. U.S. parathion tolerances can
also be found in 40 CFR 140.121.
Because of extensive data gaps in residue chemistry and
toxicology areas, a tolerance assessment can not be made at
this time. Plant and animal xnetabolites are required to
be identified and their toxicological significance determined.
Storage stability data are required, so some of the present
tolerances may be affected. Sufficient data are available
to ascertain the adequacy of the established tolerances for
residues of parathion in or on the following raw agricul-
tural commodities (RACs): beans (dried only), peas (dried
and succulent), soybeans, mustard seed, safflower seed,
sugarcane, and sugarcane forage.
There are no tolerances for residues of parathion in animal
products. On receipt of the requested plant and animal
metabolism data, the need for these tolerances will be de-
termined.
Parathion’s Acceptable Daily Intake (ADI) is 0.005 mg/kg/day,
based on rat cholinesterase inhibition. The TMRC currently
utilizes 192% of the ADI. Recent chronic feeding studies
in rats strongly suggest that the present no effect level
(NOEL) is not adequate and a new lower NOEL is needed.
Additional data are required in order for the Agency to
determine an adequate NOEL and ADI.
7. SUMMARY OF MAJOR DATA GAPS
Animal and plant metabolism data
Magnitude of the residues in various crops
Full battery of Environmental Fate data
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Additional subchronic toxicity testing to determine a NOEL
for cholinesterase inhibition and other systemic effects
(retinal degeneration, sciatic nerve, abnormal gait)
Reproduction studies
Gene Mutation studies
Reentry studies
Avian reproduction and simulated field testing
Acute toxicity to fresh water, estuarine and marine
organisms
Early life stage and fish life cycle studies
Aquatic accumulation studies
Glove permeability and drift studies
Applicator Monitoring studies
7. CONTACT PERSON AT EPA
Dennis Edwards
Acting Product Manager (12)
Insecticide-Rodentjcjde 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
reregistration.
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ATFAG1ME T I
Summary of Present Parathion Tolerances
To rances (pgip) (MRL)
Commodity United States—’ - Canada— 1 - Mexico— 1 - Internationaib
( Codex ) -
Garden Beets 1.0 0.7 —-- 0.7
Carrots 1.0 0.7
*parsfljp s 1.0 0.7 ——— 0.7
Potatoes 0.1 —-- 0.1 0.7
Radishes 1.0 0.7 1.0 0.7
Rutabagas 1.0 --- —-- 0.7
Sugar Beets 0.1
Sweet Potatoes 0.1 --- 0.1 0.7
Turnips 1.0 0.7 ——- 0.7
Garlic 1.0 ——— 1.0 0.7
Onions 1.0 0.7 1.0 0.7
Celery 1.0 0.7 1.0 0.7
Endive 1.0 0.7 ——— 0.7
Lettuce 1.0 0.7 1.0 0.7
Spinach 1.0 0.7 1.0 0.7
Swiss Chard 1.0 0.7 —-- 0.7
Broccoli 1.0 0.7 1.0 0.7
Brussels Sprouts 1.0 0..7 —-- 0.7
Cabbage 1.0 0.7 —-- 0.7
Cauliflower 1.0 0.7 ——— 0.7
Collards 1.0 ——— ——— 0.7
Kale 1.0 0.7 ——— 0.7
Kohirabi 1.0 0.7 0.7
Mustard Greens 1.0 —-- 0.7
Beans 1.0 0.7 1.0 0.7
Peas 1.0 0,7 1.0 0.7
Soybeans 0.1 ——- 0.1
Eggplant 1.0 0.7 1.0 0.7
Peppers 1.0 0.7 1.0 0.7
Tomatoes 1.0 0.7 1.0 0.7
Cucumbers 1.0 0.7 1.0 0.7
Melons 1.0 1.0 1.0 0.5
Pumpkins 1.0 0.7 ——— 0.5
Squash 1.0 0.7 ——— 0.7
Citrus Fruits 1.0 1.0 1.0 1.0
Apples 1.0 1.0 1.0 0.5
Pears 1.0 1.0 1.0 0.5
Quince 1.0 1.0 —-- 0.5
Apricots 1.0 1.0 —-— 1.0
Cherries 1.0 1.0 -—— 0.5
Nectarines 1.0 ——- —-- 0.5
Peaches 1.0 1.0 1.0 1.0
Plums 1.0 1.0 ——— 0.5
Blackberries 1.0 --- 0.5
Blueberries 1.0 ——— ——— 0.5
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Summary of Present Parathion Tolerances (con’t)
To çrances (MRL)
Commodity United Sta€ sa Canada—’- Mexico—’- Internationaib
Codex)- 1
Boysenberries 1.0 --- --- 0.5
Cranberries 1.0 1.0 —-- 0.5
Currants 1.0 ——— ——- 0.5
Dewberries 1.0 —-— —-- 0.5
Gooseberries 1.0 1.0 0.5
Grapes 1.0 1.0 ——— 0.5
Loganberries 1.0 1.0 —-- 0.5
Raspberries 1.0 1.0 —-- 0.5
Strawberries 1.0 1.0 1.0 0.5
*Voungberries 1.0 --— --- 0.5
Almonds 0.1 --— 0.1
Filberts 0.1 --- 0.1
Pecans 0.1 -—— 0.1
Walnuts 0.1 ——— 0.1
Barley 1.0
Corn 1.0 0.7 1.0
Oats 1.0
Rice 1.0
Sorghum 0.1 0.1
Wheat 1.0
Forage Grass 1.0
Alfalfa Forage 1.25 5.0
Alfalfa I-lay 5.0 1.25
Clover Forage & Hay 1.0
Vetch Forage & Hay 1.0
Miscellaneous Crops
Artichokes 1.0 1.0 0.7
Avocados 1.0 1.0 0.5
Cottonseed 0.75 0.75
Dates 1.0 --- 0.5
Figs 1.0 1.0 0.5
*Guavas 1.0 1.0 0.5
Hops 1.0 1.0
Mangos 1.0 1.0 0.5
Mustard Seed 0.2
Okra 1.0 1.0 0.7
Olives 1.0 ——— 0.5
Peanuts 1.0 1.0
Pineapples 1.0 1.0 0.5
Rape Seed 0.2
Sugarcane 0.1 0.1
Sunflower Seed 0.2
a/ The U.S., Canadian, and Mexican tolerances are expressed in terms of
residues of parathion per Se.
b/ The Codex Maximum Residue Levels are expressed as residues of parathion
and its oxygen analog, paraoxon.
I * Although these crops have tolerance there are no EPA registered uses.
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