Methyl Parathion (Penncap-M) - Chemical Profile 4/85
CHEMICAL name: O,O-dimethyl-O-p-nitrophenyl phosphorothioate (56)
DEC INGRED. CODE:
TRADE name(S): Penncap-M, Metacide (1)
FORMULATION(S): Emulsifiable concentrates, wettable powders, dusts
(56). Special flowable microencapsulated formula-
TYPE: Organophosphate insecticide-miticide
BASIC PRODUCER(S): Monsanto Agr. Prod. Co. Vertac Chemical Corp.
800 N. Lindbergh Blvd. 5100 Poplar
St. Louis, MO 63166 Memphis, TN 38137
STATUS: Restricted use
PRINCIPAL USES: Insects and mites on many crops. Nonsystemic (1).
Used for control of many insects of economic importance, being especially
effective for boll weevil control (56). Used on irrigated pastures as
a mosquito larvicide. Widely used in mosquito abatement programs (8a).
Important Pests Controlled: Aphids, armyworms, flea beetles,
leafhoppers, leafminers, scale, mealy bugs, mites, boll weevils, thrips
and many others. Especially effective on boll weevils (8a).
Fast acting (8a).
II. PHYSICAL PROPERTIES
MOLECULAR FORMULA: C8 H10 NO5 P S (62)
MOLECULAR WEIGHT: 263.2 (62)
PHYSICAL STATE: Colorless crystals (pure compound); light to dark
tan-colored liquid (technical product, c. 80% pure)
MELTING POINT: 35-36 C (pure compound) (62)
VAPOR PRESSURE: 1.3 mPa at 20 C (pure compound) (62)
SOLUBILITY: 55-60 mg/l water at 25 C (pure compound) (62)
III. HEALTH HAZARD INFORMATION
OSHA STANDARD: None established
NIOSH RECOMMENDED LIMIT: None established
ACGIH RECOMMENDED LIMIT: TWA (Time Weighted Average) = 0.2 mg/m3;
STEL (Short Term Exposure Limit) = 0.6
mg/m3 (deleted); skin notation (15c).
A. ACUTE TOXICITY
DERMAL: LD50 = 300-400 mg/kg (rabbit) (56)
LD50 = 67 mg/kg (rat) (62)
ORAL: LD50 = approx. 9-25 mg/kg (rat) (56)
LD50 (rat) = 14 mg/kg (male); 24 mg/kg (female) (62).
B. SUBACUTE AND CHRONIC TOXICITY:
In 2-yr feeding trials NEL for rats was 2 mg/kg diet (62).
Dogs fed methyl parathion for 12 weeks at a rate corresponding to
approximately 7 mg/man/day showed no clinical effect and no significant
change in cholinesterase activity. Four times this dosage produced
some inhibition of erythrocyte but not plasma cholinesterase. A dosage
corresponding to 70 mg/man/day inhibited both erythrocyte and plasma
cholinesterase activity but did not produce illness.
Groups of five men each were given methyl parathion for 30 days at
rates of 7, 7.5, 8 and 9 mg/man/day. Both the erythrocyte and plasma
cholinesterase activity remained within 20 percent of control values
IV. ENVIRONMENTAL CONSIDERATIONS
Moderately hazardous to birds, fish and beneficial insects.
Hazardous to honey bees. Biological magnification unlikely. Some
injury reported on alfalfa and sorghum (1).
Toxic to bees. Toxic to fish and wildlife so do not use where
shrimp and crab are an important resource. Doesn't persist in the soil.
No harmful effects have been noted on soil microorganisms (8a).
LC50 (96 hr) is: for rainbow trout 2.7 mg/l; for golden orfe 6.9
Approximate Residual Period: 1-2 weeks on plant surfaces;
microencapsulation extends residual period 1 week; short residual in
soil and water (1).
V. EMERGENCY AND FIRST AID PROCEDURES
The chemical information provided below has been condensed
from original source documents, primarily from "Recognition and
Management of Pesticide Poisonings", 3rd ed. by Donald P. Morgan,
which have been footnoted. This information has been provided in
this form for your convenience and general guidance only. In
specific cases, further consultation and reference may be required
and is recommended. This information is not intended as a sub-
stitute for a more exhaustive review of the literature nor for the
judgement of a physician or other trained professional.
If poisoning is suspected, do not wait for symptoms to develop.
Contact a physician, the nearest hospital, or the nearest Poison
FREQUENT SYMPTOMS AND SIGNS OF POISONING BY ORGANOPHOSPHATE PESTICIDES
Symptoms of acute poisoning develop during exposure or within 12
hours (usually within four hours) of contact. headACHE, DIZZINESS,
WEAKNESS, INCOORDINATION, MUSCLE TWITCHING, TREMOR, NAUSEA, ABDOMINAL
CRAMPS, DIARRHEA, and SWEATING are common early symptoms. Blurred or
dark vision, confusion, tightness in the chest, wheezing, productive
cough, and PULMONARY EDEMA may occur. Incontinence, unconsciousness
and convulsions indicate very severe poisoning. SLOW HEARTBEAT,
salivation, and tearing are common. TOXIC PSYCHOSIS, with manic or
bizarre behavior, has led to misdiagnosis of acute alcoholism. Slowing
of the heartbeat may rarely progress to complete sinus arrest.
RESPIRATORY DEPRESSION may be fatal. Continuing daily absorption of
organophosphate at intermediate dosage may cause an INFLUENZA-LIKE
ILLNESS characterized by weakness, anorexia, and malaise (25).
SKIN CONTACT: Bathe and shampoo victim with soap and water if
there is any chance that skin and hair are contaminated (25).
INGESTION: If victim is alert and respiration is not
depressed, give Syrup of Ipecac, followed by 1-2 glasses of water to
induce vomiting. Adults (12 years and over): 30 ml; children under 12
years: 15 ml (25).
NOTES TO PHYSICIAN:
Adminster ATROPINE SULFATE intravenously, or intramuscularly, if IV
injection is not possible.
In MODERATELY SEVERE poisoning: Adult dosage: 0.4-2.0 mg repeated
every 15 mintues until atropinization is achieved: tachycardia (pulse
of 140 per minute), flushing, dry mouth, dilated pupils. Maintain
atropinization by repeated doses for 2-12 hours or longer depending on
severity of poisoning.
Dosage for children under 12 years: 0.05 mg/kg body weight, repeated
every 15 minutes until atropinization is achieved. Maintain
atropinization with repeated dosage of 0.02-0.05 mg/kg.
SEVERELY POISONED individuals may exhibit remarkable tolerance to
atropine; two or more times the dosages suggested above may be needed.
Administer PRALIDOXIME (Protopam (TM)-Ayerst, 2-PAM) in cases of severe
poisoning in which respiratory depression, muscle weakness and
twitchings are severe.
Adult dosage: 1.0 gm intravenously at no more than 0.5 gm per minute.
Child's dose (under 12 years): 20-50 mg/kg (depending on severity of
poisoning) intravenously, injecting no more than half the total dose
Dosage of pralidoxime may be repeated in 1-2 hours, then at 10-12 hour
intervals if needed. In very severe poisonings, dosage rates may be
VI. FIRE AND EXPLOSION INFORMATION
To be developed.
Compatible with most pesticides except alkaline materials.
Penncap-M is compatible with most wettable powders and some liquid
fertilizers with pH below 7.0 (1).
VIII. PROTECTIVE MEASURES
STORAGE AND HANDLING: Do not store near food or feed products. Do not
heat product above 131 F. Store at temperatures above 65 F to avoid
crystallization. Avoid contact with eyes, skin, and mouth. Keep out
of reach of children (56).
PROTECTIVE CLOTHING: Rubber gloves, protective clothing, goggles, and
respirator. Wear mask or respirator approved by U.S. Bureau of Mines
for methyl parathion protection (56).
IX. PROCEDURES FOR SPILLS AND LEAKS
IN CASE OF EMERGENCY, CALL, DAY OR NIGHT
PESTICIDE TEAM SAFETY NETWORK/CHEMTREC
X. LITERATURE CITED
1. Harding, W.C. 1979. Pesticide profiles, part one: insecticides
and miticides. Univ. Maryland, Coop. Ext. Serv. Bull. 267.
8a. Thomson, W. T. 1976. Agricultural chemicals - book 1:
insecticides, acaricides, and ovicides. Revised ed. Thomson
Publ., Indianapolis, IN. 232 pp.
15b. American Conference of Governmental Industrial Hygienists. 1971.
Documentation of the threshold limit values for substances in
workroom air with supplements for those substances added or
changed since 1971, 3rd ed., 4th printing (1977). Cincinnati,
OH. 484 pp.
15c. American Conference of Governmental Industrial Hygienists. 1984.
TLVs: threshold limit values for chemical substances and
physical agents in the work environment and biological exposure
indices with intended changes for 1984-85. Cincinnati, OH.
25. Morgan, D.P. 1982. Recognition and management of pesticide
poisonings, 3rd ed. U.S. Environmental Protection Agency,
Washington, DC. 120 pp.
56. Farm Chemicals Handbook, 70th ed. 1984. R. T. Meister, G. L.
Berg, C. Sine, S. Meister, and J. Poplyk, eds. Meister
Publishing Co., Willoughby, OH.
62. The Pesticide Manual: A World Compendium, 7th ed. 1983. C.R.
Worthing, ed. The British Crop Protection Council, Croydon,
England. 695 pp.