E X T O X N E T
Extension Toxicology Network
A Pesticide Information Project of Cooperative Extension Offices of
Cornell University, Michigan State University, Oregon State University, and
University of California at Davis. Major support and funding was provided
by the USDA/Extension Service/National Agricultural Pesticide Impact
Assessment Program.
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Pesticide
Information
Profile
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Monocrotophos
Publication Date: 9/95
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TRADE OR OTHER NAMES
Trade names for products containing monocrotophos include Azodrin,
Bilobran, Crisodrin, Monocil 40, Monocron, Nuvacron, Pillardrin, and Plantdrin
(1, 2, 3).
REGULATORY STATUS
Use of monocrotophos on potatoes and tomatoes was withdrawn in 1985 (3).
All applications of monocrotophos were discontinued in the United States in
1988 (4). Before its withdrawal, monocrotophos was a Restricted Use Pesticide
(RUP) (5).
INTRODUCTION
Monocrotophos is an organophosphorus insecticide and acaricide which
works systemically and on contact. It is extremely toxic to birds and is used
as a bird poison (1). It is also very poisonous to mammals. It is used to
control a variety of sucking, chewing and boring insects and spider mites on
cotton, sugarcane, peanuts, ornamentals, and tobacco (2, 3). The EPA classifies
monocrotophos as a class I toxicity - highly toxic. Products containing
monocrotophos bear the Signal Word "Danger" (6). Monocrotophos is available in
other countries as a soluble concentrate or an ultra-low volume spray (3).
TOXICOLOGICAL EFFECTS
ACUTE TOXICITY
Monocrotophos is a direct acting cholinesterase inhibitor capable of
penetration through the skin (10). The dose which kills half of the test
animals, the LD50, is 17-18 mg/kg for male rats and 20 mg/kg for female rats.
The LD50 for dermal exposure is 126 mg/kg for male rats, 112 mg/kg for female
rats, and 354 mg/kg for rabbits (3, 7). The concentration in air at which half
of the test animals die, the LC50, is 0.8 mg/l air. Monocrotophos is not
irritating to skin and eyes (2).
Symptoms of monocrotophos poisoning are similar to those of other
organophosphate compounds. Its cholinesterase inhibiting activity causes
nervous system effects. Cases of human poisoning are characterized by muscular
weakness, blurred vision, profuse perspiration, confusion, vomiting, pain, and
small pupils. There is a risk of death due to respiratory failure (8, 11).
CHRONIC TOXICITY
Reproductive Effects
Rats who received doses of 2 mg/kg/day monocrotophos produced fetuses
with lower than average length and weight (9). This dose is much higher than
expected from normal application of this pesticide.
Teratogenic Effects
No teratogenic effects were found at 2 mg monocrotophos/kg/day in rats,
the highest dose tested (9).
Mutagenic Effects
Studies show that monocrotophos may be weakly mutagenic (9).
Carcinogenic Effects
Monocrotophos is not carcinogenic in rats at 0.45 mg/kg/day, the highest
dose tested (9). No significant carcinogenic lesions were observed when rats
were exposed to monocrotophos aerosol at concentrations from 97-308 mg/m3 for
one hour (10).
Organ Toxicity
Monocrotophos affects the central nervous system by inhibiting
cholinesterase, an enzyme essential for normal nerve impulse transmission.
Fate in Humans and Animals
Monocrotophos is metabolized and excreted rapidly and does not appear to
accumulate within the body (10). In mammals, 60-65% is excreted within 24
hours, predominantly in the urine (8).
ECOLOGICAL EFFECTS
Effects on Birds
Monocrotophos is highly toxic to birds (3). The LD50 is 0.76 mg/kg for
California quail, 0.94 mg/kg for bobwhite quail, 1.58 mg/kg for Canada goose,
3.3 mg/kg for European starling and 4.76 mg/kg for mallard ducks (1).
Effects on Aquatic Organisms
Monocrotophos is moderately toxic to fish (3). The LC50 (48 hrs) is 7
mg/l for rainbow trout and 23 mg/l for bluegill sunfish (2). Monocrotophos
causes reproductive damage to crustaceans exposed for long periods of time
(4).
Effects on Other Animals (Nontarget species)
Monocrotophos is highly toxic to bees (2). It may also kill non-target
birds which eat insects poisoned with monocrotophos (1).
ENVIRONMENTAL FATE
Breakdown of Chemical in Soil and Groundwater
Monocrotophos has a low environmental persistence. It does not accumulate
in soil because it is biodegradable. Its half-life is less than 7 days in soil
exposed to natural sunlight (1, 3, 9).
Breakdown of Chemical in Surface Water
No information is currently available.
Breakdown of Chemical in Vegetation
Monocrotophos has a half-life of 1.3 to 3.4 days on plant foliage (13).
It causes slight injury to some varieties of apple, pear, cherry, peach and
sorghum (8).
PHYSICAL PROPERTIES AND GUIDELINES
Monocrotophos is a reddish brown crystalline solid with a mild odor (10).
It is stable when stored in glass or polyethylene containers at room
temperature. It is relatively stable in sunlight and is non-volatile.
Hydrolysis is slow and the half-life for monocrotophos in solution is 23 days
at pH 7 and 38 degrees C (9).
Physical Properties:
| CAS #: | 2157-98-4 (mixed isomers) |
| Chemical Name: | dimethyl (E)-1-methyl-2-(methylcarbamoyl)vinyl phosphate |
| Melting point: | 54-55 degrees C (10) |
| Boiling Point: | 125 degrees C (10) |
| Solubility in water: | Soluble in water (3) |
| Solubility in other solvents: | Soluble in acetone and alcohol (3) |
Exposure Guidelines:
| ADI: | 0.0006 mg/kg (2, 12) |
| NOEL: | 0.03 ppm (rat) 1.6 ppm (dog) (cholinesterase inhibition) (9) |
| OSHA PEL: | PEL-TWA: 0.25 mg/m3 (10) |
| TLV-TWA: | 0.25 mg/m3 (10) |
BASIC MANUFACTURER
CIBA Agricultural Division
P.O. Box 18300
Greensboro, NC 27419-8300
Telephone: 919-632-6000
Review by Basic Manufacturer:
Comments solicited: October, 1994
Comments received: January, 1995
REFERENCES
Smith, G. J. 1993. Toxicology & Pesticide Use in Relation to Wildlife:
Organophosphorus & Carbamate Compounds. C.K. Smoley. Boca Raton, FL.
The Agrochemicals Handbook, Third Edition. 1994. Royal Society of
Chemistry Information Systems, Unwin Brothers Ltd., Surrey, England.
Meister, R.T. 1992. Farm Chemicals Handbook '92. Meister Publishing
Company. Willoughby, OH.
Briggs, Shirley. 1992. Basic Guide to Pesticides. Hemisphere
Publishing. Washington, DC.
Darcy Miller, Publisher. 1985. Protection Chemicals Reference.
Chemical and Pharmaceutical Publishing Corp. New York, NY.
Meister, R.T. 1994. Farm Chemicals Handbook '94. Meister Publishing
Company. Willoughby, OH.
Budavari, Susan (ed.). 1989. The Merck Index, Eleventh Edition. Merck
and Company Inc. Rahway, NJ.
Hayes Jr., Wayland and E. R. Laws, Jr. (eds.). 1991. Handbook of
Pesticide Toxicology. Academic Press, Inc. New York, NY.
U.S. Environmental Protection Agency. 1985. Pesticide Fact Sheet No.
72: Monocrotophos. U.S. EPA. Washington, DC.
American Conference of Governmental Industrial Hygienists. 1991.
Documentation of the Threshold Limit Values and Biological Exposure Indices:
Sixth Edition, Volume I. ACGIH. Cincinnati, OH.
Senanayake, N. and L. Karalliedde. "Neurotoxic Effects of
Organophosphorus Insecticides, An Intermediate Syndrome." New England Journal
of Medicine. Vol. 316, No.13. pp. 761-763.
Baker, Scott and C. F. Wilkinson (eds.). 1990. The Effect of
Pesticides on Human Health. Volume XVIII of Advances in Modern Environmental
Toxicology. Princeton Scientific Publishing Co. Princeton, NJ.
Chambers, Janice and Patricia Levi. 1992. Organophosphates Chemistry,
Fate and Effects. Academic Press, Inc. New York, NY.
Disclaimer: Please read
the pesticide label prior to use. The information contained at this web
site is not a substitute for a pesticide label. Trade names used herein
are for convenience only; no endorsement of products is intended, nor is
criticism of unnamed products implied. Most of this information is historical
in nature and may no longer be applicable.
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