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The information in this profile may be out-of-date. It was last revised in 1996. EXTOXNET no longer updates this information, but it may be useful as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated pesticide fact sheets. If you don't find a fact sheet related to your question, feel free to call 1-800-858-7378. NPIC is open five days a week from 8:00am to 12:00pm Pacific Time.

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E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised 9/95.

MONOCROTOPHOS

TRADE OR OTHER NAMES: Trade names for products containing monocrotophos include Azodrin, Bilobran, Crisodrin, Monocil 40, Monocron, Nuvacron, Pillardrin, and Plantdrin (6, 13, 154).

REGULATORY STATUS: Use of monocrotophos on potatoes and tomatoes was withdrawn in 1985 (154). All applications of monocrotophos were discontinued in the United States in 1988 (115). Before its withdrawal, monocrotophos was a Restricted Use Pesticide (RUP) (127).

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 (6). 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 (13,154). The EPA classifies monocrotophos as a class I toxicity - highly toxic. Products containing monocrotophos bear the Signal Word "Danger" (112). Monocrotophos is available in other countries as a soluble concentrate or an ultra-low volume spray (154).

TOXICOLOGICAL EFFECTS

• Acute Toxicity: Monocrotophos is a direct acting cholinesterase inhibitor capable of penetration through the skin (171). 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 (154,126). 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 (13). 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 (2, 163).
• Chronic Toxicity: No Information Available.
• Reproductive Effects: Rats who received doses of 2 mg/kg/day monocrotophos produced fetuses with lower than average length and weight (170). 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 (170).
• Mutagenic Effects: Studies show that monocrotophos may be weakly mutagenic (170).
• Carcinogenic Effects: Monocrotophos is not carcinogenic in rats at 0.45 mg/kg/day, the highest dose tested (170). No significant carcinogenic lesions were observed when rats were exposed to monocrotophos aerosol at concentrations from 97-308 mg/m3 for one hour (171).
• 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 (171). In mammals, 60-65% is excreted within 24 hours, predominantly in the urine (2).

ECOLOGICAL EFFECTS

• Effects on Birds: Monocrotophos is highly toxic to birds (154). 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 (6).
• Effects on Aquatic Organisms: Monocrotophos is moderately toxic to fish (154). The LC50 (48hrs) is 7 mg/l for rainbow trout and 23 mg/l for bluegill sunfish (13). Monocrotophos causes reproductive damage to crustaceans exposed for long periods of time (115).
• Effects on Other Animals (Nontarget species): Monocrotophos is highly toxic to bees (13). It may also kill non-target birds which eat insects poisoned with monocrotophos (6).

ENVIRONMENTAL FATE

• Breakdown of Chemical in Soil and Groundwater: Monocrotophos has a low environmental persistence. It doesnot accumulate in soil because it is biodegradable. Its half-life is less than 7 days in soil exposed to natural sunlight (6,154,170).
• 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 (133). It causes slight injury to some varieties of apple, pear, cherry, peach and sorghum (2).

PHYSICAL PROPERTIES AND GUIDELINES

Physical Properties:

• Appearance: Monocrotophos is a reddish brown crystalline solid with a mild odor (171).
• Chemical Name: dimethyl (E)-1-methyl-2-(methylcarbamoyl)vinyl phosphate
• CAS Number: 2157-98-4 (mixed isomers)
• Molecular Weight: 223.2
• Water Solubility: Soluble in water (154)
• Solubility in Other Solvents: soluble in acetone and alcohol (154)
• Melting Point: 54-55 degrees C (171)
• Vapor Pressure: 2.9 x 10-1 mPa (20 degrees C)
• Partition Coefficient: -0.22
• Adsorption Coefficient: Not Available

Exposure Guidelines:

• ADI: 0.0006 mg/kg (13, 172)
• MCL: Not Available
• RfD: Not Available
• PEL: 0.25 mg/m3 (171)
• HA: Not Available
• TLV: 0.25 mg/m3 (171)

BASIC MANUFACTURER:

CIBA Agricultural Division
P.O. Box 18300
Greensboro, NC 27419-8300

• Telephone: 919-632-6000

REFERENCES

References for the information in this PIP can be found in Reference List Number 5