Overview

Methamidophos is a highly toxic, highly regulated systemic and residual organophosphate insecticide, [acaracide], and [avicide] (EXTOXNET). Its Health Effects are consistent with all Organophosphates, and result in the inhibition of the enzyme cholinesterase which disrupts normal transmission of [nerve] impulses (EXTOXNET). Because of its toxicity, it is highly regulated throughout the world.

Chemical Description

It is a yellow-ish to colorless crystalline solid at room temperature with a melting point of 44.5 degrees Celsius (FAO). Technical methamidophos (about 73%) is in the form of yellowish to colourless crystals with melting point below 40 °C and methamidophos decomposes on heating without boiling and is used only as a spray (FAO and INCHEM).

Uses

Methamidophos is a residual and systemic organophosphate insecticide with both contact and ingestion properties to control insects such as aphids, flea beetles, worms, whiteflies, thrips, cabbage loopers, Colorado potato beetles, potato tubeworms, armyworms, mites, leafhoppers, and many others (EXTOXNET). The crops that methamidophos are use don crops suck as broccoli, Brussel sprouts, cauliflower, grapes, celery, sugar beets, cotton, tobacco, and potatoes. It is used abroad for many vegetables, hops, corn, peaches, and others (EXTOXNET).

Health Effects

Main Article: Cholinesterase Inhibitor
Methamidophos is highly toxic via all routes of exposure. It has been found to have negative effects on reproductive effects including one study found decreased sperm levels in men who were exposed to Tamaran in China (EXTOXNET and FAO). It is not thought to be carcinogenic (FAO

Environmental Effects

Methamidophos is very toxic to birds, aquatic organisms, and bees (EXTOXNET).

Its half life in soil is relatively short, about 1.9 days in silt, 4.8 days in loam, 6.1 days in sand, and 10-12 days in sandy loam and the population is not generally exposed to methamidophos in the soil or water (EXTOXNET and FAO).

Precautions

Only registered and supervised applicators should apply methamidophos and they need to follow all guidelines (FAO). All applicators should wear protective clothing and a respirator if spraying taller crops and if a worker is suspected of being exposed to methamidophos then the worker should be kept under supervision for up to 48 hours (FAO).

Regulation

Methamidophos is a US EPA registered, Class I compound which must bear the words "Danger-Poison" n commercial products and is banned, restricted or canceled in 13 countries and not legal for import in 44 countries (PAN and EXTOXNET).

External Links

• PANA on Methamidophos.
  
  

References

Extension Toxicology Network. "Pesticide Information Profile - Methamidophos. Accessed 11-16-07.

Food and Agriculture Organization of the UN. "FAO Corporate Document Registry - Methamidiphos". Accessed 11-16-07.

Pesticides Action Network (PAN) Database. "Methamidophos".

International Programme on Chemical Safety (INCHEM). "Methamidophos". 1976.