Methamidophos, trade name "Monitor," is an

organophosphate In organic chemistry, organophosphates (also known as phosphate esters, or OPEs) are a class of organophosphorus compounds with the general structure , a central phosphate molecule with alkyl or aromatic substituents. They can be considered ...

insecticide Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed t ...

. Crops grown with the use of methamidophos include potatoes and some Latin American rice. Many nations have used methamidophos on crops, including developed nations such as

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United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...

, and

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

. Due to its toxicity, the use of pesticides that contain methamidophos is currently being phased out in

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

. In 2009, all uses in the United States were voluntarily canceled.

Toxicity

rates of 21 and 16 mg/kg for male and female rats, respectively. 10–30 mg/kg in

rabbits Rabbits, also known as bunnies or bunny rabbits, are small mammals in the family Leporidae (which also contains the hares) of the order Lagomorpha (which also contains the pikas). ''Oryctolagus cuniculus'' includes the European rabbit sp ...

, and dermal LD50 of 50 mg/kg in rats. It is rapidly absorbed through the stomach, lungs, and skin in humans, and eliminated primarily through urine. It is a

cholinesterase The enzyme cholinesterase (EC 3.1.1.8, choline esterase; systematic name acylcholine acylhydrolase) catalyses the hydrolysis of choline-based esters: : an acylcholine + H2O = choline + a carboxylate Several of these serve as neurotransmitters ...

inhibitor. Breakdown in soil is 6.1 days in sand, 309 days in water at pH 5.0, 27 days at pH 7.0, and 3 days at pH 9.0. Sunlight accelerates breakdown. It is uptaken through roots and leaves of plants. It is classified as a WHO Toxicity Class "Class 1b, Highly Hazardous", and its parent chemical, acephate, is "class III, Slightly Hazardous".

Use

Methamidophos is used in great quantities in ricefields in China. Rice–fish culture is common in the southern parts of China as well as in many other rice-producing countries (e.g.,

Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...

Malaysia Malaysia ( ; ) is a country in Southeast Asia. The federal constitutional monarchy consists of thirteen states and three federal territories, separated by the South China Sea into two regions: Peninsular Malaysia and Borneo's East Mal ...

, and the

Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

). Brown rice (unpolished) in this study contained double the concentration of polished rice. Both plants and animals did not degrade the pesticide well, and fish for human consumption in these cases contains methamidophos in concentrations roughly similar to brown rice.

Use in poisoning

Methamidophos was found in dumplings ( gyoza) manufactured in China for the Japanese market after a number of consumers became sick.

References

External links

* {{Consumer Food Safety Acetylcholinesterase inhibitors Organophosphate insecticides Phosphoramidothioates Methoxy compounds