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 pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, i ...
.
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
Spain
Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...
,
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
,
Japan
Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
, and
Australia
Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
. Due to its toxicity, the use of pesticides that contain methamidophos is currently being phased out in
Brazil
Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
. 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 are small mammals in the family Leporidae (which also includes the hares), which is in the order Lagomorpha (which also includes pikas). They are familiar throughout the world as a small herbivore, a prey animal, a domesticated form ...
, and
dermal
The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided i ...
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 neurotransmitte ...
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
The World Health Organization (WHO) is a specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Geneva, Switzerland, and has 6 regional offices and 15 ...
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, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...
,
Malaysia
Malaysia is a country in Southeast Asia. Featuring the Tanjung Piai, southernmost point of continental Eurasia, it is a federation, federal constitutional monarchy consisting of States and federal territories of Malaysia, 13 states and thre ...
, and the
Philippines
The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...
). 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.
Consumer Toxicity
Methamidophos was found in dumplings (
gyoza
''Jiaozi'' or Gyoza (; ) are a type of Chinese dumpling. ''Jiaozi'' typically consist of a ground meat or vegetable filling wrapped into a thinly rolled piece of dough, which is then sealed by pressing the edges together. ''Jiaozi'' can be ...
) manufactured in China for the Japanese market after a number of consumers became sick.
See also
*
GS-7
References
External links
*
{{Consumer Food Safety
Acetylcholinesterase inhibitors
Organophosphate insecticides
Phosphoramidothioates
Methoxy compounds