Methyl parathion (pesticide)
Methyl parathion is a highly toxic organophosphate pesticide primarily used in agriculture to control pests such as boll weevils, mites, and mosquito larvae. Its chemical structure is denoted by the formula C8H10NO5PS, and it is also known by various names, including parathion-methyl and metafos. Due to its neurotoxic effects, which inhibit cholinesterase and can lead to severe health risks, including death, the use of methyl parathion is heavily regulated in the United States. It is classified as a restricted-use pesticide, meaning it can only be applied by certified professionals, and applications require strict adherence to safety guidelines, including a 48-hour re-entry period for agricultural workers after treatment.
Despite its effectiveness, methyl parathion poses significant environmental risks, affecting aquatic life and beneficial insects like honeybees. Its persistence in the environment can lead to harmful effects on wildlife and ecosystems. The pesticide has been phased out for many agricultural applications due to health and safety concerns, particularly regarding its potential carcinogenic properties and impacts on food safety. Regulatory bodies, including the EPA, have taken measures to minimize its use, particularly in crops commonly consumed by children. Overall, methyl parathion exemplifies the complexities involved in pesticide use, balancing agricultural needs against human health and environmental protection.
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Methyl parathion (pesticide)
DEFINITION: Neurotoxin used on agricultural crops to kill pests, especially boll weevils, mites, and mosquito larvae
Because methyl parathion is a highly toxic compound, its use in the United States is subject by law to many restrictions.
The molecular formula for methyl parathion is C8H10NO5PS, and the chemical name is O,O-dimethyl (4-nitrophenyl) phosphorothioate. Also known as parathion-methyl and metafos, and commonly called cotton poison and roach milk, methyl parathion has been marketed under such trade names as Metacide and Penncap-M and packaged in dust, liquid, and emulsifiable concentrate forms. The U.S. Environmental Protection Agency (EPA) classifies methyl parathion as a restricted-use (RUP) that can be sold and utilized solely by certified applicators. Methyl parathion packaging is distinguished with the word “danger” to alert users of potential harmful contact. The EPA forbids agricultural workers from being in a field treated with methyl parathion for forty-eight hours after application of the pesticide.
Methyl parathion is an organophosphate that inhibits the cholinesterase, which is crucial to healthy functioning of the nervous system. If absorbed through the skin, inhaled, or ingested, the pesticide blisters tissues, retards reproductivity, and can cause death. Methyl parathion is toxic to aquatic organisms such as fish, shrimp, and crabs and harmfully affects carnivores that consume tainted organisms. Contaminated game animals pose a danger to hunters who eat the animals’ flesh.
By killing algae-eating insects and crustaceans, methyl parathion has the unintended side effect of causing to reproduce rapidly; the algae then use oxygen that other water inhabitants need. In addition, methyl parathion poisons small mammals such as rats and rabbits, is harmful to birds and to beneficial insects such as honeybees, and has been reported to injure alfalfa and sorghum.
Methyl parathion usually requires several months to break down in soil, but it does not leave dangerous residues or kill soil microorganisms. The speed of degradation increases with higher temperatures, with to sunlight, and in flooded soil. While small amounts of methyl parathion do not contaminate groundwater, spills require longer to degrade. The pesticide degrades more quickly in flowing water, in fresh water, and in water bodies with sediments. In plants, methyl parathion is almost completely metabolized within a week.
Although it is considered safe only for outdoor use, methyl parathion is effective against cockroaches and rats; because of this effectiveness, unlicensed exterminators often spray the chemical inside homes. In 1996 the EPA evacuated residents of one thousand contaminated homes in Mississippi and spent millions of dollars to rebuild the structures. To prevent misuses of the pesticide, manufacturers, in agreement with the EPA, instituted a computerized system to track the locations of containers of methyl parathion.
Methyl parathion poses combustion hazards above 100 degrees Celsius (212 degrees Fahrenheit) and releases toxic fumes, including dimethyl sulfide, sulfur dioxide, and carbon monoxide. Concerns about adverse toxic effects of pesticide products have resulted in studies of methyl parathion’s potential carcinogenic tendencies. In 1992 producers of methyl parathion stopped supporting its use on such agricultural crops as strawberries and tobacco and for mosquito control in forests. In 1999, the EPA eliminated use of the pesticide on crops particularly likely to form large parts of children’s diets; these included apples, peaches, pears, grapes, nectarines, cherries, plums, carrots, certain peas, certain beans, and tomatoes. US Food and Drug Administration regulations allow only 0.1 to 1 parts per million of methyl parathion residue to be remain on food crops.
Bibliography
Friis, Robert H. “Pesticides and Other Organic Chemicals.” In Essentials of Environmental Health. 3rd ed. Sudbury, Mass.: Jones and Bartlett, 2018.
Hilgenkamp, Kathryn. “Pests and Pesticides.” In Environmental Health: Ecological Perspectives. Sudbury, Mass.: Jones and Bartlett, 2006.
"Public Health Statement for Methyl Parathion." Centers for Disease Control and Prevention, 20 Mar. 2014, wwwn.cdc.gov/TSP/PHS/PHS.aspx?phsid=633&toxid=117. Accessed 19 July 2024.