Malathion in aerial spraying programs
Malathion is an organophosphate pesticide widely used in aerial spraying programs to control insect populations, particularly mosquitoes, fleas, and fruit flies. Introduced in 1952, it replaced more persistent pesticides like DDT due to its relatively short environmental lifespan, breaking down into less harmful substances within days to weeks. While some concerns about potential health effects and environmental impact have arisen—such as the presence of trace impurities and the toxic breakdown product malaoxin—extensive studies have generally found no adverse health effects from low-level exposure in humans or animals. This has led to its continued use, even amid growing public skepticism about synthetic pesticides. Major urban areas, including New York City and Winnipeg, have employed malathion spraying in efforts to combat mosquito-borne diseases like West Nile virus. Critics advocate for more sustainable pest control methods, yet the urgency of public health concerns often supports the use of aerial spraying programs. The debate around malathion illustrates the tension between effective pest management and environmental health, reflecting diverse perspectives on pesticide use in public health initiatives.
On this Page
Subject Terms
Malathion in aerial spraying programs
DEFINITION: An organophosphorus pesticide used against mosquitoes, fleas, and other insects
Although no adverse health effects have been found from low-level exposure to malathion, the use of this pesticide in aerial spraying programs has been controversial.
Pesticides have been used to control crop loss and prevent the spread of disease for hundreds of years. Until the middle of the twentieth century, pesticides were either toxic metals (such as arsenic or lead) or natural products (such as nicotine sulfate). With the discovery of Dichloro-diphenyl-trichloroethane (DDT) in 1939, new human-made pesticides became available for use. However, it was soon found that DDT and related chlorinated hydrocarbon pesticides persist in the for years, causing damage to birds, fish, and other wildlife. Other pesticides, including organophosphate compounds, were therefore developed as alternatives to DDT.
Malathion is an organophosphate compound that is chemically similar to some types of nerve gas but less toxic than most other organophosphate pesticides. Unlike chlorinated hydrocarbons, malathion breaks down in the environment, transforming into carbonic and phosphoric acid over a period of days to a few weeks. Because of its relatively short lifetime, malathion does not bioaccumulate in aquatic organisms or contaminate groundwater. Following its introduction by the American Cyanamid Company in 1952, malathion quickly became a popular substitute for DDT in controlling mosquitoes, fleas, lice, and other insects. In 1956, malathion was first used to counteract fruit fly infestations.
In the following decades, the use of malathion continued to increase. In the 1980s, the spraying of malathion in California to control the Mediterranean fruit fly (also known as the Medfly) became a source of controversy. Those critical of the use of malathion in populated areas noted that commercial preparations of malathion contain trace impurities that are potentially toxic and that the initial breakdown products from malathion include malaoxin, a compound with acute forty times that of malathion itself. Critics also suggested that malathion might be carcinogenic or could weaken the immune system, making people more susceptible to disease. However, extensive studies of human populations exposed to malathion through the spraying program found no adverse health effects from low levels of exposure. Similarly, no harmful effects have been observed from low-level to malathion in laboratory studies on animals. Despite the controversy, malathion continued to be used to prevent damage to citrus crops in California, Florida, and other states, and to be available in many commercial products.
By the end of the twentieth century, controversy over the use of synthetic pesticides such as malathion had convinced many people that the of such compounds into the environment should be greatly reduced, but malathion continued to be used in some areas into the twenty-first century. Both New York City and the city of Winnipeg in Manitoba, Canada, used malathion spraying (in 2000 and 2005, respectively) as part of their attempts to eradicate insects, particularly mosquitoes, that might be carriers of West Nile virus. Critics of human-made pesticides have continued to call for more intelligent use of pesticides and the development of alternative methods of controlling insect populations. However, the dangers to human health posed by West Nile, dengue, and Zika virus make aerial spraying of malathion one of the best methods of pest control, according to the US Environmental Protection Agency.
Bibliography
Hamilton, Denis, and Stephen Crossley, eds. Pesticide Residues in Food and Drinking Water: Human Exposure and Risks. Hoboken, N.J.: John Wiley & Sons, 2004.
Levine, Marvin J. “Pesticides in Food.” In Pesticides: A Toxic Time Bomb in Our Midst. Westport, Conn.: Praeger, 2007.
"Malathion." US Environmental Protection Agency, 17 July 2024, www.epa.gov/mosquitocontrol/malathion. Accessed 19 July 2024.
Manahan, Stanley E. Fundamentals of Environmental Chemistry. 3d ed. Boca Raton, Fla.: CRC Press, 2009.