Pesticides are a broad class of chemicals and biological agents that are specifically designed and applied to kill a pest. Specific types of pesticides target specific types of pests: insecticides kill insects, fungicides kill fungi and bacteria, herbicides kill weeds and other unwanted plant vegetation, molluscacides kill mollusks, acaricides kill spiders, and so on. Pesticide use dates back to ancient times.
Pesticides are regulated in the United States at both the federal and state level. The primary legislation, one of the oldest environmental laws, is the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA, 1972), which is administered by the Environmental Protection Agency (EPA). Each state also has an agency responsible for carrying out FIFRA mandates. These agencies may be environmental or agricultural in nature, depending on the state. State laws can be more restrictive than the federal laws.
Pesticides are sometimes called "economic poisons." They are developed to kill something, and they are, therefore, inherently toxic. Pesticides that are less toxic are classified as "general use pesticides." These can be purchased by the average homeowner and applied without any special license or permits. More toxic compounds are called "restricted use pesticides" and their use requires a license. In some cases the restricted use materials have the same active ingredients as the general use materials, but at a higher concentration.
Anything that claims that it has pesticidal activity is, by law, a pesticide, and is subject to registration by the EPA and local state agencies. Household cleaners and bleach are legally pesticides—the pesticide registration number can be found on the product container.
Within the broad classes of products that have similar types of action (e.g., weed killers, insect killers) there are further distinctions regarding the type of chemistry. For example, among insect killers, there are synthetic pyrethroids, organophosphates, and organochlorines. The most well known are the organochlorines, such as chlordane and DDT, which became popular after World War II, and were used in agriculture, and for home and commercial use, for decades. These compounds have low acute toxicity, but are persistent in the environment and have caused a series of long-term environmental health problems. They remain in soil and tissue for a very long time, and they have been shown to have a harmful impact on animal endocrine systems. Most organochlorines were phased out of use in the 1980s. They were replaced by organophosphate materials that are less persistent, but more acutely toxic. In the beginning of the 1990s these compounds, too, were beginning to be phased out through government actions, and voluntarily by the manufacturers.
Pesticides have entered the food system in many parts of the world. Though credited with an enormous increase in food and fiber production, indiscriminate use of these products has led to acute and long-term health problems for humans and animals. There are risks associated with the application of a pesticide into a system, while at the same time there are benefits for using these materials to reduce disease, increased food production, and lessen the risk of starvation.
Pesticides have been applied in many part of the world to control vector-borne diseases such as malaria, yellow fever, dengue, and others. The most prudent way to balance the benefits with the risks is an integrated approach to pesticide use, combining all control methods—physical, biological, cultural, and chemical.
MARK G. ROBSON
Hayes, W., and Laws, E. (1991). Handbook of Pesticide Toxicology, Vol. 1. San Diego, CA: Academic Press.
Wallace, R., ed. (1998). Maxcy-Rosenau-Last Public Health and Preventive Medicine. Stamford, CT: Appleton and Lange.