A pesticide can be categorized by the type of pest it is designed to control, such as an insecticide (e.g., bug spray), herbicide (e.g., weed-killer), bactericide (“antimicrobial” kills bacteria), fungicide (kills molds and fungi), or rodenticide (e.g. rat poison). Pesticides are also classified by the chemical class to which they belong, such as organophosphates, carbamates, chlorophenoxy herbicides, or pyrethroids. Some of the widely used pesticides of concern in the United States include the herbicide glyphosate, organophosphate insecticides (e.g. chlorpyrifos, malathion), carbamate insecticides (e.g. carbaryl, propoxur), neonicotinoid insecticides (e.g. imidacloprid, thiamethoxam), and pyrethroid insecticides (e.g. permethrin, cypermethrin). The application method used (such as bait, trap, gel, spray, fogging, etc.) can affect both the pesticide concentration and the distance that the chemicals may spread. Members of a chemical class often share similar modes of action and toxicological properties.
Acute, high dose severe poisonings are relatively uncommon in the United States. Most serious acute poisonings occur after unintentional ingestion, although poisoning may also follow inhalational exposure (particularly from fumigants) or significant dermal exposure, such as in drift events. Chronic or repeated low-dose exposures are common as children encounter pesticides in their diet, on surfaces or soils in play areas, schools and homes. Pesticides can also be found in breastmilk among those who have eaten high fat foods (ex. dairy, red meat) that contain pesticide residues. Increasing evidence suggests these lower-level accumulated exposures may compromise healthy child development. Groups at higher risk of concerning exposures include children whose household members such as their parents use pesticides on the job and children who reside in agricultural communities where intensive pesticide use takes place.