Pesticides are meant to mitigate pests by means of extermination. In general, pesticides may be categorized by the type of pest they are intended to control or by their chemical composition.

Common pesticide groups include:

Biocides — target and kill microorganisms
Fungicides — target and kill fungi (including mold, mildew)
Herbicides — target and kill unwanted plant growth (i.e. weeds)
Insecticides — target and kill insects
Rodenticides — target and mitigate rodents (i.e. mice, rats)

Examples of chemically-related pesticide categories include:

Organophosphate Pesticides: These pesticides (most of which are insecticides) function as acetyl-cholinesterase disruptors, thus interfering with neuronal transmission in insects. While they are relatively non-persistent in the environment, they have been found to induce neuro-disruptive effects in humans similar to their effects on insects.

Carbamate Pesticides: Carbamates have been found to have a relatively low oral and dermal toxicity to mammals while targeting a broader spectrum of insects. They eliminate insects by disrupting the acetyl-cholinesterase action of the nervous system.

Organochlorine Pesticides: This group of pesticides (which includes chlordane and dichlorodiphenyltrichloroethane [DDT]) were common in the past, but have been outlawed in many places due to their persistence in the environment and high bioaccumulation.

Pyrethroids and Pyrethrins: These pesticides are included in thousands of registered insecticides. They work by targeting and altering nerve function in insects, thus resulting in death. During the last decade, there has been an increase in the usage of these pesticides as they are believed to be less acutely toxic than organophosphate insecticides.