Biology

Food and Agriculture Organization defined Pesticide as any substance or mixture of substances intended for preventing, destroying or controlling any pest, including vectors of human or animal disease, unwanted species of plants or animals causing harm during or otherwise interfering with the production, processing, storage, transport or marketing of food, agricultural commodities, wood and wood products or animal feedstuffs, or substances which may be administered to animals for the control of insects, arachnids or other pests in or on their bodies. The term includes substances intended for use as a plant growth regulator, defoliant, desiccant or agent for thining fruit or preventing the premature fall of fruit, and substances applied to crops either before or after harvest to protect the commodity from deterioration during storage and transport.

This term is well known as anti-pest on any botanical living things that are prone to pests and also as household pesticides. Some commonly known pests are insects, plant pathogens, molluscs, weeds, birds, mammals, roundworms, fish and mircrobes that destroy the botanical living things or are also sources of diseases. Though pesticides are beneficial in keeping away the pest, they also have potential toxicity to environment, humans and other animals.

Sample Effective but Harmful Pesticide
In year 1950, DDT (an organochloride) was used to fight against malaria. They were being sprayed on walls of houses. Even the WHO (World Health Organization) supported this approach and stated that it has been the best tools they have against that disease. However, a study linked breast cancer from the exposure to DDT.  Also, by entering the human food chain poisoning may also occur due to the use of DDT.

Some sample of pesticides that can be found in our home are pet shampoo, insect and pest killer and some insect sprays.
Types of Pesticides
The types of pesticides depends on the type of pest they are being used.
Categories
Chemical Pesticides
Organophosphate Pesticides  most of this type are insecticides which some are very poisonous but are not persistent in the environment. This type affects the nervous system by interrupting the progress of enzyme which controls acetylcholine, a neurotransmitter.

Carbamate Pesticides  same as Organophosphate Pesticides except that it consists of two  HYPERLINK httpwww.wisegeek.comwhat-is-methomyl.htm methomyl groups linked by amino  HYPERLINK httpwww.wisegeek.comwhat-is-nitrogen.htm nitrogen through  HYPERLINK httpwww.wisegeek.comwhat-is-sulfur.htm sulfur molecules.
Organochlorine Insecticides  this is used on fruits, vegetables, livestock, black flies and mosquitoes. It is also historically significant since it was already used a long time ago but has significant effects on environment, agriculture and health.

Pyrethroid Pesticides  this is a man-made pesticide same as pesticide pyrethrum. It is also found on commercial pesticides like shampoo, insect sprays and pest sprays.
Biopesticides  pesticides derived from natural materials.
Microbial pesticides  pesticide which the main ingredient are microorganisms.
Plant-Incorporated-Protectants (PIPs)  pesticides substance that are being produced by plants.
Biochemical pesticides  this pesticide includes substance that interfere mating (insect sex pheromones) as well as scented extracts of plants that attracts insects to their traps.
Pest Control Devices  an instrument intended for killing or trapping pest. (e.g. Mouse trap)

Environmental Protection Agency (EPA)
This is a government agency in the United States which writes and enforces laws and regulation to protect human and environment. Office of Prevention, Pesticides, and Toxic Substances is the specified agency for pesticides. They evaluate the pesticides and chemicals to keep people safe and also against environment harm.