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Pesticides and Herbicides

The term pesticide includes many ingredients used in products such as insect repellents, rodent poison, weed killers, and swimming pool chemicals, as well as disinfectants, wood preservatives, and plant growth regulators. These substances are designed to kill, repel, or otherwise control unwanted organisms. Pesticides play a large role in agriculture, industry, home/garden maintenance and public health. Of course, these benefits are balanced by potential risks to human health and the environment due to pesticide toxicity, potency, and persistence in the environment. For this reason, the chemicals are regulated.

Organophosphate pesticides represent the largest class of pesticides in use today. These compounds affect the nervous system by disrupting the enzyme that regulates acetylcholine, a neurotransmitter. Most organophosphates are insecticides. Organophosphates, in general, are acutely toxic, and many compounds were developed as nerve agents and used in World War II.These compounds include sarin and isopropylmethyl phosphonic acid (IMPA) Examples of organophosphate pesticides are chlorpyrifos, diazinon, and malathion.

Carbamate pesticides also affect the nervous system by using an acetylcholine disupter. There are several subgroups within the classification of carbamate pesticides, including aldicarb, carbaryl, carbofuran, and others.

Organochlorine insecticides were commonly used in the past, but many have been removed from the market due to their health concerns, persistence, and long-term environmental effects (e.g. DDT and chlordane).

Pyrethroid pesticides were developed as a synthetic version of the naturally-occurring pesticide pyrethrin, which is found in chrysanthemums. These compounds have been modified to increase their stability in the environment. Some synthetic pyrethroids can be toxic to the nervous system.