Pesticides are chemicals that are used to kill insects, weeds, and other organisms to protect humans, crops, and livestock. There have been many substantial benefits of the use of pesticides. The most important of these have been: (1) an increased production of food and fibre because of the protection of crop plants from pathogens, competition from weeds, defoliation by insects, and parasitism by nematodes; (2) the prevention of spoilage of harvested, stored foods; and (3) the prevention of debilitating illnesses and the saving of human lives by the control of certain diseases.

Unfortunately, the considerable benefits of the use of pesticides are partly offset by some serious environmental damages. There have been rare but spectacular incidents of toxicity to humans, as occurred in 1984 at Bhopal, India, where more than 2,800 people were killed and more than 20,000 seriously injured by a large emission of poisonous methyl isocyanate vapor, a chemical used in the...