The widespread occurrence in the environment of any foreign chemical is a matter of public health concern. The pesticides are poisons, of course, or they would not be useful in the control of insects, rodents, and other undesirable animals and plants. The possible harmful effect to the general population from intake of small amounts of these pesticidal chemicals as residues in food, water, air, or from other sources must be evaluated. In determining the overall effect on public health directly through control of insect-vector-borne diseases and indirectly through increased and improved agricultural production of food and fiber.