Chapter 22

• A pesticide may be defined as any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest.
• Pesticide exposures include (1) accidental and/or suicidal poisonings; (2) occupational exposure (manufacturing, mixing/loading, application, harvesting, and handling of crops); (3) bystander exposure to off-target drift from spraying operations; and (4) the general public who consume food items containing pesticide residues.
• Chemical insecticides in use today poison the nervous systems of the target organisms.
• An herbicide is any compound that is capable of either killing or severely injuring plants.
• A fungicide is any chemical capable of preventing growth and reproduction of fungi.

Pesticides can be defined as any substance or mixture of substances deliberately added to the environment and intended for preventing, destroying, repelling, or mitigating pests. Pesticides may be more specifically identified as insecticides (insects), herbicides (weeds), fungicides (fungi and molds), rodenticides (rodents), acaricides (mites), molluscides (snails and other mollusks), miticides (mites), larvicides (larvae), and pediculocides (lice). In addition, for regulatory purposes, plant growth regulators, repellants, and attractants (pheromones) often also fall in this broad classification of chemicals.

Consideration of the use of pesticides must balance the benefits versus the possible risks of injury to human health or degradation of environmental quality. Pesticides play a major role in the control of vector-borne diseases, which represent a major threat to the health of large human populations. When introduced in 1942, DDT appeared to hold immense promise of benefit to agriculture and public health by controlling vector-borne diseases. However, because of its bioaccumulation in the environment and its effects on bird reproduction, DDT was eventually banned in most countries by the mid-1970s. When DDT was banned in 1996 in South Africa, less than 10,000 cases of malaria were registered in that country. By 2000, the number of malaria cases had increased to 62,000, but with the reintroduction of DDT at the end of that year, cases were down to 12,500.

Excessive loss of food crops to insects or other pests contributes to economic loss and possible starvation. In developed countries, pesticides allow production of abundant, inexpensive, and attractive fruits and vegetables, as well as grains. Along with insecticides, herbicides and fungicides play a major role in this endeavor.

### Use of Pesticides

In the past 20 years, use of pesticides (as amount of active ingredient) has plateaued. Pesticides are often, if not always, used as multiagent formulations, in which the active ingredient is present together with other ingredients to allow mixing, dilution, application, and stability. These other ingredients are lumped under the term “inert” or “other.” Though they do not have pesticidal action, such inert ingredients may not always be devoid of toxicity; thus, an ongoing task of manufacturers and regulatory agencies is to assure that inert ingredients do not pose any unreasonable risk of adverse health effects.

### Exposure

Exposure to pesticides can occur via the ...

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