14 - Pesticides

Abstract

This chapter discusses pesticides, which are toxic chemicals that are deliberately introduced into the environment for the sole purpose of killing living organisms. Sources of human exposure to pesticides include agricultural application, commercial and home building disinfection, garden use, golf course and lawn use, manufacturing wastes, misuse, and handling accidents. Pesticide residues are present in foods and contaminated drinking water. Many are volatile and result in exposure upon breathing. Different classes of pesticides poison through different mechanisms. A representative profile list of the different chemical classes of pesticides, their modes of absorption, toxicities to humans, symptoms of exposure, pesticide uses, and exemplar compounds is provided. Pesticides are often applied in mixtures. Mixtures of herbicides, fungicides, and pesticides are applied to corn, cotton, lettuce, and fruit crops. As a result, pesticides are widely present in the environment as mixtures. The toxic effects of some pesticide mixtures are additive, particularly when their toxic mechanisms are identical. Exposures to mixtures of different classes of pesticides produce effects that are often difficult to anticipate. Pesticide mixture exposure has been linked to parental infertility, spontaneous abortion, preterm delivery, and congenital abnormalities. The inert components of pesticides can contribute to their absorption by humans by facilitating the transport of pesticides through protective clothing. Exposures to low levels of pesticides are those that occur when toxic effects are observed following inhalation, ingestion, or dermal absorption of concentrations not known to be toxic. The toxicities of the pesticides also increased very significantly with exposure durations.