Pesticides and Human Health

Abstract

Chemical pesticides when used properly have been of tremendous benefit to man and his environment especially in developing countries, where they are used to eradicate insectborne, endemic diseases, to produce adequate food and protect forests, plantation and fibers. Presently, more than 2.5 million tons of pesticides valued over US $30 billion are being used in cultivation alone all over the world. The Rachel Carson’s “Silent Spring” (Carson, 1962), awakened the public to the potentially “disastrous” effect of chemical pesticides on human and the environment. “Silent Spring” heralded the start of the U.S. environment movement in which a number of biologists and ecologists all echoed the same basic view that planet earth was a finite entity and that man and the whole global biosphere were doomed unless immediate action was taken to reign-in what was considered a runaway technology. When pesticides misused or used carelessly they have caused considerable harm. The risk or hazards of using chemical pesticides have increased in recent years with the sharp rise in their consumption by agriculture, industry, householders, and government. Pesticides lead to over three million poisoning cases annually and up to 220,000 deaths, primarily in developing countries. Pesticides may present immediate danger to the user if applied improperly or without sufficient knowledge of their toxic effects. Some are highly toxic and may cause serious illness and even death if spilled on the skin, inhaled, or otherwise used carelessly. In addition, potential future hazard to human health and wildlife can be created by residues from some long-lived pesticides that may build up in the food chain and cause widespread contamination of the environment. The risk is defined as a measure of the probability that an adverse effect will occur (Wilkinson, 1986). In the case of a chemical, it is a function of the intrinsic capacity of the material to cause an adverse effect (acute toxicity, neurotoxicity, cancer, etc.) and the dose, which is usually determined by the intensity, frequency, or duration of exposure. Risk assessment is the process by which estimates of risk to humans from exposure to potentially toxic agents are extrapolated from existing data, usually generated from laboratory animals (National Research Council [NRC, 1983]). Strauss (1991) divided the risk assessment into 4 components: hazard identification, exposure assessment, dose-response assessment and risk characterization (Fig. 1). The aim of the assessment of human exposure to pesticides is the identification of doseeffect relationships in man after both single and/or repeated exposures and also the methods for prevention of such adverse effects due to these chemicals. According to the circumstances, size of dose, and methods of assessment, human exposures might be divided