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HISTORY AND EPIDEMIOLOGY

The proper use of pesticides has a beneficial role in human health by increasing the quality and quantity of crops. Alternatively, acute and chronic pesticide poisoning are significant causes of morbidity and mortality worldwide, especially in developing countries, making pesticide poisoning a global public health problem.78,191

Fumigants are nonspecific pesticides applied to kill and control rodents, nematodes, insects, weed seeds, and fungi anywhere in soil, in structures, crops, grains, and commodities.37 They represent a diverse group of pesticides that are dissimilar in their chemical structures, physical properties, and mechanisms of toxicity (Tables 108–1 and 108–2). Many fumigants, particularly the halogenated solvents, have been largely abandoned because of their toxicity. In the 1987 Montreal Protocol, an international agreement was adopted to phase out ozone-depleting chemicals, such as methyl bromide, which was scheduled to be discontinued in 2005. Unfortunately, many agricultural companies received exemptions, as satisfactory substitutes for some of methyl bromide uses have not emerged.

TABLE 108–1Physical Properties and Industrial Uses of Fumigants
TABLE 108–2Comparison of Clinical Effects of Fumigants

Because fumigants exist as solids that release toxic gases on reacting with water (zinc phosphide, aluminum phosphide) or with acids (sodium or calcium cyanide), as liquids (ethylene dibromide, dibromochloropropane, formaldehyde) that can vaporize at ambient temperature, or as gases (methyl bromide, hydrogen cyanide, ethylene oxide), inhalation is the most common route of exposure (Table 108–1). In their gaseous forms, fumigants are generally heavier than air and will be found concentrated just above the ground surface and lower floors of buildings.

Their exposure risk is enhanced by their general lack of warning properties, non–species-selective effects, and high potency. Although xenobiotics from many different chemical classes were used in the past as fumigants, only a few remain in use today in the ...

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