Fate and effects of diazinon.

Diazinon use has significantly increased since its introduction more than four decades ago. Thus, today we are faced with environmental and health consequences that are largely inseparable from the insecticide's benefits. Fortunately, the research to date is of immeasurable value in making sound scientific and policy decisions regarding diazinon use. Overall, research shows that diazinon is globally widespread, having distributed to all environmental media. Residential uses, and its ubiquity under many farming practices, contribute to extensive non-point-source pollution. In general, diazinon is degraded fairly rapidly in natural settings, although results have been variable and some degradation products are at least as toxic as the parent compound. Diazinon exhibits high acute toxicity to a wide variety of animals, leading to a wide range of sublethal biochemical effects, damage to specific target organs and tissues, cytotoxic and genotoxic effects, reproductive damage, and adverse ecological impacts. Its biological fate is complex, mediated largely by diverse metabolic mechanisms. Further research and monitoring are needed in a number of areas. For instance, it is important to develop a better understanding of the mechanism of diazinon's highly lethal effects on birds. Use restrictions at golf courses and sod farms are a welcome step, but there are still widespread avian exposures from orchards and lawns. Continued diazinon use at current rates also poses a clear threat to aquatic ecosystems and to important species such as salmon and bluegill sunfish. Although the research presented here does not indicate threats to humans from the pesticide, Wright (1990) suggests that people may be at substantial risk in unregulated settings. Further research is also needed to resolve the matter of the potential carcinogenicity of diazinon. As with all pesticides, diazinon use can result in the so-called pesticide treadmill wherein pesticide use necessitates further use as insects develop resistance and natural predators are eliminated (Gliessman 1998). It is critical that all pesticides be used with great care to minimize this consequence to avoid a repeat the occurrence in 1965 in the Culiacán Valley of Mexico. There, excessive pesticide use resulted in cotton pests that were resistant to all available insecticides, forcing growers to entirely abandon production (Wright 1990). However, used carefully, diazinon represents a powerful agricultural tool available to assist in the continued production of foodstuffs for a rapidly growing world population.