RESUMO
Evaluates the risks to human health and the environment posed by exposure to alpha- and beta-hexachlorocyclohexanes (HCH). These two isomers are by-products in the manufacturing of lindane, and may be present in this pesticide as impurities. Alpha- and beta-HCH are also present in technical-grade HCH, which is used in agriculture and wood protection. Most environmental releases are linked to the use of technical-grade HCH and to the inappropriate disposal of residues produced when lindane is purified. Alpha- and beta-HCH are evaluated in separate monographs, which cover sources of human and environmental exposure, levels detected in different environmental media, behaviour in the environment, metabolic fate in different organisms, and toxic effects on experimental animals, humans, and plant and animal species. Both isomers are noted to be universal environmental contaminants, with concentrations detected in samples of air, rain water, fresh water, sea water, soil, sediment, and numerous plant and animal species, as well as in several important food items. A review of studies on environmental behaviour and metabolic fate concludes that alpha- and beta-HCH, when compared with lindane, are characterized by a higher bioconcentration in the environment, a slower rate of biodegradation by ultraviolet light, and a slower rate of elimination from organisms. Concerning sources of human exposure, studies show that, in industrialized countries, more than 90% of human intake occurs through the consumption of contaminated food, with the highest concentrations found in fat-containing food items. Current exposures via food are judged to be low and gradually decreasing, supporting the conclusion that these isomers pose no serious health threat to the general public. A review of findings from toxicity studies in laboratory animals identifies growth retardation and effects on the liver and kidney as the major consequences of acute exposure. Although a neoplastic response was observed in some studies, the report concludes that this response is most likely due to a non-genotoxic mechanism. In its concluding section, the report expresses serious concern over the widespread pollution of the environment with these isomers. As neither has any insecticidal action, the report concludes that use of technical-grade HCH products containing high concentrations of alpha- and beta-HCH is never justified
Assuntos
Hexaclorocicloexano , Exposição Ambiental , Poluentes AmbientaisRESUMO
Evaluates the risks to human health and the environment posed by lindane, an isomer of hexachlorocyclohexane used, for more than four decades, as a broad-spectrum insecticide. Although most lindane is used in agriculture for the treatment of seeds and soils, other important applications include the protection of wood and timber, the treatment of veterinary ectoparasites, and the treatment of scabies and body lice in humans. Concerning sources and levels of human exposure, the report cites residues in food as responsible for more than 90% of human exposure, noting that populations throughout the world are exposed to lindane on a daily basis. From the large number of studies that have measured levels in food, the report is able to conclude that such exposures are already below the acceptable daily intake and are gradually decreasing. The assessment of effects on human health benefits from the large number of recent, well-designed studies conducted in both experimental test systems and a range of different laboratory species and strains. These studies support the conclusion that dietary intake of lindane, at currently measured levels, will not impair the health of the general population, nursing infants, or toddlers. Citing evidence from well-designed studies of exposed workers, the report further concludes that, under normal conditions of use, lindane poses no short- or long-term threats to the health of workers. Reports of severe toxic symptoms following the use of lindane to treat scabies underscore the need for strict adherence to prescribed doses, especially when treating children. Concerning risks to organisms in the environment, the report notes that lindane, even when applied at recommended rates, is highly toxic for bats and should thus be regarded as a major environmental hazard wherever bats might roost on lindane-treated wood
