Toxaphene: chemistry, biochemistry, toxicity and environmental fate

The chemistry of toxaphene is now well developed; 20 isomers have been isolated and identified. The molecular weight and molecular formula are known for the remaining major components. The major metabolic degradation mechanisms for toxaphene in all organisms from bacteria to primates are now believed to the reductive dechlorination, reductive dehydrochlorination, and in some cases, oxidative dechlorination to produce hydroxyl derivatives, acids or ketones. Earlier reports that toxaphene was biodegradable were published before the advent of state-of-the-art analytical methodology which has permitted detection at levels in the range of ppb. Toxaphene residues have recently been documented throughout the biosphere as well as in human milk, even though its use was banned in 1982. This global persistence is against previous beliefs that toxaphene was easily biodegradable. During the last decade advances have been achieved in the selectivity, accuracy, and sensitivity of detection techniques so that the presence of toxaphene throughout the biosphere has been extensively documented. Through the use of GC/MS and electron capture GC, toxaphene can now be detected at ppb levels, making possible a more consistent and accurate assessment of the compound's presence in organisms as well as in soil, water, and ground water. Toxaphene residues have been detected in human populations, fish and wildlife, soil, water, and ground water as well as in food. An FDA Food Survey study found residues of toxaphene exceeding regulatory limits in only 1% of the 14,492 food samples. Toxaphene was reported to be among the most frequently occurring residues found in total dietary foods for the period 1982-84. It was found 48 times based on two food consumption surveys, a level higher than the frequency of DDT, DCPA, pentachloroaniline, and methoxychlor. Toxaphene has been detected in two large, pooled samples of human milk collected from mothers living in Uppsala and Stockholm at a concentration of 0.1 mg/kg of milk fat. Accumulation of toxaphene occurs in water in areas where the insecticide is in use, and it may be quite persistent. In some Canadian lakes it was found in toxic concentrations up to five yr after fish have been killed. Several studies have documented the presence of toxaphene in rain water, e.g. 9 ng/L in rain samples from Lake Michigan. It is now clear that toxaphene is a global pollutant like DDT, PCBs, and other organochlorines. Toxaphene is persistent in soils and lake sediments and has been found in fish, in the ringed seal, in rain water, and in human milk.(ABSTRACT TRUNCATED AT 400 WORDS)