Toxaphene biota

Bioconcentration factor (BCF) for toxaphene and selected species of aquatic biota... 

Toxaphene is extremely toxic to freshwater and marine biota. In laboratory tests of 96-h duration, 50% mortality was recorded for the most sensitive species of freshwater and marine teleosts, marine crustaceans, and freshwater insects at nominal water concentrations of less than 10 pg/L of toxaphene, and, in several cases, less than 1 pg/L (Table 27.2). Bioassays of longer duration, based on exposure of aquatic organisms for the entire or most of the life cycle, produced significant adverse effects on growth, survival, and reproduction at toxaphene concentrations between 0.025 and 1.0 pg/L (Table 27.3). Toxaphene was most toxic to freshwater fishes in soft water at elevated temperatures (Saleh 1991). Based on its high toxicity and extensive use, it is not surprising that toxaphene was considered a major cause of nationwide fish kills in 1977 (USEPA 1980b). 

Table 27.5 Sublethal Effects of Toxaphene to Aquatic Biota... 

Table 27.6 Bioconcentration Factors (BCF) for Toxaphene and Selected Species of Aquatic Biota... 

Toxaphene causes death and deleterious effects to nontarget aquatic biota at extremely low concentrations (i.e., <1.0 pg/L). 

Effects of Lipid, Size and Season on Toxaphene Levels in Biota. 249... 

Another major exposure route for humans is via contaminated food. For example, North America s Great Lakes, which are the largest body of freshwater in the world, are polluted with about 362 contaminants that were found in quantifiable amounts in the water, sediment, and biota (IJC 1983 USEPA 1994). The critical pollutants were identified as PCBs, DDT, dieldrin, toxaphene, mirex, methyl mercury, benzofa) pyrene, hexachlorobenzene, polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and alkylated lead. Some of these pollutants biomagnify in the aquatic food chain and can be detected in increased levels in cooked Great Lakes fish. Consequently, the blood serum levels of these chemicals are significantly increased in consumers of contaminated Great Lakes sport fish compared to people who do not eat such fish (Flumphrey 1983 Fiore et al. 1989 Sonzogni et al. 1991). 

Keywords, toxaphene, chlorobornane, nomenclature, identification, separation, toxicity, congener-specific, biota, sediment. 

In 1973, variant (i) was introduced by Khalifa et al. and the year after three reports were published which described the isolation and structure elucidation of single components from technical toxaphene [54, 78, 91]. These initial studies focused on the isolation and structure elucidation of the major components in the technical mixture. However, it turned out that the isolated components were easily degraded in biota. Nevertheless, this approach revealed interesting results such as the presence of dihydrocamphenes in toxaphene [43,44] and the isolation of a non-racemic component from the technical product Melipax [27]. 

The question about the fate of toxaphene in the environment cannot be answered in a simple way. In the environment, only some toxaphene components remain unmetabolized and are accumulated in biota. This leads to a simpler toxaphene residue pattern compared to the technical mixture. In 1979, Saleh et al. studied the metabolism of B7-515 (P-32) and technical toxaphene with seven test animals. Both were metabolized the least in chicken and the most in monkeys [175]. Furthermore, the major toxaphene congeners present in the technical mixture are not the same as those found in environmental samples due to selective bioaccumulation/metabolization and abiotic degradation mechanisms (see Table 6). 

Buser and Muller found B8-1413 (P-26), B9-1679 (P-50), and six further chlo-robornanes (TCI, TC2, TC5-TC8) in penguin tissue [120], TC8, tentatively identified as B8-806/B8-809 (P-42), was present in low amounts [120], Some of the other components may be B8-1412, B8-1414 (P-40), B8-1945 (P-41), B8-2229 (P-44), which have been identified in the same matrix [100]. Usually, in biota from the top level of the food chain B8-1413 (P-26) and B9-1679 (P-50) were most abundant. In addition, the number of toxaphene peaks decreased with increasing trophic level. The results obtained so far can be summarized as follows. Most of the toxaphene components are degradable, and only a few persistent congeners are accumulated in higher organisms. 

The degradation of toxaphene is less pronounced in water and air than in biota. Due to the many more components present in air and water, co-elutions may oc-... 

Along with the identification of an increasing number of toxaphene components persistent in the environment, the elucidation of the mechanisms leading to biodegradation or bio accumulation of the components has gained in interest. As mentioned before, the dominating toxaphene components in sediment are not identical with those in marine biota. 

The two principal components of toxaphene congeners isolated from biota (Stern et al. 1992) aH NMR showed these to be octachloro and nanochloro congeners both of which display chirality although the enantiomers were not resolved in this study (Figure 2.3). 

Stern, G.A., D.C.G. Muir, C.A. Ford, N.R Grift, E. Dewailly, T.F. Bidleman, and M.D. Walla. 1992. Isolation and identification of two major recalcitrant toxaphene congeners in aquatic biota. Environ. Sci. Technol. 26 1838-1840. 

It should be also noted that considerable attention has been directed to the highly toxic polychlorinated bornanes (toxaphene) and derivatives of hexachlorocyclopentadiene (chlordane) that were used as pesticides. Chlor-dane has been recovered from biota (Buser et al. 1992), and toxaphene components from sediments (Stem et al. 1996), so that these are highly persistent contaminants. For both, the commercial products contained a large number of congeners, and the analysis of chlordane is complicated additionally by the occurrence of enantiomers, some of which have undergone degradation and transformation after discharge. Nevertheless, only limited attention appears to have been directed to waste from locations at which these products were manufactured. 

---