Chlordane biota

Heptachlor and cw-chlordane, both of which are chiral, produce caged or half-caged structures (Figure 1.8) on irradiation, and these products have been identified in biota from the Baltic, the Arctic, and the Antarctic (Buser and Muller 1993). 

Although technical chlordane is a mixture of compounds, two metabolites — heptachlor epoxide and oxychlordane — can kill birds when administered through the diet (Blus et al. 1983). These two metabolites originate from biological and physical breakdown of chlordanes in the environment, or from metabolism after ingestion. Heptachlor can result from breakdown of cis- and trans-chlordane, eventually oxidizing to heptachlor epoxide oxychlordane can result from the breakdown of heptachlor, m-chlordane, tra .s-chlordane, or fram-nonachlor (Blus et al. 1983). Heptachlor epoxide has been identified in soil, crops, and aquatic biota, but its presence is usually associated with the use of heptachlor, not technical chlordane — which also contains some heptachlor (NRCC 1975). Various components in technical chlordane may inhibit the formation of heptachlor epoxide or accelerate the decomposition of the epoxide, but the actual mechanisms are unclear (NRCC 1975). 

Wood, L.W., P.A. Jones, and A. Richards. 1986. Possible sediment scavenging of chlordane and contamination of the aquatic biota in Belmont Lake, New York. Bull. Environ. Contam. Toxicol. 36 159-167. 

Concentrations of Chlordanes, DDTs, PCBs and PBDEs, on a dry weight basis (dw), are summarized for the 15 species common to both sites in Fig. 15.17. Higher concentrations of PCBs and PBDEs were generally found in biota from S. Khatib Bongsu and Chlordanes in biota from S. Buloh. However, the differences between the two sites are generally less than three standard deviations and are not significant. 

Figure 15.20. Chlordane profiles in mangrove biota samples collected in Singapore. M muscle L liver E eggs.

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. 

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