Hexachlorobenzene in selected marine samples: an environmental perspective

Hexachlorobenzene (HCB) has been designated by the US Environmental Protection Agency as a chemical of interest. Re-examination of previously analysed gas chromatograms and archived samples revealed peaks that co-eluted with the authentic HCB standard. Levels of HCB were less than 1 ng/g in all samples re-examined, and were at least three to four orders of magnitude lower than those of poly-chlorinated biphenyls, two orders of magnitude lower than those of pyrene and one to two orders of magnitude lower than levels of either phenanthrene or benzo[a]-pyrene found in the same mussel samples. Chromatograms of sea water (dissolved and particulate phases) and sediments also revealed very low levels of HCB. Because gas chromatography-mass spectrometry results indicated that levels of HCB were below the level of detection it was not possible to verify its presence. The environmental data on HCB provided by the US Mussel Watch programme demonstrate that HCB levels in mussels are minor compared with other organic compounds such as polychlorinated biphenyls and polycyclic aromatic hydrocarbons (phenanthrene, pyrene and benzo[a]pyrene). Mussels were transplanted to areas affected by industrial activity and by disposal of sewage sludge and dredged materials, and in relatively clean reference sites. Transplanted mussels were used to monitor the marine food chain, as surrogates for other biota in the same areas and as sentinel organisms to monitor localized differences in biologically available chemical compounds. The degree of environmental threat posed by HCB in the marine environment, as indicated by the US Mussel Watch data, is relatively low. It is therefore recommended that a decision be made not to pursue an expanded HCB monitoring programme in the marine environment solely to collect more HCB data.