PCDD/PCDF sediment concentration distribution: Casco Bay, Maine, USA

A comprehensive evaluation of sediment quality in Casco Bay for 2,3,7,8-polychlorinated dibenzo-p-dioxins and 2,3,7,8-polychlorinateddibenzofurans (PCDD/PCDF) was undertaken by the analyses of 30 sediment samples. PCDD/PCDF were detected in sediments from all areas of Casco Bay. The concentrations were highest near potential input sources. For example, PCDD/PCDF and especially 2,3,7,8-tetrachloro-p-dioxin and 2,3,7,8,-tetrachlorodibenzofurans (TCDD/TCDF) had higher concentrations near the Presumpscot River sites, 10 miles down stream of a pulp and paper mill. There are also exceptions, for example the higher PCDD/PCDF concentrations in East Bay are not near known point sources, but may be the result of transport into the bay from sources in the Kennebec/Androscoggin River or localized combustion sources. The concentrations of PCDD/PCDF found in Casco Bay sediments are in the range expected when compared to similar estuarine areas. In spite of the low concentration in sediment, detection of 2,3,7,8-TCDD/TCDF in lobster tissue and tomalley indicate these compounds are bioavailable, and have resulted in an advisory regarding consumption of lobster tomalley from Casco Bay(1).