Contaminant levels in harbor seals from the northeastern United States

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The concentrations of polychlorinated biphenyls (PCBs), organochlorine pesticides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzofurans (PCDF), polychlorinated dibenzo-p-dioxins (PCDD), and mercury (Hg) were determined in blubber and liver tissues of harbor seals (Phoca vitulina) collected along the northeast coast of the U.S. Average PCB concentrations in seal blubber (sum of congeners) were 12.0 μg/g (wet weight) with a range of 7.30 to 24.3 μg/g in 1980 and 6.66 μg/g (wet weight) with a range of 2.61 to 11.3 μg/g in 1990–1992. Comparisons between blubber data from this study and previous work indicated that the concentration of PCBs along the northeast coast of the U.S. may have decreased over the past twenty years.

The average p,p′-DDE concentrations in seal blubber were 10.9 μg/g (wet weight) in 1980 with a range of 6.95 to 21.9 μg/g and 4.12 μg/g (wet weight) with a range of 1.83 to 7.84 μg/g in 1990–1992. Only trace amounts of PCDFs and PCDDs were found in a few blubber samples; levels in most tissues were below detection (3–5 pg/g) (wet weight). Trace amounts (<30 ng/g) of phenanthracene, anthracene, and alkylated MW-178 compounds were found in some seal samples; all other PAH compounds were below the detection level (5–15 ng/g).

Toxic equivalents (TEQ) of selected coplanar and mono-ortho PCB congeners and relative toxic equivalents (RTE) (pg total TEQ/μg total PCB) were calculated, using recently proposed dioxin toxic equivalent factors (Ahlborg et al. 1994). The TEQs ranged from 41 to 315, and the RTEs ranged from 2.25 to 16.3. The RTEs for seal blubber indicated that the present values were in the midrange of those reported in the literature. Toxic equivalents calculated on the basis of the concentrations of the coplanar PCBs, PCDDs, and PCDFs indicated that coplanar PCBs, rather than PCDDs and PCDFs, may pose a more important toxic threat to harbor seals.

Mercury levels in liver tissue averaged 70.0 μg/g (wet weight) and 44.1 μg/g (wet weight) in the 1991 and 1980 samples, respectively, and are similar to those found in relatively polluted waters of the British Isles.