Organochlorine accumulation on a highly consumed bivalve (Scrobicularia plana) and its main implications for human health

摘要

Contamination by polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) was investigated along aspatial gradient in water, sediments and in commercially important bivalve species Scrobicularia plana, fromRia de Aveiro (Portugal). Organochlorines dissolved in water were below detection limit and concerningsuspended particulate matter, only PCBs were quantified, ranging from 3.8 to 5.8 ng ∙ g−1 DW (Σ13PCBs).There was a distinct spatial gradient regarding PCB accumulation in sediments. The highest concentrationswere found in deeper layers and closest to the pollution source, decreasing gradually along a 3 km area. Contaminationin sediments exceeded the Canadian and Norwegian sediment quality guidelines, inducing potentialtoxic effects in related biota. PCBs tended to bioaccumulate throughout S. plana lifespan but with differentannual rates along the spatial gradient. The maximum values were found in older individuals up to 3+ yearsold, reaching 19.4 ng ∙ g−1 DW. HCB concentrations were residual and no bioaccumulation pattern was evident.Congeners 138, 153 and 180 were the most accumulated due to their abundance and long-term persistencein the environment. In the inner area of the Laranjo Bay (0.6 km2), the species was able to remove up to0.4 g of PCBs annually from sediments into their own tissues, which is consequently free for trophic transfer(biomagnification). Concerning human health, and despite the high concentrations found in sediments, PCBlevels in bivalves do not exceed the limit established by the European Union for fishery products and arelargely below tolerable daily intake. Although PCBs in Scrobicularia plana are present at low levels, theirimpact to human health after consumption over many years might be harmful and should be monitored infuture studies.