Mercury contamination and human exposure through inland fishery and aquaculture products in Northeastern Brazil.

The exponential growth of inland fisheries and aquaculture in Northeastern Brazil requires permanent monitoring of the quality of their products, particularly regarding persistent globally distributed pollutants such as mercury (Hg). This is the first survey on Hg concentrations in inland fishery and aquaculture products from the region. This survey includes an inventory of Hg concentrations vis-à-vis compliance with national and international food safety guidelines and an evaluation of Hg exposure risk from fishery and aquaculture products consumption. Mercury concentrations were quantified in 14 fish species, representing the regional inland fisheries and including the main aquaculture product, the Tilapia (Oreochromis niloticus). Overall, concentrations were very low and well below the established threshold for human and environmental health protection. As expected, concentrations were higher in carnivorous species, such as Serrasalmus rhombeus (Piranha) from fluvial systems. We found an important pattern of Hg accumulation in farmed Tilapia, where market-size fish presented lower Hg concentrations than juveniles. This pattern likely reflects accelerated growth under intensive feeding conditions, resulting in dilution of Hg within rapidly increasing biomass. Estimates of Hg ingestion by fish consumers indicate very low exposure risk, even for high consumption scenarios, suggesting that consumption of these fishery and aquaculture products is safe with respect to Hg exposure.