Current and historical nephric and hepatic mercury concentrations in terrestrial mammals in Poland and other European countries.

The long-term anthropogenic release of mercury (Hg) into the environment has led to contamination of the biosphere, with all forms of Hg showing toxic effects and the ability to accumulate in organisms. Since the 1970s, efforts have been made in Western Europe to reduce Hg emissions and for the economic use of Hg, leading to a reduction in Hg exposure to humans and entire ecosystems. The purpose of this research was to present the total mercury (THg) burden in three mustelids (the piscivorous Eurasian otter and American mink, and the invertebrativorous European badger) inhabiting north-western Poland (mostly floodplains) and other European countries (literature data). Moreover, we wanted to investigate whether reductions in the environmental Hg burden in Europe have resulted in reductions in liver and kidney levels in wild terrestrial mammals (Eurasian otter, wild boar, red deer, roe deer, cervids, leporids, rodents, and ecotrophic groups: piscivorous mustelids, non-mustelids whose diets include aquatic prey, canids and other carnivores, omnivores, herbivores), between samples collected before and after 2000. We revealed significantly higher nephric THg levels in roadkilled than in trapped American minks. As roadkilled piscivorous mustelids from the same floodplain had similar hepatic and nephric THg concentrations, we suggest that the European research on Hg ecotoxicology should more often use alien American mink instead of the protected Eurasian otter. Badgers inhabiting Polish and other European floodplains bioaccumulated higher amounts of THg than those from other areas, and as such, may be recommended as bioindicator of mercury soil contamination. Our analysis of abundant data on mammalian hepatic and nephric THg concentrations (excluding non-piscivores mustelids) showed that in 12 of 21 cases, Hg concentrations had dropped significantly since 2000. This data signals a reduction in Hg contamination in terrestrial mammals, such as the Eurasian otter, and may be reason for cautious optimism.