Alkyl mercury poisoning in terrestrial Swedish wildlife

Abstract

Systematic examinations have revealed widepread mercury poisoning in Swedish terrestrial fauna since the middle of the 1950s. Of 253 seed-eating birds found dead, 48 percent had mercury levels above 2 mg/kg (liver), 30 percent above 5 mg/kg, 20 percent above 10 mg/kg and 13 percent more than 20 mg/kg. Similar results were obtained for predatory birds, though levels overall were significantly higher. Mercury poisoning was demonstrated in some mammalian predators. Residue levels were negligible in grazing mammals. Methylmercury accounted for the majority of mercury content in the majority of samples. Strong correlations between samples taken in the wild and those taken in laboratory experiments were noted. The study's conclusion is that alkyl-mercury dressed seed is the main source of mercury contamination in Swedish terrestrial ecosystems.