Mercury and selenium concentrations, and selenium:mercury molar ratios in small cetaceans taken off St. Vincent, West...

This study measured the concentration of total mercury (THg) and selenium (Se), and calculated the Se:Hg molar ratios in the muscle, blubber, liver, and kidney of small cetaceans (false killer whale, Pseudorca crassidens; killer whale, Orcinus orca; Risso's dolphin, Grampus griseus; short-finned pilot whale, Globicephala macrorhynchus; and dolphins of the genus Stenella) taken for human consumption off St. Vincent, West Indies. Overall, 122 samples were analyzed; mean THg concentrations (μg/g dry weight) were highest in the liver (730), followed by the kidney (274), muscle (76.4), and blubber (4.57). To explain variability in muscle THg concentrations, carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope ratios were analyzed to explore differences in dietary carbon source and relative trophic position, respectively, among species. There was no relationship between δ¹⁵N and THg concentration, but there was a positive relationship between δ¹³C and THg concentration. On average for each species, the Se:Hg molar ratios were >1 in blubber and <1 in muscle. All liver samples and the majority of kidney, muscle, and blubber samples exceeded the FAO/WHO human consumption advisory level of 1 μg/g wet weight. Based on our estimations, consuming only 6.6 g of muscle a week would exceed the MeHg provisional tolerable weekly intake of 1.6 μg MeHg/kg body weight/week for a 60 kg person. Given the high THg concentration in these cetaceans and the frequency at which these tissues are consumed, this is a potential human health issue that warrants further investigation.