Heavy metals and selenium in stranded dolphins of the northern Tyrrhenian (NW Mediterranean)

Heavy metal (Hg, Cd, Pb and Zn) and selenium levels were determined in striped (Stenella coeruleoalba) and bottle-nosed dolphins (Tursiops truncatus) stranded along the coast of Tuscany and Latium, Italy in the period 1987-1989. Lead and zinc concentrations were quite low and there was modest accumulation of cadmium in the kidney of both species. Mercury levels were very high, especially in the liver where they reached peaks of 4400 ppm (dry weight) in the striped dolphin and 13,150 ppm (dry weight) in the bottle-nosed dolphin. Selenium levels were also high and were significantly correlated with mercury levels in some organs and tissues. The toxicological significance of the selenium-mercury interaction is discussed.