About a dozen melon-headed whales that recently beached in Chiba Prefecture, Japan and subsequently died, had mercury concentrations some 10 times higher than the level the government considers acceptable, a study recently showed.

Tetsuya Endo, a lecturer at the Health Sciences University of Hokkaido, said the high concentration of mercury was detected in the whales' muscle tissue.It has been widely known that dolphins and whales tend to accumulate
high levels of mercury through the food chain because of their long life span. Some short-finned pilot whales, which are eaten in parts of Japan, are known to contain high levels of mercury.

Examinations of the beached melon-headed whales, a species for which data
have been unavailable, show they also can contain high levels of mercury.Endo and other researchers measured the total amount of mercury in the muscle, liver and kidneys of more than 10 carcasses and detected an average of 4.5 mg of mercury per kilogram of muscle, far higher than the 0.4
mg the government considers normal. The highest level was 11.0 mg, they said.

The researchers detected an average of 119 mg of mercury in the whales' livers and 6.3 mg in the kidneys.

source: Japan Times