The Japanese scientists bought samples from across the country, and found that every single slice of toothed whale red meat — Japan's most popular whale product — exceeded that country's provisional limit on mercury, with some samples containing almost 200 times the maximum value. The researchers also found that mercury levels were higher in whales caught off the coast of the southern part of the country.

The findings are scheduled to appear in the June 15 edition of Environmental Science & Technology, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society.

"About 17,000 toothed whales are caught annually off the Japanese coast," says Tetsuya Endo, Ph.D., a professor at the Health Sciences University of Hokkaido, Japan, and lead author of the paper. "Despite extreme contamination with mercury, toothed whale products have been sold for human consumption without any regulation."

"These particular meat samples were from packaged food products that someone would have eaten, if they had not been purchased for pollutant analysis," says Frank Cipriano, Ph.D., director of the Conservation Genetics Laboratory at San Francisco State University. "This is a clear signal that Japan has a major health problem that the government has not addressed."

The levels of mercury measured by the scientists are similar to or higher than the levels in fish eaten by people in the Minamata Bay area of Japan, Endo says. The region is well known for its previous problems with mercury. In the 1950s and early 1960s, hundreds of children were born with birth defects caused by their mothers' repeated consumption of contaminated fish.

The Japanese eat less whale meat today than they have historically, largely in response to a 1982 International Whaling Commission moratorium on commercial whaling. Toothed whales, or odontocetes, are not covered under the moratorium. Demand for these species — a suborder of aquatic mammals that includes dolphins, porpoises, killer whales and pilot whales — has therefore increased in Japan as larger whales have become harder to obtain, Endo says.

About 40 percent of all whale products marketed in Japan are from toothed whales, according to the Institute of Cetacean Research. This meat is eaten mostly in coastal fishing villages, but also in metropolitan areas around the country. Whale meat is not sold for human consumption in the United States.

Between 2000 and 2002, Endo and his colleagues purchased whale meat in towns across Japan — from tiny fishing villages to Tokyo. They measured total mercury levels in the samples and did a genetic analysis to verify the species of each whale.

The researchers analyzed 137 meat samples in all and found that every one exceeded the provisional mercury level set by the Japanese Ministry of Health, which is 0.4 parts per million (ppm). Out of nine different whale species identified, the lowest average mercury level was 1.26 ppm and the highest was 46.9 ppm, with the majority of species ranging from 5-10 ppm.

The two highest mercury levels in individual samples were found in a false killer whale (81 ppm) and a striped dolphin (63.4 ppm). Nago, the southernmost of the six regions studied, had the highest average concentration, and levels decreased steadily moving northward.

The effect of eating mercury-tainted meat on people in Japan is not well studied, but a 1997 survey in the Faroe Islands revealed neurological problems in children whose mothers ate whale meat frequently. Mercury levels in most of the toothed whale samples from the current study are higher than levels in pilot whales from the Faroe Islands, according to the researchers.

In another study published earlier this year, Endo and his colleagues found that rats developed kidney disorders when they ate whale organs contaminated with mercury. They plan to examine the Japanese population in the future to determine the effects of mercury contamination.

Mercury enters the environment naturally and through industrial pollution. Nearly all fish contain trace amounts of mercury, but longer-lived predators — like odontocetes, tuna and sharks — are the final repositories for many pollutants because of their position at the top of the food chain.

Endo reported the current findings at a meeting of the Food Hygiene Society of Japan in Tokyo last week.

The International Fund for Animal Welfare provided support for this study.

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