Mercury in Japan's whale meat.

Whale meat and organs have long been featured ingredients in traditional Japanese dishes. Today, the meat and organs of small cetaceans including whale and dolphin are not as widely eaten, but they are readily available ithroughout Japan. Now scientists have discovered dangerously high levels of mercury in cetacean meat products sold as food there.

The Japanese Ministry of Health, Labour, and Welfare has set the safe level of total mercury at 0.4 parts per million (ppm) for marine foods (the U.S. level is set at 1.0 ppm). Each year, Japan allows more than 22,000 small cetaceans to be legally harvested for food around the coast of Japan, although Naoko Funahashi, Japan's representative for the International Fund for Animal Welfare, estimates the actual catch is around 17,000-19,000.

Toothed whales--including porpoise, dolphin, and some whale species--are top predators in the sea life food chain. These small cetaceans therefore tend to accumulate higher loads of pollutants such as mercury than do filter feeders such as baleen whales.

"The real health problem is that some dolphin meat is being mislabeled as baleen whale meat," says Naomi A. Rose, a marine-mammal scientist with The Humane Society of the United States, a Washington, D.C.-based nonprofit organization opposed to commercial whaling. Most consumers can't distinguish the red steaks of small cetacean meat from those of baleen whale meat. "Whoever is getting those unlucky packages is getting a lot of contaminants," says Rose. "People are playing Russian roulette."

Between 2000 and 2002, a team of scientists led by Tetsuya Endo, a professor in the Department of Clinical Toxicology and Metabolism at the Health Sciences University of Hokkaido, purchased whale meat samples from markets across the country. The researchers measured total mercury levels and performed genetic analysis to verify the species of each sample. Their findings were published in the 15 June 2003 edition of Environmental Science & Technology.

Samples of Dall's porpoise, the most commonly harvested cetacean in Japan, had an average total mercury level of 1.26 ppm, with the highest sample at 2.51 ppm. Samples of false killer whale had an average total mercury level of 46.9 ppm, with a high of 81.0 ppm. Even the levels in baleen whales were high. North Pacific minke whale samples had a total average mercury level of 0.10 ppm. "This shows that pollution levels in the ocean are at such a bad level that even filter feeders are bioaccumulating some kinds of contaminants," says Frank Cipriano, director of the Conservation Genetics Laboratory at San Francisco State University.

Perhaps even more alarming are the results of a separate study in which the team sampled mixtures of boiled internal organs--sold in packages in retail outlets--for total mercury and essential heavy metals. In samples of boiled small cetacean livers purchased between 1999 and 2001, the researchers found an average total mercury level of 370.0 ppm. Two samples had total mercury levels that topped 1,970.0 ppm.

"These levels are a thousand times greater than the worst samples that we get in predatory fish in the United States," says Charles Santerre, an environmental toxicologist at Purdue University. "With a tuna steak, you might get one part per million of mercury. This problem in Japan is in a different league altogether."

In their report, published in the December 2002 issue of The Science of the Total Environment, Endo and colleagues noted that acute mercury intoxication could result from a single meal of whale internal organs, with effects that can include serious nervous system symptoms, staggering, coma, and death. They called on the Japanese government to regulate human consumption of whale and dolphin internal organs.

In 2002, a revised Japanese national law required that all fresh seafood products be labeled with the species name. And on 3 June 2003, based on studies suggesting that fetal exposure to methylmercury could harm the developing nervous system, the Japanese health ministry issued a warning to pregnant women to limit consumption of certain whale products to no more than one 60- to 80-gram serving a week and bottlenose dolphin to no more than once every two months.

But, says Funahashi, "many products still lack a species name, and many have the wrong or false name" (there is no penalty for mislabeling). Furthermore, the Japanese word for whale, kujira, can also mean dolphin or porpoise. Some Japanese media have highlighted the mislabeling problem, so more consumers are aware of it, she says. "But cetacean meat is [no longer] a common food, so it is not a huge concern among the public--yet."