Dolphin and porpoise meat is widely and illegally sold in Japan as whalemeat and all three foods are so riddled with mercury that just a tiny meal could exceed safety levels, a study said on Wednesday.
"Contaminated cetacean (whale, dolphin and porpoise) products are widely available in Japan's retail outlets," according to the report, conducted by a British-based environmental watchdog which made seafood purchases in stores across Japan and then had them analysed for toxicity and genetic ID.
"Furthermore, the government of Japan has been aware of this very real health risk for more than 20 years," it says.
The study, "Mercury Rising", is written by the Environmental Investigation Agency (EIA), a small group that specialises in using undercover techniques to expose environmental abuse.
Its latest research is timed to coincide with a meeting, running from June 16 to 19 in Berlin of the International Whaling Commission (IWC), where Japan is expected to relaunch its attempt to end a 1986 global moratorium on commercial whaling.
Japan has sidestepped the IWC ban by hunting four species of large whale - North Pacific minkes, Bryde's, sei and sperm whales - supposedly for scientific research.
It also allows a catch of more than 22,000 smaller cetaceans, from nine dolphin, porpoise and small whale species, each year.