Issues > Mercury in Seafood

Mercury is released into the air from the burning of fossil fuels and industrial pollution. When it falls back to earth, usually through rain, mercury accumulates in streams and oceans where water turns it into methylmercury, the element most harmful to humans. Methylmercury, or mercury for the purposes of this discussion, is also present in nearly all fish and shellfish according to the FDA.1

How does mercury affect us?

Larger fish have the highest levels of mercury because they have lived longer and have had more time to accumulate it. Although risk to human health is relative to size, it is also largely dictated by ranking on the food chain. In general predatory fish (shark, swordfish, mackerel, tuna) are more toxic because of the overall amount of mercury they have consumed through smaller fish.

Mercury is toxic to everyone, but the concern is greatest for young children and unborn babies whose nervous systems are still developing. Because methylmercury accumulates in the bloodstream over time it will be present in women even before they become pregnant. It can take years for the levels to drop significantly, which is why young women and women trying to become pregnant should be cautious about their fish intake.

The world discovered mercury poisoning in the 1950’s when an epidemic hit fishermen and their families in the small Japanese fishing village of Minimata. An industrial plant was discharging mercury into Minimata Bay and the effects nearly crippled the town’s population. Brain damage, retardation, and birth defects were rampant. When authorities took action to eliminate the source of pollution, mercury levels eventually dropped and the fish were safe to eat.

1 U.S. Food and Drug Administration.

Mercury in Japan

The Japanese guideline for mercury in seafood is 0.4 parts per million. In 2010, the National Institute for Minimata Disease tested 1,137 residents of Taiji, the Japanese town featured in The Cove and found mercury levels 10 times the national average. Men averaged 11.0 parts per million (ppm) and women 6.63 ppm. In fourteen locations outside Taiji average levels were considerably lower, 2.47 ppm for men and 1.64 ppm for women, though still higher than recommended. Although testing methods have been criticized the research has raised important issues for this coastal community.1

High levels of mercury in Japanese seafood are not a new phenomenon. From 2000 to 2002 scientists from the Health Sciences University of Hokkaido sampled commercial grade dolphin and whale meat. They found excessive levels of mercury in each of the 137 meats sampled – at least two species had mercury concentrations 160 to 200 times above the limit.2

In 2008 the New York Times declared “mercury does not seem to be a high priority for [Japanese] officials.” The government has no restrictions on mercury in tuna, one of the largest fish, known to have higher levels of mercury. A survey by the Health Ministry in 2005 found that the highest concentrations of mercury in Japanese tuna were more than 15 times the limit for other types of seafood.3

The statistics are not surprising considering there has been a systemic suppression of mercury-related information by the Japanese government and fishing industries over the last several decades. Local government in Taiji still claim that dolphin hunting and dolphin meat are a way of life, which remains true for a small percentage of the population who do not have access to information regarding the health risks and consequences of mercury intake. The reality is that the demand for dolphin and whale meat (which have higher mercury levels) has dropped significantly due to international stigma and a growing awareness of toxicity levels.

A movement away from consumption of large cetaceans (dolphins and whales) is taking hold, particularly with Japanese youth, but overall fish consumption shows no signs of slowing. Japan already imports 60 percent of its food and can ill afford to import any more.4  As long as the sea and its abundance remain an available resource, fish and the mercury in them will present a problem for Japan.

The Cove's success

Although dolphin meat is known to be toxic, it was served at mandatory school lunch to Japanese children.When this was revealed to the world in The Cove, the practice was discontinued. OPS is proud that thousands of school children will no longer be fed toxic meat and views this as a great victory and evidence of the power of film.

1 Minoru Matsutani. Most Taiji residents rest easy, refuse to change diet. The Japan Times. May 10, 2010.
2 Sarah Graham. Packaged whale meat in Japan contains high levels of mercury. The Scientific American. May 20, 2003.
3 The New York Times. For Japanese, mercury in tuna not a big concern. January 27, 2008.
4 Kazuaki Nagata. Japan needs imports to keep itself fed. The Japan Times. February 26, 2008.

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