Sharks high in mercury

By the Sea Shepherd Conservation Society

Tests conducted by a variety of organisations over the last couple of years have shown that mercury levels in shark fins frequently exceed World Health Organisation (WHO) limits.

The acceptable limit of mercury content in food products, as set by the WHO, is 0.5 mg/kg. However, tests commissioned in Thailand and Hong Kong by WildAid have shown that mercury concentrations in shark fin can reach 42 times this limit.

A test conducted by WildAid in Thailand in 2001 showed that 70% of the fins exceeded the safety limit. A more recent test conducted in 2002 by WildAid had one third of the sample fins having excessive mercury with one fin surpassing the limit by as much as 7 times.

The latest evidence comes from another independent test conducted this year (2002) by Doctor Choi of the Prince of Wales Hospital and Chinese University. In Dr. Choi’s test, 60% of the shark fins in the sample had excessive mercury.

What is mercury?

Mercury is a highly toxic metal. It is released by both natural and man-made processes. Although it occurs naturally, human activities have greatly increased its concentration in the environment. The vast quantities of sewage, waste material, heavy metals and industrial pollutants being dumped into the oceans every year increase the concentrations of mercury in the sea water.

It is estimated that man-made emissions have tripled mercury concentrations in the surface of the ocean since 1900. Incinerators, coal burning facilities and certain industrial processes presently account for about 75% of worldwide mercury emissions.

Why do sharks accumulate mercury?

When mercury becomes deposited within a water body, microorganisms can transform it into a very toxic substance known as methyl mercury. Methyl mercury can accumulate in the tissues of fish to concentrations much higher than in the surrounding water.

Methyl mercury binds strongly to proteins in the body of fish and humans and is depurated very slowly. The depuration of mercury from an organism depends primarily on its metabolic rate; the larger the organism, the slower its metabolism and thus the higher level of mercury.

Sharks accumulate a high level of mercury in their flesh due to the fact that they have a long lifespan and they are the top predators of the seas. And the bigger and older the shark, the more likely it is to have high levels of mercury in its tissues.

Is it just sharks that are affected?

Any form of wildlife that consume large amounts of fish are at risk of developing mercury poisoning. Besides sharks, bald eagles, loons, kingfishers, minks, and trout also prey heavily upon fish and are very susceptible to mercury poisoning. While relatively little information exists on mercury poisoning in wildlife, especially chronic symptoms, it is believed that serious nervous system and reproductive disorders are occurring in some populations of fish-eating birds and mammals.

What are the effects of mercury on human health?

Mercury is toxic even in very small doses and exposure to significant levels can result in mercury poisoning. The US Environmental Protection Agency standards for drinking water require that mercury concentrations are below 2 parts per billion (that’s 0.0000002%).

The primary health effects from mercury are on the development of the brain and nervous system. It is likely that subtle nervous system and developmental effects occur from chronic exposure to relatively low concentrations of mercury. Exposure to high concentrations of mercury over a long period of time can also result in brain damage.

Mercury is also dangerous to developing fetuses, children, and people that eat unusually large amounts of fish, such as subsistence fishermen. Because mercury can adversely affect brain and central nervous system development, pregnant women and women of child-bearing age are advised to be aware of how much mercury they consume.

Factors determining mercury exposure include the species of fish consumed, the concentration of methyl mercury in the fish, the quantity of fish consumed, and how frequently fish is eaten.

Professor Ho of the Hongkong Open University has stated that mercury is a neurotic poison, and that overdose of mercury would accumulate in human bodies, could cause cancer and affect development in embryos.

What is being done about this?

To date, 39 states in the US have issued at least one mercury advisory, and eleven states have issued statewide mercury advisories. There is also a mercury advisory in effect for the entire Gulf Coast from the Florida Keys to Corpus Christi.

In January 2002, the US Food & Drug Administration pointed out that the mercury content in sharks was excessive and warned pregnant women and children not to consume too much of it.

In early 2001, the governments of Australia and New Zealand issued a public warning to pregnant woman about eating shark and several other fish species because they may contain high levels of mercury.

Still, shark fin consumers in Asia are oblivious to the dangers. There is reason to believe that the lack of attention to this serious issue is due to the commercial pressures that the lucrative shark fin trade and its well-connected dealers bring to bear on the powers that be.

Sea Shepherd Conservation Society’s Bold Move

The Sea Shepherd Conservation Society, being a non-profit, non-governmental organisation known for its daring tactics and innovative, aggressive approach, is now leading the way in bringing this matter to public attention.

We want more objective studies on mercury levels in shark fin to be conducted by independent, non-government organisations in Asian countries. And we want the public to be aware of the risks.

The biggest risk of all is that if we continue to consume shark fins at the present rate, we could be eliminating not just sharks, but ourselves.

To raise awareness of the dangerous levels of toxic mercury in shark fins, the Sea Shepherd Conservation Society launched a new campaign consisting of press, poster and postcard advertisements (see above). The images show restaurant cooks and waiters wearing protective safety gear and gas masks while cooking, preparing and serving shark fin.