Methylmercury contaminating fish - pregnant women warned

According to an international team of scientists pregnant women should be wary of eating some types of fish because of mercury contamination.

The scientists say that greater controls are needed on power plants and the international trade in mercury to curb environmental damage, which they say is a global problem.

According to the "Madison Declaration on Mercury Pollution" published this week in a special issue of the international science journal Ambio, the health risks posed by mercury contaminated fish is sufficient to warrant issuing a worldwide general warning to the public.

The declaration is a synopsis of the latest scientific knowledge about the danger posed by mercury pollution and presents 33 principal findings from five synthesis papers prepared by the world's leading mercury scientists.

Methylmercury exposure now constitutes a public health problem in most regions of the world due to the use of fossil fuels, especially coal and the uncontrolled use of mercury in small-scale gold mining.

Methylmercury in the atmosphere is deposited in waterways and the sea where it is taken up by aquatic organisms.

On its way up the food chain it becomes concentrated and can reach high levels in large predatory fish, such as tuna, shark and swordfish.

Mercury is of particular danger to the developing foetus, and exposure can cause permanent damage when the nervous system is developing.

It is also thought to contribute to health problems in adults such as an increased risk of cardiovascular disease.

Apart from accumulating in predatory fish, the highly toxic form of methylmercury also builds up in fish-eating birds and mammals such as bald eagles, divers, otters, polar bears and seals and the scientists say tough international agreements on acceptable levels of mercury pollution are needed to address the problem.