Coal-fired power stations 'poison fish with mercury'

They say it takes only three years for particles of the toxic metal to float through the atmosphere after being expelled as a by-product of burning coal, fall into the oceans and contaminate marine life.

The speed of contamination has shocked scientists.

There are also concerns that the increasing number of coal power stations in countries such as China could put the world's health at risk.

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Mercury emissions in the atmosphere break down into more toxic methyl mercury. Until now, there has been controversy over how it gets into the food chain.

Scientists from the University of Alberta in Canada proved a direct link with emissions by releasing mercury into a lake in Ontario and measuring the effects over several years.

Researcher Vincent St. Louis said: "We can say conclusively that if you reduce mercury emissions it will result in less mercury in fish."

Some fish have worrying levels of mercury, which can damage the nervous system of unborn children and have been linked to heart disease and strokes.

Children, pregnant women and those trying for a baby are advised to limit their intake of tuna, marlin, shark and swordfish.