A recent study by the US Geological Survey has pointed the finger at Asia’s coal fired power stations. Original theories believed that mercury levels in the ocean were caused by pollution from US and Canadian coal plants being passed into clouds from the atmosphere, where the mercury would then return to earth in rain and other precipitation. The findings of the study no longer think this is the main cause.
Although the authors of the study do not target Asia as the only party responsible for increased levels of mercury in the world’s oceans, they believe that the continent is responsible for a particularly significant contribution to the problem. William Landing, a lead scientist on the study, commented,
“We believe the majority of Asian mercury emission comes from coal burning.”
Increased mercury levels in the sea can have a devastating effect for many populations across the globe, not just humans, but many creatures rely on fish for their diet. Although the mercury itself is bad news, and is a poisonous chemical in itself, it is not the most worrying factor about the increasing levels. Algae in the oceans absorb the mercury from the surrounding waters, which then becomes chemically bonded with methyl molecules when bacteria further down in the ocean break the dead algae down when their bodies sink. This creates MethylMercury, a substance which is even more lethal than mercury alone.
A considerable problem is bioaccumulation. The dead algae which contain the MethylMercury are eaten by small organisms, which in turn are eaten by creatures higher up the food chain. As each creature higher up the food chain requires more of the smaller creatures to sustain them, they are getting a higher dose of harmful MethylMercury, and so on, in much the same way as problems with pesticides such as DDT occurred, eventually killing those at the top of the food chain because levels of the poisons become so much more concentrated.
There is also a risk to humans. Many people are aware of the danger of mercury and as a result, pregnant women are advised to avoid fish that is commonly known to be at risk of containing the chemical. This is due to foetal damage that can occur as a result. But not everybody has the luxury of choosing what makes up their diet; not everybody has the benefit of living in western society where alternatives are available.