Pollution triples mercury levels in ocean surface waters, study finds

Toxic metal threatens marine life as it accumulates faster in shallow layers than in deep sea due to human activity

By Fiona Harvey for The Guardian
Published August 6, 2014

The amount of mercury near the surface of many of the world’s oceanshas tripled as the result of our polluting activities, a new study has found, with potentially damaging implications for marine life as the result of the accumulation of the toxic metal.

A sewage drain floods into the Mediterranean Sea off the coast of Gaza, in Nuseirat. Photograph: Warrick Page/Getty Images

A sewage drain floods into the Mediterranean Sea off the coast of Gaza, in Nuseirat. Photograph: Warrick Page/Getty Images

Mercury is accumulating in the surface layers of the seas faster than in the deep ocean, as we pour the element into the atmosphere and seas from a variety of sources, including mines, coal-fired power plants and sewage. Mercury is toxic to humans and marine life, and accumulates in our bodies over time as we are exposed to sources of it.

Since the industrial revolution, we have tripled the mercury content of shallow ocean layers, according to the letter published in the peer-review journal Nature on Thursday. Mercury can be widely dispersed across the globe when it is deposited in water and the air, the authors said, so even parts of the globe remote from industrial sources can quickly suffer elevated levels of the toxic material.

For several years, scientists have warned that pregnant women and small children should limit their consumption of certain fish, including swordfish and king mackerel, because toxic metals including mercury and lead have been accumulating in these species to a degree that made their over-consumption dangerous to human health. Pregnant women are particularly at risk because the metals can accumulate in the growing foetus, and in sufficient quantities can cause serious developmental disorders.

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