Mercury: Polluting the World's Oceans

Mercury, a naturally occurring but poisonous element if ingested in large amounts, is polluting the world's oceans. Levels are three times higher in the upper ocean than what they were during the Industrial Revolution, according to a recent study.

Scientists from the Woods Hole Oceanographic Institution (WHOI) worry that mercury is increasingly posing a danger to humans as well as the environment given its abundance.

Mercury is not only found naturally on Earth, but is also a by-product of human activities such as burning coal and making cement. However, until now, little was known about how much mercury in the environment is the result of human activity, or even how much bioavailable mercury exists in the global ocean - that is, forms of the element that can be taken up by animals and humans.

In this study, published in the journal Nature, researchers provide the first direct calculation of mercury in the global ocean from pollution based on data obtained from 12 sampling cruises over the past eight years.

"It would seem that, if we want to regulate the mercury emissions into the environment and in the food we eat, then we should first know how much is there and how much human activity is adding every year," WHOI marine chemist Carl Lamborg said in a news release.

So they started by looking at oceanic levels of phosphate, a substance that is both better studied than mercury and behaves in much the same way. Like mercury, phosphate is taken up into the marine food web by binding with organic material. By determining the ratio of phosphate to mercury in water deeper than 1,000 meters (3,300 feet) that has not been in contact with Earth's atmosphere since the Industrial Revolution, the group was able to estimate mercury in the ocean that came from natural sources, like the weathering of rocks.

The researchers found that about 60,000 to 80,000 tons of mercury pollution is in the global ocean. Also, the ocean as a whole has shown an increase of roughly 10 percent over pre-industrial mercury levels.

While these findings are informative, scientists are really concerned with what this means for environmental, as well as human health.

"The trouble is, we don't know what it all means for fish and marine mammals," Lamborg added.

According to the Agency for Toxic Substances and Disease Registry, humans exposed to high levels of metallic, inorganic, or organic mercury can permanently damage the brain, kidneys and developing fetus. Short-term exposure may result in lung damage, nausea, vomiting, diarrhea, increases in blood pressure or heart rate, skin rashes, and eye irritation.