Much More Toxic Mercury Is Blowing In From Asia Than Thought
Forget fish for a moment, and start worrying about the toxic mercury in the air around you.
Researchers have found that Asia is producing more than double the amount of the toxic metal—mainly from the burning of coal that also is a prime culprit in global warming—than previously thought.
After mercury is released it can remain in the atmosphere for a year as winds blow it around the world. Some of the mercury ends up deposited on land and in the ocean.
“This underestimate of emissions is important as it suggests we have a lot more work to do in terms of reducing emissions and benefiting human health,” said Noelle Selin, an MIT professor of atmospheric chemistry who collaborated with a team of researchers from around the world on the study, which was published this week in the journal Atmospheric Chemistry and Physics. “There’s been a recent growth in industrial activities and power production in Asia, and policy has a long way to go to clean that up.”
The scientists also found that mercury emitted more than a year ago is more likely to be found on land than in the ocean, information that should help policy makers better manage exposure to the toxic substance.
Mercury has been shown to cause brain damage in fetuses, infants, and young children who are exposed to it in higher amounts—usually when they or their pregnant mothers eat contaminated fish. Mercury also has been shown to affect wildlife such as ducks, herons, and egrets.
The researchers plugged data from 27 stations around the world that monitor atmospheric mercury levels in the atmosphere into a computer model. In the past, scientists relied on reports from coal-fired power plants to measure global mercury emissions, which Selin said were of limited use.
The study found that between 5,000 and 6,000 metric tons of mercury emissions are cycling through the atmosphere at any given time.
“But you have to remember that since mercury is a very toxic substance, it’s not the total amount that matters," Selin said. “What matters is that it’s toxic when it becomes methylmercury—and that we’ve increased the amount of mercury by a factor of three to five times more, thanks to human activities.”
Mercury is transformed into more toxic methylmercury in the ocean, though scientists have yet to discover how that happens.
The MIT study didn’t measure where in the atmosphere the mercury was moving or how much mercury was in the environment for any given particular location.
Still, Selin believes that her findings showing that land is a larger sink of mercury than previously thought point to possible areas of future research, such as how land-use change could affect how much mercury is being rereleased into the environment.
“We’re getting better at tracking where mercury is going,” Selin said. “From an environmental and public health perspective, we want levels to go down. So the better we get at tracing it, the more effective we can be in targeting policy interventions.”