City lakes attract more airborne mercury than those further away
We know mercury is harmful and that power plants, chemical makers and cement plants put it into our environment. But little is known about where it ends up.
Chances are it’s near where lots of people live.
A new study proves that if you’re an urban dweller, air and rain are far more likely to dump mercury into lake near you.
Researchers at the U.S Geological Survey found that mercury deposits at about four times the rate in city lakes as those further away. They sampled soil at lakes from within 30 miles and more than 100 miles of 12 cities, including two from the Great Lakes region – Chicago and Minneapolis.
Researchers tested lakes isolated from runoff because they were interested in atmospheric deposition, which is mercury that came from the air or rain. The study will be published in the March 2012 edition of Environmental Pollution.
About 80 percent of Americans live in urban areas, according to the U.S. Census.
Mercury can attack the brain, kidneys, heart and the unborn, according to the Center for Disease Control. Pregnant women and children are at higher risk.
When emitted, mercury can travel far and doesn’t always settle nearby.
“Mercury is a global pollutant and we wanted to look at how much emissions are spread globally versus how much they stay nearby,” said Peter Van Metre, research hydrologist and study author.
And city lakes had far more deposition. For example, mercury deposited in a lake six miles north of Boston was five times greater than a lake 139 miles north.
Most U.S. coal-fired plants, which are responsible for roughly half of U.S. mercury emissions, aren’t in cities, Van Metre said. But cities do have other industrial emitters, more cars and more legacy pollution.
There are a couple of reasons that cities may have more mercury deposition.
“It could just be that local emissions are more likely to deposit locally,” Van Metre said. “Vehicles and pollution that’s been in cities for years could just deposit close to where it’s from.”
Another reason could be the nature of city air.
“When mercury is a gas, it’s pretty stable in the air, but when it’s oxidized, it will fall out,” Van Metre said. “There are things in urban air, like ozone, that will oxidize it.”
But more mercury doesn’t always mean more health concerns. Methylmercury is what accumulates in fish and people and is the form most likely to hurt us. Most mercury in urban lakes doesn’t turn into methylmercury.
“Methylmerury is associated with organic material and wetlands; a lot of urban lakes have dredged shorelines,” Van Metre said. “Where there may be less mercury loading in lakes away from cities, there’s more methylization, and more of a problem with fish.”
Van Metre said the most at risk lakes are those near cities that still have ample natural surroundings to turn mercury into a more harmful compound.
As Echo reported in October, despite years of decline, methylmercury levels are on the rise in some Great Lakes wildlife.
And officials are paying attention. Van Metre’s study was released almost simultaneously as President Barack Obama passed the nation’s first national standards for coal-fired plants’ mercury emissions last month. On Dec. 21, 2011, the Environmental Protection Agency (EPA) mandated that the plants use available technology to reduce emissions by 90 percent, as mandated by the 1990 Clean Air Act.
Regional environmental groups applauded the new rules.
“These standards mean power plants will invest in modern pollution controls, and that investment will create jobs, cleaner air and better public health,” Howard Learner, executive director of the Environmental Law and Policy Center in Chicago, said in a prepared statement.
“The technology works, the lights have stayed on, mercury pollution has been reduced and children’s health is better protected,” Learner said, referring to the plants in Illinois that have already made changes.
According to the EPA, around 800 of the approximately 1,400 coal and oil fired plants have already taken action.The regulations were anticipated by the plants after a March 2011 Court of Appeals ruling pushed the EPA to create stricter air standards. The agency predicts the standards will create 46,000 short-term construction jobs and 8,000 long-term utility jobs because of manufacturing and engineering needs, and long-term pollution control, a claim disputed by some industry groups.
While his study has nothing to do with the new standards, Van Metre hopes it will keep it on people’s minds.
“They (the EPA) took a big step, but mercury isn’t going away,” he said. “We will continue monitoring efforts and figure out where it’s going.”