Photograph by Steven Higgs
The Rockport Power Plant in Spencer County released 932 pounds of the neurotoxin mercury into the environment in 2010. A new study from the University of Washington says much of that will remain in the upper reaches of the atmosphere, where it will be transformed into a more potent form and redeposited around the globe.
Mercury released from Ohio River Valley industries is damaging the brains of children around the world.
That's a conclusion that can be drawn from a University of Washington (UW) study published online Dec. 19 in the journal Nature Geoscience, which concludes mercury in the upper atmosphere can circulate for "long periods of time" before falling back to the Earth's surface.
“Much of emitted mercury is deposited far from its original sources,” the paper's lead author Seth Lyman said in a UW news release. “Mercury emitted on the other side of the globe could be deposited right at our back door, depending on where and how it is transported, chemically transformed and deposited.”
And by the time that mercury, like the 7,000-plus pounds released into the atmosphere by Indiana industries in 2010, is deposited in, say, Africa or Asia, the potent neurotoxin has been transformed into a more dangerous form.
Elemental mercury reaching the upper troposphere and lower stratosphere is transformed into oxidized mercury, which can be deposited into aquatic ecosystems and enter the food chain, said Lyman, a former UW science and technology professor who is now with the Utah State University’s Energy Dynamics Laboratory.
“The upper atmosphere is acting as a chemical reactor to make the mercury more able to be deposited to ecosystems,” he said.
The troposphere extends from between four and 12 miles from the earth's surface to the stratosphere.
In 1997, the U.S. Environmental Protection Agency (EPA) issued the eight-volume "Mercury Study Report to Congress." Its 376-page third volume, "Fate and Transport of Mercury in the Environment," detailed mercury's properties and pathways from industrial smokestacks to human bodies.
"Elemental mercury that is not oxidized will undergo long-range transport, remaining in the atmosphere from one-half to two years."
A naturally occurring element, mercury is a liquid heavy metal that readily vaporizes at ambient temperatures. It is emitted into the environment naturally and through man-made processes, which are "dominated by industrial processes and combustion sources," the EPA report said.
How far mercury travels from a smokestack depends on its form – especially its oxidation state – and atmospheric conditions, the EPA report said. About half enters the "global atmospheric cycle," with the rest falling to the ground through "local or regional cycles," either in precipitation or in particle form.
Mercury exists in three oxidation states: elemental, mercurous and mercuric, EPA said. The latter two can form other chemical compounds, including methylmercury, an organic compound that easily moves up the food chain.
Elemental mercury that is not oxidized "will undergo long-range transport," the report said, remaining in the atmosphere from one-half to two years. These emissions can be carried "anywhere on the globe before transformation and deposition occur."
Oxidized mercury remains anywhere from "hours to months" before falling to the ground, the EPA report continued. Roughly 5 to 10 percent of mercury emissions fall within 60 miles of the original source.
Once oxidized mercury reaches the surface, it is transformed by bacteria into methylmercury. The authors say the EPA report, in conjunction with existing scientific knowledge, supported a "plausible link" between mercury emissions from industrial sources and "methylmercury concentrations in freshwater fish."
Mercury is also a potent neurotoxin linked to a wide range of developmental disabilities in children, including autism, attention-deficit hyperactivity disorder, intellectual impairments and behavioral problems. Exposure can begin in the womb.
"Elemental mercury reaching the upper troposphere and lower stratosphere is transformed into oxidized mercury, which can be deposited into aquatic ecosystems and enter the food chain."
A 2005 report from the Environmental Working Group called "Body Burden – the Pollution in Newborns" found mercury and 286 other industrial chemicals in randomly selected placentas collected from hospitals nationwide and tested for the presence of toxic chemicals.
"Chemical exposures in the womb or during infancy can be dramatically more harmful than exposures later in life," the report said. "Substantial scientific evidence demonstrates that children face amplified risks from their body burden of pollution; the findings are particularly strong for many of the chemicals found in this study, including mercury, PCBs and dioxins."
After birth, developing children are exposed to mercury and other toxins in childhood vaccinations and in the food they eat.
A paper published in the November 2007 issue of the British medical journal The Lancet titled "Developmental neurotoxicity of industrial chemicals" placed the same chemical suspects at the top of the list that the Environmental Working Group did. Its lead author was Philippe Grandjean from the Harvard School of Public Health.
"Neurodevelopmental disorders such as autism, attention deficit disorder, mental retardation, and cerebral palsy are common, costly, and can cause lifelong disability," the study said. "Their causes are mostly unknown. A few industrial chemicals (eg, lead, methylmercury, polychlorinated biphenyls [PCBs], arsenic, and toluene) are recognised causes of neuro-developmental disorders and subclinical brain dysfunction."
A Harvard news release said the researchers found 202 industrial chemicals with the capacity to damage the human brain. "They conclude that chemical pollution may have harmed the brains of millions of children worldwide."
A January 2011 report from the nonprofit group Environment America found nine coal-fired power plants on the Indiana side of the Ohio released almost 11,000 pounds of mercury into the environment the year before.
"A 2005 report from the Environmental Working Group called 'Body Burden – the Pollution in Newborns' found mercury and 286 other industrial chemicals in randomly selected placentas collected from hospitals nationwide."
The Indiana Fish Consumption Advisory, compiled annually by state health, environment and natural resources agencies, advises citizens on PCB and mercury levels in fish on every lake, river and stream in the state. "Women who are pregnant or breast-feeding, women who plan to have children, and children under the age of 15," it says, should not eat any of eight common fish species caught in the Ohio, including channel catfish, flathead catfish, and three species of bass.
The UW study based its conclusions about mercury transport and transformation on air samples collected during research flights in October and November 2010 over North America and Europe by a National Center for Atmospheric Research aircraft.
Lyman built a device that can detect both elemental and oxidized mercury in the same air samples. While the flights routinely fly at altitudes well below the confluence of the troposphere and the stratosphere, several times the aircraft encountered streams of air that had descended from the stratosphere or from near it, the UW release said.
The result, Lyman said, was the first evidence that elemental mercury is transformed into oxidized mercury, and it indicated the process occurs in the upper atmosphere.
It is not known with certainty how the transformation takes place, the UW release said, but once it does, oxidized mercury "is quickly removed from the atmosphere, mostly through precipitation or air moving to the surface."
Steven Higgs can be reached at .
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