Mercury is a neurotoxin which affects the brain and nervous system; developing fetuses and young children are the most susceptible to its debilitating affects. A loss of physical coordination and mental retardation are among the impacts from chronic exposure to mercury. The term "mad hatter," of course, comes from the common occurrence of dementia experienced by nineteenth century England hatters who used mercury to make hats.
While no one has yet documented a "mad angler" syndrome, there is growing concern about the ever increasing number of lakes with mercury contaminated fish. Wisconsin is not alone in this regard. Although Wisconsin and Minnesota have the longest lists of mercury contaminated lakes, at least 24 other states have such lists as well.
Mercury exists throughout the natural environment in trace amounts often called background levels. However, human sources of mercury emissions contribute to higher concentrations. Mercury is released from the burning of fossil fuels, public waste water treatment facilities, wastewater discharge pipes, smoke stacks of many factories that use mercury in industrial processes, and from disposal of products with mercury (such as thermometers).
Just 10 to 15 years ago, paints and batteries were among the largest sources of mercury entering the environment. Mercury in paint (added as a fungicide) was banned several years ago and the battery industry has voluntarily replaced mercury as an additive.
Mercury tainted lakes are found across Wisconsin. Some are found near industrial facilities, like Lake Monona surrounded by the city of Madison; but the highest concentrations are nestled in the relatively secluded forests of our northern most counties such as Vilas and Oneida counties. The discovery of mercury contaminated fish in lakes of the relatively pristine northern-most reaches of Canadian provinces was one of the first clues that the most important source of mercury entering these lakes was the atmosphere - and mercury rain.
Nationwide, waste incinerators and coal-fired power powerplants are the largest sources of mercury and together may account for nearly half of all human sources of mercury emissions. An EPA report on mercury emissions required by the last Clean Air Act amendments is more than two years overdue and is expected in January.
In Wisconsin coal-fired power plants are by far the largest source of mercury emissions. Although direct monitoring of emissions is not required, DNR estimates indicate that power plants account for as much as 60 percent of all mercury emissions in the state.
Wisconsin's Environmental Decade has discussed with legislators plans for introducing a mercury cap bill in the state legislature. The bill would cap mercury emissions statewide at current levels immediately and create a modest schedule for reducing future emissions. This approach is very similar to that used to address acid rain in Wisconsin in the mid-80s. As with acid rain, some researchers believe that approximately half of the mercury rain falling in Wisconsin originate from "local" sources and half from distant sources, so reducing our own emissions is an important step to reducing mercury rain.
Minnesota and Michigan also have extensive fish consumption advisories for mercury and Wisconsin's Environmental Decade is actively working with advocates in those states on a regional mercury reduction campaign. Stay tuned for ways that you can get involved in the campaign to stop the mercury rain.
In mid-February, Wisconsin's Environmental Decade will release a major report on mercury contamination of Wisconsin's waters. More information on this problem will be posted following the release of this report. For now, if you have a question or want more information, please contact Keith Reopelle of Wisconsin's Environmental Decade.