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Sources of Mercury
Mercury is a naturally occurring element normally found in small amounts in rocks, soils and the oceans. Since mercury is an element, it never breaks down into a less dangerous form. Instead, it persists in the environment and can cycle for decades between land, air and water until eventually it is covered by sediments. Although there are some natural sources of mercury, humans are responsible for nearly two-thirds of the mercury currently circulating in our environment. (1)
According to the Minnesota Pollution Control Agency, most of Minnesota's mercury contamination is the result of smokestack emissions that fall into our lakes and rivers. The primary sources of mercury air emissions (see chart) are coal-burning power plants and taconite processing plants. Together, these sources account for nearly two-thirds of the mercury emitted in Minnesota.
Mercury occurs naturally in the coal we dig up and burn to generate 75% of our electricity in Minnesota and over half of our electricity in the U.S. There are many sources within the energy production sector (see chart), but coal-fired power plants alone produce just over 40 percent of the state’s total mercury air emissions. Coal-fired power plants are a growing part of the problem because our electricity demand continues to grow and because nearly every other sector that emits mercury has been required to reduce their emissions. For more detailed information on the problem of mercury air emissions in lakes and fish, see our Mercury in MN Water page.
Material processing is another major sources of mercury air emissions in Minnesota (nearly 21 percent). The Minnesota Pollution Control Agency lists only two sources within the material processing sector of their inventory: taconite processing and soil roasting. Within this sector, taconite processing is responsible for 98 percent of the mercury air emissions, making soil roasting a rather negligible source.
Finally, the Minnesota Pollution Control Agency estimates that 29 percent of the state’s air emissions of mercury come from intentional uses of mercury in a wide-variety of products and processes (see chart).
Mercury Emissions Trends
With regard to trends, there is some good news and some bad news. The Minnesota Pollution Control Agency uses a statewide mercury emissions inventory dating back to 1990. A trends chart shows that mercury emissions have been reduced dramatically from some industries and products, such as medical waste incineration, latex paints and golf course fungicides. Other sectors, such as electric utilities and taconite processors, have actually increased emissions in the same period. (2)
More Work to Do…
Clearly, there is much work to do to continue reducing mercury emissions from many Minnesota sources. This chart shows the largest source categories of mercury emissions in Minnesota according to the Minnesota Pollution Control Agency’s latest estimates.
Neither federal nor Minnesota law sets limits on the amount of mercury that these existing facilities can emit. Current air emissions permits for these facilities do not address mercury emissions at all. Minnesota has passed laws to address mercury in many products, which has resulted in a decline in mercury from such intentional uses. Unfortunately, many products that were sold before the laws were passed contain mercury and continue to be used. Eventually, these products find their way into the waste stream and can then release mercury during incineration, evaporation or directly into the water.
Mercury-Free Minnesota has a plan to reduce mercury emissions. Learn more at our Policy Agenda page. And visit our Act Now page to find out how you can help reduce mercury emissions in Minnesota.
Notes:
(1) U.S. EPA, 1997a. Mercury Study Report to Congress, Volume II: An Inventory of Anthropogenic Mercury Emissions in the United States. EPA-452/R-97-004.
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