The toxicity and use of the naturally occurring element mercury has been recognized for thousands of years. The state of Michigan has identified mercury as one of the primary pollutants of concern for decades. Mercury contaminated fish have resulted in the Michigan Department of Public Health issuing a state-wide fish advisory in 1988, for all of Michigan’s 11,000 inland lakes. Several accidental poisonings of mercury have also occurred in the state because of the various uses and lack of understanding of mercury hazards. Because mercury is toxic, the uses continue to decline. From 1983 to 1994, the United States use of mercury decreased by approximately 72%. However, the unique chemical and physical properties of mercury promote its continued use in certain applications.
In Michigan it is estimated that between approximately 8,400 to 10,400 pounds of mercury are released to the atmosphere annually. Mercury emissions have decreased in recent years and are expected to continue to decline. This decrease is primarily a result of facilities adding mercury controls or closing down their operations known to emit mercury. Between 200 to 1,800 pounds of mercury are discharged to Michigan waters, and approximately 3,800 pounds of mercury are discarded in the municipal and commercial waste stream. Mercury can enter water bodies through direct discharge, nonpoint runoff or from atmospheric deposition which is the most significant source. Mercury in aquatic systems can be converted by microorganisms into methylmercury, a bioaccumlative form that can build up in fish tissue causing a potential risk to humans and animal species that consume the fish. Methylmercury is a neurotoxin, and the developing fetus is most at risk from methylmercury poisoning. At this time the direct contribution from various mercury sources to mercury levels in fish are not known. The mercury that is deposited into lakes can originate from local sources or other states or other countries because mercury is volatile and can be transported by winds thousands of miles before being deposited. The issue is, therefore, a regional concern and even a national and international one.