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Mercury-free Colorado
Campaign
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| Mercury Toxicity | Human Exposure to Mercury |
| Mercury in the Environment | "Water Quality Limited" Waters |
| Mercury-free Colorado Home |
Mercury (Hg) is a naturally occurring metal found throughout the environment. It is a liquid at room temperature, combines easily with other metals and expands and contracts evenly with temperature changes. Because of these properties, mercury has been used in many household, medial and industrial products. Although mercury performs many useful functions in our workplaces and homes, it is toxic and can impair our health. Mercury is a potent neurotoxin, meaning that it interferes with the way nerve cells function. Mercury poisoning causes a decreased ability to see, hear, talk and walk. It can cause personality changes, depression, irritability, nervousness, and the inability to concentrate. It can also cause damage to the brain, kidneys and lungs. Mercury is a particularly serious problem for pregnant women and children. Fetuses and young children suffer the greatest risk because their nervous systems are still developing. They are four to five times more sensitive to mercury than adults.
Mercury can be released in the environment from natural sources, such as volcanic and geothermal activity, marine environments or forest fires, or it can be released from anthropogenic (man-made) sources like coal-fired power plants and other industrial activities. Recent studies suggest that human activity contributes 50-70% of the mercury in the environment globally (Office of Air Quality and Standards Report to Congress, 1997). Once mercury enters the environment, it circulates in and out of the atmosphere until it ends up in the bottoms of lakes and oceans. Mercury is among a group of pollutants called persistent bio-accumulative toxins or PBTs. These pollutants "persist" in the environment, meaning that they do not break down or go away. Mercury cannot be destroyed, it cannot be combusted and it does not degrade.
When mercury is deposited in waterways, bacteria convert it to methylmercury. Methylmercury builds up in the tissue of fish, which may then be eaten by wildlife (e.g., eagles, osprey, common loons, river otters, minks) and by people. Because mercury is tightly bound to the fish muscle tissue, there is no method of cooking or preparation that will remove or reduce mercury once it is in fish. This doesn't mean that you should stop eating fish. It is a good source of protein and is low in saturated fat. You can still get the benefits of eating fish by using moderation in how much you eat. The two organ systems most likely affected by methylmercury are the central nervous system and the kidneys. The groups most vulnerable to the effects of mercury toxicity include women who are pregnant or may become pregnant, nursing mothers, and young children. The most significant concerns regarding chronic exposure to low concentrations of methylmercury in fish are for neurological effects in the developing fetus and children.
Although human exposure to mercury occurs most frequently through eating contaminated fish, other human exposures to mercury can occur. People have been exposed to mercury from inhaling mercury vapors from broken fluorescent lamps, gas regulators or even home fever thermometers. There have been cases of mercury exposures from accidental swallowing, but these cases are rare.
Water Quality programs across the country, including Colorado, often address unacceptable mercury levels in local water bodies through the Total Maximum Daily Load (TMDL) process. The TMDL process was designed by the Clean Water Act to insure that all sources of pollutant loading are accounted for when devising strategies to meet Water Quality Standards. The TMDL is an estimate of the greatest amount of a specific pollutant that a water body or stream segment can receive without violating water quality standards. The State compares recent information regarding the physical, chemical and biological condition of a stream segment with the associated water quality standards for that stream segment. Where Technology-based effluent limits in discharge permits alone are not stringent enough to assure that water quality standards are met, these stream segments are designated "Water Quality Limited" and added to a list. This list, called the 303(d) List, identifies the specific component (such as mercury (Hg), nitrate, or copper) that is the basis for the water quality problem in that segment of the water body. TMDLs are required for all components listed for each stream segment on the 303(d) List. This list is updated every two years.
The Colorado Department of Public Health and Environment has issued fish advisories that place limits on safe quantities for consumption of fish from McPhee and Narraguinnep reservoirs as well as other lakes in the state. Pregnant women, women planning to become pregnant, nursing mothers and children less than 9 years old must be especially careful. The recommended safe consumption level is four meals of fish per month for non-pregnant adults and one meal per month for women who are pregnant, nursing or planning to become pregnant and children 9 years of age or younger. This level is consistent with fish advisories issued by other states in the 1990s. The US EPA considers one meal for an adult to be 6 ounces of cooked fish (8 ounces of uncooked fish) and for a child to be 2 ounces of cooked fish (3 ounces of uncooked fish).
If you have any questions or comments on alternatives to mercury or would like more information on the mercury campaign, please contact us at cdphe.hmmercury@state.co.us.
