Mercury is a naturally occurring metallic element that is found in trace amounts in air, water, and soil. It comes in three forms—elemental, inorganic, and organic. Mercury is familiar to most of us in its elemental form as the heavy, silvery liquid metal used in thermometers, fluorescent light bulbs, and some switches. Inorganic mercury compounds are created when mercury is combined with other elements, such as chlorine, sulfur, or oxygen. It is used in some medications and industrial compounds. Organic mercury compounds are formed when mercury combines with carbon. The most common organic mercury compound, methylmercury, is produced mainly by bacteria in water and soil.

> Link to more information about forms of mercury on the U.S. Environmental Protection Agency Web site.

In nature, mercury tends to be bound up in rocks and soil and is widely dispersed. Much of it is locked away in coal and other geological deposits, where it does not pose a danger to living organisms. However, human activities can release mercury from these natural sources. When humans extract mercury from rocks or burn fossil fuels, it is released into the atmosphere. Airborne mercury can eventually settle into soil and rivers, lakes, and oceans, where aquatic microbes convert it to methylmercury through a biochemical reaction. Fish then absorb methylmercury from the water as it passes over their gills and as they feed on other aquatic organisms. As larger fish eat smaller ones, concentrations of the pollutant increase in the bigger fish, a process known as bioaccumulation. Thus, mercury enters the food chain and becomes concentrated.

People can be exposed to mercury in a number of ways. They may come in contact with mercury from broken thermometers or other spills in the home or workplace. They may breathe in airborne mercury produced by coal-fired power plants, mining operations, or other industrial sources. But by far the most common route of mercury exposure in humans is eating fish contaminated by methylmercury, according to the federal Centers for Disease Control.

> Link to more information about sources of mercury on the U.S. Environmental Protection Agency Web site.

All forms of mercury are poisonous to humans. The severity of effects depends largely on the amount and timing of exposure. Short-term exposure to high concentrations of mercury vapor can cause harmful effects on the nervous, digestive, and respiratory systems, and the kidneys. Chronic exposure can permanently damage the brain and kidneys. Because fetuses, infants, and children are still developing, they are particularly sensitive to the effects of methylmercury on the nervous system, even at low levels of exposure, and data are evolving in support of a link between methylmercury exposure and increased risk of high blood pressure and heart disease at any age.

> Link to more information about health effects of mercury on the U.S. Environmental Protection Agency Web site.

To help protect public health, the Idaho Division of Health issues fish consumption advisories when fish in water bodies in Idaho are found to have methylmercury levels above what is considered safe. Fish consumption advisories don't mean you should stop eating fish from affected water bodies, however. Fish is a good source of protein and low in saturated fat. Simply limit fish consumption to amounts specified in the advisory.

> Link to fish advisories currently impacting water bodies in Idaho on the Idaho Department of Health and Welfare Web site.

The need for fish consumption advisories for some Idaho water bodies indicates that mercury pollution is a factor in Idaho , as do the results of water quality studies that show some water bodies in Idaho are impaired and fail to meet water quality standards for mercury. It is felt, however, that mercury pollution is less a problem here than in more highly industrialized states, particularly in the East and Midwest , where many coal-fired power plants operate. Additional studies are underway to verify mercury estimates.

Sources of mercury pollution in Idaho include a mixture of in-state and out-of-state human-caused and natural processes such as mining operations, petroleum combustion, coal-powered plants, various manufacturing sources, sewage treatment plants, landfills, and other sources.

DEQ is working collaboratively with the U.S. Environmental Protection Agency, surrounding state environmental protection agencies, public drinking water systems, the medical community, schools, and others to reduce mercury sources in Idaho . Specific activities include:

• Mercury Contamination Pilot Study: It is important that we have accurate data upon which to base future efforts to reduce mercury contamination in Idaho 's water bodies. DEQ is conducting a pilot study of mercury contamination in the Salmon Falls Reservoir and Jordan Creek in southern Idaho. Fish in both of these systems exhibit elevated levels of mercury in their tissues. The purpose of the study is to identify the sources of mercury contamination in these areas. To this end, DEQ is collecting and analyzing information from both air and water monitoring projects focused on the study area. A broad-based, statewide study of all mercury sources may ultimately be required.

• Mercury Deposition Network Site Acquisition: DEQ is working to obtain a Mercury Deposition Network (MDN) site in southeastern Idaho . The MDN is a monitoring network currently comprised of more than 85 sites in North America . Its purpose is to develop information on spatial and seasonal trends in mercury deposited to surface waters, forested watersheds, and other sensitive areas. The information will be used to help determine how mercury emissions impact human health. Link to more information on the Mercury Deposition Network.

• New Mercury Rule and Total Maximum Daily Load Development: Under a proposed rule initiated by DEQ and codified into DEQ's Water Quality Standards in April 2005, a new fish tissue criterion for methylmercury will help us evaluate whether water quality is impaired by mercury. This, in turn, will enable DEQ to develop and implement water quality improvement plans known as total maximum daily loads (TMDLs) for mercury in water bodies with fish tissue that tests above levels established in the rule.

In 2004, DEQ completed an assessment of water quality in the Snake River-Hells Canyon Subbasin (Brownlee Reservoir) along the Idaho-Oregon border where a mercury fish consumption advisory has been in effect since 1994. Development of a mercury TMDL was delayed, however, pending acquisition of additional data on methylmercury in fish tissue. A mercury TMDL for Brownlee Reservoir is scheduled to be developed in 2006. Link to Snake River-Hells Canyon (Brownlee Reservoir) Subbasin Assessment.

• Air Quality Permitting: DEQ is the state agency delegated responsibility for administering the federal Clean Air Act in Idaho . This responsibility includes issuing permits that limit the volume of hazardous air pollutants, including mercury, that facilities may emit and conducting inspections of these facilities to assure compliance with federal and state air quality standards. DEQ also tracks and maintains a database of volumes of hazardous air pollutants emitted. Link to more information on hazardous air pollutants and air quality permitting.

• Voluntary Partnership with Hospitals for a Healthy Environment (H2E): Mercury can be found in many commonly used hospital devices and materials, including thermometers, blood pressure monitors, esophageal tubes, and others. Most mercury-containing equipment has a mercury-free alternative. H2E is a voluntary program to help health care facilities reduce the amount and toxicity of wastes they generate. In 2003, DEQ joined H2E and is working with Idaho hospitals to facilitate elimination of mercury at these facilities. Link to DEQ's H2E Web page. DEQ has also worked with the Idaho Dental Association to provide information to dentists on safe disposal of mercury used in dental amalgam.

• BMPs for Mercury-Containing Equipment at Public Drinking Water Systems: As the state agency delegated responsibility for administering the federal Safe Drinking Water Act in Idaho, DEQ works closely with local public health districts and public drinking water systems to assure that the water we drink is free of contaminants including mercury. In 2003-04, DEQ conducted an evaluation of equipment used by public drinking water systems in Idaho to identify mercury-containing equipment, including electric switches, sensors, gauges, and meters, with a potential to contaminate drinking water. A technical guide was completed and is available to provide system operators with best management practices to prevent mercury-containing equipment from contaminating drinking water.

• Hazardous Waste Regulation: Every business in Idaho is required to track the volume of wastes generated, determine whether or not each is hazardous, and ensure that all wastes are properly disposed of according to federal, state and local requirements. As the state agency delegated responsibility for administering the federal Resource Conservation and Recovery Act in Idaho, DEQ maintains an inventory of hazardous wastes generated in Idaho and works closely with businesses to assure that hazardous wastes, including mercury, are transported, stored, and disposed of safely.

• Automotive Mercury Switch-Out Program: DEQ is providing guidance to auto repair shops in Idaho to facilitate switching out vehicle mercury switches for non-mercury replacement switches and to assure safe disposal of mercury-containing switches. Link to more information on Mercury Switches in Automobiles: Information for the Auto Services Sector.

• School Labs Chemical Management and Cleanup Project: In a study conducted by DEQ in 2003-04, it was revealed that a number of schools in Idaho have amassed large stockpiles of hazardous products on school grounds and lack knowledge of secure management and safe disposal procedures for hazardous chemicals and waste. Mercury was among the hazardous materials discovered at some school labs. DEQ has initiated a pilot project in eastern Idaho to assist schools in removing mercury and other hazardous products from school labs and to instruct science teachers in safe chemical management and disposal.

• Public Education and Outreach: DEQ is working to increase public awareness of risks associated with mercury exposure and ways to reduce releases of mercury into the environment. Among the projects under development are guidelines for communities to host events at which mercury-containing thermometers can be exchanged for digital models.

Mercury pollution cannot be prevented by government action alone. Individual consumers and businesses play an equally vital role. Here are some things you can do to help reduce the threat mercury poses to our environment and health: