Mercury

What is mercury?

Mercury is a silver-colored metal that is liquid at room temperature. Small amounts of mercury are naturally present in soil and water. Levels in soil average less than one part mercury for every million parts soil (ppm).

Approximately 43% of mercury releases can be attributed to natural sources such as volcanoes, the ocean, and soils. Human activities account for 57% of mercury releases on the earth. Most manmade mercury releases come from mining, coal and oil combustion, and burning of waste from cities and hospitals. Mercury releases from human activities peaked in the 1980s and are continuing to decline.

Where does mercury come from?

Mercury enters the environment through natural processes and as a result of human activity. Mercury is released through:

• weathering of rocks containing mercury;
• fossil fuel (coal and oil) combustion;
• mining of gold and ores that contain mercury;
• cement production;
• volcanic eruptions;
• manufacturing; and
• burning of municipal and medical waste;
• water treatment facilities.

Do electric utilities release mercury into the environment?

Yes. EPA estimates that electric utilities release roughly 1% of all mercury releases to the air, water, and soil in the U.S. Utilities release a total of 51 tons of mercury every year, compared to about 800 tons released through natural weathering processes. Utilities are one major source of airborne mercury releases.

How could I be exposed to mercury?

Since mercury occurs naturally in the environment, everyone is exposed to very low background levels that are not harmful to human health. The body naturally eliminates mercury, so background exposure is not considered harmful.

Main sources of mercury exposure are:

• food containing mercury (particularly fish and shellfish);
• mining production sites;
• recycling facilities, municipal or medical incinerators;
• coal-fired power plants;
• latex paint containing mercury;
• some dental and medical treatments (including tooth fillings);
• drinking water; and
• consumer products containing mercury (thermometers, batteries, etc.).

It is very rare for humans to inhale high concentrations of mercury vapor or to swallow large amounts of mercury, but such occurrences can be fatal. Breathing metallic mercury vapor can cause chest pains, cough, reduced lung capacity, or high blood pressure. Swallowing mercury can cause mercury-induced toxicity which has a detrimental effect on kidneys.

Mercury releases discussed in this paper are too low to cause poisoning.

What does EPA say?

EPA and other federal agencies are unclear about whether mercury emissions from power plants pose a significant risk to human health. Further research and evaluation of recent studies are on-going.

Mercury is considered a high priority for studies on human exposure through food and skin contact. Current information does not indicate a direct link between electric utility mercury emissions and public health concerns. However, experts agree that further research and monitoring should be conducted.

Questions remain, including the following.

• What exposure levels are likely to cause adverse health effects?
• How much mercury is emitted from natural sources?
• How much mercury is removed during coal cleaning and other ongoing pollution-control processes?
• How much would reductions in power plant mercury emissions decrease levels of mercury in the environment?

Because of these and other unanswered questions, EPA is unable to estimate the health risk posed by mercury emissions to the air.

Where can I get more information?

• Chemical Industry Institute of Toxicology
  6 Davis Drive, P.O. Box 12137
  Research Triangle Park
  North Carolina 27709-2137
  phone (919)558-1310
  
  
• Electric Power Research Institute
  3412 Hillview Ave.
  P.O. Box 10412
  Palo Alto, California 94303
  phone (650)855-2000
  
  
• Study of Hazardous Air Pollutant Emissions from Electric Utility Steam Generating Units' Final Report to Congress, Volume 1 and 2, U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, 1998.
  
  
• Toxicological Profile for Manganese, U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substance and Disease Registry, 1997.
  
  
• Toxics Release Inventory, Public Data Release, U.S. Environmental Protection Agency, Office of Pollution Prevention and Toxics, 1998.