Mercury and Ambient Air
Mercury is a naturally occurring element in the environment, but it is also an important environmental contaminant due to atmospheric deposition from man-made sources. This means that mercury enters the atmosphere through a variety of natural releases such as volcanos, forest fires, and evaporation from water and land, as well as through numerous man-made emissions to the atmosphere. In the United States, coal-fired electrical power plant emissions are currently thought to be the largest man-made source of air emissions of mercury, but there are also other man-made sources sucha s waste incineration that are being significantly reduced or eliminated. After mercury is emitted to air, it is deposited to soils and waters, where it can undergo other processes that may change it into an even more toxic form of mercury (methyl mercury).
Mercury and Seafood
Mercury (especially methyl mercury) is an important fish tissue contaminant because of its potential ability to cause permanent harmful effects on the nervous system development in the fetus, as well as the learning capacity, and behaviors of the very young. Most health advice to avoid mercury exposures is therefore directed to mothers of young children, women who are nursing, women who are pregnant or may become pregnant, and older female children or teenagers. These are examples of “sensitive sub-populations” of people that environmental regulators attempt to protect from health problems due to environmental exposures. Whether a health problem will occur or not in any individual is dependent upon many factors, including how much mercury enters your body and how it entered your body, how long or frequently you are exposed to mercury, and how each person’s body responds to mercury.
In the U.S., most fish tissue consumption advisories for “recreationally-caught fish” are due to the presence of mercury contamination. This is also true for commercial fish advisories released by FDA that can be seen on the EPA web site,
As of December 2001, MDE has issued statewide advisories for gamefish and panfish in all freshwater lakes, streams, and rivers and has also monitored mercury levels of numerous species inhabiting the Chesapeake Bay and other tidal waters. The Department has also provided Maryland residents with additional health information in a public information brochure.
Women who are pregnant, nursing or may become pregnant are advised to reduce or eliminate their consumption of certain types of commercial and recreational fish, so that their intake of methyl mercury from fish consumption do not exceed the recommended daily safe dose of methyl mercury that experts feel are without significant risk to health. Individuals can get the most current information on fish consumption advisories by contacting MDE Science Services Administration (SSA - formerly TARSA) at 410-537-3906.
Many of the harmful effects of mercury on people can also be observed in wildlife, particularly fish-eating birds and mammals, providing further evidence of the potential hazards of mercury in the environment. Many researchers utilize experimental animals or sentinel wildlife species to investigate the potential harmful effects of mercury and other environmental contaminants.
Mercury at Home, School, and Work
Through environmental protection and environmental health educational outreach efforts, the general public and members of the private sector are becoming increasingly aware of the health and ecological implications of mercury contamination in the environment (edible seafood, surface waters and sediments, ambient air, indoor air, soils, and municipal waste). The entire family needs be aware of potential exposures to mercury from household uses and sources of mercury., and adults need to be careful and avoid significant exposures to mercury through occupational sources,
Although mercury has been eliminated or reduced in many household and school products (for example, mercury-containing topical tincture of merthiolate and mercurochrome are no longer sold in drug stores), there are still a number of mercury-containing products in your home that you might not realize contain mercury. These include very old bottles of merthiolate and mercurochrome that are red or reddish brown in color, and computer monitors and some old television sets with cathode ray tubes, among other household products.
There are a number of ways that you can reduce your family’s potential exposure to mercury, such as following fish consumption advisory information offered by Maryland, EPA, and FDA. You can also replace mercury-containing glass thermometers. However, there are always times when someone may accidentally break a mercury-containing thermometer and broken mercury thermometers are in fact the most commonly encountered household indoor air exposure to mercury.
When a mercury-containing glass thermometer is broken, it is IMPORTANT TO KEEP CHILDREN AND PETS AWAY FROM THE AREA. IT IS IMPORTANT FOR OLDER CHILDREN TO KEEP THE YOUNGER CHILDREN AWAY FROM THE AREA AND IMMEDIATELY CALL FOR HELP FROM ADULTS. LET ADULTS KNOW THAT THE THERMOMETER HAS BEEN BROKEN, SO THAT THEY CAN CLEAN IT UP ACCORDING TO MDE RECOMMENDATIONS AND PREVENT ANY EXPOSURES TO YOU OR YOUR FAMILY.
Depending on where you work or go to school, there may be other types of exposures to mercury that you may encounter. IT IS RECOMMENDED THAT MEMBERS OF THE GENERAL PUBLIC NOT TRY TO CLEAN UP ANY MERCURY SPILL THAT IS MORE THAN A SINGLE THERMOMETER. IF A MERCURY SPILL LARGER THAN THE CONTENTS OF A SINGLE THERMOMETER OCCURS, CALL YOUR LOCAL HEALTH DEPARTMENT OR MARYLAND DEPARTMENT OF THE ENVIRONMENT FOR ASSISTANCE AND REPORT THE SPILL.
Mercury Reclamation and Disposal
Mercury is also a “waste stream” contaminant. This means that mercury can enter municipal landfills and wastewater treatment plants, and then be discharged to surface waters and aquatic sediments at varying rates, depending on the usage habits and disposal practices of people. Maryland has implemented mercury reclamation centers and household hazardous waste centers to reduce and perhaps one day prevent releases of mercury to the environment. These types of programs also discourage using mercury in schools and businesses, thereby greatly reducing future releases of mercury from accidental breakage of older thermometers, barometers, physician’s sphygmomanometers (blood pressure meters), etc. with mercury being dumped into the municipal trash.
Your cooperation in voluntarily disposing of mercury waste in the recommended manner and in voluntarily participating in other mercury product reclamation efforts assists MDE in helping to protect the quality of Maryland’s environment.
For more information on mercury and a more complete listing of additional MDE web pages on mercury, see the MDE Land Administration mercury page.
Additional links for mercury information can also be found at:
EPA Mercury website
EPA Mercury Maps website