Mercury is found in three forms in the environment: Elemental, Inorganic and Organic. The toxicity of mercury to humans is dependent upon its form, concentration and exposure pathway.
Mercury emissions into the environment result from both man-made and natural sources. Natural sources of mercury emissions include volcanic activity, forest fires, and the off-gassing of soils, rocks and the oceans. There is no direct scientific evidence of the total amount of naturally-released mercury. However, estimates range from 13 million pounds per year to 36 million pounds per year.
Man-made mercury emissions are estimated to represent less than half of the total mercury emitted into the environment. Estimates vary, but approximately 5 million pounds per year are believed to come from man-made sources.
Man-made sources of mercury emissions include chemical and industrial processes, metal smelting, home heating oil, medical waste incinerators, coal-fired utility boilers, agricultural operations, and solid waste disposal facilities.
Municipal solid waste combustion was once one of the largest known sources of mercury emissions. However, today, because of reduced mercury in consumer products and advanced pollution control devices on municipal waste combustion facilities, these facilities are an insignificant source of mercury emissions into the environment.
Health risk assessments completed over the past several years for new and existing waste-to-energy plants consistently reveal that the levels of mercury emissions result in exposures which are 100 times less than the threshold health effects standard established by federal and state regulatory agencies.
Mercury can be absorbed through inhalation, skin contact or ingestion. Mercury can travel a long way from the point of release, settle in the soil and drain into surface water bodies. Once in water, Mercury is converted to methylmercury by bacteria. Water borne creatures pass this toxin up the food chain. The concentration of methylmercury increases the higher you go in the food chain.
Low exposure to mercury can cause immune system dysfunction, muscle tremors and irritability. High exposure can cause speech and hearing problems, respiratory problems and sometimes death. Fetuses and young children are at greatest risk due to the ongoing development of their nervous systems. They could suffer from developmental problems in learning, walking, talking and birth defects.
Manufacturers have largely replaced mercury in their battery products. Most batteries manufactured prior to 1980 contained mercury. Button batteries, disc-like batteries used in hearing aids and cameras may contain mercury. Any disk battery made prior to 1994 should be suspect.
Source reduction, product reformulation, and increasingly effective battery recycling programs have reduced mercury in trash by about 90% since 1990, according to the EPA. Pollution control equipment on waste-to-energy plants thereafter remove about 90% of the remaining mercury in the waste stream that is used as a fuel to generate power. Currently, AAA, AA C, D and 9 volt batteries are manufactured mercury-free.
The use of mercury by U.S. manufacturers will decline even further due to the virtual elimination of mercury from alkaline batteries and aggressive recycling and product substitution at hospitals, homes, and businesses.
As a good conductor of electricity, mercury is often used in switches. Temperature-sensitive switches and tilt switches used in thermostats often contain mercury. Automatic shut off switches used in clothing irons and some top-loading freezers could also contain mercury. Check with manufacturers for mercury-free alternatives.
Fluorescent and high intensity discharge (HID) lamps contain mercury. Breaking the bulb will release mercury in vapor form. Look for “low mercury lamps” often with green end caps. Keep burnt out bulbs in a protected place until they can be recycled safely.
Blood Pressure Gauges may contain up to 1.5 pounds of mercury. Aneroid units are mercury-free.
Older barometers and thermometers may contain liquid mercury if they have a silvery liquid. If they contain a red or blue liquid, they are most likely mercury-free.
When you are ready to dispose of a product containing mercury, store it in an unbreakable plastic container and put it away in a safe place where it won’t be touched, especially by children and pets. Then, call your local health department for a list of places in your community where you can drop the product off for safe and proper handling. Some communities hold thermometer swaps where you can drop off your old glass mercury thermometer for a free non-mercury one.
