Skip to main content

About Mercury

Mercury is a naturally occurring element (Hg on the periodic table) that is found in air, water and soil. It exists in several forms: elemental or metallic mercury, inorganic mercury compounds and organic mercury compounds. Elemental or metallic mercury is a shiny, silver-white metal and is liquid at room temperature. If heated, it is a colorless, odorless gas.

Mercury Sources

Mercury sources

Mercury is released into the air, water and land and it cycles between them due to its ability to change forms. Mercury gets into the soil through natural breakdown of rocks, disposal of mercury in landfills and atmospheric deposition. It enters the water through runoff, atmospheric deposition and when mercury from products is poured down the drain. Mercury is released to the atmosphere through coal-fired utility and incinerator emissions, as well as evaporation from water and land. Once mercury enters this cycle, it can remain in the environment for years as it accumulates. It cannot be removed, but it can be prevented from ever entering the environment.


The sources of mercury are varied because the element was used in the production of many products and energy. It is less widely used today in products due to its significant health impacts. Efficient mercury-free alternatives exist to replace almost all uses of mercury. When replacing a mercury product, please recycle the mercury and buy a new, mercury-free replacement.

Listed below are some of the most commonly used mercury products.

Source Alternatives
Barometers Digital/Aneriod
Dental mercury amalgam Gold, composites
Fluorescent light bulbs There is not an alternative as energy-efficient at this time
Lab thermometers Alcohol
Manometer Digital/Aneriod
Medical fever thermometers Digital
Paints Latex paint made after 1990
Pesticides/fungicides Any product after 1995
Sphygmomanometer (blood pressure cuff) Digital/Aneriod
Switches (lights, safety) Ball bearing or mechanical
Thermostats Electronic or snap-action
Vaccines containing thimerosol Thimerosol-free vaccines

Environmental and Wildlife Impacts

Environmental and wildlife impacts

Mercury is a heavy metal that has the ability to bioconcentrate and biomagnify up the food chain, meaning it both accumulates in the body over time and incrementally increases at each level of the food chain. Mercury is mutagenic, teratogenic, carcinogenic, embryotoxic and has cytochemical and histopathological effects. Once mercury enters the body of an animal or a person, it can affect the function and development of the central nervous system, as well as cause other adverse health impacts such as reproductive and behavioral problems.

In wildlife, mercury exposure poses the greatest health risk to fish-eating birds and mammals, such as bald eagles, loons and river otter. Birds are particularly at risk for mercury poisoning because many species exclusively eat mercury-laden fish. They are also long-lived animals and therefore accumulate mercury in their bodies over a long period.

Additional facts

  • In mammals, mercury exposure causes teratogenic, mutagenic and carcinogenic effects (Eisler 1987). Neurologic and central nervous system disorders are also common in mammals.
  • In aquatic organisms, low concentrations of mercury can adversely affect reproduction, growth, behavior, metabolism, blood chemistry, osmoregulation and oxygen exchange (Eisler 1987).
  • Sublethal effects of mercury on birds include adverse effects on growth, development, reproduction, blood and tissue chemistry, metabolism and behavior.
  • Mercury exposure can also result in ataxia and muscle disorders, as well as histopathological changes.
  • In just about all species, the developmental stages of an organism are the most sensitive.

Health Impacts

Health impacts

This video from Dartmouth University [exit DNR] explains how mercury enters the seafood we eat, why eating low-mercury fish is important for good health and the need to keep mercury out of the environment.

Individuals exposed to mercury are most likely exposed to the organic species of this chemical (e.g., methylmercury). Human health effects associated with methylmercury include severe neurological disorders in infants exposed during pregnancy. Children exposed to mercury may suffer from developmental problems and damage to the kidneys and digestive system. The nervous system is very sensitive to all forms of mercury. Symptoms include irritability, shyness, tremors, changes in vision or hearing and memory problems. Exposure to the vapors can cause effects such as lung damage, nausea, vomiting, diarrhea, increases in blood pressure or heart rate, skin rashes and eye irritation.

Bioaccumulation and biomagnification

Mercury is particularly toxic to living organisms because it bioaccumulates. Bioaccumulation is the process by which organisms take up a contaminant more rapidly than their bodies can eliminate it. Thus, mercury accumulates in the body over time. If mercury is continually ingested it can build up to toxic levels.

Mercury becomes even more hazardous to organisms higher in the food chain because it biomagnifies. Biomagnification is the incremental increase in a contaminant's concentration at each level of the food chain. For example, humans eat large fish, which eat lots of small fish, which eat lots of plants. Mercury bioaccumulates in every organism along the way, and the human will ingest all of the mercury accumulated during each step.

Eating fish

Although some human exposure to mercury is short-term due to mercury-containing equipment breakage and spills (acute exposure), most human exposure occurs through regular consumption of fish contaminated with methylmercury (chronic exposure). Wisconsin has issued a statewide fish consumption advisory for all inland waters due to mercury contamination.