What is Mercury?

Mercury is a naturally occurring metal that can be released by both natural and human activities. It can be found in air, water, soil, and biota.

At its core, elemental or metallic mercury (historically known as quick silver) is a shiny, silver-white metal, and is liquid at room temperature. It is used in older thermometers, fluorescent light bulbs and some electrical switches. When dropped, elemental mercury breaks into smaller droplets which can go through small cracks or become strongly attached to certain materials. At room temperature, exposed elemental mercury can evaporate to become an invisible, odorless toxic vapor. If heated, it is a colorless, odorless gas.

How do Fish accumulate mercury?

Fish absorb mercury from the water when it passes over their gills and as they feed on other aquatic organisms. Mercury levels increase as larger predatory fish eat smaller fish, this is known as bioaccumulation. Bioaccumulation is the general term describing a process by which chemicals are taken up by a plant or animal either directly from exposure to a contaminated medium (soil, sediment, water) or by eating food containing the chemical. Exposure to small amounts of mercury over time from fish consumption, can have toxic effects on human nervous and cardiovascular systems, especially on the developing nervous system of children and fetuses.

Inland lakes top predators (such as Musky or Northern Pike) can attain high levels of mercury compared to other fish, due to bioaccumulation. This why GLIFWC recommends eating smaller fish on the bottom of the lake food web such as whitefish, herring, bluegill, crappie, perch, or sunfish.

Where does Mercury come from?

Natural Sources of Mercury

Mercury becomes a problem for the environment when it it is released from rock and ends up in the atmosphere and in water. These releases can happen naturally. Both volcanoes and forest fires send mercury into the atmosphere.

This airborne mercury can fall to the ground in raindrops, in dust, or simply due to gravity (known as “air deposition”). The amount of mercury deposited in a given area depends on how much mercury is released from local, regional, national, and international sources.

Human Sources of Mercury

Since mercury occurs naturally in coal and other fossil fuels, when people burn these fuels for energy, the mercury becomes airborne and goes into the atmosphere. In the United States, power plants that burn coal to create electricity are the largest source of emissions; they account for about 44 percent of all manmade mercury emissions (Source: 2014 National Emissions Inventory, version 2, Technical Support Document (July 2018)

Other causes of mercury emissions

Burning oil that contains mercury
Burning wood that contains mercury
Burning mercury-containing wastes, including:
- Wastes from the manufacture of Portland cement
- Consumer products that contain mercury, like electronic devices, batteries, light bulbs and thermometers, that are thrown into garbage that is incinerated
Using certain technologies to produce chlorine
Breaking products that contain mercury
Burning iron ore, coke and limestone in electric arc furnaces used to produce steel
Using coal-fired boilers in many industries to generate forms of thermal heat like steam

The burning of municipal and medical waste was once a major source of mercury emissions. A reduction in the use of mercury along with state and federal regulations, however, has led to a decrease in emissions from this source by over 95%.

Photos on this page were retrieved from blue-growth.org, chemistrytalk.org, npr.org
Content seen on this page was retrieved from the U.S. EPA, Basic Information about Mercury page.

GLIFWC • P.O. Box 9 – 72682 Maple Street • Odanah, WI 54861 • (715) 682-6619 • glifwc.org

Page updated

Google Sites

Report abuse