Mercury is a naturally occurring element that is toxic to humans and animals. It affects human nervous systems, particularly of young children and fetuses. At room temperature, mercury is a silvery, liquid metal, but it can also evaporate and become airborne like water. Mercury does not break down into less toxic substances.
Mercury used to be common in some products like switches, thermometers, and fluorescent lights. Those uses are less common now, but it’s still found in some products. When these items are broken or thrown away, mercury can escape into the environment. Activities such as burning coal and processing taconite also release mercury into the air.
Airborne mercury circulates in and out of the atmosphere, and may travel long distances before it falls to earth with precipitation or dust. Eventually this mercury ends up in lakes or oceans, where it can accumulate in fish.
One of the primary ways people are exposed to mercury is by eating contaminated fish. As fish eat plankton and smaller fish that are contaminated, mercury concentrations increase. Large fish that are popular in Minnesota, such as bass, walleye, and northern pike, tend to be the most contaminated. Many states, including Minnesota, have fish consumption advisories to inform people about how many meals of fish they can safely eat over a period of time. Learn more about safely consuming fish on the Minnesota Department of Health (MDH) web site.
Inhaling the vapor given off when mercury is heated is also dangerous, as is the mercury that becomes airborne if you break something like a mercury thermometer, barometer, blood pressure cuff, or fluorescent light bulb. Learn more about the health effects of mercury exposure on the MDH web site.
Fish are the main source of food for many birds and other animals, and mercury can seriously damage the health of these species. Loons, eagles, otters, mink, kingfishers, and ospreys eat large quantities of fish. Because these predators rely on speed and coordination to obtain food, mercury may be particularly hazardous to these animals. Research indicates that mercury is accumulating in loons, mink, otters, and walleye.
Keep your home safe from mercury
If you spill mercury in your home, even the small amount from a broken thermometer, it must be cleaned up carefully and quickly to prevent harm to people and pets. Learn more:
MPCA mercury resources