Frequently Asked Questions: Mercury in its liquid form - EH: Minnesota Department of Health


Mercury is a naturally occurring element found in rocks, soil, water, air and living things. It is found in some products and can be a potential health risk for people. Mercury is a liquid at room temperature. In its pure form (often called metallic or elemental), mercury is a shiny, silver-white, odorless liquid. If heated, mercury vaporizes into a toxic, colorless gas that is odorless to people.

Elemental Mercury

Elemental mercury has been used in a wide variety of equipment and consumer products, such as thermometers, blood pressure cuffs, barometers, switches, pressure regulators, skin lightening products and in some types of light bulbs. Elemental mercury that is not in a closed container will slowly give off vapor and can accumulate in indoor air. For example, a broken fever thermometer that is not properly cleaned up (especially in carpet or on fabric) can leave behind elemental mercury that will give off low levels of vapor for many years. Breathing in low levels of mercury vapor for months to years can be harmful, especially for the developing fetus, infants and children. Elemental mercury vapor easily moves from the lungs to the bloodstream. Heating elemental mercury speeds up evaporation and can quickly lead to dangerous vapor levels in a very short time and at high levels can be very harmful, even fatal. On the other hand, eating a small amount of elemental mercury, like the amount in a fever thermometer, is not a serious concern because very little elemental mercury is absorbed through the stomach and intestines. If you do swallow elemental mercury, please contact the Poison Control Center at 1-800-222-1222.

Methyl Mercury

Methyl mercury easily passes from the stomach and intestines into the bloodstream and then can cause damage to the nervous system, especially when the nervous system is developing in fetuses, infants and children. When elemental mercury in the air falls onto lakes and streams, certain bacteria chemically combine it with carbon to form methyl mercury. Fish accumulate methyl mercury from their food. Fish that feed on other fish - such as walleye, northern pike, shark and swordfish - have the highest amounts of mercury. Fish that don't eat other fish, for example sunfish and salmon, have low levels of methyl mercury. Older, larger fish also have higher amounts because methyl mercury builds up in fish over time. Fish provide many health benefits. Fish are an excellent source of low fat protein, omega 3 fatty acids and other nutrients. If you follow MDH’s advice, the methyl mercury in the fish you eat will be safely eliminated between meals. For advice on how to choose which fish to eat and how often, see Fish Consumption Guidance.

Other Forms of Mercury

Mercury naturally occurs in the environment in a salt form or in rock, such as cinnabar. Some inorganic mercury compounds were commonly used in the United States as medicine, but most are no longer in use. Mercury compounds have been used in some products including fungicides, antiseptics or disinfectants. Some traditional medicines, such as skin lighteners or freckle creams, can contain high levels of mercury. All medicines with unknown ingredients should be avoided.

Mercury is a hazardous chemical. Mercury can damage the central nervous system, kidneys and liver. Factors that determine how mercury affects our health include how much mercury gets into the body, how often we are exposed to mercury, other chemicals we might be exposed to and a person’s individual health status. The health effects of mercury can range from none -- to subtle -- to severe -- and even death. Both high level/short-term and low level/long-term exposures can lead to serious health problems.

High level, short-term exposure can cause skin rashes, diarrhea, and respiratory distress. Repeated exposure to low levels, or long-term, low-level exposure, can cause muscle tremors, irritability, personality changes, or rashes.

Nerve damage from mercury may start with a loss of sensitivity in hands and feet, difficulty in walking, or slurred speech. In rare cases it has caused paralysis and even death. The risk varies depending on how much mercury a person is exposed to, how long a person is exposed to mercury, and how often the person is exposed.

Fetuses and children are very sensitive to mercury. Pregnant women and women of child-bearing age should also avoid exposure to mercury.


The greatest health danger from elemental mercury is through inhalation, or breathing in mercury vapor. When elemental mercury is spilled or exposed to the air, it vaporizes slowly. In a warm environment (like a kitchen or on a hot plate) it will vaporize more quickly, resulting in higher indoor mercury levels. In its vapor form, mercury is easily inhaled and extremely toxic. Elemental mercury that is breathed into a person’s lungs quickly moves into the bloodstream and is carried to the brain. If a person is exposed to mercury in air for a long enough time, even a small amount can affect his or her health. Mercury that is released outdoors will eventually vaporize into the air. Normally, the amount of mercury in outdoor air is extremely low, and this should not pose a health hazard.


If someone swallows elemental mercury very little is absorbed through the stomach and intestines into the bloodstream. However, methylmercury in fish is easily absorbed by the stomach and intestines into the bloodstream. It is carried by the blood to the brain and nervous system. View the Statewide Safe-Eating Guidelines for more information about consuming fish.


Very little elemental mercury is absorbed through the skin. If mercury is on the skin, there may be some irritation, and the best way to handle this is for the exposed person to shower with soap. The more serious risk is from the mercury vapor that can be breathed in. Playing with elemental mercury also increases the risk of an accidental spill which could become a long term source of mercury vapor.

The best way to avoid a mercury spill is not to have any mercury in the house. Replace any mercury thermometers in your home with digital thermometers or alcohol (red bulb) thermometers. Replace old thermostats that contain mercury with non-mercury electronic thermostats. Most electronic thermostats can be programmed to automatically decrease fuel use and costs at night or when you are out of the house.

Thermometers, thermostats and other devices that contain mercury, such as barometers and spent fluorescent bulbs or tubes, should NOT be thrown in the trash. Instead, take them to your county's household hazardous waste collection site. Use visit Minnesota Pollution Control Agency's webpage to Find your household hazardous waste collection site.

Spilled mercury, even small quantities in the home, should be cleaned up properly so that people don’t come in contact with it or breathe its vapors. Some ordinary cleanup measures, such as sweeping and vacuuming, are not appropriate when trying to clean up spilled mercury; as they will increase the health risks.

Mercury vapor is odorless, colorless and very toxic. Even though liquid mercury evaporates slowly, a significant amount of mercury vapor can build up indoors after mercury is spilled, and it can be dangerous to breathe these mercury vapors.

For advice about cleaning up a mercury spill in your home, contact the Minnesota Pollution Control Agency by calling the Minnesota Duty Officer at 800-422-0798 or 651-649-5451 anytime, day or night.

You should NOT attempt to clean up spilled mercury yourself unless the amount spilled is no more than what is contained in a fever thermometer or compact fluorescent bulb and the spill did not occur in a warm environment, such as on a hot surface, or in a device that vaporizes liquids (i.e. a humidifier). .

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For questions about exposure, please contact us.

Updated Thursday, March 29, 2018 at 12:36PM