Cleaning up a mercury spill in your school

Mercury is an element that exists in a variety of forms: as a pure liquid that can vaporize, and as organic and inorganic compounds. Liquid mercury, also known as “quicksilver” due to its liquid metallic appearance, has unique physical and chemical properties, and has been widely used in industry, homes and schools.

Where was mercury formerly found in schools?

Chemistry and biology labs: Because of its physical properties, mercury used to be a component of a variety of laboratory equipment (e.g., thermometers, barometers, psychrometers). In addition, mercuric compounds (e.g., mercuric chloride, calomel) were used in chemistry experiments. There still may be mercury compounds and mercury-containing instruments in your school’s science labs.

School nurse’s station: Mercury-containing fever thermometers and blood pressure cuffs were used by school nurses. You may still have mercury-containing instruments in your nurse’s station.

Throughout the school: Mercury-containing thermostats and switches may be found in rooms throughout a school.

Existing thermostats may continue in use, but the law prohibits the purchase, installation or re-installation of mercury thermostats.

New and used fluorescent lamps, which contain mercury, may be stored in custodial areas. Fluorescent bulbs should be recycled whole and unbroken. Bulb-crushing machines that are marketed in some states are illegal in Minnesota because they emit large amounts of mercury into buildings and the environment.

What to do when mercury is spilled in your school

The Minnesota Pollution Control Agency (MPCA) recommends having a professional emergency contractor clean up mercury spills. If the spill is minor, such as one broken fever or lab thermometer or one or two fluorescent bulbs, school or school district staff trained in hazardous materials spill cleanups may take on cleanup responsibilities.

Take immediate action:

  1. Evacuate the spill area. Leave all shoes, clothing and other articles that were splashed with mercury at the spill area.
  2. Wash skin exposed to mercury with soap and water.
  3. Immediately open the room’s outside windows and exterior doors to provide ventilation.
  4. Evaluate the spill: Most spills of elemental mercury have little potential to create health issues as long as the spill is contained and mercury is not pilfered or tracked to another location and not properly cleaned up. If the mercury was spilled on a heat source or if it was somehow vaporized or atomized (e.g., vacuumed), exposures can be severe. Consider evacuating the building. And if someone ingested mercury, call a poison center at 800-222-1222.
  5. Close off the room from the rest of the building by closing all interior doors and windows. Close all cold-air returns so that mercury vapor is not carried throughout the school.
  6. Lower the temperature of the room by turning off the heat to that room. The ventilation and cooling systems to the spill area should be turned off. If possible, all air ducts to the room should be closed temporarily.
  7. Turn off fans unless they vent to the outdoors. Use portable fans to blow mercury-contaminated air outdoors.
  8. Unless the spill resulted from the breakage of only one or two fluorescent bulbs, it should be reported to the Minnesota Duty Officer, who answers calls any time, night or day:
    • 651-649-5451 (Twin Cities metro area)
    • 800-422‑0798 (outside the Twin Cities metro area)
    • 651-297-5353 or 800-627-3529 (TDD).
  9. Hire a professional emergency response contractor or make sure a trained staff person takes responsibility for cleaning up the mercury spill.
  10. Monitor the spill area to ensure that mercury vapor levels meet Minnesota Department of Health criteria (see below).
  11. Properly recycle all mercury waste or dispose of it as hazardous waste. Contact your county solid or hazardous waste office for recycling or disposal information and reporting requirements.

Cleaning up broken fluorescent bulbs

Fluorescent tubes, compact fluorescent lamps, and high-intensity discharge lights used for exterior lighting all contain a small amount of mercury and should be managed as such. It is illegal to put these bulbs in the trash, and when they break, they should be cleaned up in the following manner:

  1. Clear the room of all students and staff.
  2. Open any outside windows, close all interior doors and windows, and leave the room for 15 minutes.
  3. Wear rubber gloves and carefully pick up all glass shards and any remaining powder with duct tape or other sticky tape.
  4. Wash the area with soapy water using disposable towels and dry the area with disposable towels.
  5. If a bulb breaks on carpet, follow the previous instructions. After all visible signs of the bulb have been removed from the carpet, you may vacuum the area.
  6. Put all glass, tape, disposable towels and vacuum cleaner bag in a plastic bag, then add the rubber gloves and seal the bag.
  7. Dispose of this bag in the same manner you would the debris from a larger mercury spill.
  8. If you break more than two bulbs, call the Minnesota Duty Officer for clean up and disposal instructions.

Why is spilled mercury a concern?

Mercury is a toxin that can affect the nervous system of humans. It can also damage the liver and kidneys. Even small amounts of spilled mercury may become a health hazard if it is not properly controlled and cleaned. Heating mercury or failing to clean up a spill can lead to a large exposure or long-term exposure to lower amounts of mercury. Both can impact ones health.

Elemental mercury vapor easily moves from the lungs to the bloodstream. Heating elemental mercury or breathing excessive amounts of vapor from a spill can be very harmful. Ingestion of liquid mercury does not typically result in health impacts because elemental mercury does not pass easily from the gastrointestinal system into the bloodstream. In addition, people usually can avoid swallowing mercury that has been spilled.

Most symptoms of mercury exposure are subtle and reversible upon removal of exposure. Symptoms of a large exposure to mercury may include pink skin, skin rashes or lesions, muscle tremors, personality and behavioral changes, memory loss, and damage to the kidneys and central nervous system.

Spilled mercury is also a concern because it contributes to mercury pollution of the atmosphere. Mercury in rain contaminates lakes, causing fish contamination.

Inhalation exposure criteria

 When assessing sites for mercury contamination, the MPCA uses the Minnesota Department of Health (MDH) criteria for acute and chronic mercury exposure. Acute toxicity generally means that a short exposure period results in an adverse health effect. Chronic toxicity means that symptoms occur following lengthy exposure or a series of shorter exposures.

Short- and long-term exposure risks

MDH acute health-based criteria are used when the exposure is for an hour or less. MDH chronic health-based criteria are used for extended periods or for averaging exposures over a year. When exposures are at or below these criteria, the general public or even vulnerable people (such as children or women of child-bearing age) should not have adverse health effects. However, as mercury concentrations or length of exposure increase to exceed these criteria, the risk of experiencing adverse health effects increases, and any related health effects may become more severe.

Exposure to mercury vapor

The MDH acute exposure criterion for mercury vapor is 1,800 nanograms per cubic meter. This mercury vapor concentration should not be exceeded in students’ or teachers’ breathing space (this does not necessarily include isolated areas, such as inside or under cabinets).

Long-term exposures to mercury vapor should average less than 300 nanograms per cubic meter. Because children and teachers are not in school all the time, the MDH recommends 800 nanograms per cubic meter as a generally protective chronic exposure criterion for schools.

Cleanup standards

If mercury exposures may be occurring in your school, the MPCA and MDH recommend cleanup action until mercury vapor levels meet the MDH chronic exposure criterion for schools (800 nanograms per cubic meter).

A few mercury “nevers”

  • Never heat liquid mercury or mercury compounds. When heated, mercury evaporates rapidly, causing it to go into the air as mercury vapor that can be inhaled.
  • Never use a vacuum cleaner or a broom to clean up a mercury spill. A vacuum heats mercury and disperses it to the air, creating a larger hazard. Brooms break mercury into smaller drops and cause further dispersion.

    The MPCA recommends that so-called “mercury vacuums” be used only when the exhaust is monitored with a mercury vapor analyzer. Improper use of these mercury vacuums releases mercury vapor to the air. The result is the potential contamination of an even larger area. Conventional vacuum cleaners may be used following cleanup of one or two broken fluorescent bulbs, while the area is still being ventilated.
  • Never pour mercury down a drain. Mercury becomes lodged in pipes, pollutes wastewater-treatment plants and makes its way to our lakes and streams. There it can contaminate fish and the animals and people who eat them.
  • Never throw fluorescent or high-intensity discharge lamps in the garbage or trash. These bulbs contain mercury. It is illegal to throw mercury waste in with the regular garbage or trash because of the potential to harm health and pollute the environment. Lamps must be either properly recycled or managed as hazardous waste.

The best advice: Keep mercury out of your school

Because there is a ban on the purchase, use, and storage of mercury in Minnesota schools, you are bound by law to refrain from purchasing products and devices that contain mercury or mercury compounds, except fluorescent lamps.

Fortunately, mercury-free substitutes exist for just about everything that would be used in a school:

  • alcohol (red bulb) and isoamyl benzoate (blue bulb) and digital lab and fever thermometers,
  • electronic thermostats and switches,
  • aneroid blood-pressure units, and
  • digital barometers and other gauges.

Even though fluorescent lamps contain mercury, the MPCA still recommends their use due to their energy savings. Handle and store new and used lamps very carefully to avoid breaking them and releasing mercury. When more than one or two fluorescent lamps are broken simultaneously indoors, a potential mercury inhalation hazard exists. Broken fluorescent bulbs need to be cleaned up like a mercury spill.

Need more help?

Reporting a spill: You must report a mercury spill to the Minnesota Duty Officer unless the spill results from the breakage of only one or two fluorescent bulbs. The Minnesota Duty Officer can be reached any time at:

  • 651-649-5451 (in the Twin Cities metro area),
  • 800-422-0798 (calling from outside the Twin Cities metro area), or
  • 651-297-5353 or 800-627-3529 (TDD).

Obtaining health and safety funding for dealing with a mercury spill: Independent school districts that wish to obtain health and safety funding for remediation or cleanup costs for a mercury spill should contact Michael Oxborough at the Minnesota Department of Education, 651-582-8509, email

For more hazardous waste information, go check out MPCA’s Hazardous waste and problem materials section.

If you have mercury and health-related questions: Email the Minnesota Department of Health at; or call the MDH at 800-657‑3908, press “4.” The MDH can provide health education materials and consultation to your school and community.