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Mercury Poisoning in Pets
Veterinary & Aquatic Services Department, Drs. Foster & Smith
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What is mercury?

Mercury is also known as quicksilver because it is a silver-colored liquid. It is a naturally occurring element that can cause serious environmental and health problems.

What are the common sources of mercury?

Mercury has been used in various industries and as a medical treatment for centuries. Because of its toxicity, its use has become more regulated. The main source of exposure to mercury today comes in the form of airborne particles released when coal, oil, or natural gas is burned as fuel or mercury-containing garbage is incinerated. The airborne mercury can then fall to the ground with rain and snow, and contaminate soil or bodies of water. Lakes and rivers are also contaminated by direct discharges of mercury-laden industrial waste or municipal sewage being emptied into them. In turn, mercury accumulates in fish and can cause health hazards when consumed.

Broken fluorescent lights release a toxic powdery vaporous form of mercuryThere are several common sources of mercury in a household including thermometers, fluorescent lights, button-cell batteries, barometers, thermostats, electrical switches, some blood pressure measuring devices, and in the switches of the lights commonly found in children's athletic sneakers (those that "light-up" with each step).

What are the health problems associated with mercury?

Mercury is toxic to humans and animals, and can cause harm to the nervous system, cardiovascular system, digestive tract, kidneys, and cause birth defects and affect the development of young children. Mercury vapors, e.g., resulting from a broken mercury thermometer, enter the body through the lungs from where the mercury may then be distributed throughout the body. The amount of mercury vapor released from a broken thermometer does not present an immediate health hazard, but extended exposure will cause health problems.

How can I decrease exposure to mercury?

To protect you and your pets from mercury hazards:

  • Choose alternatives to mercury-containing products, for example, switch to electronic thermometers and thermostats.

  • Recycle used fluorescent bulbs, which use mercury in the powder inside the glass.

  • Separate mercury-containing waste and broken or used equipment containing mercury from your trash. Find out if there is a household hazardous waste collection program that will accept these.

  • If you do need to use elemental (liquid) mercury, make sure it is safely stored in a leakproof container. Keep it in a secure space (e.g., a locked closet) so that others cannot easily get to it.

  • Follow your health department's recommendations on the amount of fish you and your family can safely consume.

  • Know what to do in case you are exposed to liquid mercury.

What should I do if there is a mercury spill?

Liquid mercury evaporates at room temperature and these vapors are invisible, odorless, and, at high levels, are very toxic. Upon spilling, liquid mercury will bead up and spread readily. The amount of vapor elemental mercury produces is related to the amount spilled, surface area (amount of beads produced), temperature (vapor increases with warmer air), airflow, and physical disturbance of the spilled material.

You should respond immediately to all mercury spills, such as a broken thermometer. Even small spills can, in some cases, cause high levels of mercury vapors that are unsafe to breathe. Mercury vapors are readily absorbed through the lungs into the bloodstream and are therefore, particularly hazardous. Mercury vapors are also heavier than air and may linger in higher concentrations close to the floor. Children or pets who crawl or play in these areas are at highest risk of breathing in these vapors.

If you break a mercury thermometer or have another type of small mercury spill, follow these nine steps:

  1. ISOLATE THE SPILL AREA: Keep children and pets away. Avoid traffic going through the spill area. Those who may have come into contact with mercury should be directed to remove contaminated shoes or clothing, which should then be double-bagged (one bag inside of the other) and sealed. Otherwise, mercury could be tracked around the home. If the mercury was vacuumed, exposed to heat, or entered the ventilation system, higher mercury vapor levels may exist and could require additional protective equipment and professional expertise.

  2. if mercury is spilled, assemble clean-up suppliesASSEMBLE CLEAN-UP SUPPLIES: Many clean-up supplies are available from hardware stores. The following are some common household articles that could be used to construct an in-home mercury clean-up kit:

  • eyedropper   to pick up the mercury
  • plastic container with lid   to hold the mercury
  • tape (wide, duct, or masking)   to help pick up mercury beads
  • plastic bags with zipper seal   to store mercury-contaminated debris and equipment
  • rubber gloves   to protect hands from mercury contact
  • syringe without needle   to pick up mercury
  • trash bags   for containing mercury waste
  • playing cards or index cards   for collecting mercury beads
  • flashlight   to help see the mercury
  • latex or rubber gloves   to protect your hands
  • PICK UP ALL VISIBLE MERCURY DROPLETS: Inspect the spill area with a bright light or flashlight to help illuminate any hidden droplets. Clean up any beads of mercury by using an index card and rigid piece of paper. With the card, gently push the mercury droplets away from any carpet, fabric, or porous surfaces and toward other droplets to combine them into larger droplets. Slide droplets onto a sheet of rigid paper like another index card or greeting card. You could also use an eyedropper or syringe to pick up the beads of mercury. Adhesive tape strips may also be used to clean up any tiny remaining mercury droplets. Never use a broom or a vacuum on a mercury spill because it will only scatter the mercury droplets, making them harder to find and pick up. Be careful of broken glass fragments.

  • GENTLY PLACE MERCURY INTO AN UNBREAKABLE PLASTIC CONTAINER: Place the mercury into an unbreakable plastic container or zipper-locked storage bag. Avoid using glass since it can easily break. If using a container, tighten the lid securely so that liquid and vapors will be contained. Place the container or bag into another zipper-locked bag. Be sure all bags are zipped tight. If there are glass fragments mixed with the mercury, place the double-bagged mercury into another puncture proof container.

  • CHECK CAREFULLY FOR MISSED MERCURY: Use a very bright flashlight to better illuminate mercury beads in the spill area. If additional assurance is desired, sprinkle powdered sulfur (available from garden supply stores) over the spill area (do not apply to carpet or soft items). The sulfur powder will turn brown when in contact with mercury and help identify any mercury that may have been missed. Collect the powder as was done with the mercury beads. The sulfur will bind with the mercury, reducing the amount of vapor.

  • SET ASIDE EVERYTHING YOU THINK MIGHT BE CONTAMINATED WITH MERCURY: Place all contaminated clean-up materials such as the index cards, eyedropper, gloves, and tape securely into a double bag and label as "Mercury-Contaminated."

  • Clothing and personal belongings that were contaminated or suspected of being contaminated can be placed in a plastic bag, which should then be sealed. Contact your local health department to determine if the contents can be tested for the amount of contamination. If the mercury level is low enough, the clothes and belongings can be safely returned for use. Note that the cost to monitor and clean clothes and belongings could exceed the value of those items. Clean-up cost should be weighed against the item's value to prevent unnecessary expense.

    Note: Everything used during the clean-up procedure should be considered contaminated with mercury unless you are positive it has not come into contact with mercury. Seek advice from your local county health department or department of natural resources on proper disposal.

  • VENTILATE: Try to ventilate the room to the outside and close it off from the rest of the home. Ventilate as much as possible to completely air out the room or spill zone with fresh outside air. Use fans for a minimum of one hour to speed the ventilation.

  • MEDICAL TESTING: If significant exposure of a person or pet is believed to have occurred, you should discuss with your family doctor/veterinarian whether urine mercury tests should be conducted.

  • Special precautions should be taken if mercury was spilled in a high traffic area or a confined area where children or infants play. Young children playing on the floor are particularly at risk to mercury's effects on the central nervous system. Call your local health department to see if additional testing or other measures may be needed.

  • CONSIDER REMOVAL AND DISPOSAL OF CONTAMINATED CARPETING AND OTHER SOFT ITEMS: It takes very little mercury in the air to create unhealthy levels of vapor. Further, vacuuming any surface with mercury will make more vapor. Factors that affect the severity of risk from mercury in carpet or soft-surfaced items include the amount of mercury spilled, how much was recovered, the type of room, and whether young children or pregnant women frequent the room. Local health departments and spill response contractors may be able to monitor for the presence of mercury vapor on contaminated items. However, private testing may be costly. The value of the item should be weighed against such cost and the peace of mind offered by the testing and/or removal of the contaminated item. When removing contaminated items, double wrap them in plastic bags and contact your local health department or Wisconsin Department of Natural Resources for proper disposal.
    (Do NOT expose to heat or incinerate.)

    • DO NOT use a vacuum to clean up mercury. The filters in household and even high efficiency vacuums will not remove mercury vapors. Of even greater concern, the vacuum exhaust will put more mercury vapor in the air. The vacuum will also be contaminated. If you already have used a vacuum to clean a spill, carefully place the vacuum in a double bag, seal the bag, and remove it from the building. Quickly isolate the areas as described below because there may be higher amounts of mercury vapor in the air.

    • DO NOT use a broom to clean up mercury. It will break the mercury into smaller beads, further spreading it and making more vapor.

    • DO NOT touch the mercury with your hands. Use latex gloves for proper protection.

    • DO NOT use household cleaners to clean the spill. Some of them could react with the mercury and release harmful gasses.

    • DO NOT allow people whose shoes have contacted mercury to take their shoes beyond the spill area. Further contamination of the building may result.

    • DO NOT put mercury in the trash. Mercury can be released in the environment and will further threaten human health.

    • DO NOT put mercury or mercury-containing items in a burn barrel. Vapors and smoke will be produced releasing mercury into the environment and create an exposure risk.

    • DO NOT pour or allow mercury to go down a drain. It can lodge in the trap, and produce airborne vapor creating an inhalation risk. It will also lead to mercury contamination of the wastewater system.

    • DO NOT wash mercury-contaminated items in a washing machine. Mercury may contaminate the machine and/or be discharged to the environment in wastewater.

    References and Further Reading

    University of Calgary, Canada. Safe Science Newsletter, June 1998.

    Wisconsin Department of Natural Resources. Focus on Mercury.

    Wisconsin Department of Health and Family Services. General information on mercury spills.

    Wisconsin Department of Health and Family Services. Cleaning up a broken fever thermometer.

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