Is There Mercury in Your Gymnasium Floor?

by Joseph L. Sbarra, CIH

Certified Industrial Hygienist with > 35 years experience

How Did Mercury Get in Gymnasium Floors?

From the early 1960’s to the mid 1990’s, schools and other commercial facilities installed polyurethane (rubberized) flooring in indoor gymnasiums, cafeterias and outdoor running tracks and field houses.

Polyurethane flooring became popular as it was less expensive than hardwood flooring, is less resistant to damage, and is easier to maintain.  Most commonly, the process involved pouring the floor in three parts: 

• A base layer of liquid resin and rubber.
• A middle layer polyurethane elastomer.
• A thin top layer polyurethane coating, which allowed for sports graphics and school/company logos to be added.

Some manufacturers’ flooring included a compound that contained a form of mercury called phenyl mercuric acetate (PMA), which was used as a catalyst in production.  Even today, 30 - 50 years after installation; floors with the PMA catalyst still emit mercury vapors into the air!


What is Mercury?

Mercury is an element; it is a shiny, silvery metal sometimes also called quicksilver.

It is the only metal that is a liquid at room temperature.  Mercury gives off vapors at room temperature; the higher the temperature, the more vapors are released.  Mercury vapors are colorless and odorless.

Mercury has historically been used in thermometers, barometers, fluorescent light bulbs and dental amalgams (used for filling teeth).


Are Mercury Vapors a Health Concern?

They can be, the effect on a person’s health depends on a several factors including:

1. Mercury exposure levels
2. Length of exposure
3. Age (young children are more vulnerable)
4. Current state of health

Mercury is a poison, it is not a known cancer-causing agent.  Mercury is absorbed into the body primarily by breathing the airborne vapors.  Exposure to mercury can affect the central nervous system (CNS), which is very sensitive to mercury.  Exposure to lower levels of mercury vapors for prolonged periods of time (which is the most likely case with regard to gym floors) can cause non-specific health effects such as:

• Irritability
• Sleep disturbance
• Excessive shyness
• Tremors
• Coordination problems
• Changes in vision or hearing
• Memory problems

Most of the effects of mercury resulting from prolonged low level exposure are reversible, once exposure is terminated and the mercury has left your body. 1


What is the Approach to Dealing with Gym Floors?

There is a basic approach that can be applied to gym floors that contain mercury. 

The first step is to conduct bulk testing to determine if mercury is even present. If bulk testing results are below 1 ppm, then no further action is needed.

If the bulk testing results are positive, the next step would be to conduct mercury vapor screening to determine airborne mercury levels.  This can be done with a handheld mercury vapor meter that has the capability to detect < 300 nanograms of mercury per cubic meter of air (that's a really small amount!).

Based upon the mercury screening results, a Management Plan would need to be developed to  ensure that airborne mercury vapor exposure levels remain below recommended limits.  A Management Plan should include:

• Periodic mercury vapor screening - to verify airborne levels.
• Ventilation controls - to control and reduce accumulation of mercury vapors.
• Temperature controls - to keep gymnasium temperatures from elevating and increasing the mercury vapor levels
• Procedures for repair & maintenance - damaged areas can emit higher levels of mercury vapor levels than undamaged areas.

Lastly, a decision needs to be made with regard to Long-term Planning: manage the mercury gym floor in place or remove it.  Several factors should be considered, including:

• Effectiveness of the Management Plan - are levels remaining below recommended limits?
• High levels of mercury during removal - several studies have shown that mercury vapor levels are typically above federal worker exposure limits during removal.  Steps need to be taken during removal to ensure that workers are protected and that mercury does not contaminate the remainder of the school/building.
• Budget and cost considerations - removal is an expensive process as the waste generated will be hazardous and will have to be disposed of in accordance with EPA and state environmental regulations.

We Have a Polyurethane Floor…What Do We Do Next?

• Contact an Industrial Hygiene consulting firm– they should have the expertise to help identify and address this specific concern.  Industrial hygiene is the science of anticipating, recognizing, evaluating, and controlling chemical (that includes mercury), physical, and biological hazards. 
• Make sure that the firm has a certified industrial hygienist (CIH) on staff. The CIH is the “gold standard” of certifications for health and safety.
• Ask to speak directly with the CIH about your specific case, not with a technician or lower level scientist.   A CIH will be able to answer any questions you may have.
• Ask if the CIH has specific experience with evaluating mercury in gym floors.  If they do not, consider another firm.

Footnotes:
1.  Agency for Toxic Substances and Disease Registry, ToxFAQs TM for Metallic Mercury, March 2001.

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