Hidden Toxins in School Gym Floors — Mercury Vapor
Over the past fifteen years, the relatively common occurrence of mercury in rubberized gym floors has been confirmed by several state health departments. The presence of mercury in gyms or other areas in schools that use the same type of synthetic polyurethane flooring is a scary revelation as the mercury will vaporize at room temperature (77°F or 25°C). As a vapor, mercury is easily inhaled by persons in the immediate area, leaving children particularly vulnerable — they are closer to the floor where the vapor is more dense and particularly hazardous to their developing nervous systems.
Currently, there are permissible exposure limits established for mercury and its various forms, but there are no regulations or standards established regarding these potentially hazardous gym floors. State health departments, such as Ohio and Minnesota, have made significant headway in researching the extent of off-gassing from the floors, sampling methods, potential health hazards and possible remediation options. Even though there are no regulations in place, the New Jersey Education Association (NJEA) has stated that it is the “responsibility of local boards of education to eliminate any mercury exposures in schools from these floors.” Do you know if you have one of these floors in your school? Do you know what actions to take if you have a suspect floor? Read on to find out.
History of Mercury in Gym Flooring
The type of flooring that may have mercury in it is a synthetic, rubber-like type of floor composed of polyurethane. Most of these floors seem to have been installed between the 1960s and 1990s. In order to spread and level out the polyurethane, a mercury-containing catalyst was used called Phenyl Mercuric Acetate (PMA). This type of flooring was not just used for gym floors either — it can also be found in multi-purpose rooms, cafeterias, auditoriums, stages and indoor/outdoor tracks. Not all of these types of floors contain mercury, however. Some companies did not use a PMA catalyst during installation. It is also currently unknown as to how many of these floors exist across the country and whether they are still being installed using the mercury-containing catalyst.
There are a number of companies that used PMA as a catalyst to install their floors. If your gym floor was installed by one of the companies below, consider getting the floor tested for mercury (this is not a comprehensive list of all the companies, however):
- 3M Corporation produced Tartan floors and Tartan track
- American Biltrite Rubber Co. produced Amtico rubber flooring
- Crossfield Products Corp. produced Dex-O-Tex
- Athletic Polymer Systems (APS)
- Mondo Rubber
- Pitzer, Inc.
- Selby, Battersby and Company
- Sportan Surfaces, Inc.
- Robbins Sport Surfaces produced Chemturf
Recently, in January of 2017, a New Jersey school in Burlington Township discovered mercury was present in their gym floor during preliminary testing prior to major renovations of the school building. The amount of mercury was high enough to classify the gym floor as a hazardous material which could not be placed into a regular landfill. The school administration had no idea prior to testing for mercury that there was a potential health hazard sitting in their gymnasium. However, the vaporization of mercury from synthetic flooring has actually been known for almost two decades.
Starting in 2002, several gyms in Minnesota school districts were found to have ambient mercury concentrations above the RfC of the EPA — some of them significantly higher than this permissible level. The Minnesota Department of Health conducted mercury vapor analysis at several gyms in the state, as well as at a private university where they developed mercury floor emission and gymnasium ventilation models. The analyses, along with research conducted by a few other agencies (Ohio Department of Health; Michigan Department of Community Health), have provided us with comprehensive, yet disconcerting, information regarding just how much mercury is being emitted from these poured polyurethane floors.
Mercury Vapor Data
It is not known whether the PMA converts to elemental mercury after volatilizing in the air of the gym or prior to volatilization, however, the process does happen slowly over time. It has been determined that the half-life of the mercury in the floors is approximately sixteen years, meaning only half of the mercury in the flooring will vaporize in sixteeen years. In 2006, the Minnesota Pollution Control Agency (MPCA) studied the mercury vapor concentration of a Minnesota gymnasium in order to gain more information on the phenomenon. This gym flooring contained 170μg/g (ppm) of mercury. The average concentration of the mercury vapor in the air was 2.7μg/m3. This concentration is significantly above the Reference Concentration Level (RfC) determined by the Environmental Protection Agency (EPA) — 0.3μg/m3. In addition, this concentration was found at a temperature of only 21.7ºC (71.1ºF) when the amount of mercury vapor doubles for every 9ºC (16.2ºF) increase in temperature! This means, that on a sweltering hot day during the summer, if the gymnasium temperatures reach even just 30.7ºC (87.3ºF), that concentration will double, reaching 5.4μg/m3.
A measurement of 5.4μg/m3 is, importantly enough, above the limit determined by the EPA, but also already half the limit determined by the Center for Disease Control (CDC) and the Agency for Toxic Substances and Disease Registry (ATSDR) for schools (10μg/m3). The good news is that this average concentration was determined while the gym’s ventilation was off and all windows and doors were closed — the worst case scenario. The same study also determined that if the ventilation was turned on but windows and doors still closed the concentration decreased to 0.05μg/m3 — a concentration well below all the limits mentioned previously. Opening the windows and doors in addition to the ventilation only brought this down to 0.04μg/m3.
The results of the above study show that without proper ventilation, mercury vapor levels emitted from these synthetic floors will reach unacceptable concentrations. Just opening windows and doors is not enough — schools will need ventilation that actively pulls the outside air inside for air exchange. If such actions are taken, it is usually the case that the mercury vapor concentrations will be decreased to the point that they are below the most conservative limit (0.3μg/m3). To be sure the ventilation is actually taking care of the problem though, for schools or businesses that have these polyurethane synthetic floors, testing is necessary. It is recommended that bulk samples of the floor be taken to test the amount of mercury. If the concentration is less than <1ppm, then the floor was not manufactured using a mercuric catalyst; if the concentration is between 1-20ppm, then it is unlikely that the vapors will reach levels of concern, especially with proper floor maintenance, ventilation and periodic testing; if the concentration is greater than 20ppm, then levels may approach or exceed levels of health concern under specific conditions and disposal of the floor should be seriously considered.
Although the mercuric floors will off-gas more frequently if damaged, with cracks, seams or holes, the concentration of mercury vapors in the air are both temperature and ventilation dependent.
What Does This Mean for Children?
Mercury vapors are especially hazardous to children as their bodies and their nervous systems are still developing, leaving them particularly vulnerable. In addition, due to their lighter body weight, the exposure is much higher than for an adult. The main concern regards the central nervous system and kidneys. Mercury is considered neuro-, nephro- and immunotoxic. Any damage done to the nervous system from mercury exposure will most likely be permanent. When mercury vapor is inhaled, about 70-80% of it is absorbed by the lungs into the bloodstream. It can also travel directly from the pharynx to the brain. Elemental, or metallic mercury, is lipid soluble and capable of crossing the blood-brain barrier. Mercury in the elemental form (Hg0) can travel and spread throughout the body for several minutes before being oxidized. Once it gets to the brain, it will oxidize and remain there as the oxidized form cannot cross the blood-brain barrier — therefore, it accumulates in the worst possible place of a human’s body.
The oxidized form of mercury (Hg++) will bind to certain chemical groups on proteins, inhibiting important enzymatic reactions and causing cellular damage. Symptoms of mercury exposure include:
- Psychological disturbances (diffidence, mental hyperactivity, temper outbursts, depression, etc.)
- Decreased immune system function
- Excessive salivation
In terms of the most important methods of exposure to worry about with these floors are 1. inhalation of the vapor or dust particulates 2. dermal contact with the flooring and 3. ingestion of residues or dust particulates. In addition, the mercury vapor from the floor can contaminate other items in the gym such as items composed of plastic or wood. The vapor is also odorless and colorless rendering it impossible to detect without specific instrumentation.
Protecting Children From Mercury Exposure
The first step a school should undertake is taking a bulk sample of their gymnasium floor if it is suspected to be one of the described synthetic, rubber-like, polyurethane floors and testing it for mercury, especially if it was manufactured by one of the aforementioned companies. Further air testing should be conducted if the concentration of the floor exceeds 1ppm. NJEA has stated a set of recommendations for schools to take in order to responsibly take care of any issues arising from synthetic gymnasium flooring:
- If installing a new gymnasium, verify with the manufacturer that it has not been produced with a mercury catalyst
- Do not cover, seal or encapsulate mercury-containing floors — this may just add more chemicals into the mix
- Keep the gymnasium floor and area cool and well-ventilated
- Conduct scheduled and periodic air testing
- Remove the floor as soon as possible using environmental and health safety precautions, especially if significantly damaged and/or contaminated
- Actively ventilated with fresh air at least 2 hours before use
- Ensure ventilation of the gymnasium during buffing or vacuuming of the floors
By following these steps and being responsible about potential mercury exposure to school children, you are doing your part in keeping children safe and bringing attention to these potential hazards. Further research needs to be conducted to determine how exactly the PMA is being converted to elemental mercury, but in the meantime, we can all lower the exposure potential for school children.
Karl Environmental Group has experience sampling for mercury in school gymnasiums and is more than willing to visit your school and help you determine whether there is contamination or high mercury vapor present in your school building or business.