In the early 1960’s, 3M developed Tartan Brand floor covering, a rubber-like polymer promoted as a durable substitute for wood floor gymnasiums and running surfaces.1 Manufacturing involved mercury as a catalyst2 to help the end product retain its soft texture. 1 The 3M Tartan product became popular until discontinued in 1980. Polyurethane flooring is manufactured by combining two liquid resins to form a durable, resilient surface. 3
Since 3M’s introduction, rubberized sport surfaces have been manufactured by several other companies, including, but not limited to:
- Athletic Polymer Systems
- Dynamic Sports Construction (Versaturf)
- Crossfield Products (Dex-O-Tex)
- Mondo Rubber
- Pitzer, Inc.
- Robbins Sport Surfaces (Chem Turf & Pulastic Systems)
- Selby Battersby & Company
- Surfacing Systems
- Whittaker Synthetic Surfaces (Chemothane)3
Some of these manufacturers produced floors similar to the 3M Tartan product as late as the early 2000s.
What are the potential issues with these floors?
Mercury is the only common metal that remains liquid at room temperature. It also slowly evaporates at room temperature.4 Long-term exposure to mercury vapor affects the central nervous system3 of humans.
The on-going release of mercury vapor can be of concern if it exceeds Environmental Protection Agency (EPA) or state guidelines. The product itself becomes of concern when removed for replacement with another flooring type creating a disposal issue. According to the flooring manufacturers and test data, the finished flooring typically contains 550 to 1,100 parts per million (ppm) of mercury when first installed. Vapor levels on warm days in gymnasiums with mercury-containing floors may reach 1 to 5 micrograms per cubic meter of air, or 100 to 500 times that of normal, ambient air levels. 3 The Agency for Toxic Substances and Disease Registry considers mercury vapor concentrations at or below 1 microgram per cubic meter an acceptable level of exposure in a residential setting. 3 Levels for industrial and institutional settings are not established.
Bottom line, the ongoing vapor levels may require removal of these floors for health reasons, and the amount of mercury used by a particular manufacturer may require management of the debris as hazardous. Unfortunately, there is no technology for treating mercury-catalyzed polyurethane flooring to remove and recover the mercury so that the rest of the flooring material can be managed as solid waste without restriction.
Where to Start?
First, determine if your flooring is a mercury-catalyst polymer floor to begin with. There are other types that are similar that do not involve mercury. You may need to contact the original manufacturer.
If you have a mercury-catalyst polyurethane floor in your school or facility, specialists have recommended having the floors tested by an independent, certified lab. The EPA provides testing standards for both the vapor levels and amount of mercury present in the floor itself, should it need to be removed.2
Once the levels have been tested, the testing firm may offer more than one potential approach. There may be no need to take further action based on safe vapor levels. If the floor is aging, it may be worthwhile to consider ongoing continued management of the floor in place to avoid the costs of removal. Depending on total and leachable vapor levels, there may be an option that involves covering the floor with the replacement flooring if the polymer floor is exhausted from a usability standpoint. In some cases, a ventilation system may provide an adequate reduction in vapor levels, allowing continued safe use. Only a certified, well-qualified testing facility or industrial hygienist familiar with this issue should make recommendations based on your circumstances, and both state and federal requirements.
3M, in a January 2006 letter to the Oregon Environmental Toxicology Program, agreed with the OETP recommendation that a qualified industrial hygienist be involved in studying what levels of personal protective equipment may be required for workers removing MCPF.5
If You Keep the Floor: Maintenance Issues
Testing facilities that qualify and are certified to perform vapor and content mercury testing may be able to perform in-use testing during actual maintenance procedures. If the plan being considered includes continuing to maintain the existing floor, it may be necessary to test under conditions that disturb the floor structure, such as screening, to find how much vapor is released during those procedures.
Every floor and environment offer different challenges. State laws vary. This is why qualified testing is important to your plan. Testing labs should also be qualified to provide cost estimates of the various options they find available.
1 Ohio Bureau of Environmental Health, “Mercury Exposure, Tartan Brand Polymer Flooring”
2 Minnesota Pollution Control Agency, “Disposal guidance for mercury0catalyzed polyurethane flooring and subflooring”
3 Gandee & Associates, Inc., “Mercury Contamination of Polyurethane Flooring”
5 Oregon Dept. of Human Services, “Health Consultation: Salem-Keizer School District, 3M Flooring”
The information in this article is deemed accurate, but no article can substitute for the incorporation of professional testing and advice. The goal of this article is to increase knowledge of the issues and encourage measurement of any potential mercury health issues.