Synthetic rubber floors come in various types and thicknesses.
They all have what I would consider fairly strong to very strong perceptible offgassing levels.
Though this is not a flooring material I would use myself or recommend to any of my chemically sensitive clients, I will go over which types are the best choices.
Because rubber can sometimes be the only option under certain types of heavy weights and equipment, it could be used in some areas of the gym, but it should be minimized as much as possible if you want to have the lowest possible VOC levels.
Recycled rubber might be marketed as “eco-friendly” because it’s recycled, but otherwise, recycled rubber flooring made from “crumb rubber” (recycled tires) contains the highest levels of contaminants and chemicals of concern.
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Synthetic Versus Natural Rubber Flooring
Synthetic rubber is more durable than natural rubber latex.
I have seen brands that are part natural rubber and part synthetic, like Mondo Sport.
I don’t believe any brands are 100% natural rubber.
What is Rubber Flooring Made of?
Rubber flooring can be made with recycled SBR rubber (most often tires), new (virgin) SBR rubber (synthetic or a synthetic/natural mix), and EPDM virgin rubber color chips as the main ingredient.
Tarkett makes a rubber flooring where almost all ingredients are on the Declare label.
Rebonded Versus Vulcanized
Anything labeled rebonded rubber uses a polyurethane adhesive to hold the flooring together.
Polyurethane glue does have noticeable offgassing, which most people would consider fairly high.
Vulcanized and virgin rubber are usually heat-pressed.
Vulcanized rubber is preferable from an offgassing standpoint over polyurethane-bonded rubber.
Some manufacturers use sulfur in their binding agents, which certainly adds to the VOCs and odor.
Other Components
Some rubber gym floors are mixed with vinyl, like the brand Roppe, which I do not consider an improvement.
A rubber and cork mix like those from Ecore can be quite good.
Flame retardants can also be added.
Tarkett lists their flame retardants as Huntitte, Hydromagnesite, and Aluminum Trihydrate.
The Lowest VOC Rubber Flooring
Look for these attributes when choosing the healthiest rubber floor:
- Virgin rubber, not post-consumer recycled (especially not tires)
- Vulcanized rubber, not rebonded
- No PVC added
- Calendared rubber as the top layer (on top of vulcanized) reduces offgassing somewhat. This is the best out of all the rubber floors I have seen, in terms of VOCs (Ecore Aurora)
- Thinner rubber sheets are preferable to thicker rubber (less to offgas)
- A mix with cork can be fine (like Ecore brand), it is similar to the pure vulcanized rubber
- A mix with natural latex can reduce offgassing
- Turf on top of rubber can reduce the offgassing of the rubber layer (Ecore FIT turf)
- Time does help rubber to offgas. If you can air this out for a few weeks or a few months before installation that would be a great help
- Greenguard Gold certification can be reached by some brands
VOCs/Offgassing of Rubber Flooring
Rubber flooring is the only flooring type I know of that has measured above 500 μg/m3 VOCs (see Floorscore certificates here).
(Here are some other measurements for context: GreenGuard Gold laminate has around 9 μg/m3, Mohawk formaldehyde-free laminate 0.009 μg/m3, natural linoleum ≤10 μg/m3, a number of bamboo floors are around 9-10 μg/m3).
A study by California’s Public Health Institute titled Tire-Derived Rubber Flooring Chemical Emissions revealed offgassing of xylene, butylated hydroxytoluene, ethylbenzene, toluene, formaldehyde, and acetaldehyde from recycled rubber flooring.
Benzene and carbon disulfide were above the health threshold in one or two samples.
Sulfur is commonly used in virgin rubber flooring. Whereas rebounded uses polyurethane adhesives. Both of these produce offgassing odors.
Some brands do meet GreenGuard Gold VOC levels (like Mondo) which is a fairly low level of offgassing and makes it suitable for most people (those who are chemically sensitive are not likely to be able to use any SBR rubber flooring).
The odor of rubber flooring does go down, although slowly, and may never fully go away.
Metals and Other Contaminants in Rubber Flooring
If you do go with a rubber flooring you can ask to see testing of heavy metals (especially lead) as well as PAHs (polyaromatic hydrocarbons).
However, the Healthy Building Network does not find this testing to be comprehensive enough since it’s only a spot check.
Recycled rubber flooring may contain more contaminants than virgin rubber says the Healthy Building Network.
Recycled rubber flooring is made from recycled tires, this is also called crumb rubber.
Many chemicals in the recycled rubber, such as distillate aromatic extract (which makes up a large percentage of the product and creates polyaromatic hydrocarbons), lead, phthalates, BPA, styrene, nano carbon black, vulcanizing agents, accelerators, and plasticizers remain in recycled rubber.
Levels of lead have tested above the Consumer Product Safety Commission (CPSC)’s limit for children’s products (100 parts per million). (Source)
Cities and towns in Washington, Connecticut, California, Minnesota, and Maryland have proposed or enacted moratoriums or bans on crumb rubber (recycled tire rubber) and/or artificial turfs for playgrounds and/or fields.
The European Union has banned recycled tire rubber infill (this is used as an infill for turf).
The Healthy Building Network does not recommend the use of recycled tire flooring in interior applications, especially where children may come into direct contact with the flooring.
Seal in the Offgassing and Contaminants of Rubber Flooring with Paint?
It’s difficult or maybe impossible to seal up rubber because most paints and sealers don’t stick well to it, especially if it has a rough surface.
I tried sealing rubber flooring samples with shellac but the shellac did pull away from the rubber within a few weeks so I would not count on being able to seal it.
Reduce the Offgassing in Rubber Flooring/Rubber Mats:
- Air + heat + time – rubber takes a long time to offgas in my experience. Even a year outside was not nearly enough for me. However, this is still the main way to offgas any material. Just don’t leave it in the sun too long, as rubber breaks down in the sun.
- Wash it down with a) a mix of water and vinegar, b) lemon juice, or c) peppermint oil on a damp cloth, or soak it if possible (if it’s a smaller mat) in a mix of water and baking soda, or water and dish soap.
- If you need to do something immediately, encase it or put down charcoal, zeolite, or cat litter on top of it. A more temporary solution can be to place down aluminum foil if the offgassing is not bearable for a chemically sensitive person.
Corinne Segura is an InterNACHI-certified Healthy Homes Inspector with certifications in Building Biology, Healthier Materials and Sustainable Buildings, and more. She has 10 years of experience helping others create healthy homes. You can book a consult here.
Sources
Healthy Building Network: Avoiding Contaminants in Tire-Derived Flooring
Tire-Derived Rubber Flooring Chemical Emissions Study: Laboratory Study Report
A review of potentially harmful chemicals in crumb rubber used in synthetic football pitches
Corey
Hi, thanks so much for posting this article. We just gut-renovated our house and moved in 2 weeks ago. My husband had rubber mats AND artificial turn installed in the new basement gym (half and half) and it smells so, so strong I am quite worried about it. Even opening the door to the basement from the kitchen, you can smell the odor all the way up the stairs. My husband insists that the house has a great HVAC system and fresh air is constantly being circulated, and really is not concerned at all. However, we have a 7 year old son who loves being down in the space, kicking a soccer ball or even going on the stationary bike. Additionally, my husband works out anywhere from 1-3 hours several times per week and will be spending significant time in the space.
I honestly want to rip out the floors and install something healthier, but this is obviously a huge expense and complicated (since I am so worried about this but my husband is NOT). I guess I am looking for some guidance about how to navigate this situation in which I am very concerned about the health of my husband and son using this terrible smelling space (and the artificial turf also worries me because of what I’ve read about that), but my husband is not concerned at all.
Is there a way to get objective testing to determine the safety of the materials in this space and monitor the off-gassing? Is there a way to have a neutral third-party come in and say for certain whether the space is safe and suitable for heavy use (time spent, and heavy breathing due to exercising) for an adult and a child? Additionally my son is sliding all over the artificial turf while shooting the soccer ball, and this contact with his body/clothing is also concerning. Overall, I am feeling extremely anxious about the gym space and need guidance on how to either convince my husband that there are legitimate health concerns (via an expert and/or testing) or be assured that the materials/off-gassing is okay and I need to just get over it. Thank you so, so much.
Corinne Segura, Building Biologist
I don’t do much testing, I’m not an industrial hygienist or similar. I focus mainly on material specification and what’s in them. You can do a VOC test here https://www.thegreendesigncenter.com/product/home-air-check-iaq-testing-systems/?=4122
I don’t have a list of labs to check for metals, PAHs, PFAS (in the turf), etc.
There is an article on turf though.