Turf Wars

March/April 2009

Is the crumb rubber in artificial turf harmful to people or to the environment? The research says the material is safe, but tire recyclers worry that the concerns alone are enough to damage this important market.

By Marc Hequet

It seems like the perfect example of solving multiple problems at once. Take scrap tires, granulate them to form crumb rubber particles the size of grains of sand, and pour that material—alone or with sand—in a layer several inches thick over artificial turf fields.

Crumb rubber infill is a valuable market for scrap tires. Tire piles once were a blight on the landscape, sometimes catching fire and all but impossible to extinguish. Moreover, old tires hold water that gives disease-bearing mosquitoes a lush choice of breeding areas. Now most of those tire piles are gone because new markets for recycled tires have developed. They're used in soundproofing, asphalt road surfaces, patio blocks, paints, automotive weather-stripping, brake pads, hoses, shoe soles—even new tires.

Though only about 4 percent of scrap tires become athletic and recreational surfaces—a category that includes artificial turf infill, shredded rubber playground cover, and running tracks—it was one of the fastest-growing segments of the industry from 2003 to 2005, according to the Rubber Manufacturers Association (Washington, D.C.). In a 2006 market report, RMA expected the crumb rubber infill market to double in three years.

Crumb rubber infill holds the artificial turf in place and holds the blades of grass upright. It improves the field's drainage and makes it spongier and safer for athletes than previous generations of artificial turf, says Anthony Cialone, chief operating officer of Florida Tire Recycling (Port St. Lucie, Fla.). "Instead of a dense, abrasive rug, crumb rubber athletic fields' fiber surface is soft, silky—like new blades of grass in a spring meadow," he says. "Rug burns are a thing of the past." With growing nationwide concerns about childhood obesity and the importance of play spaces, more communities are installing artificial turf, which reportedly is more durable, requires less maintenance, and is more cost-effective over the long term than natural grass. (Cialone says clients report annual savings of $30,000 to $60,000 per field per year on maintenance costs compared with natural grass.) The number of "third-generation" infilled artificial-turf fields in the United States grew from seven in 1998 to 3,500 in 2008, according to the Synthetic Turf Council (Atlanta).

That popularity might have led to today's backlash, however. Crumb rubber, like regular dirt, gets into every nook and cranny on the human body. Whether it's diving soccer goaltenders or panting football players who stick their noses into the turf every day during the season, athletes inhale dust from the field, swallow the granules, and rub them against cuts and bruises. Parents and other critics began to wonder whether such close contact with the crumb rubber was harmful to human health and whether fields of this material could damage the surrounding environment. Though more than a half-dozen studies in the United States and Europe have given the material a green light, the criticisms persist, leading some government agencies to call for more research and a moratorium on the use of crumb rubber. Those in the tire recycling industry worry that even if every study comes up clean, the damage to crumb rubber's reputation might be irreversible.

Cataloging the Concerns
You can sum up most critics' concerns with crumb rubber infill with just three questions: What chemicals are in crumb rubber, are those chemicals harmful, and are those chemicals getting into humans or the environment in dangerous levels when crumb rubber is used in artificial turf?

"Our concerns are the compounds and the chemicals that are in rubber tires," says Nancy Alderman, president of Environment & Human Health, a nonprofit in North Haven, Conn., that focuses on environmental risks to human health. The tires "are ground up into tiny 'crumbs' and distributed over the plastic or nylon synthetic grass. When these fields are played on, dust is created from the rubber tire ‘crumbs,' and this dust is able to go deep into the lungs and distribute the toxic chemicals throughout the body."

Tire rubber does contain some nasty stuff. Its makeup varies from manufacturer to manufacturer and brand to brand as tire producers try to create a product with specific performance characteristics. Studies have found potential hazards, including polycyclic aromatic hydrocarbons, volatile organic compounds, semivolatile organic compounds such as phthalates, benzothiazole, and certain metals. Studies of used tires have identified additional substances that probably bond to tires during their road use, including alkylphenols and benzene. Some of those materials are potential carcinogens; others can be lung irritants, contribute to air pollution, or are harmful if swallowed in sufficient quantities.

That answers questions one and two, leaving the controversy almost entirely to question three. Once crumb rubber is scattered on playgrounds and playing fields, do the chemicals leach into groundwater, outgas into the air, or get into the bloodstream through skin contact or digestion in sufficient amounts to constitute a risk?

What the Studies Say
Industry representatives who have looked at the studies on crumb rubber's potential health and environmental impact are mystified by the fears. Jerry Swensen, president of Auburndale Recycling Center (Auburndale, Wis.) and of ReMA's Scrap Tire Processors Chapter, points out that tires wear down all the time during routine use, and roads and highways must be lined with powdered tire rubber. If crumb rubber is a hazard, Swensen muses, "every single person in the United States is going to keel over tomorrow."

Crumb rubber "is a good material. It's very safe," says Jonathan Levy, ReMA's director of state and local programs. "It does not pose a significant threat to human health." Any carcinogens it does contain are present at "minute" levels, he says. The research measuring crumb rubber's impact on human health and the environment supports that claim:

• A 2007 California literature review of tire shreds in playground surfaces (a material that's larger than the granulated rubber used as artificial turf infill) found it "unlikely that a onetime ingestion of tire shreds would produce adverse health effects." Any leaching of carcinogens into the digestive system as the rubber is digested results in negligible additional cancer risk—less than 1 in 10 million according to one study, less than 4 in 100 million according to another. Estimated cancer and noncancer risks to children who incur repeated hand-to-mouth contact with the shredded rubber over a 12-year period were similarly insignificant. In terms of environmental impact, the study concluded that "it is unlikely that the use of shredded tires in outdoor applications such as playground surfaces would result in the leaching during rain events of high enough concentrations of chemicals to cause [toxic] effects" to any of a wide variety of organisms.

• A May 2008 literature review by TRC (Windsor, Conn.) for the New York City Department of Health and Mental Hygiene evaluated 11 previously conducted human health risk assessments of crumb rubber in artificial turf. Each assessment used different assumptions and evaluated different crumb rubber constituent materials, but "all had a similar conclusion: exposure to [chemicals of potential concern] may occur, however the degree of exposure is likely to be too small through ingestion, dermal [contact] or inhalation to increase the risk for any health effect."

• A July 2008 RMA-sponsored literature review by ChemRisk (Pittsburgh) concludes that "adverse health effects are not likely for children or athletes exposed to recycled tire materials found at playgrounds or athletic fields" and "no adverse ecological or environmental outcomes from field leachate are likely." The report notes that heating during the tire manufacturing process causes physical and chemical reactions that bond potentially harmful chemicals into the material "such that they are inhibited from release into the environment." Neither indoor nor outdoor use of crumb rubber creates adverse health effects, the study found. Like many building materials, tires do emit VOCs slowly over time, and some critics worry that high outdoor field temperatures could accelerate these emissions to a harmful level. The report calls this possibility "extremely unlikely."

• European studies by INTRON (Sittard, Netherlands) and the Dutch National Institute of Public Health and the Environment "have concluded that there is no health risk" from PAHs, potential carcinogens that are present in crumb rubber, for athletes playing on artificial turf, says Ulbert Hofstra, an INTRON senior consultant. Further, INTRON's research showed that leaching of zinc oxide from crumb rubber into the environment is at acceptable levels in properly constructed fields.

• A December 2008 report conducted by Milone & MacBroom (Cheshire, Conn.) with the input of the Connecticut Department of Public Health looked at concentrations of three chemicals of concern in the air above artificial turf fields during the summer, when the field temperature was as high as 151 degrees F—conditions likely to maximize any emissions of these substances. The test found "no detectable concentrations" of two of the chemicals in the air above the field or upwind or downwind of the field. The third was present "at a very low concentration" directly above one field, possibly because the field recently had been groomed.

The firm also looked at stormwater drainage from the fields and concluded that "metals do not leach in amounts that would be considered a risk to aquatic life as compared to existing water quality standards." The report added that "metals will leach from the crumb rubber but in concentrations that are within ranges that could be expected to leach from native soil."

The gist of all this research is that "crumb rubber pellets have been used for more than 10 years with an unblemished record of safety," said Marty Sergi, president of tire recycler Perma­Life Products (Guttenberg, N.J.), in testimony to the New York City Council's Committee on Parks and Recreation in February. Or, as Swensen puts it, "I have yet to see any definitive evidence that this material is harmful to kids."

Continued Concerns
Critics of crumb rubber in artificial turf are not satisfied with the existing research. "What we recommend is, get more data, and until you get more data, stop using the stuff," says David Brown, a public health toxicologist with Environment & Human Health. Brown notes that sources of crumb rubber are anything but uniform "and therefore cannot be characterized for safety using studies with small sample sizes." The industry "could do proper studies if they wanted to. They're passing studies off that are just not accurate" because of too few samples, he says. Without further research, public concerns about crumb rubber are placing a potentially promising industry at risk, he warns. If someone gets sick and blames crumb rubber, rightly or wrongly, "an industry, irrespective of potential, could be destroyed," he says, and its partisans might "not be able to salvage it."

Brown's organization supports a moratorium on crumb-rubber use in playgrounds and athletic fields until further testing. The idea puzzles leaders of the turf industry, who say the issue has been studied enough. "When you consider all the benefits of synthetic turf, why is it good to suspend all of those benefits for a period of time to study something that's already been declared safe to humans and the environment in numerous independent and current research [reports]?" asks Rick Doyle, president of the Synthetic Turf Council.

That's not to say there are no avenues for further research. In RMA's 2008 report, ChemRisk researchers conclude there are "no short-term or urgent research needs," but more research would "enhance the weight of evidence used in risk communication." In particular, the report calls for further assessment of particle exposure at indoor and outdoor fields and of outdoor airborne concentrations of VOCs in high temperatures. New York City's report also suggests looking at emissions and particulate matter from outdoor fields—and comparing that data with that collected from natural grass fields and other sites in the community to get a fix on how much of the bad stuff comes from other sources in urban settings. It also calls for further study of crumb rubber from different source materials and created via different processing techniques.

At the same time, critics have raised other concerns about artificial turf fields that are not solely related to their crumb rubber content. Artificial turf absorbs heat from sunlight much more readily than grass—it gets up to 60 degrees F hotter, according to research conducted by Columbia University's Center for Climate Systems Research (New York). This heat is a potential danger to the athletes on the field and contributes to the temperature of the surrounding environment. (The synthetic grass blades trap heat as much or more than the crumb rubber, according to Colum­bia researchers.) Some wonder whether bacteria and other pathogens can build up in artificial turf playing fields. "Blood, sweat, skin cells, and other materials can remain on the turf because the fields are not washed or cleaned," said California state Sen. Abel Maldonado in a January story in the San Jose Mercury News. "It's like playing on a giant used Band-Aid." (Products exist to sanitize fields, and one maintenance manual recommends sanitization be done twice a month, according to a March 2008 report in Environmental Health Perspectives.) Further, one field in New York City was found to have elevated lead levels, which New York's parks commissioner has surmised came from a manufacturing facility that previously occupied the property.

These combined concerns have been enough to lead some government agencies to revisit their support of artificial turf fields. California Sen. Maldonado passed a law that orders state agencies to study the health and environmental impacts of synthetic turf fields. The Connecticut legislature is considering a moratorium on the use of the material and commissioning additional research to be completed in 2010. And in February, New York's Department of Parks and Recreation decided to remove crumb rubber from the one lead-contaminated field, stop installing it in new fields, and replace existing crumb rubber in the remaining fields at the end of the material's 10-year expected lifespan.

Potential Industry Impact
Tire recyclers worry that if research shows that some tire brands have higher levels of certain hazards than others, they might be forced into time-consuming, labor-intensive, and costly tire sorting to produce a product free of those hazards. "It wouldn't make it worthwhile for the tire recycling business to make crumb rubber," says Aaron Santarosa, vice president for business development with Innovative Waste Recovery (Niagara Falls, N.Y.).

Further, the universe of recycled tire products is not so large that the industry can afford to lose the crumb rubber infill market, says ReMA's Levy. In testimony to the New York City Council Committee on Parks and Recreation, he noted that about 13 percent of all recycled rubber that New York state generates—from a total of nearly 21 million scrap tires every year—gets used in artificial turf. New York City's 89 artificial turf fields make it a major consumer of that crumb rubber, which "is helping to strengthen markets for recyclable tires and support an economically sustainable model for tire recycling while at the same time providing an environmentally suitable use for crumb rubber," he said.

If there is not sufficient market demand for crumb rubber products, Levy testified, "there will be no place for the processed rubber to go." The result will be that tires are less likely to get recycled and more likely to end up in illegal and hazardous tire piles or in landfills (which also is illegal in New York), or get burned for energy recovery. Levy urged the committee to "consider the science, instead of emotion, and do what is best for our environment"—to continue to use crumb rubber infill in artificial turf fields. •

Marc Hequet is a writer based in Minneapolis.

Is the crumb rubber in artificial turf harmful to people or to the environment? The research says the material is safe, but tire recyclers worry that the concerns alone are enough to damage this important market.