Millions of old tires are ground up and sprinkled on artificial fields each year. But is the practice safe?

In October, University of Washington women's soccer coach Amy Griffin's appeared on NBC to ask for more research on the materials in artificial turf fields. Her concern? That the ground-up tires used in the turf caused cancer in some of her players. 

Synthetic turf is essentially a carpet of shaggy fake grass, sprinkled with a liberal amount of "tire crumb," made from shredded recycled tires. The crumbs get raked in between the blades of fake grass to prop up the blades and cushion impact. Turf installers, such as Micheal Viscusi of The Philadelphia Turf Company, say it costs less to maintain, uses less water and can withstand more heavy usage than a natural grass field. It also provides a constructive final resting place for recycled tires, which might otherwise be hard to dispose of. An average athletic field can contain over 20,000 recycled tires, according to an estimate by Viscusi. The Synthetic Turf Council puts the number of these fields across North America at over 8,000.

Universities and government agencies have investigated artificial turf for a variety of health concerns—from injuries to staph infections—since the 1960s. But a concern over cancer has not taken center stage until now. And the fact that much of the research on the exposure risk of playing on artificial turf is "limited," according to studies by the Environmental Protection Agency.

"It just doesn't seem like anybody's connecting the dots in terms of chemicals and exposures," said ward commissioner in Mt. Lebanon, Pennsylvania, Kelly Fraasch. Her town recently voted to replace the athletic fields in the town park with artificial turf fields that contain crumb rubber. Fraasch cast the only dissenting vote. She said the studies have not proven to her that artificial turf is safe.

According to the EPA's own reports, known carcinogens like benzene have been identified in some tires. And Fraasch said Vasco's own representatives seemed oblivious to potential health impacts. "I had one of them say to me, because I'd said, 'I've heard these can be flammable,' and he said, 'We took care of that. Now we spray them with flame retardants,'" said Fraasch. "I just looked at him for a second and said, 'Didn't we start removing them from clothing material because they were possibly harmful to children?'"

Child safety is a sticking point for Fraasch and other parents who want information on the the potential link between turf and cancer. And there is cause to investigate that link, because "there are high cancer rates in the tire manufacturing industry," according to public health toxicologist David Brown. Brown works for non-profit Environment and Human Health, Inc., or EHHI, which first responded to questions about artificial turf from a concerned parent in 2007.

That year, EHHI released a report vetting existing studies on turf and containing some original research. That report recommended placing "a moratorium on installing any new fields or playgrounds" until the material's safety could be further investigated.

Brown said one big critique of existing studies is that their methods don't replicate how people actually spend time on these fields – making it impossible to figure out if they are safe. "I saw a risk assessment that I think was done in California that assumed kids would play on the field once in their lifetime," said Brown. He also said that the high incidence rate of the same kinds of cancers – the non-Hodgkin's lymphoma's – seen in Coach Griffin's players points to a specific chemical carcinogen.

The Synthetic Turf Council's website lists 14 studies it says show the material is safe to use. One of these is a study out of Rutgers University funded by the New Jersey Department of Environmental Protection last year. That study put 200mg of crumb rubber —less than a packet of sugar—in artificial biofluids to see what potentially harmful compounds spit or stomach acid could pull out. "Breaking it down this way, we found very little of the metals and of the organic compounds going into any of the fluids," said researcher Clifford Weisel, who is the Deputy Director of the Exposures Science Division of the Environmental and Occupational Health Science Institute at Rutgers University.

But that study simulated only one exposure, and sampled only seven pre-existing fields across New Jersey. It also found that two of these fields contained higher than recommended levels of lead in the artificial grass material. The New Jersey Department of Environmental Protection is also the entity responsible for disposing of tires in the state. "Because this is a retro-waste, the decision was made that the health decisions would be made at the level of the state and local governments," said Brown. "They can't do it."

The Pulse reached out to the Environmental Protection Agency and the Agency for Toxic Substances and Disease Registry (ASTDR) by phone and email for comment. Representatives from the ASTDR responded that they're evaluating a request by New Jersey Representative Frank Pallone to do more research on potential health impacts, and pointed me to existing studies on the EPA's website. These studies include the caveat that they are limited in scope and did not explicitly explore a link with cancer.

Which brings us back to local officials like commissioner Kelly Fraasch, who have to decide what's an acceptable risk for their town. "We only know that we can't put our tires in our garbage, or out on the curb to be picked up...and now we're going to put our kids on a field of the same material," said Fraasch. "That does not make sense to me." So, the commissioner introduced a motion to use a non-tire based infill for Mt. Lebanon's fields. A decision is due Nov. 28.

Cities from San Francisco, California to Ocean City, New Jersey are struggling with similar concerns, and some have halted plans for artificial turf fields.