SAN FRANCISCO — For years, the Environmental Protection Agency has endorsed the recycling of ground-up tires to cushion the surfaces of children's playgrounds and sports fields _ the same material used for the Obama family's new White House playground.
Now, the agency is having second thoughts.
EPA scientists are worried that they don't have enough information about potential health risks from chemicals in the rubber material, which is popular because it decreases playground injuries and is low maintenance and weatherproof.
The concerns are disclosed in internal agency documents about a study the EPA is conducting of air and surface samples at four fields and playgrounds that use recycled tires. The study was prompted by other research suggesting potential hazards from repeated exposure to bits of shredded tire that can contain carcinogens and other chemicals, according to the documents.
The EPA scientists cited gaps in scientific evidence, despite other reviews showing little or no health concern. They urged their superiors to conduct a broad health study to inform parents on kids' safety.
Results from the agency's limited study, which began last year, are expected within weeks.
"From everything I've been able to see, I'm not sure there's an imminent hazard but it's something we're investigating," said Michael Firestone, EPA's head of children's health protection. "It's critical to take a look at all the data together."
Communities from New Jersey to Oregon have raised concerns about children touching, swallowing or inhaling lead, metals and chemicals like benzene, zinc and breathable particles from synthetic fields and play yards.
Last week, New York state officials said they found no significant health or environmental concerns in a study of leaching and breathable air above sports fields with so-called tire crumb _ tiny rubber infill pellets that help anchor the synthetic grass blades. Other local studies have reached similar conclusions, examining artificial grass or tire crumb. Several have recommended more research.
"If they really find it's something toxic, I would be concerned," said Alejandro Arroyo, a teacher watching his high school students from June Jordan School for Equity play soccer at San Francisco's Crocker Amazon Park. The scent of tire rubber wafted over the busy, five-field complex as a dozen third-graders flopped onto artificial turf infused with gravel-sized, black rubber.
"We practice here, we eat lunch here," Arroyo said. "Everybody does that. It's a family park."
Scrap tire mulch cushions the ground under the play set that President Barack Obama's daughters use at the White House. It was recommended by the National Recreation and Park Association, which relies on the industry's safety assurances and recommendations by the Consumer Product Safety Commission for cushioning the impact of falls, said Richard Dolesh, public policy officer for the park association.
But New York City officials say their new sports fields will no longer use tire crumbs. Connecticut asked the EPA to study the matter shortly after EPA's Denver regional office recommended the same.
The EPA memo was sent to Washington from the Denver office in January 2008, saying that until more was known, the EPA should take a neutral stance instead of sanctioning recycled tires for play areas. The documents, obtained under the Freedom of Information Act, were provided to The Associated Press by the Public Employees for Environmental Responsibility, an advocacy group that objects to the EPA's endorsement of using recycled tires without a broad scientific risk evaluation.
"It appears that there are valid reasons to take a broader perspective of all potential risks associated with crumb rubber" through a full-blown health study, said the memo from Assistant Regional Administrator Stephen Tuber.
Withdrawing the EPA's endorsement would be premature, said EPA spokesman Dale Kemery.
"Nobody has the evidence at this point" to scientifically justify pulling back, he said.
Along with its own research, the agency will consider studies in New Jersey, California, Connecticut and New York to determine whether more testing is needed. A shortcoming of EPA's study is the small number of locations examined, according to the documents.
The Synthetic Turf Council, an advocacy trade group, says laboratory-based claims of toxicity don't reflect actual conditions.
"The science is clear that synthetic turf crumb rubber infill fields do not present a human health or environmental risk," said Rick Doyle, president of the group.
The CPSC concluded last summer that synthetic fields pose no lead hazard for kids. It tested turf fibers for lead at a few fields. It did not examine chemicals in tire crumbs interspersed with the turf, or playgrounds where children handle mulch made from shredded tires.
A health advisory from the federal Centers for Disease Control and Prevention said older fields may be riskier for lead as wear kicks up turf dust. Not all turf fibers contain lead. The CDC urges eliminating all nonessential uses of lead, which can cause neurological damage in children.
Chemicals in recycled tires could vary by location because tire manufacturers differ, EPA scientists said.