Concerns about the possible health effects of sports fields and playgrounds made from ground-up tires prompted the U.S. Environmental Protection Agency to conduct a study of air and surface samples at four fields and playgrounds with recycled-rubber surfaces.
Government documents say the study began last year, and the results are expected within weeks, the Associated Press reported.
The EPA launched the limited study at the urging of some of its own scientists, who said there were gaps in scientific knowledge about how repeated exposure to bits of shredded tires might affect children's health.
"From everything I've been able to see, I'm not sure there's an imminent hazard, but it's something we're investigating," Michael Firestone, EPA's head of children's health protection, told the AP. "It's critical to take a look at all the data together."
Communities across the country have expressed concerns about children touching, swallowing or inhaling lead, metals and chemicals like benzene and zinc from artificial fields and play areas.
Results of a New York state study released last week found no significant health or environmental concerns about leaching and breathable air above the artificial sports fields, the AP said. Other local studies examining artificial grass or tire-crumb play areas have reached similar conclusions. Several have recommended more research, the AP said.
But New York City has announced its new sports fields no longer will use tire crumbs.
The EPA's limited study won't be definitive, but, along with studies in New Jersey, California, Connecticut and New York, it could help determine whether more research is needed, the AP said.
The ground covering under the Obama family's new play set at the White House is made of ground-up tire mulch, which was recommended by the National Recreation and Park Association.