(CBS) -- Kids play sports on fields covered in something called crumb rubber.
New research is confirming that the tiny rubber pellets often contain cancer-causing chemicals.
But that is not all.
As CBS 2's Dave Savini reports, the new tests also found there are other problems caused by crumb rubber and much we still do not know about it.
Athletes of all ages competing on synthetic turf padded with tiny crumb rubber pellets from recycled tires are being exposed to numerous toxic chemicals according to the latest testing by Environment and Human Health, Inc. It supports CBS 2's crumb rubber test results from February.
"The major components were benzothiazole compound and polyaromatic hydrocarbons," says Chris Palenik of Microtrace, which conducted the testing.
Environment and Human Health's study at Yale University found 96 chemicals – 20 percent of which are probable carcinogens, a potential cancer risk. They also found skin, eye and even respiratory irritants, some of which could cause asthma symptoms.
But the group says nearly half the chemicals found in the crumb rubber have not been properly studied, so the health effects are unknown.
It is these types of findings, including the unknown, that frustrates people like Teddy Shapiro, a teenage cancer patient.
"It's a rare form of bone cancer," Shapiro says about his disease. "It's called osteosarcoma."
He spent many years playing soccer on crumb-rubber fields and wants a thorough government study done to ensure athlete safety.
Dr. Robert Cohen, from Northwestern Medicine, says there has been a lack of significant, long-term testing of crumb rubber to find out whether there is a health danger.
"We know some of these chemicals do cause cancer," Cohen says. "I think the frightening thing is that we just don't have the information we need."
Environment and Human Health, Inc., calls crumb rubber an "incredibly irresponsible experiment in people's health."
As CBS 2 reported earlier this year, a college soccer coach in Washington gathered information on at least 50 soccer players, mostly goalies, exposed to crumb rubber who got cancer.
However, the Synthetic Turf Council has pointed to almost 60 studies indicating that crumb rubber is safe.
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