As of January, there have been 200 nationwide cases of cancers in young athletes that played on synthetic turf—many of them lymphoma, which is uncommon in the age group. In 2013, the U.S. Environmental Protection Agency withdrew earlier safety assurances and called for new, more comprehensive studies.

A majority of professional and college athletes strongly prefer natural turf because those playing on synthetic turf suffer about 50 percent more knee and ankle injuries.

Other playfields use “crumb rubber” infill made of ground-up used tires formerly considered hazardous waste. Thus, sports players may be exposed to dozens of chemical compounds, most of which have never been tested for health impact; some of those tested are believed to cause cancer, birth defects, developmental and reproductive disorders and infertility.

 
Primary source: epa.gov