National Toxicology Program

National Toxicology Program

NTP Synthetic Turf/Recycled Tire Crumb Rubber Research


Synthetic or artificial turf is a surface of artificial fibers and other components made to look like natural grass. It is used in professional sports stadiums and increasingly at recreational athletic fields and on playgrounds. Since its introduction in the 1960s, the use of synthetic turf has grown. Today in the U.S., over 11,000 synthetic turf fields are in use.

In a synthetic turf field, infill materials are spread between the “grass” fibers to provide cushioning and traction. The infill typically consists of “crumb rubber”—shredded rubber particles made from recycled automotive tires—often mixed with sand.

In recent years, the use of tire crumb rubber infill has led to public concern for potential health risks. As athletes and children dive and play on synthetic turf surfaces, crumb rubber particles have been found to cling to clothing, hair, and skin. This could lead to breathing, unintentionally ingesting, and skin contact with tire crumb or chemicals that may leach out of the crumb rubber. Currently, limited research is available on which to judge whether playing on these fields might impact health.

NTP Research Activities

NTP plans to conduct research to enhance the understanding of potential health impacts of chemicals released from synthetic turf with an emphasis on the crumb rubber. NTP is exploring how to mimic human exposure conditions to crumb rubber or its component chemicals. NTP has received some crumb rubber samples that were obtained from recycling facilities and is doing preliminary work to characterize the crumb rubber materials chemically to understand what chemicals might be released from the particles and under what exposure conditions. Based upon those results, NTP plans to carry out short-term studies in rodents and cellular and molecular studies. NTP’s research program is in response to a request in November 2015 from the California Office of Environmental Health Hazard Assessment as part of its Environmental Health Study of Synthetic Turf.

NTP is located at the National Institute of Environmental Health Sciences, part of the National Institutes of Health.