The California Office of Environmental Health Hazard Assessment (OEHHA) has ruled that recycled tyres used as crumb rubber (SBR) in synthetic turf are not likely to harm users or spectators.
Following an extensive study, the OEHHA stated that there is no evidence of significant risk of cancer or other health problems from this recycled rubber to players, coaches, referees and spectators, based on the available data, even for young athletes.
The state has over 900 synthetic turf fields for sports.
“This study should ease concerns about the safety of crumb rubber use in synthetic turf fields,” said OEHHA director Kris Thayer. “Athletes of all ages can use these fields without parents worrying about this commonly used material.”
Many fields use crumb rubber, small granules produced by grinding up recycled waste tires, as infill material placed between the synthetic grass blades. This infill helps keep the blades upright, provides cushioning, and improves traction during play. In fact, SBR was instrumental to the introduction of long-pile synthetic turf surfaces that are favoured by football, rugby and American Football players these days. As it was a widely and cheaply available material that also provided a recycling opportunity for end-of-life tyres that were piling up all over the world, in the absence of a solution to discard these, SBR infill became very prominent in the early 2000s.
This started to change around 2017 when it became evident that these particles could also become an environmental nuisance if they migrated outside the playing surface to the surrounding environment. A growing fear off minerals leaching from the particles polluting the environment or particles ending up in the food chain, has forced authorities around the world to respond.
The European commission has banned the sale of SBR and any other polymeric infills that are used for synthetic turf surfaces from October 2031.
Informing California’s circular economy
OEHHA studied this material to inform California’s sustainability goals. California’s waste tire program sets standards for safely managing waste tyres and explores appropriate markets for materials that might otherwise be landfilled. “Protecting public health is our top priority, and California is committed to making sure waste tyres are managed safely so they don’t litter communities or pose risks to residents,” Calrecycle director Zoe Heller said. “CalRecycle appreciates the work of OEHHA and its partners to advance our understanding in support of a cleaner, healthier circular economy.”
Comprehensive study design
To evaluate safety, OEHHA tested 35 synthetic turf fields. The sampling accounted for both old and new fields, as well as fields from every climate region in California. Multiple samples from each field were collected to account for variations in source materials. OEHHA also collected air samples both during active use of the field and when no use occurred. OEHHA’s groundbreaking study focused on more than 100 chemicals that could pose a risk — unlike past studies that looked at only a small number of chemicals. To identify the full suite of chemicals present, OEHHA coordinated with the Lawrence Berkeley national lab to simulate sweat and digestion and identify chemicals to which the public could be exposed.
To understand how people might be exposed to the chemicals found, OEHHA worked with researchers from UC Berkeley and the University of Arizona. They studied how soccer players might contact crumb rubber—through the skin, breathing, or swallowing small pieces. The team surveyed more than 1,000 soccer players, aged 7 to 71, about how they play, like sliding or diving on the field. They also recorded players during games and practices to see how often they touched the turf. Because goalies dive the most, the study used goalie data to estimate risk for players. Researchers also looked at the chemical risk to toddlers who might crawl onto the field.
No significant risk found
OEHHA found no acute risk to athletes, referees, coaches, or spectators, including toddlers. In most cases, risk of sensory irritation, cancer, harm to the reproductive system or a developing foetus, or other health effects was negligible.