Synthetic Turf Field Recycled Tire Crumb Rubber Research Under the Federal Research Action Plan: Final Report Part 2 – Exposure Characterization

The goal of the research under the Federal Research Action Plan on Recycled Tire Crumb Used on Playing Fields and Playgrounds (FRAP) is to characterize potential human exposures to the substances associated with recycled tire crumb rubber used on synthetic turf fields. The results of the research activities under the FRAP are being documented in two parts. The previously released Part 1 Report (EPA/600/R-19/051, available at: http://www.epa.gov/TireCrumb) documents the tire crumb characterization activities and results. This Part 2 report documents the results from the pilot exposure characterization research study conducted by EPA and CDC/ATSDR, and includes the supplemental biomonitoring study conducted by CDC/ATSDR (Appendix A). Part 2 also includes future research recommendations that could provide additional insights into potential exposures to recycled tire crumb rubber used on synthetic turf fields. A pilot-scale human exposure measurement sub-study was implemented to further develop and deploy appropriate sample collection methods and generate data to better understand potential exposures that may occur when individuals frequently use synthetic turf fields. A subset of the participants that provided questionnaire responses were asked to participate in the exposure measurement pilot study based on their field usage. Field use scenarios anticipated to be among those with relatively high potential exposures due to frequency and duration of time spent on the field and the potential for contact with synthetic field materials were the focus of the study. A set of personal, biological, and field environmental samples was collected around a sport or training activity performed on a participating synthetic turf field. Personal and environmental samples were analyzed for metals, volatile organic compounds (VOCs), and semi-volatile organic compounds (SVOCs). For the biomonitoring pilot, blood and urine samples collected before and after participant practice sessions were analyzed for selected metal and polycyclic aromatic hydrocarbon (PAH) metabolites, respectively. Following the pilot-scale biomonitoring effort, ATSDR designed and conducted a supplemental biomonitoring study measuring PAH urinary metabolites for a larger number of synthetic field users and included athletes playing on natural grass fields for comparison (Appendix A). Researchers utilized information from the literature and data collected in this study to conduct exposure pathway modeling on six selected chemicals for athletes using synthetic turf fields with tire crumb rubber infill. This effort aimed to elucidate which exposure pathways are likely to be the biggest contributors to total exposure for different types of tire crumb rubber constituents; explore whether data produced in this study can improve our exposure estimates, particularly for the dermal and ingestion pathways; assess the availability, robustness, and adequacy of tire crumb and exposure measurement data, and data for exposure model parameters in the context of accuracy and uncertainty for exposure estimation; and prepare examples of modeled estimates of background exposures from residential and dietary sources for comparison with exposure estimates for synthetic turf field users. It is important to note that the study activities completed as part of this multi-agency research effort were not designed, and are not sufficient by themselves, to directly answer questions about potential health risks. Other studies may aid in this regard. Overall, we anticipate that the results from this multi-agency research effort will be useful to the public and interested stakeholders for understanding the potential for human exposure to chemicals associated with recycled tire crumb rubber infill material used on synthetic turf fields.

Impact/Purpose

In the United States, synthetic turf fields are used at municipal and county parks; schools, colleges, and universities; professional sports stadiums and practice fields; and military installations and are designed to simulate the experience of practicing and playing on grass fields. First introduced in the 1960s, synthetic turf fields have evolved over time from first-generation systems made of tightly curled nylon fibers to third-generation systems typically made of polyethylene yarn fibers. These third-generation systems typically use small pieces of recycled tires, referred to as “recycled tire crumb rubber” (or simply “tire crumb rubber”), to fill the space between the polyethylene yarn fibers. The recycled tire crumb rubber (sometimes mixed with sand or other raw materials) is added for ballast, support for the synthetic grass blades, and as cushioning for field users. Third-generation synthetic turf field systems are widely used today. There are between 18,000 and 19,000 synthetic turf fields in the United States, with 1,200 – 1,500 new installations each year, and about half of those are replacements.[2] It is estimated that millions of people use and/or work at these fields. Some parents, athletes, schools and communities have raised concerns about the use of recycled tire crumb rubber on synthetic turf fields. To help address these concerns, the Centers for Disease Control and Prevention/Agency for Toxic Substances and Disease Registry (CDC/ATSDR) and the U.S. Environmental Protection Agency (EPA), in collaboration with the Consumer Product Safety Commission (CPSC), launched a multi-agency research effort in February 2016. This multi-agency research effort, known as the Federal Research Action Plan on Recycled Tire Crumb Used on Playing Fields and Playgrounds (FRAP), is focused on assessing potential human exposure, which includes conducting research activities to characterize the chemicals associated with recycled tire crumb rubber and to identify the ways in which people may be exposed to those chemicals based on their activities on synthetic turf fields. Also, the FRAP includes characterizing emissions and bioaccessibility to differentiate what is present in the recycled tire crumb rubber from what people may actually be exposed to from recycled tire crumb rubber. The research laid out in the FRAP is not intended to be a risk assessment. Like other studies, this research has limitations, and risks cannot be inferred from the information and conclusions found in this study. Prior to initiating the FRAP, most studies examining these potential risks have been considered inconclusive or otherwise incomplete. Based upon available literature, this research effort represents the largest tire crumb rubber study conducted in the United States. The information and results from the effort will fill specific data gaps about the potential for human exposure to chemical constituents associated with recycled tire crumb rubber used in synthetic turf fields. It is important to note that the study activities completed as part of this multi-agency research effort were not designed, and are not sufficient by themselves, to directly answer questions about potential health risks. Other studies may aid in this regard. Overall, we anticipate that the results from this multi-agency research effort will be useful to the public and interested stakeholders for understanding the potential for human exposure to chemicals associated with recycled tire crumb rubber infill material used on synthetic turf fields.

Citation

Thomas, K., E. Irvin, A. Guiseppi-Elie, A. Ragin-Wilson, AND J. Zambrana. Synthetic Turf Field Recycled Tire Crumb Rubber Research Under the Federal Research Action Plan: Final Report Part 2 – Exposure Characterization. U.S. Environmental Protection Agency, Washington, DC, EPA/600/X-24/020, 2024.