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Characterization of Recycled Tire Crumb Rubber Used on Synthetic Turf Fields in the United States
Citation:
Thomas, K., E. Irvin-Barnwell, A. Guiseppi-Elie, A. Ragin-Wilson, AND J. Zambrana. Characterization of Recycled Tire Crumb Rubber Used on Synthetic Turf Fields in the United States. 2019 SETAC North America Annual Meeting, Toronto, CANADA, November 03 - 07, 2019.
Impact/Purpose:
Tire crumb rubber from recycled tires is widely used as infill material in the 12,000+ synthetic turf fields in the United States. Tire crumb rubber is a complex material, with many potential chemical substances, presenting challenges for assessing human exposures. As part of U.S. Federal Research Action Plan on Recycled Tire Crumb Used on Playing Fields tire crumb rubber samples were collected from recycling plants and synthetic turf fields around the United States. Multiple analytical methods were applied to measure a wide range of particles, metals, VOCs, and SVOCs. The research is designed to improve our understanding and knowledge of tire crumb rubber material for assessing synthetic field user exposures. The Federal Research will be of interest to synthetic turf field users, communities and schools, and industry stakeholders.
Description:
Crumb rubber from recycled tires is widely used as an infill material in synthetic turf fields which has raised issues concerning potential exposures. However, recycled tire crumb rubber is a complex material which presents challenges when evaluating potential exposures (i.e., what is in the material as well as how people are actually exposed). As part of U.S. Federal Research Action Plan on Recycled Tire Crumb Used on Playing Fields and Playgrounds, researchers collected recycled tire crumb rubber samples from across the U.S (nine tire recycling plants; 25 outdoor and 15 indoor synthetic turf fields) and characterized the samples for chemicals as an initial step in characterizing exposure (with a total of over 3000 analyses). Multiple analytical methods were applied to characterize particle size; metals, volatile (VOCs) and semi-volatile organic compounds (SVOCs). Particle size analysis used a sieve method to generate seven particle size fractions for each sample, ranging from ≤ 0.063 to > 4.75 mm. Twenty elements were measured by microwave acid digestion and ICP-MS analysis. Forty-nine PAHs, phthalates, thiazoles, amines, and other SVOCs were measured by solvent extraction with GC/MS/MS and LC/TOFMS analyses. Releases of SVOCs and thirty-one target VOCs (including BTEX chemicals, formaldehyde, styrene, and 1,3-butadiene) from tire crumb rubber were measured by dynamic emission chamber testing at 25° and 60°C. Suspect screening and non-targeted analyses were applied to tentatively identify additional VOCs and SVOCs associated with the material. Bioaccessibility of metals was measured using simulated gastric fluid, sweat plus sebum, and saliva at 37°C. When compared to previous studies, the mean concentrations measured for most metal and SVOC chemicals were similar. While many chemicals are present in recycled tire crumb rubber, exposure may be limited based on what is released into air or biological fluids, but this needs confirmation. For the microbial analysis, all tire crumb rubber samples collected from the 40 synthetic turf fields tested positive for a universal bacterial gene (16s rRNA) at levels similar to those found on household products. Results from this research (and the follow up exposure characterization which is underway) improves our understanding of the potential for human exposure to chemicals associated with recycled tire crumb rubber material used on synthetic turf fields.