Chemical and Physical Characterization of Tire Crumb Rubber Used in Synthetic Turf Fields to Improve Exposure Assessment

Abstract

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 and Playgrounds, researchers collected tire crumb rubber samples from nine tire recycling plants and infill from 25 outdoor and 15 indoor synthetic turf fields across the U.S. Fields were recruited from all four U.S. census regions, and ranged in age from new installations to 12 years old. Multiple analytical methods were applied to measure a wide range of metals, VOCs, and SVOCs. Particle sizes were characterized using gravimetric and SEM methods. Microwave acid digestion of tire crumb rubber with ICP-MS analysis was used to measure 20 elements. Tire crumb rubber was solvent extracted for analysis of approximately 50 PAHs, phthalates, thiazoles, and other rubber chemicals by GC/MS/MS and LC/TOFMS methods. Dynamic emission chamber testing was performed for VOCs and SVOCs at 25° and 60°C. Suspect screening and non-targeted analysis approaches were applied to assess the larger range of VOCs and SVOCs that may be associated with the material. Bioaccessibility of metals from tire crumb rubber was measured using simulated saliva, sweat, and gastric fluids. The range and variability in chemical substances measured within and between recycling plants and synthetic turf fields was examined. Differences in measurements among indoor and outdoor fields and fields with different age and region characteristics were assessed. This presentation will focus on key results from the application of this array of analytical methods, with a goal of improving our understanding and knowledge for assessing synthetic field user exposures.