Emerging investigator series: In-depth chemical profiling of tire and artificial turf crumb rubber: aging, transformation products, and transport pathways

Abstract

Crumb rubber generated from end-of-life tires (ELTs) pose a threat to environmental and human health based on their widespread use. Of particular concern is the use of ELT crumb rubber as infill for artificial turf fields, as people are unknowingly exposed to complex mixtures of chemicals when playing on these fields. Additionally, there is concern regarding transport of rubber-related chemicals from artificial turf into the environment. However, existing knowledge does not fully elucidate the chemical profile, transformation products, and transport pathways of artificial turf crumb rubber across different ages. To address these knowledge gaps, we utilized a multi-faceted approach that consisted of targeted quantitation, chemical profiling, and suspect screening via ultra-high performance liquid chromatography-high-resolution mass spectrometry (UPLC-HRMS). We collected and processed 3 tire and 11 artificial turf crumb rubber samples via solvent extraction, leaching, and a bioaccessibility-based extraction. Nineteen rubber-derived chemicals were quantified using parallel reaction monitoring and isotope dilution techniques. In solvent extracts, the most abundant analytes were 1,3-diphenylguanidine (0.18-1200 µg/g), N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD, 0.16-720 µg/g), 2-mercaptobenzothiazole (0.47-140 µg/g), and benzothiazole (0.84-150 µg/g). Chemical profiling assessed changes in sample diversity, abundance, polarity, and molecular mass. Suspect screening identified 81 compounds with different confidence levels (16 at level 1, 53 with level 2, 7 at level 3, and 5 at level 4). The formation rate of transformation products and clustering analysis results identified time-based trends in artificial turf field samples. We found that the first two years of aging may be critical for the potential environmental impact of artificial turf fields. Our analysis provided insight into the chemical complexity of artificial turf crumb rubber samples ranging from 0-14 years in age.