Kreider ML, Hynds ES, Panko JM. Evaluation of tire and road wear particles (TRWP) in air in Delhi, India. Poster at Society of Toxicology Annual Meeting, Baltimore, MD, March 10–14, 2019.
Tire and road wear particles (TRWP) are formed at the frictional interface of the tire and the road surface, and include contributions from both the tire and the pavement. In a previous international sampling campaign to quantify TRWP in environmental media, TRWP were found to be ubiquitously present in ambient air, detectable in both the PM10 (particulate matter less than 10 um) and PM2.5 (particulate matter less than 2.5 um) fractions; although at low concentrations relative to other PM in the air. However, previous sampling was executed in developed countries, where ambient particulate matter con-centrations are well-managed. The purpose of this study was to understand the TRWP concentrations and contributions to ambient particulate matter in a developing country with known challenges associated with ambient air par-ticulate. As a city with one of the highest concentrations of ambient PM, Delhi, India was selected for investigation in this study. Both PM10 and PM2.5 air samples were collected over four consecutive days at six locations through-out Delhi. Total suspended particulate (TSP) samples were also collected at two of the six locations. Study sites were selected to represent a wide variety of human receptors with close proximity to a traffic source; samples were collected within 10 m of the roadside. These air samples were then evaluated for the presence of TRWP using a previously-established pyrolysis gas-chro-matography method, which measures pyrolysis products of the rubber poly-mer to ensure specificity to TRWP. Mean TRWP air concentrations across the six sampling sites were 0.45, 2.1, and 6.2 ug/m3 for PM2.5, PM10, and TSP, espectively. These concentrations represented 0.40%, 0.58%, and 0.50% of total particulate in these respective size ranges, indicating that TRWP is only a minor contributor to ambient particulate matter in Delhi. This finding is con-sistent with sampling in developed countries, where TRWP represented less than 0.3% of total PM2.5 and less than 0.6% of total PM10 on average. That said, the concentration of TRWP in Delhi was higher than found elsewhere; though the underlying reasons for this are unknown, differences in traffic volume, road surfaces, and tires may be potential contributors.