Toxic tire wear compounds (6PPD-Q and 4-ADPA) detected in airborne particulate matter along a highway in Mississippi, USA

Authors: OLUBUSOYE, BOLUWATIFE - University Of Mississippi; CIZDZIEL, JAMES - University Of Mississippi; BEE, MATTHEW - University Of Mississippi; Moore, Matthew; PINEDA, MARCO - McGill University - Canada; YARGEAU, VIVIANE - McGill University - Canada; BENNETT, ERIN - Trent University

Submitted to: Bulletin of Environmental Contamination and Toxicology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2023
Publication Date: 11/9/2023
Citation: Olubusoye, B.S., Cizdziel, J.V., Bee, M., Moore, M.T., Pineda, M., Yargeau, V., Bennett, E.R. 2023. Toxic tire wear compounds (6PPD-Q and 4-ADPA) detected in airborne particulate matter along a highway in Mississippi, USA. Bulletin of Environmental Contamination and Toxicology. 111. Article 68. https://doi.org/10.1007/s00128-023-03820-7.
DOI: https://doi.org/10.1007/s00128-023-03820-7

Interpretive Summary: As automobiles move, microscopic pieces of tires are broken off and carried through the air or left on the ground and transported during a rain event. Air samplers were placed on the edge of a US highway in Mississippi at various distances from the driving lanes to determine concentrations of toxic compounds related to rubber tires. Two toxic compounds were found in samples at concentrations that may pose problems to human health if inhaled or to organisms in a water environment. This study provided a preliminary assessment into the need to examine these emerging compounds to better understand their ecological and human health risk.

Technical Abstract: Tire wear particles (TWPs) are a major category of microplastic pollution produced by friction between tires and road surfaces. This non-exhaust particulate matter (PM) containing leachable toxic compounds is transported through the air and with stormwater runoff, leading to environmental pollution and human health concerns. In the present study, we collected airborne PM at varying distances (5, 15 and 30 m) along US Highway 278 in Oxford, Mississippi, USA for ten consecutive days using Sigma-2 passive samplers. Particles (~1-80 µm) were passively collected directly into small (60 mL) wide-mouth separatory funnels placed inside the samplers. The particles were subsequently subjected to solvent extraction and the extracts were analyzed for TWP compounds by high resolution orbitrap mass spectrometry. This preliminary study was focused solely on qualitative analyses to determine whether TWP compounds were present in this fraction of airborne PM. The abundance of airborne TWPs increased with proximity to the road with deposition rates (TWPs/cm2/day) of 63, 47, and 23 at 5 m, 15 m, and 30 m from the highway, respectively. Two common TWP compounds (6PPD-Q and 4-ADPA) were detected in all samples, except the field blank, at levels above their LODs, estimated at 2.90 ng/L and 1.14 ng/L, respectively. Overall, this work suggests that airborne TWPs may be a potential inhalation hazard along roadways. The bioavailability of TWP compounds from inhaled TWPs is needed to address exposure risk.