Improved characterization of the real-world contributions and impacts of non-tailpipe particulate matter emissions

This study will measure concentrations of non-tailpipe particulate matter across Toronto, Canada to determine how much non-tailpipe pollution people might breathe in everyday life and how to better measure these exposures in the future.

Poster abstract for HEI Annual Conference 2023

Improved Characterization of the Real-World Contributions and Impacts of Non-tailpipe Particulate Matter Emissions

Greg Evans¹, Matthew Adams¹, Jeffrey Brook¹, Arthur Chan¹, Meredith Franklin¹, Marianne Hatzopoulou¹, Kristin Iorio¹, Cheol-Heon Jeong¹, Maria-Teresa Pay-Perez¹, Sophie Roussy¹, Nicole Trieu¹, Xing Wang¹, Scott Weichenthal², Yee-Ka Wong¹

¹University of Toronto, Toronto, Ontario, Canada

 ²McGill University, Montreal, Quebec, Canada

Background. Emissions of non-tailpipe (NTP) particulate matter (PM) from vehicles are increasing. We have initiated a three-year HEI-funded project, to help build knowledge needed to elucidate potential health impacts associated with resulting exposure.

Objectives. This project has four complementary objectives: (1) characterize hourly and long-term patterns of NTP PM and emission factors; (2) disentangle spatial patterns of NTP PM using complementary approaches; (3) evaluate and improve lab-based methods to differentiate between tailpipe (TP) and NTP PM; and (4) identify, evaluate, and differentiate NTP and TP variations in microenvironments to guide future health studies.

Experimental Design. We will address our objectives through four integrated sub-studies:

1) We will apply two-step positive matrix factorization (PMF) to hourly measurements of fine (PM_2.5) composition at fixed near-road monitoring stations in two Canadian cities, including metal and organic markers of brakes, tires, and resuspended road dust, to characterize and apportion the contributions of TP and NTP emissions. Separate analyses of PM_2.5 and PM₁₀ metals will be conducted at one site to resolve particle-size-related differences in NTP source contributions. We will also apply PMF modelling to five years of 24h integrated filter data, to estimate long-term trends in NTP sources.

2) Saturation (e.g. weekly filters), mobile sampling, and air sensor measurements across Toronto will be used to characterize and contrast the spatial patterns of NTP and TP PM. A combination of physical and chemical characterization methods will be used to distinguish TP vs NTP and constrain the relative contributions of various NTP sources (e.g. brakes, tires, and road dust).

3) Lab-based studies will explore mass spectrometry- and metals-based methodologies to identify chemical source profiles and marker compounds for NTP PM. We will also measure the oxidative potential (OP) of PM from known NTP sources and field samples to identify source-related differences in PM OP.

4) Samples collected at potential hotspots and background locations across Toronto will be used to infer and contrast the mix and contributions of NTP sources. The PM OP at these locations will also be evaluated to guide exposure assessment for future health studies.

Significance. This project should yield new methods to differentiate and estimate NTP PM exposure across populations and new insight into how the contribution of NTP emissions to PM has changed over time in contrasting cities. We also hope to improve knowledge of real-world factors that influence near-road concentrations of NTP PM in addition to knowledge of the relative OP of NTP sources compared to TP sources. Finally, we hope to identify microenvironments that could be used in future studies of acute or chronic health impacts of NTP PM exposure.