I use field measurements coupled with statistical models to examine the impacts of traffic emissions on air quality. Recent focus is on the study of non-exhaust emissions from brakes, tires and road dust, which have physical and chemical properties distinct from traditional exhaust emissions and are expected to dominate traffic-related particulate contributions in the near future as exhaust emissions continue to decrease.
My latest research evaluates the concentrations and emission factors of non-exhaust emissions using chemical speciation data collected near major roadways in Canada. We quantitatively show that these variables are influenced by road type, vehicle fleet composition, and meteorology, providing new insights into the real-world characteristics of these pollutants.
Under review
My previous work integrated roadside monitoring data from criteria air pollutants, volatile organic compounds and particulate organic and elemental carbon measurements to disentangle the source contributions between diesel, gasoline and LPG vehicles, providing evidence in support of different vehicle emissions control policies.
I am interested in understanding how the chemicals in air pollution mixtures translate into health effects. I am also interested in applying less-expensive and flexible monitors to study the variations in composition and sources of air pollution in micro-environments.
We performed a holistic analysis of the toxic air pollutant data collected in Hong Kong, analyzed their source variations over the past two decades, and assessed the associated change in inhalation cancer risks. We found that the major sources of cancer risks have shifted from being diesel emission to industry-related VOCs.
I am interested in using low-cost sensors and other portable instruments to understand air pollution at fine spatial and temporal scales, which ultimately enables improved representation of exposures. My research on the applications of low-cost sensors is a close collaborative effort with the AirSENCE Team of A.U.G. Signals. More publications will come.
Under preparation
We need new analytical capabilities to measure pollutants that we have not been able to detect well yet but are known to have significant implications to the environment and health.
Building upon the latest analytical technique developed by Cao et al. (2025) for simultaneously determining aerosol OCEC and INON, we are currently developing and field-testing an online version of this instrument to enable higher time resolution measurements to better understand carbon and nitrogen chemistry.