Near-road measurement of traffic-related pollutants

Photo Source: Wikipedia user Aliamizi

Photo Source: Wikipedia user Aliamizi

Traffic related pollutants were officially classified as carcinogenic by the World Health Organization in 2013. For the many Canadians that live or work near roadways, this could be a risk factor which may negatively impact their health.

Dr. Cheol-Heon Jeong and Jon Wang, both of UofT’s Department of Chemical Engineering and Applied Chemistry, say the concentration of traffic-related pollutants varies with distance from the road; where significant pollution can be detected up to 250 metres from the road.

There are over 10 million Canadians living 250 metres from the road and nearly another 2 million living within 50 m of major roads, which are areas with high concentrations of traffic-related pollutants.

At the latest SOCAAR seminar, Jeong and Wang discussed the exposure of Canadians to traffic related pollution based on findings from three different field campaigns they had conducted.

Air quality samples taken from College Street in downtown Toronto from one of the longest studies on the number and size distributions of ultrafine particles, showed pollution trends linked to weekday and weekend traffic patterns. Ultrafine particles and black carbon peaked during the morning rush hour on weekdays. Similar peaks were seen in traffic-related trace metals like calcium, manganese, iron, and barium during the morning rush hour. These increases roughly corresponded to the increase in traffic during the weekday over the weekend.

Jeong and Wang also linked some emission factors to different vehicle sources. Specifically, cars showed higher levels of carbon monoxide (CO) and aromatic volatile organic carbon (VOC); while trucks show higher levels of nitrogen dioxide (NOx), black carbon, and ultrafine particles.

The other two field studies looked at the size distribution of particles as a distance from the roadway. The particle size is very important because the deposition rate of particles in the lung increases as the size of the particles decreases. Jeong and Wang concluded that people living, working, or travelling within 20 metres from major roads could be exposed to significant amounts of traffic related volatile ultrafine particles below 20 nanometres.

The next investigation for Jeong and Wang will be on the seasonal comparison (warm versus cold temperatures) and spatial differences for traffic-related pollutants between downtown and urban sites.