Metro Commuter Exposures to Particulate Air Pollution and PM_2.5-Associated Elements in Three Canadian Cities: The Urban Transportation Exposure Study

Abstract

System-representative commuter air pollution exposure data were collected for the metro systems of Toronto, Montreal, and Vancouver, Canada. Pollutants measured included PM (PM = particulate matter), PM, ultrafine particles, black carbon, and the elemental composition of PM. Sampling over three weeks was conducted in summer and winter for each city and covered each system on a daily basis. Mixed-effect linear regression models were used to identify system features related to particulate exposures. Ambient levels of PM and its elemental components were compared to those of the metro in each city. A microenvironmental exposure model was used to estimate the contribution of a 70 min metro commute to daily mean exposure to PM elemental and mass concentrations. Time spent in the metro was estimated to contribute the majority of daily exposure to several metallic elements of PM and 21.2%, 11.3% and 11.5% of daily PM exposure in Toronto, Montreal, and Vancouver, respectively. Findings suggest that particle air pollutant levels in Canadian metros are substantially impacted by the systems themselves, are highly enriched in steel-based elements, and can contribute a large portion of PM and its elemental components to a metro commuter's daily exposure.

Personal exposures to traffic-related air pollution in three Canadian bus transit systems: the Urban Transportation Exposure Study

“…The UTES was designed to assess TRAP exposures in Canadian subway [18], private vehicle [19], and bus commuting environments. The predominant use of diesel propulsion in buses may result in higher exposure to diesel exhaust in buses, relative to private vehicles and subways.…”

“…Personal exposures to TRAP in commuting environments is a research priority. While commuting represents 5% of a Canadian's day [15], this microenvironment can represent a larger proportion of daily exposure to trafficrelated air pollutants [16][17][18]. The characterization of air pollution in urban transport environments can help refine air pollution exposure estimates as well as inform air quality policy.…”

“…The Urban Transportation Exposure Study (UTES) was designed to assess TRAP exposures in Canadian commuting environments. Results from the subway/metro [18], and private vehicle [19] components of UTES are published elsewhere. This paper presents an air pollution exposure assessment for the public bus transit systems of Toronto, Ottawa, and Vancouver, Canada.…”

Particulate matter and the airway epithelium: the special case of the underground?

“…Studies evaluating the composition of underground PM compared to PM found in overground light rail and road journeys suggest that, while underground PM may have relatively low concentrations of the carcinogenic polyaromatic hydrocarbons associated with diesel combustion, this may be outweighed by the presence of metals in underground PM, and the sheer airborne concentration of underground PM [14,92]. Indeed, even a relatively short commute in an underground railway may contribute a large proportion of an individual's daily exposure to PM and airborne metals [16]. Therefore, it is perhaps surprising that studies of the effects of acute and chronic exposure to underground railway air have found little evidence of excess risk [93].…”

Effect of modes of transportation on commuters' exposure to fine particulate matter (PM2.5) and nitrogen dioxide (NO2) in Chennai, India

“…Studies carried out in Canada and Barcelona showed that, elemental concentration differs with respect to mode of transport and time of exposure i.e. travel time on which the commuters use the roads [3,36].…”