Impacts of Subway System Modifications on Air Quality in Subway Platforms and Trains

Abstract

Subway PM2.5 can be substantially sourced from the operation of the system itself. Improvements in subway air quality may be possible by examining the potential to reduce these emissions. To this end, PM2.5 was measured on the trains and station platforms of the Toronto subway system. A comparison with previously published data for this system reveals significant changes in below ground platform PM2.5. A reduction of nearly one-third (ratio (95% CI): 0.69 (0.63, 0.75)) in PM2.5 from 2011 to 2018 appears to have resulted from a complete modernization of the rolling stock on one subway line. In contrast, below ground platform PM2.5 for another line increased by a factor of 1.48 (95% CI; 1.42, 1.56). This increase may be related to an increase in emergency brake applications, the resolution of which coincided with a large decrease in PM2.5 concentrations on that line. Finally, platform PM2.5 in two newly opened stations attained, within one year of operation, typical concentrations of the neighboring platforms installed in 1963. Combined, these findings suggest that the production of platform PM2.5 is localized and hence largely freshly emitted. Further, PM2.5 changed across this subway system due to changes in its operation and rolling stock. Thus, similar interventions applied intentionally may prove to be equally effective in reducing PM2.5. Moreover, establishing a network of platform PM2.5 monitors is recommended to monitor ongoing improvements and identify impacts of future system changes on subway air quality. This would result in a better understanding of the relationship between the operations and air quality of subways.

In-train particulate matter (PM10 and PM2.5) concentrations: Level, source, composition, mitigation measures and health risk effect – A systematic literature review

“…The instrument was either placed at the passenger's breathing level or carried in a backpack by the researcher. 8,9,24,[27][28][29][30][31][32][33][34][35]39,[41][42][43]47,57,58,65,67,69,70,76,78,79,81,82,[85][86][87]90 The real-time mass concentration of PMs was determined by DustTrak using light scattering technology and can detect PM 2.5 and PM 10 mass concentrations. On the other hand, the Dustmate fume and dust detector was another standard instrument observed in the selected articles for this review.…”

“…The USA produced a more significant portion of five studies, [81][82][83][84][85] and another conducted in multiple northeastern United States cities. 7 Canada, 86 Chile 87 and Mexico 88 produced one article each, which reported measurements of in-train concentration in each scenario. Two publication was conducted in Australia in the Oceania continent 89,90 and no publication was found from Africa, South America and fewer in Southeast Asia.…”

“…Source originating people's activities in train Smoking 78 Cooking 30 Passenger density 27,28,31,43,64 Presence and movement of passengers 38,40,62,106 Resuspended materials from passengers and luggage from the carriage floor 28,31,40,64,78 Sources originating from trains operation Doors and windows opening 29,37,61,65,73,74,79 Train arrival/departure 37 Air conditioning/ ventilation system 26,28,43,56,69,75 Inorganic metallic source from subway station internal facilities 52 Air exchange between train and tunnel 65,74 Sources originating from the mechanical movement of train parts Steel abrasion/wear of parts 58,97 Friction between railway lines and the rail wheels 9,52,58,62,86…”

Sixteen-Year Monitoring of Particulate Matter Exposure in the Parisian Subway: Data Inventory and Compilation in a Database

“…These data suggest that the PM present in the subway has, for the most part, an internal origin. Since all these concentrations massively exceed the recently updated WHO AQGs (i.e., 5 µg/m 3 for PM 2.5 and 15 µg/m 3 for PM 10 ), monitoring and recording of this exposure for epidemiological study purposes is important This database will also be used to carry out further analysis on PM concentrations in relation to a variety of potential determinants, similar to what was conducted on the effects of changing parameters in the subway system (e.g., the rolling stock) on PM 2.5 concentrations recorded between 2011 and 2018, in the subway of Toronto [58]. Several parameters have been identified in the literature as potential determinants of PM exposure.…”

A Real-Time Comparison of Four Particulate Matter Size Fractions in the Personal Breathing Zone of Paris Subway Workers: A Six-Week Prospective Study

“…Because of this size distribution and a highly ferruginous composition, along with the presence of trace metals (Mg, Al, Si, Ti, V, Cr, Mn, Ni, Cu, Zn, Ba, and Pb) [ 23 , 24 ], subway PM generates more reactive oxygen species (ROS) and oxidative-stress-related outcomes compared to other PM [ 18 , 25 ]. A comprehensive assessment of individual exposure to subway PM, particularly the finest size fractions, is urgently warranted in order to identify the sources and factors that contribute to high PM levels in individual subway stations and lines [ 26 , 27 ]. While the potential health impacts of subway PM on workers and/or commuters remain uncertain, exposure assessment studies are essential for risk assessments and exposure control interventions.…”