The effect of route selection on PM2.5, particle number count and lung deposited surface area concentrations during bicycle commuting

Abstract

TPS 651: Air pollution exposure modeling 1, Exhibition Hall, Ground floor, August 27, 2019, 3:00 PM - 4:30 PM Aim: The aim was to evaluate the difference in fine particle (PM2.5; particles <2.5 µm in diameter), particle number count (PNC) and lung-deposited surface area (LDSA) concentrations during cycling between more and less road traffic-impacted routes to find out whether cyclists can influence their exposure to particulate air pollutants with route selection. Methods: Measurements were conducted in the Helsinki metropolitan region, Finland, in October/November 2016, March/April 2017 and June 2017, representing autumn, spring and summer. Measurements were done simultaneously on two bicycling routes, which had the same starting and end points and starting time. One route followed busy streets in traffic environments (‘Traffic’) and another utilized side-streets and parks (‘Green’). Seven bicycling route pairs were selected for air pollution measurements conducted during and outside rush hours on weekdays. The cyclist carried portable measurement devices in a backpack. Every route was biked back and forth at least two times both in the mornings and in the afternoons in each season. For each trip, the median of measured concentrations was calculated to represent a typical exposure level during a one-way trip. The Wilcoxon Signed-Rank test was used to compare the concentration ratios of studied air pollutants between Traffic and Green routes. Results: A total of 173, 145, and 145, pairs of one-way trips were included in the analysis for PM2.5, PNC, and LDSA, respectively. Length of Traffic and Green routes ranged between 3.9-5.5 km and 4.7-6.7 km, respectively. Cyclist was exposed on average 1.3-times higher median PM2.5 and LDSA concentrations on Traffic route compared to Green route, and 1.4-times higher PNC concentration. The differences between levels in studied route pairs were greater during rush hours. Conclusion: Cyclists can influence their exposure to air pollution with route selection. Thus, alternative routes further away from busy road traffic should be planned in urban areas.