Personal exposure to fine particulate air pollution while commuting: An examination of six transport modes on an urban arterial roadway

Abstract

Traffic-related air pollution in urban areas contributes significantly to commuters’ daily PM2.5 exposures, but varies widely depending on mode of commuting. To date, studies show conflicting results for PM2.5 exposures based on mode of commuting, and few studies compare multiple modes of transportation simultaneously along a common route, making inter-modal comparisons difficult. In this study, we examined breathing zone PM2.5 exposures for six different modes of commuting (bicycle, walking, driving with windows open and closed, bus, and light-rail train) simultaneously on a single 2.7 km (1.68 mile) arterial urban route in Salt Lake City, Utah (USA) during peak “rush hour” times. Using previously published minute ventilation rates, we estimated the inhaled dose and exposure rate for each mode of commuting. Mean PM2.5 concentrations ranged from 5.20 μg/m3 for driving with windows closed to 15.21 μg/m3 for driving with windows open. The estimated inhaled doses over the 2.7 km route were 6.83 μg for walking, 2.78 μg for cycling, 1.28 μg for light-rail train, 1.24 μg for driving with windows open, 1.23 μg for bus, and 0.32 μg for driving with windows closed. Similarly, the exposure rates were highest for cycling (18.0 μg/hr) and walking (16.8 μg/hr), and lowest for driving with windows closed (3.7 μg/hr). Our findings support previous studies showing that active commuters receive a greater PM2.5 dose and have higher rates of exposure than commuters using automobiles or public transportation. Our findings also support previous studies showing that driving with windows closed is protective against traffic-related PM2.5 exposure.

On-road Air Pollution Exposure to Cyclists in an Agent-Based Simulation Framework

“…The inhaled dose per trip for cyclists is about 2 times higher than inhaled dose per trip for car drivers/passengers and about 4 times higher than motorbike riders. Higher inhaled dose for cyclists is also found in previous studies (Chaney et al, 2017;O'Donoghue et al, 2007). Even though the average trip times of cyclists and motorbike drivers are in similar range (14.7 min and 17.4 min for cyclists and motorbike drivers respectively), the exposure per trip for cyclists is higher because of higher breathing rate of cyclists.…”

“…In the latter, the inhaled mass per trip is very low (see Table 2) while comparing to the values in literature (O'Donoghue et al, 2007;Chaney et al, 2017). For instance, the estimated inhaled dose of PM 2.5 for a cyclist is about 2.78 µg only for a trip of about 2.7 km in Salt Lake City, Utah (USA) (Chaney et al, 2017). Including background air quality in the estimation of exposure, the inhaled mass per trip increases significantly.…”

Effect of mode shift from car to light rail on personal exposure: A controlled experiment

“…However, when taking into account fleet characteristics such as ventilation, in-LRT BC exposure was higher than in-vehicle BC exposure when the vehicle was operating under closed ventilation condition (2.69 µg/m 3 vs. 1.61 µg/m 3 ). Except for a few recent studies (Chaney et al, 2017;Ham et al, 2017), most previous studies looking at the modal differences in pollutant exposure rarely control for a ventilation condition or make certain assumptions about ventilation condition. For example, Wang and Gao (2011) did not explicitly control for ventilation conditions when measuring PM2.5 and fine particle concentrations for different travel modes, yielding unusually lower PM2.5 mass concentrations (400% to 1,400% lower) for automobile compared to all other modes.…”

“…Differences caused by a specific mode can be trumped by other factors, such as ventilation and traffic microenvironments. Especially, ventilation setting of a vehicle could be a deciding factor because personal exposure is largely influenced by how much outside pollutants penetrate into the vehicle (Chaney et al, 2017;Ham et al, 2017;Quiros et al, 2013).…”

“…Notably, few empirical studies have systemically examined the effects of mode shift from car to rail transit on air pollution exposure. One study from Salt Lake, Utah conducted simultaneous measurements of PM2.5 while taking into account different driving conditions with closed/open windows (Chaney et al, 2017). A recent study from Sacramento, California has conducted a large-scale multi modal exposure assessment and found ventilation settings to have a significant effect on personal exposure (Ham et al, 2017).…”