LAUSR

Objective: To find the differences in PM(2.5) exposure level in the context of four commuting modes (by walk, bicycle, bus and subway) in Guangzhou. Methods: The PM(2.5) exposure assessment was carried out from January to December 2015 in Guangzhou. PM(2.5) was measured by using SidePak individual dust meter (AM510, TSI Inc. USA) with time interval of 1 minute. Our measurement was taken on Monday, Wednesday, Friday and Sunday in the second week of each month and the samples were collected in the morning (07:00-09:00), afternoon (11:00-13:00) and evening (17:00-19:00). Results: A total of 284 air samples during walking, 281 air samples during bicycle riding, 278 air samples in bus, and 280 air samples in subway were collected. The median PM(2.5) concentrations exposed during walking, during bicycle riding, in bus and in subway were 38.4, 38.6, 23.3 and 24.1 μg/m(3), respectively, which were positive correlated with exposure concentration in fixed surveillance sites. The exposure level was lowest in summer, and highest in winter. The median of one-way exposure level to PM(2.5) from high to low were as follows: 21.0 μg for bicycle riding, 20.1 μg for walking, 5.1 μg for taking bus and 2.6 μg for taking subway. The season and time specific one-way exposure levels to PM(2.5) of four commuting modes were consistent. Conclusions: The exposure level to PM(2.5) was obviously higher during walking and bicycle riding than that in bus and subway. The exposure level to PM(2.5) during walking was higher than that during bicycle riding, in bus and in subway.