Identification of High Personal PM_2.5 Exposure during Real Time Commuting in the Taipei Metropolitan Area

There has been an increase in the network of mass rapid transit (MRT) and the number of automobiles over the past decades in the Taipei metropolitan area, Taiwan. The effects of these changes on PM2.5 exposure for the residents using different modes of transportation are unclear. Volunteers measured PM2.5 concentrations while commuting in different modes of transportation using a portable PM2.5 detector. Exposure to PM2.5 (median (range)) was higher when walking along the streets (40 (10-275) mu g/m(3)) compared to riding the buses (35 (13-65) mu g/m(3)) and the cars (15 (8-80) mu g/m(3)). PM2.5 concentrations were higher in underground MRT stations (80 (30-210) mu g/m(3)) and inside MRT cars running in underground sections (80 (55-185) mu g/m(3)) than those in elevated MRT stations (33 (15-35) mu g/m(3)) and inside MRT cars running in elevated sections (28 (13-68) mu g/m(3)) (p < 0.0001). Riding motorcycle also was associated with high PM2.5 exposure (75 (60-105 mu g/m(3)), p < 0.0001 vs. walking). High PM2.5 concentrations were noted near the temples (588 +/- 271 mu g/m(3)) and in the underground food court of a night market (405 +/- 238 mu g/m(3)) where the eatery stalls stir-fried and grilled food (p < 0.0001 vs. walking). We conclude that residents in the Taipei metropolitan area may still be exposed to high PM2.5 during some forms of commuting, including riding underground MRT.