Comparisons of personal exposure to PM2.5 and CO by different commuting modes in Beijing, China.

BACKGROUND: Epidemiological studies have shown that commuting in traffic is associated with adverse health effects. It is vital to investigate commuters' exposure to traffic-related air pollutants before considering potential health risks. However, there are relatively few publications considering commuters' personal exposure in China.
METHOD: We carried out a field investigation measuring commuters' personal exposure to particulate matter ≤2.5 μm in aerodynamic diameter (PM(2.5)) and carbon monoxide (CO) by three commuting modes in Beijing. Both PM(2.5) and CO personal concentrations and whole trip exposures were compared among the three commuting modes.
RESULTS: After controlling confounding factors, we found that taxi commuters were exposed to lower concentrations of PM(2.5) (31.64±20.77 μg/m(3)) compared with bus commuters (42.40±23.36 μg/m(3)) and cyclists (49.10±26.60 μg/m(3)). By contrast, CO personal concentrations were significantly higher when commuting by taxi (5.21±1.52 ppm) than by bus (2.41±0.99 ppm) and bicycle (1.90±0.55 ppm). However, when inhalation rates and trip duration were taken into consideration, cyclists experienced the highest whole trip exposures to both PM(2.5) and CO (p<0.05). We also found fixed site monitoring data were not appropriate surrogates for personal exposure while commuting, especially during traffic heavy times.
CONCLUSION: PM(2.5) and CO personal concentrations were greatly influenced by the commuting mode. Furthermore, the highest whole trip exposures to PM(2.5) and CO which cyclists experienced indicates it is not preferable to commute by bicycle in a relatively high air polluted environment. Cyclists are possibly subject to greater health risks than other commuters. Thus further research needs to be conducted to investigate the health risks associated with cycling.