Traffic-related PM_2.5 exposure and its cardiovascular effects among healthy commuters in Taipei, Taiwan

The association between traffic-related air pollution (TRAP) exposure and cardiovascular effects has been reported in previous epidemiological studies. However, the effects of different commuting modes on TRAP exposure and TRAP-induced cardiovascular effects in healthy adults during commuting are not well known. We recruited 120 healthy adults in Taipei, Taiwan. Each participant was classified by his/her own commuting style, including electrically powered subway, gasoline-powered bus, gasoline-powered car, gasoline-powered scooter, walking, and walking wearing a facemask. Six repeated measurements of systolic blood pressure (SBP), diastolic BP (DBP), heart rate (HR), urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG), particulate matter with an aerodynamic diameter ≤ 2.5 μm (PM_2.5), temperature, humidity and noise level were conducted for each participant between 09:00 am and 10:00 am in six different commuting modes. Mixed-effects models were used to investigate the association between PM_2.5 and cardiovascular effects. The results showed that personal exposure to PM_2.5 was associated with increased SBP (W: 6.5%; Sc: 7.9%), HR (W: 3.4%; Sc: 6.4%) and urinary 8-OHdG (W: 8.1%; Sc: 8.9%) in the walking (W) mode and scooter (Sc) mode. The PM_2.5 level (Mean ± SD) was the highest in the scooter mode (53.6 ± 26.1 μg/m³) but the lowest in the subway mode (21.7 ± 5.8 μg/m³). The effects of PM_2.5 on cardiovascular endpoints were not statistically significant in the subway mode. Additionally, no significant association was noted among PM_2.5, BP and HR in the walking wearing a facemask mode. We concluded that traffic-related PM_2.5 was associated with cardiovascular effects. We encourage commuters to commute using public rapid transit systems instead of riding scooters/motorcycles during rush hours.