Intermodal comparison of commuters' exposure to VOCs between public, private, and active transportation.

Urban populations are exposed to a multitude of traffic-related air pollutants during daily commutes. This study assessed commuters' exposure to volatile organic compounds (VOCs) during bus, motorcycle, and bicycle commuting, and estimated the VOC inhalation dose. Benzene, toluene, ethylbenzene, and xylene (BTEX) were the main compounds detected, contributing 58 - 68% to ΣVOC (sum of the concentrations of all detected VOCs) in different travel modes. The mean ΣVOC exposure concentration was higher for motorcyclists than for cyclists and bus commuters. However, due to cyclists' higher minute ventilation rates and longer exposure time, they had the highest ΣVOC inhalation dose based on both travel time (7.09 ± 2.36 μg min-1) and distance (32.9 ± 10.8 μg km-1). Among the three travel modes, bus commuters had the lowest ΣVOC inhalation dose based on travel time (2.33 ± 1.18 μg min-1) and distance (8.91 ± 4.91 μg km-1), while motorcyclists had a moderate ΣVOC inhalation dose based on travel time (5.08 ± 1.46 μg min-1) and distance (13.4 ± 5.5 μg km-1). Health impact assessment of VOCs showed that cyclists faced the highest carcinogenic and non-carcinogenic risks, while bus commuters experienced the lowest health risk associated with VOC exposure. Our findings underscore the need to consider air quality in transportation infrastructure design and prioritize interventions to safeguard urban commuters' health, particularly cyclists, who are the most vulnerable to the adverse effects of traffic-related air pollutants.