Improve air quality in public transportation | Science

Millions of people depend on urban public transportation systems (1), which are critical to sustainable urban living. However, in public transportation vehicles and hubs worldwide, air quality remains unregulated (2), and air pollutant levels surpass those in the outdoor ambient air (3–7), threatening the health of commuters and transit workers. Improving air quality in these settings is critical to safeguarding population health in increasingly urbanized societies.