Urban city of tomorrow: Bicycle based measurements of particulate matter exposure before and after road closure to motorized traffic

Particulate matter pollution poses a growing health risk, especially during physical activity and active commuting in traffic-heavy urban areas. This study compared the concentration of particulate matter on the same urban road either open or closed to motorized traffic. Particulate matter (PM 1 , PM 2.5 , PM 10 ) was assessed using a bicycle-mounted Mini Laser Aerosol Spectrometer. Data were collected on a 900-m inner-city street in Frankfurt am Main, Germany, on 20 days (10 days with and 10 days without motorized traffic). Meteorological data and local urban background concentrations of PM 2.5 and PM 10 were taken from three nearby located air quality monitoring stations. The impact of motorized traffic and environmental cofactors on particulate matter exposure (absolute values for PM 1 , normalised to local urban background concentrations for PM 2.5 and PM 10 ) were analysed using linear mixed models. When the cycled road was closed for motorized traffic, mean and standard deviation values of 6.9 ± 4.8 μg/m 3 PM 1 , 9.8 ± 5.3 μg/m 3 PM 2.5 , and 19.2 ± 10.1 μg/m 3 PM 10 occurred. Compared to the car-free condition, the presence of motorized traffic was associated with significantly higher particulate matter concentrations, with an average increase of 3.2 μg/m 3 (95 % CI: 3.0, 3.5) for PM 1 , 1.3 μg/m 3 (95 % CI: 0.9, 1.7) for PM 2.5 and 3.4 μg/m 3 (95 % CI: 2.4, 4.4) for PM 10 . As an additional finding, higher air pressure, humidity and temperature as well as lower wind speeds were linked to increased particulate matter concentrations. Concepts like open streets or car-free days which include temporary or permanent road closures to motorized traffic have health-promoting potential by drastically reducing the local particulate matter exposures for pedestrians and cyclists. • Road closures to motorized traffic significantly reduced particulate matter concentrations of PM1, PM2.5 and PM10. • Mobile bicycle-based measurements revealed peak exposure levels up to three times higher under traffic conditions. • Meteorological factors like air pressure, temperature, humidity, and wind speed influenced particulate levels. • Traffic-free interventions are a cost-effective way to reduce PM exposure and promote health-focusedurban planning.