The inhaled dose of pollution while bike commuting: Interactions between route pollutant concentrations and exertional intensity

• Particulate matter (PM) concentrations varied greatly by area and season in Brescia, Italy. • Higher levels of PM were found during the Fall/Winter seasons compared to the Spring/Summer seasons. • Due to this variability, high ID levels can be achieved even with low levels of exertional intensity. • To assess PM exposure, both air quality and physiological data must be taken into account. Bike commuters are amongst the road user groups most exposed to air pollutants. In this context, particulate matter (PM) has been shown to vary greatly within urban settings. However, despite recent advancements in high-resolution portable devices, how this variability interacts with active commuting-related exertional intensity in determining the actual inhaled dose (ID) of PM has remained under-investigated. This study evaluated the variability of the ID within the city of Brescia (Italy) by modelling actual recordings of PM concentrations in different areas of the city with actual laboratory-derived ventilatory rates at two cycling intensities. PM was recorded across six different city areas between seasons (i.e., cold and hot), while ventilatory rates were measured from 47 young healthy participants (21 females) during moderate- and heavy-intensity cycling. PM concentrations varied considerably between areas (∼30–55 %; P < 0.001) and were higher (∼35 %; P < 0.001) during the cold season. Due to these variations, in some areas the computed ID for moderate-related ventilation levels was similar to the ID computed for heavy-related ventilation levels for other areas of the city with a lower concentration of PM. In a sub-analysis, our data also demonstrate that the ID for the same relative heavy-intensity exercise was greater in males [1.47 (1.18––1.90) µg/min] compared to females [1.05 (0.82–––1.36) µg/min; P < 0.001, r = 0.24]. Within the same municipality, the concentration PM varies considerably, such that a high level of ID can be achieved even with low levels of exertional intensity. Our data indicate that PM concentrations, exertional intensity, and the sex of the individuals must be considered when quantifying individual exposure to PM. Collectively, this evidence could be used to inform the planning of bike routes and to enhance awareness of bike commuters regarding the role of exertional intensity in determining their ID.