Modelled Physical Activity Benefits and PM_2.5 Risks in Two Urban Cyclists

The analysis evaluated the modelled balance between physical-activity benefits and PM_2.5 -related mortality risks using previously published monitoring data from 162 repeated cycling trips by two commuters in Gliwice, Poland. Each trip defined a hypothetical long-term pattern repeated five days per week, compared with resting for the same duration at the concurrent stationary reference concentration. Observed concentrations and durations were combined with assumed ventilation and published dose-response functions. The analysis propagated epidemiological coefficient uncertainty and alternative ventilation assumptions into net relative risk (RR_NET) and examined illustrative sensor sensitivity and trip-specific break-even concentrations. Under central fixed-ventilation assumptions, median RR_NET was 0.840, corresponding to a modelled 16.0% relative risk reduction. The simulated dataset median was 0.839 (95% uncertainty interval 0.792-0.892) when epidemiological coefficients varied. Alternative ventilation scenarios also yielded favourable conditional balances. Personal-concentration changes of ±10% altered the sign of the dose-equivalent increment for 12 trips without producing central RR_NET ≥ 1. The median modelled break-even concentration was 196.7 µg/m³ with other assumptions fixed. These estimates are not observed health effects, population effects or universal pollution thresholds. Uncalibrated optical measurements and the two-person sample constrain interpretation; larger studies with sensor validation and measured ventilation are needed.