Real-time record of particulate matter along traffic roads and health risk assessment.

Air pollution from road traffic is a major environmental and public health concern in European cities. Many municipalities have introduced Clean Transport Zones (CTZs) to restrict high-emission vehicles and improve air quality. This study evaluated whether the planned CTZ in Warsaw, Poland, could reduce particulate matter (PM) concentrations and the associated respiratory exposure. A mobile monitoring system equipped with an optical particle analyzer measured real-time concentrations of four PM fractions along traffic routes, while the multiple-path particle deposition model was applied to assess age-dependent inhalation and deposition in the human respiratory tract. Average PM2.5 and PM10 concentrations did not differ significantly between the CTZ and the surrounding access routes. The highest concentrations occurred near major intersections, traffic lights, pedestrian crossings, and congestion zones, where PM2.5 and PM10 levels increased by up to an order of magnitude compared to uninterrupted traffic flow. Traffic disruptions, rather than CTZ location, are the primary drivers of short-term PM exposure. PM10-PM2.5 contributed approximately three times more to peak PM10 concentrations than under traffic-background conditions. Respiratory exposure analysis revealed significant age-related differences. Inhaled doses of PM1 decreased with age, deposition of PM10 in tracheobronchial and pulmonary regions was substantially higher in young children. PM10 mass deposition per area in 3-year-old children (0.78 μg m⁻