Integrated Assessment of Traffic-Related PM2.5 Exposure, Metal Composition, and Health Risk in a Roadside Urban Microenvironment of Jaipur, India

Traffic-related emissions significantly contribute to fine particulate matter (PM2.5) in urban roadside environments, where limited dispersion elevates human exposure and health risks. This study provides an integrated assessment of PM2.5 exposure in a traffic-dominated roadside microenvironment in Jaipur, India, and evaluates seasonal variability, respiratory deposition dose (RDD), elemental composition, source characteristics, and inhalation health risk. Ambient PM2.5 sampling was performed from October to February, and gravimetric and elemental analyses were conducted. RDD was quantified, and non-carcinogenic and carcinogenic risks were estimated using USEPA guidelines. PM2.5 concentrations showed strong seasonal variability, peaking at 97 ± 5.85 µg/m3 during low-temperature winter weekdays, exceeding national and World Health Organization guidelines by 1.6 and 6.5 times, respectively. Winter conditions also led to higher RDD (~80% deposition in the head region) and the enrichment of traffic-related metals, particularly chromium, cadmium, and lead. Backward trajectory analysis indicated dominant local traffic influence with episodic regional transport. Non-carcinogenic risk surpassed unity for children during winters, while carcinogenic risk, primarily driven by chromium, exceeded acceptable thresholds (1 × 10−6), reaching 610 times higher during low-temperature winter weekdays. This first integrated PM2.5 health risk assessment for Jaipur underscores the need of dose- and composition-based assessment in traffic-influenced urban environments.