atmospheric concentrations, seasonal variations, and health risk assessment of pm2.5, pm10, and so2 in tehran metropolis, iran

Background: this study evaluates the seasonal and annual variations of pm₂.₅, pm₁₀, and so₂ concentrations in tehran’s ambient air from 2019 to 2021 and assesses their associated health risks.methods: non-carcinogenic health risks were quantified using the u.s. environmental protection agency (epa) methodology. sobol sensitivity analysis was conducted in r (version 4.1.2), andarcgis (version 10.8.1) was used to map the spatial distribution of pollutants.results: the annual mean concentrations of pm₂.₅, pm₁₀, and so₂ ranged from 28.24–32.34 μg/m³, 69.57–82.22 μg/m³, and 14.94–17.98 μg/m³, respectively, exceeding who air quality guidelines. pm₂.₅ and so₂ levels were highest in the west and southwest, while pm₁₀ was most prevalent in the east and northeast. the hazard quotient (hq) for pm₂.₅ and pm₁₀ exceeded 1 in 8- and 12-hour exposure scenarios, indicating significant health risks. however, the hq for so₂ remained below 1 across all exposure durations, suggesting no immediate health threat. at 3-hour exposures, the hq for pm₂.₅ and pm₁₀ was below 1, underscoring the role of exposure duration in health risks. sobol sensitivity analysis identified pm₂.₅ concentration as the most influential factor affecting health risk.conclusion: the findings highlight the urgent need for regulatory interventions to mitigate pm₂.₅ and pm₁₀ pollution in tehran, particularly in high-exposure regions. effective control measures should prioritize reducing emissions to protect public health.