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.