Linking ambient air pollution to health risk burden: A comparative study across urban and semi-urban regions of Karnataka, India

Abstract

Introduction: Ambient air pollution poses significant public health challenges across urban and semi-urban India. Karnataka, encompassing coastal, plateau, highland, and semi-arid environments, provides an ideal setting for evaluating regional air quality variability and associated health risks. This study assessed the spatio-temporal characteristics of ten criteria and hazardous air pollutants measured at five Central Pollution Control Board (CPCB) Continuous Ambient Air Quality Monitoring Stations (CAAQMS) across Karnataka during 2024.

Materials and methods: Monthly mean concentrations of Particulate Matters (PM₂.₅, PM₁₀), Nitrogen dioxide (NO₂), Sulfur dioxide (SO₂), Carbon monoxide (CO), Ozone (O₃), Ammonia (NH3), and benzene were analysed across four India Meteorological Department (IMD) seasons. Serial autocorrelation was assessed using the lag-1 Kendall statistic prior to applying the Mann–Kendall test and Sen's slope estimator as an exploratory assessment of intra-annual monotonic tendencies. Spatial variability was evaluated using one-way ANOVA with Tukey's HSD post-hoc test and validated using the Kruskal–Wallis test. Inhalation health risks were assessed using the USEPA Risk Assessment Guidance for Superfund (RAGS) methodology by estimating Hazard Quotient (HQ), Hazard Index (HI), and Lifetime Cancer Risk (LCR).

Results: Bengaluru recorded the highest annual mean PM₂.₅ (40.2 μg/ m³) and PM₁₀ (80.4 μg/m³) concentrations, with PM₂.₅ equal to the CPCB National Ambient Air Quality Standard (NAAQS) and PM₁₀ exceeding it by approximately 34%. Annual mean PM₂.₅ concentrations at all stations exceeded the WHO 2021 Air Quality Guideline (15 μg/m³). The southwest monsoon produced the greatest reduction in particulate concentrations. Exploratory Mann–Kendall analysis yielded negative Sen's slopes for PM₂.₅ at all stations, although none were statistically significant (p>0.05). One-way ANOVA confirmed significant spatial heterogeneity among monitoring stations (p < 0.001). Screening-level health risk assessment indicated HI values >1.0 at all stations (1.756–3.290). Estimated PM₂.₅ LCR ranged from 1.76 × 10⁻³ to 3.34 × 10⁻³ and represents hypothetical upper-bound screening estimates rather than regulatory cancer risk values.

Conclusion: Particulate matter remains the dominant air quality concern across Karnataka, particularly in Bengaluru. Strengthened emission control measures, continued multi-year monitoring, and agricultural ammonia management are recommended to support long-term improvements in air quality and public health.