A framework for residential BTEX management: GIS mapping, source diagnostics, OFP scaling, and health risk

This work developed and utilized an integrated engineering framework to estimate the seasonal dynamics, source contributions, photochemical reactivity, and health risk of BTEX (benzene, toluene, ethylbenzene and xylene) in residential microenvironments of Delhi throughout 2019–2021. ∑BTEX showed seasonal variability, with elevated concentrations during winter (≈36 µg m⁻³ across study years) due to low boundary-layer height and atmospheric stagnation; on the contrary, summer levels were drastically declined and particularly so in 2020 (19.38 µg m⁻³) under COVID-19 mobility restrictions. Spatial variability was interpolated within ArcGIS by use of Inverse Distance Weighting to create exposure surfaces. Multiple regression analysis determined environmental predictors and Principal Component Analysis (PCA) extracted 3 major sources of emissions elucidating 80.8% of total variance (PC1: 37.8%, PC2: 29.9%, PC3: 13.1%), related to regional traffic-solvent emissions, and local fuel/traffic level hotspots and neighborhood-level combustion/micro-industrial sources respectively. Reactivity-weighted ozone formation potentials (OFP) calculated with Maximum Incremental Reactivity coefficients indicated that photochemical loadings were toluene-dominant (>89% contribution), and benzene contributed little to the oxidizing capacity despite some episodic concentration increases. The quantitative risk assessment model with the exposure route of EC, EDI, HQ and ILCR confirmed that there was no significant non-carcinogenic effect (HQ < 1) from benzene but found a high enough lifetime cancer risk from benzene to exceed the CPCB benchmark in both 2019 and 2020. The coupling of spatial interpolation, multivariate source fingerprinting, reactivity scaling and exposure modeling yields a robust and reproducible engineering decision support tool for local urban VOC mitigation efforts and overall air quality sustenance.