Assessment of benzene and toluene emissions in National Capital Region (NCR): Implications for health risks and ozone formation

This study investigates benzene and toluene concentrations in Delhi and National Capital Region (NCR), India, assessing health risks and impacts on air quality, focusing on their role in ozone formation. Data from 56 monitoring stations identified 18 locations where benzene levels exceed the national safe limit, primarily due to traffic emissions and seasonal variations. Benzene concentrations peaked at 15.06 µg/m³ in Loni, Ghaziabad, during winter. Seasonal analysis indicated higher benzene levels during winter and post-monsoon periods due to lower planetary boundary layer heights (PBLHs) trapping pollutants near the ground. Health risk assessments revealed probable cancer risks for residents, with children facing higher risks than adults. Using the Ozone Formation Potential (OFP) metric and Maximum Incremental Reactivity (MIR) coefficients of 0.72 for benzene and 4.0 for toluene, the study predicted OFP values for various hotspots. Toluene's significant contribution to ozone formation was evident, with the highest concentration observed at Charkhi Dadri, Haryana (29.65 ± 2.26 µg/m³), surpassing the WHO’s air quality guidelines of 120 µg/m³, and the highest benzene concentration at Loni (7.3 ± 0.8 µg/m³). Toluene/benzene ratio and principal component analysis identified automobiles and industrial activities as significant pollution sources. The study underscores the urgent need for stricter emission controls, cleaner fuels, and improved urban planning to reduce these pollutant's negative impacts on the environment. Elevated VOC levels and associated health risks necessitate immediate action to protect public health and improve air quality in Delhi NCR. These results emphasize critical need for interventions to address benzene and toluene pollution comprehensively.