BTEX exposure-driven human health risks: a comprehensive analysis during COVID-19 lockdown in metropolitan city, India.

Benzene, toluene, ethylbenzene, m,p-xylene, and o-xylene (BTEX) are released into the atmosphere from various sources and cause several long-term health problems, especially in metropolitan cities. This study used a C6-C12 analyzer with thermal desorption gas chromatography to measure ambient BTEX levels from January to May 2020, covering pre-lockdown (phase 0) and lockdown phases (I-IV) during COVID-19 pandemic in Ahmedabad, India. The average ƩBTEX concentration dropped from 40.51 µg/m3 (before lockdown) to 7.86 µg/m3 (during lockdown), with an ~ 81% reduction. Toluene showed the relatively less reduction of 76%, while benzene, ethylbenzene, and xylenes each decreased over 80%. The largest hazard quotient (HQ) reduction was observed from phase 0 to phase II, with a 93% and 79% reduction in benzene and toluene, respectively. The hazard index (HI) for BTEX compounds from phase 0 to phase IV was 5.60E-01, 2.40E-01, 4.33E-02, 3.73E-02, and 3.12E-02, with significant drops in phases I and II. HQBenzene showed the strongest correlation with HI across all phases, whereas the most significant HI reductions occurred during phase I (51.52%) and phase II (85.71%). The incremental lifetime cancer risk (ILCR) showed benzene's cancer risk dropping 93.07% compared to ethylbenzene's 89.4% from phase 0 to phase II. Later phases showed less reduction due to resumed activities. Many data points exceeded the definite risk threshold (1E-04). ILCRBz decreased to 4.76E-06 by phase IV, a 95.01% decline. Thus, present study demonstrates how lockdown measures reduced BTEX pollution and associated human health risks.