Probabilistic human health risk assessment and contributions to ozone and SOA formation potentials associated with BTEX and formaldehyde emissions in a tropical city (Salvador, Bahia, Brazil)

Abstract

The BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) and formaldehyde (FA) have harmful impacts on human health and are also important precursors of tropospheric ozone and secondary organic aerosols (SOA). Thus, the objective of this study was to perform a human health risk assessment considering the lifetime carcinogenic (LCR) and non-carcinogenic (as hazard quotient (HQ)) risks for 3 different age groups associated with exposure to BTEX and FA by inhalation using a probabilistic approach with Monte Carlo simulation, as well as to evaluate the contributions of these compounds to ozone formation potential (OFP) and SOA formation potential (SOAFP), at seven sites in the city of Salvador, Bahia, Brazil, during the dry and rainy periods. The HQ values associated with BTEX and FA compounds were below the limit set by the USEPA (HQ = 1) for all groups in both periods. The LCR values for benzene and FA at the 95th percentile considering 3 evaluated groups were 2.49 × 10⁻⁶, 3.56 × 10⁻⁶, 9.16 × 10⁻⁶ and 1.83 × 10⁻⁵, 2.53 × 10⁻⁵, 6.55 × 10⁻⁵ in the dry period and 2.83 × 10⁻⁶, 3.94 × 10⁻⁶, 1.01 × 10⁻⁵ and 7.97 × 10⁻⁶, 1.02 × 10⁻⁵, 2.40 × 10⁻⁵ in the rainy period, respectively, being all values above the acceptable limit by the USEPA (1.0 × 10⁻⁶). For all 3 groups of the population, the LCR values for benzene and FA were higher during the rainy period and dry period, respectively, following the same pattern as the concentrations. FA, xylenes, and toluene accounted for up to 97.0% of total OFP, whereas toluene, benzene, and xylenes contributed up to 88.5% of total SOAFP. The results obtained showed the need to adopt measures to reduce BTEX and FA emissions in order to minimize the impacts on health of the exposed population and on air quality.