Monitoring BTEX compounds and asbestos fibers in the ambient air of Tehran, Iran: Seasonal variations, spatial distribution, potential sources, and risk assessment

The toxic air pollutants such as benzene, toluene, ethylbenzene and xylene (BTEX) as well as asbestos are considered hazardous because of their role in adverse impacts on human health. Accordingly, this research was conducted to evaluate the levels, seasonal variations, spatial mapping, potential sources, and health risk assessment of BTEX compounds as well as asbestos fibres in the ambient air of Tehran. Air samples were collected by the NIOSH1501 method at 15 different sample stations from March 2018 to February 2019. Charcoal glass tube was used to collect samples and BTEX concentration was further determined using GC-FID method. The sampling of asbestos fibres was carried out via a low volume peripheral pump with analysis performed according to the NIOSH 7400 method via phase contrast microscopy (PCM). The findings showed that the mean±SD concentrations of ∑BTEX were 33.44 ± 11.77 and 59.97 ± 33.76 µg/m3 in warm and cold seasons, respectively. It was 1.46 × 10−3 and 2.31 × 10−3 fibre/ml for asbestos in the warm and cold seasons, respectively. The spatial mapping indicated that the maximum levels of both pollutants were observed in sampling sites S1, S11, and S15, which were located close to factories downtown (S1) and heavy traffic roads (S11 and S15). The mean inhalation lifetime cancer risk (LTCR) value for benzene was 1.64 × 10−5, which was higher than US EPA and WHO recommended limits. Further, the excess lifetime cancer risk (ELCR) suggested that the exposure to asbestos fibre in Tehran would cause the risk of developing cancer in 0.5 to 3.53 people per every 1000 individuals. Hence, much suitable managing strategies are required to control the concentration of these pollutants in the ambient air of Tehran