Extensive investigation of seasonal and spatial fluctuations of BTEX in an industrial city with a health risk assessment.

There are many pollutants in the air that can be harmful to human health. Their impact varies based on factors such as the kind of pollutant, duration of exposure, and concentration levels. Volatile organic compounds are particularly significant carcinogens among the various pollutants present in the air. Consequently, people who are exposed to these harmful airborne pollutants suffer permanent consequences. This study examines the properties of BTEX compounds-benzene, toluene, ethylbenzene, and xylene-as well as their sources and risk assessments throughout a one-year period from March 21, 2019, to March 20, 2020, in Karaj, Iran's largest industrialized city. First, utilizing a geographical information system that covered the entire city, 17 locations within Karaj were chosen for this purpose. Then, samplings were carried out in the spring, summer, autumn, and winter months with the NIOSH 1501 method. During the research period, 68 samples of BTEX compounds were collected. The adsorption of these contaminants on the activated carbon adsorbents was performed using an environmental sampling pump with a flow rate of 0.2 L/min for 1 h. The samples were subsequently prepared using a carbon disulfide solution and injected into a GC-FID for analysis. In this research, the average annual concentration of BTEX compounds in the air of Karaj city was obtained at 33.01 µg/m