Gas flares contribution in total health risk assessment of BTEX in Asalouyeh, Iran

Abstract

The health risk assessment of benzene, toluene, ethylbenzene and xylenes (BTEX) associated with the combustion of gas in gas flares of one of the largest gas refinery complex in Iran (South Pars gas complex in Asalouyeh, 1–10 phases) has been conducted based on Office of Environmental Health Hazard Assessment’s (OEHHA) method. In this regard, AERMOD dispersion model coupled with WRF model has been used to predict the ground level concentration of pollutants emitted from gas flares. The accuracy of the dispersion model has been verified with measured ambient SO2 data. The risk assessment results have shown that the chronic noncarcinogenic risk of BTEX emitted from gas flares is in the acceptable range in the residential area and most of refineries site. Regarding acute noncarcinogenic risk, the hazard indices (HIs) are only greater than one in refineries sites and are less than permitted level elsewhere in the study area. For carcinogenic risk, the cumulative risk of benzene and ethylbenzene are greater than 10−6 in refineries sites and two cities (Asalouyeh and Nakhl Taghi), but in two camps nearby the gas flaring sites, the value is less than the allowable limit. Besides, the relative contribution of gas flaring in health risk assessment of BTEX is accomplished by calculating the health risk parameters with the measured BTEX concentrations at 10 receptors, which reveal the cumulative effects of all potential sources of BTEX throughout the study area. The comparison of health risk parameters has shown that the health risk of BTEX associated with flaring is in average 42 %, 2.6 % and 10.8 % of the overall health risk of BTEX in industrial areas, two cities and camps, respectively. It can be concluded that the contribution of gas flaring in industrial areas is noticeable and application of emission reduction policies at gas flaring, has a major effect on industrial areas and maybe has minor effects on the air quality of the residential areas.