Comparative health risk assessment of BTEX exposures from landfills, composting units, and leachate treatment plants

This study assessed and compared the carcinogenic risks and hazard ratios of exposure to benzene, toluene, ethylbenzene, and xylene (BTEX) within different units of a municipal solid waste disposal facility (Tehran, Iran), including the leachate treatment plant (LTP), the landfill, and a composting unit. Eight stations within the landfill site were sampled during summer and winter using NIOSH method 1501. The health risk assessment was conducted using the probabilistic risk model Oracle Crystal Ball. The probability distributions of risks were estimated. The average concentrations (±SD) of benzene, toluene, ethylbenzene, xylene, and total BTEX were 9.01 (± 5.22), 11.44 (± 6.62), 14.56 (± 9.8), 24.06 (± 14.86), and 59.09 (± 32.38) ppbv, respectively. BTEX concentrations were significantly higher downwind of the disposal site compared to those in the upwind direction. The maximum carcinogenic risks of benzene in LTP, landfill, and composting unit were in excess of 1 × 10⁻⁴. Hazard ratios of BTEX were sufficiently low so as not to pose a significant risk to the workers' health. However, maximum hazard ratios of benzene and total BTEX within landfill exceeded 1. In general, lifetime cancer risks and hazard ratios of BTEX were higher in landfill area compared to leachate treatment plant or the composting unit. Sensitivity analyses indicated that concentration and exposure duration had the largest impacts on the variance of the estimated risks. Individuals working in the landfill were at higher risk. An action plan is needed to reduce the risks from BTEX exposure in waste facilities by reducing the concentrations and/or exposure duration.