Factors such as the route of exposure, the chemical composition of the mixture, the presence of co-exposures, and genetic susceptibility are likely to explain inter-organ differences in the carcinogenicity of PAH (IARC Working Group, 2010).Cross-sectional studies in high-incidence areas of esophageal squamous cell carcinoma (ESCC) in Linxian (China) and Golestan Province (Iran) indicate that the i