Introduction: Heavy metals have an important role in human health because of their nutritive value and possible adverse effects. The objective of this study was to assess level of heavy metals and selenium in rice harvested in the Golestan Province, Iran. Materials and Methods: This study was conducted in the Golestan Province, northern Iran. The area under rice cultivation is 45714 acres. Overall, 69 rice samples were collected from rice farms in different areas of the province including high-risk (42 samples) and low-risk areas (27 samples) for esophagus cancer (EC). Concentrations of heavy metals were measured by polarograph. Voltammetric analysis was carried out using 797 VA computrace (Metrohm). Results: Maximum concentrations of zinc, cadmium, lead, copper, nickel, cobalt and selenium in high-risk areas for EC were 70.6, 0.41, 5.05, 14.4, 8.8, 0.88 and 0.48 mg/kg as dry weight, respectively. Maximum concentrations of these elements in the low-risk area for EC were 88.4, 0.37, 3.9, 17.2, 8.1, 0.27 and 0.25 mg/kg as dry weight, respectively. The concentration of Se in high-risk areas were significantly higher than that in low-risk areas (P<0.05). Conclusions: Heavy metals and Se may act as possible risk factors for EC in the Golestan Province, which should be considered when designing cancer control programs in this area.

The number of diabetics is growing every day. In addition to the main risk factors of type 2 diabetes (obesity, age and etc.) other environmental risk factors such as persistent organic pollutants are also considered. Dichlorodiphenyldichloroethylene is one of the persistent organic pollutants which are produced by the pesticide DDT metabolized and its effects of type 2 diabetes are taken into consideration of many investigators. Inconsistency in the results caused to try to achieve a detailed assessment of the effect of dichlorodiphenyldichloroethylene on type 2 diabetes by systematic review and meta-analysis. In this review study after a systematic review, finally 6 prospective and 7 cross-sectional studies were obtained. After approving the heterogeneity of the studies based on random effect model, it was calculate the mean of odds ratio. Meta-analysis of the pooled random effects of Dichlorodiphenyldichloroethylene was done with type 2 diabetes in prospective and cross-sectional studies. In prospective studies, the highest and lowest odds ratio was 6.1 (95%CI: 1.36-27.27) and 1.01 (95%CI: 0.59-1.70) and cross-sectional studies was 5.5 (95%CI: 1.2-25.10) and 0.61 (95%CI: 0.32-1.15), respectively. In the all studies (sum of prospective and cross-sectional), in the random effect model odds ratio was 1.52 (95%CI: 1.26-1.84) and heterogeneity was 52.1% (ρ heterogeneity =0.009). Increasing concentration of Dichlorodiphenyldichloroethylene in the serum and adipose tissue increased the risk of type 2 diabetes significantly (P<0.001). The results of this review study support the role of dichlorodiphenyldichloroethylene as an environmental risk factor for type 2 diabetes.