Association Between Heavy Metals and Colon Cancer: An Ecological Study Based on Geographical Information Systems in Northeastern Iran

Abstract

BackgroundExposure to environmental pollutants such as heavy metals has been introduced as a possible contributor to increasing the risk of colon cancer. We aim to explore the associations between heavy metals and the age-standardized incidence rate (ASR) colon cancer in Northeastern Iran.MethodsCancer data were drawn from the population-based cancer registry of Golestan province, Northeastern Iran. The heavy metals’ samples were collected from 69 rice milling plants in the study area. Then, the concentration level of seven heavy metals, including Cadmium, Nickel, Cobalt, Copper, Selenium, Lead, and Zink was measured. The Kriging algorithm was used to interpolate the heavy metals' concentration on the surface of the study area. The exploratory regression analysis was conducted to build the ordinary least squares (OLS) models on every possible combination of the candidate explanatory variables. Finally, the best OLS models were chosen to show the effect of heavy metals on colon cancer.ResultsGenerally, heavy metals were higher in central part of the province. The analyses showed that the high concentration of Cobalt was associated with the high ASR of colon cancer in men. In contrast, the Selenium concentration was higher in areas with lower ASR of colon cancer in men. A significant regression equation for men colon cancer was found (F(4,137)=38.304, P<.000) with an adjusted R2 of 0.77. The predicted ASR of men colon cancer was -58.3581 with the coefficients for Cobalt= 120.329780; Cadmium= 80.603505; Selenium= -6.069037; Nickel= -3.086802; and Zink= -0.405843. The effect of Copper and Lead on men colon cancer was not significant. We did not find a significant model for women colon cancer.ConclusionThere may be a possible negative correlation between selenium concentration and lower risk of colon cancer in men. Furthermore, the higher cobalt concentration may be related to an increased risk of men colon cancer.