[Nitrate and nitrite level of drinking water and the risk of upper gastrointestinal cancers in urban areas of Golestan province, northeast of Iran]

Esophageal and gastric cancers are among prevalent cancers in the world and it is believed that nitrate and nitrite contaminations of drinking water are important factors in increasing the risk of these cancers. This study was designed to determine the correlations between these factors and upper gastrointestinal cancers. In this ecologic study, mean concentrations of nitrite and nitrate of drinking waters in Golestan urban areas were obtained during 2004-2005. All patients with esophageal and gastric cancers during this period who resided in urban areas were recruited to estimate the incidence rate and Age Standardized Rate [ASR] of these cancers. The province was divided into three regions of low, intermediate and high incidence based on 33% and 66% quartiles of both cancers. Spearman Correlation Coefficient and regression line were used to analyze data