Potential oral exposure to low-dose chromium and stomach cancer mortality in the population in the interior of Sao Paulo State, Brazil

Total chromium concentrations from 0.45 to 110 mu g/L have been detected in the Bauru Water Table in the Sao Paulo State, Brazil, sometimes exceeding the quality threshold adopted by Brazilian legislation, which is 50 mu g/L. According to the Sao Paulo State Environmental Company (CETESB), part of the chromium consists of the hexavalent form [Cr(VI)], which presents controversial evidence as to carcinogenicity by the oral route. This article aims to evaluate the effect of exposure to low-dose Cr(VI) on gastric cancer mortality in the population 15 to 75 years and older who consumed water from the Bauru Water Table from 2004 to 2015. An ecological study was performed in 326 municipalities situated in the Western Sao Paulo High Plain and that used water from the Bauru Water Table. The associations were estimated via linear regression, using indicators of exposure to chromium (proxy) and standardized mortality ratio (SMR) for gastric neoplasms as the response variable. The Municipal Human Development Index (MHDI) was used to control for possible socioeconomic differences in the target population. The estimated SMR for gastric cancer corresponded to 79% of the expected deaths, and the risk was lower in municipalities that have water treated by the Sao Paulo State Basic Sanitation Company (SABESP), with special attention to the female population (beta = -0.146; 95%CI: -0.270; -0.021; p = 0.022). Although the research data are limited, 77 (23.6%) of the municipalities evaluated reveal an increase in the risk of gastric cancer. Among these, nearly 70% are supplied by water tables associated with river basins with geochemical Cr(VI) anomalies.