Environmental impact assessment due to the intake of uranium contained in surface waters in a semi-arid region in Brazil

Abstract

In Santa Quitéria City, part of the population uses surface water for potation. These waters do not undergo any treatment before consumption. As the region has a deposit of uranium, assessing water quality becomes important. In the present study, the uranium activity concentration (AC) in becquerels per liter was determined in water samples from six points. Univariate statistics showed differences between the soluble and the particulate fraction (soluble AC > particulate AC). The particulate fraction showed no variation in AC among the six points. On the other hand, the soluble fraction and the total fraction presented different ACs between them. The multivariate statistics allowed to separate the soluble from the particulate fraction of the points. The same tools applied to the total fraction made it possible to differentiate the sampling points, grouping them ((#1, #2); (#3, #4), and (#5, #6)). The maximum mean value of AC found was 0.177 Bq∙L^-1, corresponding to 25% of the chemical toxicity limit (0.72 Bq∙L^-1). The maximum mean dose rate, 2.25 µSv∙year^-1, is lower than the considered negligible dose rate (> 10 µSv∙year^-1). The excess lifetime cancer risk was 10^-6, two orders of magnitude smaller than the threshold considered for taking action. The assessment parameters used in this work indicate that the risk due to the uranium intake by the local population is negligible.

Keywords: Brazil; Chemical uranium exposure; Drinking water quality; Effective dose; Lifetime cancer risk; Radiological uranium exposure; Risk assessment; Semi-arid ecosystems.