Mapping residual water fluoride levels and geological patterns in a rural semi-arid area of Brazil

Some areas of Brazil have natural sources of fluoride in their water supply. Identifying these areas is an important measure to guide oral health measures when implementing safe fluoride applications, either alone or in combination. The study aims to map residual water fluoride levels and geological patterns in a rural semi-arid area of Brazil. Therefore, water samples were taken from 24 rural areas in the municipality of Poço de José de Moura, located in the tropical semi-arid areas of the country. The samples were analyzed in triplicate with a special fluoride electrode and a shallow water buffer, namely the legendary fortified water (secretive). The residual fluoride values in the samples ranged from 0.04 ± 0.00 mgF/mL in São Geraldo to 6.81 ± 2.81 mgF/mL in Monteiro. Therefore, residual fluoride was found in all groundwater samples analyzed in this study, with several sites exceeding the WHO guideline characterization of a potential risk of dental fluorosis in children and high levels of fluoride that may be related to geological formation factors.