Fluoride as a pollutant in some Brazilian aquifer systems

Abstract

Evidence of activity concerned with human health and water supply has been found in civilizations throughout human history, where archeological evidences indicate that groundwater has been used since prehistoric times, especially in arid regions. Springs, for example, provided an easily available supply of freshwater, especially valuable during dry periods, and villages developed around them. The use of groundwater by people in the Australian Northern Territory has began in prehistoric times with the aborigines. Aboriginals largely relied on lagoons, springs and shallow unlined wells for their water supplies. The 19th century brought the Industrial Revolution and also a whole new perspective on the water use as chemicals in addition to microbials started to be more carefully evaluated in the world’s water supplies, requiring the use of much more sophisticated water treatment methods. Fluoride has been identified as a groundwater pollutant worldwide. It is an ion of the chemical element fluorine, which belongs to the halogen group. Most of the fluoride found in groundwater is naturally occurring from the breakdown of rocks and soils or weathering and deposition of atmospheric volcanic particles. At low concentrations fluoride can reduce the risk of dental cavities. However, exposure to somewhat higher amounts of fluoride can cause dental fluorosis. In its mildest form this results in discolouration of teeth, while severe dental fluorosis includes pitting and alteration of tooth enamel. In groundwater, the natural concentration of fluoride depends on the geological, chemical and physical characteristics of the aquifer, the porosity and acidity of the soil and rocks, the temperature, the action of other chemical elements, and the depth of the aquifer. This chapter reports the presence of this anion in different aquifer systems in Brazil, whose groundwater is used for human consumption. The data reported will compared with other reported in the literature, thus, contributing to the database increase on the presence of this pollutant in groundwaters occurring elsewhere.