Fluoride levels in Texas groundwater

The purpose of this study was to compile, map, and evaluate regional patterns of fluoride concentrations in Texas groundwater. County-median fluoride levels were calculated from nearly 7,000 wells distributed among 237 Texas counties. Four regions having high fluoride levels were identified. These regions occupy parts of west, southwest, north-central, and south Texas. At least 50 percent of the fluoride observations in each of five Texas counties exceeded the primary drinking water standard of 4.0 mg/L. All of those counties are located in northwest Texas. Statewide, 25 counties had a median fluoride level above the secondary standard of 2.0 mg/L. Several factors contribute to elevated fluoride levels in Texas aquifers, including seepage from nearby saline formations, sparse recharge and dilution, and native mineral constituents of the aquifers. Results of this study suggest that: (1) regional geology influences fluoride concentrations in Texas, (2) statewide, the pattern is not random, (3) fluoride levels are generally higher in the western part of the state, and (4) regions which warrant further monitoring include west-central and north-central Texas.