Karolinska Institutet Mar 7 2025 Elevated concentrations of fluoride can occur in well water, and in some countries, it is added to drinking water to counteract caries in the population. A study from Karolinska Institutet in Sweden now supports a few previous studies indicating that exposure to fluoride during the fetal stage or early childhood may impair cognition in children. The study is published in the journal Environmental Health Perspectives. Fluoride occurs naturally as fluoride ions in