Fluoride is a double-edged sword in its relationship to human well-being because it is a beneficial element when present in the right amount in drinking water. Beneficial levels of fluoride promote good health, but slightly more or less is harmful. Fluoride occurs naturally in minerals and rocks and chemical analysis of water samples drawn from wells reveal that it dissolves into groundwater in ionic form (F–). Fluoride concentrations at levels above those specified for safe drinking water (between 1 and 4 mg/L depending on the country) is a widely distributed problem but is most severe in arid and semi-arid countries, which is where nearly 40 percent of the global population resides. It is one of more than a dozen naturally occurring elements in nature that are essential or beneficial to human health when consumed in the appropriate amounts, but fluoride is unique because its benefit is largely related to dental health. Addition of fluoride to municipal drinking water to promote dental health is controversial because it can be harmful to human health when consumed in water at concentrations above the optimal concentration of 0.7 to 1 mg/L as it can cause fluorosis, which is a weakness of the bone and teeth and may result in calcification of ligaments. Most wells around the globe have not been tested for fluoride and it is likely that excessive geogenic fluoride occurs in millions of domestic water wells. It is estimated that more than 200 million people suffer from fluorosis and an equal or greater number suffer from increased dental caries due to a lack of fluoride.
This book describes the occurrence, distribution, origins and impacts of fluoride in groundwater and summarizes methods for fluoride removal from drinking water. It includes the most comprehensive global listing of reported fluoride occurrences which includes more than 60 countries. This book presents the geochemical principles that govern fluoride in groundwater which provides a basis for expectations concerning fluoride problems when there is minimal direct knowledge. The two authors, Dr. Kirk Nordstrom of the United States and Dr. Pauline Smedley of the United Kingdom, are exceptionally experienced hydrogeochemists who have published extensively about the occurrence of geologically-derived constituents, including fluoride, in groundwater. Their work encompasses theory and practice with a global perspective. It is suspected that there are many millions of people in both high- and low-income nations unknowingly drinking groundwater with unsafe levels of fluoride. This book provides the scientific knowledge base for better recognition of fluoride in groundwater supplies and for action toward alleviating the problem.
John Cherry, The Groundwater Project Leader
Guelph, Ontario, Canada, November 2021