Global analysis and prediction of fluoride in groundwater

TLDR

Millions of people worldwide are harmed by chronic exposure to geogenic fluoride in groundwater, which can cause dental mottling and skeletal fluorosis, yet many regions lack regular testing and the WHO limits drinking water to 1.5 mg/L. This study presents a global fluoride hazard map derived from machine learning on over 400,000 measurements, aiming to estimate the human population at risk. The map is generated by training a machine‑learning model on the dataset and by analyzing key hydrochemical and environmental factors that drive fluoride accumulation. The resulting map highlights hotspots in central Australia, western North America, eastern Brazil, and many parts of Africa and Asia, indicating that roughly 180 million people—predominantly in Asia and Africa—are at risk, with Africa hosting 14 of the top 20 affected countries.

Abstract

Abstract The health of millions of people worldwide is negatively impacted by chronic exposure to elevated concentrations of geogenic fluoride in groundwater. Due to health effects including dental mottling and skeletal fluorosis, the World Health Organization maintains a maximum guideline of 1.5 mg/L in drinking water. As groundwater quality is not regularly tested in many areas, it is often unknown if the water in a given well or spring contains harmful levels of fluoride. Here we present a state-of-the-art global fluoride hazard map based on machine learning and over 400,000 fluoride measurements (10% of which >1.5 mg/L), which is then used to estimate the human population at risk. Hotspots indicated by the groundwater fluoride hazard map include parts of central Australia, western North America, eastern Brazil and many areas of Africa and Asia. Of the approximately 180 million people potentially affected worldwide, most reside in Asia (51–59% of total) and Africa (37–46% of total), with the latter representing 6.5% of the continent’s population. Africa also contains 14 of the top 20 affected countries in terms of population at risk. We also illuminate and discuss the key globally relevant hydrochemical and environmental factors related to fluoride accumulation.