Global groundwater contamination by geogenic fluoride

Area of Science:

• Environmental Science
• Geochemistry
• Public Health

Background:

• Fluoride (F¯) is a widespread geogenic groundwater contaminant.
• Elevated fluoride levels exceed safe limits (WHO: 1.5 mg L⁻¹), leading to dental and skeletal fluorosis.
• Drinking water is the primary pathway for human exposure to excess fluoride.

Purpose of the Study:

• To review the global incidence, distribution, and mobilization mechanisms of fluoride in groundwater.
• To identify knowledge gaps in fluoride contamination worldwide.
• To synthesize findings on contaminated aquifers, defluoridation methods, and safe water strategies.

Main Methods:

• Systematic literature review using the PRISMA 2020 framework.
• Review period: 1953–2025.
• Synthesis of global data on fluoride occurrence, geochemistry, and mitigation.

Main Results:

• Fluoride contamination is prevalent across Asia, Africa, the Middle East, Europe, and the Americas.
• Key drivers include fluorine-bearing minerals, high pH, Na-HCO₃ water types, and low calcium concentrations.
• Hotspots include the East African Rift Valley, Indo-Gangetic plains, northern China, and volcanic regions; arid/semi-arid areas show higher levels.

Conclusions:

• Despite extensive research, monitoring gaps and mitigation challenges persist, especially for vulnerable rural populations.
• Scalable, cost-effective defluoridation solutions are crucial for providing safe drinking water.
• Prioritizing vulnerable areas and communities is essential to address the global fluoride contamination issue.