Health Risk Assessment of Fluoride and Nitrate in Groundwater

Fluoride and nitrate are common inorganic constituents of groundwater that pose significant non-carcinogenic health risks when concentrations exceed recommended limits. Fluoride occurs naturally through dissolution of fluoride-bearing minerals and can be augmented by industrial effluents, leading to dental and skeletal fluorosis in populations consuming high-fluoride water. Nitrate enters aquifers primarily via agricultural fertiliser leaching, septic systems and manure applications and can induce methemoglobinaemia in infants and has been linked to other adverse health outcomes. Health risk assessment frameworks combine contaminant concentration data, exposure parameters (such as ingestion rates and body weight) and dose-response metrics to calculate hazard quotients (HQ) and hazard indices (HI) for sensitive age groups. Probabilistic approaches, including Monte Carlo simulation, quantify the uncertainty and variability in exposure estimates. Spatial mapping using geographic information systems (GIS) supports the identification of high-risk zones, while hydrochemical facies analysis elucidates the geochemical controls on contaminant distribution. Effective assessment informs water-resource management interventions—such as targeted defluoridation, nitrate removal and public-health advisories—to mitigate risks, especially for infants and children in semi-arid and rural settings worldwide.

Research from Nature Portfolio

Recent studies have applied multivariate statistical techniques and water-quality indices to characterise fluoride-rich aquifers and assess associated health risks. A 2024 investigation of groundwater in a major alluvial plain demonstrated that sodium-bicarbonate and calcium-chloride facies dominate fluoride mobilisation, with groundwater quality index values indicating that most samples are unsuitable for direct consumption. Principal component analysis highlighted geogenic fluoride sources, underscoring the need for pre-treatment before use. Another study in 2021 compared centralised and decentralised supply systems in a fluoride-endemic region and found that decentralised wells exhibited higher fluoride concentrations and hazard indices above unity for infants and young children. Seasonal sampling revealed that geological variations and local waste discharge influence fluoride enrichment, and that infants and children are disproportionately affected by non-carcinogenic risks.

Health Risk Assessment of Fluoride and Nitrate in Groundwater publication trend

The graph below shows the total number of articles in health risk assessment of fluoride and nitrate in groundwater across all publications each year (not limited to Nature Index journals).

Technical terms

Hazard Quotient (HQ): The ratio of estimated daily intake of a contaminant to a reference dose, indicating non-carcinogenic risk when above unity.

Hazard Index (HI): The sum of multiple hazard quotients for co-exposures, used to assess cumulative non-carcinogenic risk.

Monte Carlo Simulation: A probabilistic technique that uses repeated random sampling to characterise uncertainty and variability in risk assessment inputs.

Hydrochemical Facies: Classification of groundwater based on dominant ion composition, reflecting geochemical processes affecting water quality.

Geogenic vs Anthropogenic: Geogenic refers to naturally occurring sources (e.g., rock weathering), while anthropogenic denotes human-derived inputs (e.g., fertiliser leaching).

References

1. Health risk assessment of nitrate and fluoride toxicity in groundwater contamination in the semi-arid area of Medchal, South India. Applied Water Science (2021).
2. Groundwater quality assessment using water quality index and principal component analysis in the Achnera block, Agra district, Uttar Pradesh, Northern India. Scientific Reports (2024).
3. Nitrate in Groundwater Resources of Hormozgan Province, Southern Iran: Concentration Estimation, Distribution and Probabilistic Health Risk Assessment Using Monte Carlo Simulation. Water (2022).