Integrated assessment of fluoride occurrence and groundwater usability: a critical concern for drinking water sustainability and irrigation in semi-arid region of West Bengal, India

Occurrence of fluoride (F−) at elevated levels in groundwater (GW) has become
a major concern as it is associated with serious health issues like dental-skeletal
fluorosis, severe neurological disorders, and abnormal enzymatic activities. This
study conducted, in Purulia district in West Bengal, India, to understand the factors
influencing F⁻ enrichment in GW in the context of hydroclimatic variability, its
suitability for drinking water and irrigation purposes, and associated health risks.
Results show that 37.5% of collected GW samples (n = 24) exceed the permissible
limit of WHO (1.5 mg/L). The average and highest F⁻ concentrations recorded at
1.4 mg/L and 2.2 mg/L, respectively. A positive correlation between F⁻, Ca²⁺, and
Na⁺ indicates that rock weathering significantly contributes to F⁻ mobilization. GW
in this area is of Na-Mg-Cl type as indicated by the piper plot. The trend of rainfall
and temperature shows an inverse relationship with F− content and GW level is one
of the major aggravating hydroclimatic factors for mobilization of F− in GW. The
study showed that, GW is suitable for irrigation based on geochemical indices, but
elevated fluoride and moderate salinity have degraded its quality, raising concerns
about increased F− exposure through dietary intake. Consequently, Dental fluorosis
prevalence is notably higher among individuals aged 10–20, 21–30, and over 50, with
males consuming more F⁻-rich water than females across all age groups. So, it can
be concluded that, hydroclimatic variability plays a key role in driving geochemical
processes that mobilize fluoride in groundwater. Therefore, identifying safe aquifers
while considering demographic and climatic factors is essential for managing fluoride
contamination and mitigating health impacts.