Unveiling Fluoride Dynamics in Northeast Indian Tea: Geospatial Distribution and Health Risk Assessment

Abstract

Tea (Camellia sinensis) is a perennial plant and a strong fluoride (F⁻) hyperaccumulator, requiring acidic soil for optimal growth and quality. Tea plants readily absorb F⁻ from the growing medium because the soil in which tea is grown is acidic. Environmental factors (soil pH, geological sources, temperature, and rain fall) and human activities are the main contributors to F⁻ in tea. We investigated the total F⁻ content in 100 samples each of CTC and orthodox teas collected from the tea-growing regions of Northeast India. Comparatively, CTC (119.7 µg/g) tea showed higher F⁻ content than orthodox tea (76.39 µg/g), with mean fluoride concentrations below European Commission Maximum Residue Limit (400 mg/kg). The non-carcinogenic anthropogenic risk from F⁻ in tea was evaluated using Hazard Quotient (HQ) and Monte Carlo Simulation (MCS) values, which were found to be < 1 for men, women, and children, with children showing higher F⁻ intake from tea than adults. Positive Matrix Factorization (PMF) identified geogenic sources and industrial drilling as the main contributors to increased F⁻ in tea. Additionally, a geostatistical tool using Inverse Distance Weighting (IDW) and hot-spot analysis was developed to predict the spatial distribution and hot and cold spot patterns of F⁻ in tea. This study significantly enhances the understanding of F⁻ in tea from the Northeast region, indicating that contemporary Northeast Indian tea does not pose any F⁻ related health hazards, though regular monitoring for any elemental contamination remains important for tea quality and production.