Fluoride contamination in groundwater and associated health risks in Karbi Anglong District, Assam, Northeast India.

Health hazards due to excess intake of fluoride via groundwater contamination are a major concern worldwide. This study provides a comprehensive report on the human health risks associated with the consumption of groundwater contaminated by fluoride. Several groundwater samples were collected across 8 blocks of Karbi Anglong district of Assam, India. The concentration of fluoride was observed in the range of 0.15-17.13 mg/L. In 4 out of 8 studied blocks, the mean fluoride level exceeded the permissible limit (1.5 mg/L) as prescribed by the World Health Organization. Elevated fluoride levels in some parts of the district may be attributed mainly to dissolution from fluoride-containing minerals in the granitic rocks and regional geological settings. The health risk of fluoride was assessed in terms of hazard quotient (HQ). The HQ was observed in the ranges of 0.06-10.7 (adult) and 0.2-35 (children). Mean HQ values exceeded the safe level (HQ > 1) for children in all blocks, except B-6 and B-8. For adult population, the HQ value was above the safe limits in 13-40% of the sampled locations in different blocks and HQ values were within safe limits in B-6 and B-8. These findings suggest that some sites in the district need serious attention in order to ensure the health safety of local residents.