Fluoride (F) is harmful to human health and knowledge of spatiotemporal distribution of F content in groundwater is thus a prerequisite for taking preventive measures.

This communication reports F incidence in groundwater and its relation with the prevalence of fluorosis  in Tamnar area, Raigarh District, Chhattisgarh, India. Nearly 18% of the sampled wells had F concentrations above the desirable limit (> 1.0 mg/l), the highest value being 8.8 mg/l. High F concentrations primarily occurred in coal-bearing Barakar Formation of the Gondwana Supergroup. Prevalence of dental fluorosis was observed in five villages, viz. Dholnara, Kunjhemura, Muragaon, Pata and Saraitola; whereas skeletal fluorosis was found to occur only in Muragaon.

The spatial distribution of F in groundwater, as indicated by hydrogeochemical analyses, corroborated well with the prevalence of dental and skeletal fluorosis. It is envisaged that, in addition to the people already affected, a large fraction of the population in the area is at potential risk, especially considering that the region falls in the coal mining and industrial belt. The health-risk map prepared using a Geographic Information System provides baseline information in taking mitigation measures. 

The findings are significant as the area falls in the potential mining and industrial belt of Chhattisgarh, emphasizing a large population may be at potential risk. The rock and water interaction with accompanying ion exchange processes in micas and clay minerals appear to be the primary mechanism for high concentration of F– in groundwater. Systematic study needs to be undertaken in the Gondwana rocks in the surrounding area, with an emphasis on the coal-bearing Barakar Formation, to delineate unsafe zones.