Meta-analysis and risk assessment of fluoride contamination in groundwater

This study aimed to carry out a systematic review of meta-analysis and risk assessment of the global pooled concentration of fluoride and identify the influencing factors of fluoride loads in groundwater. The study extracted data from 36 most prevalent regions of 20 countries in the world through various search engines using keywords as well as Boolean operators and follows the PRISMA statement in every phase of literature searching. The study illustrated the pooled concentration of fluoride in the selected 20 countries was 2.1267 mg/L (1.650, 2.604) at 95% confidence interval, which was higher than the WHO standards limit of 1.5 mg/L. The results of the meta-analysis suggested that pH, Na, HCO₃ and rainfall was significantly positively correlated (r = ~0.4; p ˂ 0.05) to fluoride and has a weak correction with the other parameters such as local temperature, altitude, water depth, EC, Ca, and Mg (r = -0.064 to +0.214; p ˂ 0.05). Concerning, the risk assessment through oral and dermal route exposure revealed that the consumers in most of the regions were at considerable risk, and the children were more vulnerable than the adults (THQ > 1). The study findings would help to take measures for safe water supply in the affected areas. PRACTITIONER POINTS: The calculated pooled concentration of fluoride was 2.1267 mg/L (1.650, 2.604) at 95% CI in groundwater of the study areas. Climatic conditions and lithological composition are the key controlling factors for groundwater fluoride contamination. Semi-arid and arid regions are significantly affected by fluoride rather than humid areas. Regarding fluorosis in selected regions, children (78%) are more vulnerable than adults (23%).