A review of groundwater fluoride contamination in Pakistan and an assessment of the risk of fluorosis

The fluoride ion (F) is an important anion and a major pollutant of groundwater, affecting millions of people around the globe. Groundwater contaminated with F is the main source of F exposure for the development of fluorosis in humans.Various natural and anthropogenic activities are responsible for the F contamination of groundwater sources. At concentrations greater than the permissible limits, F has adverse impacts on human health with various manifestations of fluorosis, especially in children. In Pakistan, the F content in groundwater sources varies considerably from the World Health Organization (WHO) and national standard value of 1.5 mg/L. In addition to the climatic conditions of an area, the factors controlling the F concentration in groundwater sources include the weathering and leaching of F-bearing minerals and rocks. F contamination of groundwater sources in Pakistan is widespread and is often intense with the highest mean concentration being 28.24 mg/L in the Chachro and Diplo sub-districts in Tharparkar. The lowest value was 0.29 mg/L in Peshawar. High mean values were found for the Estimated Daily Intake (EDI) and the Hazard Index (HI) [HI=EDI_water/RfD] in both children and adults (EDI: 0.406 mg and 0.098 F/kg bw/day; HI: 6.77 and 1.638, for children and adults, respectively). Children in Pakistan are at a higher risk than adults for developing fluorosis due to F contamination of ground water. The determination of the F status in all the drinking water sources in Pakistan is urgently required.