“…lepidolite, montmorillonite, kaolinite, pegmatite, mica, clays, villuanite, phosphorite, and some micas weathered from silicates, igneous, and sedimentary rocks, especially shale (Adimalla et al 2018a;Ayoob and Gupta 2006;Sudarshan 2017a, 2018a, b), and high rates of evaporation and low precipitation in arid and semiarid areas can also contribute to the fluoride enrichment Venkatayogi 2017, 2018;Subba Rao et al 2015). However, fluoride is an important element for human health which has certain limits for intake (Rao et al 2017;Ali et al 2016;Narsimha and Sudarshan 2017a, b). World Health Organization (WHO 1984) has fixed a safe limit for fluoride from 0.5 to 1.5 mg/L in drinking water.…”