Safe limit of fluorine in drinking water is:
a. Optimum concentration of fluorine in drinking water is 0.5-0.8 ppm (mg/lit.)
b. Deficiency of fluorine leads to dental caries while excess of fluorine causes dental and skeletal fluorosis.
This occurs in places with high levels of fluorine in water (3 – 5 mg/L)
However the Safe limit of Fluorine in drinking water in India is – 0.5 to 0.8 mg / dl.
Remember :- Dental Fluorosis if F2 above 1-2 mg/l
Skeletal Fluorosis if F2 3-6 mg/l
Crippling if Fluorosis above 10 mg/l
Intervention :- 1. Change the source of water
2. Nalgonda technique: Lime and alum are added to water followed by flocculation, sedimentation and filtration.