Fertilization with super phosphates (ATSDR, p146).”
Fluoridation of low fluoride concentration water.
Release of fluorine in water during weathering of rocks
Abundance of fluorine in the rocks.
Controlled by solubility product.
For fluorite, CaF 2 =Ca ++ +2F −
K fluorite =(Ca ++ ).(F − ) 2 =10 -10.57 at 25 ◦ c.
inversely proportional to Ca ++ concentration.
2Na + ->Ca ++ increases fluoride concentration.
Longtime water-rock interaction.
Positive correlation with temp & depth
& negative correlation with hardness of water.
High in neutral to alkaline water (pH 7-9).
Fluoride enters the human body by ingestion (food and water), and in extreme cases through the skin.
The maximum permissible limit of Fluoride content in groundwater is 1.5 mg/l (WHO, 1994). For the Indian sub-continent, the desirable limit of ‘F’ is 0.6 mg/l and maximum permissible limit is 1.2 mg/l (ISI, 1983).
Low concentration causes dental caries
High concentration promotes dental fluorosis, skeletal fluorosis, crippling fluorosis. Ca 10 (PO 4 ) 6 (OH) 2 ->Ca 10 (PO 4 ) 6 (F) 2
Non skeletal health hazards
Destruction of stomach & intestinal lining (mucosa). F − +HCl =HF+Cl −
High concentration causes Nervousness & Depression, Muscle Weakness & stiffness.
Early destruction of RBCs causes anemia.
soft tissues like ligaments, blood vessels tend to harden and calcify and the blood vessels may be blocked.
Excessive fluoride intake since early childhood would reduce mental work capacity (MWC) (case study).
May causes cancer (less clearly defined).
Remediation of high fluoride water
Identifying the source and mapping of affected area
Defluoridation of water containing excessive fluoride concentration.
Promote & support research & development on removal of excessive fluoride.
Develop suitable local guideline and standards of fluoride in drinking water.
Develop & survey alternative source of drinking water, such as rain water.
Detailed study on the vertical variation of the fluoride concentration and identify aquifers with less fluoride concentration–sealing aquifers with high fluoride concentrations
Edmunds M.,Smedley p.(2004);Fluoride in natural waters, in Selinus O., Alloway B.J. , Centeno J.A. , Finkelman R.B. , Fuge R. , Lindh U. , Smedley P. (eds) Medical geology; Elsevier; pp:812.