.

Several clinical studies and researches have been conducted to find out the impact
of fluoride concentration in drinking water on human health.

It is a well-known fact that fluoride (F⁻) at low concentration (<0.5 mg/L) induces dental caries, which enhances the risk of tooth decay^1,2. On the other hand, ingestion of excessive fluoride imparts adverse effect on human health³. It is a well-established fact that elevated F⁻ concentration in drinking water is linked to dental and skeletal fluorosis depending on the amount of intake and duration of exposure^4,5. Excessive fluoride can also damage structure, function and metabolism of soft tissues such as kidney, liver, lung and testicles^6,7,8,9. Various clinical studies suggest that ingestion of excessive fluoride promotes physiological dysfunctions like mutagenesis, immune suppression, carcinogenesis and growth retardation^3,10. At times, higher concentrations of fluoride can also promote neuro-toxicological effects^11,12. Several studies indicate that exposure of excessive fluoride does impart the vulnerable effect on the mental ability of the children. Choi et al.¹³ suggests that children with exposure to high fluoride were found with significantly lower IQ compared to children residing in low fluoride areas¹³.
Fluoride easily reaches the placenta, and exposure to fluoride may permanently harm the foetus¹⁴. In the human body, the thyroid gland is the most sensitive tissue to the fluoride and exposure to fluoride raises TSH (thyroid stimulating hormone) concentration and decreases T₃ and T₄ concentration, thereby resulting in hypothyroidism^15,16. In several studies, it has been pointed out that prolonged exposure of fluoride from drinking water does develop insulin resistance in human beings^17,18. Excessive consumption of fluoride ultimately leads to hyperglycemia and impaired glucose tolerance^19,20. While some studies showed that exposure to high fluoride may induce adverse impact on human reproductive system, leading to infertility problems and low body weight of neonates^3,21,22. Osteosarcoma is known as a potential cancer target site due to fluoride deposition in bone^23,24. Cohn (1992) observed that the association of fluoride in public water with an increased incidence of osteosarcoma in young males²⁵.