Fluoride contamination of groundwater

Ingestion of low levels of fluoride compounds is beneficial to the body and prevents dental caries. Some of us can perhaps still remember advertisements of fluoridated toothpastes. But long term ingestion of excess fluoride can be harmful to the body and cause a condition known as fluorosis that affects teeth and bones.
In the recent past there has been excessive dependence on groundwater to meet potable water needs. If groundwater passes through fluoride rich rocks, it dissolves the fluoride and the water consequently can have more than an acceptable level of fluoride. Water used for drinking should not have fluoride in excess of 1.0 mg/l.
According to the Department of Drinking Water Supply, out of 593 districts from which data is available, water in 203 districts has shown high fluoride (Susheela A K, 2001). As seen from the map below, almost all states in India have districts where groundwater contains excess levels of fluoride.
Fluoride map
Dental and skeletal fluorosis
Moderate amounts of fluoride ingestion can cause dental fluorosis, which is characterized by staining and pitting of the teeth. In more severe cases all the enamel may be damaged.
Dental Fluorosis
Chronic high-level exposure to fluoride can lead to skeletal fluorosis. In skeletal fluorosis, fluoride accumulates in the bone progressively over many years. The early symptoms of skeletal fluorosis include stiffness and pain in the joints. In severe cases, the bone structure may change and ligaments may calcify, with resulting impairment of muscles and pain. 
Skeletal Fluorosis
There is no medicine for fluorosis, but treatment systems that can regulate the amount of fluoride in water are available. The control of drinking-water quality is therefore critical in preventing fluorosis. In all fluoride affected areas it is advised that rainwater harvesting is done to recharge the groundwater source that shows high fluoride levels.
In places where fluoride levels are between 1.5 to 2 mg/l, some nutritional interventions can help. In these places it is advised to eat more of foods that are rich in iron, calcium and Vitamin C. The use of black salt (kalanamak) and products containing it, as well as the use of fluoridated toothpastes should be avoided in these areas.

Nalgonda District in Andhra Pradesh is said to have the highest concentration of people affected by fluorosis. Nearly 500 villages in the district are gripped by fluorosis resulting in twenty thousand fluorosis victims in the district. According to the World Health Organization, maximum level of fluoride in water should be 1 ppm or 1 mg/l. In Nalgonda, the water contains up to 10 ppm of fluoride. Many adults and even young children have been irreversibly affected by skeletal fluorosis in this district.
  • www.who.int
  • Mid-term appraisal of the eleventh five year plan, Planning Commission