What is flouride?

Fluoride is one of the chemical compounds that are present in the water and soil. These fluorides are organic and inorganic compounds containing the element fluorine.

How does fluoride enter the water?
Fluoride gets mixed with water when leaching from rocks takes place and these rocks are in contact with water. In ground water, fluoride is present in traces in the form of calcium and/or magnesium fluoride.

Fluoride levels in water
The maximum permissible limit of fluoride quantity in drinking water is 1.5 mg/l. Fluoride level above this poses serious health risks to humans and causes irreversible damage to plants. Many states in India such as Andhra Pradesh, Tamil Nadu, Karnataka, Gujarat, Rajasthan, Punjab, Haryana, Bihar and Kerala have high quantities of fluoride in drinking water.

A high concentration of 5.2 mg/l has been reported in Medak district of Andhra Pradesh, 15 mg/l in Nawabganj block in Uttar Pradesh and 18 mg/l in Jaipur, Rajasthan.

High quantities of fluoride enter the shallow zone groundwater due to the geochemical disposition in the vicinity of the groundwater extraction structures. The toxicity of fluoride is also influenced by high ambient temperature, alkalinity, calcium and magnesium contents in the drinking water.

Fluorosis worldwide

Fluoride in water is mostly of geological origin. Waters with high levels of fluoride content are mostly found at the foot of high mountains and in areas where the sea has made geological deposits.

Known fluoride belts on land include: one that stretches from Syria through Jordan, Egypt, Libya, Algeria, Sudan and Kenya, and another that stretches from Turkey through Iraq, Iran, Afghanistan, India, northern Thailand and China. There are similar belts in the Americas and Japan. In these areas Fluorosis has been reported.

Fluorosis in India

Fluorosis is endemic in large areas of India, mostly rural because more than 90% of the rural population in India uses ground water for domestic use, predominantly for drinking and cooking.

Nearly 65 million people in 160 districts and 17 states across India drink water contaminated by excess fluoride (over 1.5ppm). Rajasthan in India has fluoride levels as high as 44 mg/l in the ground water which is used for domestic purposes in several districts.

Geochemistry of fluoride in Karnataka

Karnataka contains high levels of fluoride in India. The sedimentary formation of bhima group is constituted by conglomerates, sandstones, shales and limestones. The formation in the Southern regions is subjected to tectonic disturbances and hence traversed by shear and fractured zones. These zones are occupied by pegmatite veins filled with fluorite-associated minerals.

The alluvium is of recent age and is limited to certain river courses draining the districts. It consists of unconsolidated sediments as gravel, sand, clay, silt and pebbles. These sediments contribute to the water fluoride content.