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.
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.
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.
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.
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Fluoride is often called a two-edge sword – in small dosages,
it has remarkable influence on the dental system by inhibiting dental
carries, while in higher dosages causes dental and skeletal
fluorosis. When present in concentration of
0.8-1.0 mg/L, fluoride is beneficial for calcification of dental enamel
especially for the children below 8 years of age. At higher concentrations
(1.5-2.0 mg F/L), fluoride effects adversely and leads to dental
fluorosis. At still higher concentration, (3-6
mg F/L) skeletal fluorosis occurs. The disease
affects the bone and ligaments. Intakes of 20-40 mg F/day over long period
have resulted in crippling skeletal fluorosis.
High concentrations of fluoride in ground water are common in
some of the semi-arid areas of Rajasthan, southern Punjab, Gujarat,
Karnataka, Tamil Nadu, Madhya Pradesh, and
southern Haryana. Several areas of Andhra
Pradesh have high concentrations of fluoride in ground water (exceeding 5
mg/l). There are a number of cases of dental and skeletal
fluorosis in these areas. In several parts of
Karnataka, Tamil Nadu, U.P., and other areas,
fluoride concentrations of groundwater are more than the permissible level
of 1.5 mg/l. An extensive survey of the community water supplies has shown
that around 25 million people in rural areas consume water with fluoride
content more than this limit. Various authorities have given permissible
limits for fluoride content in drinking water.
Concentrations of fluoride in drinking water in different parts of the
country varies from 0.5 to 50 mg/L.
Permissible limit
of fluoride in drinking water prescribed by various organizations
Fluoride contaminated
ground water is creating health problems in India. Nearly 90 million people
including 6 million children in the country in 200 districts in 15 states
are affected with dental, skeletal and/or non-skeletal
fluorosis. The extent of fluoride contamination in ground water
varies from 1.0 to 48 mg/l. The fluoride affected states are: Andhra
Pradesh, Bihar, Delhi, Gujarat, Haryana,
Jammu and Kashmir, Karnataka, Kerala, Madhya Pradesh,
Maharashtra, Orissa, Punjab, Rajasthan, Tamil
Nadu, and Uttar Pradesh,
In Rajasthan, in the absence of perennial
rivers, surface and canal systems, ground water remains
the main source of drinking water for about 95% population. Ground water of
18 districts contains high fluoride (2 to 20 mg/l) affecting approx. 3
million people. Studies have revealed that three million people in the state
are consuming water with excess fluoride. Rajasthan has to depend on ground
water resources to a greater extent and in arid in semi-arid
areas, the ground water is the only water
resource for drinking as well as agricultural purposes. According to the
survey of states for drinking water supply in rural habitation conducted by
the Rajiv Gandhi Drinking Water Mission, 9,741
villages and 6,819 habitations have fluoride content more than 1.5 mg/l in
ground water.
In Tamil Nadu,
fluoride monitoring is carried out at 1286 observation wells by TWAD Board
throughout the State twice in a year – during pre-monsoon and post monsoon
periods. About 121 blocks in 19 districts are found to have high fluoride
concentration in ground water.
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