Beware flurosis is zeroing in on you
as we approach the new millennium, a glass of clean, uncontaminated water seems to be a luxury, that even money cannot buy. Newspapers are awash daily with reports of fluoride-contaminated water sources. Sadly, long-term constructive policies are yet to see the light of day. Occasional studies and certain discrete temporary solutions by local governments is all that is dished out to hapless citizens. This leaves many at the doorstep of a fatal disease, fluorosis.
Danger lurks in the ground beneath Fluoride, if present in excess in groundwater, causes fluorosis. If the fluoride concentration is below 0.5 milligrams per litre (mg,l) or above 1.5 mg/l litre in drinking water, it is considered harmful. The disease manifests itself through discolouring and mottling of teeth and in an advanced stage damages bones and joints. Children are particularly susceptible to this disease and the damage is medically irreversible.
In India almost 60-65 million people drink fluoride-contaminated groundwater. The number affected by fluorosis is estimated at 2.5-3 million. Studies show that the concentration of fluorides is five times higher in granite than in basalt rock areas. Similarly, shale has a higher concentration than sandstones and limestones.
On the other hand, researches have also shown that the concentration of fluoride in groundwater is not dependent only on the concentration in the source rocks. It is also enriched over a certain period due to climatic conditions. Other researches have shown that a high concentration of fluoride is correlated with high rate of annual evaporation. A comparison shows that although the evaporation rate in the south central part of peninsular India is comparable to that in north-western India, the fluoride levels in the former are somewhat lower than in western India. This is probably because the rainfall in south central India is marginally higher.
A comparison between the distribution of fluoride concentration in India and the total dissolved solids in groundwater, shows an interesting correlation. The Central Ground Water Board ( cgwb ) has prepared a contour map of electrical conductivity in areas with shallow groundwater. The conductivity values are proportional to the concentration of total dissolved solids. Salinity increases with higher values of electrical conductivity. A study of the map shows that the high values are present in areas with greater fluoride levels.
Wanted: a cohesive strategy The present strategies of various state governments for tackling scarcity, excess fluoride and brackishness or salinity in water are invariably localised, expensive and time-consuming. Local administrations tackle water scarcity by identifying new and deeper aquifers or supplying water through tankers and pipelines brought from distant sources of surface water. While the first and second solutions are not sustainable, the third is expensive. Moreover, there is also the question of a long gestation period and it is not feasible in the hilly areas or arid regions like the Thar desert, where there are no perennial sources of surface water.
Salinity or excessive fluoride is tackled through expensive methods like installation of desalination or de-fluoridation plants at the source of the water. These can reduce the salt or fluoride content to permissible levels. Various chemical processes and plants of different capacities have been installed at many locations in the country over the past two decades. However, studies and discussions have shown that these approaches are neither socially acceptable nor sustainable.
Many plants, even after being adapted to local needs by scientists, are lying defunct due to lack of spares, chemicals for treating the water, or neglect.
The present scenario calls for refreshing and holistic approaches like water harvesting and conservation of water in the watershed regions, to tackle the three problems