THAR in Sindh is experiencing an endemic fluorosis. A research carried out by PCSIR scientists shows that 78.77 per cent of the groundwater samples had fluoride values exceeding the limit of 1.5 mg/L proposed by the WHO.

Chemical analysis of 425 groundwater samples collected from Umarkot, Mithi, Chachro, Diplo and Nagarparkar sub-districts of Thar was carried out by the PCSIR for major ions as well as trace metals analyses.

The groundwater is concentrated with high fluoride along the north and northeastern side of the Thar desert especially in Chahchro and Umarkot areas, whereas localised enrichments have also been found in Mithi, Islamkot and Nagarparkar areas. The ground water of these areas is not potable. Fluoride-bearing granite rocks provide source of dissolved fluoride in ground water resources.

Thar lacks fresh water source except rainwater. The rain water collected in palar meets the requirements of the locals for only about three to four months of the year. After that the people are left with no option but to use the groundwater which is brackish, highly saline. Sweet water is found at great depths.

The rain water is collected in natural ditches and depressions known as Tal and Tarayoon and is locally called Palar. The precipitation rate in Thar is very little with a high rate of evaporation. The monsoon rains are very erratic--- between 100-200 mm a year. In certain areas, the rains are patchy leading to severe shortage.

Agriculture and animal husbandry are the main profession of the people, which are dependent on water supply. Agriculture in the area entirely depends on rainfall; however it is also carried out around dug wells in southern parts of Thar around Karoonjhar hills of Ngarparkar. Crops like chilies, onion, garlic, brinjal and wheat are grown here.

The desert soil is sandy and saline; in places sand dunes render large areas uncultivable. The constant dry wind erodes the loose topsoil of the fields, reducing its capacity still further. Water shortages, crop failures, debt and sickness create a vicious circle of poverty, disease and loss of productivity in the area.

Healthcare is a major issue in Thar. The marginalised sections of society suffer the most. Poverty and malnutrition compound the problems. In many families, women and girls fetch water for the family every day from a long distance, from a communal source. This takes hours, depriving them of profitable working time or education. Constant lifting and carrying of heavy water pots cause health problems, particularly among pregnant women.

The main crops grown in the area are millet, mung beans, bulgur wheat, chili and oilseed. These plants can tolerate dry conditions. However in severe drought conditions yield of even these crops falls drastically. Fresh fruits and vegetables are scarce. Successive years of low rainfall lead to scarcity of food and poverty.

Thar is highly population for a desert. However, settlements are spread over vast areas. In the absence of public water supply, when surface water dries out, the people are compelled to use groundwater which is brackish with high concentration of fluoride. The main source of fluorine is the minerals present in granite rocks through which the groundwater percolates under variable temperature conditions. When fluorine-rich minerals, present in these rocks and soils, come in contact with high alkaline groundwater they react to form fluoride through hydrolysis replacing hydroxyl (OH) ion.

Fluoride causes dental and skeletal fluorosis, osteoscalerosis, thyroid, and kidney problems when its concentration exceeds 1.5 mg/L in drinking water. The intake of excessive fluoride leads to chronic bone and joint deformations in skeletal fluorosis, for which early symptoms include sporadic pain and stiffness of joints and finally the spine, major joints and muscles damaging the nervous system.

Severe forms of fluorosis develop when the fluoride content of drinking water exceeds five to 10 mg/L. Fluorosis is irreversible and no remedy and treatment has so far been found except prevention by keeping fluoride intake within the safe limits.

Excess fluoride levels have been found in almost all parts of the study areas. Whereas in some areas, the local population is consuming water with fluoride concentration as high as 5-30 mg/L. Fluorosis problem is visible at various intensity levels in the Thar area and local peoples are suffering from dental fluorosis to skeletal fluorosis and non-skeletal manifestations to premature ageing.

In most of the rural areas, the alternative sources of water are not available and removal of excessive fluorine from drinking-water is difficult and expensive. Activated alumina defluoridation filter is used in some developed countries. They are relatively expensive, literature shows that the lowest price of a filter is Rs2,500 and these filter need frequent replacement. Reverse osmosis systems has shown considerable reduction in level of fluoride, however it is also very expensive for the poor community.

Nalgonda technology is a cost-effective defluoridation technique in which aluminium sulphate is added to precipitate fluoride in raw water and lime is added to obtain the appropriate alkalinity. The major concerns with this technique are that the doses of alum and lime are determined after assessing the fluoride levels and alkalinity of the water. Both these parameters changes with season, and, if the alum dose is not adjusted accordingly, there is a possibility of excess aluminium contamination in water. Raw bauxite is also used for defluoridation to treat water in high fluoride areas. Boiling water concentrates the fluoride rather than reducing it.

The situation in Thar region is alarming and need immediate remedial measures including better rainwater harvesting. Development of sweet groundwater and installation of defluoridation and desalination plants are other possible solutions.

The solutions suggested are costly and cannot by tried without financial assistance. The scientific literature on hydro-geological conditions of deserts is limited and almost negligible for Thar desert, which is the major hindrance in developing alternatives.

In order to mitigate the suffering of Tharies, the Sindh government should carry out exploration of deep-seated ground water in Thar with financial assistance from the federal and international donor agencies. The role of research organisations and local NGO is also very significant especially in creating awareness among the local people.

Developments like better education, healthcare and access to electricity will also help minimise the impact of flouorosis on the local population.