HYDERABAD, June 7: High levels of fluoride in groundwater in Thar cause fluorosis among people, a condition which is characterised by discoloured, blackened, mottled or chalky-white teeth, and can lead to severe bone deformations, thyroid and kidney problems if its level exceeds permissible limits, says a research study.

Tahir Rafique, senior scientific officer in Pakistan Council of Scientific and Industrial Research (PCSIR), Karachi, who conducted the research, said that the study confirmed high level of fluoride in Thar groundwater.

He said in his research on “Occurrence, Distribution and Origin of Fluoride-rich Groundwater in the Thar desert” at a seminar on Friday that the research found that 78.77 per cent of the analysed groundwater samples had fluoride values exceeding the limit of 1.5mg/L prescribed by WHO.

He pointed out that distribution patterns showed that high fluoride groundwater was concentrated along the north and north-eastern side of Thar especially in Chhachhro and Umerkot areas, whereas localised enrichments had also been investigated in Mithi, Islamkot and Nagarparkar areas.

He said that fluoride bearing granite rocks provided source of dissolved fluoride in groundwater resources. Elevated fluoride levels had been investigated in almost all parts of the area whereas local population was consuming water with fluoride concentration as high as 5-30mg/L.

The scholar said that fluoride was considered beneficial to human health if taken in limited quantity (0.5 to 1.5mg/L) and it caused dental and skeletal fluorosis, osteoscalerosis, thyroid, and kidney problems if its concentration exceeds 1.5mg/L in drinking water.

He said that dental fluorosis was characterised by discoloured, blackened, mottled or chalky-white teeth which were clear indication of overexposure to fluoride during childhood at the age of teeth development.

He said that chronic intake of excessive fluoride led to severe and permanent bone and joint deformations in skeletal fluorosis, for which early symptoms included sporadic pain and stiffness of joints and finally the spine, major joints and muscles and nervous system were damaged.

He said that severe forms of fluorosis typically developed only when the fluoride concentration of drinking water was greater than 5 to 10mg/L. Symptoms of the disease could develop with regular ingestion of water containing fluoride concentrations as low as 1 to 2mg/L, he added.

Dental or skeletal, fluorosis was irreversible and had no remedy and treatment and its only remedy was by keeping fluoride intake within safe limits, he said.

Mr Rafique said that according to WHO, there were more than 29 developed and developing nations that were endemic for fluorosis across the globe and added that many of these areas were arid where alternative sources of water were not available.

He said that presence of fluoride in groundwater, exceeding permissible limits, was a critical matter of concern from public health point of view. According to his research incidence of fluoride in groundwater was mainly a natural phenomenon, basically influenced by local and regional geological conditions, he said.