FLUORIDE IN GROUNDWATER IN EASTERN HILL TRACTS OF BANGLADESH

Bangladesh comprises of four geo-morphological regions, namely tableland, flood plain, delta including coastal areas and hill tracts in the eastern part of the country. All the regions except the hill tracts in the eastern part of Bangladesh are affected by arsenic contamination in groundwater. It is believed that flood plains and part of table lands containing Holocene sediments are rich in arsenic bearing minerals while the hill tracts containing Pliocene sandstone are not rich in arsenic minerals. While the flood plain groundwater has high arsenic (~50 to several hundred ppb), the groundwater in hill tracts area are relatively free from geogenic arsenic. However, our recent study involving analysis of about 150 groundwater samples from hill tracts area revealed that 20 percent of samples have fluoride (F^-) levels much higher than the World Health Organization (WHO) guideline value. Fluoride has not been identified at significant level in groundwater from other areas of Bangladesh. Whether the fluoride level in groundwater becomes a public health issue in Bangladesh remains to be seen. But the current finding calls for strict monitoring of fluoride and other ions in groundwater in Bangladesh. Fluoride and several other anion data in groundwater from Bangladesh will be presented and potential health risks will be discussed in the paper.