I would like to endorse the comments by Dr Chakraborti [at
http://groups.yahoo.com/group/arsenic-source/message/169 ] that fluoride is not
a
major issue in the Bengal Delta, and is not coincident with arsenic
contamination.

However, fluoride is not absent from the delta. First, the BGS survey of
northeast Bangladesh in 1992 did find one or two exceedances of the
WHO drinking water guideline.

Secondly, in some of the deeper aquifers of the coastal zone, where ion exchange
processes result in very low calcium concentrations, the few data analysed by
DPHE-Danida suggest enrichment in fluoride, and hence a possible fluorite
solubility control. Although these analyses do not exceed drinking water
standards, other surveys have neglected this issue and there are too few
analyses to give confidence at this time.

Peter Ravenscroft
Hydrogeologist