Well water usually contains high levels of minerals, including fluoride.
I'm curious whether fluoride levels were also checked in areas where high
levels of arsenic were found. Is there any relationship here? My searches of
the discussion groups have turned up very little on this subject.

In India fluoride contamination from well water is a big problem. I wonder
if fluoride could be contributing to the ill health effects caused by the
arsenic. For example, skin rashes attributed to arsenic could also be
caused or made more serious by fluoride. A couple years ago a scientific
conference in China focused specifically on the problems of arsenic and
fluoride.