<Which reminds me that according to NPR 18-24M people in Bangladesh are
exposed
to drinking shallow-well water with natural occurring arsenic in it>

Which brings to mind the story of a remote rural area somewhere in the US,
where the ground water was contaminated by slowly increasing amounts of
arsenic. The local residents started to show symptoms, including
jaundice-like coloration, but remained healthy. They knew they had a serious
problem when a visitor drank the water and died. Just goes to show what you
can get used to, when it hits you incrementally.