If I were tasked with improving Bhutan, one of the things I would focus on is probably lead. 3/4 of Bhutanese children have elevated levels of lead in their blood.
https://www.unicef.org/bhutan/press-releases/national-blood-...
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https://www.unicef.org/bhutan/press-releases/national-blood-...
- Lead paint
- Water supply
- Lead in cookware
- Lead in spices, especially tumeric, where leaded dye is used to make it more yellow
- Industrial airborne emissions
Leaded gasoline used to be on that list but not anymore. Not sure about the specifics in Bhutan.
If you'd like to help prevent lead exposure in countries like Bhutan, the two charities I know about are Pure Earth and LEEP. Not sure if they have Bhutan programs.