Most developing countries require flour to be fortified with folate to prevent severe birth defects. Why doesn’t Europe?
(Note: this intervention is probably not cost-competitive with GiveWell’s top charities but is a very easy public health win in European countries, and is very cost-effective given the current marginal public health intervention in rich countries.)
I found this a clear explanation of the costs and benefits—thanks for writing it up!
A similar issue: lack of iodization in Europe, the region where children have the highest rates of low iodine. https://www.who.int/publications/i/item/9789241593960
A less important but still meaningful win in the US and other places with existing iodization might be extending it to salt in processed food.