It has everything to do with the economic costs. There is no other reason other than perceived threat to human life that drives that cost. How is that not obvio

It has everything to do with the economic costs. There is no other reason other than perceived threat to human life that drives that cost. How is that not obvious ? That paper, and others like it, demonstrates that radiation is much more benign than generally believed, and that level of resources spent on threads that don't exists, especially in comparison with others, like drink a can of soda a day, or living in a city, is not justifiable.