Does burning medical waste—including impurities like blood—for money fall under selling impure substances? Are the earnings of such a company lawful, and is it permissible to work for it?

What was mentioned regarding hiring someone to transport and dispose of impurity is not selling the impurity. This is permissible, and even necessary today, due to the harm that results from not destroying these waste products. It is stated in al-Mughni that it is permissible to carry impurity to pour it out, and a dead animal to dispose of it, and to hire someone for the purpose of removing waste.