The problem is that (a) you can't prove something safe, you can merely fail to find harm; and (b) literally everything is a chemical, often it already exists in

The problem is that (a) you can't prove something safe, you can merely fail to find harm; and (b) literally everything is a chemical, often it already exists in some form and is used for some purposes, and we reuse it for something else at a larger scale... at large enough scales basically anything is dangerous.