Stratum corneum is the answer
Factories which leaves out smokes (carbon dioxide and carbon monoxide), carbon dioxide mix up with sulfur and acid rain is created which damages out skin permanently and carbon monoxide which very harmful and since they are minute particle they can pass inside our body through nose and takes out oxygen from our body, the only thing left in our body will be carbon which leads to death.
It has the ability to bind itself to small amounts of acid in the blood, which helps with removing that acid before the blood’s pH changes