You spend one third of your life asleep. But you spend your entire life breathing. Sure, there may be a minute here and there where you stop breathing for swimming-related reasons, but if you stop breathing, the jig is up. Game over, man. What you breathe should be as important as where you sleep. Your lungs are one of those "critical" organs and should be treated thusly. And if the air pollutants can find anything to harm in the lungs, they can move right into the bloodstream and have access to every organ.
The best way to defeat an enemy is to know it. The EPA has a list of the most common indoor air pollutants. Here?s a breakdown of that list.