Pollutants are all the dead things around us that should not get into your body because they interfere with its work. As long as they don't penetrate your tissues, they won't interfere, like plastic eyeglasses and clothing. But if they are invasive, your body must fight to remove them.
Pollutants can invade your body via the air you breath, the foods and beverages you eat, and the products you put on your skin.
The biggest tragedy is not recognizing when a pollutant is harming you.
Two people can use the same face cream. One develops a rash, the other does not. The one who did not assumes the cream is not harmful to them...that they are like a bank vault, impregnable to that product. A better assumption is that the face cream is somewhat toxic, as evidenced by the rash that can develop, and they escaped the rash only because they had a stronger immune system. The immune system is like money, paid out of the bank vault, for every toxic invasion. When the money is gone, the bank (your health) fails.