It can be disheartening. I don't know that there's much strong evidence yet that air polluted with synthetic particles leads to bad health effects, but I do kno

It can be disheartening. I don't know that there's much strong evidence yet that air polluted with synthetic particles leads to bad health effects, but I do know that are lungs have been subjected to things in the last 100 years that they hadn't encountered in the previous 300 million.