You may say: There is no problem with "my" air.

That's the joke, there is no "my" air. In one moment the air is in the engine of a car and in the other it is in your lung. Funny to think about.

You may still think there is no problem with the air "you" are breathing. That's relative mildly said.
  1. You can't be sure what are you breathing, many dangers are invisible and have no smell or taste (Carbon monoxide, Ozone, Radon...)
  2. You may be lucky and spend your life time in pristine environment (which is doubtful), but your kids, parents or loved-once don't 
  3. You will never know if the air you were breathing all your life will kill just die from one of the pollution induced sicknesses, 10 years earlier or a just sudden but it will harm you for sure.
Human induced air polution has been around from the moment humanoid learned how to exploit fire. There was however change in recent history...
You have to look on these factors:
1. Time of exposure
2. Kind of airborn polutant
3. Resistance
4. Life expectancy

Pre-industrial Post-industrial
→Limited to certain areas and time however also  significant. Burning wood indoors to cook. →A city-dweller is exposed 24/7 if not leaving city or the weather conditions dilute the pollution.
→Burning wood, natural oils, charcoal and dung. Regular mineral dust and dirt. →Nano sized artificial particles, Poisonous gases like NOx, Hydrocarbon combustibles, artificial dust
→Natural selection and rather merciless natural environment made sure that only the strongest specimens survived. →Current advances in medicine and technology allows the survival of specimens that would naturally not survive without.
→Life expectancy was much lower. Ranged from the early 40’s to the early 60,’s There was little  time to develop any pollution induced sickness to any significant stage. →Current technology advancements allow humans to reach higher lifespans. It is expected human will soon reach regularly 100 years if 'environmental conditions are favorable'. Plenty of time to develop dementia.

There always be something in the air, depends only what kind of stuff it is and for how long will you let enter it your body. Also if the body is elderly or a young one the bets are the impact will be significantly worse that for an adult. Particularly the air pollution effects on children are worrisome.