How can human health be affected by changes in air quality

Human health can be affected by changes in air quality mainly because if the air is bad they will have various health defects. For example with some of the cities in China much of the air there is polluted. Thus human health may be affected by added stress as well as breathing in polluted air which will cause side effects. 

All in all human health is affected by changes in air quality because air is what humanity breaths to survive. If in some way this air were to be polluted we would suffer from decreased health due to a circulation of fossil fuels in our atmosphere. 

How humans' health could be effected by the changes in air quality is that majority of the human population needs to have good air quality to be able to have a healthy development either in the open world or in the mother's stomach.