WHO Air quality guidelines and city performance

If you are reading this in a big city, the air you are breathing may be doing you harm. Though over 50% of the world’s population now live in urban areas, only 2% of the global urban population lives with acceptable concentrations of particulate matter, or PM, which can cause breathing and respiratory diseases, cancer and premature death. Children, older persons, and people with lung ailments such as asthma or chronic lung disease are especially vulnerable to the effects of PM. See full Article.