With the recent realisation that mercury can transform itself in the stratosphere, then pollute the atmosphere below, we are finally coming to terms with the enormous extent to which we have (along with other sources) polluted ourselves out of house and home-planet. The extent of air pollution of course combines with terrestrial and aquatic pollutions, and even on to solar system and universal pollution. Of course it can't continue. If we ourselves are to stop it, government education would and could help a little.
The two main gases in our air are not pollutants at this time. Others are in small quantities and pose little threat until they upset ecosystems. The prime candidates are carbon dioxide, ozone and methane, although the latter is not sourced by humans, but instead lies beneath oceans as a rather benign, but massive threat. The many polluting "colleagues" of these gases are present in lesser quantities. We all know that some of them are lethal to us and other organisms. Carbon monoxide poisoning (mentioned later in car emissions) and the gases that governments have licensed so that we could harm each other are major threats despite their small volumes.
Global warming of course is the main threat from CO2 build-up, as well as methane and several others. Gases such as these and even nitrogen can kill oxygen breathers by blanketing a low-lying area (such as a camp site). Creating world-wide nuisance however is their claim to present notoriety, despite several coal-burning countries' efforts to pour scorn on their effects. It is however accepted, both scientifically and rationally, that, whatever your reigning ruler might say, global warming is just about to cause a greater menace than we have faced for generations
Read more at http://www.earthtimes.org/encyclopaedia/environmental-issues/air-pollution/#2sEZ371WSvhzy73b.99