This is the planet we live on, we should take care of it like we would take care of a new pet. But instead we neglect it. You may think you don't do much to pollute the earth, but everyone does a little part of it. Trees are a sours of our oxygen but we cut them down to make room for houses and make paper. If you smock chances are you've left buds laying around somewhere and it takes them around ten years to decompose.  
CO2 (carbon dioxide) a green house gas is caused by combustion, the burning of fossil fuels like coal, oil and natural gases. The more CO2 in the air heats up the atmosphere which causes lots of problems like the melting of the Polar ice caps leading to the expanding of oceans into low areas.
SO2 (sulfur dioxide) is the cause of considerable environmental damage. It's created by sulfur or fuels containing sulfur are burned. 
CO (carbon monoxide) is formed by lack of oxygen in the combustion process, it can be deadly to inhale. 
Smog is a brownish yellow cloud of gases are caused by oxides of nitrogen in the air, when it is exposed to sunlight it reacts chemically with other gases. 
Air quality is something you really need to consider when using oil, gases, or coal to produce the energy to manufacture products. Just think of how unclean the air that you breath in is. 
Some of the deadliest forms of pollution is smog, sewage, radioactivity, mining and battery recycling. 
Even though somethings are caused by the environment we need to help clean it up. Submerged cars from the New Orleans Hurricane leaks oil and gas, which can seep into the ground water tainting lakes and poisoning wells. 
Just think of what all of this pollution does to us. 40 percent of deaths in the world are caused by a form of pollution. We all should give a hand in trying to clean up the world.