The Tab Delimited data should be the easiest to work with. OzData Library of data sets and associated stories. It is intended as a resource for teachers of statistics. Very nice site. A whole page devoted to air quality.
Site is pretty straightforward.
Most of the data is on emissions, concentrations, etc. There's a large collection of data at this site, ranging from country profiles to the highest mountains in the world. Once in the editor remember to take out the spaces. World Populations Total populations for countries around the world. The data is ready to go so you shouldn't have a problem.