There are many forms of air pollution. There is no doubt that air pollution is not healthy. The uncertainty is at what level is it an acceptable risk. The one of concern in this study is the finest of particulate matter. - See more at: http://www.enn.com/pollution/article/45621#sthash.OREPIZA3.dpufThere are many forms of air pollution. There is no doubt that air pollution is not healthy. The uncertainty is at what level is it an acceptable risk. The one of concern in this study is the finest of particulate matter.