Summer smog is an occasional problem confined to the Melbourne metropolitan area and surrounding coastline. Smog is mostlty made up of ozone, which can affect people with respiratory problems such as asthma. Monitoring over 26 years has shown a significant improvement, because of tighter controls on vehicle emissions. However, recent bushfires contributed to higher smog levels in 2003 and 2006, as bushfire smoke, like motor vehicle emissions, can convert into smog under certain conditions. You can help to reduce smog pollution by minimising the use of your car on hot days in summer, and keeping it well tuned to reduce emissions of pollutants.