Most people associate ozone with either the beleaguered upper atmospheric filter layer that protects us from solar radiation or with ground level air pollution.
Ozone is indeed present in smog, because certain processes that create pollution also produce ozone.
As well, sunlight shining on industrial and automotive pollution makes oxygen atoms hive off from pollutant molecules, leaving baddies like nitrous oxide, nitric acid, sulphur dioxide and carbon monoxide. Meanwhile, the freed oxygen atoms bond with free oxygen in the air to form ozone. The highly reactive ozone, in turn, recombines with these same pollutants and neutralizes them by breaking them down into water, carbon dioxide, nitrogen, sulphur and oxygen. Consequently, increased pollution results in high ozone levels, but ozone specifically, is not the culprit. Because ozone levels have a direct relationship to levels of chemical pollutants found in smog, it is used as an index to monitor outdoor air pollution.