This ozone which is a main ingredient in urban smog ozone Environmental Protection Agency hugely harmful to human health which is a main ingredient in urban smog good up high, bad nearby which is a main ingredient in urban smog major sources of “bad” ozone By definition ccording to the EPA, AirNow: Ozone - Good Up High, Bad Nearby What is Ozone? cfpub.epa.gov/airnow/index.cfm?action=gooduphigh.index Ground level ozone good up high, bad nearby