This photo appears in the United Nations Environmental Programme youth magazine Tunza, vol 4, issue 4, illustrating a short piece on the Golden Ratio. Photo Credit: Stu Horvath

smog alert noun

a warning that is issued when there is a particularly high concentration of pollutants in the air. Most Smog Advisories are issued in the summer, when ground level ozone levels are expected to exceed the current National Ambient Air Quality Objective of 82 parts per billion, thereby allowing the public to modify their daily plans accordingly, as they do for ultraviolet radiation forecasts.