: a fog made heavier and darker by smoke and chemical fumes
also: a photochemical haze caused by the action of solar ultraviolet radiation on atmosphere polluted with hydrocarbons and oxides of nitrogen especially from automobile exhaust
the city's smog was once so bad that darkness often prevailed, even at noon
Recent Examples on the WebSeparate teams have also looked for technological signatures of alien civilizations, like smog on distant planets.WIRED, 11 Sep. 2022 In her first winter on the throne, a heavy, smothering smog descended on London—prompting the introduction of clean air acts that banned the burning of coal. Stephen Fidler, WSJ, 8 Sep. 2022 Additionally, state officials say the plan would cut smog-forming nitrogen oxides by more than 25% in 2037.Los Angeles Times, 25 Aug. 2022 The cow power also is used to run a feed mixing system at Bar 20, replacing diesel and reducing smog-forming emissions by 90%. Jeff Kart, Forbes, 18 Aug. 2022 According to the Times, Lovelock later used the device to confirm that smog was caused by industrial pollutants. Will Sullivan, Smithsonian Magazine, 17 Aug. 2022 Officials in Seattle and Portland on Tuesday issued air quality advisories expected to last through Saturday, warning that smog may reach levels that could be unhealthy for sensitive groups.CBS News, 29 July 2022 Transportation also accounts for 67% of emissions of nitrogen oxides, a component of smog. Mike Mavredakis, Hartford Courant, 26 July 2022 The film, which won the Mifa Annecy award at Ventana Sur in December 2021, turns on a group of children living in a city covered by a giant pink cloud of smog that turns adults into zombies. Lise Pedersen, Variety, 15 June 2022 See More