Smog Is Gross, But it Makes For Oddly Beautiful Pictures

In the late 19th- and early 20th-century London, the newly industrial metropolis contended with an issue known as "pea soup fog." The city's factories, foundries, and power plants were belching nitrogen oxides, sulfur oxides, smoke, and particulate matter into the air, forming a layer of visible pollution that typically quippy British residents named after a particularly opaque soup. We know it as the portmanteau of "smoke" and "fog": "smog." The modern stuff, the stuff that hovers famously over Los Angeles, is a more advanced strain. There, and more extremely in cities like Delhi and Beijing, car fumes percolate in the atmosphere and react with sunlight, creating secondary pollutants that thicken the air. (Ozone is one, famous secondary pollutant.) A multitude of cars and sun produces more than just dark tans.