Guardian: During the 1950s when London was enveloped in pea-souper smogs, Los Angeles was struggling with a quite different air pollution problem. The London smogs were caused by coal smoke becoming trapped in the city in cold still conditions, whereas Los Angeles smogs were caused by traffic pollutants reacting in strong sunshine to produce ozone at ground-level. Ozone is very reactive and these smogs were first characterised because of their damage to rubber and crops before human health effects were fully...