A London policeman ... trapping the smog for days, causing "pea-soup" conditions where the smog appeared yellow or green due to sulphur pollutants. A weather map from Dec. 4, 1952 shows a strong ...

London's poor air quality ... most of the country and turned to smog in the city on Jan. 1, 1962. (Photo by Keystone/Getty Images) A weather map from Dec. 4, 1952 shows a strong high pressure ...

A London policeman wearing a mask for protection against the thick fog which hit most of the country and turned to smog in the city on Jan. 1, 1962. (Photo by Keystone/Getty Images) A weather map from ...