Treehugger has just posted a series of photographs from the Smoke Control Lantern Slide Collection, ca. 1940-1950, from the Archives Service Center at the University of Pittsburgh. See a selection of the photographs below. They demonstrate how it is not just modern-day cities such as Beijing, Mexico City, and Rio de Janeiro that experience severe air pollution. Many cities that have relatively clear skies today such as Chicago, London, and Berlin also used to have dangerous smogs but these were tackled with curbs on emissions and stricter controls on air quality. Let us hope the industrialising nations manage to implement their own restrictions soon. These beautiful yet terrifying images are taken from war-time Chicago. The air quality is much the same as that LMV saw in the Beijing of today.