With smoke from brush fires clouding the skies over much of southeastern Australia, it's worth recalling the Great Smog of 1952. It was on December 9, 1952, that the Great Smog finally lifted in London. An educational site maintained by the Met Office in London states:
The smoke-laden fog that shrouded the capital from Friday 5 December to Tuesday 9 December 1952 brought premature death to thousands and inconvenience to millions. An estimated 4,000 people died because of it, and cattle at Smithfield, were, the press reported, asphyxiated. Road, rail and air transport were almost brought to a standstill and a performance at the Sadler's Wells Theatre had to be suspended when fog in the auditorium made conditions intolerable for the audience and performers.
The spike in deaths due to the Great Smog was noticed only three weeks later when official mortality figures were published. The awareness that several thousand people had died for reasons directly related to air pollution, however, made a difference in public policy. Eric Nagourney of the New York Times writes,
The Great Smog is considered a turning point in environmental history. Although there had been other episodes where air pollution was held responsible for a spike in deaths--notably in the Meuse Valley in Belgium in 1930, and in Donora, Pa., in 1948--the numbers were much lower than those in London. In the aftermath, British officials passed laws banning the emission of black smoke and requiring industry to switch to cleaner-burning fuels.
These laws gradually produced dramatic reductions in some of the more unhealthy components of London's famous fog.