In October 1948, smog filled the Monongahahela Valley in western Pennsylvania. As noted in a previous column, damaging oxides of nitrogen, halogen acids, zinc and lead claimed 20 lives with 2,000 afflicted with respiratory disorders. Fog and industrial pollution created the worst episode of smog in London from Jan. 5-9, 1952. Stagnant air over the four-day period found sulfur dioxide and particulate concentrations reaching deadly levels. The smog was so thick that Londoners couldn’t see their hands with outstretched arms, traffic stopped and only the blind could navigate. Close to 100,000 residents became sick as deaths from bronchitis and influenza increased 10 times leaving 4,000 dead. Four years later, Parliament enacted the British Clean Air Bill as the burning of bituminous coal was banned. Fastcast: Warmer.