Hungary toxic sludge reaches Danube River: Top 10 environmental disasters worldwide
1. London's 'Great Smog,' 1952
In Dec. 1952, a thick, acidic smog enveloped London, lasting for four days. The smog, which came from fumes from coal stoves, industry and gas-burning cars, caused the deaths of about 4,000 people in a month and more than 8,000 in later months for reasons related to the smog.