The New York Times had an excellent piece yesterday on the 1984 Bhopal tragedy. The chemical gas leak occurred on December 4, 1984 in Bhopal, India when 40 tons of methyl isocyanate gas leaked from a Union Carbide plant. It is probably the most notorious in world history, killing thousands immediately following the event, and affecting many members of the community for years to come.
Though it is important to note that most occupational health problems come from long-term exposure, full-scale disasters like Bhopal can have a ripple effect in terms of public opinion towards occupational and environmental health. Think Chernobyl or even Three Mile Island (which caused no deaths or injuries).