THE INDUSTRIAL TOWN of Donora, Pennsylvania, had dealt with pollution for many years. The smoke and fumes from the local factories were a fact of life. The mills supplied jobs to the local townspeople, and the locals were known to state that the "smoke" put bread on their table.

In 1948 the small town of Donora became an example of the mounting problem of acid pollution. Between October 26 and 31, a dense fog settled on the town. A weather phenomenon known as inversion, when a cold air mass traps warm air near the ground, caused a disaster. Fumes from the American Steel and Wire Company's zinc and iron works mixed with the foggy air and stayed near the ground, trapped by the mass of cold air above. The poisonous air settled on the town and did not leave for nearly a week...