The Donora Smog of 1948

The Donora Smog was a thick, yellow smog that covered the town of Donora, Pennsylvania, from October 26 to October 31, 1948. This deadly smog resulted in the hospitalization of about 7,000 people (about half the population) and a total of 20 deaths at the end of the five day period. The town of Donora, prior to this smog, was home to unregulated steel mills and zinc works. The emissions created by these factories on a daily basis included toxic chemicals like nitrogen dioxide.

Donora was usually smoggy in the mornings, something the citizens had gotten used to and thought little about. This was until the morning of October 26, 1948, when the usual smog failed to disperse as a result of a natural condition known as 'Thermal Inversion' (this is when a layer of warm air settles over a layer of cool air near ground level, preventing it from escaping). This condition held down the smog produced by the town below it. The citizens of Donora continued about their daily activities and noticed there was a problem only when a great amount of visibility was lost. One man recalled that event, saying "You couldn't see the hand in front of your face" (Bill Schempp, Donora Firefighter). The town was finally freed by downpour, which helped disperse the smog.

This event brought into the minds of state legislators the need for some course of action against air pollution. This later led to the 'Clean Air Act' (of 1970), which helped regulate air pollution nationwide. This act was later expanded to include both mobile and industrial polluters. The zinc works in Donora were also finally closed in the year 1956 in response to this disaster.