Donora, a small industrial town built on the metal processing and steel industry, is situated on the banks of the Monongahela River in Pennsylvania, USA. On Tuesday October 26, 1948, a murderous fog took many lives in Donora. Twenty residents died in a week. After that, an additional 50 people died within a month, and as many as about 6,000 people fell ill. And its impact lasted long. Even after a decade, the mortality rate here remained significantly higher than in surrounding areas. The Donora incident played a decisive role in alerting the entire United States of the horrors of air pollution and in the federal government enacting regulatory legislation.