Common to all three tragedies were two key elements. First, large factories in each area had been spewing enormous amounts of pollutants into the air, the most deadly being sulfur dioxide. And second, Mother Nature came calling in the form of something called a temperature inversion.
On Tuesday October 26, the air over Donora became foggy from cool air being trapped beneath warmer air above in what meteorologists term a temperature inversion. Normally inversions last less than a day, but this one lasted a devastating five days. Within two days the fog had turned into a stinging, yellowish-gray shroud so thick…