A killer smog: Oct. 27, 1948

The residents of Donora, a small mill town along the Monongahela River in western Pennsylvania, aren’t much worried when a thick fog traps air pollution from the local zinc smelting plant and steel mills over the city. They’re used to polluted air, and while the acrid yellow smoke burns eyes and throats, people go to work and kids head off to school.

But the pollution, which contains unusually high levels of sulphuric acid, carbon monoxide and fluorine, never dissipates, and by the next day, doctors and health officials are warning anyone with respiratory conditions to get out of town.  Unfortunately, the smoke is so thick that it’s nearly impossible to drive.

Not only are the hospitals soon overflowing, but firefighters with oxygen tanks begin going door to door. Many residents make a point of calling every one of Donora’s eight physicians, hoping that will get a doctor to their houses sooner.

People start getting very sick. Over the next few days, 20 will die and almost half the town’s 14,000 residents will need treatment. Almost 800 animals also die. Still, it takes four days for local doctors to convince the owners of the smelting plant to shut it down temporarily.  As it turns out, that same day, Halloween morning, a rainstorm finally clears the air.

Eventually, a local group called the Society for Better Living sued the Zinc Works.  Its owners agreed to make a relatively small cash payment, but according to the agreement, the company was absolved off all responsibility for the deaths and illnesses caused by the smog.

The U.S. Public Health Service released its own findings in 1949. It concluded that a temperature inversion—where cold air is held close to the Earth’s surface by warmer air above it—was responsible.  The incident, it said, was a “freak of nature” and an “act of God.”

Still, the disaster, for the first time, made Americans aware of just how dangerous air pollution could be.  In 1955, Congress passed the Air Pollution Control Act, the first federal legislation that recognized pollution as a problem.  That was followed by the Clean Air Act in 1963, the first federal law to set standards for air quality. And then, in 1970, President Richard Nixon signed an even tougher Clean Air Act, one that established the Environmental Protection Agency and gave it the authority to enforce air quality standards.

By then, though, Donora’s smelting plant had closed.  So had two mills operated by U.S. Steel.  Property values plummeted and people moved away.  Donora’s population is now less than half of what it was that grim late October week back in 1948.

Five years ago, to commemorate the 60th anniversary of the tragedy, the Donora Smog Museum opened in a storefront on a downtown street.  The sign out front carries the phrase, “Clean air started here.”