Ecology: Menace in the Skies

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On the morning of Oct. 26, 1948, at Donora, Pa., the skies delivered a deadly warning that man had poisoned them beyond endurance.

As workers trudged to their jobs, a heavy fog blanketed the bleak and grimy town. It hung suspended in the stagnant air while local businesses—steel mills, a wire factory, zinc and coke plants—continued to spew waste gases, zinc fumes, coal smoke and fly ash into the lowering darkness. The atmosphere thickened. Grime began to fall out of the smog, covering homes, sidewalks and streets with a black coating in which pedestrians and automobiles left distinct footprints and tire tracks. Within 48 hours, visibility had become so bad that residents had difficulty finding their way home.

Donora's doctors were soon besieged by coughing, wheezing patients complaining of shortness of breath, running noses, smarting eyes, sore throats and nausea. During the next four days, before a heavy rain washed away the menacing shroud, 5,910 of the town's 14,000 residents became ill. Twenty persons—and an assortment of dogs, cats and canaries—died.

Investigating the tragedy, meteorologists concluded that it had been triggered by a temperature inversion, an atmospheric phenomenon that prevents normal circulation of air. Ordinarily, warm air rises from the earth into the colder regions above, carrying much of man's pollution with it. Occasionally, a layer of warmer air forms above cooler air near the ground; the inversion acts as a lid, preventing the pollutants at lower altitudes from rising and dispersing. Inversions are no novelty, but what happened at Donora shocked public-health officials into an awareness that such layers pose a deadly threat to an increasingly industrialized and pollutant-producing society.

Sulky Sun. On Dec. 5, 1952, a thick fog began to roll over London. Hardly anyone paid any attention at first in a city long used to "pea-soupers." But this fog was pinned down by a temperature inversion, and was steadily thickened by the soot and smoke of the coal-burning city. Within three days, the air was so black that Londoners could see no more than a yard ahead. Drivers were forced to leave cars and buses to peer closely at street signs to find out where they were. Policemen strapped on respiratory masks. The Manchester Guardian reported that London's midday sun "hung sulkily in the dirty sky with no more radiance than an unlit Chinese lantern."

Hospitals were soon filled with patients suffering from acute respiratory diseases; deaths in the city mounted. The British Committee on Air Pollution finally estimated that during the five days that the smog smothered London, there were 4,000 more deaths than would have occurred under nor mal circumstances. During the next two months, there were another 8,000 excess deaths—most of them apparently caused by respiratory disease—that scientists suspected were a direct result of the killer smog.