Fall may be in the air, but in China, it’s the pollution that’s most visible. This is the time of year when many northern industrial cities switch on coal-fired heating plants to provide warmth to urban dwellers. When combined with copious quantities of industrial pollution from factories dependent on coal, entire cities shut down, as Harbin did a couple of weeks ago.

The government’s response is hardly reassuring: more pledges of conversion to cleaner fuels, even though coal use is expected to double by 2030, as well as plans to set up a national monitoring system in the hardest-hit cities. Fiddling while Rome burns.

There are plenty of historical antecedents for China’s dilatory response. As I noted last week: Both the U.K. and the U.S. tolerated staggering pollution levels in their industrial cities in the 19th century. Nonetheless, so-called “killer smogs” in the 20th century eventually led to serious reforms in both nations. Whether China follows in those footsteps remains to be seen.

In the U.S., the watershed event was a disaster that befell Donora, a suburb of Pittsburgh. In October 1948, a weather inversion trapped sulfurous clouds of smoke and fog over the settlement. Donora soon became, in the words of the New York Times, a “twilight world” where the sun disappeared, leaving the city in a purgatory of pollution.

Soot Tracks

Strange things happened: When people walked down the street, they left a trail of white tracks where their footfalls had disturbed soot accumulating on the ground.

A zinc smelter continued to belch a toxic mix of pollutants into the air, where it mixed with smoke from coal-fire furnaces.

By the fourth day, hospitals overflowed with patients gasping for breath, most of them older and already suffering from respiratory ailments. An elderly barber fell ill in his shop. Terrified, he tried to flee town in his car, but never made it: He was found slumped over the steering wheel, “his face reddened in mortal cyanotic agony.”

By the time rain cleared the clouds on the fifth day, 20 people had died, along with 800 animals, and 43 percent of the population had fallen seriously ill. In succeeding years, the town’s steel mills and zinc smelter closed, though mortality rates remained elevated. Subsequent studies suggested the primary culprit was sulfuric acid generated in part by the coal-burning mills.

The disaster became a catalyst for state and local legislation to regulate air pollution. Other cities became synonymous with smog in the 1950s and 1960s, notably “Smogtown,” or Los Angeles, though its brown skies had more to do with automobile emissions than the classic mix of fog and smoke. But in the U.S., nothing could match the Donora tragedy as a symbol of what could happen if smog reached lethal levels.

Four years after Donora, London offered a more terrifying illustration of these hazards. In November 1952, unusually low temperatures prompted Londoners to stoke up their coal furnaces earlier than usual. As coal supplies dwindled, the National Coal Board lifted restrictions on the use of a particularly low-quality, smoky fuel known as “nutty slack,” hoping that this would keep people warm.

During the first week of December, a rare weather inversion trapped vast quantities of smog over the metropolitan area. Faced with darkening skies and clammy cold, city dwellers cranked up their coal-powered furnaces.

In the center of the city, it soon became impossible to see more than a few feet. People began to complain of difficulty breathing; they noticed peculiar smells in the air. The London Times reported that “those who ventured on to the roads in the gloom of what should have been daylight made little progress, and many had to abandon their cars and walk.”

BBC Lost

Wembley Stadium shut down for the first time in decades, as did some of the city’s theaters. According to historian Peter Thorsheim, “even the BBC was affected, for a number of people who were scheduled to go on the air found it impossible to reach its studios.”

This was later dubbed the “Great Smog.” What made it great wasn’t merely the density and lethality of the pollution, which may well have been comparable to 19th-century episodes. Rather, it was the belated recognition that the departing clouds of pollution had just sent thousands of people to an early grave.

Data collected via crude monitoring devices highlighted the enormity of the environmental disaster. Normally, pollution levels in London (already famous for its befouled air) averaged around 250 micrograms per cubic meter of particulate matter and sulfur dioxide. During the Great Smog, some monitoring stations registered levels as high as 4,460 micrograms per cubic meter.

But in some parts of London, the levels probably were far greater. According to historian Peter Brimblecombe, the National Gallery’s air-conditioning system routinely clogged on account of the particulate matter in the air. At the height of the Great Smog, it clogged at 54 times the normal rate. This crude measure of air pollution implies that the levels in the neighborhood may have hit a lung-choking 14,000 micrograms per cubic meter at the peak of the disaster. (By contrast, a Chinese industrial city such as Shenyang averages combined levels of particulate matter and sulfur dioxide of about 200 micrograms per cubic meter.)

When members of the opposition Labour Party asked how many people had died of respiratory diseases, the governing Conservatives initially demurred. Public pressure mounted, and in late December 1952, the health minister reported that 2,852 more people had died during the week of the Great Smog than had died the previous year during the same time period.

The death toll was, in fact, far worse. As statisticians began combing through the data, they realized that pollution levels remained quite high through March, and that many people suffering from respiratory ailments during the Great Smog died in the succeeding weeks and months.

Higher Toll

Devra Davis, who studies air pollution and spent much of her childhood in Donora, has argued that the total death toll probably exceeded 12,000 people, though some of the fatalities may have been caused by an outbreak of influenza.

Still, even a conservative estimate puts the total at more than 7,000 fatalities. Worse, as one U.K. journal noted in the wake of the disaster, “it was not, as has been occasionally suggested, merely a matter of old people, who were due to die soon in any case, being killed. Many of those affected might have had years of useful life ahead of them.”

That observation is equally applicable to the Chinese cities where smog has become a fixture of life. There is one difference, however: In the U.K., the government was ultimately accountable for the tragedy. Four years after the Great Smog, Parliament passed the Clean Air Act, and restrictions on industrial emissions and the use of coal for heat gradually brought the era of deadly air pollution to an end.

Unless something changes quickly, no such resolution awaits China. In the past year, the government has fought attempts to make accurate pollution data public. It has proven even less forthcoming in releasing data on mortality rates during smog events such as the one that hit Harbin.

Sooner or later, some city in China will find itself trapped in a once-in-a-lifetime weather inversion. When that happens, government mendacity and incompetence may ignite a tragedy that makes the Great Smog seem tame by comparison.

(Stephen Mihm, an associate professor of history at the University of Georgia, is a contributor to the Ticker. Follow him on Twitter. This article is the last of two on the history of smog.)