Killer fog, the Donora and London incidents
Autumn, leaves falling and... fog raising. Despite Donald Trump, according to whom pollution is not a problem, when smokes by cars, heatings, and industrial chimneys join fog, they can create a killer smog.
This is not just a hypothesis: in these circumstances smog is able to seriously harm health, reaching the point to kill, as already has happened at least twice in the 20th century, in Donora and in London.
Donora lethal fog
The first and worst killer fog incident happened in the USA in 1948, at Donora, a borough 39 south of Pittsburgh along river Monogahela. The fog was usual in the cold season at Donora, but October 26, 1948, a blanket of smog started to stagnate on the town so thick that people, along the way, weren't able to see their own feet.
Fog mixed to the smoke of Donora's steelworks didn't dissolve for the whole day and lasted till October 31, when factories production was halted as a matter of urgency.
The problem was so strong that streetlights up on the road didn't go out even during the hours of light, what's worst the hydrofluoric acid and the sulfur dioxide from steelworks, mixed to the fog, causing serious breathing problems to the population.
In the end in four days, 20 people died and autopsies found lethal levels of fluorine, while 50 people died the next few weeks for the same reason and 14 thousand more finished the rest of their lives with damaged lungs and hearts. But because it would have been bad for factories' reputation, they preferred to blame an “exceptional” occurrence and didn't toss any environmental alertness.
In London smog kills
A few years later the phenomenon reiterated, this time in Great Britain. In London, December 5, 1952, the city was wrapped by a shroud of mist so heavy that people had to walk close to the walls not to lose orientation, while the movie theaters stopped projections since from the hall people couldn't see the screen.
Londoners protested immediately because of bad smell, but the problem was much more serious. London's fog, which lasted until December 9, was mixed to the smoke of heating systems, that burned at that time low-grade, sulfurous variety coal, so when fog lifted 12 thousand people had died (4 thousand just in the first week) and over 100 thousand more were made ill by the smog's effects.
This time, btw, was not possible to pass off in silence that fog mixed to smog was the main cause of death so some years later, in 1956, government was forced to issue albeit reluctantly, the Clean Air Act, applied until 1964 and then replaced by new and modernized rules, to reduce air pollution, especially in the main UK cities.