Modern Mysteries

What was behind the 1952 London killer fog ?

By T.K. Randall
November 16, 2016

Image: Westminster Palace
Credit: David Castor / (PD) The worst air pollution event in European history, the disaster saw the entire city shrouded in a layer of choking fog for five whole days. The sky became dark, visibility was reduced to around three feet, transportation systems ground to a halt and tens of thousands experienced problems breathing.

The fog, which ultimately killed over 12,000 and hospitalized a further 150,000, was thought to have been caused by emissions from coal burning, however exactly what combination of circumstances had managed to produce such a deadly, noxious fume has long remained something of a mystery.

Now though, scientists in China believe that they may have finally found the answer.

Their research, which drew upon studies of the pollution issues experienced by Chinese cities, suggests that sulfur dioxide in the air may have been turned in to sulfuric acid thanks to nitrogen dioxide - another coal burning co-product - which interacted initially with natural fog in the air.When the fog particles eventually evaporated they left behind a deadly acidic haze.

"The difference in China is that the haze starts from much smaller nanoparticles, and the sulfate formation process is only possible with ammonia to neutralize the particles," they wrote.

"In China, sulfur dioxide is mainly emitted by power plants, nitrogen dioxide is from power plants and automobiles, and ammonia comes from fertilizer use and automobiles."

"Again, the right chemical processes have to interplay for the deadly haze to occur in China. Interestingly, while the London fog was highly acidic, contemporary Chinese haze is neutral."

Source: EarthSky.org

Tags: London, Fog