– In December 1952 a great fog blanked London killing as many as 12,000 people. Causing breathing problems, the fog covered the city for five days and it is the worst air pollution event in the European history.
This terrible event became known as the Great Smog of 1952, also known as the Big Smoke, The Great Pea Soup and the Killer Fog.
What caused the great Smog of 1952 has been puzzling researchers for decades.
Now scientists think they have finally solved the mystery of the Killer Fog.
A group of international team of scientists working together with researchers from Texas A&M University, suggests the same air chemistry also happens in China and other places.
Scientists conducted a number of laboratory experiments and found that nitrogen dioxide converting comparatively benign sulfur dioxide into lethal sulfuric acid.
“People have known that sulfate was a big contributor to the fog, and sulfuric acid particles were formed from sulfur dioxide released by coal burning for residential use and power plants, and other means,” explained Texas A&M researcher Dr Renyi Zhang. “But how sulfur dioxide was turned into sulfuric acid was unclear.
Our results showed that this process was facilitated by nitrogen dioxide, another co-product of coal burning, and occurred initially on natural fog. Another key aspect in the conversion of sulfur dioxide to sulfate is that it produces acidic particles, which subsequently inhibits this process.
Natural fog contained larger particles of several tens of micrometers in size, and the acid formed was sufficiently diluted. Evaporation of those fog particles then left smaller acidic haze particles that covered the city.”
The study shows that similar chemistry occurs frequently in China, which has battled air pollution for decades. Of the 20 most polluted cities in the world, China is home to 16 of them, and Beijing often exceeds by many times the acceptable air standards set by the U.S. Environmental Protection Agency.
“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,” Zhang adds.
Not only did the Killer Fog of 1952 cause the death of more than 12,000 people. It also resulted in approximately 150,000 hospitalizations and thousands of undocumented animal deaths.
Initially, the British government was reluctant to act in the wake of the Great Smog. Following a government investigation, however, Parliament passed the Clean Air Act of 1956, which restricted the burning of coal in urban areas and authorized local councils to set up smoke-free zones.