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The Mystery of the London Fog Finally Solved

14 Dec 2016, 4:29 pm

The decades-old mystery of what caused a killer fog that claimed the lives of thousands of people here appears to have been solved by a team of international scientists.

For five days in December 1952, a fog that contained pollutants enveloped all of London. By the time the dense fog cover lifted, more than 150,000 people had been hospitalized and at least 4,000 people had died. Researchers now estimate that the total death count was likely more than 12,000 people, as well as thousands of animals. Despite its lethal nature, the exact cause and nature of the killer fog has largely remained a mystery. Recently, a team of researchers has determined the likely reasons for its formation.

The research was published online Nov. 9 in the journal Proceedings of the National Academy of Sciences.

“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,” lead author Renyi Zhang, a scientist at Texas A&M University, said in a statement.

“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.”

The study said that similar conditions often occur in China.

“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 said.

He said sulfur dioxide is mainly emitted by power plants in China, while nitrogen dioxide comes from power plants and vehicles, and ammonia comes from fertilizer use and vehicles.

“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 basically neutral,” he added.

The 1952 killer fog led to the creation of the Clean Air Act, which the British Parliament passed in 1956. Researchers still consider it the worst air pollution event in European history.

Story Image: Texas A&M

Credit: Leonard Bentley

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