Back in December, 1952, the city of London, England, was set upon by a thick and noxious fog. Most of the people went about life as normal, assuming the fog was normal London precipitation. But as the days moved on the fog grew more dense and more gnarly. People began to fall ill, the sky was dark and visibility was reduced to just 3 feet in some areas, and those who ventured out did so with some type of cloth over their mouth.
On the 5th day the fog lifted and as many as 4,000 people were dead. Over a 100,000 were hospitalized and the fog was eventually blamed for 12,000 human deaths and countless animals. But what happened?
For more than half a decade scientist have attempted to solve the mystery. Well, lets be fair. They KNOW that it was caused by pollutants. After all London’s factories billowed with coal smoke, just as they did here in the states. But how the perfect chemicals combined to make the poison smog was a mystery till now.
Texas A&M researchers have used laboratory experiments and atmospheric measurements in China, to come up with the answers.
“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,” researcher Renyi Zhang says.
“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.”
British Parliament still considers the worst air pollution event in the European history. On a positive note, the fog is directly responsible for Parliament passing the Clean Air Act of 1956. So there’s that.