London Sets Pollution Record

London's air quality set a modern record during this week’s spate of pollution that occurred when cold, windless weather trapped emissions over the capital. 

"More than 20 sites recorded levels that hit the limit 10 on an index maintained by King’s College London from Jan. 17 to Jan. 24, the most since the index was introduced in 2012," said Andrew Grieve, an analyst at the college.

The college uses sensors placed around the city to measure various types of pollution, such as particulate matter and gases, Bloomberg reported.

High pollution levels come and go in what are known as episodes. At various times this week, air quality in London was worse than Beijing. But overall, the Chinese city has much worse air over a sustained period of time.

Simon Birkett, director of Clean Air in London, said Beijing would soon quickly overtake London once celebrations for Chinese New Year get underway.

“Things will go mental in Beijing,” he said. “They’ll have a massive firework problem and particles will go through the roof.”

London Mayor Sadiq Khan issued a “very high” pollution alert this week, the first since he became mayor last year. His alert meant that levels were more than twice the legal hourly limit. Children were told to play indoors.

Britain has surpassed European Union air quality limits since 2010. Last year, London blew through its annual limit eight days in. This year, it only took five.

The London mayor’s office estimates that about 9,400 premature deaths are caused each year by toxic air. It’s gotten so bad, a judge said the government had broken the law by not doing enough to deal with the problem and ordered ministers to take care of it.

London regulations that limit the burning of coal for health reasons date to at least 1273. 

The country's Clean Air Act was passed in 1956 after an event known as the Great Smog of 1952 killed thousands of people.