Pollution in London's air was at a dangerously high level earlier this month
London's air was contaminated with record-breaking levels of harmful pollutant earlier this month.
According to The Evening Standard, all air quality monitoring sites in the city hit "high" or "very high" between Thursday March 10 and Sunday March 13 - the peak being on Saturday when 11 out of the 18 measuring sites in the capital hit "very high."
The microscopic particles, known by experts as PM2.5, can penetrate deep into lung tissue and are too minute to be filtered out by the human body's normal defences.
The smog was an accumulation of dirty air from industrial regions of Germany, Poland, and Holland which gradually drifted towards south-east England, where it was made even filthier by the emissions of London's vehicles, the Standard reports.
These new readings are the most severe since PM2.5 levels in the capital were first measured due to health concerns in 2012.
A report published that year said the spikes in the particle were linked to increased hospital admissions and the premature death of the old and sick, and a relationship was found between long-term exposure and lung cancer.
The report, published by the Air Quality Expert Group, also said that no known safe level of the particle had been identified.
Simon Birkett, founder of the Clean Air in London campaign, told the Evening Standard:
It's a national disgrace that it's taken an investigation by the Evening Standard to unearth the worst air pollution episode in recent years. Worse, Sadiq Khan and Zac Goldsmith both refused to share our tweeted smog warnings at the time.
Professor Sir Malcolm Green, founder of the British Lung Foundation, has compared inhaling high levels of the PM2.5 particle to breathing in "little particles of tar" and said they are capable of entering the lungs and finding a way into the bloodstream.