More than six decades after London's Great Smog killed several thousand people within a few days, the UK capital still has a deadly air pollution problem.

Putney High Street, a busy thoroughfare in southwest London, burned through its legal annual limit on toxic nitrogen dioxide emissions in just the first eight days of 2016, according to the London Air Quality Network, which is part of King’s College London’s Environmental Research Group.

High levels of NO2 can cause lung irritation and increase the risk of respiratory infections.

European Union rules stipulate that a “maximum nitrogen dioxide concentration” of 200 milligrams per cubic meter must not be exceeded for more than 18 hours during the entire year. Putney High Street hit its 19th hour during the morning commute on Jan. 8.

“It is breathtaking that toxic air pollution has breached the legal limit for a whole calendar year within a few days,” Simon Birkett, founder and director of Clean Air in London, told the Independent.

Breathtaking, but not that surprising.

Oxford Street took just two days to breach NO2 pollution limits last year. This year, faulty monitoring equipment meant its air quality couldn’t be measured for the first week of 2016.

An additional five roads exceeded legal limits in the first month of last year, too, the London Air Quality Network said.

The air isn’t much cleaner in the rest of London, either.

A recent report published by the UK-based independent think tank Policy Exchange found 12.5 percent of Greater London, particularly in the center of the city, currently exceed legal limits on NO2 emissions, and even rival those seen in the notoriously polluted Chinese cities of Shanghai and Beijing, “which are amongst the worst cities globally in terms of overall air quality.”

The most polluted parts of London had NO2 concentrations nearly four times the legal limit, the report found.

It's literally killing Londoners.

A study by the King’s College London, and cited in the Policy Exchange report, found 9,400 people died as a result of air pollution in 2010, including 5,900 deaths from NO2.

One of the biggest sources of NO2 is road transportation, accounting for 45 percent of emissions. Diesel-engine vehicles are a major culprit.

Diesel cars have become increasingly popular in recent years, owing to their lower carbon dioxide emissions and greater fuel efficiency. In 1994 they made up just 7 percent of the UK’s total fleet, but they now account for 36 percent. And while they spew less carbon dioxide into the air than their gasoline-powered counterparts, they are heavier emitters of NO2.

That’s not to say London hasn’t made progress on reducing other nasty pollutants.

Data suggests efforts to tackle air pollution — such as London’s low-emission zone, congestion-charge zone, restrictions on older taxis and investments in public transport — are bearing fruit, with levels of carbon monoxide and sulfur dioxide plummeting 80 percent since 1996, the Policy Exchange report said. Levels of PM2.5, dangerous particles so tiny they can travel deep into a person's lungs, are within legal limits.

But NO2 levels remain dangerously high. And as the UK prepares to mark the 60th anniversary of the Clean Air Act, which was introduced in response to the Great Smog of 1952 to regulate smoke emissions, it’s clear the country must do more.