It’s no big secret: London’s air quality isn’t great. At all.

The capital is, at the time of writing, ranked at number 28 on IQAir’s list of ‘most polluted cities’ around the world.

And today, pollution levels in parts of the city have reached ratings Moderate to High, according to London Air Quality.

As a result, people with asthma, lung and heart problems are being warned against taking ‘strenuous’ exercise outdoors – to avoid breathing in high volumes of nasty pollutants.

So why is the air quality in London so bad? And what’s the situation everywhere else in the UK?

Here’s what you need to know.

Why is London’s air quality so poor?

‘Air quality’ generally refers to how much air pollution an area has.

And pollution is caused by all sorts: car fumes, lorry fumes, domestic and commercial heating systems, fumes from industry (such as factories) and even things like cigarette smoke.

These things release poisonous gases and substances into the atmosphere, which affects our health long-term, but also harms animals, plant life and the environment.

Pollutants, as listed on London.gov.uk, include:

  • Ozone
  • Sulphur Dioxide
  • Nitrogen Dioxide
  • Carbon Monoxide
  • Particulate Matter (PM10 and PM2.5 Particulates)
  • Lead
  • Benzene
  • Benzo(a)pyrene.

London is a big, heavily-populated city – with a lot of road traffic, and plenty of those heating systems. That’s where the vast majority of its pollution originates from.

Most pressing are its levels of Nitrogen Dioxide and Particulate Matter levels (especially PM2.5), says the Mayor of London website.

These substances are strongly linked to asthma and even death. Long-term exposure can cause serious lung issues, too.

Air pollution levels in London do vary day by day, and they also vary from borough to borough. Visit the London Air Quality website to check your local area.

How does London air quality compare to other major UK cities?

Air quality can be tracked in real time, using the US Air Quality Index (AQI) rating system.

It’s published on IQAir, and it’s easy to get a picture of how London differs from the rest of the UK – and find out what’s going on all over the world.

These ratings change frequently as pollution levels ebb and flow, but there is a 2020 average.

Overall, the UK’s AQI rating for 2020 was 34, which is classified as Good.

However, the concentration of PM2.5, one of the most concerning pollutants here, was 1.7 times above the World Health Organisation’s (WHO) annual guideline.

Interestingly, the area with the lowest pollution in the UK in 2020 was Midlothian in Scotland. Its AQI score was 16, and was rated Good.

While Christchurch, a town in Dorset, recorded the highest average AQI score of 52. It was rated Moderate.

As for levels of PM2.5, the WHO produced a report in 2019 which revealed that Warrington, Bristol, Stanford-Le-Hope, Storrington and Swansea had the highest averages, according to Compare My Move.

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