We Measured Air Pollution in Some of London's Richest and Poorest Boroughs

London's air quality is not good. If you've been paying attention to the headlines, you'll know that long-term exposure to air pollution is killing 9,500 Londoners per year, while pupils at 800 London schools are being exposed to levels of nitrogen dioxide (NO2) in breach of EU guidelines. And after spending a few days travelling around the capital measuring pollution, let me put it this way: I'm now reluctant to breathe as I cross major roads.

"Road traffic and cars are the biggest problem for air pollution," Jenny Bates, clean air campaigner at Friends of the Earth, tells me. "We need to actually cut traffic levels, not just have cleaner cars, and the government isn't really tackling this."

London mayor Sadiq Khan's London Plan takes the issue more seriously, in her view. But Friends of the Earth maintains that the targets aren't strict enough to really deal with the problem. The UK has a goal to stop selling petrol or diesel vehicles after 2040, but Friends of the Earth thinks this is too lax, not to mention that a lot of the road traffic pollutants are actually generated from brakes, tyres and road wear.

London's NO2 levels are dangerously high, and the city’s grim air quality became blatantly obvious to me as I travelled across Hackney, Newham, Kensington and Chelsea, Lambeth, and Wandsworth – boroughs with some of the city's highest and lowest poverty rates, according to the Trust for London – clutching a keychain air quality measurement device called "the Flow", made by French company Plume Labs.

Why was I doing that? To see if the wealth of an area has any bearing on the level of air pollution its residents are exposed to.

The Flow uses traffic light colours: green means pollution levels are below the recommended annual exposure thresholds the World Health Organisation (WHO) sets for one year. Orange is considered more or less acceptable. Red means the WHO recommends you shouldn’t stay in that air for more than 24 hours. Purple means you may start to experience more serious health consequences.

Near Hackney New School and Newham's First Steps Montessori Prep School, for example – places where children spend a lot of their time – the device flashed purple, indicating there was more than double the amount of NO2 present than recommended by the WHO.

I took my readings in London during sunny March days when the city's air pollution forecasts were "low" as a whole, with no warnings against spending time or exercising outside, even for vulnerable people or those with asthma. The Flow air measurement gadget syncs to an app that gives more granular data to optimise help you find the healthiest route to wherever you want to travel. It’s not laboratory grade, but close enough to give you a good idea.

Now for the science stuff. I recorded three key measurements for air pollution, starting with Particulate Matter (PM):

PM2.5 and PM10: Particulate Matter can get into your airways and lungs and bind to blood vessels. PM10 are tiny particles smaller than 10 microns in diameter, and PM2.5 even smaller, at less than 2.5 microns. What does that mean? Well, PMs can cause cardiovascular and respiratory diseases, as well as lung cancer. WHO’s annual mean target for PM2.5 is 10 micrograms per cubic metre air (µg/m3), while for PM10 it’s 20 (the EU targets are 25 and 40 respectively).

Nitrogen dioxide: NO2 is an irritating gas that can cause asthma and bronchitis, and possibly lead to decreased lung function. The annual NO2 mean target from the WHO and EU is 40. As you'll see in the readings below, I often found that levels of NO2 were more than twice this amount.

Volatile Organic Compounds: VOCs are airborne gases that can cause irritation and impact breathing. There’s a wide range of VOCs, each with separate recommended limits. Here’s a snapshot of what sort of air quality Londoners may encounter as they move about the city.

Thirty-six percent of Hackney residents live in poverty, according to the Trust for London – well above the London average of 27 percent. Hackney also has the highest infant mortality rate of the whole city, and according to the Flow device’s “purple”, Hackney residents also breathe some pretty bad air. (Since VOC numbers can spike dramatically if someone walks by smoking a cigarette or wearing lots of perfume, we’ve only included these readings for indoor locations.)

Dalston Superstore: red.
(PM2.5: 6 / PM10: 14 / NO2: 94)

The Haggerston pub (by Hackney New School): purple.
(PM2.5: 6 / PM10: 1 / NO2: 127)

London Fields park (by Gayhurst Community School): red.
(PM2.5: 8 / PM10: 13 / NO2: 88)

Sutton and Sons vegan chip shop: red.
(PM2.5: 10 / PM10: 19 / NO2: 93)

Oslo Hackney: purple.
(PM2.5: 10 / PM10: 1 / NO2: 102)

Hackney’s “purple” average is owed mostly to the high levels of NO2, which spiked far above recommended levels at five out of seven locations.

You could smell exhaust fumes in some of the places where I picked up these midday readings, but even London Fields park gave high readings, demonstrating that, in 2019, you're exposed to dangerous levels of air pollution even in London's supposedly green areas . A passer-by said "yikes" after witnessing the purple light outside venue Oslo Hackney, adding that he might think twice before having a drink outside pubs facing major roads.

Newham has London’s highest number of homeless households in temporary accommodation, according to the Trust of London, and 32 percent of working residents are low paid. Air quality is also alarmingly poor, with the Flow device delivering a verdict of “red”.

Olympic Park (by Bobby Moore Academy): orange.
(PM2.5: 4 / PM10: 1 / NO2: 38)

Roof East in Stratford: red.
(PM2.5: 2 / PM10: 1 / NO2: 86)

Westfield shopping centre, indoors: green.
(PM2.5: 14 / PM10: 20 / NO2: 8 / VOC: 4)

Familia Café (by First Steps Montessori Prep School): purple.
(PM2.5: 2 / PM10: 1 / NO2: 100)

The Flow device hovered mostly around red and purple in Dalston, dropping to orange on the Overground passing through Hackney Wick and the Olympic Park. Roof East is closed until spring, but people were enjoying the sun on the square in front, where NO2 levels flashed red – high NO2 levels were also the main problem in Newham. People at Forest Gate's Familia Café drank their coffee indoors – probably for the best, as several roads intersect out front.

London’s smallest borough is in part very rich, and in part very poor. On the whole, the Trust for London found that Kensington and Chelsea did far better than the average London borough, with child poverty rates at 29 percent compared to the city’s average of 37 percent. Air quality was more moderate rate too, with Flow flashing “orange”.

Notting Hill Book Exchange on Portobello Road: red.
(PM2.5: 46 / PM10: 73 / NO2: 42)

Life Centre yoga studio in Notting Hill, indoors: green.
(PM2.5: 9 / PM10: 18 / NO2: 8 / VOC: 6)

Evans & Peel Detective Agency cocktail bar (by St Cuthbert with St Matthias Primary): orange.
(PM2.5: 36 / PM10: 45 / NO2: 32)

The device flashed red in the backstreets of Notting Hill at 4PM, and spiked to purple at the major roads here, too. While NO2 levels were high also in Kensington and Chelsea, Flow found that particulate matter was more of an issue here.

At 30 percent, Lambeth’s poverty rate is higher than the city average, according to the Trust for London. 18 percent of Lambeth’s residents earn less than the living wage, faring better than the city’s average of 22 percent. Flow’s “orange” rating for the area’s air quality is a moderate ruling too.

Phonox club in Brixton: red.
(PM2.5: 10 / PM10: 19 / NO2: 87)

Franco Manca in Brixton Market, indoors: green.
(PM2.5: 2 / PM10: 6 / NO2: 19 / VOC: 3)

The Dog Star in Brixton, indoors: green.
(PM2.5: 4 / PM10: 5 / NO2: 20 / VOC: 2)

Clapham Common (by St Francis Xavier 6th Form): orange.
(PM2.5: 10 / PM10: 43 / NO2: 39)

A diner queuing at Franco Manca inside the covered Brixton Market commented that she expected the NO2 levels to be better in the market, as it’s sheltered about 30 metres from the main road. Flow’s measurements were mixed: NO2 levels were very high outside Phonox at 6PM rush hour on Brixton Road. I only had to walk 50 metres into Clapham Common to see an improvement in air quality compared to the main road, but still, both NO2 and PM10 levels remained over the limit.

At 3.5 percent, Wandsworth’s unemployment is the second-lowest in the city, according to the Trust for London, and at 11 percent, Wandsworth has joint-best rating in the city for the number of low-paid workers. But income inequality is high, and the borough has one of the city’s worst rates for premature mortality. Flow’s verdict of “orange” for reflects a similar mixed bag for air quality.

The Ship riverside pub in Wandsworth Town: green.
(PM2.5: 10 / PM10: 1 / NO2: 7)

The Alma pub in Wandsworth Town (by St Faith’s CE Primary): orange.
(PM2.5: 6 / PM10: 7 / NO2: 25)

The Exhibit in Balham (by Ravenstone Primary School): red.
(PM2.5: 6 / PM10: 12 / NO2: 66)

The air quality wasn’t too bad at the outside seating at the Exhibit bar, gallery and club space in Balham – a NO2 reading of 66 seemed almost moderate compared to elsewhere in the city, especially for a venue facing a supermarket car park. In Wandsworth Town at 8PM, Flow’s first sustained green light of the day came at the Ship, where you can have a drink by the Thames and enjoy a cleaner breeze from the river.

Northern Line, at Elephant & Castle: purple.
(PM2.5: 113 / PM10: 124 / NO2: 0 / VOC: 8)

Victoria Line, at Stockwell: purple.
(PM2.5: 111 / PM10: 120 / NO2: 0 / VOC: 6)

Central Line, at Bethnal Green: red.
(PM2.5: 75 / PM10: 80 / NO2: 7 / VOC: 6)

During both outings, Flow’s high of the day was measured on the Tube. Recent studies have confirmed that the air is terrible on the Underground, with deep lines such as the Northern Line being the worst offenders, especially for particulate matter (as confirmed by the readings which showed PM2.5 and PM10 spiking far beyond recommended levels).

My conclusion after a day of measuring London’s air quality was that yep, it’s pretty bad. There was definitely a correlation between poor boroughs and worse air pollution, but a busy traffic corner will have high NO2 levels no matter where you are. It’s definitely worth avoiding major roads, especially during rush hour, and walk down back streets and through parks whenever possible. And if you’re going for a run, maybe opt for a nice park in an affluent area – your lungs will thank you.

@jessicafurseth