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15 July 2021

London air

or, I can’t hack black snot.

I really like living in London, but one jarring feature of its airscape bothered me from the start. Sometimes, home after a day out, I would blow my nose to find my snot black and sooty. I eventually realized that the Tube, which I thought was the most convenient and environmentally friendly way to get around the city, was the culprit. The source of my sable nasal discharge was the horribly polluted air in its deep lines.

Deep Tube lines are badly ventilated and full of, among other things, small particles emitted by the trains’ brakes and tracks. A 2019 Financial Times investigation1 found that harmful particulate matter concentrations in all examined Zone 1 Tube segments exceeded the World Health Organization’s safety limit, with parts of the Central line exceeding it more than eight times over. At station platforms, these particles cake surfaces that aren’t touched often and make the air so dusty that you can see it move under the light. They’re also what turn your snot black.

With Tube air quality on my mind, I decided it was worth thinking up ways to mitigate the effects of bad air in London and cities more generally. I’m sure they’re nothing new to a seasoned Londoner, but I hope they help other newcomers like me who can’t hack black snot.

Air pollution is a complex and localized phenomenon. It depends on a lot of things, including nearby sources of pollution, the weather, geography, and the built environment. It can also differ significantly between two nearby points on the same sidewalk, street, block, or neighborhood.

One of the best things we can do to reduce our exposure to bad air is change our modes of travel. Depending on what works for your journey, it’s best to go by foot, bicycle, bus, then Tube, in that order. Because private cars can have sophisticated air filters, they are perhaps the best way to get around a city from a personal air quality perspective. But, if they aren’t electric, they make the air more polluted for everyone else.

If you’re walking, try to take side streets instead of major ones. When you inevitably do have to walk near traffic, stay as far from the road as possible. A few feet of distance make a big difference in the amount of exhaust you breathe in. Cycling is similar to walking: it’s best to take quiet roads or dedicated bicycle paths where you won’t end up stuck behind an exhaust pipe at a red light.

In terms of public transit, it’s better to take the bus than the Tube if your schedule can handle it. The air is less polluted, and it’s more pleasant to travel above ground. However, sometimes the Tube is the only reasonable way to get where you’re going. For those journeys, sub-surface lines like Circle and District, especially where they run above ground, are much better than deep lines.

If you can’t get around spending time in a polluted environment, you might consider wearing a pollution mask. The best kinds have straps that go around your neck and the top of your head as well as a rubber-like material to make a tight seal around your face. I’ve found that using one keeps my snot a healthy color, even after long rides on deep Tube lines. Wearing some kind of glasses can also be useful for moving around the city. They keep a quickly passing person, bicycle, car, or train from getting something unpleasant in your eyes.

At home, opening windows for ventilation is good for air quality as long as the air outside isn’t too polluted. If you live on a major street and there isn’t much distance between your home and the road, be careful not to open street-facing windows during periods of high traffic. An air purifier will also improve your indoor air quality. Look for one with a good, easily replaceable filter and a high air change rate.

  1. “London Underground: the dirtiest place in the city”