Monday 13 February 2017 07.00 GMT
In the UK, the department for environment, food and rural affairs issues daily alerts measuring air pollution levels. But when it comes to tips on how to respond, Defra confines itself to the slightly gnomic “reduce activity”.
So we asked a team of air pollution experts on the best ways to protect yourself when there’s a pollution alert in your city.
Exercise earlier – or do it indoors
The general advice, according to Frank Kelly, professor of environmental health at King’s College London is to “try to avoid exercising during a pollution episode. If you have to exercise, do so indoors.” As Ally Lewis, director of the National Centre for Atmospheric Science, points out though, the question of whether to “exercise, cycle to work or go for a run depends on the individual”. For keen runners, he says: “If you shift it to early in the morning, that would benefit anybody, because air pollution tends to build up with rush hour at about 7 or 7.30am. If you’re going to cycle to work, doing it an hour earlier, before pollution builds up, could have a significant impact on exposure.”
Pray for rain
“Particulate matter is removed primarily by rainfall,” according to Mark Jacobson, professor of Civil and Environmental Engineering at Stanford University. Don’t rush out as soon as it starts, though. “You have to wait a short while. If it’s moderate to high pollution and it starts raining, I would give it 60 minutes or so and then there’ll probably be quite a difference,” Kelly adds. If there’s wind and rain, even better.
Walk one street back
“Avoiding main arterial roads really does make a difference,” says Lewis. “Pollution drops away substantially when you’re walking one street back. If you look at the concentration gradient say, 20, 30, 40 metres away from a very congested road, it’s not like pristine air from the Atlantic but it will be two or three times less polluted. That’s a gain worth having.”
Use an app to avoid hotspots
Kelly recommends using “a travel app that gives you a lower pollution route choice”. King’s College have developed one for London and others are popping up, such as Plume, which covers more than 200 cities.