Short answer: very.
For people who love parks but worry about air pollution, there’s good and bad news from London.
The good news is that, as of Wednesday morning, London has a new online map and search engine that enables you to discover exactly how polluted your local park is. The bad news is that the answers it provides are so unpromising that after consulting it you might be tempted to stay indoors, breathing through an oxygen mask.
The new map, produced by the data science company ASI, reveals NO2 levels for all of London’s parks. As the chart below (where each green bar represents a park) most of London’s public open spaces manage to stay below the agreed E.U. safe limit of 40 μg per cubic meter. But a large number exceed these limits; in Central London, it’s practically all of them.
For anyone familiar with London, browsing the map can make interesting, if sobering viewing. Some of the most polluted of the city’s parks contain more than double the acceptable limit of μg of NO2 per cubic meter. London’s worst figures are actually for what is a small patch of garden: Whittington Garden, a small oblong of greenery located next to a busy, four-lane route through London’s financial district, where NO2 levels reach 99.5 μg per cubic meter. It’s no surprise that the air is dirty in such an exposed spot (though I’ll never eat a sandwich there again). Of arguably greater concern are the levels recorded for London’s major green spaces. Even measured at its heart, Hyde Park has NO2 levels above safe limits, as do Green Park, St James’ Park and Regent’s Park. Located at the heart of a major city, you might not expect the air here to be mountain-fresh, but it’s a poor showing when the places people head to grab some fresh air offer nothing of the sort.
The worst results are mainly confined to a central East-West corridor, so as you head farther out things improve pretty fast. That still leaves many central London park-goers wheezing like an old pair of bellows, in a city where pollution kills up to 9,500 people a year.
Thankfully, London is making some changes that could improve things. This autumn, the city is getting an early warning system to alert people to pollution peaks. And starting in 2017, more polluting vehicles will have to pay an extra fee on top of the existing congestion charge to drive into central London, while Oxford Street, sometimes called the world’s most polluted street, will be pedestrianized by 2020.
Such measures suggest an easing of pollution through light tinkering, rather than the true life-saving modal shift London needs. Still, widespread public awareness of how bad London’s air pollution is remains a fairly recent phenomenon. Maps pinpointing where parkland air is poor, or public displays and text messages warning of a brownout, won’t clean London’s air. But they might help create awareness that could push Londoners into real action.