Not breathing easy

A Supreme Court ruling forces the government to deal with dirty air

BRITISH air is much clearer than it once was: in 1952 one “pea souper” smog in London(see photo) caused the deaths of around 4,000 people in a week. But it is not as clean as it could be. On April 29th the Supreme Court ordered the next government to come up with a plan by the end of the year to reduce the amount of nitrogen dioxide (NO-2), a noxious gas produced by diesel engines, in the atmosphere. The judgment could have big implications for several large infrastructure projects. It also suggests how, after years of campaigning by greener types, dirty air is finally becoming a political issue.

The health effects of NO-2 have not yet been calculated for Britain, but are thought to be as potentially damaging as fine man-made particulate matter, says Gary Fuller of King's College London. A report from a government advisory group in 2010 estimated that, if all fine particulate matter (which is mostly caused by car fumes and the wear and tear of tyres on the road) were removed from the atmosphere, it would increase the average life expectancy of those born in 2008 by six months—and for those born in London by nine months.

Despite the mounting evidence of the harmful effects of dirty air, there has been little political desire to get it sorted. Responsibility for cleaning up air pollution falls over several different government departments, and may require unpopular decisions to be made about raising taxes or increasing environmental burdens on car companies. And around a third of the dirty air in Britain is swept across from Europe. Politicians could often skirt the issue by pointing out that it was a Europe-wide problem. But the ruling by the Supreme Court “takes political will out of the equation,” says Alan Andrews of ClientEarth, the group of environmental lawyers who brought the case to the Supreme Court. The government will have to clear up the air within the next decade or so, regardless of costs.

However, in the next few months Sir Howard Davies, the leader of an independent Airports Commission, is expected to issue a recommendation on where to expand airport capacity in the south-east. The court ruling adds a “potential black mark” to the case for expanding either Heathrow or Gatwick, Sir Howard's two potential options, says Matthew Farrow, the executive director of the Environmental Industries Commission, an industry group. Levels of NO-2 are already above recommended levels around Heathrow, which is next to a busy motorway, and are expected to rise at Gatwick even without another runway. It could also delay plans for a new bridge in East London.

This means the next government will have to make some swift decisions about clearing up Britain's dirty air, by introducing several “low-emission zones” to reduce the number of diesel cars and the like. Measures to cut air pollution have been taken before. In 1956, after the smog in London, the government pushed through a Clean Air Act, banning coal fires in people's homes. That decision was prompted by a crisis. The reasons for pushing through this reform may appear to be less dramatic, but they are no less important.