2015年经济学人 空气污染 英国需要采取更多措施来净化污浊的空气（在线收听）

Air pollution

The big smoke

Britain needs to do more to clean up its dirty air

VISITING Oxford Street, a road teeming with tatty shops and overcrowded with people, is plainly a trial. Less plainly, levels of nitrogen dioxide (NO2), a noxious gas, have been found to be around three times higher there than the legal limit. In 2013 the annual mean concentration of NO2 on the street was one of the highest levels found anywhere in Europe.

British air is far cleaner than it was a few decades ago. Fewer people use coal-burning stoves; old industrial plants have been decommissioned. But since 2009 levels of nitrogen oxides and particulate matter, coarse or fine particles that are linked to lung cancer and asthma, have fallen more slowly. The exact number of deaths caused by dirty air is unknown. But in 2010 a government advisory group estimated that removing man-made fine particulate matter from the atmosphere would increase life expectancy for those born in 2008 by an average of six months.

Much of the slowdown is the result of fumes from diesel cars, which were championed by successive governments because they use less fuel and thus produce less carbon dioxide than petrol cars. In 2001 only 14% of all cars ran on diesel; by 2013 the proportion had increased to 35%. (Greener “hybrid” and electric cars have increased ninefold since 2006, but account for just 0.5% of the entire fleet.) Second-hand cars are particularly noxious, but even newer ones have not been as clean as hoped. Many cars that belched out few pollutants in tests produced more when on the roads.

Government dithering has not helped. Part of the problem is that several departments are responsible for air pollution. This means nobody has taken a lead on it, complains Joan Walley, a Labour MP who chairs an environmental committee that has released a series of damning reports. And few politicians are keen to bash drivers. Talking to Britons about car ownership is “like talking to an American about hand guns”, quips one air-pollution scientist.

Some improvements have been made. In 2008 a “low-emission zone” was created in London, which targets large vans and coaches. A smaller “ultra low-emission zone” has been proposed for 2020, which would charge all vehicles that are not of a certain standard 12.50 (18.80) a day. European Commission fines for breaching limits may encourage cities to do more. But other countries are more ambitious: 60 such zones exist in Germany, targeting private cars as well as vans. In December Anne Hidalgo, the mayor of Paris, announced that she wanted to ban diesel cars by 2020. Cities in Denmark and the Netherlands do more to boost cycling.

When a thick “pea souper” smog enveloped London in 1952, causing the deaths of around 4,000 people in one week, the government was compelled to push through legislation to clean the air. Perhaps the largest problem now is that, with rare exceptions such as a Saharan dust smog that covered the capital in April 2014, this new pollution is invisible. But policy-makers should not lose sight of it.