Enjoying the sun? I do hope so, not least because there is an extra reason to relish the best spell of good weather in seven years. Dangerous air pollution normally soars in such conditions, but so far we have largely escaped. Fresh, clean north‑easterly breezes, blowing in off the North Sea, have dispersed it before it can build up.

Not that we have got off entirely scot-free, or will necessarily go on doing so well. On Wednesday, high pollution levels struck south-west London, for only the third time in six years. And experts fear that the winds may shift eastwards tomorrow, adding bad air from the Continent to our own toxic brew.

But whatever happens in the next few days, air pollution will remain one of the country’s biggest public health problems, killing tens of thousands of people a year. And among the main reasons for its severity are official measures to combat global warming which – ignoring top medical advice – have long encouraged motorists to switch fuels.

More than half the cars now sold each year run on diesel. They presently make up a third of the total car fleet, compared with just 7.4 per cent only nine years ago. The dramatic rise has been explicitly encouraged because they emit slightly less carbon dioxide than their petrol-driven counterparts. And big environmental groups that used to campaign noisily against them have remained largely silent, possibly because of their overwhelming, if understandable, concern with climate change.

This is a serious matter. Tiny particulates, one of the two most serious pollutants emitted from car exhausts, are officially calculated to kill 29,000 people a year, over 10 times as many as die in car accidents, in a toll only exceeded by smoking. And the Government’s Committee on the Medical Effects of Air Pollution has also suggested that they may play a part in 200,000 more deaths. No one has yet worked out a similar fatality figure for the other big danger from exhausts, nitrogen dioxide, but it is strongly linked with asthma, and a major 25-city study has suggested that living near main urban roads could account for up to 30 per cent of all new cases of the disease in children.

Much the worst problem is in London, shamefully the European capital city most polluted by nitrogen dioxide. Vehicles are responsible for half of this pollutant, and 80 per cent of the particulates, in London air. And of these – according to a groundbreaking report by Policy Exchange, the Prime Minister’s favourite think tank, last year – no less than 91 per cent of the particulates and 95 per cent of the nitrogen dioxide come from diesel exhausts.

Nor is this all. Last year the World Health Organisation officially designated diesel fumes as a cause of cancer alongside asbestos and plutonium. And the most deadly particulates are largely made of black carbon, which is emerging as one of the most important causes of global warming. So the saving in carbon dioxide emissions is almost certainly outweighed. Instead of combating climate change, the dash to diesel is likely to be making it worse.

Much of the problem is down to EU emission standards, which have long allowed diesel engines to emit much more nitrogen dioxide than petrol ones. In the United States, where equal limits are applied, the diesel expansion has not taken place: just 0.6 per cent of cars burn the fuel. Worse, though the standards have been tightened so that they look good under laboratory conditions, they have had little effect on real driving: King’s College London scientists say actual emissions from diesel engines have remained much the same since the turn of the millennium, while those from petrol ones have tumbled by 96 per cent.

If that were not bad enough, official incentives designed to fight climate change have focused only on carbon dioxide. The most carbon-friendly cars pay no vehicle excise duty (compared with £475 a year for the worst ones), are exempted from London’s congestion charge and may get discounts on parking permits. Such measures have done much to fuel the diesel boom and so increase pollution. The campaign group Clean Air in London says that nitrogen dioxide emissions are more than twice what they would have been if we had retained the same mix of cars as in 2000.

At last there are slight signs of change. London Mayor Boris Johnson this month stopped low-carbon diesel cars being exempted from the congestion charge. Camden and Kensington and Chelsea councils now charge them extra to park. But ministers still seem only to be concerned with carbon dioxide – and conning millions of well-meaning motorists to endanger their fellow citizens by persuading them that using diesel is the green way to go.

via Why is killer diesel still poisoning our air? – Telegraph.