Air pollution was until recently regarded as a problem mainly for those whose health was already compromised or vulnerable in some way: the very old, the very young, and those with existing respiratory problems such as asthma. Thanks to groundbreaking research in the last few years, we now know the problem goes much further, to the root of human health: air pollution has been linked to miscarriage, dementia, heart disease and lower intelligence.

There is scarcely an aspect of human health that is not affected by the silent insinuation of this invisible killer into our lungs, our blood, our brains and every other organ.

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Yet while the science has piled up, action has been slow. One reason is the diffuse nature of air pollution. There is no single cause, and some of the old sources – such as coal-fired power stations – have been phased out. Agriculture is an increasing source of air-polluting emissions and so, too, are the biomass-burners some people have turned to as a green alternative for heating their homes.

But it is now clear that diesel-powered vehicles are likely to be the worst offenders, and for decades government policy has been geared towards encouraging their uptake, through preferential tax rates. The criminal activities of some in the motor industry also outstripped governments’ ability to catch up with stronger enforcement.

This government has an astonishing record of being taken to court by activist lawyers determined that ministers should stop ignoring medical evidence on air pollution. By almost this time last year, the government had lost its third court case demanding that it should meet its legal obligations on preventing citizens from breathing dirty air. After that, it was taken to Europe’s highest court to explain its actions and still faces millions of pounds in fines for its failure to safeguard UK citizens in accordance with European rules.

All of that enforcement was dependent on the UK’s membership of the EU. Once outside its dictates, the government will be freer to set its own rules on what air we should breathe, as well as what water we should drink and bathe in, and what food we should be allowed to eat.

The new air quality strategy is its response to concerns over air quality, claiming to be a replacement for the EU’s strict multi-year laws and science-based targets, and the mechanisms by which governments can be taken to account for not meeting these standards.