If you do not remember smog, breathe easy.

For the moment, at least. That hellish product of mist and brown coal once killed thousands routinely in our great cities. Then, almost 60 years ago, the Westminster Parliament decided clean air was not such a bad idea, and passed an Act to make it so.

Do we need another law? In the United Kingdom in the early 1950s sulfur dioxide swept the streets, carrying off young and old. Now we confront nitrogen dioxide. Anyone who tries to move through Glasgow, Edinburgh, or other places besides, tastes its reek and, sometimes, suffers its taint. If the Supreme Court orders a government - meaning the next government - to clean up its act by the year's end, who will argue?

Some might. They would be, once eyes were scrubbed clean, myopic. The clear danger to the health of people ought to be paramount, but if that case will not suffice, there is an economic argument. Filthy cities, toxic cities, cities that repel their own inhabitants, are bad for business. This can and has been shown on every continent.

The court, led by Lord Carnwath, has found in favour of Client Earth and others after a five-year struggle to prove that the urban environment in places such as Glasgow can no longer be sustained. A burden falls, in particular, on a Scottish Government that tends to talk more about the economic potential of alternative energy than about simple filth in urban lungs. So why not a Clean Air Act for Scotland?

In the mid-1950s, the Government was less than keen. It believed - governments do not change by much - that a reform would hinder the economy. But the ensuing legislation was, to modern eyes, remarkable in its scope and ambition. In essence, the United Kingdom was forbidden the habit of poisoning itself. A Scottish administration often accused of hubris might wish to imitate at least one example.

After all, Lord Carnwath speaks of "immediate action". Decode the juridical language and you hear the legal voice say that enough time has been wasted on this; lives, too. The administrations in Westminster and Edinburgh have both shouted into the fog. The pollution endured by children, businesses, travellers, tourists, dogs, birds and passing politicians is now, in Glasgow and elsewhere, out of hand.

Bus companies will not like it. If emissions are part of their business, however, they have an obligation to deal with any mess they might create. Transport groups have tried hard in this respect, but the pollution measurements found regularly in Edinburgh, Glasgow and elsewhere are hard to dispute. "Environmentally-friendly" travel still leaves a lot to be desired.

Clean air should be a simple enough desire. Pollution is not, as the Clean Air Act ought to have made obvious in 1956, an inevitable consequence of urban life. If our cities are to be restored to greatness, some of the muck, old and new, needs to be banished once and for all.