CAMBRIDGE (England) • In January, researchers at King's College London announced that pollution levels on Oxford Street, in central London, had exceeded limits set for the entire year in just the first four days of 2015. Similarly alarming numbers have been recorded for other streets in the city - and yet the mayor, Mr Boris Johnson, has delayed implementation of stricter air-quality measures until 2020.

What's happening in London is being played out in cities worldwide, as efforts to curtail the onslaught of air pollution are stymied by short-term vested interests, with potentially disastrous results.

This is not the first time that society has confronted a threat of this kind. In the 19th century, the Industrial Revolution brought millions into the world's cities, which expanded with unprecedented rapidity, leading to atmospheric pollution as the fossil fuels burned in urban homes poured huge quantities of sooty emissions into the air.

Nowhere was this more obvious, or more threatening, than in London, where air pollution was literally in front of everyone's face in the form of the city's infamous polluted fog.

The British capital is particularly liable to natural winter fogs. It is surrounded by low hills, with marshland on its outskirts and a large river running through it. Its location encourages the meteorological phenomenon of temperature inversion, when warm air traps cold air beneath it for days on end. During such a fog, the sulphur-laden smoke from domestic coal fires and factory chimneys was unable to rise into the upper atmosphere and seeped into the natural fog, turning it yellow, brown, green or black - a process beautifully captured by Claude Monet in his series of paintings of London fog.

Such fogs were known as "pea soupers". As the name suggested, they were often so thick that people could not see their own feet as they walked through them on the city streets. As the city grew, these fogs occurred more frequently; they became more dense, and they lasted longer.

Londoners were well aware of the dangers the fogs posed to health. In 1873, a number of prize cattle at the Smithfield cattle show, in central London, choked to death during a particularly dense and suffocating fog. Newspapers and medical experts pointed to a statistical increase in deaths in London's human population from bronchitis and other respiratory diseases during fogs. Now-forgotten pulp-fiction writers like William Delisle Hay produced alarmist stories imagining the destruction of London's entire population caused by the fog.

Fog could also be a cover for crime. "Linklighters", boys or men who earned a few pennies carrying lighted torches to lead people through the darkened world of the London streets, would sometimes lead people down a quiet alleyway to be robbed. Burglars were reported to be particularly fond of breaking into people's houses during major fogs, which not only made them hard to see, but deadened sound as well.

And yet, for decades, every law proposed in Parliament to curb smoke emissions was watered down so heavily that it had no tangible effect. What explains such legislative inertia?

Vested interests were a major obstruction. In 19th- and 20th-century London, many industries thwarted attempts by successive governments to clean up the capital's air. Often they would simply refuse to install smoke purifiers on their factory chimneys, blaming the smoke from household fires instead.

Moreover, the fines on violators were often so small that they could not serve as a deterrent. Magistrates had sympathy for the industrialists, especially the smaller ones, who could not afford to convert their furnaces to more efficient, cleaner models. And, above all, smoke from industrial chimneys represented jobs and growth - which, in turn, gave people wages with which they could afford a fire at home, thus exacerbating the problem.

There was a cultural component, too. The British were wedded to their open fires. Closed stoves, popular throughout much of Europe, especially in Germany, were shunned by Londoners. During World War I, Britons were exhorted, in the words of the famous song, to "keep the home fires burning". Politicians were simply not willing to risk unpopularity by forcing Londoners to stop using coal and go over to gas or electric heating instead. In Britain today, in an echo of these earlier concerns, the government is cutting subsidies for onshore wind and solar farms, anxious not to offend voters in rural areas where such facilities would be built.

It took a disaster to force London to change direction. In 1952, a "great killer fog" lasted five days and killed an estimated 4,000 people. In a Britain trying to turn a corner after the death and destruction of the Blitz, this was unacceptable. A Clean Air Act was passed in 1956, forcing Londoners to burn smokeless fuel or switch to gas or electricity, power sources that had become much cheaper as these industries expanded.

Legislation for clean air was taken up by many politicians, but perhaps the most surprising was the extravagantly mustachioed Conservative politician Gerald Nabarro, whose flamboyantly expressed opinions included the retention of capital punishment, opposition to European integration and strident racism. But it was Sir Gerald who sponsored the 1956 act. More surprisingly still, it was Mr Robert Maxwell, the Czechoslovakian-born British media mogul and Labour member of Parliament, who pushed through further legislation in 1968 to strengthen the provisions of the previous Bill. His dubious financial transactions may have earned him the nickname "the bouncing Czech", but in this instance, he performed a genuine public service.

The 1956 Act took a long time to become effective, but it worked: Another great yellow fog in 1962 was the last. Since then, despite the belief in some parts of the world - not least the United States - that there are still foggy days in London town, pea soupers have become a thing of the past.

And yet, after several decades of cleaner air, Britain seems to be sliding back. Motor vehicles are now the main cause of air pollution and campaigners are trying to create some urgency around the debate to reduce car emissions. But people are as wedded to cars now as they were tied to their open fires a century or more ago. Will another eccentric British politician take up the mantle?

Mr Johnson is certainly eccentric, but he has vehemently denied reports about London's increasing pollution. "Ludicrous urban myth," he wrote on Twitter. "London air qual better than Paris and many other Euro cities - and go to Beijing or Mexico City." He later backed off from his statement somewhat, but he pared back London's planned Ultra Low Emissions Zone and put off any effective action until 2020.

Empty promises, delays and evasions are reactions that many of London's earlier clean-air campaigners would have recognised only too well. If a city like London can't control its air quality, what hope is there for Beijing or Mexico City, or indeed the rest of the world's rapidly growing cities? Great fogs may not come back to England, but it's unlikely that the world has seen its last pea souper.

NEW YORK TIMES

• The writer is a senior member of Wolfson College, Cambridge University and the author of London Fog: A Biography.