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MID-AFTERNOON in Delhi, and a red blob looms in the haze. The sun barely illuminates the city. A yellow-green smog hangs low. Even indoors, fuzzy halos of dust and smoke surround lamps. Those foolish enough to be out jogging, or compelled to stand at junctions directing traffic, complain of shortness of breath, migraines, clogged lungs. Newspapers are crammed with articles about asthma, wheezing children at clinics, an epidemic of grumpiness and gloom, the frail and elderly falling victim to an annual—and worsening—scourge: Delhi’s winter pea-soupers.

By one estimate the Delhi smog kills 10,500 people a year: smog can trigger heart or asthma attacks, particulate matter causes cancer. Like just about every big Asian city that has grown fast, with only a passing concern for environmental standards, its air is wretched. Official data prove it so. India’s minister for the environment, Jayanthi Natarajan, said so explicitly before parliament in March, explaining that India sets national standards for various nasty pollutants, and monitors for them in 216 towns and cities.

For Delhi, between 2001 and 2010, there was one bright light. The annual average level of sulphur dioxide fell from 14 micrograms per cubic meter to just five. For that Dilliwallahs should thank improvements in transport: a court order roughly a decade ago compelled some 100,000 buses, taxis and auto-rickshaws to switch from running on diesel to compressed natural gas; a successful metro network has been rolled out; a ban on lorries from Delhi’s roads is reasonably well enforced, between 6am and 9pm.

On other scores, matters are much worse. Levels of nitrogen oxide almost doubled over the same period, from 29 micrograms to 55, on average. A measure of particulate matter known as PM10 (any dust with a diameter less than 10 micrometres) has also more than doubled, from 120 to 261, way above the prescribed limit of 100. Keep in mind, too, that pollution is relatively low in the blazing summer months, and during the monsoon. In the winter, by contrast, truly terrifying levels lift the annual average. A glance at the website of a Delhi government agency on November 5th, for example, showed the PM10 level at 749, more than seven times over the safe limit. And for more dangerous tiny particles, known as PM2.5, the agreed safe limit is 60, whereas the official Delhi site reported a level of 489, over eight times too high.

Such statistics are not really needed. Rub your skin after a short walk outside and your fingers are left coated with black smudges. As the worst of the smog appears,it becomes riskier than ever to drive or walk on chaotic roads as visibility falls to just a few metres. Come the new year, Delhi’s airport is battered by delays as fog and smog, usually in the morning, slow the departure and arrival of aircraft. The huge annual festival of Diwali—to be celebrated on November 13th this year—sees a series of immense, deafening and beautiful firework displays, which leave sulphur and gunpowder smoke choking the air for days.

Add to that the impact of the huge bonfires of waste, post-harvest. A striking picture just released by NASA shows thousands of orange dots, blazes that give off the smoke and smog that gathers across much of north India and then sits unmoving as temperatures drop and air pressure—an “inversion”—holds everything still. It is as if a greenhouse is erected above Delhi, to catch and contain the swirling brown exhaust from cars, smoke from oily fires, along with dust and industrial fumes. Right now, too, meteorologists say a distant cyclone, off the east coast of India, has left extra moisture over the northern plains, which has helped to make the smog even denser.

By some measures, Delhi’s rotten air, at least at the worst time of year, competes with the most gasp-inducing of all. One ranking (by UN Habitat) of carbon-dioxide levels, indoor pollution and PM10, suggests its air is worse even than that in Beijing, China’s capital. Residents there may beg to differ, saying their own smogs are worse yet. Even if, on average around the year, some other cities are arguably even worse—Karachi in Pakistan and Dhaka in Bangladesh look particularly dire—it is a miserable competition to join.

What could be done? Getting away from the city makes good sense: Kashmir is rather nice at this time of year. Individuals are told they may protect themselves a bit, for example by hiding indoors, keeping doors and windows closed and using air filters. General advice against exercising outdoors at least gives couch potatoes an excuse to put off keep-fit regimes for another few months.

For Delhi, a series of other measures make sense. Perhaps a fifth of all the pollution in the city is still caused by traffic, notably from diesel cars. Scrapping subsidies on diesel might help, for example by pushing more people on to public transport or at least into more efficient vehicles. The metro is now some 180km long, and is rather good, but it could be expanded further. Lots more buses, and bus lanes, would be useful too.

Beyond vehicle emissions, there are other causes of woe aplenty, as well described by Sarath Guttikunda of the Indian Institute of Technology, Delhi in a recent study. He notes for example that some 1,000 brick kilns surround Delhi, serving its construction boom, baking bricks by burning coal, wood and other organic smoky stuff. Such kilns are traditional, inefficient and dirty. Converting these to something cleaner—or moving them farther away—would surely help.

Similarly coal- and oil-fired power stations near Delhi have, over the years, been converted to gas or moved away. Six power plants remain near the city, but as the general power grid fails repeatedly, wealthy residents, hospitals and businesses turn increasingly to diesel-generators in the city centre, points out Mr Guttikunda. Making the grid more reliable, therefore, would cut the use of such stinky and noisy machines. Paving more roads would lessen the amount of dust (a big portion of PM10) thrown up into the air, while a ban on burning rubbish would cut the oily particles, and so on.

The lesson from the court-ordered transport switch is that official intervention, and proper monitoring, can bring direct and most welcome improvements. It helps, too, that the rich, aside from fleeing, can hardly breathe different air from the poor; thus almost everyone should have a strong interest in doing something to improve matters. Delhi, after all, is gasping for a change.