THROUGHOUT its steep climb away from Delhi, the plane remained enveloped in an acrid fug. It was not until it reached cruising altitude that sunlight could break through. Off to the north, tickling an achingly blue sky, the pristine pinnacles of the Himalayas whispered a promise of fresh air. But as the aircraft crested the lip of the jagged bowl that cradles Kathmandu, the fabled capital of Nepal looked less like Shangri-La than like a giant curdled cappuccino. The plane descended into a yellow-brown smear that stretched clear across the valley, thick enough at the centre to blur away streets and buildings entirely.

Kathmandu is far smaller than Delhi, and the ingredients in its noxious halo are different. The cocktail at this dry time of year is mostly plain old dust. Stirred by swarms of motorbikes bumping over potholes, and through builders’ heaps of sand, gravel and cement made ubiquitous by the devastating earthquake of 2015, the permanent choking cloud blots out stars in the night sky. Though close by, the world’s highest mountains make only a brief appearance as tantalising wisps in the early morning before vanishing into the murk.

Delhi’s autumnal pollution is of a more dangerous kind. Its 25m people suffer under a seasonal plague that afflicts the Indo-Gangetic Plain from the city of Lucknow in the east all the way to Lahore, in Pakistan, to the west, as millions of rice farmers conclude their harvest by burning off the leftover stalks to clear paddies for winter planting. Add to this Delhi’s unique mix of spices: ash spewed out of coal-fired power plants, fine grit from dirty diesel engines, exhaust from generators running on the cheapest bunker and coking fuels, fumes from crematoria and malodorous miasmas from spontaneously combusting trash mountains. All this gets chucked up into the air where, in early November, rising humidity combines with falling temperatures and an almost complete lack of wind to produce a clammy, smelly suspension of ultrafine toxic dust. It hangs over the city like congealed smoke.

Yet if the chemical components and proximate causes of air pollution across South Asia are different, the ultimate source is the same: poor governance. It is not that political bosses have uniformly failed to recognise the dangers of air pollution, or taken no steps to curb it. Across the region they have done both. Delhi, for instance, converted all its buses to cleaner natural gas 15 years ago. But governments have for years dealt with the issue haphazardly, half-heartedly and with all the shortcomings in state capacity that put Asia’s underbelly to shame compared with the continent’s less democratic but more efficient countries. Delhi has become the world’s most polluted mega-city, supplanting Beijing.

Indeed, the contrast with China is stark. For nearly a decade its government has exerted a massive, concerted effort to tackle pollution, with encouraging results. In Beijing the average level of PM 2.5, the finest and most dangerous sort of dust, fell by about 20% between 2012 and 2016. Greenpeace, an environmental pressure group, reckons that around 160,000 premature deaths have been avoided as a result. NASA, America’s space agency, reckons that China’s emissions of sulphur dioxide have fallen by 75% since 2007. India’s grew by 50% over the same period, largely as a result of building ever more coal-fired power stations and failing to equip old ones with filters.

India is not alone among its neighbours in being so neglectful. Pakistan has also made a big, controversial push for coal. Just like Delhi, Lahore has flailed feebly at tackling toxic air. Only when public anger over the stink mounted in recent weeks did the city government reveal that it had bought six pollution monitors some time ago, but had not yet installed them. As in India, Pakistan’s state governments have been wary of forcing farmers, a crucial vote bank, to curb their pyromania.

In Nepal, meanwhile, it is not poverty so much as delays in disbursing budgets, compounded by an anti-corruption agency that terrifies bureaucrats, that is largely responsible for the failure to pave streets. Ignoring evidence that diesel exhaust is carcinogenic, and keen to placate the truckers and farmers who use it most, the government has maintained a steep price differential: petrol costs 30% more. In any case, lack of sufficient oversight means that petrol and diesel alike are often heavily adulterated with even dirtier stuff by the time they reach consumers.

For decades India has maintained a similar pro-diesel policy, promoting a shift by consumers and carmakers such that, by 2013, some 55% of cars registered had diesel engines. In Delhi diesel accounts for 78% of the PM 2.5 produced by cars. The International Council on Clean Transportation reckons this could potentially translate into an additional 284,600 cases of lung cancer a year. Overall, perhaps as many as 2.5m people in India die prematurely every year owing in part to air pollution.

The elephant in the smog-filled room

Yet despite gasps and cries from the public, and stark warnings from doctors, the national government remains strangely aloof. The prime minister, Narendra Modi, loudly promotes a Clean India campaign aimed at building toilets and tidying streets. But he has shied from broaching the electorally trickier question of air pollution, which is hard to fix and risks treading on the toes of both big industry and small farmers. His environment minister, Harsh Vardan, airily waves off suggestions that anyone might actually be dying from air pollution.

This is foolish. India does not even need to look to China to see what can be done. Inadvertently, for instance, another of Mr Modi’s projects, promoting cooking gas to replace traditional stoves that burned wood or dung, is saving thousands of lives previously shortened by indoor pollution. Up in the terraced hills of Nepal, meanwhile, farmers can teach their peers down on the plains a lesson. They do not burn off rice straw. They carefully dry and stack it, feeding the hay to cows and buffaloes all winter.