In Delhi: A seasonal villain

Early last winter I went trekking in the Himalayas, in search of clean air and the crystal silence of the mountains. Within a day, I had found what I was looking for: verdant hill villages where the air tasted of freshly trodden grass and the woody aroma of the deodar.

What seemed like time travel into a pre-modern world lasted only a week, however.

On the way back to New Delhi, I ran smack into the realities of city life even before reaching it: A mile- long traffic jam from a highway pile-up caused by low visibility, typical of a seasonal villain in India's capital and its suburbs - smog.

New Delhi's air is wretched, and in no other season is this fact more obvious than in winter.

Residents find themselves choking on a blanket of acrid smoke and pollution. The smog almost blanks out the sun, covering the city in a steely grey haze. Visibility is reduced to a few metres early in the morning and at night.

Sniffing, wheezing, coughing, some 10,000 people are said to die of respiratory ailments linked to smog every year.

For a time, New Delhi's air visibly improved after the government forced public transport vehicles to convert from diesel to compressed natural gas. But those gains were lost as the city of 20 million people grew.

In the decade to 2010, the average level of nitrogen oxide almost doubled, from 29 micrograms to 55 micrograms. The level of particulate matter called PM10 also more than doubled, from 120 micrograms per cubic metre to 261, way above the prescribed limit of 100.

Last year was particularly bad: The PM10 count peaked at 908 micrograms per cubic metre. The city reported the PM2.5 count, the more dangerous tiny particles, had reached 489 at one point, against a safe level of 60.

"This is like a ding-dong battle," Ms Sheila Dikshit, the chief minister of the state of New Delhi, told reporters last year. "We catch up with something; the pressures catch up more than that."

The summers are relatively better, by New Delhi pollution standards, with average PM10 levels between 140 and 165 - making it still among the worst in the world.

What is responsible for the smog here is a topic of ongoing debate.

Conventional wisdom blames growth with little concern for the environment.

For example, New Delhi has seven million vehicles and adds about 1,000 more a week.

There is also pollution from nearby industrial towns and farmlands burning rice straw after harvest.

But some experts say the city's smog problem is not solely caused by increased emissions from vehicles. They blame a weather phenomenon called "inversion".

In this, fog traps pollutants and, in the absence of wind to blow the haze away, hangs over the city like it would in an unventilated room.

For hapless Delhites like myself, the annual hike up the mountains is as close as one gets to recovering from the stresses of city life. Or for a brief escape from the dreaded winter smog.

Even if that means risking the freezing cold of the Himalayas.