When i walk or cycle through Delhi i see a growing city grappling, as cities across the world have done, with the challenges growth brings.It is crowded, yes, but that is because it provides jobs and homes to millions from surrounding states looking for an opportunity to better their lives.

It is dirty and unsanitary in parts, because it takes time for overwhelmed city authorities to catch up with providing services to the millions who arrive here.And while we foreigners have the luxury of opting out and returning to our own cities, the residents of Delhi, especially the poor, have no such option and continue to face the impact of air pollution.

Urban air pollution is a knotty issue in today's emission-generating world.Several metropolises are struggling to deal with it. The levels of pollution in Delhi are different - because the scale is different. Paris city has less than 3 million people; Delhi more than 16 million and growing daily. London has 2.6 million private vehicles and Delhi over 4 million.

And none has its particular problems - like the 80,000 trucks that rumble through Delhi each evening, bringing in and taking out goods needed for daily life but also spewing noxious fumes into the night. Or the fact that its airshed is inextricably linked to that of the neighbouring states of Haryana and Punjab, where the burning of agricultural waste in early winter adds to the pall of smoke that hangs over the city. Or even the reality that countless poor households in the city do not have access to clean fuels, and still depend on wood or coal fires to cook their food or keep warm in winter.

It is now time to focus on solutions.Certain principles will need to drive this campaign. First, any air quality management effort must cover not only Delhi but the entire National Capital Region; otherwise efforts in one part will be negated by pollution from another. NCR needs to develop a comprehensive air quality management plan that includes a mapping of pollution sources, monitoring levels of air pollution, as well as a rigorous assessment of the costs and benefits of different mitigation measures.

But even while this comprehensive management plan is being prepared, what are measures that can be implemented immediately to address air quality? We know for instance that the major sources of PM2.5 - which is the most harmful to human health - are emissions from the transport sector, residential sources and the industrial sector in that general order.

Besides the tens of thousands of commercial vehicles that ply in NCR or even pass through it, it is the alarming number of personal vehicles - 1,500 are registered in Delhi alone every day - that add to the city's pollution load. We are also familiar with the political economy issues around the adoption of cleaner fuels and cleaner technologies for vehicles. But even as we wait for the government to resolve these and decide to leapfrog to higher standards at par with the best in the world, there are quick solutions available.

Many of these are well known too - build long-awaited bypasses that will allow transiting trucks to proceed without entering Delhi, enhance public transport in NCR including last-mile connectivity, and strengthen `pollution-under-control' monitoring systems for all vehicles.

Less is known about the next biggest source of emissions in Delhi - the numerous hotel and restaurants, street vendors and households that do not have access to clean fuel. One recent assessment suggests that 27% PM2.5 emissions in NCR comes from traditional fuels (coal, wood, kerosene) used for cooking, and another 24% from coal-dominated energy consumption in industry.

Every city that has cleaned up its air pollution has done it by moving households and industry to cleaner fuels. In several cities of northern China, moving to gasbased heating systems has helped bring down PM2.5 concentration substantively and cost-effectively. One action that governments responsible for the NCR region could take is to switch every source of residential and industrial emissions to gas.

The Delhi government is already committed to providing residential piped gas, which would be a major contribution to this anti-pollution programme. But it would require other states in NCR to put in place similar policies for the gains not to be frittered away .

Similarly, monitoring networks across NCR, to supplement those in Delhi city, need to be set up now so that information about pollution is available in real time (including crowd-sourced information as we now have for traffic snarls) and authorities can respond nimbly to pollution peaks, perhaps using the information to curb cars or control certain manufacturing activities on a bad-air day.

Ultimately, Delhi's air pollution challenge is only one facet of India's urban renewal challenge. With about 600 million Indians expected to live in urban areas by 2031, India's cities need to find better ways of managing their waste, to construct buildings that are energy efficient, and plan spatial growth in a manner that makes for a more compact, more resource-efficient cities. And they need efficient, inclusive and safe urban transport. Motivated by its air pollution challenge, the entire NCR could show the way to the nation and move towards becoming a true 'smart' city.