Far away in Beijing, once the global capital of air pollution, the skies are clear and PM 2.5 levels are less than one-fifth of Delhi’s. The story is similar in other erstwhile polluted metropolises — Paris, London, and Los Angeles. Despite their differences and unique conditions, cities that have successfully dealt with the problem provide a useful template to consider. Here’s what they got right.

Firstly, in these cities, the need to address air pollution found resonance among people, elevating it to a matter of political significance which, in turn, led to ambitious policymaking. For example, following public outcry over the issue in 2013 in China, the Premier Li Keqiang said in 2014, “We will resolutely declare war against pollution as we declared war against poverty.” In a short period of time, cities replaced coal heaters and moved polluting industries away from densely populated areas. The political momentum led to action across the administrative setup.

Secondly, cities that addressed the issue adopted scientific approaches to addressing the problem. While Indian institutions also tend to be aligned with mainstream science while dealing with air pollution, it is vital to increase capacity and capabilities to monitor, track and implement measures. Improved funding of scientific bodies can go a long way in real-time information gathering that can help address the issue more effectively.

Most Indian cities either don’t have studies that reveal the sources of air pollution, or have sporadically conducted ones, as is the case with Delhi. This will need to change. Initiatives such as Delhi’s Real-Time Source Apportionment System that involves IITs and other specialised institutions can help provide much-needed data but will need to quickly get off the ground and be replicated in other cities. Such investments should be strongly preferred over smog towers that are proven to be ineffective. For instance, pollutants were barely 14% lower when measured 100 feet away from the smog tower in Connaught Place in Delhi, which would have no measurable health benefits to passersby.

Thirdly, countries adopted cohesive policies and empowered relevant institutions to implement them. In the early 1940s, just as Los Angeles was realising it had a pollution problem, the city created the first-ever institutions in the country to monitor and address the problem and gave them the authority needed to act. In India, there are several institutions that are meant to tackle several aspects of the problem but lack cohesion. Furthermore, state pollution control boards lack the trained workforce and funding needed to implement existing policies.

Fourthly, cities such as Paris have been successfully addressing the air pollution issue by adopting people-centric approaches to city design, focusing on walkable and cyclable cities, dense public transport, and accessible public infrastructure. Appropriate zoning regulation, electrifying freight transport fleets and public transport can go a long way in reducing transport-related pollutants that are a major contributor to Delhi’s poor air quality.

Finally, cities that successfully reduced air pollution did not rely on band-aid solutions like watering streets using fire trucks, and focused instead on transformative changes to key contributing sectors. In Delhi’s case, while all contributing sectors will need attention, there is an urgent need for structural change in agricultural practices particularly for its outsized role in the winters.

Not only is Delhi’s smog crisis an annually recurring one, poor air quality itself is a perennial issue. As India seeks to build the metropolises of tomorrow, air quality will need to be central to it. While the success stories around the world provide a useful template of sound principles, India’s air pollution fight is ultimately its own, requiring unique solutions to its unique challenges.

Now, the caveats. While air pollution is caused by a range of sources — especially polluting factories and vehicles — a few factors stand out that might be distinctive to each city. For example, Beijing’s coal-fired heating systems in buildings were a major contributor to its poor air quality. In Delhi, while a multiplicity of sources contribute to air pollution throughout the year, stubble burning aggravates the problem at the onset of the winter every year, contributing to up to half of the city’s pollutants on certain days.

Another facet that differentiates the situation in cities is the geographic and meteorological reality, which is an important determinant of air quality. Los Angeles and Beijing are located in basins surrounded by higher altitude areas that trap air pollutants over the city. Delhi is situated in the plains, but for India’s Gangetic plains as a whole, the Himalayas prove to be a barrier that helps trap pollutants over the region. This is especially true in the winter as the wind direction changes and colder temperatures contribute to particulate matter being unable to escape easily.

For this reason, it is vital to understand air pollution not as an urban issue, but as an issue that concerns any “airshed”, which is an area where the unique topography and meteorology ensure that one cannot simply focus on the air above a city without thinking about the region as a whole. In the airshed to which Delhi belongs, it is not only urban sources that contribute to air quality, but also farm fires, dust storms that originate elsewhere, brick kilns that are hundreds of kilometres away, and so on. Cleaning Delhi’s air necessitates addressing air quality in much of India’s northern and Gangetic plains, leading to far-reaching benefits to hundreds of millions of people who reside in the region.

Siddharth Singh is the author of ‘The Great Smog of India’