In early 2015, the World Health Organisation released its annual Ambient Air Pollution Database, which catalogues levels of particulate matter (PM 2.5 and PM 10) across 91 countries and 1,600 cities, ranking them on the basis of annual average ambient concentration of both pollutants.

The database placed 13 Indian cities in the top 20 most polluted around the world, ranking Delhi first in terms of annual average concentration of PM2.5 – which is particulate matter less than 2.5 microns in diameter, or about 30 times finer than a human hair – the more harmful of the two pollutants.

This ranking triggered a period of sustained media coverage of the deplorable air quality in the national capital, along with a series of feverish repudiations from policymakers with objections raised regarding the validity of the data and the methodology employed. Articles reporting on Yale University’s Environmental Performance Index the previous year, which ranked India as worse off than China and several of its South Asian neighbours, triggered a similar debate that quickly disintegrated into a Delhi vs Beijing squabble.

During both years, as with reporting on the latest World Health Organisation Ambient Air Pollution database earlier this year, the media as well as the general public, completely lost sight of the bigger picture. The spotlight in each case was reserved exclusively for Delhi, given its centrality in the Indian media and political discourse, with little attention provided to the broader message being conveyed by either the environmental performance index or the Ambient Air Pollution database, which is that the issue is regional in its influence, national in its import, and with severe implications for the health of the Indian citizenry.

Lack of data

The Ambient Air Pollution database exercise involves compiling data across multiple sources including data reported by national agencies, regional networks, UN agencies, other development agencies, and peer-reviewed literature. The vastness of the exercise and the sparseness of the monitoring, especially in a country like India, means that there is often a lack of data on either PM 10, or more often, PM 2.5.

This gap is plugged through national conversion factors that provide a reasonable proxy of the ambient concentrations. The lack of temporal coverage also ensures that a few readings collected through the year are averaged out to produce a picture that provides plausible deniability when questions are raised with policymakers. With these caveats in place, it is important to understand that the exercise remains useful in identifying hotspots for expanded monitoring, or regions that require urgent policy action.

The media and policymakers, while ignoring the above issue, committed the cardinal sin of focusing solely on Delhi in their narrative, ignoring the fact that in both instances, a dozen other Indian cities were listed alongside Delhi in the top 20, with ambient concentrations often in the same range. These included rapidly industrialising tier-2 and tier-3 cities such as Agra, Varanasi, Kanpur, Gwalior, Patna, Raipur and Ludhiana, many of which are earmarked to become smart cities as part of the government’s flagship urbanisation programme.

The big picture

If one were to take a step back and look at work done in satellite-based estimations of PM2.5, validated by ground monitoring data, the picture starts to look clearer. Taking off from the proverbial blind men and elephant tale, the focus on Delhi, even over the last few weeks, ensured ignorance of the vast swathe of the Indo-Gangetic plain which suffers exposures seven to 15 times above what the World Health Organisation deems safe.

Annual ambient air quality exposure in India.
Annual ambient air quality exposure in India.

The picture painted by satellite data shows us that the problem is in fact regional, with the inter-connectedness of the Indo-Gangetic plain ensuring that no action plan that ignores the states around Delhi will ever be successful in improving air quality. It also tells us that the focus now needs to extend beyond Delhi, which is quite well monitored, to these tier-2 and tier-3 towns where monitoring is sparse, awareness is non-existent, and accountability is virtually absent. Our own analysis of the data from the last year shows us that the annual variability of PM 2.5 of select cities in the Indo-Gangetic plain, in comparison with Delhi, is not very different, reaffirming the need for a regional multi-sectoral action plan, with focus on all sources of air pollution.

Comparison of air quality across four cities in the Indo-Gangetic plain for the period November 2015 to October 2016. (Source: Central Pollution Control Board.)
Comparison of air quality across four cities in the Indo-Gangetic plain for the period November 2015 to October 2016. (Source: Central Pollution Control Board.)

This exercise also shows us that the need for open and accessible air quality monitoring data in tier-2 and tier-3 cities is greater than ever. There are large gaps in the data sets from these cities, and given the lack of technical manpower in the State Pollution Control Boards, a high likelihood of calibration errors as well.

The Central Pollution Control Board’s move last year to also remove historical data from its website and to move towards a 24-hour rolling average for the Air Quality Index only makes the need for data from other sources more immediate. Ultimately, what ranking cities in India has resulted in is some form of action to alleviate the woes of Delhi residents, while ignoring the vast swathe of the Indian population that continues to suffer from alarming levels of air pollution exposure.

Bhargav Krishna manages the Centre for Environmental Health at the Public Health Foundation of India, and is a co-Founder of Care for Air. Kishore Kumar Madhipatla of the Public Health Foundation of India also contributed to this article.