‘Missing’ India Air Pollution Data Restored to WHO Air Quality Database 
Pollution in Delhi peaks in late autumn when drifting emissions from crop burning exacerbate the usual urban household, traffic and industrial sources

India’s air quality data, removed at the last minute from the WHO Air Quality database update just prior to its launch two weeks ago, has been restored again to the online repository

The omission of data from dozens of cities in one of the world’s most polluted nations went unnoticed by major media until it was reported last week by Health Policy Watch.

At the time, WHO sources denied that any pressure had been applied by the Indian government to suppress or alter the data.  Rather, the India data was deleted from the online database so as to perform a final data check that was somehow overlooked in the lead-up to the launch. 

“The World Health Organization, after a thorough review, have now included the Indian cities, and have taken immediate steps to update this on its WHO web site, and in the database,” a senior WHO scientist told Health Policy Watch

WHO’s belated inclusion of Indian cities to its 2022 update covering air quality in 6,000 cities and settlements around the world, was noted Tuesday by Indian media and air quality advocates:

“Indian cities have finally been added by @WHO to its latest #airpollution report. Nine of the top 15 most polluted places are in India in the last 3 years,” tweeted Chetan Bhattacharji, senior managing editor at India’s NDTV station.  

“After several phone calls and emails, the mystery remains unsolved, but at least the data is back,” said the non-profit group Care for Air. “Data transparency is data democracy. And transparency precedes awareness and action.”  

The data still reveals a glum national situation for India. Although Lahore, Pakistan; Kabul, Afghanistan and Hetian Shi, China rank as the three most polluted cities in the world, they are closely followed by eight Indian urban centres – Delhi included.  

Air Pollution value for Delhi unchanged, but some others reflect refinements  

PM2.5 values for Delhi and a number of other major cities were largely unchanged in the final, published WHO data set, as compared to the embargoed version of the data, which was dropped at the last minute from the WHO 2022 database launch on 4 April, but published by Health Policy Watch last week. 

Comparisons of values for major Indian cities in the 31 March, embargoed WHO database and the final dataset released on 19 April. (Health Policy Watch compilation from WHO datasets)

The now updated Indian dataset does include other significant technical refinements. For instance, data for large Indian cities from the Indian government’s Central Pollution Control Board (CPCB), the statutory authority responsible for monitoring air quality is now incorporated more fully.  

Previously, data for Delhi and a number of other large Indian cities had been attributed only to the US AirNow programme, which monitors air quality from its missions and embassies around the world – but is not an official government data source. 

In a few cases, the final inclusion of the CPCB data actually led WHO to report on higher pollution values.  

For instance, in Agra, the annual average of PM 2.5 air pollution concentrations for 2019 was 109.67 µg/m3 – about 17% higher than the 91 µg/m3 value included in the embargoed dataset. The final data also includes more CPCB monitoring points – covering some 85% of the city. 

Other corrections included the elimination of duplication in the Indian names Bangalore (British spelling) and Bengaluru (Indian) – with the British spelling chosen as the reference. Data from Haryana, the Indian state that surrounds Delhi on three sides, was deleted. While that is presumably because Haryana is a state and not a city, that reduces valuable perspective of air quality in a strategically important farm area – where smoke from rice stalk burning drives heavy pollution into Delhi in the late autumn. 

WHO-led BreatheLife campaign site offers an interactive search experience for air pollution data from cities globally. Here, results  for Delhi – along with estimated deaths/year in India from air pollution.

WHO database ‘not designed to derive trends’ in developing cities over time  

Although WHO’s air quality database was a bold move for the global health agency when it was first established over a decade ago – one significant limitation of WHO’s urban air pollution reporting today is the lack of analysis of trends in major cities over time.  WHO produces no such analysis for cities – even though more than a decade’s worth of ground station monitoring data is now available. 

“The WHO database has never been intended to derive trends,” in the cities that it tracks over time, the WHO scientist told Health Policy Watch

“Even with the historical data that is included, it is difficult to do such type of analyses for many reasons (based on the same limitations highlighted for intercity comparisons).” 

Nonetheless, other global experts are indeed looking at trends at national and urban level – and particularly in large cities seen as drivers of change, both good and bad. 

One example is a paper on trends in developing country megacities, published on 8 April in Science AdvancesIt concluded that rising air pollution levels are driving a rise in air pollution-related mortality in African and South Asian megacities – where policymaker action on polluting vehicles, urban sprawl, home and power plant emissions – has been slow, if it happens at all.  

That analysis, which also references satellite sources, notes that observations of Aerosol Optical Depth (AOD) values reflect growing PM2.5 pollution in South Asian cities over the past decade. AOD is the level at which aerosols prevent light traveling through the atmosphere and is thus an indicator of PM2.5 concentrations. 

“Trends in AOD from 2005 to 2018 in South Asian cities are steep (2.5 to 7.8% a−1) and significant. AOD more than doubles in Bangalore (7.8% a−1) and Hyderabad (7.3% a−1),” report the authors from University College London, Harvard School of Public Health, the University of Birmingham and University of Brussels.  

“Earlier studies have reported similar positive trends for these cities, so our contemporary record supports sustained rapid growth in AOD (and thus PM2.5),” the authors say, adding that: 

“Desert dust likely does not contribute to trends in AOD over South Asian cities, as desert dust optical depth has declined over the Thar Desert and makes a negligible contribution to AOD trends across the rest of India.”  

Increase in premature deaths due to increase in exposure to PM2.5 in rapidly growing tropical cities. Bars give the increase in premature mortality in 2018 relative to 2005 for the top 15 cities, colored by the percentage point change in fraction of premature deaths attributable to exposure to PM2.5. Inset value is the total for the cities in Fig. 1 with detectable trends in AOD. (Science Advances)

Politicians in Asia and Africa also have often tried to blame high air pollution levels on either natural dust or biomass burning, related to household cooking, charcoal production or wildfires. 

However, the Science Advances article draws out multiple lines of evidence suggesting that other “anthropogenic” sources from vehicles, energy production and industry represent a growing piece of the pollution puzzle.

Notably, six African cities including Abuja, Ibadan and Conakry Nigeria, have exhibited “very steep increases in anthropogenic activity NO2” the authors note, referring to another health-harmful air pollutant, nitrogen dioxide closely associated with vehicle emissions. NO2 levels are rising at time when biomass burning, a traditionally prominent source of air pollution in Africa, is on the decline, the authors note.    

WHO planning global trends analysis update 

Along with avoiding trend analysis, WHO has discouraged using the data to make comparisons between cities – saying it’s main message is to encourage better monitoring altogether.

While it’s true that considerable technical inconsistencies in monitoring methods can make inter-city comparisons challenging, critics say that the real bigger barrier is political. As a member-state body, studies that lead to unflattering comparisons between member states puts WHO in an extraordinarily uncomfortable position.

WHO has in the past undertaken trend analyses – but with a focus more at the global or global and regional level. The latest such WHO paper, a hybrid analysis of both ground station monitoring and satellite data from 2010-2016, was published in Nature in 2020. It found that one-half of the world’s population are being exposed to increasing levels of air pollution. 

(Nature 2020) Graphic a: Average annual PM2.5 (μg/m3) Concentrations in 2016. b: Changes in PM2.5  concentrations 2010-2016 show South East Asia and Africa with the most rapid increases (in pink and red).

“We intend to publish an update of it, with the 2020 data early next year,” said the WHO scientist involved in the previous paper.  

In addition, the scientist added: “WHO has recently established a Global Air Pollution and Health Technical Advisory Group (TAG) which brings together over eighty of the top experts on the health and air pollution, working to better quantify the health risk from air pollution, and to provide guidance on quantifying the costs and benefits of different interventions to tackle air pollution, among other [tasks]. 

“The TAG will advise and support WHO on the relevant analysis and trends to be developed.”

See the exclusive Health Policy Watch analysis of the database here:

EXCLUSIVE: WHO Deleted India’s Air Pollution Data from its New Air Quality Database – Why? 



Image Credits: Flickr, Compiled by Health Policy Watch from WHO data , Science Advances, April 2022 , Nature (2020).

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