The Central Pollution Control Board — an Environment Ministry organisation that sets guidelines for monitoring and controlling pollution — says international studies linking air quality in India to disease and death are flawed because “…the ethologic, personnel immunity (sic) and demography of India are incomparable with international practices.”

Bodies such as the World Health Organization (WHO) used “arbitrary conversion factors [to measure the prevalence of different pollutants]” to rank cities for air quality, the CPCB alleged in an internal newsletter published in November 2016 but not made public.

The publication, called Matter-Fine Particulate: An Environmental Challenge, is a guide to understanding the genesis, prevalence, sources and health effect of extremely small particles of dust that can result from a wide range of causes including road dust, domestic cooking and fossil fuel burning.

The size of these particles determines the ease with which they can be lodged within the body. Those smaller than 2.5 micron (PM2.5) are generally implicated for respiratory and cardiovascular ailments.

Reacting, last week, to reports that air pollution killed 1.1 million Indians in 2015, Environment Minister Anil Dave told a press conference, “We seem to be far more influenced by things out of India. We have several of our own organisations and experts…and I trust them as much as I do our Army.” While acknowledging that PM2.5 pollution was a problem, no Indian agency has quantified death and disease due to air pollution in India. On the other hand, other than disavowing mortality figures, the government has also never officially disputed any international report on how they measured pollution numbers for Indian cities.

In its most recent update in 2016, the WHO said that 10 of the 20 most polluted cities in the world were in India, whose air quality standards require that the daily PM 2.5 averages not exceed 60 mg/cubic metre and 40 mg/cubic metre annually.

The WHO arrived at its figures by collecting 24-hour and annual average of PM 10 and PM 2.5 of cities from government websites and, when it didn’t have figures for PM 2.5, used a constant number to convert from PM 10 measurements. Of the 124 Indian cities, whose pollution figures are available in the WHO database, only 8 had direct PM 2.5 measurements.

According to the CPCB publication — by far the only available government critique of this methodology — this conversion is problematic as air quality monitoring machines varied widely in their measurements even within the same city. In some cases PM2.5 was only 8% of PM 10 and other cases 86%, according to a 2014 assessment of air quality parameters in Delhi by the CPCB. “The average thus works out to about 47%,” D. Saha of the CPCB and one of the authors of the report told The Hindu.