Air quality in India’s northeast States is worsening and while still much better than pollution hotspots in other parts of the country, appear to be under threat by the same sources — vehicles, industry and urbanisation — that have soiled the air elsewhere, according to an analysis of air quality by the Delhi-based Centre for Science and Environment.
So far air pollution is largely seen as a crisis of the Indo Gangetic plains, particularly in winter when Delhi and several cities in Uttar Pradesh and Haryana find themselves in lists of the world’s most polluted cities. Air in the northeast States, in the popular imagination, is less befouled due to the region's topography that is less conducive to fossil-fuel led industrialisation and geographical isolation.
CSE analysed concentrations of PM 2.5, particulate matter sized 2.5 micron or less, from January 1, 2019 to December 7, 2021 in Assam, Meghalaya, Tripura, Nagaland, Mizoram, and Arunachal Pradesh over annual and seasonal periods. They relied on live data available from seven continuous ambient air quality monitoring stations (CAAQMS) spread across six cities in five States: two stations in Guwahati and one station each in Shillong (Meghalaya), Agartala (Tripura), Kohima (Nagaland), Aizawl (Mizoram) and Naharlagun (Arunachal Pradesh).
The number of air quality monitors in the Northeast are few and have been installed in the last two years unlike those in many cities in India. This, therefore, gives only a limited picture of the variability and scale of air pollution.
What CSE found was that the annual, average PM 2.5 levels of Guwahati in 2021 (as of November 30) was 60 microgram per cubic metre (μg/m3) which was less than that in 2020 (62 μg/m3) but more than in 2019 (56 μg/m3). India's upper limit for PM 2.5 is 40 μg/m3.
Agartala, readings for which were available only for 2021, had an annual concentration of 45 μg/m3 whereas Shillong, Kohima and Naharlagun were below the 40-mark.
Shillong was the only other city in the region with a station generating data for over two years but “due to poor data availability its annual averages could not be considered credible,” the researchers noted, “Aizawl and Naharlagun do not meet the minimum data availability requirement but the limited data available indicates that these two would most probably be meeting the annual standard.”
These air quality figures are a far cry from those recorded in cities in the Indo Gangetic Plains, where annual concentrations are in triple digits but Guwahati has increasingly been sending concerning signals. Until November end, the number of days with air quality in ‘very poor’ or ‘severe’ category stands at 54 days in Guwahati city which is “comparable to cities of North India” and in other cities 'good' and 'satisfactory' days dominate but poor and very poor days had begun to emerge. Agartala registered 10 ‘very poor’ days while Kohima had two ‘very poor’ days. Good, satisfactory and very poor refer to degrees of PM 2.5 concentrations.
Except Guwahati, rest of the cities in the States in the Northeast have low annual PM2.5 levels but during winter, episodes of high pollution were common, the study noted. Weekly PM2.5 levels could go as high as 189 μg/m3 in Guwahati. This winter, so far, the highest weekly level has been reported from Agartala when it hit 91 μg/m3. Last winter it had gone up to 112 μg/m3. Similarly, high pollution has been recorded in Aizawl and Kohima.
“The current obsession with high pollution concentration in the Indo-Gangetic Plain and in overall northern India overshadows and side-lines the early signs of the crisis in our north-eastern states in the national discourse on air pollution and public health. Weak and inadequate air quality monitoring and paucity of data do not allow proper assessment of the risk. But even the limited evidence shows several cities — especially the state capitals — are already vulnerable to poor air quality and winter smog,” Anumita Roychowdhury, Executive director, Research and Advocacy, CSE, said in a statement. “Cities of north-eastern states need urgent attention...to cut pollution from growing motorisation and congestion, use of solid fuels and open burning, and dispersed industrial sources at the early stages to prevent worsening of the public health crisis in this ecologically vulnerable region.”
