The pollution level in the Northeast states has increased gradually over the last several years. Among other cities, Guwahati and Agartala are the most polluted.
A new analysis by the Centre for Science and Environment (CSE), the New Delhi-based think tank, says that the problem of air pollution is growing steadily in the Northeast region, putting paid to the impression of pristine blue skies and clean air that people usually have about this region.
“The current obsession with high pollution concentration in the Indo-Gangetic plains and in overall northern India overshadows and sidelines the early signs of the crisis in our northeastern states in the national discourse on air pollution and public health. Weak and inadequate air quality monitoring and paucity of data do not allow a 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,” says Anumita Roychowdhury, executive director, research and advocacy, CSE.
The study methodology
CSE has analysed the urban air quality status in the states of Assam, Meghalaya, Tripura, Nagaland, Mizoram, and Arunachal Pradesh. This is part of the air quality tracker initiative of the urban data analytics lab of CSE, which was initiated last winter. The objective of this new analysis is to understand the magnitude and trend in winter pollution in major cities of the region which have recently started real-time air quality monitoring.
This is an assessment of annual and seasonal trends in PM2.5 concentration for the period January 1, 2019, to December 7, 2021. This analysis is based on the real-time data available from currently functioning air quality monitoring stations in the northeast. A huge volume of data points have been cleaned and data gaps have been addressed based on the USEPA (the United States Environmental Protection Agency) method.
This analysis covers seven continuous ambient air quality monitoring stations (CAAQMS) spread across six cities in an equal number of states: two stations in Guwahati (Assam) and one station each in Shillong (Meghalaya), Agartala (Tripura), Kohima (Nagaland), Aizwal (Mizoram) and Naharlagun (Arunachal Pradesh).
There is no real-time monitoring in Manipur and Sikkim, which is why the analysis is unable to cover these states.
Even from the states covered, the data is limited. Guwahati and Shillong have data available for over two years. Real-time monitors in Agartala, Kohima and Aizwal became operational only near the end of 2020, which limits the possibility of doing long-term trend analysis for these cities. Naharlagun got its real-time monitor in March 2021. Due to the excessive amount of missing data from this station, any meaningful analysis is not possible.
“Gaps in air quality data and lack of quality control of data make it difficult to construct reliable air quality trends for these cities,” says Avikal Somvanshi, programme manager, Urban Lab, CSE.
“The air quality in the region is worsening. But this has not drawn adequate public attention. In winter, air quality of cities like Guwahati can be almost as bad as what we see in the National Capital Region (NCR) and cities of Uttar Pradesh. Pollution is also high in smaller cities like Agartala and Kohima.”
Guwahati has the most polluted air
Average PM2.5 levels in 2021 (up till November 30) have already surpassed the 2019 annual average in Guwahati. The city’s 2020 annual average was also higher than its 2019 average which indicates a continuous worsening of air in the city.
Shillong is the only other city in the region that has a station generating data for over two years, but due to poor data availability, its annual averages cannot be considered credible. Nevertheless, the city’s average is considerably below the annual standard.
Among other cities meeting the minimum data availability requirements, Agartala with a 2020 average of 45 micro gramme per cubic metre (ug/m3) is the second most polluted city in the region.
Kohima with a 2020 average of 35 ug/m3 is the third most polluted city in the region. Aizwal 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.