- Smaller towns see higher winter pollution levels than mega cities
- Cities of the north-eastern region – a new focus of this analysis – show lower averages but higher toxicity as the share of PM2.5 in PM10 is considerably high
As the winter season nears its end and summer trends start setting in across most regions of the country, understanding the changes in winter pollution trends across regions becomes necessary to know the challenge and depth of action needed to meet the clean air benchmark. Centre for Science and Environment (CSE) has carried out an extensive analysis of real-time data from cities in different regions to throw light on the difference between 2020-21 winter and the previous winters. This has been a special winter that coincides with the unlocking of the economy post-pandemic linked hard lockdown phases.
“Winter is a special challenge when inversion, and cool and calm weather traps and spikes daily pollution. While the northern Indo Gangetic Plain is most affected, other regions also experience a rise, but with lesser intensity. But this year even though the average level of PM2.5 during summer and monsoon months was considerably lower than the previous year due to the summer lockdown, the winter PM2.5 concentration has risen compared to 2019 winter in many cities across regions. This bouncing back of pollution post-lockdown unmasks the high impacts of local and regional pollution. This demands quicker regional reforms to curb pollution from vehicles, industry, power plants and waste burning to curb the winter pollution and also sustain annual improvement at a regional scale with speed,” says Anumita Roychowdhury, CSE’s executive director in charge of research and advocacy.
“This analysis has considered 99 cities where data availability for two consecutive winters meets the minimum criteria of 75 per cent of data completeness requirement.
The analysis is part of the air pollution tracker initiative of CSE. It is based on publicly available granular real time data (15-minute averages) from the Central Pollution Control Board’s (CPCB) official online portal Central Control Room for Air Quality Management. The data is captured from 248 official stations under the Continuous Ambient Air Quality Monitoring System (CAAQMS) spread across 115 cities in 22 states and union territories. CAAQMS has many more cities in its network than included in the analysis.
This part of story has highlighted only the winter air pollution level in north east region.
Northeast India is the eastern most region of India representing both a geographic and political administrative division of the country. It comprises eight states – Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, Tripura and Sikkim.
Monitoring is very limited in this region. Data is available for only Guwahati in Assam and Kohima in Nagaland. Real-time monitoring has recently started in Shillong, Agartala, and Aizwal. But for the purpose of this analysis they do not meet the minimum data requirement. Geographically this region represents the Eastern Himalayas and Brahmaputra plains.
Guwahati has recorded worst levels in the region with seasonal winter average of 103 μg/m3. This large and populated city in the plains has a valley effect and is markedly different from other cities in the region which are located in the hills and are much smaller. City’s winter average rose by 7 per cent. (About 450 km away, Siliguri in West Bengal saw 22 per cent increase in seasonal pollution).
Kohima in Nagaland was the only other city which met the data completeness requirement in the region. With a seasonal average of 38 μg/m3 it is one of the cleanest city not just in the region but also among all other cities in the analysis. But the air quality in the city can drop to “poor” AQI category on multiple days which is a reason for concern.
Agartala, Shillong, and Aizwal also have real-time monitors that became operational only near the end of 2020. Data availability is more than 50 per cent but less than 75 per cent of the study duration. Therefore, their provisional seasonal averages have been computed but not used for comparative analysis. Agartala’s winter average of 84 μg/m3 which is more than double than the levels noted in other hill-towns of the region, in fact it is higher than all cities of south India. In Agartala PM2.5 73 per cent of PM10. This indicates highly toxic air. Influence of inert crustal dust is much less. Shillong and Aizwal also have high share of PM2.5 but significantly lower concentration.
This requires quicker reforms and action in key sectors of pollution – vehicles, industry, power plants and waste management to control winter pollution and decrease the annual air pollution level.
Reported by Ms. Pratyusha Mukherjee, , a Senior Journalist working for BBC and other media outlets, also a special contributor to IBG News. In her illustrated career she has covered many major events and achieved International Media Award for reporting.