New Delhi, January 19: Air pollution is rapidly becoming a matter of concern in the western states of Maharashtra and Gujarat as well despite their geographical advantages and favourable meteorology, according to a new analysis of regional air pollution levels by the Centre for Science and Environment (CSE).

"The number of bad-air days in Mumbai have doubled between 2019 and 2021, while good days are down by 20 per cent. This underscores the urgency of scaling up action across all sectors to prevent further worsening and to arrest the trend in this region," said Anumita Roychowdhury, executive director, research and advocacy, CSE.

The analysis covered 56 continuous ambient air quality monitoring stations (CAAQMS) spread across 15 cities in two states: Maharashtra -- one station each in Aurangabad, Kalyan, Nagpur, Nashik and Solapur, two in Chandrapur, four in Navi Mumbai, eight in Pune, and 21 stations in Mumbai; and Gujarat -- one station each in Ankleshwar, Nandesari, Vapi and Vatva, four in Gandhinagar, and eight stations in Ahmedabad. Delhi Air Pollution: Air Quality in National Capital Stands in 'Very Poor' Category Today, AQI Stands at 339.

Avikal Somvanshi, programme manager, Urban Data Analytics Lab, CSE, pointed out that even though there are multiple real time monitors in a few cities of these states, many of them could not be considered for long-term analysis due to data gaps and lack of quality data.

Moreover, in several cases, the real time monitors have been set up recently and therefore, long-term data is not available. The researchers found that nearly all cities in the region show a drop in annual average PM2.5 levels in 2020 -- the year with the maximum number of lockdown phases. But there has been a rebound and a rising trend is visible in 2021.

Gujarat's cities are more polluted than those in Maharashtra. Vatva and Ankleshwar have the most polluted air in the region with the 2021 average of PM2.5 at 67 microgram per cubic metre. This is followed by Vapi and Ahmedabad with 2021 annual averages at 54 microgram per cubic metre and 53 microgram per cubic metre, respectively.

In Maharashtra, Chandrapur, an industrial city, has recorded levels marginally above the annual standard at 43 microgram per cubic metre. Other stations have met the annual standard though all of them are showing a rising trend in 2021 after the dip in 2020.

With 102 days of poor and very poor AQI, Ankleshwar in Gujarat has the unhealthiest days in the region, followed by Kalyan with 84 days, Vatva (75 days), and Navi Mumbai (54 days).

Vapi has 48 days of poor and very poor AQI -- but its data is missing for 138 days (mainly for the winter months). Mumbai has registered 42 days of poor and very poor AQI despite meeting the annual standard. Delhi's Air Pollution: Air Quality Index In The National Capital Remains In 'Moderate' Category.

Bad-air days begin to build up in the cities of the western states during the end of December and persist till the end of January. Cities in the Mumbai Metropolitan Region show a more pronounced impact of winter pollution compared to cities of other regions. Industrial towns have bad-air days across the year, but there is some clustering during winter, the CSE said.

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