The reduction in economic activity during the pandemic lockdown had led to a decrease in air pollution in most parts of India, but satellite observations show that parts of central-west and north India have seen increases in air pollution, contrary to the general trend, the government said on Monday citing a study. Scientists at the Aryabhatta Research Institute of Observational Sciences (ARIES), an autonomous institute of the Department of Science and Technology, used the EUMETSAT and NASA satellite observations for 2018, 2019 and 2020 and examined the impact of a significant interruption in activity on the changes in the distribution of ozone, carbon monoxide and nitrogen dioxide during the embargo.

According to the study published in Environmental Science and Pollution Research, ozone, carbon monoxide and NO2 showed an increase of about 15 percent over the central western part of India.

The results found carbon monoxide showed a consistent increase in concentration (up to 31 percent) during lockdown at higher altitudes.

The study was carried out by Prajjwal Rawat, a Senior Research Fellow at ARIES Nainital, along with its research director Dr. Manish Well headed.

In a statement, the Ministry of Science and Technology said scientists had found that regions in midwestern India and northern India based on cutting-edge satellite observations are more prone to higher levels of air pollution and therefore at greater risk of respiratory diseases.

“In 2020, India was imposed a full nationwide lockdown to prevent the spread of coronavirus disease. This has disrupted the economy tremendously with one positive side effect, a short-term improvement in air quality near the surface,” the ministry said.

Satellite-based monitoring of toxic trace gases – ozone, NO2 and carbon monoxide – near the surface and in the free troposphere showed largely a reduction in pollutants over India, it said.

However, increases in ozone and other toxic gases have been observed in some regions such as west-central India, some parts of northern India, and the remote Himalayas. This could have exacerbated respiratory health risks in these regions during the pandemic, the ministry said.

Long-distance transport and downward transport from the stratosphere significantly increased ozone concentrations over northern India during lockdown, and remote regions such as the Himalayas and coastal cities showed the minimal impact of lockdowns on air quality, with a tendency for criteria to increase in air pollutants, according to the Study.

According to the ARIES team, this study has helped identify the regions that are more prone to higher levels of air pollution, and thus can identify areas at greater health risk.

The team previously demonstrated together with scientists from ISRO INSAT-3D as a valuable Indian geostationary satellite for the investigation of ozone pollutants over India. For other criteria of air pollutants such as NO2, SO2 and CO, however, India lacks space-based observations and needs air quality monitoring from native satellites in orbit.