Delhi residents are breathing clearer air due to 49 per cent improvement in the Air Quality Index (AQI). If these low levels of air pollution are maintained, India's annual death toll could reduce by 6.5 lakh, according to a study by the Indian Institute of Technology (IIT) Delhi, and two Chinese universities – Fudan University in Shanghai and Shenzhen Polytechnic.
AQI includes several air pollutants, such as particulate matter (PM), nitrogen oxide, sulphur dioxide, ozone, carbon monoxide and so on. Particulate matter with a diameter of 2.5 and 10 microns are considered most harmful because these are too small to be filtered out of the body.
The nationwide lockdown which started from March 25 resulted in an interruption in economic activities during the first month of the lockdown and led to a 52 per cent average reduction in excessive risk (health risk assessment due to air pollution exposure) for particulate matter (PM) across India. The latest study also estimated a four-time decline in health risks associated with other pollutants, according to a Hindustan Times report.
During the research, it was found that concentrations of six pollutants, PM10 and PM2.5, carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), and sulphur dioxide (SO2) were analyzed between March 16 and April 14 from 2017 to 2020, in 22 cities across India.
The study, titled, 'Effect of restricted emissions during Covid-19 on air quality in India' was published in the peer-reviewed science journal Elsevier Public Health Emergency Collection, earlier this month.
"If this low concentration during one month persisted for a year, it would save the lives of 6.5 lakh people, which would have otherwise been lost due to air pollution health effects," Sri Harsha Kota, corresponding author from IIT-Delhi was quoted as saying.
Reportedly, out of all the pollutants, PM 2.5 had a maximum reduction in most regions. The lockdown imposed to stop the spread of COVID-19 had enforced restrictions and self-quarantine measures, which reduced emissions from transportation and industries.
Delhi has reported 87.9 per cent decline in nitrogen oxide, whose main contributor is transported.
"Delhi observed the maximum reduction of 49 per cent in AQI. This reduction in AQI was also associated with a change in dominant pollutants in many cities," reads the study.
There was a slight increase in sulphur dioxide concentrations. According to IIT Delhi, it could be due to no restrictions on power plants in northern India and using coal-powered energy as an essential commodity during the lockdown period. Ozone also increased by 10 per cent as compared to the last three years.