The COVID-19 lockdown reduced dangerous air pollutants in five Indian cities -- Chennai, Delhi, Hyderabad, Kolkata, and Mumbai -- by up to 54 per cent saving 630 people from premature deaths, a team of UK scientists, led by an Indian-origin researcher have found.

In late March 2020, a complete lockdown of internal and external borders together with social isolation measures came into effect in India, affecting the lives and mobility of its 1.3 billion population.

"COVID-19 has had a devastating effect on the lives and livelihoods of billions across the world," said study researcher Prashant Kumar, Professor at the University of Surrey in the UK.

"This tragic global event has allowed us to quantify the impact that human activity has had over our environment and, in particular, our air quality," Kumar added.

For the study, published in the journal Sustainable Cities and Society, the research team studied the levels of harmful fine particulate matter (PM2.5) originating from vehicles and other non-vehicular sources in the five Indian cities from the start of the lockdown period until 11 May 2020.

The team analysed PM2.5 distribution and contextualised their findings against those from other cities from across the world.

They also explored potential factors influencing differences between divergent concentration changes in different cities, as well as aerosol loadings at a regional scale.

In their work, the research team compared these lockdown air pollution figures with those from similar periods of the preceding five years.

The results showed that the lockdown reduced concentrations of harmful particles across all five cities, from a 10 per cent reduction in Mumbai up to a 54 per cent reduction in Delhi.

These reductions in PM2.5 were found to be comparable to reductions in other cities across the world, such as in Vienna (60 per cent) and Shanghai (42 per cent).

The team also investigated the monetary value of avoided premature mortality due to reduced PM2.5 concentrations, and calculated that the reduction may have saved 630 people from premature death and $690 million in health costs in India.

The team pointed out that the present lockdown situation offers observational opportunities regarding potential control systems and regulations for improved urban air quality.

"While the reduction in PM2.5 pollution may not be surprising, the size of the reduction should make us all take notice of the impact we have been having on the planet," the study authors wrote.(IANS)