According to an environmental group report, even as the air quality improved due to coronavirus lockdown, the world's five most populous cities recorded 160,000 premature deaths due to dreadful pollution.

According to a report from Greenpeace Southeast Asia, the worst-affected state was New Delhi, the most polluted capital on Earth, where around 54,000 deaths are estimated to have occurred due to hazardous PM2.5 airborne particles.

"When governments choose coal, oil and gas over clean energy, it's our health that pays the price," said Avinash Chanchal, climate campaigner at Greenpeace India.

In Tokyo, the figure was 40,000 with the rest spread across Shanghai, Sao Paulo and Mexico City, according to the report, which looked at the impact of microscopic PM2.5 matter produced by burning fossil fuels.

PM2.5 particles are considered to be the most harmful substances for an individuals health. They damage the heart and lungs, and increase the chances of severe asthma attacks.

Some studies have linked PM2.5 exposure to a higher risk of dying from coronavirus.

The report used an online tool that estimates the impacts of PM 2.5 by taking air quality data from monitoring site IQAir (Swiss Air Technology Company) and combining it with scientific risk models, as well as population and health data.

The tool is a collaboration between Greenpeace, IQAir, and the Centre for Research on Energy and Clean Air.

Despite the high numbers of deaths, coronavirus lockdowns imposed across the world did clear traffic off the streets and shut down polluting industries. One of the benefits of lockdown was that people could see the clear skies again. 

Delhi, for instance, underwent a dramatic transformation last year during the lockdown. Residents commented on improved air quality, while the netizens took it on to many social media platforms posting pictures of clear skies everyday.

Scientists say that massive drops in some pollutants due to lockdowns are bound to have prevented deaths.

Nevertheless, Greenpeace urged governments to put investment in renewable energy at the heart of plans to recover from the pandemic-triggered economic downturn.

"To really clean up our air, governments must stop building new coal plants, retire existing coal plants, and invest in clean energy generation, such as wind and solar," said the group's air pollution scientist Aidan Farrow.