Environmental campaign group Greenpeace Southeast Asia and air quality technology company IQAir measured pollution levels across 28 cities – chosen according to where data was available and with a geographical spread.
In the five most-populated cities – Delhi, Mexico City, Sao Paulo, Shanghai and Tokyo – air pollution caused about 160,000 deaths and economic losses, totalling about $85bn.
“A few months of lockdown hasn’t really dented that long-term average of air pollution that people have been exposed to,” said Aidan Farrow, an air pollution scientist at Greenpeace Research Laboratories at Britain’s University of Exeter.
“It is a little shocking to see how much upheaval there has been – and we still have work to do to improve air pollution,” he told the Thomson Reuters Foundation.
Air pollution is the single largest environmental risk to human health globally, and kills an estimated 7 million people every year, according to the World Health Organization (WHO).
The WHO says nine out of 10 people breathe polluted air, which is linked to strokes, lung cancer and heart disease – and now equals the effects of smoking tobacco, health experts say.