As lockdowns were implemented in response to the coronavirus pandemic, society and industry as a whole have been brought to a halt across the world. This has offered a glimpse of a cleaner world with no air pollution, with many cities benefiting from it.

Air pollution has declined up to 60% in nine major cities, according to a recent report by the Swiss company IQAir – analyzing government data from Delhi, London, Los Angeles, Milan, Mumbai, New York City, São Paulo, Seoul, Wuhan, and Rome.

The report examined fine particle pollution (PM2.5) in the cities while lockdowns were in place. It used hourly PM2.5 readings obtained from seven governmental agencies as well as readings provided by supplemental, validated non-governmental monitoring stations. Finally, the team compared these levels to those of the same period in 2019, as well as during the same periods in the previous four years. All locations and their data sources are visible on the IQAir AirVisual app and website. All cities except for Rome experienced a reduction in air pollution levels.

The most-polluted areas saw the highest drops in fine particulate matter. Delhi saw a 60% reduction in pollution over a three-week period while its stay-at-home order took effect, compared to the same period last year. Meanwhile, Seoul in South Korea saw a 54% decrease.

Automobile-dependent Los Angeles saw its longest streak of clean air on record: during its lockdown period, fine particle pollution in LA was down 31% when compared to 2019, and down 51% when compared to the previous four-year average. New York City saw air pollution drop 25% as a result of its lockdown.

“Across the globe, the coronavirus pandemic has had a monumental impact on the way we live,” said Frank Hammes, CEO of IQAir. “While the costs are devastating, we are also witnessing how much of air pollution comes from human activity. The reduction in air pollution shows how our habits directly impact the air we breathe.”

London and Madrid saw more modest reductions in air pollution at 9% and 11%, respectively. Rome saw a 30% increase in pollution during its lockdown period, while Delhi, Mumbai, and Los Angeles experienced their best March air quality on record in 2020.

Cleaner air is especially welcomed during a pandemic caused by a virus that affects the lungs, but it’s not forecast to last. Air pollution is expected to rebound after restrictions set during the pandemic loosen. A similar rebound was reported after the 2008 economic crisis.

Air pollution is the most urgent environmental health risk in the world. More than 90% of the planet breathes unhealthy air, leading to seven million premature deaths per year and billions of dollars in costs for health services.