The lockdown measures implemented in Europe and China at the start of the pandemic improved air quality and averted thousands of deaths in regions with severe air pollution, according to a new study. The authors called for control policies to achieve larger air quality improvements.

A team of scientists at the University of Notre Dame found that particulate matter (PM 2.5) concentrations in China and parts of Europe dropped by 29.7% and 17.1% respectively during the lockdown. They measured air quality between February and March in China and February and May in Europe, when stay-at-home orders were in place.

Particulate matter, small airborne particles, comes from combustion-related sources such as industrial emissions, transportation, wildfires, and chemical reactions of pollutants in the atmosphere. This has turned air pollution into the leading environmental cause of death, according to the World Health Organization.

“We look on these lockdowns as the first global experiment of forced low-emission scenarios,” said Paola Crippa, co-author of the study, in a statement. “This unique, real-world experiment shows us that strong improvements in severely polluted areas are achievable even in the short term, if strong measures are implemented.”

Crippa and her team measured particulate matter concentrations at more than 2,500 sites in Europe and China between 2016 and 2020. They integrated these into computer simulations to see how the lockdown impacted air quality and its effects.

The researchers estimated rates of premature death against four different economic recovery scenarios. One of them assumed a fast resumption of normal activity, and another one a gradual come-back. The other two contemplated a second outbreak between October and December and a permanent lockdown for the rest of the year.

“The most surprising part of this work is related to the impact on human health of the air quality improvements,” Crippa said. “It was somewhat unexpected to see that the number of averted fatalities in the long term due to air quality improvements is similar to the COVID-19 related fatalities, at least in China.”

The study found that from February to March an estimated 24,200 premature deaths associated with particulate matter were averted throughout China compared to 3,309 reported COVID-19 fatalities. Improvements in air quality were widespread across China because of extended lockdown measures.

The situation in Europe was quite different. While COVID-19 related deaths were higher compared to China, an estimated 2,190 deaths were still avoided during the lockdown period when compared to averages between 2016 and 2019. The averted fatalities figures become much larger in Europe and China when considering long-term effects.

The researchers believe the study is an example of the need for ad hoc control policies to be developed to achieve effective air quality improvements. This could include subsidies to electric vehicles, prioritizing public transport in heavily trafficked cities, and the adoption of more stringent emission limitations for industries.

“Continuous air pollution mitigation strategies might help in reducing mortality not only during the ongoing COVID-19 pandemic but also in future pandemics related to respiratory diseases, as people exposed to poor air quality are more likely to have pre-existing respiratory or pulmonary conditions that could make them more vulnerable to infectious diseases and ultimately increase the death rate,” the researchers wrote.

The study was published in the journal The Lancet.