The first lockdowns of Covid-19 led to a significant drop in air pollution around this word, a new study says, but the changes were smaller than previously thought.
Researchers at the University of Birmingham found that after eliminating the effects of weather conditions, the reductions in dangerous gases such as nitrogen dioxide (NO2) were lower than expected.
In fact, the lockdowns have resulted in increased concentrations of ozone – which can be harmful to health and damage crops – in cities.
The research team also found that concentrations of PM2.5 – fine particle air pollution that can worsen medical conditions such as asthma and heart disease – had declined in all of the cities studied except London and Paris.
Scientists used machine learning to eliminate weather impacts and seasonal trends before analyzing the data: site-specific hourly concentrations of major pollutants from December 2015 to May 2020.
Air pollution is considered the biggest environmental health risk in the world, contributing to 6.7 million deaths each year. The World Bank estimates that air pollution costs the global economy billions of dollars a year.
Public Health England calls air pollution “the biggest environmental threat to health in the UK” and links it to 36,000 deaths per year.
Last December, 9-year-old Ella Kissi-Debrah of Lewisham became the first person in the UK to list air pollution as a cause of death after a years-long campaign led by her mother Rosamund.
Zongbo Shi, professor of atmospheric biogeochemistry at the University of Birmingham, said: “Emissions changes associated with early lockout restrictions have led to abrupt changes in air pollutant levels, but their impacts on the quality of the air were more complex than we thought, and smaller than expected. . “
Roy Harrison, Queen Elizabeth II Centenary Environmental Health Professor in Birmingham, co-author of the study, said: “Reducing NO2 will benefit public health – restrictions on activities, especially traffic. , resulted in an immediate drop in NO2 in all cities. .
“If similar levels of restrictions had remained in place, the average annual NO2 concentrations at most sites would have complied with WHO air quality guidelines.