Covid-19 Lockdowns Improved Air Quality But Far Less Than Expected

A new study published in the peer-reviewed journal Science Advances has found that while Covid-19 lockdowns did improve air quality, the gains were smaller than expected and fluctuated from city to city. 

The researchers from the University of Birmingham in the UK evaluated air quality across 11 global cities – Beijing, Wuhan, Milan, Rome, Madrid, London, Paris, Berlin, New York, Los Angeles and Delhi – to arrive at this conclusion. 

Overall the study evaluated changes in ambient NO2, O3 and fine particles (PM2.5).

NO2 is a key air pollutant from traffic emissions, associated with respiratory problems, while ozone (O3) is also harmful to health, and damages crops. Concentrations of PM2.5, which can worsen medical conditions such as asthma and heart disease, decreased in all cities studied except in London and Paris. 

Researchers corrected for the impact of weather and seasonal trends and found small reduction in NO2 levels. The lockdowns in fact caused concentrations of ozone to rise. 

Impact of lockdowns more complex

As several countries went into lockdown early on to halt the spread of the Covid-19 virus, it was expected that air quality would improve substantially.

“Emission changes associated with the early lockdown restrictions led to abrupt changes in air pollutant levels but their impacts on air quality were more complex than we thought, and smaller than we expected,” said Zongbo Shi, professor of atmospheric biogeochemistry at the University of Birmingham, and the study’s lead author.

Researchers added that for air quality to meet set global standards these reductions will have to be more long-term.

“The reduction in NO2 will be beneficial for public health – restrictions on activities, particularly traffic, brought an immediate decline in NO2 in all cities. Had similar levels of restrictions remained in place, annual average NO2 concentrations would have in most locations complied with WHO air quality guidelines,” said Roy Harrison, Queen Elizabeth II Birmingham centenary professor of environmental health and a co-author of the study.

Need for systemic change

The mitigation measures in the future would both have to be systemic and tailored for specific cities to maximize the benefits, according to the researchers. 

The Covid-19 lockdowns did curtail some pollution-causing activities like commuting or electricity use in commercial establishments while others like biomass-based cooking or air-conditioning in homes continued. “Unless we transform the underlying structural causes of carbon dioxide emissions or particulate matter pollution, temporary cessation of selected activities or favourable weather patterns will not be sufficient to make our skies cleaner and our children healthier,” said Ulka Kelkar, who is the director of climate program at WRI India and was not involved with the Birmingham study.

Mounting research points to the public health and economic fall outs of air pollution. A recent study in south Asia – one of the world’s most populous regions – found that air pollution was linked to 7% of pregnancy losses in the form of miscarriages and stillbirths. In India alone, an estimate suggests air pollution cost the economy $36.8 billion in 2019.

“Globally carbon dioxide emissions fell by an estimated 6% during 2020 as a result of the Covid-19 lockdowns, economic downturn, and decline in aviation,” said Kelkar. “Staying within a safe global warming requires us to repeat this 6% decrease each year for the next ten years. This will be possible only if we significantly accelerate the adoption of clean energy and energy efficiency throughout the economy.”