Infectious Disease

COVID-19 lockdowns had much less of an impression on air air pollution than anticipated

January 16, 2021

3 min read

ADD SUBJECT TO EMAIL ALARMS

Receive an email when new articles are published

Please enter your email address to receive an email when new articles are published . “data-action =” subscribe “> subscribe

We could not process your request. Please try again later. If you continue to have this problem, please contact customerservice@slackinc.com.

Back to Healio

COVID-19 lockdowns in multiple cities had less of an impact on air pollution than expected, according to a study published in Science.

Zongbo Shi, PhD, Professor of Atmospheric Biogeochemistry at the University of Birmingham and colleagues used a weather normalization method to isolate changes in air pollutant concentrations and assess air quality effects from restricted zones in 11 cities: Beijing and Wuhan, China; Milan; Rome; Madrid; London; Paris; Berlin; New York; Los Angeles; and Delhi, India.

Zongbo Shi

They found that while the decrease in automobile use during the lockdown resulted in a decrease in NO2 in all cities, only 30% of the decrease was due to the effects of the lockdown. That change was likely due to continued emissions from other pollution sources, they wrote.

We spoke to Shi about the implications of the study.

Q: What factors contributed to the overestimation of air quality changes during the lockdown?

A: There are two main factors. The first is meteorology, which affects pollution, promotes the distribution of local emissions, and removes pollutants from the updraft. The second is the seasonal change in air pollution due to changes in emissions and chemistry – for example, when combustion for heating decreases from winter to spring, and changes in atmospheric processing occur with increasing temperature and increasing sunlight. These factors can cause the air pollutant concentration to change higher or lower than the actual emission change on either side of a given date – for example at the beginning of a closure – due to the closures.

Q: Can we expect air quality to return to pre-pandemic levels once the lockdowns are lifted?

A: The pandemic has changed the way we work and do business. This has potential positive effects on air quality. For example, if more people work from home, future traffic emissions are likely to be lower than they were before the lockdown. In some cities, there are also clean air measures so that air pollution decreases year by year, for example in Beijing. Therefore, it is more likely that air pollution will be lower in the future unless economic activities such as industrial production in these cities suddenly increase.

Q: Aside from the impact of people during the lockdown, are there any other factors that could have affected air quality?

A: In addition to human factors affecting air pollution emissions, both meteorological conditions and the chemistry of the atmosphere contribute to changes in air quality. As mentioned earlier, meteorological conditions affect the distribution of air pollutants. The chemistry of the atmosphere regulates chemical reactions in the air that create secondary pollutants like ozone and fine particles. Because of this, we have seen ozone rise as air pollutant emissions decreased during the lockdown. In most locations there is a certain amount of ozone in the background air. Road NO emissions remove some of this O3 – the reaction is that NO + O3 creates NO2 + O2. Less traffic therefore leads to fewer NO emissions and less O3 reduction. This is a rapid atmospheric process that takes place over a minute and affects local O3 levels. The slower atmospheric reactions that form O3 over several days are also influenced by the changed emissions.

Q: Are there other areas of research on the subject worth exploring further?

A: There are two areas of research that are worth exploring further. The first is, “What physical and chemical processes are responsible for the increase in secondary pollutants like ozone and secondary PM2.5 during the London and Paris closures?” The second is, “How can we maximize the health benefits of improving air quality by coordinating the control of all important air pollutants such as NO2, O3 and PM2.5? “

Q: Does this study have any impact on air pollution control efforts?

A: Our study shows that the actual air quality improvements from the lockdown were significantly less than suggested in some previous reports or observational data – underscoring the scale of the challenge in cleaning our air. The response from PM2.5 is complex and depends on the city. Therefore, a systematic approach to air pollution control, tailored to each city and taking into account all types of pollutants, would be needed to achieve the greatest health benefits.

In a way, the locks allow us to see into the future. The sharp changes in NO2 in UK cities during the lockdown are the same as those expected from 2027 to 2030 due to changes in vehicle emissions (fleet renewal and electrification) to address the climate challenge. Although atmospheric CO2 mixes globally, pollutants such as NO2 stay in the air for about a day and therefore remain close to where they are emitted. Lockdown shows us that some changes to reduce carbon emissions – driven by global climate change, an international problem – will also bring immediate local benefits to our air quality and health.

ADD SUBJECT TO EMAIL ALARMS

Receive an email when new articles are published

Please enter your email address to receive an email when new articles are published . “data-action =” subscribe “> subscribe

We could not process your request. Please try again later. If you continue to have this problem, please contact customerservice@slackinc.com.

Back to Healio

COVID-19 Resource Center

COVID-19 Resource Center

Related Articles