The effect of the first lockout on air pollution was eliminated, our study suggests

The epidemic caused governments worldwide to initiate lockdowns in early 2020, temporarily closing workplaces and evacuating roads and public spaces. As economic activity slowed, so did the emissions of air pollutants. After about a year, the effect with which we breathe is becoming apparent.

The most direct way to determine the effects of lockdown on air quality is to compare measurements before and after lockdown starts. First study Used this approach and reported large reductions in some pollutants, such as (No.) A study Claimed that NO Wu emissions fell by 90% in Wuhan (Chinese) COVID-19 is believed to be at its peak).

But this comparison is misleading. For example, weather also affects pollution levels, for example by spreading emissions from cities. More fossil fuels are burned for heating during winter than in spring, and pollutants are formed to react differently in the atmosphere under different conditions of sunlight and temperature, causing air pollution levels between seasons. Varies. These factors obscure the effect of a single event on air pollutant concentrations.

Our new analysis Investigated 2020 during the spring in the Northern Hemisphere and adjusted them to offset the effects of weather and seasonal changes. This allowed us to isolate the impact of lockdown alone on air quality in 11 cities: Beijing, Wuhan, Milan, Rome, Madrid, London, Paris, Berlin, New York, Los Angeles, and Delhi.

This is important to do, because if people reduce the benefits of lockdown on air quality, they can reduce the scale of the air pollution challenge in the world’s cities and take the radical action necessary to bring urban air quality within healthy limits Can fail. Globally, air pollution is associated with approx. Seven million premature deaths every year.

Ozone up, noone down

Our study looked at the levels of NO₂, ozone (O and) and , Such as soot (smaller than 2.5 micrometers; also called PM2.5). NO is emitted from vehicle exhaust, power station chimneys and gas boilers. Ground-level ozone, unlike the protective layer in the stratosphere 20 km above the Earth, is an air pollutant formed in the form of hydrocarbons and nitrogen oxides (NOₓ) in sunlight. Fine particles are emitted from many sources in industry, traffic, and agriculture, and are small enough to live directly in the lungs. They can be made up of severe pollutants in the atmosphere. All these pollutants are harmful to human health and cause heart and lung conditions.

Except for all the cities we studied, the level of NO₂ fell during lockdown, but the effect was smaller than the suggested levels before and after. For example, in Wuhan, NO₂ concentrations fell to 47% between the second and fifth week of lockdown, but some of it was due to weather and It would have happened anyway. Lockdown alone accounted for 34%.

Measured changes in NOured were highest at locations closest to the roads. But the level of NO But would suggest to be less than the overall change in traffic. This is because less traffic was reduced as the number of heavy vehicles on the roads, such as diesel-powered freight trucks.

In fact, ozone levels rose in most places during the lockdown, up to 2% in some locations and up to 30% in others. This was in large part because the traffic emission of nitrogen oxide would normally have removed some of this ozone by reacting with it.

PM2.5 levels fell in most of the cities where we studied due to the lockdown, as primary emissions from road traffic and other sources fell. But high concentrations of PM 2.5 were still recorded during the lockdown, particularly in Beijing, London and Paris. One possible reason is that weather patterns cause pollution from heavy industry areas to flow to cities. Another is that the changing chemical nature of the atmosphere during lockdown converted more gaseous compounds into air into these finer particles.

वायु प्रदूषण पर पहले तालाबंदी का प्रभाव समाप्त हो गया था, हमारे अध्ययन से पता चलता है

Removing seasonal and weather effects helps to isolate the effect of lockdown on air pollution. Credit: Shi et al. (2021)Provided the author

A window to the future

Lockdowns were an unintentional global experiment that produced clean air for many millions of people. Reductions in NO red alone have brought and continue to have widespread health benefits, allowing most cities to meet air quality guidelines set by the World Health Organization. But the increase in ozone may have made up for it, and many of the changes are smaller than we originally thought – highlighting how big the challenge of clearing our air is. A systematic approach to control air pollution, tailored to each city and considering all The type will provide the greatest health benefit.

In some ways, the lockdown allows us to look into the future. Changes in NO is observed in UK cities during lockdown, showing what is expected between the two 2027 and 2030, Because the emissions of fossil-fueled vehicles are phased out by electrical options.

Whereas carbon dioxide (CO carbon) is mixed globally in the atmosphere and can tolerate Several hundred years, Pollutants such as NO रहते remain in the air one day and close to their source. Lesson from Aggressive action to eliminate the sources of CO – – an international effort to tackle the global issue – will also bring immediate benefits And health in your neighborhood.

Early COVID-19 lockdown had less impact on urban air quality than before

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Quotes: The impact of the first lockdown on air pollution was over, our study shows (2021, 14 January) https://naveenbharat.org/news/2021-01-lockdown-effect-air-pollution-overstated. Retrieved 14 January 2021 from html.

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