Early COVID-19 lockdown in Delhi had less impact on urban air quality than first believed

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The first COVID-19 lockdowns led to significant changes in urban air pollution levels around the world, but the changes were smaller than expected, a new study reveals.
After developing new corrections for the impact of weather and seasonal trends, such as reduced NO 2 emissions from winter to summer, the researchers evaluated changes in ambient NO 2 , O3 and fine particle (PM 2.5 ) concentrations arising from lockdown emission changes in 11 global cities: Beijing, Wuhan, Milan, Rome, Madrid, London, Paris, Berlin, New York, Los Angeles and Delhi.

Led by experts at the University of Birmingham, the international team of scientists discovered that the beneficial reductions in NO 2 due to the lockdowns were smaller than expected, after removing the effects of weather. In parallel, the lockdowns caused (weather-corrected) concentrations of ozone in cities to increase.

NO 2 is a key air pollutant from traffic emissions, associated with respiratory problems, while ozone is also harmful to health, and damages crops.

Publishing their findings today in Science Advances, the research team also reveals that concentrations of PM 2.5 , which can worsen medical conditions such as asthma and heart disease, decreased in all cities…
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