Changes in air pollution due to COVID-19 lockdowns in 2020: Limited effect on NO₂, PM_2.5, and PM₁₀annual means compared to the new WHO Air Quality Guidelines

Abstract

Background Lockdowns have been fundamental to decreasing disease transmission during the COVID-19 pandemic even after vaccines were available. We aimed to evaluate and compare changes in air quality during the first year of the pandemic in different cities around the world, investigate how these changes correlate with changes in mobility, and analyse how lockdowns affected air pollutants’ annual means. Methods We compared the concentrations of NO 2 , PM 2.5 , and PM 10 in 42 cities around the world in the first months of the pandemic in 2020 to data from 2016-2019 and correlated them with changes in mobility using Human Development Indexes (HDIs). Cities with the highest decreases in air pollutants during this period were evaluated for the whole year 2020. We calculated the annual means for these cities and compared them to the new World Health Organization (WHO) Air Quality Guidelines. A Student’s t - test (95% confidence interval) was used to evaluate significant changes. Results Highest decreases in NO 2 , PM 2.5 , and PM 10 were between -50 and -70%. Cities evaluated for the whole year 2020 generally showed a recovery in air pollution levels after the initial months of the pandemic, except for London. These changes positively correlated with year-long mobility indexes for NO 2 and PM 2.5 for some cities. The highest reductions in air pollutants’ annual means were from -20 to -35%. In general, decreases were higher for NO 2 , compared to PM 2.5 and PM 10 . All analysed cities showed annual means incompliant with the new WHO Air Quality Guidelines for NO 2 of 10 μg/m 3 , with values 1.7 and 4.3 times higher. For PM 2.5 , all cities showed values 1.3 to 7.6 times higher than the WHO Guidelines of 5 μg/m 3 , except for New Delhi, with a value 18 times higher. For PM 10 , only New York complied with the new guidelines of 15 μg/m 3 and all the other cities were 1.1 to 4.2 times higher, except for New Delhi, which was 11 times higher. Conclusions These data show that even during a pandemic that highly affected mobility and economic activities and decreased air pollution around the world, complying with the new WHO Guidelines will demand a global strategical effort in the way we generate energy, move in and around the cities, and manufacture products.

Assessing the relationship between particulate matter concentration and property values in Spanish cities

“…In 2022, a more complex scenario appeared, which was marked by the ongoing challenges and changes brought about by the COVID-19 pandemic. In the early pandemic stages in 2020 and 2021, air quality in many parts of the world, including Spain, improved due to lockdowns and fewer economic activities [ 33 ]. However, air pollution resurged as the world began to recover and reopen in 2022 [ 34 ].…”

Development of an Air Filter to Remove Fine Dust from Indoor Air Using a Traditional Korean Paper, ‘Hanji’

“…Due to rapid industrialization and urbanization in East Asia, the region faces various environmental issues, including an increase in air pollution caused by heightened energy and vehicle usage [1,2]. Since 2013, the World Health Organization (WHO) has classified fine particles (PM10) and ultrafine particles (PM2.5), which can penetrate both respiratory and skin barriers and cause severe damage to the body, as Group 1 carcinogens [3,4]. Accordingly, there is a continuous demand for the development of technologies to reduce fine dust levels [5][6][7].…”