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COVID-19 lockdowns cause global air pollution declines.

Zander S Venter1, Kristin Aunan2, Sourangsu Chowdhury3

  • 1Terrestrial Ecology Section, Norwegian Institute for Nature Research, 0349 Oslo, Norway; zander.venter@nina.no.

Proceedings of the National Academy of Sciences of the United States of America
|July 30, 2020
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Summary

COVID-19 lockdowns significantly reduced air pollution, with nitrogen dioxide (NO2) decreasing by 60% and fine particulate matter (PM2.5) by 31%. This highlights the impact of reduced economic activity on air quality and public health.

Keywords:
COVID-19 confinementair qualityemissionsnitrogen dioxideparticulate matter

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Area of Science:

  • Environmental Science
  • Atmospheric Chemistry
  • Public Health

Background:

  • The COVID-19 pandemic necessitated global lockdowns, drastically cutting economic and transport activities.
  • Understanding the impact of these unprecedented reductions on air quality is crucial for public health.

Purpose of the Study:

  • To test the hypothesis that lockdowns reduced tropospheric and ground-level air pollution.
  • To quantify the changes in specific air pollutants during the lockdown period.

Main Methods:

  • Utilized satellite data and over 10,000 ground-level air quality stations across 34 countries.
  • Accounted for meteorological variability to isolate pollution changes.
  • Leveraged Google and Apple mobility data to correlate transport declines with pollution reduction.

Main Results:

  • Observed significant population-weighted declines in ground-level nitrogen dioxide (NO2: 60%) and fine particulate matter (PM2.5: 31%).
  • Noted marginal increases in ozone (O3: 4%) and smaller reductions in tropospheric pollutants compared to ground-level, indicating spatial variability.
  • Found empirical evidence linking vehicle transportation declines to reduced ambient NO2 exposure.

Conclusions:

  • Lockdowns demonstrated a substantial potential for mitigating air pollution through reduced economic and transport emissions.
  • Findings suggest that reducing "business as usual" emissions can lower public health risks.
  • The study underscores the complex chemistry and transport affecting pollutant distribution.