Effects of the COVID-19 Lockdown on Air Pollutant Levels and Associated Reductions in Ischemic Stroke Incidence in Shandong Province, China

Han Wu; Zilong Lu; Jing Wei; Bingyin Zhang; Xue Liu; Min Zhao; Wenhui Liu; Xiaolei Guo; Bo Xi

doi:10.3389/fpubh.2022.876615

Effects of the COVID-19 Lockdown on Air Pollutant Levels and Associated Reductions in Ischemic Stroke Incidence in Shandong Province, China

Front Public Health. 2022 May 27:10:876615. doi: 10.3389/fpubh.2022.876615. eCollection 2022.

Authors

Han Wu¹, Zilong Lu², Jing Wei³, Bingyin Zhang², Xue Liu¹, Min Zhao⁴, Wenhui Liu⁵, Xiaolei Guo², Bo Xi¹

Affiliations

¹ Department of Epidemiology, School of Public Health, Qilu Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China.
² Shandong Center for Disease Control and Prevention, and Academy of Preventive Medicine, Shandong University, Jinan, China.
³ Department of Atmospheric and Oceanic Science, Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, United States.
⁴ Department of Nutrition and Food Hygiene, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, China.
⁵ Information and Data Analysis Lab, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, China.

Abstract

Background: Local governments in China took restrictive measures after the outbreak of COVID-19 to control its spread, which unintentionally resulted in reduced anthropogenic emission sources of air pollutants. In this study, we intended to examine the effects of the COVID-19 lockdown policy on the concentration levels of particulate matter with aerodynamic diameters of ≤1 μm (PM₁), ≤2.5 μm (PM_2.5), and ≤10 μm (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), and carbon monoxide (CO) and the potential subsequent reductions in the incidence of ischemic and hemorrhagic stroke in Shandong Province, China.

Methods: A difference-in-difference model combining the daily incidence data for ischemic and hemorrhagic stroke and air pollutant data in 126 counties was used to estimate the effect of the COVID-19 lockdown on the air pollutant levels and ischemic and hemorrhagic stroke incident counts. The avoided ischemic stroke cases related to the changes in air pollutant exposure levels were further estimated using concentration-response functions from previous studies.

Results: The PM₁, PM_2.5, PM₁₀, NO₂, and CO levels significantly decreased by -30.2, -20.9, -13.5, -46.3, and -13.1%, respectively. The O₃ level increased by 11.5% during the lockdown compared with that in the counterfactual lockdown phase of the past 2 years. There was a significant reduction in population-weighted ischemic stroke cases (-15,315, 95% confidence interval [CI]: -27,689, -2,942), representing a reduction of 27.6% (95% CI: -49.9%, -5.3%). The change in the number of hemorrhagic stroke cases was not statistically significant. The total avoided PM₁-, PM_2.5-, PM₁₀-, NO₂-, and CO-related ischemic stroke cases were 739 (95% CI: 641, 833), 509 (95% CI: 440, 575), 355 (95% CI: 304, 405), 1,132 (95% CI: 1,024, 1,240), and 289 (95% CI: 236, 340), respectively.

Conclusion: The COVID-19 lockdown indirectly reduced the concentration levels of PM₁, PM_2.5, PM₁₀, NO₂, and CO and subsequently reduced the associated ischemic stroke incidence. The health benefits due to the lockdown are temporary, and long-term measures should be implemented to increase air quality and related health benefits in the post-COVID-19 period.

Keywords: COVID-19; air pollution; incidence; ischemic stroke; lockdown.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Air Pollutants* / analysis
Air Pollution* / analysis
COVID-19* / epidemiology
COVID-19* / prevention & control
China / epidemiology
Communicable Disease Control
Hemorrhagic Stroke*
Humans
Incidence
Ischemic Stroke*
Nitrogen Dioxide / analysis
Particulate Matter / analysis

Substances

Air Pollutants
Particulate Matter
Nitrogen Dioxide