How Transportation Restriction Shapes the Relationship Between Ambient Nitrogen Dioxide and COVID-19 Transmissibility: An Exploratory Analysis

Lefei Han; Shi Zhao; Peihua Cao; Marc K C Chong; Jingxuan Wang; Daihai He; Xiaobei Deng; Jinjun Ran

doi:10.3389/fpubh.2021.697491

How Transportation Restriction Shapes the Relationship Between Ambient Nitrogen Dioxide and COVID-19 Transmissibility: An Exploratory Analysis

Front Public Health. 2021 Jul 29:9:697491. doi: 10.3389/fpubh.2021.697491. eCollection 2021.

Authors

Lefei Han¹, Shi Zhao^{2

3}, Peihua Cao⁴, Marc K C Chong^{2

3}, Jingxuan Wang², Daihai He⁵, Xiaobei Deng⁶, Jinjun Ran⁶

Affiliations

¹ School of Global Health, Chinese Center for Tropical Diseases Research, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
² The Jockey Club (JC) School of Public Health and Primary Care, Chinese University of Hong Kong, Hong Kong, China.
³ The Chinese University of Hong Kong (CUHK) Shenzhen Research Institute, Shenzhen, China.
⁴ Clinical Research Center, Zhujiang Hospital, Southern Medical University, Guangzhou, China.
⁵ Department of Applied Mathematics, Hong Kong Polytechnic University, Hong Kong, China.
⁶ School of Public Health, Shanghai Jiao Tong University School of Medicine, Shanghai, China.

Abstract

Background: Several recent studies reported a positive (statistical) association between ambient nitrogen dioxide (NO₂) and COVID-19 transmissibility. However, considering the intensive transportation restriction due to lockdown measures that would lead to declines in both ambient NO₂ concentration and COVID-19 spread, the crude or insufficiently adjusted associations between NO₂ and COVID-19 transmissibility might be confounded. This study aimed to investigate whether transportation restriction confounded, mediated, or modified the association between ambient NO₂ and COVID-19 transmissibility. Methods: The time-varying reproduction number (R_t ) was calculated to quantify the instantaneous COVID-19 transmissibility in 31 Chinese cities from January 1, 2020, to February 29, 2020. For each city, we evaluated the relationships between ambient NO₂, transportation restriction, and COVID-19 transmission under three scenarios, including simple linear regression, mediation analysis, and adjusting transportation restriction as a confounder. The statistical significance (p-value < 0.05) of the three scenarios in 31 cities was summarized. Results: We repeated the crude correlational analysis, and also found the significantly positive association between NO₂ and COVID-19 transmissibility. We found that little evidence supported NO₂ as a mediator between transportation restriction and COVID-19 transmissibility. The association between NO₂ and COVID-19 transmissibility appears less likely after adjusting the effects of transportation restriction. Conclusions: Our findings suggest that the crude association between NO₂ and COVID-19 transmissibility is likely confounded by the transportation restriction in the early COVID-19 outbreak. After adjusting the confounders, the association between NO₂ and COVID-19 transmissibility appears unlikely. Further studies are warranted to validate the findings in other regions.

Keywords: COVID-19; China; nitrogen dioxide; reproduction number; transportation.

Publication types

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

MeSH terms

COVID-19*
Cities
Communicable Disease Control
Humans
Nitrogen Dioxide* / analysis
SARS-CoV-2

Substances

Nitrogen Dioxide