Long-term exposure to ambient NO2 and adult mortality: A nationwide cohort study in China

Yunquan Zhang; Zunyan Li; Jing Wei; Yu Zhan; Linjiong Liu; Zhiming Yang; Yuanyuan Zhang; Riyang Liu; Zongwei Ma

doi:10.1016/j.jare.2022.02.007

Long-term exposure to ambient NO₂ and adult mortality: A nationwide cohort study in China

J Adv Res. 2022 Nov:41:13-22. doi: 10.1016/j.jare.2022.02.007. Epub 2022 Feb 18.

Authors

Yunquan Zhang¹, Zunyan Li², Jing Wei³, Yu Zhan⁴, Linjiong Liu², Zhiming Yang⁵, Yuanyuan Zhang², Riyang Liu⁶, Zongwei Ma⁶

Affiliations

¹ Department of Epidemiology and Biostatistics, School of Public Health, Wuhan University of Science and Technology, Wuhan, Hubei, China; Hubei Province Key Laboratory of Occupational Hazard Identification and Control, Wuhan University of Science and Technology, Wuhan, Hubei, China. Electronic address: YunquanZhang@wust.edu.cn.
² Department of Epidemiology and Biostatistics, School of Public Health, Wuhan University of Science and Technology, Wuhan, Hubei, China.
³ Department of Chemical and Biochemical Engineering, Iowa Technology Institute, The University of Iowa, Iowa City, IA 52242, USA.
⁴ Department of Environmental Science and Engineering, Sichuan University, Chengdu, Sichuan, China.
⁵ School of Economics and Management, University of Science and Technology Beijing, Beijing, China.
⁶ State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu, China.

Abstract

Introduction: A number of population-based studies have investigated long-term effects of nitrogen dioxide (NO₂) on mortality, while great heterogeneities exist between studies. In highly populated countries in Asia, cohort evidence for NO₂-mortality association was extensively sparse.

Objectives: This study aimed to quantify longitudinal association of ambient NO₂ exposure with all-cause mortality in Chinese adults.

Methods: A national cohort of 30,843 adults were drawn from 25 provincial regions across mainland China, and followed up from 2010 through 2018. Participants' exposures to ambient air pollutants were assigned according to their residential counties at baseline, through deriving monthly estimates from high-quality gridded datasets developed by machine learning methods. Cox proportional hazards models with time-varying exposures were utilized to assess the association of all-cause mortality with long-term exposure to ambient NO₂. NO₂-attributable deaths in China were estimated by province and county for years 2010 and 2018, with reference to the counterfactual exposure of 6.9 μg/m³ (the lowest county-level average in this cohort).

Results: We observed a total of 1662 deaths during 224020 person-years of follow-up (median 8.1 year). An approximately linear NO₂-mortality relation (p = 0.273 for nonlinearity) was identified across a broad exposure range of 6.9-57.4 μg/m³. Per 10-µg/m³ increase in annual NO₂ exposure was associated with an hazard ratio of 1.127 (95% confidence interval: 1.042-1.219, p = 0.003) for all-cause mortality. Risk estimates remained robust after additionally adjusting for the confounding effects of co-pollutants (i.e., PM_2.5 or/and O₃). In 2018, 1.65 million deaths could be attributed to ambient NO₂ exposure (national average 17.3 µg/m³) in China, representing a decrease of 4.3% compared with the estimate of 1.72 million in 2010 (20.5 µg/m³).

Conclusion: This cohort study provided national evidence for elevated risk of all-cause mortality associated with long-term exposure to ambient NO₂ in Chinese adults.

Keywords: Adult mortality; Air pollution; Attributable deaths; Cohort study; Nitrogen dioxide.

Publication types

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

MeSH terms

Adult
Air Pollution* / adverse effects
Air Pollution* / analysis
China / epidemiology
Cohort Studies
Environmental Exposure / adverse effects
Environmental Exposure / analysis
Humans
Nitrogen Dioxide* / analysis

Substances

Nitrogen Dioxide