Individual and joint associations of long-term exposure to air pollutants and cardiopulmonary mortality: a 22-year cohort study in Northern China

Wenzhong Huang; Yang Zhou; Xi Chen; Xiaowen Zeng; Luke D Knibbs; Yunting Zhang; Bin Jalaludin; Shyamali C Dharmage; Lidia Morawska; Yuming Guo; Xueli Yang; Liwen Zhang; Anqi Shan; Jie Chen; Tong Wang; Joachim Heinrich; Meng Gao; Lizi Lin; Xiang Xiao; Peien Zhou; Yunjiang Yu; Naijun Tang; Guanghui Dong

doi:10.1016/j.lanwpc.2023.100776

Individual and joint associations of long-term exposure to air pollutants and cardiopulmonary mortality: a 22-year cohort study in Northern China

Lancet Reg Health West Pac. 2023 May 4:36:100776. doi: 10.1016/j.lanwpc.2023.100776. eCollection 2023 Jul.

Authors

Wenzhong Huang^{1

2}, Yang Zhou³, Xi Chen^{4

5

6}, Xiaowen Zeng¹, Luke D Knibbs^{7

8}, Yunting Zhang¹, Bin Jalaludin^{9

10

11}, Shyamali C Dharmage¹², Lidia Morawska¹³, Yuming Guo², Xueli Yang^{4

5

6}, Liwen Zhang^{4

5

6}, Anqi Shan^{4

5

6}, Jie Chen¹⁴, Tong Wang¹⁵, Joachim Heinrich¹⁶, Meng Gao¹⁷, Lizi Lin¹, Xiang Xiao^{17

18}, Peien Zhou¹⁹, Yunjiang Yu³, Naijun Tang⁴, Guanghui Dong¹

Affiliations

¹ Guangdong Provincial Engineering Technology Research Center of Environmental Pollution and Health Risk Assessment, Department of Occupational and Environmental Health, School of Public Health, Sun Yat-sen University, Guangzhou 510080, China.
² Climate, Air Quality Research Unit, School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia.
³ State Environmental Protection Key Laboratory of Environmental Pollution Health Risk Assessment, South China Institute of Environmental Sciences, Ministry of Environmental Protection, Guangzhou 510655, China.
⁴ Department of Occupational and Environmental Health, School of Public Health, Tianjin Medical University, Tianjin 300070, China.
⁵ Tianjin Key Laboratory of Environment, Nutrition and Public Health, Tianjin Medical University, Tianjin 300070, China.
⁶ Center for International Collaborative Research on Environment, Nutrition and Public Health, Tianjin 300070, China.
⁷ Faculty of Medicine and Health, School of Public Health, The University of Sydney, NSW 2006, Australia.
⁸ Public Health Research Analytics and Methods for Evidence, Public Health Unit, Sydney Local Health District, Camperdown, NSW 2050, Australia.
⁹ Centre for Air Quality and Health Research and Evaluation, Glebe, NSW 2037, Australia.
¹⁰ Ingham Institute for Applied Medial Research, Liverpool, NSW 2170, Australia.
¹¹ School of Public Health and Community Medicine, The University of New South Wales, Kensington, NSW 2052, Australia.
¹² Allergy and Lung Health Unit, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, VIC 3052, Australia.
¹³ International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, QLD 4001, Australia.
¹⁴ Department of Occupational and Environmental Health, School of Public Health, China Medical University, Shenyang 110122, China.
¹⁵ School of Public Health, Shanxi Medical University, Taiyuan 030001, China.
¹⁶ Institute and Clinic for Occupational, Social and Environmental Medicine, University Hospital, LMU Munich, Munich 80336, Germany.
¹⁷ Department of Geography, Hong Kong Baptist University, Hong Kong SAR, China.
¹⁸ Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA.
¹⁹ Department of Public Health & Primary Care, University of Cambridge, Cambridge CB2 1TN, United Kingdom.

Abstract

Background: Evidence on the associations between long-term exposure to multiple air pollutants and cardiopulmonary mortality is limited, especially for developing regions with higher pollutant levels. We aimed to characterise the individual and joint (multi-pollutant) associations of long-term exposure to air pollutants with cardiopulmonary mortality, and to identify air pollutant that primarily contributes to the mortality risk.

Methods: We followed 37,442 participants with a mean age of 43.5 years in four cities in northern China (Tianjin, Shenyang, Taiyuan, and Rizhao) from January 1998 to December 2019. Annual particulate matter (PM) with diameters ≤2.5 μm (PM_2.5), ≤10 μm (PM₁₀), sulfur dioxide (SO₂) and nitrogen dioxide (NO₂) were estimated using daily average values from satellite-derived machine learning models and monitoring stations. Time-varying Cox proportional hazards model was used to evaluate the individual association between air pollutants and mortality from non-accidental causes, cardiovascular diseases (CVDs), non-malignant respiratory diseases (RDs) and lung cancer, accounting for demographic and socioeconomic factors. Effect modifications by age, sex, income and education level were also examined. Quantile-based g-Computation integrated with time-to-event data was additionally applied to evaluate the co-effects and the relative weight of contributions for air pollutants.

Findings: During 785,807 person-years of follow-up, 5812 (15.5%) died from non-accidental causes, among which 2932 (7.8%) were from all CVDs, 479 (1.3%) from non-malignant RDs, and 552 (1.4%) from lung cancer. Long-term exposure to PM₁₀ (mean [baseline]: 136.5 μg/m³), PM_2.5 (mean [baseline]: 70.2 μg/m³), SO₂ (mean [baseline]: 113.0 μg/m³) and NO₂ (mean [baseline]: 39.2 μg/m³) were adversely and consistently associated with all mortality outcomes. A 10 μg/m³ increase in PM_2.5 was associated with higher mortality from non-accidental causes (hazard ratio 1.20; 95% confidence interval 1.17-1.23), CVDs (1.23; 1.19-1.28), non-malignant RDs (1.37; 1.25-1.49) and lung cancer (1.14; 1.05-1.23). A monotonically increasing curve with linear or supra-linear shape with no evidence of a threshold was observed for the exposure-response relationship of mortality with individual or joint exposure to air pollutants. PM_2.5 consistently contributed most to the elevated mortality risks related to air pollutant mixture, followed by SO₂ or PM₁₀.

Interpretation: There was a strong and positive association of long-term individual and joint exposure to PM₁₀, PM_2.5, SO₂, and NO₂ with mortalities from non-accidental causes, CVDs, non-malignant RDs and lung cancer in high-exposure settings, with PM_2.5 potentially being the main contributor. The shapes of associations were consistent with a linear or supra-linear exposure-response relationship, with no lower threshold observed within the range of concentrations in this study.

Funding: National Key Research and Development Program of China, the China Scholarship Council, the National Natural Science Foundation of China, Natural Science Foundation of Guangdong Province.

Keywords: Air pollution; Cardiorespiratory disease; Cohort study; Joint association; Lung cancer; Mortality.