Assessing and improving the evidence synthesis of gestational ambient air pollution exposure and the risk of preterm birth: a systematic review, meta-analysis and health impact assessment
File(s)
Author(s)
Lee, Shawn Yu-Cheng
Type
Thesis
Abstract
Systematic reviews and meta-analyses of gestational air pollution exposure and the risk of PTB have methodological shortcomings and inconsistencies in their findings, which hindered the use of their findings as concentration-response functions (CRF) in health impact assessments (HIA). A comprehensive update for the effect of gaseous pollutants was also needed. The aim of this thesis was to conduct a high quality, rigorous, up-to-date systematic review and meta-analysis of gestational exposure to PM2.5, NO2, O3, and the risk of PTB, with methodological improvements made in areas such as quality assessment and analysis of study dependencies. Whole pregnancy PM2.5 exposure was associated with an increase in the risk of PTB (OR: 1.10 [1.06-1.14], per 10 μg/m3 increment, n=34, I2=92%), moderate-to-late PTB, and very PTB. Trimester 3 NO2 exposure was associated with an increase in the risk of PTB (OR: 1.20 [1.07-1.34], per 10 μg/m3 increment, n=16, I2=99%). No associations were found for O3. Factors such as exposure assessment method were partial drivers of the high heterogeneity observed. Coupled with the findings from the narrative synthesis, the relationship between PM2.5 exposure and the risk of PTB was deemed “likely to be causal”, whereas that of NO2 exposure and the risk of PTB was “suggestive of, but not sufficient to infer” a causal relationship. Using the increase in risk of PTB associated with whole pregnancy PM2.5 exposure as a CRF, HIA was conducted to quantify the impact of PM2.5 reduction caused by Net-Zero policies in England. Approximately 27,000 PTBs would be averted if the Balanced Net Zero Pathway instead of a business-as-usual scenario was adopted, and it will result in a monetised benefit of £6,000,000,000 from 2019 to 2154. The findings in this thesis reaffirms the necessity of high-quality evidence synthesis and encourage the inclusion of PTB as an outcome in future HIAs.
Date Issued
2024-11-24
Date Awarded
2025-04-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Walton, Heather
Smith, Rachel
Exley, Karen
Sponsor
National Institute for Health Research (Great Britain)
Publisher Department
School of Public Health
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)