ASSESSING THE ACUTE AND CHRONIC CARDIO-RESPIRATORY HEALTH IMPACTS OF AMBIENT AIR POLLUTION IN CHINA

Background
Both the acute and chronic health impacts of ambient air pollution (AAP) are now consistently documented throughout epidemiological literature. However, the majority of evidence currently applies to developed regions where both health outcome data and pollutant data are more readily obtainable with greater degree of quality assurance. Thus, generic extrapolation of the health impacts from developed regions into low and/or middle income countries (LMIC's) including China is increasingly common within the evidence base. Such extrapolation of results often presents as the better option, with research in LMIC's themselves frequently restricted by methodological issues. These issues stem from their complex healthcare systems, lack of unified health data recording, and consistent exposure misclassification. Therefore, evidence on the health impacts of AAP exposure for populations within LMIC's exclusively remains anecdotal.
Within China specifically, economic development has flourished at the inherent sacrifice of air quality, with AAP causing an estimated 1.6 million deaths annually (1). However, even within China there remains significant uncertainty in terms of the exact health impacts of AAP exposure on the population. Furthermore, the majority of high quality epidemiological studies are performed within the Chinese "mega-cities" with little consideration for the health effects in wider regions, despite the ubiquity of AAP exposure. This project therefore aims to accurately determine the acute and chronic health effects of AAP exposure within varying regions of China, using a methodology previously reserved almost exclusively for developed regions.
Methods
This project will utilise China Kadoorie Biobank (CKB), a cohort of 0.5 million participants covering 10 diverse regions of China. The availability of high quality standardised health data through health insurance data linkage will enable health outcomes to be accurately examined in relation to AAP exposure for individuals within the CKB.
The acute health effects of AAP exposure will be examined in terms of both cardiovascular and respiratory hospital admissions, documented from five urban areas in China. This will involve single pollutant modelling for the primary air pollutants (PM2.5, PM10, SO2, NOx, O3) obtained from the Chinese National Air pollution monitoring network. Time-series analysis (using pre-specified lags) will be performed, and generalised additive models generated in order to accurately determine the association between AAP exposure and acute cardiovascular/respiratory events for CKB participants. Unlike the majority of studies which focus solely on single pollutant modelling from fixed monitoring sites, this project will perform sensitivity analysis utilising multi-pollutant modelling. It will also examine various potential effect modifiers such as differing geographic region, in addition to the main confounders including demographic characteristics, seasonal trends, and meteorological variables.
In terms of the chronic health impacts of AAP exposure, this will involve examining;
- The association of long term AAP exposure and blood pressure/hypertension in CKB participants.
- The association of long term AAP exposure and incidence of cardiovascular/respiratory disease in CKB participants.
To quantify long term exposure to AAP for CKB participants, satellite based estimates of PM2.5 will be utilised with further calibration from fixed monitoring measurements and personal exposure assessment. These methods of exposure assessment will minimise exposure misclassification providing a more reliable estimate of the health impacts of AAP exposure in China.
Bibliography
(1) Institute for Health Metrics and Evaluation. Poor air quality kills 5.5 million annually. 2016; Available at: http://www.healthdata.org/news-release/poor-air-quality-kills-55-million-worldwide-annually. Accessed 24/10, 2016.