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Air pollution and cardiovascular diseases

Zhao, B ORCID: 0000-0001-5423-971X 2020 , 'Air pollution and cardiovascular diseases', PhD thesis, University of Tasmania.

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Air pollution is a growing public health issue related to global morbidity and mortality and more than half of deaths attributable to exposure to air pollutants are from cardiovascular diseases. However, there are many gaps in the understanding of the links between air pollution and cardiovascular diseases. These include detailed characterisation of the underlying mechanisms and pathways linking air pollution and cardiovascular outcomes; the impacts on long-term cardiovascular development of children who have been exposed to a high-level pollution episode in early life; and short-term associations between ambient air pollution and cardiovascular outcomes such as out-of-hospital cardiac arrest (OHCA) , especially in less polluted settings.
The studies contained in this thesis aimed to research the following: 1) to identify the relationship between air pollution and telomere length (TL) as a possible mediator in linking air pollution with cardiovascular disease risk; 2) to investigate the feasibility of conducting non-invasive vascular assessments and provide normal ranges for very young children at 2 years of age for cardiovascular risk screening; 3) to examine the subsequent vascular health of a group of Australian children who were exposed to coal mine fire emissions during the first two years of life or whose mothers were pregnant at the time of the fire; 4) to assess the association between short-term exposure to ambient air pollution and acute cardiac events in Gunma, Japan; 5) to identify the associations between short-term exposure to ambient particulate matter (PM) and gaseous pollutants and the incidence of OHCA, and to characterise susceptible population groups in a nationwide study in Japan, a country with generally low levels of air pollution.
A systematic review of published manuscripts was conducted firstly (Chapter 2) to identify the association between air pollution and telomere length. Next, the Latrobe Early Life Follow-up (ELF) study was established to examine the health and development of children following the Hazelwood coal mine fire in Victoria, Australia. Chapter 3 summarised the intima-media thickness (IMT), pulse wave velocity (PWV), vascular stiffness index and distensibility among 2-year-old children in the Latrobe ELF study. In Chapter 4, possible associations between exposure to coal mine fire and vascular health of children three years after the fire were assessed. Exposures for each participant were the mean and peak 24-hourly particulate matter with aerodynamic diameter of < 2.5 µm (PM2.5) concentrations during the fire. Outcome measures were carotid IMT and PWV. Chapters 5 and 6 used case-crossover design to determine the association between ambient air pollution and acute cardiovascular events in Japan.
First, 80% of published papers indicated air pollution was associated with shorter TL. Uniform reporting protocol is warranted to estimate the effect size of the influences of air pollution on TL. Second, noninvasive vascular assessments were feasible for cardiovascular risk screening in 2-year-old children and carotid IMT is a preferable option to aortic IMT in this age group. Third, in the postnatal exposure group and the subgroup of children whose mothers smoked during pregnancy or had environmental tobacco smoke (ETS) exposure, there were associations between PM2.5 exposure during coal mine fire and higher vascular stiffness. No associations were found between mine fire exposure and vascular health in the in-utero exposure group. Fourth, short-term exposure to sulfur dioxide (SO2) and nitric oxide (NO) were associated with the increased risk of OHCA but not with other pollutants in Gunma, Japan. Fifth, in the nationwide case-crossover study in Japan, short-term exposure to PM2.5 that is below the current WHO (World Health Organization) or Japanese air quality standards was independently associated with the increased risk of OHCA and patients older than 65 years are more susceptible than younger age groups. Carbon monoxide (CO), photochemical oxidants (Ox) and SO2 were also associated with OHCA in single pollutant models. Nitrogen dioxide (NO2) did not show a positive association with OHCA with lower concentrations in the study setting.
Air pollution plays an important role in the pathogenesis of cardiovascular diseases with some impacts detectable very early in life. As there is an increasing burden of cardiovascular outcomes due to air pollution globally. Effective mitigation, education, preventive and management strategies in communities are warranted, and could lead to important public health benefits even in relatively low pollution settings.

Item Type: Thesis - PhD
Authors/Creators:Zhao, B
Keywords: Air pollution, Cardiovascular disease. Telomere, Vascular health, Children, Out-of-hospital cardiac arrest, Cardiorespiratory health theme
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Copyright 2019 the author

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