Research in context
Evidence before this study
At study launch, there was no literature on progression of atherosclerosis in relation to long-term exposure to air pollution; the study was in response to the US Environmental Protection Agency's Request For Applications for a prospective observational study of cardiovascular disease initiation and progression associated with long-term exposure to ambient particulate matter and other air pollutants in a population-based sample. Although previous research has been considered to be consistent with a causal relationship between particulate matter air pollution and ischaemic heart disease events and mortality, these studies had substantial limitations and biological plausibility has continued to be questioned. Previous studies have had short follow-up durations, little attention to fine-scale variation in pollutant exposure, and comprised secondary analyses of existing datasets collected to test other hypotheses.
Added value of this study
This study provides important new information about the underlying biological processes of long-term exposure to air pollutant concentrations and their association with cardiovascular disease, through repeated assessment of coronary artery calcification by CT (a surrogate of atherosclerosis extent) in a cohort and with an unprecedented effort to characterise air pollutant exposures. The study was specifically designed to address the hypothesis that air pollutants would be associated with progression in subclinical atherosclerosis.
Exposures assessed in this study are low and relevant for understanding the health effects of ambient environments occurring nowadays in high-income, low-income, and rapidly industrialising countries.
Implications of all the available evidence
Together with accumulating observational evidence of the relationship between ambient pollutants and cardiovascular disease events, this study substantially advances the case for global efforts to reduce exposures to ambient air pollutants.