Re: Long term exposure to ambient air pollution and incidence of acute coronary events: prospective cohort study and meta-analysis in 11 European cohorts from the ESCAPE Project
We read the paper by Cesaroni et al. with interest (1), and are encouraged by this addition to the evidence base.
It seems counter-intuitive that larger particles of smoke, dust, and dirt (PM10) are significantly associated with coronary events, but smaller toxic organic compounds and heavy metals (PM2.5) are not. However, this was a multi-centre cohort study including a meta-analysis of its eleven cohorts, and must be considered as part of the wider evidence base.
A systematic review in 2009 by Bhaskaran et al. identified 26 studies with Myocardial Infarction as an outcome and air pollution as a risk factor (2). Only 7 studies were long-term studies and the authors concluded that there was some evidence that PM2.5, PM10, and NO2 were associated with detrimental cardiovascular outcomes, but more studies were needed. A 2006 analysis by Pope et al. provides evidence that long-term exposure to PM2.5 is an important risk factor for cause-specific cardiovascular mortality (3). A study by Miller et al. in 2007 followed over 65800 women in 36 US metropolitan areas for 6 years. They found that each increase of 10 μg/m3 in PM2.5 was associated with an increased Odds Ratio of 1.24 (95% CI 1.09-1.41) for the onset of a first cardiovascular event (4).
There are still questions regarding the cardiovascular effects of air pollution. There are a few long-term studies and this paper contributes to the limited evidence base. Studies presently focus on PM10 and PM2.5, with a gap in the evidence base regarding ultrafine particulate matter (PM0.1).
The EU presently sets an annual concentration limit at 25 µg/m3 for PM2.5 and at 40 µg/m3 for PM10 (5), while in the US, the annual concentration limit is 12 µg/m3 for PM2.5 and there is no annual concentration limit for PM10 (6). In order to ensure consistent guidance, it is important to understand better the role of air pollution and particulate matter on coronary events in particular and health in general. Therefore a comprehensive systematic review and meta-analysis of all available data, such as a Cochrane review, is recommended to inform further guidance on air quality standards.
1. Cesaroni, Giulia, et al. "Long term exposure to ambient air pollution and incidence of acute coronary events: prospective cohort study and meta-analysis in 11 European cohorts from the ESCAPE Project." BMJ: British Medical Journal 348 (2013).
2. Bhaskaran, Krishnan, et al. "Effects of air pollution on the incidence of myocardial infarction." Heart 95.21 (2009): 1746-1759.
3. Pope, C. Arden, et al. "Cardiovascular Mortality and Long-Term Exposure to particulate Air Pollution Epidemiological Evidence of General Pathophysiological Pathways of Disease." Circulation 109.1 (2004): 71-77.
4. Miller, Kristin A., et al. "Long-term exposure to air pollution and incidence of cardiovascular events in women." New England Journal of Medicine 356.5 (2007): 447-458.
5. European Commission. 2014. Air Quality Standards. (online) Available at: http://ec.europa.eu/environment/air/quality/standards.htm (Accessed:5 Feb 2014)
6. Esworthy R. 2013. Air Quality: EPA’s 2013 Changes to the Particulate Matter (PM) Standard. (online) Available at:
http://www.fas.org/sgp/crs/misc/R42934.pdf (Accessed:5 Feb 2014)
Competing interests: No competing interests