January 21, 2014

expert reaction to air pollution, heart attacks and angina

A study in the BMJ found long term exposure to particulate matter in outdoor air, at levels within legally acceptable limits, is strongly linked to heart attacks and angina.

Professor Jon Ayres, Professor of Environmental and Respiratory Medicine, University of Birmingham, said:

“The findings of the ESCAPE project have been awaited eagerly for some time.  Its strengths are its size, the use of the same methodology across all centres and the fact that the findings are remarkably consistent across centres.  It has been known for many years that particulate pollution (both PM10 and its sub-set PM2.5) is associated with coronary events, but previous studies of the effect on first coronary events have been variable.  This European prospective study shows that PM is associated with a first coronary event after allowing for other risk factors for coronary events such as, for example, cigarette smoking, hypertension and a family history of cardiac disease.  The effect size is in the same ball park as previous positive studies but the size of the study adds strength to the findings. 

“Importantly, these effects are seen at PM concentrations below the current EU air quality standards.  There is no doubt that further reduction of PM levels would result in improvements in cardiac health in Europe.  One can only hope that our European politicians will be persuaded of the importance of these findings and reassess their position on air pollution in Europe.”

Dr Jeremy Langrish, Clinical Lecturer and Specialty Registrar in Cardiology, University of Edinburgh, said:

“This landmark paper confirms in a contemporary European population (where air pollution levels are generally low) associations demonstrated in large US cohorts, that long-term exposure to particulate matter air pollution is associated with an increased risk of suffering a heart attack (myocardial infarction). There is insufficient data presented to comment on the association between exposure to air pollutants and angina (pain due to impaired blood flow to the heart).

“These data suggest that for each increase in 5 µg/m3 long-term exposure to PM2.5 air pollution, there is a 13% relative increase in the incidence of acute myocardial infarction after correction of important potential confounders. A difference of 5 µg/m3 in long-term exposure to PM2.5 air pollution would be similar to the difference between living in a UK city compared to a rural area, or living in a less polluted city such as Edinburgh compared to a bigger one like Glasgow, for instance. We should remember that the absolute risk is quite small – in this cohort of >100,000 patients followed for 11.5 years, there were 5157 reported episodes of acute myocardial infarction (5.1% of the population over a 11.5 year period, or 0.45% of the population each year). If we take the baseline risk of 0.45% of the population having an event each year, that equates to around 450 cases/yr, a 13% increase would be an extra 59 cases/yr. What is interesting however, is that in the same cohort, the authors demonstrated no association between exposure and cardiovascular death (see their recent paper in the Lancet, Beelen et al.), suggesting that although the incidence of acute myocardial infarction is increased, this does not lead to an increase in death.

“It is important that these observations were seen at low levels of air pollution, well within the current EU guidelines, and they do support a move towards more stringent air pollution targets, which is likely to have an important effect on public health.”

Professor David Coggon, Professor of Occupational and Environmental Medicine, University of Southampton, said:

“This study adds to the evidence that particulate air pollution is a cause of heart disease, but it does not establish that there are important health risks from levels of exposure below current exposure limits.  This is because the differences in risk that were observed may have been a long-term effect of exposures in the past when levels of pollution were higher.”

Professor Jeremy Pearson, Associate Medical Director at the British Heart Foundation (BHF), said:

“Although it is not widely appreciated, the greatest health consequence of air pollution is now recognised as cardiovascular disease.  Studies conducted by BHF Professor David Newby’s team in Edinburgh over the last 5 years have shown how particles in exhaust fumes affect heart and blood vessel function. And, in a large study last year he showed that air pollution not only leads to a higher incidence of heart attacks but also to worsening of heart failure. 

“This current meta-analysis adds further valuable information, demonstrating how air pollution increases the risk of heart attack even within the currently accepted European pollution limits. This strongly supports the view that public health measures to reduce pollution even further will have significant health benefits.”

‘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’ by Giulia Cesaroni et al. published in the BMJ on Tuesday 21 January 2014.