Air pollution linked to increased heart attack risk even at ‘safe’ levels.
Dramatic health consequences of air pollution were first described in Belgium in 1930 after the Meuse Valley fog. The World Health Organization (WHO) considers air pollution as one of the largest avoidable causes of mortality. Besides the pulmonary and carcinogenic effects of air pollution, exposition to air pollution has been associated with an increased risk in cardiovascular mortality. Ambient air pollution is a mixture of particulate matter (PM) and gaseous pollutants such as sulfur dioxide (SO2), nitric dioxide (NO2) and ozone (O3). Fine particle pollution, also called PM2.5, has the ability to reach the lower respiratory tract and carry a large amount of toxic compound into the body.
Now, a study from researchers at University Hospital Brussels has shown that particulate matter and NO2 air pollution are associated with increased risk of severe heart attacks despite being within European recommended levels. The study was presented at the ESC Congress.
Previous studies show that in addition to the long term consequences, more recent research suggests that acute exposure to air pollution may trigger some cardiovascular events such as strokes, heart failure or myocardial infarction (heart attack). Myocardial infarction covers a number of clinical conditions and the effect of pollution on these subsets is unknown.
The current study investigated the effect of short term exposure to air pollution on the risk of ST-segment elevation myocardial infarction (STEMI). This type of myocardial infarction has the worst prognosis and is caused by thrombotic occlusion of a coronary artery that damages the heart. Results showed that between 2009 and 2013, there were 11 428 hospitalisations for STEMI. Data findings show that 10 μg/m3 increases in ambient PM2.5 concentrations were associated with a 2.8% increase in STEMI while 10 μg/m3 rises in NO2 were associated with a 5.1% increased risk. The team note that these associations were only observed in men.
A subgroup analysis according to age showed that patients aged 75 years and above developed more STEMI in relation to PM10 exposure, while those 54 years and under were more susceptible to NO2. The researchers hypothesize that as NO2 is more related to vehicle emissions, one explanation for this finding could be that the younger population may be exposed to excess NO2 from road traffic due to a higher level of social and professional activities.
Data on PM10, PM2.5, O3 and NO2 levels were obtained from Belgian Environmental Agency air pollution records in the current study. A statistical model called RIO was used to provide a real-time evaluation of air pollution exposure in each part of Belgium with adjustments for population density. Data on STEMI incidence came from the Belgian Interdisciplinary Working Group on Acute Cardiology (BIWAC) STEMI registry, using STEMI hospitalisation as a proxy indicator. The relationship between pollutants and STEMI was assessed using a case-crossover design and performed by the biostatistics department of Université Libre de Bruxelles (ULB), Brussels, Belgium.
The lab state that the association between STEMI and air pollution was observed within one day of exposure. They go on to stress that this was despite the fact that concentrations of air pollutants were within the European air quality standard. The team note that it’s possible that only men were affected because of the under representation of women in their study population which was less than 25%.
The researchers surmise that to their knowledge this is the first study to examine the effect of air pollution on STEMI occurrence at a national level using a prospective observational registry of unselected patients. Their study showed that particulate and NO2 air pollution, at levels below European limits, are associated with an increased risk of STEMI. The group conclude that the detrimental impact of NO2 exceeds that of fine particles and raises new public health concerns which need further investigation.
Source: European Society of Cardiology