Even 'safe' levels of air pollution up heart attack risk

Particulate matter and nitric dioxide emissions from industrial plants or vehicles increase the risk of heart attacks, despite being within 'safe' levels of air pollution, a new study has claimed.
The study examined the effect of short term exposure to air pollution on the risk of ST-segment elevation myocardial infarction (STEMI).
This type of myocardial infarction (heart attack) has the worst prognosis and is caused by thrombotic occlusion of a coronary artery that damages the heart.
Ambient air pollution is a mixture of particulate matter (PM) and gaseous pollutants such as sulphur 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.
PM2.5 and NO2 originate predominantly from the combustion of fossil fuels such as emissions from industrial plants or vehicles.

Data on PM10, PM2.5, O3 and NO2 levels were obtained from Belgian Environmental Agency air pollution records.
Data on STEMI incidence came from the Belgian Interdisciplinary Working Group on Acute Cardiology (BIWAC) STEMI registry, using STEMI hospitalisation as a proxy indicator.
Between 2009 and 2013, there were 11,428 hospitalisations for STEMI.
Researchers found that 10 microgrammes per cubic metre increases in ambient PM2.5 concentrations were associated with a 2.8 per cent increase in STEMI while 10 microgrammes per cubic metre rises in NO2 were associated with a 5.1 per cent increased risk. These associations were only observed in men.

"The association between STEMI and air pollution was observed within one day of exposure," said Jean-Francois Argacha, a cardiologist at University Hospital Brussels in Belgium.
"This was despite the fact that concentrations of air pollutants were within the European air quality standard," said Argacha.
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.
"Considering that 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," said Argacha.

"We found that particulate and NO2 air pollution, at levels below European limits, are associated with an increased risk of STEMI," said Argacha.