It is widely known that there is a link between air pollution and respiratory conditions but the impact that air pollution has on cardiovascular health is perhaps not so well known. The World Health Organisation (WHO) estimated in 2012, that some 72% of outdoor, air pollution-related premature deaths were due to ischaemic heart disease and strokes. Despite this, polling shows that while nine in ten (89%) people know that air pollution can worsen asthma, less than two in ten (17%) are aware that it can also increase their risk of stroke.
Both long and short term exposure to air pollution can make existing heart conditions such as heart failure or angina worse and can cause heart attacks and strokes amongst people with existing cardiovascular disease. The link between air pollution and cardiovascular disease is particularly strong for particulate matter with a diameter under 2.5 micrometres (PM2.5), which is derived from diesel vehicle exhausts. The British Heart Foundation (BHF) funded researchers at the University of Edinburgh who discovered that these tiny particles produce free radicals that can injure blood vessels and lead to disease. The particles prevent blood vessels from relaxing and contracting properly and this disturbance to blood vessel function means there is increased risk of clots developing in coronary arteries, which can cause a heart attack.
Short‐term exposure to high levels of particulate matter has been linked with an increase in the risk of heart attacks within a few hours to one day after exposure.
In 2014, the European Study of Cohorts for Air Pollution Effects (ESCAPE) found that long term exposure to PM2.5 is strongly linked to heart attacks and angina. This study also highlighted that the risk of heart attack and angina increased at levels of PM2.5 exposure below current EU limit thresholds.
There are thought to be a number of ways that air pollution can contribute to cardiovascular disease. Inhaling harmful pollutants could cause inflammation, which may cause the arteries to narrow. These pollutants might also make the blood more likely to clot (which could cause a heart attack in someone who already has coronary heart disease), alter the function of the nervous system causing abnormal heart rhythms or increase blood pressure. The BHF is funding research in this area in order to better understand exactly how air pollution affects the heart and the blood vessels.
The impacts of air pollution are felt most strongly by individuals with existing heart conditions. For this reason it is advised that people with cardiovascular conditions might avoid spending long periods of time in places where there is high levels of air pollution. However this places an unfair burden upon already vulnerable people and it is very difficult for such people to limit their exposure by themselves. That is why the government and local authorities must take steps to improve air quality throughout the UK.
Kylie Barclay is Policy & Public Affairs Officer at the British Heart Foundation