Short-term exposure to air pollution could increase a person’s risk of irregular heartbeat or blood clots in the lung, a study has suggested. But researchers found “no clear evidence” of effects of short-term pollution on a certain type of heart attack or stroke.

The authors from the London School of Hygiene and Tropical Medicine wanted to examine the biological impact of short-term air pollution on cardiovascular events.

They used data from three databases across England and Wales about heart attacks, hospital admissions and deaths for 2003-09 and compared them to recorded pollution events.

Air pollution was responsible for 3.7 million deaths in 2012

The study, published in the journal Heart, looked at some 400,000 heart attacks, more than two million emergency admissions for cardio-vascular problems and 600,000 deaths from cardiovascular disease. These were linked to average levels of air pollutants over five days from the monitoring station nearest to the residence. They measured various types of air pollutants including carbon monoxide, nitrogen dioxide, particulate matter less than 10 micrometres in aerodynamic diameter (PM10), PM2.5, sulphur dioxide and ozone.

No clear link with any air pollutant was found for cardiovascular deaths, with the exception of PM2.5 which was linked to an increased risk of irregular heart rhythms, irregular heartbeat and blood clots in the lungs.

Only nitrogen dioxide was linked to an increased risk of a hospital admission for cardiovascular problems, including heart failure, and an increased risk of a particular type of heart attack.

Earlier this year, it estimated that outdoor air pollution was globally responsible for 3.7 million deaths in 2012.