British researchers have found inhaled nanoparticles, especially those coming out of vehicles, enter the bloodstream through the lungs and build up in vessels over a period of time, which runs the risk of a heart attack or stroke.

The new findings, published on Wednesday in the journal ACS Nano, build on previous evidence show the particles we breathe get into our blood and are carried to different parts of the body, including arteries, blood vessels and the heart.

Researchers said these nanoparticles tend to build up in damaged blood vessels of people who already suffer from coronary heart disease – the condition that causes heart attacks – and make it worse.

Experts have long known that air pollution causes serious health risks and can trigger fatal heart attacks and strokes. But until now scientists were not sure how particles inhaled into the lungs go on to affect heart health.

“There is no doubt that air pollution is a killer, and this study brings us a step closer to solving the mystery of how air pollution damages our cardiovascular health,” said Jeremy Pearson, a professor and associate medical director at the British Heart Foundation charity that part-funded the study.

According to a Centre for Science and Environment report, more than 6 lakh people die in India each year due to outdoor air pollution.

“When pollution levels go up, people living with chronic respiratory illnesses like asthma and bronchitis, experience an aggravation of symptoms. Pollution also results in hypertension, increasing the risk of heart attack and stroke. This study is just another proof,” Dr Srikant Sharma, senior consultant physician at Delhi’s Moolchand Hospital, said.