Extremely small particles of pollution have the potential to evade the lungs’ protective filter system and end up deep in the body, scientists suggest. Researchers speculate the particles could then build up in blood vessels and raise the risk of heart disease. They say their early study – based on extremely small particles of gold – brings them a step closer to cracking the “mystery” of how air pollution and heart disease and stroke are linked. Air pollution is estimated to help shorten of the lives of about 40,000 people a year in the UK. Several studies suggest it does this in the most part by worsening or triggering heart or lung problems. But despite many theories, exactly how air pollution affects the heart is not fully understood. Some scientists suspect that it may be partly down to extremely tiny pollution particles (known as nanoparticles) that could potentially be too small to be removed by the body’s filter system in the nose and lungs. To investigate researchers, from the University of Edinburgh and universities in the Netherlands studied extremely small particles of inert gold – at a similar size to those found in diesel exhaust fumes. Scientists asked 14 healthy volunteers to breathe in air containing pieces of gold, which scientists consider inert, while exercising for two hours. A day later, researchers found that gold nanoparticles had made their way into the bloodstream of most participants. And for some people, the particles remained in the body for months – they were detected in people’s urine three months later.