How a tiny speck of exhaust soot can kill you
Microscopic specks of soot from vehicle exhausts can enter the bloodstream through the lungs and sow seeds of disease in arteries, research suggests.
The carbon nanoparticles, a thousand times smaller than the width of a human hair, are coated with powerful toxins which increase the risk of heart attacks and strokes, scientists believe.
Air pollution, especially from traffic, has been linked to an increased risk of heart and artery disease.
But while the effects of exhaust fume particles on public health are well known, less is understood about what they do in the body.
The study, reported in the journal 'ACS Nano', shows for the first time how the smallest particles pass through the lungs and gather in the most vulnerable areas of blood vessels.
It suggests people who already suffer from artery damage are likely to be hit hardest by inhaled traffic pollution.
Because carbon particles are so hard to trace in the body, the scientists modelled them using non-reactive and harmless gold nanoparticles.
A series of trials in which volunteers were asked to inhale the gold dust showed within 24 hours they migrated from the lungs to the bloodstream, and were still detectable three months later.
Part of the study involved exposing surgical patients at high risk of stroke to the gold particles. Analysis of clogging material removed from the patients' arteries demonstrated that the nanoparticles accumulated in fatty deposits growing inside blood vessels.
Professor Jeremy Pearson, associate medical director at the British Heart Foundation, which co-funded the research, said: "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."