Air pollution is associated with increased mortality and risk of a variety of age-related diseases, but as is often the case in human epidemiological data it isn't all that clear as how much of this is due to direct versus indirect effects. Lesser degrees of air pollution are associated with wealthier regions of the world, for example, and wealth in turn correlates with lower mortality and less age-related disease. That said, there are range of direct mechanisms for air pollution to impact long-term health, some with better accompanying evidence than others, such as the one explored here:
Tiny particles in air pollution have been associated with cardiovascular disease, which can lead to premature death. But how particles inhaled into the lungs can affect blood vessels and the heart has remained a mystery. Now, scientists have found evidence in human and animal studies that inhaled nanoparticles can travel from the lungs into the bloodstream, potentially explaining the link between air pollution and cardiovascular disease.
The World Health Organization estimates that in 2012, about 72 percent of premature deaths related to outdoor air pollution were due to ischemic heart disease and strokes. Pulmonary disease, respiratory infections and lung cancer were linked to the other 28 percent. Many scientists have suspected that fine particles travel from the lungs into the bloodstream, but evidence supporting this assumption in humans has been challenging to collect. So researchers used a selection of specialized techniques to track the fate of inhaled gold nanoparticles.
In the new study, 14 healthy volunteers, 12 surgical patients and several mouse models inhaled gold nanoparticles, which have been safely used in medical imaging and drug delivery. Soon after exposure, the nanoparticles were detected in blood and urine. Importantly, the nanoparticles appeared to preferentially accumulate at inflamed vascular sites, including carotid plaques in patients at risk of a stroke. The findings suggest that nanoparticles can travel from the lungs into the bloodstream and reach susceptible areas of the cardiovascular system where they could possibly increase the likelihood of a heart attack or stroke.