Getting to the Heart of the Health Effects of Pollution

04 February 2007
Posted by Chris Smith.

Researchers at the University of Rochester, US, have taken an elderly groups of rats on the rodent equivalent of senior citizens road trip to find out how air pollution breathed in by motorists might be harmful to health. Alison Elder and her team wanted to understand why heart attacks seem to occur more often on days when the air quality is bad. They took a collection of aged rats with high-blood pressure on a six hour, 320-mile drive west of New York. Throughout the journey and for five days afterwards the rats, which breathed the same air as any road-user would along the route, had their heart rates, electrocardiograms and blood pressures measured regularly. The study revealed that the well-travelled rats showed a 10% drop in heartrate and a 70% decrease in the responsiveness of their autonomic nervous systems, the neural network that controls subconscious processes like breathing, blood pressure and heart rate. "The fact that exposure to air pollution can change the heart rate, independent of other factors, is a cause for concern," Elder said. "It's important to understand that these changes are taking place outside of the lung. Air pollution is either having a direct effect on the heart in rats or is altering something within the circulatory system." Scientists suspect that the culprit could be ultrafine "nanoparticles" pumped out by engines. They're 60,000 times more numerous than the larger, coarser particles such as PM10s and PM2.5s, which are routinely measured as an index of air pollution. These tiny particles are likely to be able to penetrate deeply into the lungs and enter the circulation. By interacting with blood platelets, which control blood clotting, the particles could increase blood stickiness, making it more likely to form an artery-blocking clot.

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