Diesel exhaust stresses brain

Previous studies have shown that particle matter from air pollution, even if measured in billionths of an metre, can end up lodged in the brain. But this is the first time scientists have demonstrated that inhalation of these nanoparticles actually alters brain activity, says the study, published in the British journal Particle and Fibre Toxicology.

In experiments led by Paul Borm from Zuyd University in the Netherlands, 10 volunteers spent one hour in a room filled with either clean air or exhaust from a diesel engine. The human guinea pigs were wired up to an electroencephalograph (EEG), which monitored their brain waves for the exposure period and for one hour after they left the room.

What the study showed
The researchers found that after about 30 minutes the diesel exhaust started to induce a stress response in the brain cortex, as shown by electrical activity in this region.

Stress continued to increase even after the subjects were no longer exposed to the fumes. The concentration of diesel exhaust was the equivalent to the highest level people might encounter in the environment or at work, for example on a busy road or in a garage.

"We believe our findings are due to an effect nanoparticles or 'soot' particles that are major component of diesel exhaust," said Borm. "We can only speculate what these effects may mean for the chronic exposure to air pollution encountered in busy cities where the levels of such soot particles can be very high."

One possible explanation for the change in brain function, said Borm, is that particles depositing in tissue can cause oxidative stress, which has been implicated in degenerative brain diseases such as Parkinson's and Alzheimer's.

Long-term effects of exposure to traffic nanoparticles "may interfere with normal brain function and information processing," noted Borm. – (Sapa)

March 2008

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