Previous studies have already suggested that very small particles, called nanoparticles, breathed in from polluted air can end up in the brain. But this is the first time that scientists have demonstrated that inhalation actually alters brain activity.

Ten volunteers spent one hour in a room filled with either clean air or exhaust from a diesel engine. The concentration of diesel exhaust that the subjects breathed was set to the highest level that people might encounter in the environment or at work, for example on a busy road or in a garage.

The subjects were wired up to an electroencephalograph (EEG), and their brain waves were monitored during the exposure period and for one hour after they left the room.

The researchers found that after about 30 minutes the diesel exhaust began to affect brain activity. The EEG data suggested that the brain displayed a stress response, indicative of changed information processing in the brain cortex, which continued to increase even after the subjects had left the exposure chamber.

We believe our findings are due to an effect nanoparticles or ‘soot’ particles that are major component of diesel exhaust. These may penetrate to the brain and affect brain function. 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.

—Paul Borm, lead researcher, Zuyd University in The Netherlands

One link to understanding the mechanism of this effect is that oxidative stress is one consequence of particles depositing in tissue and oxidative stress has also been implicated in degenerative brain diseases such as Parkinson’s and Alzheimer’s disease.

It is conceivable that the long-term effects of exposure to traffic nanoparticles may interfere with normal brain function and information processing. Further studies are necessary to explore this effect, and to assess the relationship between the amount of exposure to particles and the brain’s response and, and investigate the clinical implications of these novel findings.

Resources

• Bjoern Cruts, Ludo van Etten, Hakan Tornqvist, Anders Blomberg, Thomas Sandstrom, Nicholas L Mills and Paul JA Borm. Exposure to diesel exhaust induces changes in EEG in human volunteers. Particle and Fibre Toxicology (in press)