Diesel exhaust fumes not only stink, they may alter the way the brain functions, a study released Tuesday suggests.

In the journal Particle and Fibre Toxicology, researchers from the Netherlands, Sweden and the United Kingdom report that even a half hour's exposure to the fumes can put stress on the brain.

Previous research has suggested that very small particles breathed in from polluted air can end up in the brain, but "this is the first study to demonstrate functional changes in brain activity as a result of exposure to diesel exhaust in human subjects," the team writes.  

Researchers monitored 10 male volunteers who spent an hour in a room filled either with clean air or exhaust from a diesel engine. The exhaust-filled room was set to mimic the highest level that people might encounter in the environment or at work, for example on a busy road or in a garage.

Volunteers were connected to an electroencephalograph (EEG) to monitor the brain's electrical signals during exposure and for the hour afterwards.

Within 30 minutes, the participants in the exhaust room showed signs of stress on the EEG, indicating a change in the way the brain processes information.

The researchers said the effect continued in the hour after the participants left the room.

"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," lead researcher Paul Borm said in a release.

"It is conceivable that the long-term effects of exposure to traffic nanoparticles may interfere with normal brain function and information processing," he said, adding that further studies would be necessary to determine whether exposure has a lasting effect.

Such findings are significant, the researchers said, because this type of stress, as a consequence of particles depositing in tissue, has been linked to the development of Parkinson's and Alzheimer's disease.