The team of researchers from Zuyd University in the Netherlands reached this conclusion after conducting a study examining how the brain is affected by diesel exhaust fumes.
The study, which set out to replicate the environment experienced by those who work in a garage or by the roadside, involved 10 volunteers spending an hour in a room filled either with clean air or exhaust from a diesel engine.
Though scientists have known for some time that nanoparticles from exhaust fumes reach the brain when inhaled, this is the first time that scientists have demonstrated that inhalation actually alters brain activity.
The volunteers were wired up to an electroencephalograph (EEG), a device that records the electrical signals of the brain and were monitored during the period of exposure and for an hour after they left the room.
The EEG data suggested that within 30 minutes 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.
Lead researcher Paul Borm says what these effects may mean in relation to the chronic exposure to air pollution encountered in busy cities where the levels of such soot particles can be very high, can only be speculated.
He suggests the long-term effects of exposure to traffic nanoparticles may interfere with normal brain function and information processing and more research is needed.
Experts say the results are not altogether surprising and such physiological changes warrant further investigation because there could be a long-term effect.
A study of dogs in Mexico found those who lived in highly-polluted Mexico City had brain lesions similar to those seen in Alzheimer's patients, while those who lived in much less-polluted rural areas showed a much lower rate of damage to the brain.
Studies that expose volunteers to potential toxins or require invasive techniques are limited for ethical reasons.
Borm is currently conducting experiments where volunteers inhale artificially generated nanoparticles that are free from the other chemicals that are generated, along with the nanoparticles in diesel exhaust.
The research is published in the journal Particle and Fibre Toxicology.
