-Jay Farrar – “Feel Free”

There is nothing to induce a simmering fury in me on my morning bicycle commute like following a diesel exhaust spewing, and inconsiderately piloted, bus. The narrow streets of Oxford barely allow for two cars to pass side-by-side – nevermind buses, vans and trucks – and the dark stains on the beautiful sandstone buildings attest to the long term effects of pollution from vehicle exhaust.

A study that I found this week at BioMed Central explores the shorter term effects of one type of vehicle exhaust on peoples brains. It seems that there may be a biological reason for my frustration at tailing a bus into the Oxford city center. Writing in Particle and Fibre Toxicology, a group led by Paul Borm at Zuyd University in the Netherlands looked at brain activity of volunteers exposed to diesel exhaust and found some interesting changes.

Diesel fumes in general have previously been shown to cause pulmonary inflammation and other more systemic health effects. Borm’s group is focused on the particulate matter, particularly nanoparticles, that are plentiful in diesel exhaust. It has been previously shown that nanoparticles can moveto the brain through olfactory nerves. Many of these nanoparticles are strong inducers of oxidative stress, a chemical process that has been implicated in neurodegenerative disease like Parkinson’s and Alzheimer’s.

Based on these previous results, Borm and his colleagues exposed volunteers to either diesel exhaust or filtered air for one hour. During that time, and for an additional hour after exposure, the volunteers’ brain activity was monitored by quantitative electroencephalography (EEG). The researchers found that there was a significant increase in brain activity in response to diesel exhaust particularly in the left frontal cortex after a half hour of exposure. Interestingly, this increase in activity continues even after the diesel exhaust is removed.

So, the take home message is that exposure to diesel exhaust causing some kind of temporary but detectable change in brain activity. The left frontal cortex is a pretty general localization of this activity and there is no empirical data to determine the biological relevance of the increased activity. Borm interprets it as a cortical stress response – the brain trying to deal with potentially dangerous toxins – but they don’t carry out the experiments necessary to determine what is actually happening in the volunteers’ noggins. In addition, the Dutch researchers are really interested in the effect of nanoparticles in particular rather than diesel exhaust more generally so they kind of miss the forest for the nanoparticles. The changes in brain activity alone are interesting as this is the first study to demonstrate a quantitative neurological effect of exposure to diesel exhaust. The more interesting follow-up experiments would focus more specifically on what regions of the brain are being affected, how long the effects last and what level of exposure is required to induce changes.

Jay Farrar’s “Sebastopol” is available from Amazon and .