| This study examines changes in brain activity, particularly in the frontal cortex, that result from exposure to diesel exhaust (DE), which is a mixture of non-engineered nanoparticles and exhaust compounds. Further human studies are necessary to determine whether nanoparticles in DE are responsible for these effects and if so, by what mechanism. |
Reviewed by Linda Cohen, MPH, Environ International Corp.
Background
Diesel exhaust (DE) has been identified as an important component of particulate matter (PM) exposure in several epidemiological studies that examine adverse health effects from environmental exposures. Additionally, studies have suggested that inhaled nanoparticles can travel or translocate to the brain via the olfactory nerves, and inflammatory changes have been associated with the site of deposition. This finding is of concern, since nanoparticles may be associated with changes at the cellular level that have been connected to the development of neurodegenerative diseases and possibly impaired cognitive function.
Objective
The objective of this study was to investigate short-term changes in brain function from exposure to PM and components less than 100 nm.
Participants/Methods
Ten male study participants ranged in age from 18-39 years. Volunteer participants were randomly assigned to two groups – one exposed to diesel exhaust, the other to filtered air. Brain activity was measured, and after 2 to 4 days, participants were exposed to the other “condition”. Brain activity in the form of quantitative electroencephalography (EEG) readings was continuously recorded in eight areas of the brain for one hour during and after each exposure. Significance levels of differences (p<0.05) between average values of the readings by DE-exposed or control status were presented.
Evidence
Initial baseline brain activity measurements did not differ from pre-exposure conditions inside/outside the exposure chamber. No significant differences in EEG readings between subjects were seen in the first 5 minutes of diesel or control conditions. After 30 minutes, a slow increase in EEG parameters of all subjects was observed, which was stronger in subjects exposed to diesel exhaust compared to control conditions. This observed effect was more pronounced at the frontal electrode sites than at the other sites tested. This increasing trend continued during the diesel post-exposure period.
In other analyses, diesel exposure correlated with a significant increase in fast wave activity at frontal electrode sites compared to control conditions. In 7 out of 10 subjects, a marked increase in this activity was observed at the end of the diesel exposure interval, but not under control conditions. Similar changes in fast wave activity were not observed in central and parietal electrode sites.
Results
Results of this study include a delayed response in the frontal cortex to DE exposure, possibly indicating increased brain activity of the left frontal cortex during and after exposure. The authors suggest that this change in brain activity is due to an effect of nanoparticles that penetrate the brain or impact neural signaling. Effects on the frontal cortex from chronic exposure to PM and/or nanoparticles is uncertain. The authors conclude that further studies to establish whether other nanoparticles induce functional effects in the human brain and to investigate the clinical implications of these findings are necessary.
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported.
