Effect of diesel exhaust inhalation on blood markers of inflammation and neurotoxicity: a controlled, blinded crossover study.

CONTEXT: Epidemiological studies and animal research have suggested that air pollution may negatively impact the central nervous system (CNS). Controlled human exposure studies of the effect of air pollution on the brain have potential to enhance our understanding of this relationship and to inform potential biological mechanisms. OBJECTIVES: Biomarkers of systemic and CNS inflammation may address whether air pollution exposure induces inflammation, with potential for CNS negative effects. MATERIALS AND METHODS: Twenty-seven healthy adults were exposed to two conditions: filtered air (FA) and diesel exhaust (DE) (300 µg PM2.5/m(3)) for 120 min, in a double-blinded crossover study with exposures separated by four weeks. Prior to and at 0, 3, and 24 h following each exposure, serum and plasma were collected and analyzed for inflammatory cytokines interleukin 6 (IL-6) and tumour necrosis factor alpha (TNF-α), the astrocytic protein S100b, the neuronal cytoplasmic enzyme neuron-specific enolase (NSE), and serum brain-derived neurotrophic factor (BDNF). We hypothesized that IL-6, TNF-α, S100b and NSE would increase, and BDNF would decrease, following DE exposure. RESULTS: At no time-point following exposure to DE was a significant increase in concentration from baseline seen for IL-6, TNF-α, S100b, or NSE relative to FA exposure. Similarly, no significant decrease in BDNF concentration from baseline was seen following DE exposure, relative to FA. Furthermore, the repeated measures ANOVA considered for all time-points and biomarkers revealed no significant time-exposure interaction. DISCUSSION AND CONCLUSION: These results suggest that short-term exposure to DE amongst healthy adults does not acutely affect the systemic or CNS biomarkers that we measured.

Acute diesel exhaust exposure and postural stability: a controlled crossover experiment.

Recent epidemiological evidence connects ambient air pollutants to adverse neurobehavioural effects in adults. In animal models, subchronic controlled exposures to diesel exhaust (DE) have also showed evidence of neuroinflammation. Evidence suggests that DE not only affects outcomes commonly associated with cognitive dysfunction, but also balance impairment. We conducted a controlled human exposure experiment with 28 healthy subjects (average age = 28 years (SD = 7.1; range = 21-49); and 40% female) who were exposed to two conditions, filtered air (FA) and DE (300 µg PM2.5/m3) for 120 min, in a double-blinded crossover study with randomized exposures separated by four weeks. Postural stability was assessed by the Balance Error Scoring System (BESS), a brief, easily-administered test of static balance. The BESS consists of a sequence of three stances performed on two surfaces. With hands on hips and eyes closed, each stance is held for 20 s. "Error" points are awarded for deviations from those stances. Pre- and immediately post-exposure BESS "error" point totals were calculated and the difference between the two timepoints were compared for each of the two exposure conditions. A mixed effect model assessed the significance of the association. While our data demonstrates a trend of reduced postural stability in response to exposure to DE, exposure was not significantly associated with BESS value. This is the first study to investigate changes in postural stability as a result of exposure to DE in human subjects.