Background
Epidemiological studies have reported associations between air
pollution and neuro-psychological conditions. Biological mechanisms behind
these findings are still not clear.
Objectives
We examined changes in blood and urinary neural biomarkers following
exposure to concentrated ambient coarse, fine and ultrafine particles.
Methods
Fifty healthy non-smoking volunteers, mean age 28 years, were exposed
to coarse (2.5-10 μm, mean 213 μg/m3) and fine
(0.15-2.5 μm, mean 238 μg/m3) concentrated
ambient particles (CAPs), and filtered ambient and/or medical air.
Twenty-five participants were exposed to ultrafine CAP (mean size 59.6 nm,
range 47.0-69.8 nm, mean 136 μg/m3) and filtered medical
air. Exposures lasted 130 minutes, separated by ≥2 weeks, and the
biological constituents endotoxin and β-1,3-D-glucan of each
particle size fraction were measured. Blood and urine samples were collected
pre-exposure, and 1-hour and 21-hour post exposure to determine neural
biomarker levels. Mixed-model regressions assessed associations between
exposures and changes in biomarker levels.
Results
Results were expressed as percent change from daily pre-exposure
biomarker levels. Exposure to coarse CAP was significantly associated with
increased urinary levels of the stress-related biomarkers vanillylmandelic
acid (VMA) and cortisol when compared with exposure to filtered medical air
[20% (95% confidence interval: 1.0%,
38%) and 64% (0.2%, 127%),
respectively] 21 hours post exposure. However exposure to coarse CAP
was significantly associated with decreases in blood cortisol
[-26.0% (-42.4%, -9.6%) and -22.4%
(-43.7%, -1.1%) at 1 hr and 21 hr post exposure,
respectively]. Biological molecules present in coarse CAP were
significantly associated with blood biomarkers indicative of blood brain
barrier integrity. Endotoxin content was significantly associated with
increased blood ubiquitin C-terminal hydrolase L1 [UCHL1, 11
% (5.3%, 16%) per
ln(ng/m3+1)] 1-hour post exposure, while
β-1,3-D-glucan was significantly associated with increased blood
S100B [6.3% (3.2%, 9.4%) per
ln(ng/m3+1)], as well as UCHL1
[3.1% (0.4%, 5.9%) per
ln(ng/m3+1)], one-hour post exposure. Fine CAP
was marginally associated with increased blood UCHL1 when compared with
exposure to filtered medical air [17.7% (-1.7%,
37.2%), p=0.07] 21 hours post exposure. Ultrafine
CAP was not significantly associated with changes in any blood and urinary
neural biomarkers examined.
Conclusion
Ambient coarse particulate matter and its biological constituents may
influence neural biomarker levels that reflect perturbations of blood-brain
barrier integrity and systemic stress response.