Acute health effects of ambient air pollution including ultrafine particles in a semi-experimental setting in young, healthy individuals.

Background: Multiple effects of ultrafine particles (UFP) on human subjects are known but there is less knowledge of how relative exposure levels between ultrafine and fine particles as typically encountered in large cities affect lung function and cardiovascular parameters.

Methods: Four sites with high/low levels of ultrafine particles and/or fine particles were selected in the city of Munich, Germany: control area (woodland), urban environment, heavy traffic site, biomass combustion (beech wood). In a randomized cross-over design, 26 young, healthy individuals were exposed at each site over 75 min to atmospheric pollutants, which were monitored continuously, while performing intermittent (5 min per 15 min) light exercise. Parameters assessed pre and post exposure comprised symptoms, spirometry, lung diffusing capacity for carbon monoxide (DLCO) and nitric oxide (DLNO), alveolar volume (AV), the fractional concentration of exhaled nitric oxide (FeNO), reactive hyperemia index (RHI), blood pressure, and heart rate. Outcomes were expressed as percent changes of parameters and analyses performed by either comparing the four sites or by multiple linear regression analyses using the measured pollutant levels.

Results: The sites showed the planned pattern of exposure levels but with large overlap. Outcomes showed no statistically significant differences between sites, except for symptoms which were elevated with heavy traffic site exposure and biomass combustion. In regression analyses, AV decreased by 0.92 (95% confidence interval (CI): 0.28 to 1.57) % per 10,000/cm³ UFP; similarly, for LDSA (lung-deposited surface area), which was highly correlated with UFP. Overall, FeNO slightly increased after exposure, but this increase was attenuated by 5.4 (95% CI: 1.8 to 9.2) % per 10 ppb ambient NO₂. Heart rate decreased after exposures overall; this decrease was enhanced by 2.1 (95% CI: 0.3 to 4.0) % per 10,000/cm³ UFP.

Conclusions: Short-term exposures to UFP elicited a reduction in the lung volume (AV) accessible to gas transport by diffusion and convection. FeNO was slightly elevated after all exposures, but this increase was significantly smaller at higher ambient NO₂ concentrations. While these effects were too small to be clinically relevant, they demonstrated that typical levels of urban air pollution had measurable acute effects in young, healthy individuals.