Exhaled breath condensate as a matrix for combustion-based nanoparticle exposure and health effect evaluation.

Background
Health Assessment and medical surveillance of workers exposed to combustion nanoparticles is challenging. The aim was to evaluate the feasibility of using exhaled breath condensate (EBC) from healthy volunteers for 1) assessing the lung deposited dose of combustion nanoparticles; 2) determining the resulting oxidative stress by measuring H2O2 and MDA.
Methods
15 healthy non smoker volunteers were exposed to three different levels of side-stream cigarette smoke under controlled conditions. EBC was repeatedly collected before, during and 1 and 2 hours post exposure. Exposure variables were measured by direct reading instruments and by active sampling. The different EBC samples were analyzed for particle number concentration (light-scattering based method) and for selected compounds considered oxidative stress markers.
Results
Subjects were exposed to an average airborne concentration up to 4.3 x 10^5 particles/cm3 (average geometric size ~60-80 nm). Up to 10 x 10^8 particles/ml could be measured in the collected EBC with a broad size distribution (50th percentile ~160 nm) but these biological concentrations were not related to the exposure level of cigarette smoke particles. While H2O2 and MDA concentrations in EBC increased during exposure, only H2O2 showed a transient normalization 1 hour after exposure and increased afterward. In contrast, MDA levels stayed elevated during the 2 hours post-exposure.
Conclusions
The use of diffusion light scattering for particle counting proved to be sufficiently sensible to detect objects in EBC but lacked the specificity for carbonaceous tobacco smoke particles. Our results suggest two phases of oxidation markers in EBC: first, the initial deposition of particles and gases in the lung lining liquid, and later the start of oxidative stress with associated cell membrane damage. Future studies should extend the follow-up time and should remove gases or particles from the air to allow differentiating between the different sources of H2O2 and MDA.