Method validation of nanoparticle tracking analysis to measure pulmonary nanoparticle content : the size distribution in exhaled breath condensate depends on occupational exposure.

Abstract

Aparticle exposure assessment based on the dose deposited in the lungs would be the gold standard for the evaluation of any resulting health effects. Measuring particles in exhaled breath condensate (EBC)—a matrix containing water and airway lining fluid—could help to evaluate particle retention in the lungs. This study aimed to (1) validate a nanoparticle tracking analysis (NTA) method for determining the particle number concentration and their hydrodynamic size distribution in EBC, and (2) apply this method to EBC collected from workers exposed to soapstone (n=55) or quartz dust (n=12) and controls (n=11). A standard latex bead solution was used to determine the linear range, limit of detection (LOD), repeatability (coefficient of variation,CV), and bias in spiked EBC. An LM10 NanoSight instrument withNTAversion 3.1 software was used for measurement. RTubes® were used for field collection of EBC. The repeatability obtained for aD50 size distribution in EBC showed less than8%variability, with a bias<7%. The particle concentration was linear in the range 2.5×108 particles ml−1 with aLODof 4×106 particles ml−1. A recovery of 117±20% at 6.2×107 particles ml−1 was obtained with aCV<10% and a bias<20%. EBC from workers exposed to quartz, who experienced the largest exposure to silica particles, consistently exhibited a statistically significant (p<0.01) higher concentration of particles in their EBC, with a size distribution shift towards larger values than the other groups. Results showed that theNTAtechnique performed well for characterizing the size distribution and concentrations of particles in EBC. The technique needs to be corroborated with a larger population of workers.