Aerosol AgNPs characterization. Characterization of AgNPs aerosol was performed using a scanning mobility particle sizer (A, D), cascade impactor (B, E), and dynamic light scattering (DLS) (C, F). SMPS peak particle number at 77.4 nm for 20 nm AgNP and (E) 78.2 nm for 110 nm AgNP. Note the shoulder in the 110 nm AgNP trace at 120 nm (D). Mass concentration of size fractions was determined using a Merced type cascade impactor type (B, E). This indicates that there were some agglomerates of particles in the sample. Particle size in suspension was determined by DLS (C, F). Samples from manufacturer sealed containers (circles) and particles recovered from nebulizer at the end of exposure (diamonds) are very similar indicating lack of degradation. SMPS data are geometric mean ± σg (geometric standard deviation), cascade impactor data are mean ± SD, and DLS is Z-average diameter.