In this study, airborne particles were collected using filters, and the particle number concentrations were measured in two nanotitanium dioxide (nanoTiO2)-manufacturing plants. Real-time particle size measurements were performed using both optical and scanning mobility particle sizer and X-ray fluorescence spectrometry (XRF). The respirable particles collected using filters were used to analyze Ti concentrations in the workplace air of two factories engaged in nanoTiO2 powder bagging processes. The XRF analysis revealed sufficient sensitivity to measure 0.03 mg/m3, which is 1/10 the concentration of the recommended occupational exposure limit of nanoTiO2 in both stationary sampling and personal exposure sampling settings. In a factory where outside air was directly introduced, micron-sized aggregated particles were generated because of factory operations; however, nanosized and submicron-sized particles were not observed owing to high background concentrations of incidental nanoparticles. Alternatively, in another factory where particles from the outside air were removed using a high-efficiency particulate air filter, workrelated nanoparticles were released. The findings of this study suggest that in nanoparticle powder handling processes, a nanoparticle exposure risk exists in the form of nonagglomerated state in nanoparticle powder handling processes. [ABSTRACT FROM AUTHOR]