Comparison of nanoparticle exposure levels based on facility type—small-scale laboratories, large-scale manufacturing workplaces, and unintended nanoparticle-emitting workplaces

The aims of this study were to investigate the concentrations and characteristics of nanoparticle exposure at various workplaces. We compared the concentration and characteristics of nanoparticles at nine workplaces of three types; i.e., small laboratories (LAB), large-scale engineered nanoparticle manufacturing workplaces (ENP), and unintended nanoparticle-emitting workplaces (UNP), using real-time monitoring devices including scanning mobility particle sizers (SMPS), condensation particle counters (CPC), surface area monitors (SAM), and gravimetric sampling. ANOVA and Scheffe's post hoc tests were performed to compare the concentration based on the type of workplace. The concentrations at UNPs were higher than those at other types of workplace for all measured metrics followed by (in order) ENP manufacturing workplaces and LAB (p < 0.01). Geometric means and geometric standard deviations of LAB, ENP, and UNP for total number concentration measured using SMPS were 8,458 (1.41), 19,612 (2.18), and 84,172 (2.80) particles cm(-3), respectively. For CPC, the concentrations were 6,143 (1.45), 11,955 (2.42), and 38,886 (2.61) particles cm(-3), respectively. The surface area concentrations were 32.79 (1.46), 93.68 (2.60), and 358.41 (2.74) mu m(2) cm(-3), respectively. The characteristics of exposure and size distributions differed among the workplaces. Some tasks or processes at LAB exhibited higher concentrations than those at ENP or UNP workplaces, and LAB showed the lowest concentration. In conclusion, we observed different exposure characteristics at LAB, ENP, and UNP suggesting that different risk management strategies are required.