Most of TiO 2 powder was suspended as micron-order agglomerates in the breathing zone. The operation of a gasoline powered forklift temporarily increased the concentration of ultrafine particles. The maximum PM 0.1 concentration (31.3 µg m –3) occurred in a powder filling booth without air ventilation. More than 70% of particles in the breathing zone was coarse agglomerates of > 1 µm, while it may be influenced by powder properties and the handling process as well as the management of local ventilation. The action level was exceeded during the filling of a flexible container bag. The 8h-time-weighted average (TWA) and 95% upper limit for respirable dust exposure were below the occupational exposure limit specified by the Japan Society for Occupational Health and the recommended exposure limits for TWA by NIOSH. The number of particles of 0.01–10 µm was also monitored online in order to examine the short-term fluctuation in the concentration and size distribution of particles. Using a cyclone sampler for PM 4 and a personal sampler for PM 0.1, PM 4 and PM 0.1 exposure levels were evaluated to discuss them in relation to worker’s duties.
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