Industrial worker exposure to airborne particles during the packing of pigment and nanoscale titanium dioxide.

CONTEXT: Titanium dioxide (TiO2) factory workers' source specific exposure and dose to airborne particles was studied extensively for particles between 5 nm and 10 µm in size. OBJECTIVE: We defined TiO2 industry workers' quantitative inhalation exposure levels during the packing of pigment TiO2 (pTiO2) and nanoscale TiO2 (nTiO2) material from concentrations measured at work area. METHODS: Particle emissions from different work events were identified by linking work activity with the measured number size distributions and mass concentrations of particles. A lung deposit model was used to calculate regional inhalation dose rates in units of particles min⁻¹ and µg min⁻¹ without use of respirators. RESULTS: Workers' average exposure varied from 225 to 700 µg m⁻³ and from 1.15 × 104 to 20.1 × 104 cm⁻4. Over 90% of the particles were smaller than 100 nm. These were mainly soot and particles formed from process chemicals. Mass concentration originated primarily from the packing of pTiO2 and nTiO2 agglomerates. The nTiO2 exposure resulted in a calculated dose rate of 3.6 × 106 min⁻¹ and 32 µg min⁻¹ where 70% of the particles and 85% of the mass was deposited in head airways. CONCLUSIONS: The recommended TiO2 exposure limits in mass by NIOSH and in particle number by IFA were not exceeded. We recommend source-specific exposure assessment in order to evaluate the workers' risks. In nTiO2 packing, mass concentration best describes the workers' exposure to nTiO2 agglomerates. Minute dose rates enable the simulation of workers' risks in different exposure scenarios.