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

Abstract

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.

Keywords::

• Aerosol
• nanoparticle
• characterization
• exposure
• dose
• TiO₂