Exposure assessment of workplaces manufacturing nanosized TiO₂ and silver

Abstract

With the increased production and widespread use of nanomaterials, human and environmental exposure to nanomaterials is inevitably increasing. Therefore, this study monitored the possible exposure to nanoparticles at workplaces that manufacture nano-TiO₂ and nano-silver. To estimate the potential exposure of workers, personal sampling, area monitoring, and real-time monitoring using a scanning mobility particle sizer (SMPS) and dust monitor were conducted at workplaces where the workers handle nanomaterials. The gravimetric concentrations of TiO₂ ranged from 0.10 to 4.99 mg/m³, which were lower than the occupational exposure limit 10 mg/m³ set by the Korean Ministry of Labor or American Conference of Governmental Industrial Hygienists (ACGIH). Meanwhile, the silver metal concentrations ranged from 0.00002 to 0.00118 mg/m³, which were also lower than the silver dust 0.1 mg/m³ and silver soluble compound 0.01 mg/m³ occupational exposure limits set by the ACGIH. The particle number concentrations at the nano-TiO₂ manufacturing workplaces ranged from 11,418 to 45,889 particles/cm³ with a size range of 15–710.5 nm during the reaction, although the concentration decreased to 14,000 particles/cm³ when the reaction was stopped. The particle concentrations at the TiO₂ manufacturing workplaces increased during the reactor and vacuum pump operations, and during the collection of the synthesized TiO₂ particles. Similarly, the particle concentrations at the silver nanoparticle manufacturing workplaces increased when the sodium citrates were weighed or reacted with the silver nitrates, and during the cleaning of the workplace. The number of silver nanoparticles in the samples obtained from the workplace manufacturing silver nanoparticles using induced coupled plasma ranged from 57,789 to 2,373,309 particles/cm³ inside the reactor with an average size of 20–30 nm and 535–25,022 particles/cm³ with a wide range of particle sizes due to agglomeration or aggregation after the release of nanoparticles into the workplace air. In contrast, the silver nanoparticles manufactured by the wet method ranged from 393 to 3526 particle/cm³ with an average size of 50 nm. Thus, when taken together, the TiO₂ and silver nanoparticle concentrations were relatively lower than existing occupational exposure limits.

Keywords::

• Nano-silver
• nano-TiO2
• workplace
• exposure assessment
• nanoparticle
• nanomaterial

Acknowledgement

This research was supported by the Nano R&D program through the National Research Foundation of Korea funded by the Korean Ministry of Education, Science and Technology (2010-0019156).

Declaration of interest

The authors declare that they have no competing interests.