Introduction Exposed to carbon nanotubes (CNT) may cause potential adverse health effect. Worker may expose to CNT during the manufacturing processes. But there is limited number of studies about CNT exposure at workplaces. The purpose of this study was to conduct exposure assessment of CNT at the CNT manufacturers in lab-scale and large-scale.

Methods Seven sites were investigated at five lab-scale and two large-scale workplaces. Measurement was conducted by tasks. Area and personal samples were collected for mass concentration of EC (Elemental Carbon), according to National Institute for Occupational Safety and Health (NIOSH) Method 5040. Real time monitoring such as Scanning Mobility Particle Sizer etc. Transmission/Scanning electron microscopy (TEM/SEM) samples were collected and analysed to CNT agglomerate and shapes.

Results The three of seven sites exceeded the NIOSH recommended exposure limit (REL) (1 µg/m³). Concentration of EC ranged from 1.21 to 14.24 µg/m³ at large-scale manufacturing and 0.3 to 4.49 µg/m³ at lab-scale handling. Preventive maintenance task showed the highest concentrations and packaging process also higher than other tasks. Relatively high exposure was found during preventive maintenance tasks and packaging by real time monitor. From the electron microscope analysis, we found that the presence of airborne CNT during weighing, sonication, and packing tasks.

Conclusions The number of tasks were exceeded NIOSH REL. At the large scale manufacturing site, the concentration of EC was higher than the NIOSH REL than lab scale site and control of working environment during CNT manufacturing process is required. Therefore, protection of worker should be considered and further exposure assessment study of CNT should be conducted.

Acknowledgement This work was supported by Korea Occupational Safety and Health Agency (2016-OSHRI-1044).