Journal of Korean Society of Occupational and Environmental Hygiene (한국산업보건학회지)

Korean Industrial Hygiene Association (한국산업보건학회)
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Characteristics of Workers' Exposure to Aerosolized Particles during the Production of Carbon Nanotube-enabled Composites

탄소나노튜브 복합체 취급 작업자의 공기 중 입자상 물질 노출 특성

  • Kwon, Jiwoon (Occupational Safety and Health Research Institute, Korea Occupational Safety and Health Agency) ;
  • Kim, Sungho (Occupational Safety and Health Research Institute, Korea Occupational Safety and Health Agency) ;
  • Jang, Miyeon (Occupational Safety and Health Research Institute, Korea Occupational Safety and Health Agency)
  • 권지운 (한국산업안전보건공단 산업안전보건연구원) ;
  • 김성호 (한국산업안전보건공단 산업안전보건연구원) ;
  • 장미연 (한국산업안전보건공단 산업안전보건연구원)
  • Received : 2020.02.27
  • Accepted : 2020.03.27
  • Published : 2020.03.31
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Abstract

Objectives: The purpose of this case study is to assess workers' exposure to carbon nanotubes(CNTs) and characterize particles aerosolized during the process of producing CNT-enabled polytetrafuoroethylene(PTFE) composites at a worksite in Korea. Methods: Personal breathing zone and area samples were collected for determining respirable concentrations of elemental carbon(EC) using NIOSH(National Institute for Occupational Safety and Health) Method 5040. Personal exposure to nano-sized particles was measured as the number concentration and mean diameter using personal ultrafine particle monitors. The number concentration by particle size was measured using optical particle sizers(OPS) and scanning mobility particle sizers(SMPS). Transmission electron microscopy (TEM) area samples were collected on TEM grids and analyzed to characterize the size, morphology, and chemistry of the particles. Results: Respirable EC concentrations ranged from 0.04 to 0.24 ㎍/㎥, which were below 23% of the exposure limit recommended by NIOSH and lower than background concentrations. Number concentrations by particle size measured using OPS and SMPS were not noticeably elevated during CNT-PTFE composite work. Instant increase of number concentrations of nano-sized particles was observed during manual sanding of CNT-PTFE composites. Both number concentrations and mean diameters did not show a statistically significant difference between workers handing CNT-added and not-added materials. TEM analyses revealed the emission of free-standing CNTs and CNT-PTFE aggregate particles from the powder supply task and composite particles embedded with CNTs from the computer numerical control(CNC) machining task with more than tens of micrometers in diameter. No free-standing CNT particles were observed from the CNC machining task. Conclusions: Significant worker exposure to respirable CNTs was not found, but the aerosolization of CNTs and CNT-embedded composite particles were observed during handing of CNT-PTFE powders and CNC machining of CNT-PTFE composites. Considering the limited knowledge on the toxicity of CNTs and CNT composite particles to date, it seems prudent to take a precautionary approach for the protection of workers' health.

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