Focused actions to protect carbon nanotube workers

The critical question is that while the carcinogenic potential of carbon nanotubes is being further investigated, what steps should be taken to protect workers who face exposure to CNTs, current and future, if CNTs are found to be carcinogenic? This paper addresses five areas to help focus action to protect workers: review of the current evidence on the carcinogenic potential of CNTs; role of physical and chemical properties related to cancer development; CNT doses associated with genotoxicity in vitro and in vivo; workplace exposures to CNT; and specific risk management actions needed to protect workers

Paul A. Schulte; Eileen D. Kuempel; Ralph D. Zumwalde; Charles L. Geraci; Mary K. Schubauer-Berigan; Vincent Castranova; Laura Hodson; Vladimir Murashov; Matthew M. Dahm; Michael Ellenbecker

2012

Scholarcy highlights

  • If some carbon nanotubes are shown to be carcinogenic, as the current limited experimental animal and in vitro data seem to suggest, are Disclaimer: The findings and conclusions in this paper are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health
  • Assuming a worker is exposed at the NIOSH draft recommended exposure limit for CNTs or carbon nanofibers of 7 mg/m3; breathes 9.6 m3 air per 8-hr workday; and works 250 day/year, it would take approximately 8 years to reach the human-equivalent estimated deposited lung dose that was associated with K-ras mutations in mice
  • multi-wall carbon nanotube dimensions in a workplace; and an example of a structure size that would result in an equivalent number concentration of 0.1 fiber/cm3 and mass concentration of 7 mg/m3
  • NIOSH issued a draft REL for CNTs and CNFs based on the estimated risk of noncancer adverse lung effects for working lifetime exposure at the upper limit of quantification of the NIOSH sampling and analytical method for elemental carbon
  • If significant exposures and risks are suspected, what should be done? Should certain types of CNTs be banned or restricted like many asbestos-containing products are in some countries, or could controls be put in place to protect workers so that society could obtain the benefits of CNTs? Clearly this is a complex issue because there are many types of single-wall carbon nanotube and MWCNTs, and functionalized variants
  • This commentary concerns the possible carcinogenicity of CNTs, it is not clear that cancer is necessarily the most sensitive or significant health endpoint of CNT exposures
  • Based on evaluation of the animal data of pulmonary inflammation and fibrosis following exposure to carbon nanotubes, NIOSH estimated a >10% estimated risk over a working lifetime of early-stage fibrotic lung effects in workers at mass concentrations below the limit of quantification of the current measurement method

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