On January 5, 2021, the National Institute for Occupational Safety and Health (NIOSH) posted a Science Blog item entitled “Understanding the Broad Class of Carbon Nanotubes and Nanofibers (CNT/F) Used or Produced in U.S. Facilities.” The item summarizes a recently published article in the journal Particle and Fibre Toxicology, “Physicochemical characterization and genotoxicity of the broad class of carbon nanotubes and nanofibers used or produced in U.S. facilities” that addresses whether different-sized CNT/F materials have similar toxicity if inhaled. For successful commercialization and industrial hygiene, and from a human health perspective, it is important for us to understand the relationship between different physicochemical characteristics of CNT/F and toxicological effects. The Science Blog item states that the major findings of the study include:
- Not all CNT/F possess similar toxicity. This will be further illustrated in subsequent publications that evaluate inflammation, pathological changes, and translocation;
- Detailed physical dimension characteristics, not just the mean length and width, provide a more consistent grouping of CNT/F into toxicologically relevant categories;
- All CNT/F induced some degree of genotoxicity. Micronuclei formation, combined with cellular oxidative stress and evidence of DNA double-strand breaks, indicated CNT/F with increasing length and diameter caused slightly more toxicity; and
- Interestingly, even a small percentage of CNT/F with increased length and diameter in a material can alter the toxicity of the material. It does not need to be the primary component of the material.
According to the Science Blog item, depending on the parameter, the toxicity of CNT/F is likely to vary by the component material or group of materials with similar physicochemical characteristics. NIOSH states that integrating exposure and toxicity assessments provides direct feedback and representative study design, enabling an understanding of the potential for toxicity of a CNT/F in relationship to potential worker or consumer exposure. NIOSH expects these results to help inform guidance for the responsible handling and commercialization of CNT/F.