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NTP Publishes Technical Report on Toxicity Studies of 1020 Long Multiwalled Carbon Nanotubes

On December 5, 2019, the National Toxicology Program (NTP) announced that the NTP Technical Report on the Toxicity Studies of 1020 Long Multiwalled Carbon Nanotubes Administered by Inhalation to Sprague Dawley (Hsd:Sprague Dawley® SD®) Rats and B6C3F1/N Mice is now available.  In 2003, the Rice University Center for Biological and Environmental Nanotechnology nominated nanoscale materials as a class of substances for toxicological evaluation.  The recommended studies included “[c]haracteriz[ing] the inhalation toxicology of high aspect ratio materials, such as carbon nanotubes (single-walled or multi-walled), as a function of material purity and stabilization.”  According to the abstract for the Technical Report, “[b]ecause long-term inhalation toxicity and carcinogenicity studies were being conducted on a relatively short, rigid [multiwalled carbon nanotube (MWCNT)], a representative long and thin MWCNT was selected for these studies.”  Following an evaluation of 24 different long, thin MWCNTs, NTP selected the 1020 Long Multiwalled Carbon Nanotube (L-MWNT-1020) (Sun Innovations, Fremont, CA) “based on availability, high purity (97%), and the low amount of residual nickel catalyst (0.52% by weight).”  The abstract states that 0.3 milligrams per cubic meter (mg/m3) is considered the no‑observed‑adverse‑effect level (NOAEL) for L-MWNT-1020.  The Technical Report notes that the exposure concentrations used in the study were approximately 100-fold higher than the National Institute for Occupational Safety and Health (NIOSH)-proposed recommended exposure limit (REL) for carbon nanotubes (CNT) of 1.0 micrograms per cubic meter (μg/m3) elemental carbon as a respirable mass eight-hour time-weighted average (TWA) concentration.  According to the Technical Report, “NIOSH researchers have also evaluated exposure in multiple U.S. manufacturers of CNTs and nanofibers and reported inhalable exposures of MWCNT of up to 0.4 mg/m3.”  The Technical Report states that given the long half-life and persistence of MWCNT in the lung, “even short periods of exposure at such levels would lead to chronic high-level exposures.  Therefore, although the no-observed-adverse-effect level determined in the present study (0.3 mg/m3) is approximately 300-fold higher than the recommended exposure limit, it is within the range observed in occupational settings and may be informative regarding potential health risks associated with occupational exposures to CNTs.”  The abstract includes a detailed chart summarizing the findings considered to be toxicologically relevant in rats and mice exposed to L-MWNT-1020 by inhalation for 30 days.

©2020 Bergeson & Campbell, P.C.National Law Review, Volume IX, Number 341

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About this Author

Lynn Bergeson, Campbell PC, Toxic Substances Control Act Attorney, federal insecticide lawyer, industrial biotechnology legal counsel, Food Drug Administration law
Managing Partner

Lynn L. Bergeson has earned an international reputation for her deep and expansive understanding of the Toxic Substances Control Act (TSCA), the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), European Union Registration, Evaluation, Authorization and Restriction of Chemicals (REACH), and especially how these regulatory programs pertain to nanotechnology, industrial biotechnology, synthetic biology, and other emerging transformative technologies. Her knowledge of and involvement in the policy process allows her to develop client-focused strategies whether...

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Carla Hutton, Bergeson Campbell PC, global regulatory attorney, public health activists lawyer, metals industry legal counsel, Toxic Substances Control Act law
Regulatory Analyst

Since 1996, Carla Hutton has monitored, researched, and written about regulatory and legislative issues that may potentially affect Bergeson & Campbell, P.C. (B&C®) clients. She is responsible for creating a number of monthly and quarterly regulatory updates for B&C's clients, as well as other documents, such as chemical-specific global assessments of regulatory developments and trends. She authors memoranda for B&C clients on regulatory and legislative developments, providing information that is focused, timely and applicable to client initiatives. These tasks have proven invaluable to many clients, keeping them aware and abreast of developing issues so that they can respond in kind and prepare for the future of their business.

Ms. Hutton brings a wealth of experience and judgment to her work in federal, state, and international chemical regulatory and legislative issues, including green chemistry, nanotechnology, the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), the Toxic Substances Control Act (TSCA), Proposition 65, and the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) program.

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