E9-7941. Request for Information on Carbon Nanotubes (CNTs) Including Single-Walled Carbon Nanotubes (SWCNTs) and Multi-Walled Carbon Nanotubes (MWCNTs)

AGENCY:

National Institute for Occupational Safety and Health (NIOSH) of the Centers for Disease Control and Prevention (CDC), Department of Health and Human Services (HHS).

ACTION:

Notice of public comment period.

SUMMARY:

The National Institute for Occupational Safety and Health (NIOSH) of the Centers for Disease Control and Prevention (CDC) intends to evaluate the scientific data on carbon nanotubes (CNTs) and develop appropriate communication documents, such as an Alert and/or Current Intelligence Bulletin, which will convey the potential health risks and recommend measures for the safe handling of these materials. NIOSH has developed guidelines for managing the potential health concerns associated with occupational exposures to engineered nanoparticles [see: http://www.cdc.gov/​niosh/​topics/​nanotech/​safenano/​] which will provide the framework for developing specific recommendations for CNTs.

NIOSH is requesting information on the following: (1) Published and unpublished reports and findings from in vitro and in vivo toxicity studies with CNTs, (2) information on possible health effects observed in workers exposed to CNTs, (3) information on workplaces and products in which CNTs can be found, (4) description of work tasks and scenarios with a potential for exposure, (5) workplace exposure data, and (6) information on control measures (e.g., engineering controls, work practices, personal protective equipment) that are being used in workplaces where potential exposures to CNTs occur.

Public Comment Period: Comments must be received by May 15, 2009.

ADDRESSES:

You may submit comments, identified by docket number NIOSH-161, by any of the following methods:

• Mail: NIOSH Docket Office, Robert A. Taft Laboratories, MS-C34, 4676 Columbia Parkway, Cincinnati, OH 45226.
• Facsimile: [phone].
• E-mail: [e-mail].

All information received in response to this notice will be available for public examination and copying at the NIOSH Docket Office, 4676 Columbia Parkway, Cincinnati, Ohio 45226. A complete electronic docket containing all comments submitted will be available on the NIOSH Web page at http://www.cdc.gov/​niosh/​docket, and comments will be available in writing by request. NIOSH includes all comments received without change in the docket, including any personal information provided.

FOR FURTHER INFORMATION CONTACT:

Ralph D. Zumwalde, NIOSH, Robert A. Taft Laboratories, MS-C32, 4676 Columbia Parkway, Cincinnati, OH 45226, telephone [phone].

SUPPLEMENTARY INFORMATION:

Nanotechnology is generally defined as the intentional manipulation of matter to form novel structures with one or more dimension or features less than 100 nanometers (nm). Nanotechnology involves a wide range of chemistries and almost unlimited types of structures that have highly unpredictable interactions with biological systems. Carbon nanotubes (CNTs) are a type of nanomaterial comprised of a sheet of graphite (a hexagonal lattice of carbon) rolled into a cylinder that can have a length-to-width ratio greater than 1,000. Carbon nanotubes are produced having a single cylinder carbon wall (single-walled carbon nanotubes [SWCNT]) or having multiple walls-cylinders nested within other cylinders (multi-walled carbon nanotubes [MWCNT]). CNTs range in diameter from about 1-2 nanometers for SWCNTs to dozens of nanometers for MWCNTs with lengths extending into the micrometer range.

There are several major techniques used in the synthesis of CNTs. The arc-evaporation technique involves passing a current of about 50 A between two graphite electrodes in an atmosphere of helium in the presence of metal catalysts (Co, Ni). The second method is chemical vapor deposition, where nanotubes are formed by decomposition of a carbon-containing gas with use of nano-sized catalytic particles usually Fe, Co, Yt or Ni. The advantage of catalytic synthesis over arc-evaporation is the ability to scale-up for volume production. The third method for making CNTs, laser ablation, involves employment of a powerful laser to vaporize metal (Co and Ni)-graphite targets. Of the three major processes, chemical vapor deposition is the most prominent one that is currently used for CNT production.

Due to their unique physical and chemical properties, CNTs have sparked much research into developing novel applications. CNTs are ideal non-biodegradable materials; they are stronger then steel, flexible, lightweight, heat resistant, and have high electrical conductivity. The market for CNTs is estimated to grow substantially over the next decade. They are currently used in a variety of applications including: Electronics, reinforced plastics, micro-fabrication conjugated polymer activators, biosensors, enhanced electron/scanning microscopy imaging techniques, and in pharmaceutical/biomedical devices for drug delivery and medical diagnostics. Estimates of the number of workers potentially exposed to CNTs are unavailable due to limited exposure data and its relatively recent introduction into domestic commerce.

The toxic nature of SWCNTs and MWCNTs in humans is not known. Recently published in vitro and in vivo studies with some SWCNTs and MWCNTs describe adverse effects including their ability to be cytotoxic when tested in various cell cultures, and cause acute inflammation and early onset of fibrosis when delivered to the lungs of mice by pharyngeal aspiration or inhalation. No occupational exposure limits for CNTs have been established by NIOSH or the Occupational Safety and Health Administration (OSHA).

NIOSH seeks to obtain materials, including published and unpublished reports and research findings, to evaluate the possible health risks of occupational exposure to CNTs. Examples of requested information include, but not limited to, the following: (1) Identification of industries or occupations in which exposures to CNTs may occur.

(2) Trends in the production and use of CNTs.

(3) Description of work tasks and scenarios with a potential for exposure to CNTs.

(4) Workplace exposure measurement data in various types of industries and jobs.

(5) Case reports or other health information demonstrating potential health effects in workers exposed to CNTs.

(6) Research findings from in vitro and in vivo toxicity studies.

(7) Information on control measures (e.g., engineering controls, work practices, PPE) being taken to minimize worker exposure to CNTs.

Dated: March 31, 2009.

James D. Seligman,

Chief Information Officer, Centers for Disease Control and Prevention.