NIOSH Recommends New Level of Exposure for Nanomaterials

Contact: Nura Sadeghpour (202) 245-0673

NIOSH today recommended that occupational exposures to carbon nanotubes (CNTs) and carbon nanofibers (CNFs) be controlled to reduce a potential risk of certain work-related lung effects. CNTs and CNFs are man-made elongated particles made of sheets of pure carbon that are about a thousand times smaller than a human hair.

NIOSH's recommendations, which were issued in a technical document called a Current Intelligence Bulletin, are based on peer-reviewed findings from NIOSH laboratory studies, field observations of industrial processes, intensive review of published studies by other research authorities, and public review and comment on an earlier draft of the document. Some companies already use or plan to establish control measures that achieve the recommended exposure limit and match a number of NIOSH's recommendations.

CNTs and CNFs are only two of many types of nanomaterials created through nanotechnology which is described as the manipulation of matter on a microscopic scale. This matter is smaller than what has been studied for the past 100 years by material scientists and is far too small to be seen with the human eye; their size gives them new and different properties that have not been seen by scientists before. CNTs and CNFs are being incorporated into different products to increase strength, durability, versatility, heat resistance, and other useful properties. These products include plastics and ceramics, paints and coatings, textiles, and electronics. Though it cannot be determined with certainty how many workers are currently potentially exposed to these nanomaterials, demand for carbon nanotubes and carbon nanofibers is expected to grow over the next decade with increasing use in medical devices, structural materials, consumer goods, and energy-saving products.

Recent results from experimental animal studies with rodents indicate that exposure to CNTs and CNFs may pose a respiratory hazard if inhaled. NIOSH's recommendations are expected to assist industry in establishing good risk management practices for controlling occupational exposures to free, unbound CNTs and CNFs during their manufacture and industrial use.

Consumers are unlikely to be exposed to carbon nanotubes or carbon nanofibers in their free, dry powder form. These materials are almost always bound up or incorporated into a final product as a very small percentage of the final formula. It is the free form of CNTs and CNFs that creates the greatest possibility for inhalation exposure and the greatest concern. The workplace is the most likely place for this type of exposure.

"NIOSH's recommendations provide practical guidance for incorporating prudent management of these revolutionary materials into everyday workplace practice as this new technology and the improved products it creates grows," said NIOSH Director John Howard, M.D. "This guidance supports the safe development of the industry, which will be a critical part of maintaining U.S. leadership in the global nanotechnology market."

NIOSH recommends that employers in companies that manufacture or use carbon nanotubes or carbon nanofibers:

• Reduce worker exposures to airborne concentrations of those materials to no more than 1 microgram per cubic meter of air as a recommended exposure limit. This is the lowest airborne concentration that can be accurately measured. The recommended exposure limit is intended to minimize potential risk for adverse lung effects in workers who might be exposed at this concentration over a working lifetime.
• Apply strategic approaches for controlling occupational exposures, giving priority to engineering controls that enclose processes where CNTs or CNFs could be released into the air, such as transfer of the dry, fine powders from one container to another.
• Educate and train workers on the safe handling of bulk quantities of CNTs and CNFs or CNT-and CNF- enabled products.
• Train workers on the proper use of engineering controls, administrative controls, and safe work practices. These are standard risk management practices that employers have followed for many decades to reduce worker exposures to dusts and other materials in workplaces.
• Establish health surveillance and medical screening programs to help identify early signs of respiratory disease. Such surveillance programs can assist in determining if additional exposure control measures are needed, and if individual medical attention is needed.

NIOSH and diverse partners in the private sector and government have collaborated for approximately 10 years in conducting research and issuing guidance on the safe handling of nanomaterials. Research continues to better understand the potential health risk to workers exposed to CNTs and CNFs and other nanomaterials so that appropriate guidance can be provided for protecting worker’s health. Current Intelligence Bulletin 65: Occupational Exposure to Carbon Nanotubes and Nanofibers is available at http://www.cdc.gov/niosh/docs/2013-145/. For more information about NIOSH’s research and outreach in the nanotechnology industry, visit the topic page at www.cdc.gov/niosh/topics/nanotech/.