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NIOSH Issues Draft Current Intelligence Bulletin on Health Effects of Occupational Exposure to Silver Nanomaterials

Release Date: February 17, 2016

Engineered silver (Ag) nanomaterials are used in a growing number of consumer and medical products. As a result, the National Institute for Occupational Safety and Health (NIOSH) assessed the scientific literature to investigate whether workers exposed to silver nanomaterials are at increased risk of adverse health effects. One of the key objectives was to determine whether sufficient data are available to develop a recommended exposure limit (REL) that is specific to particle size.

Results of the NIOSH assessment are contained in a draft document entitled External Review Draft - NIOSH Current Intelligence Bulletin: Health Effects of Occupational Exposure to Silver Nanomaterials (CIB). The document is available for public review and comment until April 22, 2016, and a public meeting to solicit additional comment and information will be held on March 23, 2016 at the NIOSH/CDC Robert A. Taft Laboratories in Cincinnati, Ohio.

The draft CIB contains a review and assessment of the currently available scientific literature on the toxicological effects of exposure to silver nanoparticles in experimental animal and cellular systems, and on the occupational exposures to silver dust and fume and the associated health effects. The current NIOSH recommended exposure limit (REL) for silver (metal dust and soluble compounds, as Ag) is ten micrograms per cubic meter (ug/m3), which is the same as the OSHA permissible exposure limit (PEL). The REL and PEL are based on preventing workers from developing argyria, which is bluish-gray pigmentation to the skin and mucous membranes, and argyrosis, which is bluish-gray pigmentation to the eyes – the limits are not based on the size of the silver nanoparticles, and do not directly address any adverse effects that may be associated with silver nanoparticles. As a result, one of the key objectives of the CIB was to assess the scientific evidence on the role of silver particle size and toxicity, in order to evaluate whether the current REL for silver is adequate to protect against exposure to silver nanoparticles.

NIOSH attempted to estimate a REL for silver nanoparticles based on data obtained from animal studies. However, the NIOSH estimates for a silver nanoparticle REL were both above and below the current REL, due to a number of uncertainties in evaluating the data. As such, NIOSH concluded:

“Although the experimental animal and cellular studies are useful for showing potential risks from exposure to silver nanomaterials, NIOSH considers the currently available data to be too limited to develop a REL for silver that is specific to particle size.”

As a result, NIOSH is recommending that the current REL of 10 ug/m3 as an 8-hour time-weighted average (TWA) be used to control worker exposure to all forms of silver, including silver nanoparticles. In addition, NIOSH is recommending the implementation of a risk management program, which should include:

The draft NIOSH Current Intelligence Bulletin: Health Effects of Occupational Exposure to Silver Nanomaterials which contains detailed recommendations, such as a table of recommended engineering controls for specific tasks or operations, can be accessed directly at http://www.cdc.gov/niosh/docket/review/docket260a/pdfs/draft--niosh-cib-on-silver-nanomaterials-1_8_16.pdf. For additional information on the public meeting and how to comment on the draft, see the following Federal Register notices:

For additional information on working with nanomaterials, see Engineering & Safety Service News Report NR-2013-11-15, NIOSH Issues New Document on Controlling Industrial Exposures to Nanomaterials, which includes numerous references to several other E&S reports on the subject.

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The information contained in this publication was obtained from sources believed to be reliable. ISO Services, Inc., its companies and employees make no guarantee of results and assume no liability in connection with either the information herein contained or the safety suggestions herein made. Moreover, it cannot be assumed that every acceptable safety procedure is contained herein or that abnormal or unusual circumstances may not warrant or require further or additional procedure.


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