After evaluating the available scientific evidence, the National Institute for Occupational Safety and Health (NIOSH) has determined that it is insufficient to support developing a size-specific recommended exposure limit (REL) for silver nanomaterials. In the absence of information to support a size-specific REL, worker exposures to silver dust, fume, and soluble compounds should be maintained below the NIOSH REL of 10 µg/m3 as an 8-hour time-weighted average.
Growing numbers of workers may be exposed
Engineered nanoparticles have unique size-driven properties that can affect their physical, chemical, and biological behavior. Because of the physical-chemical properties at the nanoscale, silver nanomaterials are being used in an increasing number of products. These products include consumer goods, such as electronics and textile coatings, and antibacterial items for medical use. With increased use, however, comes the possibility that growing numbers of workers may be exposed during the manufacture and use of the materials. In keeping with our leadership role in evaluating and assessing whether workers exposed to nanomaterials are at risk, the National Institute for Occupational Safety and Health (NIOSH) recently evaluated the available literature on silver and nanosilver to determine if there is sufficient evidence for a size-specific recommended exposure limit (REL).
Airborne concentrations can exceed limits
Published information on workers’ exposure to silver is limited but indicates that workplace airborne concentrations can exceed recommended limits without good risk management practices, such as using engineering controls. These limits include the current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) and the NIOSH REL of 10 µg/m3. Long-term exposures have been noted to cause localized and generalized argyria, which is an irreversible bluish-gray pigmentation of the skin. NIOSH also evaluated laboratory studies that demonstrated possible lung and liver effects, but these were of uncertain clinical significance when extrapolating study doses to humans.
The draft recommendations now are available for public comments until April 22, 2016. After the public comment period, NIOSH will revise the document in response to the public and peer review comments received before publishing the final recommendations.
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