On February 10, 2016, the National Institute for Occupational Safety and Health (NIOSH) published a Federal Register notice extending the comment period on the draft NIOSH Current Intelligence Bulletin:  Health Effects of Occupational Exposure to Silver Nanomaterials.  As reported in our January 22, 2016, blog item, the draft Current Intelligence Bulletin (CIB) includes 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.  NIOSH recommends that effective risk management control practices be implemented so that worker exposures to silver nanomaterials do not exceed the NIOSH recommended exposure limit (REL) of ten micrograms per cubic meter (μg/m3) (eight-hour time-weighted average) for silver metal dust, fume, and soluble compounds, measured as a total airborne mass concentration.  The draft CIB provides recommendations for the safe handling of silver nanoparticles, and proposes research needs to fill important data gaps in the current scientific literature on the potential adverse health effects of occupational exposure to silver nanoparticles.  Comments are due April 22, 2016.