NIOSH Develops Draft REL for Silver Nanomaterials
NIOSH has revised its draft Current Intelligence Bulletin on the health effects of occupational exposure to silver nanomaterials, which are used in the manufacture of electronics and textiles and have been used as pigments, catalysts, and antimicrobials. The revised draft document updates the previous version that was published in 2016. The revision contains an updated scientific literature review of information related to occupational exposure to silver nanomaterials and proposes a new draft recommended exposure limit that would apply to processes that produce or use silver nanomaterials. NIOSH now recommends that worker exposures to silver nanomaterials not exceed 0.9 µg/m3 measured as an airborne respirable 8-hour time-weighted average concentration. The agency continues to recommend its existing REL for total silver of 10 µg/m3 as an 8-hour time-weighted average concentration (total mass sample) of silver metal dust, fumes, and soluble compounds. NIOSH’s existing REL is the same as OSHA’s permissible exposure limit for silver. “The PEL and REL 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,” NIOSH’s draft document reads. “However, the [existing] REL has not been evaluated specifically for silver nanomaterials.” The new draft REL is based on NIOSH’s assessment of studies on the toxicological effects of exposure to silver nanomaterials in experimental animal and cellular systems and the effect of particle size and other properties on the toxicological effects of silver. The agency reviewed studies in animals that show adverse lung and liver effects associated with exposure to silver nanoparticles. NIOSH’s draft REL also accounts for the agency’s recommendations on the measurement and control of occupational exposures to silver and silver nanomaterials. The agency recommends the use of workplace exposure assessments, engineering controls, safe work procedures, training and education, and established medical surveillance approaches to prevent potential adverse health effects from exposure to silver nanomaterials. NIOSH’s revised CIB is available via, the federal e-rulemaking portal. For more information, see the Federal Register notice.