Late last month the National Institute for Occupational Safety and Health (NIOSH) issued Current Intelligence Bulletin 65 recommending exposure limits for carbon nanotubes (CNTs) and carbon nanofibers (CNFs) based on the concerns over possible adverse health effects.
Citing research studies that demonstrated adverse lung effects on rodents at relatively low-mass doses of CNTs and CNFs, including pulmonary inflammation and rapidly developing fibrosis, NIOSH stated that worker exposure needs to be minimized.
NIOSH proposed a recommended exposure limit (REL) of µg/m3 of elemental carbon as a respirable mass 8-hour time-weighted average. NIOSH noted, however, that because of some residual risk at the REL and uncertainty concerning chronic health effects and possibly carcinogenicity, efforts should be made to reduce exposures as much as possible.
According to NIOSH, recent animal studies suggest that carbon nanotubes and carbon nanofibers may pose a respiratory hazard.
You can find NIOSH’s Current Health Bulletin 65 here.