On April 27, 2015, the National Institute for Occupational Safety and Health (NIOSH) announced publication of “Carbon Nanotube and Nanofiber Exposure Assessments: An Analysis of 14 Site Visits” in Annals of Occupational Hygiene. The paper is the second report from NIOSH’s Industrywide Study. According to NIOSH, the findings illustrate which tasks have the highest exposures, trends in exposure, nature and character of materials involved, effectiveness of controls when used, and continued refinement of the methods used to evaluate exposure of this high-priority class of nanomaterials. NIOSH visited 14 sites to assess exposures to carbon nanotubes (CNT) (13 sites) and carbon nanofibers (CNF) (one site). According to the abstract, overall, elemental carbon personal breathing zone and area time-weighted average samples were below the NIOSH recommended exposure limit (REL) of one microgram per cubic meter (µg/m3) elemental carbon as a respirable mass (96 percent were less than one µg/m3 at the respirable size fraction), while 30 percent of the inhalable personal breathing zone elemental carbon samples were found to be greater than one µg/m3. The abstract states: “Until more information is known about health effects associated with larger agglomerates, it seems prudent to assess worker exposure to airborne CNT and CNF materials by monitoring [elemental carbon] at both the respirable and inhalable size fractions. Concurrent [transmission electron microscopy] samples should be collected to confirm the presence of CNT and CNF.”
