On the heels of new research showing that nano particles may cause lung damage, the National Institute for Occupational Safety and Health is taking no chances and has issued a recommended exposure limit (REL) for nanotubes and nanofibers. The REL for carbon nanotubes and nanofibers is not a legal requirement, but the fact that it has been issued (along with the supporting evidence NIOSH used in making its recommendation) gives employees ammunition to claim that employers have been put on notice about the potential hazards.

What's the REL?

NIOSH set the REL for carbon nanotubes and nanofibers to the lowest detectible level (1 microgram per cubic meter) as a respirable mass 8-hour time-weighted average concentration.  Occupational exposure to carbon nanotubes and carbon nanofibers can occur not only in the process of manufacturing them, but also when these materials are incorporated into other products or applications.

In view of the NIOSH REL, it would appear that OSHA's permissible exposure limits (PELs) for graphite (5,000 micrograms per cubic meter) and carbon black (3,500 micrograms per cubic meter) can no longer be applied to carbon nano materials. The new REL is dramatically lower than the previous standards and will be much more difficult to achieve.

What's behind the new recommendation?

The NIOSH REL is based on a number of research studies with rodents that have shown adverse lung effects such as pulmonary inflammation and rapidly developing, persistent fibrosis at relatively low-mass doses of carbon nanotubes and nanofibers.  The REL also reflects NIOSH's March, 2013  report, which described preliminary findings from a new laboratory study in which mice were exposed by inhalation to multi-walled carbon nanotubes.  Although the study did not indicate that the nano substances alone caused cancer in mice, the findings did indicate that when mice received both an initiator chemical plus inhalation exposure to the nano materials, they were significantly more likely to develop tumors (90 percent incidence) and have more tumors than mice receiving the initiator chemical alone.

Is my company at risk?

As NIOSH notes, nano materials are currently found "in hundreds of products, ranging from cosmetics to clothing to industrial and biomedical applications."  NIOSH notes that "many of these first-generation products of nanotechnology," which include metal oxides, nanotubes, nanowires, quantum dots, and carbon fullerenes (bucky balls), among others, "may pose a greater health risk than the larger bulk form of these materials."  Accordingly, employers must carefully monitor current research in this rapidly evolving area.