The National Institute for Occupational Safety and Health (NIOSH) has set exposure guidelines (current intelligence bulletin [CIB 65]) for nanotechnology fibers at “one microgram per cubic meter of air per eight-hour workday.” According to environmental health sciences experts, anything below that limit cannot be measured. While the CIB acknowledges that animal studies may not indicate “whether similar adverse health effects occur in humans following exposure to CNT [carbon nanotubes] or CNF [carbon nanofibers], or how airborne CNT in the workplace may compare in size and structure to the CNT aerosols generated in the animal studies,” because adverse respiratory health effects have been observed in lab animals, NIOSH recommended an exposure limit for CNT and CNF “to help minimize the risk of occupational respiratory disease in workers.” See USA Today, April 26, 2013.