Current Intelligence Bulletin 65: Occupational Exposure to Carbon Nanotubes and Nanofibers

This NIOSH Current Intelligence Bulletins, (1) reviews the animal and other toxicological data relevant to assessing the potential non-malignant adverse respiratory effects of carbon nanotubes (CNT) and carbon nanofibers (CNF), (2) provides a quantitative risk assessment based on animal dose-response data, (3) proposes a recommended exposure limit (REL) of 1 μg/m³ elemental carbon as a respirable mass 8-hour time-weighted average (TWA) concentration, and (4) describes strategies for controlling workplace exposures and implementing a medical surveillance program. The NIOSH REL is expected to reduce the risk for pulmonary inflammation and fibrosis. However, because of some residual risk at the REL and uncertainty concerning chronic health effects, including whether some types of CNTs may be carcinogenic, continued efforts should be made to reduce exposures as much as possible.