This report documents the re-evaluation of Hanford Tank Farm (HTF) occupational exposure limits (OEL) for five N-nitrosamines identified as Chemicals of Potential Concern (COPC), and two other N-nitrosamines being considered as COPCs. N-nitrosamines are genotoxic, and exposure has been historically regulated based on cancer as the endpoint of concern. Currently, HTFOELs are based on German Maximum Arbeitsplatz Konzentration values that are no longer used. The National Institute of Occupational Safety and Health (NIOSH) recently released new policy applying a risk-based approach
to develop OELs for occupational carcinogens and plans to release guidance on specific chemicals in the future. Consistent with this new NIOSH policy, Pacific Northwest National Laboratory proposes a risk-based approach to establish risk-specific doses for occupational exposures to N-nitrosamine COPCs. This approach establishes a range of N-nitrosamine inhalation exposures associated with risk levels that can be used as a tool for protecting HTF workers. Updated guidance from NIOSH or other authoritative bodies on N-nitrosamine OELs should trigger a re-evaluation of this proposed approach.