Hi, @hgajjar.
I think the discussion on N-nitroso-propanolol is helpful to you.
In this thread, the link to an interesting paper was shared by @Diego_HM.
Practical and Science-Based Strategy for Establishing Acceptable Intakes for Drug Product N-Nitrosamine Impurities | Chemical Research in Toxicology (acs.org)
Structural group 5 suggests 440ng/day. However, I am not sure this is acceptable to health authorities.