The different VNAs vary in their carcinogenic potency. NDMA,
NPYR and NPIP all affected the same endpoint, i.e. total liver tumors
but with descending potency, with NDMA being the most potent
of the three (Peto et al., 1984). In the present study the BMDL10 of
29 μg kg bw−1 day−1 was conservatively chosen for the combined risk
assessment for the total of VNA. Except for NDEA the VNAs are less
potent carcinogens than NDMA. NSAR is a carcinogenic NVNA (IARC,
1978), though a much weaker one than NDMA. For a conservative
approach we therefore found it relevant to include NSAR in the
summed exposure to carcinogenic NA and thereby include it in the
risk assessment.