e.g. N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR),N-nitrosopiperidine (NPIP) and N-nitrosodiethylamine (NDEA), occursgenerally at low levels <5 μg kg−1 but levels up to 20 μg kg−1 has beenreported (Hill et al., 1988; Massey et al., 1991). NDEA has been evaluatedas the most potent carcinogen among the known meat relatedVNAs (Peto et al., 1984). The non-volatile NAs (NVNAs), which includethe N-nitrosamino acids, e.g. N-nitrosohydroxyproline (NHPRO),N-nitrosoproline (NPRO), N-nitrososarcosine (NSAR), N-nitrosothiazolidine-4-carboxylic acid (NTCA), N-nitroso-2-methylthiazolidine-4-carboxylic acid (NMTCA), generally occur atsignificantly higher levels than the VNAs, i.e. up to several thousandmicrogram per kilo (Herrmann et al., 2014a; Massey et al., 1991;Tricker and Kubacki, 1992). With the exception of NHPRO and NPROthe carcinogenicity of the NVNAs are poorly elucidated (Tricker et al.,1991). For NTCA and NMTCA a literature study only revealed threein vitro genotoxicity studies of limited scope (Lin and Gruenwedel,1990; Negishi et al., 1991; Umano et al., 1984) for NTCA and nostudies for NMTCA. Thus, the toxicological significance of severalof the NVNAs cannot be evaluated because of insufficient data.Estimations of the dietary exposure to NAs are available in theliterature though only for the VNA, NDMA, NPYR and in a few casesNPIP. Studies on the dietary exposure to NDMA published from1978to 1990 have been reviewed by Tricker et al., (1991) (Table 1). Sincethen others have published results on dietary exposure to NDMA,NPYR and NPIP (Table 1). The estimated exposures to VNA from allfoods range from 80 ng day−1 (NDMA only) for the Finish population(1990), to 900 ng day−1 (NDMA, NPYR, NPIP) for the German
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