N-Nitrosamine formation

The sudden consumption of the remaining UDMH, and the increased relative importance of N-nitrosamine formation at -30 minutes into the photolysis can be rationalized by assuming that at that time the [NO I/ENO] ratio, and thus the photostationary state [O3], has become sufficiently high that O3 may be reacting with the hydrazine directly, and that reaction (3) begins to dominate over reaction (10). This results in higher rates of UDMH consumption by the OH radicals formed in the UDMH + O3 reaction (1), and by the OH radicals generated by the reaction of NO... 

Nitrite concentration The kinetics of N-nitrosamine formation in vitro has been studied at length (, ) and, in moderately acidic media, the reaction rate is directly proportional to the concentration of the free amine (non-protonated) and to the square of the concentration of the undissociated nitrous acid. Therefore, it is not surprising that the amount of nitrite permitted in bacon has received considerable attention. Although, there have been suggestions that it is the initial and not the residual nitrite that influences N-nitrosamine formation in bacon (41), recent evidence seems to indicate that the lowest residual nitrite gives the least probability of N-nitrosamines... 

Recently, Robach et al. ( ) investigated the effects of various concentrations of sodium nitrite and potassium sorbate on N-nitrosamine formation in commercially prepared bacon. 

N-Nitrosamine inhibitors Ascorbic acid and its derivatives, andDC-tocopherol have been widely studied as inhibitors of the N-nitrosation reactions in bacon (33,48-51). The effect of sodium ascorbate on NPYR formation is variable, complete inhibition is not achieved, and although results indicate lower levels of NPYR in ascorbate-containing bacon, there are examples of increases (52). Recently, it has been concluded (29) that the essential but probably not the only requirement for a potential anti-N-nitrosamine agent in bacon are its (a) ability to trap NO radicals, (b) lipophilicity, (c) non-steam volatility and (d) heat stability up to 174 C (maximum frying temperature). These appear important requirements since the precursors of NPYR have been associated with bacon adipose tissue (15). Consequently, ascorbyl paImitate has been found to be more effective than sodium ascorbate in reducing N-nitrosamine formation (33), while long chain acetals of ascorbic acid, when used at the 500 and lOOO mg/kg levels have been reported to be capable of reducing the formation of N-nitrosamines in the cooked-out fat by 92 and 97%, respectively (49). 

Commercially available nonfat dried milk and dried buttermilk have also been shown to contain small but detectable levels of NDMA (, , ). It has been suggested that N-nitrosamine formation is possible in foods that are dried in a direct-fired dryer (65). In such a dryer, the products of combustion come into direct contact with the food being dried, and N-nitrosamine formation is probably due to the reaction between secondary and/or tertiary amines in the food and the oxides of nitrogen that are produced during fuel combusion (65). 

It has been shown in these studies that the principal, and probably only significant source of NDMA, is malt which had been dried by direct-fired drying (21, 73). It is well known that malts kilned by indirect firing have either low or non-detectable levels of NDMA (74). Consequently, changes in malting procedures have been implemented in both the U.S. and Canada which have resulted in marked reductions in N-nitrosamine levels in both malts and beer (70,74). For example, sulfur dioxide or products of sulfur combustion are now used routinely by all maltsters in the U.S. to minimize N-nitrosamine formation (70). The Canadian malting industry, on the other hand, has... 

We initiated an investigation to examine the possibility of N-nitrosamine formation from the herbicide glyphosate in different soils. It was also of interest to determine whether uptake of N-nitroso compound by plants would occur from soil. 

Davies, R. McWeeny, D. J. Catalytic effect of nitroso-phenols on N-nitrosamine formation. Nature, 1977, 266, 657-658. 

Some effects of phenol- and thiol-nitrosation reactions on N-nitrosamine formation. In Walker, E. A. Castegnaro, M. Griciute, L. Lyle, R. E., Eds. "Environmental Aspects of N-Nitroso Compounds" lARC Scientific Publication No. 19 International Agency for Research on Cancer Lyon, France, 1978 pp. 183-197. 

In 1985, Stuehr and Marietta demonstrated that the macrophage is the major source of N02 and NO, in response to LPS, at least in the mouse. Subsequently, this group showed that addition of LPS and the immune cytokine interferon-y (cytokines are discussed in more detail below) to macrophages results in N-nitrosation of morpholine the N-nitrosamine was not formed by addition of NO2 and morpholine to the macrophages, and the highest levels of N-nitrosamine occurred many hours prior to the peak NO2" formation (Miwa et al., 1987). Thus, treated macrophages are stimulated to produce a reactive precursor to N02 and NO,, which is capable of N-nitrosamine formation. 

Rao GS, Osborn JC, Adatia MR. 1982. Drug-nitrite interactions in human saliva effects of food constituents on carcinogenic N-nitrosamine formation. J Dent Res 61 768-771. 

Mills, A.L. and M. Alexander. 1976. N-Nitrosamine formation by cultures of several microorganisms. Appl. Environ. Microbiol. 31 892-895. 

Another advantage of ascorbate is the prevention of N-nitrosamine formation, although it should be stressed that the amount found in meat products is generally low (Schmidt et al., 1985). It was demonstrated that in the presence of provocative amounts of nitrosamine precursors, GdL and starter cultures support N-nitrosamine formation, a phenomenon that is related to the pH fall. Ascorbate counteracts the reaction but, according to Liao and Seib (1987), more than 1000 ppm is needed in order to substantially limit the N-nitrosamine formation. 

Table 7. Inhibition (%) of N-nitrosamine formation by melanoidins at various pH conditions...

Gray, J.I., and Dugan, L.R., 1975, Inhibition of N-nitrosamine formation in model food systems, J. Food Sci., 40 981. 

Khan, S. U, 1981, N-nitrosamine formation in soil from the herbicide glyphosate and its uptake by plants, "N-nitroso Compounds,"... 

The other area where cooking plays an important role is in N-nitrosamine formation. Janzowski et al. report that decarboxylation of nitrosamino acids is not the essential pathway of nitrosamine formation during the frying of cured meat products. 

The current state of knowledge on N-nitrosamines formation in production processes in the rubber industry is presented. Taking into account that N-nitrosamines are toxic and carcinogenic, or probably carcinogenic for human beings, their emission creates threat for environment and health particularly in the case of rubber goods intended for direct contact with foodstuffs and humans, especially children (soothers, toys etc.) The origin of N-nitrosamines formation in the rubber industry is described. Raw materials, mainly vulcanisation accelerators, which can cause N-nitrosamines formation, are characterised and necessary measures to ehminate their emission or reduce concentration are presented. The best way is to apply safe accelerators which are not... 

RESEARCH DEVELOPMENT IN FIELD OF IMPROVEMENT OF ECOLOGY IN RUBBER INDUSTRY. I. ELIMINATION OF CAUSES OF N-NITROSAMINES FORMATION... 

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