Carcinogens nitrosamines

Nitrosamines. Findings that secondary amines, so common in mbber accelerators, can react with NO species to form the suspected human carcinogens, nitrosamines, have prompted active programs to develop alternative accelerators. Neither primary nor tertiary amines form stable nitrosamines and they are generally considered to be safe materials. The abiHty of each type of common mbber accelerator class to form nitrosamines has been summarized and depends on their 1°, 2°, or 3° nature (30). 

Cyanides can be fatal to fish at <1 ppm. Because of concern over the possible in vivo conversion of nitrate into carcinogenic nitrosamines, the nitrate content of drinking water must be strictly controlled. Nitrate and phosphate pollution can also cause eutrophication in still or slow-moving warm waters by stimulation of algae growth in the presence of... 

We have developed a quantitative structure-activity model for the variations in potency among the nitrosamines and, more recently, a related model for the variation in target organ for a smaller set of nitrosamines. We are currently developing a model for interspecies variation in susceptibility toward carcinogenic nitrosamines. The model for organ selectivity requires terms for the parent nitrosamine as well as for the hypothesized metabolites while the model for potency variations contains terms only for the unmetabolized parent compound. 

CARCINOGENIC NITROSAMINES NOT MUTAGENIC TO SALMONELLA WHEN ACTIVATED WITH RAT LIVER S9... 

Some carcinogenic nitrosamines have also been determined by differential pulse polarography146. 

There is a balance to be drawn between risks. Looking at nitrite again, this ion has been used since the Middle Ages to preserve meat. It is the preservative in saltpetre which helps preserve cured meats and stop those who eat them getting botulism. There has been much research to find an alternative to nitrite as it can react with some amines to form carcinogenic nitrosamines. Risk analysis, reviewed in Chapter 4, is an important tool in controlling the use of additives. 

With carcinogenic nitrosamines and DMPO, microsomal preparations give (DMPO—HO ) and an unidentified adduct derived from the nitrosamine (Floyd et al., 1978). Metabolic activation of CC14 has also been examined (Ingall et al., 1978 Poyer et al., 1978). 

Interactions between chemicals may be of a physico-chemical and/or biological nature. Examples of physico-chemical interactions are the reaction of nitrite with aUcylamines to produce carcinogenic nitrosamines, and the binding of toxic chemicals to active charcoal resulting in a decreased absorption from the gastrointestinal tract. It is held that physico-chemical interactions will normally only occur at high doses and therefore are of lesser importance for low-dose scenarios. Physico-chemical interactions will therefore not be considered in any detail in this book. 

Nitrate, nitrite Preservative Present in vegetables form carcinogenic nitrosamines... 

The chemical activation of dibenzylnitrosamine (VI), that is the chemical conversion to the a-acetoxy derivative, would give an intermediate which on hydrolysis would yield the benzylcar-bocation. Hius on the basis of the previous report (, ) the a-acetoxydibenzylnitrosamine (VII) should be a non-mutagenic, non-carcinogenic nitrosamine. 

Nitrosonium ion is an important intermediate in the formation of carcinogenic nitrosamines and to the deamination of DNA and amine-containing amino acids residues in proteins (Wink et al., 1991). It readily adds to the lone electron pair of amine as follows... 

What has inspired the outlandish accusations Scientific ignorance is at least partially responsible. There is much discussion on the Web sites in question about the degree to which SLS and sees are contaminated with carcinogenic nitrosamines. While it is true that trace amounts of nitrosamines have been found in some shampoos, they have nothing to do with sodium lauryl or laureth sulfate. Ethanolamine lauryl sulfates, substances found in a few products, accounted for the insignificant levels of contamination. The similarity in names, I guess, led the chemically illiterate to slur the much more common detergents. 

The gut bacteria may also reduce nitrates to nitrites, which can cause methemoglobinemia or may react with secondary amines in the acidic environment of the gut, giving rise to carcinogenic nitrosamines. 

Although the potentially carcinogenic nitrosamines may he present in foods, particularly cured meats, occurrence is infrequent and at low levels. USDA regulations stipulate that ascorbic acid be added to cured meats at live limes the level of nitrates and nitrites to prevent the formation of carcinogenic Af-nitroso compounds. See also Food Additives. 

Antioxidant activity involving the transfer of two electrons between the ascorbate/dehy-droascorbate redox couple or donation of one electron to inactivate highly reactive free radicals, e.g., protection of vitamin E by reduction of the tocopheryl radical Competitive inhibition in substrate binding reactions, including inhibition of the formation of carcinogenic nitrosamines... 

Thus, in order to avoid excessive uptake, it is very important to determine the BAs of interest in food and beverages. In addition, polyamines may produce carcinogenic nitrosamines in the presence of nitrite (25,26) this is another reason for preventing the accumulation of BAs in cured products. 

As discussed in Section 13.3.6, ascorbate may act to inhibit the formation of carcinogenic nitrosamines from nitrite and dietary amines, and thus reduce the risk of cancer. There is some evidence that vitamin C supplements are protective against the development of gastric cancer. 

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