Chemicals, nitrosamines from

A-Nitrosamines in rubber products are by-products of the reactions taking place during the vulcanization of rubber mixtures [80]. They are formed from some chemical compounds such as secondary amines (accelerators, antioxidants) via nitrosation by nitrogen oxides present in the surrounding air. These reactions occur inside the rubber product and on its surface. The resulting A-nitrosamines from the interior of the rubber can diffuse to the surface of the article, and then to the environment or media in which the product is used. A-Nitrosamines can also be incorporated in the rubber mixture by contamination of raw materials during preparation. 

Lastly, but importantly, in a chapter titled Chemical Carcinogenesis, the following cited authors note that vitamin C inhibits carcinogenesis in the stomach by blocking the formation of nitrosamines from the nitrosation of amines (Williams and Weisberger, in Amdur et al.,1991, p. 146). This is aside from the usual view of medical orthodoxy that vitamin C has no special therapeutic effects other than the alleviation of scurvy (e.g., Marcus and Coulston, in Pharmacological Basis of Therapeutics, pp. 1568-1571). 

A-Nitrosamines are formed by a chemical reaction between a secondary or a tertiary amine and a nitrosating agent, such as chemicals derived from nitrites or nitrogen oxides. FYimary amines react with nitrosating agents to form unstable A-nitroso derivatives which degrade to olefins and alcohols. 

The persistence of the N-nitrosamine that may be formed in soil will depend on a host of conditions, such as soil type, organic matter content, clay content, pH, the microflora present in the soil, moisture content and temperature, etc. Superimposed on all these factors will be the chemical nature of the pesticide. The N-nitrosoatrazine ( ) formed in soil from the herbicide atrazine ( ) was shown to be rapidly disappeared (1). Thus, in soil W-nitrosoatrazine was observed after one week, but was absent 4 and 10 weeks later (Table IV). In contrast, N-nitroso-butralin (11 ) persisted much longer than N-nitrosoatrazine (9) under the same conditions (Table V) and was still detectable after 6 months (3). Our studies demonstrated that N-nitrosoglyphosate is persistent in the soil. Fox soil treated with 20 ppm of nitrite nitrogen and 740 ppm glyphosate contained about 7 ppm of N-nitrosoglyphosate even after 140 days (6). 

Nitrosamine standards were obtained from Thermo Electron Corp. (Waltham, MA) and diluted to appropriate concentrations with DCM. N-Nitrosobis(2-hydroxypropyl)amine (BHP) and NDELA were prepared by the Eppley Institute Chemical Services Unit. 

The effort required to establish identity of a nitrosamine in an environmental sample depends on the nature of the problem and the specificity of the primary detection system. TEA response is much stronger evidence of identity than response from a flame ionization or nitrogen-specific detector. If TEA response is supported by chemical (9) or ultraviolet photolysis (8) supporting data, identification is adequate for many... 

Other environmental properties of interest are those that govern movement of chemicals, for these properties can influence not only the possibility of human exposure but also the lifetime and fate of the chemical. Clearly, if a nitrosamine is formed in, or introduced into, the soil and stays there, it presents little threat to man, and its lifetime will depend on the chemical or microbiological properties of the soil. If it should move to the surface and volatilize into the atmosphere, on the other hand, there will exist the possibility of human exposure via inhalation and also the possibility of vapor-phase photodecomposition. If a nitrosamine were to leach from soil into water, it could perhaps be consumed in drinking water alternatively, exposure of the aqueous solution to sunlight could provide another opportunity for photodecomposition. 

The NO + 03 chemiluminescent reaction [Reactions (1-3)] is utilized in two commercially available GC detectors, the TEA detector, manufactured by Thermal Electric Corporation (Saddle Brook, NJ), and two nitrogen-selective detectors, manufactured by Thermal Electric Corporation and Antek Instruments, respectively. The TEA detector provides a highly sensitive and selective means of analyzing samples for A-nitrosamines, many of which are known carcinogens. These compounds can be found in such diverse matrices as foods, cosmetics, tobacco products, and environmental samples of soil and water. The TEA detector can also be used to quantify nitroaromatics. This class of compounds includes many explosives and various reactive intermediates used in the chemical industry [121]. Several nitroaromatics are known carcinogens, and are found as environmental contaminants. They have been repeatedly identified in organic aerosol particles, formed from the reaction of polycyclic aromatic hydrocarbons with atmospheric nitric acid at the particle surface [122-124], The TEA detector is extremely selective, which aids analyses in complex matrices, but also severely limits the number of potential applications for the detector [125-127],... 

If animal systems are chosen, preparations derived from fish (see, e.g., Kada, 1981) and birds (Parry et al., 1985) have been used. However, by far the most widely used and validated are those derived from rodents, in particular, the rat. Hamsters may be preferred as a source of metabolizing enzymes when particular chemical classes are being screened, for example, aromatic amines, heterocyclic amines, N-nitrosamines and azo dyes (Prival and Mitchell, 1982 Haworth et al., 1983). 

Table 5 gives the exposure level of different N-nitrosamines analogously arising as pollutants from various chemical industries73. 

Because N-nitroso compounds can have such a wide variety of physical and chemical properties, and because they can be formed from a wide variety of precursors. analysis at the trace level is difficult. The most widely used technique is the use of a nitrosamine specific detector, called a TEA, which can be interfaced to either a gas chromatograph (GC) or a high pressure liquid chromatograph (HPLC) (31,32). General screening procedures which have been designed to detect all N-nitroso compounds have been developed (33,34). Structural confirmation of N-nitroso compounds is gen-... 

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. 

Uses/Sources. Research chemical impurity in herbicides treflan, isopropalin, and triflu-ralin contaminant in wastewater from chemical factories and production of cheese and brandy and other liquors. AT-nitrosamines are frequently produced during rubber processing and may be airborne in the workplace. 

One of the more important classes of chemical carcinogens are N-nitrosamines. They are important because practically all of the simple nitrosamines are carcinogenic, they are widely distributed in our environment and can be formed in the stomach from secondary and tertiary amines and the ubiquitous nitrite ion. Moreover, nitrosamines are very organ-specific. Thus, a given nitrosamine will produce a liver or an esophageal tumor, regardless of the route of administration of the carcinogen. This fact makes nitrosamines very useful in the study of mechanisms of tumor induction (1). 

Aerojet (fine chemicals division now acquired by AMPAC) also has reported technology to prepare and use diazomethane on large scale from the reaction of NaOH with N-methyl-N-nitrosamine. This process differs for the Phoenix process in that relatively large amounts of a low-boiling volatile solvent, diethyl ether, are uhlized to limit bulk liquid temperatures and minimize headspace concentrations of diazomethane [22]. 

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