Rubber products, nitrosamine

The nitrosamine contamination of rubber products originates from amine-containing accelerators and... 

Migration of N-nitrosamines from nipples and pacifiers after incubation in a standard test with artificial saliva for 24 h at 40 C. Concentrations in ug/kg rubber product (- <1 ppb)... 

Consideration is given to the toxicity of nitrosamines formed during rubber vulcanisation in the presence of certain accelerators, the mechanisms by which they are formed, and French, German and European Union regulations relating to nitrosamines in the workplace atmosphere and in rubber products. Methods used in the sampling and analysis of nitrosamines are also described. 6 refs. 

Migration of nitrosamines into consumer products can occur via direct contact of materials such as waxed containers, elastic and rubber etc.81. Morpholine is used extensively as an industrial solvent for wax formulations. The wax formulations are used for coating fruits and vegetables to prevent moisture loss and increase shelf-life of the products. Paper and cardboard packed with morpholine was also found to give rise to NDMA, as these packaging materials were found to be contaminated with NDMA as well. Besides this, rubber products also provided a migratory source for both nitrosamines and nitros-able amine precursors, as trace levels of NDEA and TV-nitrosodibutylamine (NDBA) have been reported in cured meats with amine-based accelerators in the rubber nettings82. 

The presence of A-nitrosamines in the atmosphere, workplace, food, and articles of common use should be monitored and later eliminated. Checking the presence of nitrosamines is particularly important for products intended for direct contact with food and the human body. This applies especially to rubber articles intended for infants and children (e.g., pacifiers and toys) and products used in the food industry (e.g., hoses, belts, machine parts). Despite the fact that nitrosamines in rubber products are present in very low concentrations (parts per million and lower), these compounds can threaten health. 

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. 

In the 1980s it became evident that rubber teats and soothers may release carcinogenic nitrosamines, which are reaction and degradation products from accelerators and stabilisers used in the mbber. Legislation contained in Directive 93/11/EEC prescribes that nitrosamines and nitrosatable substances that can be transformed into nitrosamines in the stomach shall not be released from the teats and soothers in detectable quantities. Methods for the analysis are proposed with the detection limit set to 0.01 mg/kg rubber for nitrosamines and 0.1 mg/kg rubber for nitrosatable substances. 

The Council of Europe s Rubber Resolution on food contact elastomers contains an inventory list of additives and a small section that deals with breakdown products - nitrosamines and amines. The inventory list is described as Technical document No. 1 - List of substances to be used in the manufacture of rubber products intended to come into contact with foodstuffs . This and other relevant Council of Europe documents are available on the Internet website of the Partial Agreement Division in the Social and Public Health Field www.coe.int/soc-sp. 

A more recent Dutch retail survey looked at the migration of A-nitrosamines, A-nitrosatable substances and 2-mercaptobenzothiazole (MET) from 19 samples of teats and soothers. In addition to these species, screening work was also carried out for any other potential migrants. The majority of the teats and soothers were found to be based on sihcone mbber, and the extractable substances were found to be siloxanes. The remaining samples were natural rubber and only one was found to be above the permissible limits, and that was for nitrosatable substances at 0.23 mg/kg. MET was found in only one of the natural rubber products and this was below the migration limit of 0.3 mg/teat. 

Occurrence of volatile nitrosamines in air has been associated with tire and rubber products, leather tanneries, and automotive upholstery, and, as a result, measurable levels of the nitrosamines have been found in certain confined areas, e.g. automobile interiors. Concentrations of NDMA in interior air of automobiles have been found to vary widely due to differences in age of the car, design and decor. Levels of NDMA in interior air of new cars were found to range from <0.02 to 0.83 g/m (Dropkin 1985, Rounbehler et al. 1980). 

SFE has been demonstrated to be a good extraction technique for A-nitrosamines in rubber products. In addition, SFE allows fast analysis with a reduction in solvent waste, time, and manipulation. Although recoveries are not too good, especially for the smaller A-nitrosamines, SFE could be considered as a useful tool to determine these analytes, considering that through its selectivity it provides quite clean extracts in one step." Reche et al." determined A-nitrosamines in latex products by combining supercritical fluids and chemical derivatization. The addition of a denitrosation reagent into the extractor combined with an adequate liquid trap allows elucidation of the presence of A-nitrosamines as well as their potential precursors. 

Nitrosamine-generating chemicals represent an area where suspect materials have been removed from rubber products, even though no governing legislation has yet been drafted. Nitrosamines can be formed when secondary amine accelerators are used to cure mbber. These accelerator changes have a very signiAcant effect on the total rubber industty. 

N-Nitrosamines are widely distributed in various human environments. The concern was initially focused on their widespread occurrence in food and consumer products, as beer, meats cured with nitrite, smoked fish, tobacco and tobacco smoke, rubber products including baby bottle nipples and pacifiers, cosmetics, drug formulations, or herbicides formulations. Much data of their occurrence have been obtained by inadequate analytical methods and must await confirmation. Considerable progress has been made in the development of adequate and specific methods for trace analysis of nitrosamines, and reliable information is expected in the near future. 

The international discussion about carcinogenic N-nitrosamines generated during or after vulcanisation of rubber products started in the late 1970s. It reached its... 

The rate of vulcanisation of a rubber compound is controllable by the choice of accelerator. The range of products offered to the rubber industry has been categorised historically into recognised classes. New developments have resulted in products that improve compound performance and which overcome dermatological problems, and do not generate nitrosamines and other extractable or volatile decomposition products. 

N-Nitroso compounds occur in many operations in the rubber industry. Some nitrosamines (nitrosodiphenylamine, N-N-dinitrosopentamethylenetetramine, polymerized N-nitroso 2,2,4-trimethyl-l,2-dihydroquinoline and N-methyl-N-4-dinitroso aniline) are used as organic accelerators and antioxidants in the production of rubber and often the products are found to be contaminated with such compounds [19]. 

Volatile nitroso compounds were determined in hams processed in elastic rubber nettings by SPE and GC-CLD577. By a similar method A-n i tro sodi ben zy lamine (278b), a semivolatile nitrosamine, was determined in these products by SPE followed by GC interfaced to a nitrosamine-specific TEA-CLD detector the coefficient of variation was 10.6% at the 2.1 ppb level578. The nitrosamines detected in ham most likely originate from the amine precursors in rubber and from the nitrite commonly used in the meat curing process. 

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. 

Sen, N.P., Baddoo, P.A., and Seaman, S.W., 1993, Nitrosamine in cured pork products packaged in elastic rubber netting An update. Food Chemistry 47,387-390. 

Natural rubber has been the traditional material for elastomeric meat netting for many years and this has led to a number of studies into the levels of N-nitrosamines, nitrosatable and other compounds. Work carried out in the US A ° using a typical product produced from natural rubber latex contacted with a 50% ethanol simulant for 150 minutes at 152 °C produced the data shown in Table 12.5. 

Work in Canada has looked into the levels of certain A-nitrosamines in hams that have been in contact with natural rubber netting and control samples that have not. The average results obtained on a sample group of 20 products are shown in Table 12.6. The results obtained illustrate the ubiquitous nature... 

Nitrosamines form as a result of the reaction of nitrosating agents with secondary amines in the rubber. One of the main sources of secondary amines is a number of the accelerators that are used in sulphur-based cure systems, the amines being breakdown products produced as a result of the chemical reactions taking place during vulcanisation. Specific examples of these accelerators, their secondary amine products (i.e. the nitrosatable compounds) and the nitrosamines derived from them, are given in Table 12.7. 

SEN N p, BADDON p A and SEAMAN s w, Nitrosamines in cured pork products packaged in elastic rubber netting an update , Food Chemistry, 1993 47(4) 387-390. 

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