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Analysis of chemical substances in balloons 1 Introduction
Balloons are popular toys among children and the market offers a variety of different balloons. Even though balloons are not recommended for children under three years it is most likely that children of that age will get in contact with balloons. Almost all the balloons are made of natural latex. Special focus is on the release of nitrosamines from balloons as several studies have shown that carcinogenic nitrosamines are given off in migration tests to artificial saliva. The nitrosamines are formed from secondary amines liberated from the accelerators used. Other substances might be harmful to the health, i.a. problematical such as thiuram accelerators and mercaptobenzothiazole (MBT), which may cause type IV-allergy. Balloons are dyed in different colours and therefore colorants may also present a risk. Finally it is a well-known fact that for a small part of the population the proteins in natural latex may cause type I-allergy, which may be life threatening. This aspect will not be studied in detail in this limited project, but it should be added that especially by bursting of balloons there is a risk of affecting the proteins if the balloons are powdered with corn starch or other release agents (talc) which are added to the finished product in order to reduce the tackiness of the rubber. Natural rubber is extracted from the tree Hevea Brasiliensis, where the rubber latex is drained from the cortex in the form of latex. The latex is stabilised with ammonia to avoid coagulation. Immediately after dispersing of rubber chemicals the latex can be used for production of balloons or other dipped products (e.g. bottle teats, gloves and condoms). A prevulcanisation will often take place when heating the latex solution to 60-70 °C for a shorter period (approx. 6 hours). The latex used for balloons normally has a dry matter content of 60 % w/w. 1.1 Nitrosamine formationNitrosamines can be formed oxidatively from the amines that can be liberated from the applied thiuram-ultra accelerators during vulcanisation of the natural latex. The most common accelerators for dipped latex products are the following:
The most frequently applied accelerators are salts of dithiocarbamic acid in the form of zinc dimethyldithiocarbamate, zinc dimethyldithiocarbamate and zinc di-n-butyldithiocarbamate in the order given. By vulcanisation carbon disulfide will be formed during the release of the secondary amines, which are part of the chemical building blocks for the accelerators:
In the presence of nitrosatable substances (NOX) all five secondary amines can form nitrosamines. Due to the low vapour pressure the nitrosamine from dibenzyl amine is considered to be relatively unproblematic in health terms, but is still one of the nitrosamines to be quantified according to DS/EN 12868. Nitrosamines may also be formed from other accelerators or sulphur donors, which might be ingredients in the latex recipe, e.g. dimethylthiuram mono- and disulfide, diethylthiuram mono- and disulfide as well as 4,4´-dithiomorpholine. 2-Morpholino-benzothiazole sulfenamide is a sulphenamide accelerator, which may cause formation of N-nitroso-morpholine. MBT is a mercaptothiazole accelerator, known as a medium strong accelerator, and which is also being used as accelerator in natural rubber latex. It is used by dipped products together with ultra accelerators of the thiocarbamate or the thiuram type to provide improved process safety. Further, MBT is being used within production of technical rubber products as it is one of a few accelerator types which do not give off nitrosamines during vulcanisation. 1.2 Legislation/ recommendations on limit values for nitrosamines and nitrosatable substances in balloons based on laboratory analyses, etc.There is, however, no actual legislation for balloons as is the case for e.g. teats for soothers and feeding bottles. However, balloons, which are marketed and sold in Germany must comply with the German limit values laid down for consumer products according to BgVV recommendation XXI. Based on exposure scenarios the BfR ”Bewertung von Nitrosaminen in Luftballons” (ref. 4) has laid down a maximum liberation of nitrosamines from balloons of 0.2 mg/kg and 2 mg/kg for nitrosatable substances. EU directive 93/11/EEC stipulates that rubber teats and soothers may not release nitrosamines and nitrosatable substances in amounts larger than 10 µg per kg rubber for nitrosamines and 100 µg per kg rubber for nitrosatable substances for artificial saliva (DS/EN 12868). In the USA the limit value by a dichlormethane extraction of 20 µg per kg for soothers and 10 µg per kg for rubber teats. A German investigation has shown that for approx. 81% of the investigated balloons in 2001, the release of nitrosamines and nitrosatable substances (nitrosamine precursors) for artificial saliva according to EN 12 868 (1 hour at 40 °C) was higher than the limit values applying for soothers and rubber teats. An analysis in 2003 of 14 balloons established that only one of these complied with the limit value of less than 10 µg per kg for nitrosamines. The nitrosamines found in the investigation were N-dimethylnitrosamine (97 % of the balloons), N-dibutylnitrosamine (93 % of the balloons) and diethylnitrosamine (34 % of the balloons). In 9 % of the balloons was found N-nitrosomorpholine. It is not surprising to find the three first-mentioned types of nitrosamines, as the most frequently used accelerators in natural latex will be capable of forming these nitrosamines. The presence of N-nitrosomorpholine in 9 % indicates that morpholine derivates are being used either as sulphur donor or as accelerator (sulfenamide types). According to ref. 3 the European industry has responded to the proposed amendment to the Toys Directive concerning nitrosamines in balloons, that the industry is aware of the risk, but that there is presently no available technology for complete elimination of the nitrosamines. It is further stated that a possible total ban on nitrosamines in balloons will fall notably hard on the European balloon industry and in the worst case it completely close the industry.
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