An article published on December 8, 2017 in the peer-reviewed journal Food Additives & Contaminants: Part A reported on N-nitrosamines migrating from food contact materials (FCMs). Friederike Kuehne and colleagues from the German Federal Institute for Risk Assessment (BfR), Department of Chemical and Product Safety, National Reference Laboratory for Food Contact Materials, Berlin, Germany, developed a liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry (LC-APCI-MS/MS) method allowing quantification of 13 N-nitrosamine species migrating from elastomeric FCMs into the food simulants deionized water, 3% acetic acid, and 10% and 50% ethanol. This new method is on average ten times more sensitive than the one using the gas chromatography-thermal energy analyzer (GC-TEA), referred to in BfR’s Recommendation XXI for commodities based on natural and synthetic rubber, published in 2016.
In ten out of twelve elastomer FCM samples examined, up to six different N-nitrosamines could be detected in different food simulants. The two samples which did not release detectable N-nitrosamines into any of the food simulants were the “IIR sheet (butyl rubber)” and the swing stopper sealing ring made of a thermoplastic elastomer (TPE) based on styrene-ethylene-butadiene-styrene (SEBS) co-polymer.
Among the ten samples with measurable N-nitrosamine content, the BfR-recommended limit of 1 µg/dm2 for total migrating N-nitrosamines was exceeded only for one sample, namely the semi-finished SEBS TPE FCM sample, which released a maximum of 2.1 µg/dm2 of nitrosamines in 10% ethanol after ten days of migration at 40 °C. The main contributor was N-nitrosomethylphenylamine (NMPhA, CAS 614-00-6), with 1.1 µg/dm2. The authors noted that this finding was “unexpected” because styrene block polymer TPEs are not vulcanized and hence their production does not require the use of vulcanization accelerators, which are typical precursors of nitrosamines in rubbery FCMs. However, styrene based TPEs are typically processed on “conventional rubber machines,” the authors informed. Therefore, further research should address the question as “to what extent the dual use of machinery may lead to unacceptable contamination.” The authors concluded that their finding “presents a so far isolated case and should therefore be considered as call for further investigation of potential N-nitrosamine contamination of TPEs.”
N-nitrosamine substances have a generic chemical structure of R2N-N=O. Most N-nitrosamines are known to exhibit carcinogenic properties, with formation of DNA adducts as well as generation of reactive nitrogen and oxygen species being implicated as potential mechanisms. During rubber production, N-nitrosamines may be formed due to the reaction of vulcanization accelerators such as dithiocarbamates and thiurames with nitrogen oxide species. Thus, FCMs made of natural or synthetic rubber, so-called elastomers, may be a potential source of N-nitrosamine contamination of food. Examples of articles made of such FCMs include “baby bottle teats, seals in household items and food industry machinery, conveyor belts, gaskets, [and] tubing.”
BfR (July 1, 2016). “XXI. Commodities based on natural and synthetic rubber.” (pdf)
Kuehne, F., et al. (2017). “N-nitrosamines migrating from food contact materials into food simulants: Analysis and quantification by means of HPLC-APCI-MS/MS.” Food Additives & Contaminants: Part A (published December 8, 2017).