Article

Styrene-acrylonitrile-copolymer and acrylonitrile-butadiene-styrene-copolymer: a study on extractable and migratable oligomers

Authors:
  • Labor Lommatzsch & Säger GmbH
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Abstract

Styrene-acrylonitrile-copolymer (SAN) and acrylonitrile-butadiene-styrene-copolymer (ABS) are gaining in importance as food contact materials. Oligomers and other non-intentionally added substances can migrate into foodstuffs. Five SAN and four ABS samples from the German market and manufacturers were extracted and the extractable oligomers were characterised by high performance liquid chromatography-mass spectrometry/ultraviolet detection/chemiluminescence nitrogen detection/fluorescence detection and gas chromatography-mass spectrometry. Trimers, formed from acrylonitrile and styrene units, were determined to be the dominating group of extractable oligomers in SAN and ABS in concentrations of about 4900–15800 mg/kg material. Furthermore, styrene-acrylonitrile dimers, styrene oligomers, styrene monomer and ethylbenzene were identified in the sample extracts. Migration testing with three consecutive migrations for multiple use articles was performed for two SAN articles. Migration of trimers into water, 3% acetic acid, 10% and 20% ethanol under hot-fill conditions (70°C, 2 h) was not detectable above 9 µg/dm², while 50% ethanol acting as a food simulant for milk (124 µg/dm² trimers during the third migration) was shown to overestimate the actual migration into milk (< 11 µg/dm² trimers at 70°C, 2 h). 2-Amino-3-methyl-1-naphthalenecarbonitrile (AMNC), an oligomer degradation product and a primary aromatic amine, was detected in all material sample extracts (0.3–17.1 mg/kg material) and was released into food simulants in low amounts (< 0.014 µg/dm² during the third migration into 50% ethanol at 70°C, 2 h).

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Using a combination of gas chromatography/mass spectrometry (GC/MS) and gas chromatography/infrared spectroscopy (GC/IR) spectroscopic techniques, chemical contaminants and their hydrolysis products were identified in well water sampled in connection with a suspected childhood cancer cluster located in Dover Township, Ocean County, New Jersey. The drinking water contamination resulted from the leaching of industrial waste chemicals from drums that were disposed of at the site known as Reich Farm. Contaminants identified include dinitrile-tetralin compounds, known as 'trimers,' that are by-products of a polymerization process widely used by several polymer manufactures during the 1970s and 1980s (and still used today). Also identified were 'trimer' hydrolysis products, formed by the hydrolysis of their nitrile groups to amides. These industrial contaminants were not present in any of the mass or IR spectral library databases, and their identification required unconventional spectroscopic methods (including high resolution mass spectrometry, chemical ionization mass spectrometry, and IR spectroscopy), along with scientific reasoning and interpretation. It is currently not known whether these chemical contaminants are responsible for the childhood cancers observed in this area.
Article
To examine the estrogenic activities of styrene oligomers, we carried out cell proliferation assays with estrogen-sensitive MCF-7 cells and competitive binding assays to human estrogen receptor [alpha] (hER[alpha]). The styrene oligomers tested were 1,3-diphenyl propane (SD-1), 2,4-diphenyl-1-butene (SD-2), cis-1,2-diphenyl cyclobutane (SD-3), trans-1,2-diphenyl cyclobutane (SD-4), 2,4,6-triphenyl-1-hexene (ST-1), 1a-phenyl-4a-(1'-phenylethyl)tetralin (ST-2), 1a-phenyl-4e-(1'-phenylethyl)tetralin (ST-3), 1e-phenyl-4a-(1'-phenylethyl)tetralin (ST-4), 1e-phenyl-4e-(1'-phenylethyl)tetralin (ST-5), 1e,3e,5a-triphenylcyclohexane (ST-6), and 1e,3e,5e-triphenylcyclohexane (ST-7). In the MCF-7 cell proliferation assay, styrene trimers (ST-1, ST-3, ST-4, and ST-5) had the highest proliferative activities of the compounds tested. The relative potency of these chemicals was 0.0002-0.0015%, which was comparable with that of bisphenol A (0.0001-0.0025%), and their relative proliferative effect was 51-104%. Styrene dimers (SD-3 and SD-4) also significantly increased the cell yields. However, SD-1, SD-2, ST-2, ST-6, and ST-7 had insignificant proliferative activities. The competitive binding assay revealed the binding affinity of some styrene oligomers for hER[alpha]. The order of their binding potency for hER[alpha] was as follows: ST-4 > ST-2 > ST-3 > ST-5 > ST-1 > SD-3 > SD-4 > SD-2 > SD-1. ST-6 and ST-7 did not appear to bind to hER[alpha]. The present studies indicate that styrene dimers SD-3 and SD-4 and styrene trimers ST-1, ST-3, ST-4, and ST-5 have estrogenic activity on MCF-7 cells and binding affinity for hER[alpha]. These compounds might be endocrine disrupters.
Article
Styrene trimers migrate from polystyrene food container into foods. We evaluated the estrogenic activity of styrene trimers such as 2,4,6-triphenyl-1-hexene (ST-1), 1a-phenyl-4a-(1'-phenylethyl)tetralin (ST-2), 1a-phenyl-4e-(1'-phenylethyl)tetralin(ST-3), 1e-phenyl-4a-(1'-phenylethyl)tetralin (ST-4), and 1e-phenyl-4e-(1'-phenylethyl)tetralin (ST-5) using the reporter-gene assay with MVLN cells stably expressing the estrogen-stimulated reporter gene, and it was confirmed that ST-1, ST-3, and ST-4 had estrogen-like activity. On the other hand, ST-2 and ST-5 had anti-estrogen-like activity. We examined the estrogenic activity in vivo of ST-1, ST-3, and ST-4. The styrene trimers were administered to pregnant rats, and the effects on the offspring were examined. ST-1, ST-3, or ST-4 (0, 10, 100, 1000 microg/kg body wt/day) were subcutaneously injected into pregnant rats from gestational Day 11 through 17, and the male offspring were sacrificed on postnatal days (PND) 101-103. In the ST-4 treatment groups, the relative anogenital distance on PND 3 was significantly shortened. The relative testis weight was remarkably decreased in all styrene trimer treatment groups. Relative weights of the prostate and epididymides significantly decreased in the ST-4 treatment groups. The relative brain weight was markedly reduced in the ST-3 and ST-4 treatment groups. A significant decrease of the Sertoli cell count was observed in the ST-1 and ST-4 treatment groups. The serum follicle stimulating hormone level was remarkably reduced in all styrene trimer treatment groups. The luteinizing hormone level was significantly decreased and the testosterone level increased in the ST-1 and ST-4 groups. These results suggest that prenatal exposure to estrogenic styrene trimers at low levels obstructed genital organ development, and disrupted the endocrine systems of male rat offspring.
Gemessene Gehalte an Styrol-Oligomeren in Lebensmittelsimulanzien : gesundheitliche Risiken sind unwahrscheinlich (Aktualisierte Stellungnahme 023
  • Risikobewertung Bundesinstitut Für
Bundesinstitut für Risikobewertung. 2016 April. Gemessene Gehalte an Styrol-Oligomeren in Lebensmittelsimulanzien : gesundheitliche Risiken sind unwahrscheinlich (Aktualisierte Stellungnahme 023/2016). p. 1-9.
Handbuch der technischen Polymerchemie
  • A Echte
Echte A. 1993. Handbuch der technischen Polymerchemie. Weinheim, Germany: VCH.
Genotoxicity of styrene-acrylonitrile trimer in brain, liver, and blood cells of weanling F344 rats
  • C A Hobbs
  • R S Chhabra
  • L Recio
  • M Streicker
  • K L Witt
Hobbs CA, Chhabra RS, Recio L, Streicker M, Witt KL. 2012. Genotoxicity of styrene-acrylonitrile trimer in brain, liver, and blood cells of weanling F344 rats. Environ Mol Mutagen. 405(April):391-405. doi:10.1002/em.