Migration of antimony from PET bottles into beverages: determination of the activation energy of diffusion and migration modelling compared with literature data

Abstract

Plastics bottles made from polyethylene terephthalate (PET) are increasingly used for soft drinks, mineral water, juices and beer. In this study a literature review is presented concerning antimony levels found both in PET materials as well as in foods and food simulants. On the other hand, 67 PET samples from the European bottle market were investigated for their residual antimony concentrations. A mean value of 224 ± 32 mg kg⁻¹ was found, the median was 220 mg kg⁻¹. Diffusion coefficients for antimony in PET bottle materials were experimentally determined at different temperature between 105 and 150°C. From these data, the activation energy of diffusion for antimony species from the PET bottle wall into beverages and food simulants was calculated. The obtained value of 189 kJ mol⁻¹ was found to be in good agreement with published data on PET microwave trays (184 kJ mol⁻¹). Based on these results, the migration of antimony into beverages was predicted by mathematical migration modelling for different surface/volume ratios and antimony bottle wall concentrations. The results were compared with literature data as well as international legal limits and guidelines values for drinking water and the migration limit set from food packaging legislation. It was concluded that antimony levels in beverages due to migration from PET bottles manufactured according to the state of the art can never reach or exceed the European-specific migration limit of 40 µg kg⁻¹. Maximum migration levels caused by room-temperature storage even after 3 years will never be essentially higher than 2.5 µg kg⁻¹ and in any case will be below the European limit of 5 µg kg⁻¹ for drinking water. The results of this study confirm that the exposure of the consumer by antimony migration from PET bottles into beverages and even into edible oils reaches approximately 1% of the current tolerable daily intake (TDI) established by World Health Organisation (WHO). Having substantiated such low antimony levels in PET-bottled beverages, the often addressed question on oestrogenic effects caused by antimony from PET bottles appears to be groundless.

Keywords:

• exposure modelling
• metals analysis – ICP/MS
• quality assurance
• migration
• diffusion
• heavy metals
• packaging
• PET
• beverages
• fruit juices
• drinking water

Acknowledgements

Thanks are due to Dominik Fiedler, Manuel Huber, Annika Seiler, Veronika Wildgruber and Gerd Wolz (Fraunhofer IVV) for experimental contributions and fruitful discussions. Information from Dr Yoko Kawamura, National Institute of Health Sciences, Tokyo, on the Japanese PET market is gratefully acknowledged.