In the EU, styrene is currently authorized for use in food contact materials without a specific restriction, but the European Commission is currently considering developing a migration limit for styrene into food (FPF reported). In 2016, the US State of California added styrene to its Proposition 65 list of carcinogens (FPF reported), and in 2018 the International Agency for Research on Cancer (IARC) concluded that styrene is “probably carcinogenic to humans” (FPF reported). In an article published on July 17, 2022, in the journal Foods, Valeria Guazzotti and co-authors from the Fraunhofer Institute for Process Engineering and Packaging, Freising, Germany, aimed to evaluate styrene concentrations in dairy products and the main factors influencing migration.
Guazzotti and co-authors purchased 17 dairy products, including yogurt, whipped cream, sour cream, and coffee creamers, with different fat contents packaged in polystyrene (PS) from German and Italian supermarkets in 2021. All but the coffee creamers were indicated to be refrigerated products meaning to have a shelf life of 40 days at 5 °C. The scientists stored the samples at 5 °C (exception: coffee creamer at room temperature) and determined styrene levels in the product on the best before date, as well as partly also 20 days before and 15 days after. For the analysis, they used purge and trap gas chromatography coupled with both mass spectrometry and a flame ionization detector. Styrene concentrations remaining in the packaging after emptying were also assessed by acetone-based extraction experiments.
The researchers reported a mean styrene concentration in the food packaging of 300 µg/g polymer (range: 256 – 339 µg/g polymer). Migration levels in the dairy products ranged from 5 to 30 µg/kg of food on their best before date. While 20 days before the end of their shelf life only half of the styrene seemed to have migrated for yogurts with 3.5% fat content, styrene concentrations did not “increase greatly” over the 15 days after the best before date. Coffee creamers were analyzed after storage for six months at room temperature and found to contain 401 µg/kg food corresponding to 4 µg styrene exposure/portion. The authors reported that the “ratio between the surface contact area of the package and the quantity of the food packed (S/F), the time/temperature conditions of production/filling as well as of storage of the products” were “the main factors influencing styrene migration into food under real application of use.” On the other hand, they found that the fat content can influence styrene migration but less than other parameters. Moreover, styrene migration into 50% ethanol was much higher than in refrigerated dairy products. Therefore, the authors raised the question of “whether compliance testing for PS plastics should be adapted taking into consideration the correlation between migration testing by laboratory simulations and migration into real food.”
A review published in January 2022 calculated an average level of 91.53 µg styrene/kg food (FPF reported), and a study published in December 2021 found that in 56% of the analyzed dairy products and desserts styrene concentrations exceeded 10 µg/kg food (FPF reported). Some US states have banned polystyrene food packaging such as Virginia (FPF reported), Maine (FPF reported), and New Jersey (FPF reported). In the EU, the Single Use Plastics Directive (SUP) bans expanded PS but not structurally similar extruded PS, which has resulted in criticism (FPF reported).
Reference
Guazzotti V. et al (2022). “Article Migration of Styrene in Yogurt and Dairy Products Packaged in Polystyrene: Results from Market Samples.” Foods DOI: 10.3390/foods11142120
