In an article published on February 16, 2023, in the journal Science of the Total Environment, Di Feng from Beijing Technology and Business University, Beijing, China, and co-authors tested 42 food contact articles (FCA) made of silicone rubber for their cytotoxicity, endocrine activity, and chemical composition.
The scientists purchased 31 articles of kitchenware (i.e., 15 molds, 5 plates, 4 chopping boards, 4 kneading dough bags, and 3 cups) and 11 infant bottle nipples with a silicon component on the Chinese market. After performing migration experiments in 95% ethanol at 70 °C for 2 h, they subjected the samples to gas chromatography-mass spectrometry (GC-MS), ultra-high performance liquid chromatography-quadrupole time-of-flight (UPLC-Q-TOF)-MS, and inductively coupled plasma-MS for the quantitative and qualitative analysis of the compounds. For toxicity assessment, they used human cervical cancer cells (HeLa) to test for cytotoxicity as well as estrogenic, anti-estrogenic, androgenic, and anti-androgenic activity (dual-luciferase reporter gene assay). The researchers also investigated the correlation between the chemicals present in the samples and the migrate’s toxicity.
Feng and co-authors reported that almost all of the 31 kitchenware samples were cytotoxic in their assays (96%) and 64% induced estrogenic, 19% anti-estrogenic, 42% androgenic, and 39% anti-androgenic activities, respectively. In contrast, none of the bottle nipples was toxic on the tested endpoints. Concerning chemical composition, the authors detected more compounds by GC compared to UPLC-Q-TF MS, but with both methods silicone oligomers were the predominant compounds in the migrates. A total of 26 organic compounds and 21 metals were identified and quantified in the migrates from kitchenware. They included cyclic methylsiloxanes, phthalic acid esters plasticizers, fatty acid plasticizers, and lubricants, amongst others. The comparison of the estimated daily intake (calculated based on the migration levels) with the threshold of toxicological concern (TTC) thresholds, led the scientists to conclude that D5-D18, palmitic acid, stearic acid, oleamide, and erucamide are of concern.
Furthermore, Feng et al. reported that “metals contributed 71% of biologic effects in all substances and combinations, although the migration of these single metals meets the specific migration limit.” Other substances that strongly correlated with cytotoxicity and endocrine activity were phthalate plasticizers, methylsiloxanes, fatty acid plasticizers, and lubricant. Given the complex chemical composition of the samples, the authors recommended combining chemical analysis and bioassays to assess the composition and overall toxicity, and eventually, the safety of the final products. This conclusion was also drawn by previous studies which used the combination to analyze a wide variety of products, based on fossil as well as natural resources (FPF reported and here).
Already in 2016, researchers from Beijing analyzed migrates of 30 silicon rubber FCAs for their chemical composition. In their non-target screening, they identified 140 compounds of which they prioritized 53 for further safety evaluation (FPF reported). A study by the European Consumer Organization (BEUC) tested 44 silicon baking molds sold in Europe. The high release of chemicals, which included several substances of very high concern (SVHCs), led BEUC to call for stricter EU rules for silicon FCAs (FPF reported). Only five Member States have their own national rules for silicone food contact materials (FCMs), but none of them address specific contaminants released. The European Commission has committed to revising the EU food contact material legislation, with preparatory work on a legislative proposal currently underway (FPF reported and here).
Not only silicones but also FCAs made of other polymers can contain endocrine-disrupting chemicals (EDCs). In a review article published on February 15, 2023, in the journal Comprehensive Reviews in Food Science and Food Safety, Khairun Tumu and co-authors from Iowa State University, Ames, USA, review two groups of EDCs in food packaging, phthalates and bisphenols including bisphenol A and bisphenol S. The focus of the review is two-fold. First, it summarizes the properties, uses, and levels of phthalates and bisphenols in FCMs, their toxicity, exposure routes, and how these compounds are regulated under different legislation. Second, it discusses analytical techniques for the detection and quantification of the two chemical groups. With their review, the authors aim to provide “an updated resource for addressing regulatory concerns and potential impact to human and environmental health by determining appropriate methods and limitations for detecting” EDCs in FCMs.
Yongjun Xiao from the International Food & Water Research Center, Singapore, and co-authors analyzed eight commercially available vegetable oils for the presence of nine phthalates. In their article published on February 21, 2023, in the journal Toxics, they describe that they aimed to develop a method based on atmospheric pressure gas chromatography with tandem mass spectrometry (APGC-MS/MS) to determine phthalates in oils. The scientists found the method to have a quantification limit of 0.015-0.058 mg/kg oil and be “suitable for investigating dietary exposure and future proof against decreases to the regulatory limit.” Applying it to the eight vegetable oils, they only detected diethyl hexyl phthalate (DEHP, CAS 117-81-7) in seven and dibutyl phthalate (DBP, CAS 84-74-2) in three samples in concentrations up to 0.39 and 0.13 mg/kg, respectively.
References
Feng, D. et al. (2023). “Cytotoxicity, endocrine disrupting activity, and chemical analysis of 42 food contact silicone rubber products.” Science of the Total Environment. DOI: 10.1016/j.scitotenv.2023.162298
Tumu, K. et al. (2023). “Endocrine modulating chemicals in food packaging: A review of phthalates and bisphenols.” Comprehensive Reviews in Food Science and Food Safety. DOI: 10.1111/1541-4337.13113
Xiao, Y. et al. (2023). “Simultaneous Determination of Nine Phthalates in Vegetable Oil by Atmospheric Pressure Gas Chromatography with Tandem Mass Spectrometry (APGC-MS/MS).” Toxics. DOI: 10.3390/toxics11030200
