Migration of toxic elements from recycled paper food contact materials to food simulants
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Discussion Influence of migration and extraction approaches on the extractability of elements from paper and board FCMs Compared with DFM, which uses less polar solvents such as acetone and methanol, migration samples with higher po- larity and acidity, such as AFM, LFM, and FFM (containing water and ethanol), exhibited increased migration of elements from recycled paper FCMs. This difference is evident in both the number and quantity of detected elements. The extent of migration is directly proportional to the polarity and acidity of the solvents used. This relationship has been previously noted by Dong et al. (2015) and Li (2020), who studied the impact of acidity on the migration of elements like lead and cadmium from ceramic FCMs. Specifically, the AFM sample, prepared with 3% (volume fraction) acetic acid, showed higher migration compared with the LFM sample, which contains 10% (volume fraction) ethanol in water. The increased migration in AFM can be at- tributed to acetic acid’s ability to break down bonds more effectively, facilitating the release of elements from the paper matrix. Similar trends were observed between the FFM and DFM samples, simulating contact with fatty and dry foods, respectively. While the same paper FCM sample was used for AFM and LFM preparations, the FFM and DFM sam- ples were prepared using different paper FCMs tailored to their respective food contact scenarios, which might intro- duce variations due to the inherent differences in the paper compositions. Kishi et al. (2024) used distilled water, 4% (volume frac- tion) acetic acid, and 50% (volume fraction) ethanol to study antimony and germanium migration from polyethylene tereph- thalate bottles. They reported the highest migration in 50% (volume fraction) ethanol, which was attributed to the potential of ethanol to swell the FCM, thereby enhancing element accessi- bility to the food simulant. Although germanium and antimony were not detected in this study, this highlights the influence of solvent interaction with FCM matrices, whether plastic, paper, glass, or other materials. The swelling effect of ethanol can sig- nificantly increase the contact surface area between FCM and the food simulant, leading to higher migration rates. In addition, elements may be poorly soluble and present as metals, salts, or organometals, requiring a complex process of accessing and dissolving, including a transformation (oxi- dation) step, which takes time and activation energy (tem- perature). This process can be particularly challenging for solvents like acetone and methanol, which might not provide the necessary conditions to facilitate the complete extraction of certain elements. Migration samples consistently exhib- ited greater element migration from the recycled paper FCMs compared with extracts. The AFM, LFM, and FFM samples showed higher numbers and quantities of detected elements compared with their extraction counterparts, LAE and DE, which demonstrated overall lower element migration. However, the disparity between migration samples and ex- tracts diminished with decreasing polarity of the food simu- lants and solvents, leading to minimal differences between the DFM and DE samples, both of which use a methanol and acetone (1:1, volume ratio) mixture as their final solvent. This suggests that the extraction method’s efficiency is influ- enced by the solvent’s polarity, with less polar solvents re- sulting in lower overall extraction efficiency. In summary, the
physicochemical characteristics of the food simulant and ex- traction solvent significantly influence the extent of element migration from recycled paper FCMs. Acidity and polarity play a pivotal role in elemental migration, surpassing the im- pact of specific sample preparation methods in these findings. Compatibility of migration samples and extracts with ICP-MS analysis Migration and extraction approaches often use solvents with high organic content that interfere with ICP-MS analysis. To address this, two methods were explored: diluting the organic content below 2% (volume fraction) with nitric acid in water, drying the migration sample or extract, and then dissolving it in water and nitric acid. Both methods were compatible with ICP-MS and yielded comparable results in terms of de- tected elemental quantities. The dilution approach increased the LOR for elements, reducing their concentrations by fac- tors of five (AFM and LFM), 25 (FFM), and 50 (DFM, DE, LAE, and FE). Consequently, trace elements in very low quan- tities were only detectable using the ‘drying and dissolving’ method, making it the most effective for analyzing samples with high organic content. Concerning the extraction and migration of toxic metals from paper FCMs Migration samples and extracts from recycled paper FCMs contained significant quantities of toxic metals. Arsenic, lead, mercury, and cadmium were detected in amounts exceeding the SMLs stipulated by the Regulation (EU) 2023/915. Elevated levels of aluminum, barium, zinc, and chromium also sur- passed the migration limits specified in the Dutch Commodities Act. SMLs for lithium, beryllium, cobalt, nickel, molybdenum, and uranium are not explicitly defined in current legislation, but their quantities exceed the cTDI values. The OpenFoodTox database lacks specific reference thresholds for lithium. The presence of these toxic elements in migration samples indicates their transfer into food simulants at potentially harmful levels, violating Article 3.1 of the Regulation (EC) 1935/2004. The AFM samples exhibited the highest concentrations of toxic elements, suggesting acidic aqueous food products as signifi- cant substrates for migration. The LFM and FFM samples showed moderate migration levels, whereas dry food simulants were least conducive to element migration. Consequently, dry food products like bread may pose lower risks of hazardous elemental migration from recycled paper FCMs. The acidity and polarity of food simulants can predict elemental migra- tion likelihood. Packaging acidic foods in glass containers may be preferable, whereas paper FCMs are suitable for dry foods with minimal water content. Conclusions Toxic elements, including lead, arsenic, cobalt, chromium, cadmium, barium, and uranium, were detected in the re- cycled paper FCM samples. While harmonized SMLs exist in the EU for lead, arsenic, mercury, tin, and cadmium under the Regulation (EU) 2023/915, additional SMLs are found in the national legislations of certain European member states. The substantial presence and migration of these toxic metals from recycled paper FCMs, as evidenced in this study and corroborated by data in the FCCmigex database, under- score the necessity for risk assessment and harmonization of SMLs for other toxic elements at the EU level. The migration
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