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Mathematic Modelling of Migration of Nanomaterials from Food Contact Polymers
Abstract
The objective of the book chapter is to provide the state of the art in migration modelling, understood as diffusion controlled mechanism following Fick's law of diffusion, for NPs in food contact plastics. In the first part of this chapter migration modelling of conventional plastics additives will be described as a basis for modelling approaches of NPs which is the topic of the second part of this chapter.
... In this critical review [12], any unambiguous positive proof of migrating nanoparticles was not found. Furthermore, a publication [13] dealing with mathematic modelling of nanoparticle migration from polymers indicated that nanoparticles in the size range as used in food contact polymers do not have the potential for diffusion in polymers and therefore would not be able to migrate into foods under usual packaging and food contact application conditions as long as they are fully incorporated and embedded in the polymer host matrix. The authors concluded that consumers will not be exposed to nanoparticles when the contact surface of the host polymer is intact and not altered by mechanical surface stress during application. ...
... Nanoparticles with diameters larger than 5 nm are known to have extremely low diffusion coefficients in polymers [13,28] so that for usual size distributions, which do not show fractions in this low size range, migration cannot be expected under usual conditions of use as long as the host polymer fully covers the nanoadditive and encapsulates it completely. A NM incorporated into a polymer nanocomposite can be measured and characterized by transmission electron microscopy (TEM) imaging. ...
... From this it is hypothesized that the parameter 'size' of a migrant combines migration modelling of both nanoparticles and molecules and is applicable to both species. On this basis, a migration modelling approach for nanoparticles was recently developed which considers nanoparticles as quasi-molecules and, thus, enables estimating diffusion coefficients, and hence the calculation of migration values for very small nanoparticles in the diameter range up to 10 nm [13]. ...
The use of nanoadditives in food contact materials requires risk assessment to ensure consumers’ safety. The evaluation of health risk is based on the combination of two elements: hazard and exposure. For nanomaterials (NM) used as additives in nanocomposites, the exposure is directly linked to the level of migration or release of the NM into the food. In principle, appropriate methods for experimental determination and theoretical estimation of migration are available but need diligent considerations to avoid erroneous conclusions from the measured data. We propose a comprehensive test scheme based on these methods, starting with characterization of the nanomaterial itself and when incorporated in the polymer. These data form the basis for making a decision whether migration of the NM can be excluded by migration theoretical considerations or if experimental migration testing and/or abrasion testing for mechanical release should be carried out. Guidance to and considerations for each of these steps and regarding the applicable methods are discussed. In conclusion, the results will provide a basis for risk assessment, either directly when exposure of consumers to the nanomaterials can be excluded or will be very low or, in the case of evidenced exposure, in combination with then needed toxicological data.
... Nanomaterials are used in consumer products like food packaging articles which require profound knowledge on the potential release of nanomaterials into foods for proper risk assessment. In our previous works, based on comprehensive migration testing using plastics nanocomposites with incorporated silver nanoparticles (Ag-NPs) [1], nanotitanium nitride (TiN) [2], and nanolaponite [3], we could not find any detectable migration and together with theoretical considerations we concluded that migration of nanoparticles from plastic food packaging materials in general is not possible according to Fickian Law of diffusion as long as the particles are larger than 3-4 nm (in case of polyolefins) or 1-2 nm (for PET and similar polymers) in diameter [4] and when the nanomaterial is fully covered with polymer (i.e., does not stick out of the polymer). Since such small nanomaterial sizes are not used in food contact nanocomposites exposure of the consumer due to diffusion-controlled migration of nanomaterials can be excluded. ...
... In a previous study [3] it was demonstrated that AF4/MALLS was suitable for the characterization and quantification of laponite particles dispersed in an aqueous surfactant solution 4 ] −0,7 laponite is mainly composed of ubiquitous elements that do not allow sensitive detection via element-specific ICP-MS measurements, due to an already high background of laponite relevant elements. However, a combination of both techniques (i.e., AF4 with MALLS and ICP-MS as detection system) would allow simultaneous screening for particulate structures with an elemental composition typical for laponite. ...
... Both, theoretical considerations together with experimental empirical findings demonstrate that nanomaterials are immobilized in a polymer matrix and do not migrate based on Fickian law of diffusion [4,5]. Although it is generally accepted that the limiting factor for migration is the size of the migrant and thus nanomaterials are too large to diffuse, some studies reported positive results in migration experiments from nanocomposites that contained silver [8][9][10][11], clays [12][13][14], or titanium-based nanomaterials like titanium dioxide [15]. ...
Three plastic nanocomposites containing the nanomaterials silver, titanium nitride, and laponite were investigated on the potential to release nanoparticulates under stress conditions into food simulants. Nanocomposites were exposed to thermal, chemical, and mechanical stress followed by mechanical abrasion of their surface. Particle sensitive asymmetric flow field-flow fractionation (AF4) with multi-angle laser light scattering (MALLS) as well as inductively coupled plasma mass spectrometry (ICP-MS) detection was used to detect and quantify the respective nanoparticulates. The results of this study demonstrate that even under dynamic stress conditions nanoparticulates are not released from the nanocomposites into food.
... Within the last years the number of studies that investigated the migration potential of different types of NMs has increased and can be found summarized elsewhere [7,25,26]. In some case-examples practical evidence was already given that some NMs cannot migrate and theoretical considerations even showed that NMs used as additives in FCM are too large to migrate in general [26,27]. The use of NMs as additives in FCM made of plastics is regulated within the European Union in regulation EU/10/2011 [28] and its amendments [29][30][31]. ...
... In this study, the migration potential of laponite from nanocomposites based on low-density polyethylene (LDPE) was investigated. Due to its small size compared to other nanoclays, laponite was selected as a model nanomaterial which will represent the worst-case in comparison with all other types of clay materials when considering migration being based on size-dependent Fickian diffusion [27]. ...
... Due to its size with 1 nm in thickness and 25 nm in diameter only, laponite is one of the smallest clay types (in all three dimensions) and NMs (in one dimension) in general. With migration being based on size-dependent Fickian diffusion [27,34,35] lapoAnite can be considered to be a worst-case nano-additive for FCM made of plastics due to expected higher mobility than most other clay NMs. fortified migration sample unfortified migration sample Figure 8. AF4 fractograms from a 6% laponite in LDPE migration solution before and after spiking to 500 ng/mL laponite. ...
In this study, the migration potential of laponite, a small synthetic nanoclay, from nanocomposites into foods was investigated. First, a laponite/ethylene vinyl acetate (EVA) masterbatch was compounded several times and then extruded into thin low-density polyethylene (LDPE) based films. This way, intercalation and partial exfoliation of the smallest type of clay was achieved. Migration of laponite was investigated using Asymmetric Flow Field-Flow Fractionation (AF4) with Multi-Angle Laser Light Scattering (MALLS) detection. A surfactant solution in which laponite dispersion remained stable during migration test conditions was used as alternative food simulant. Sample films with different loadings of laponite were stored for 10 days at 60 °C. No migration of laponite was found at a limit of detection of 22 µg laponite per Kg food. It can be concluded that laponite (representing the worst case for any larger structured type of clay) does not migrate into food once it is incorporated into a polymer matrix.
... For polymers used in FCM, for instance, the general rule is that smaller sized additives migrate faster and at higher rates than those of larger sizes. This is also valid for nanoparticles as migrants in polymer nano-composites according to recent publications Franz and Welle, 2017) on migration modelling of nanoparticles from food contact polymers. ...
... migrating nanomaterials from FCMs). by direct measurements on the nanomaterial in the food matrix, or in the food simulant used in migration testing, or by migration modelling of the nanomaterial in the polymer matrix (Duncan and Pillai, 2014;Noonan et al., 2014;Franz and Welle, 2017;Stormer et al., 2017). ...
The European Food Safety Authority has produced this Guidance on human and animal health aspects (Part 1) of the risk assessment of nanoscience and nanotechnology applications in the food and feed chain. It covers the application areas within EFSA's remit, e.g. novel foods, food contact materials, food/feed additives and pesticides. The Guidance takes account of the new developments that have taken place since publication of the previous Guidance in 2011. Potential future developments are suggested in the scientific literature for nanoencapsulated delivery systems and nanocomposites in applications such as novel foods, food/feed additives, biocides, pesticides and food contact materials. Therefore, the Guidance has taken account of relevant new scientific studies that provide more insights to physicochemical properties, exposure assessment and hazard characterisation of nanomaterials. It specifically elaborates on physicochemical characterisation of nanomaterials in terms of how to establish whether a material is a nanomaterial, the key parameters that should be measured, the methods and techniques that can be used for characterisation of nanomaterials and their determination in complex matrices. It also details the aspects relating to exposure assessment and hazard identification and characterisation. In particular, nanospecific considerations relating to in vivo/in vitro toxicological studies are discussed and a tiered framework for toxicological testing is outlined. It describes in vitro degradation, toxicokinetics, genotoxicity as well as general issues relating to testing of nanomaterials. Depending on the initial tier results, studies may be needed to investigate reproductive and developmental toxicity, immunotoxicity, allergenicity, neurotoxicity, effects on gut microbiome and endocrine activity. The possible use of read-across to fill data gaps as well as the potential use of integrated testing strategies and the knowledge of modes/mechanisms of action are also discussed. The Guidance proposes approaches to risk characterisation and uncertainty analysis, and provides recommendations for further research in this area. © 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.
... Recent studies have indicated that spherical nanoparticles exhibit the most rapid diffusion in polymers, making them the worst-case scenario in terms of migration compared to nonspherical structures. Furthermore, these studies suggested that only nanoparticles with sizes up to 2-4 nm can migrate (Franz & Welle, 2017). ...
... In fact, numerous studies, supported by theoretical considerations and modeling, have shown that NMs >3-5 nm in diameter are not able to diffuse under normal conditions of use, when fully embedded in a polymer matrix (Störmer et al., 2017). Consequently such NMs cannot migrate out from such matrices based on diffusion mechanism (Bott and Franz, 2014;Franz and Welle, 2017). It should be noted that typically NMs in the size range below 5 nm are not used in polymer nanocomposites (Störmer et al., 2017). ...
The widespread integration of engineered nanomaterials into consumer and industrial products creates new challenges and requires innovative approaches in terms of design, testing, reliability, and safety of nanotechnology. The aim of this review article is to give an overview of different product groups in which nanomaterials are present and outline their safety aspects for consumers. Here, release of nanomaterials and related analytical challenges and solutions as well as toxicological considerations, such as dose-metrics, are discussed. Additionally, the utilization of engineered nanomaterials as pharmaceuticals or nutraceuticals to deliver and release cargo molecules is covered. Furthermore, critical pathways for human exposure to nanomaterials, namely inhalation and ingestion, are discussed in the context of risk assessment. Analysis of NMs in food, innovative medicine or food contact materials is discussed. Specific focus is on the presence and release of nanomaterials, including whether nanomaterials can migrate from polymer nanocomposites used in food contact materials. With regard to the toxicology and toxicokinetics of nanomaterials, aspects of dose metrics of inhalation toxicity as well as ingestion toxicology and comparison between in vitro and in vivo conclusions are considered. The definition of dose descriptors to be applied in toxicological testing is emphasized. In relation to potential exposure from different products, opportunities arising from the use of advanced analytical techniques in more unique scenarios such as release of nanomaterials from medical devices such as orthopedic implants are addressed. Alongside higher product performance and complexity, further challenges regarding material characterization and safety, as well as acceptance by the general public are expected.
... In the last two decades, significant advances have been made in migration modelling through the consideration of the underlying physical-chemical processes that occur under single and repeated-use conditions and offers opportunities for more realistic migration and exposure assessments when compared to conventional testing protocols [1][2][3][4][5][6][7][8]. These advances include the prediction of diffusion coefficients D P in the polymers that are used for food contact materials and articles [2,9,10]. ...
Food contact materials (FCMs) can transfer chemicals arising from their manufacture to food before consumption. Regulatory frameworks ensure consumer safety by prescribing methods for the assessment of FCMs that rely on migration testing either into real-life foods or food simulants. Standard migration testing conditions for single-use FCMs are justifiably conservative, employing recognized worst-case contact times and temperatures. For repeated-use FCMs, the third of three consecutive tests using worst-case conditions is taken as a surrogate of the much shorter contact period that often occurs over the service life of these items. Food contact regulations allow for the use of migration modelling for the chemicals in the FCM and for the partitioning that occurs between the FCM and food/simulant during prolonged contact, under which steady-state conditions are favored. This study demonstrates that the steady-state is rarely reached under repeated-use conditions and that partitioning plays a minor role that results in migration essentially being diffusion controlled. Domains of use have been identified within which partitioning does not play a significant role, allowing modelling based upon diffusion parameters to be used. These findings have the potential to advance the modelling of migration from repeated-use articles for the benefit of regulatory guidance and compliance practices.
... To assess the exposure of the consumer to a nanomaterial from FCM, it is essential to determine the actual or potential migration of the nanomaterial from the FCM into the food matrix. This can be achieved by direct measurement of the nanomaterial in the food matrix, in the appropriate food simulant used in migration testing or by migration modelling of the nanomaterial in-and from the polymer matrix (Duncan and Pillai, 2014;Noonan et al., 2014;Franz and Welle, 2017;Stormer et al., 2017). ...
The EFSA has updated the Guidance on risk assessment of the application of nanoscience and nanotechnologies in the food and feed chain, human and animal health. It covers the application areas within EFSA's remit, including novel foods, food contact materials, food/feed additives and pesticides. The updated guidance, now Scientific Committee Guidance on nano risk assessment (SC Guidance on Nano-RA), has taken account of relevant scientific studies that provide insights to physico-chemical properties, exposure assessment and hazard characterisation of nanomaterials and areas of applicability. Together with the accompanying Guidance on Technical requirements for regulated food and feed product applications to establish the presence of small particles including nanoparticles (Guidance on Particle-TR), the SC Guidance on Nano-RA specifically elaborates on physico-chemical characterisation, key parameters that should be measured, methods and techniques that can be used for characterisation of nanomaterials and their determination in complex matrices. The SC Guidance on Nano-RA also details aspects relating to exposure assessment and hazard identification and characterisation. In particular, nanospecific considerations relating to in vitro/in vivo toxicological studies are discussed and a tiered framework for toxicological testing is outlined. Furthermore, in vitro degradation, toxicokinetics, genotoxicity, local and systemic toxicity as well as general issues relating to testing of nanomaterials are described. Depending on the initial tier results, additional studies may be needed to investigate reproductive and developmental toxicity, chronic toxicity and carcinogenicity, immunotoxicity and allergenicity, neurotoxicity, effects on gut microbiome and endocrine activity. The possible use of read-across to fill data gaps as well as the potential use of integrated testing strategies and the knowledge of modes or mechanisms of action are also discussed. The Guidance proposes approaches to risk characterisation and uncertainty analysis.
... While some already address the importance of the size of the material, the risk assessment of NMs requires additional considerations given NMs often exhibit physicochemical properties that are different from those of a material with the same chemical composition but at a different scale. As a general rule, smaller sized particles migrate faster and at higher rates than larger additives (Franz & Welle, 2018). NMs are also typically associated with an increased capacity to translocate over biological membranes (Raftis & Miller, 2019), and with a large surface area, which can be associated with a higher surface reactivity. ...
Background
The use of nanomaterials in the food and feed chain is expected to keep increasing in the years to come. While this brings exciting prospects to both industry and consumers, it also entails important considerations regarding their risk assessment and potential detrimental effects following human exposure. Aiming to standardise the risk assessment of nanomaterials, the European Food Safety Authority (EFSA) has recently published a new guidance where in vitro tests are indicated to play a key role.
Scope and approach
Here, we summarise the latest EFSA guidance aiming to bring it to a wider readership. Recent examples from the literature are critically reviewed regarding their adherence to the recommended methods, thus providing a basis for read-across justifications in future studies. This paper also looks into emerging technologies that may accelerate the development and approval of novel nanomaterials in food while reducing the need of animal studies.
Key findings and conclusions
Few publications cover the extensive list of in vitro studies and parameters recommended by the EFSA. Nevertheless, some address specific sections (e.g. physicochemical characterisation or cytotoxicity) in a very comprehensive manner and we expect this review to contribute towards a better understanding of the importance of following a methodical approach in the risk assessment of novel nanomaterials in food. Lastly, emerging organ-on-chip technologies may arise as impactful tools to run toxicokinetics studies at high-throughput and with significant in vitro-in vivo correlation.
... Besides, the nanoparticle coefficients for conventional polymers used for food (2008) reported a diffusion coefficient of 4.3 × 10 −13 m s −1 for a 1 nmmodel molecule, which is the worst condition for nanoparticle migration and 2.1 × 10 −27 m 2 s −1 at 40 • C for a nanoparticle of 10 nm in LDPE (low density polyethylene), which is the reference polymer with the lowest barrier properties. In the case of PET, a polymer with high barrier properties, the coefficient diffusion is 1.9 × 10 −24 m 2 s −1 for a 1 nm particle and 1 × 10 −49 m 2 s −1 at 40 • C (Franz & Welle, 2018). According to these results, it was possible to establish that nanoparticles can diffuse from polymer matrix inner to the polymer surface at very low rates. ...
Nanotechnology is considered a highly valued technology to reduce the current environmental problem that is derived from plastic accumulation. The need to recycle and reuse packaging materials is essential to create a sustainable society towards a circular economy. However, the reprocessing of polymers leads to the deterioration of their characteristic mechanical, optical, thermal, and barrier properties due to the degradation of their polymeric chains. When recycled polymers are reinforced with nanoadditives, aforementioned properties improve and their use in the circular economy is more viable. In this review, different types of nanoadditives and recent advances in the development of recycled polymer nanocomposites reinforced with nanoadditives will be presented. In addition, there is a description of two research topics of current interest, recyclability of nanocomposites and safety for food packaging applications. Recyclability of nanocomposites requires a study that includes the nature of the polymer matrix, the type of polymer and the concentration of nanofiller, the morphology, the presence of additives, and the conditions of the thermal‐mechanical cycles. Finally, safety section is dedicated to clarify the migration process in nanoreinforced‐recycled polymers in order to assess their safety for food contact applications.
... The inherent complexity of the migration studies on nanocomposites is one reason why risk assessment of NMs still has to be performed on a case-by-case basis [9]. When considering the potential migration of NMs from polymers, it is generally accepted though that NMs are too large to have a significant mobility within a polymer matrix and thus do not have the potential to migrate due to diffusion in the polymer [10,11]. In these studies, supported by migration modelling, a "cut-off diameter" for diffusion of 3-4 nm was derived for NMs incorporated into polyolefins and 1-2 nm in polyethylene terephthalate (PET) or similar polymers. ...
Plastic and rubber based composites containing carbon black (CB) were investigated for the potential to release CB nano-particulates under stress conditions into food simulants. Nanocomposites were exposed to thermal, chemical, and mechanical stress, followed by mechanical abrasion of their surface. Particle sensitive asymmetric flow field-flow fractionation (AF4) with multi angle laser light scattering (MALLS) detection was used to detect and quantify CB nano-particulates. This study demonstrates that, even under dynamic stress conditions, CB nano-particulates are not released from the plastic or rubber compounds into food. This study intends also to propose a general nano-release stress test protocol for plastic materials coming into contact with foodstuff.
... The Panel noted that under these test conditions the maximum use level of 30 lg/dm 2 was not simulated. However, based on published data (Franz and Welle, 2017;Stoermer et al., 2017) on diffusion in and migration from polymers of nanoparticles, migration of SeNPs is not to be expected also at this higher use level. Due to the high conversion rate of selenite into SeNPs (99.87%) and taking inherently low diffusion characteristics of polyolefin polymers for inorganic species into account, also migration of ionic selenium such as residual selenite is not expected. ...
This scientific opinion of the EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF) deals with the safety assessment of selenium nanoparticles, FCM substance No 1070, which is intended to be used as an antioxidant. Selenium nanoparticles are incorporated into the adhesive middle layer of multilayer laminates with an outside polyethylene terephthalate (PET) layer and an inner polyolefin (food contact) layer. The final materials are intended to be used for contact with all food types that are susceptible to oxidation. The specific migration of total selenium was tested using multilayer pouches containing selenium nanoparticles at 0.002 mg/dm ² and filled with 3% acetic acid and 20%, 50% or 95% ethanol for 10 days at 60°C. In all tests, migration of selenium was not detectable. Taking into account current knowledge on the diffusional properties of nanoparticles in polymers, the CEF Panel concluded that there is no safety concern for the consumer if selenium nanoparticles are used in multilayer films and separated from the food by a polyolefin food contact layer for any type of food and under any food contact conditions. © 2018 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.
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