The advantageous features of nanomaterials have led to their use in an increasing number of applications across many sectors including the food industry. Common types in food packaging include nanoparticles, nanocomposites (when nanoparticles are integrated into a polymer), and nanosensors (small sensors that monitor food conditions in real time).
A study commissioned by the European Union Observatory for Nanomaterials (EUON) published on October 22, 2024, reviewed the release of nanoparticles from consumer products, including from food contact materials (FCMs), and their potential toxicity. The study defined nanoparticles as particles with all three external dimensions being between 1 and 100 nm.
For their systematic review, the authors searched Web of Science, PubMed, and Scopus for relevant literature on (1) the (eco)toxicity of nanoparticles released from products containing nanomaterials and (2) the characterization of the (nano)particles released. A total of 50 and 203 studies were considered eligible, respectively. Of the release characterization studies, 14% of the 203 were on FCMs.
Concerning FCMs, the report clarifies that nanoparticles, such as silver (Ag), titandioxid, zinc oxide, silanated silica, ferric oxide, and nanoclays, are added to the food packaging to improve gas barrier, antimicrobial, and antioxidant properties, as well as mechanical strength. In 2019, EUON published a database of 240 nanomaterials currently available on the market (FPF reported) which increased to 324 when updated in 2023. Accordingly, the current EUON report finds that applications of nanomaterials in packaging have significantly increased in the past decades, and with that concerns about human exposure and related impacts. For FCMs, the concern pertains to nanoparticles migration into the food, leading to human exposure. While the nano-size and high surface area-to-volume ratio of the particles bring advantages to materials such as resistance, flexibility, or thermal conductivity their small size also has drawbacks, such as the ability to cross biological membranes (FPF reported).
The authors of the EUON report found that the included studies on FCMs assessed nanoparticle release according to regulatory standards, e.g. the regulation on plastic FCMs (EU) No 10/2011, meaning they investigated the migration of nanoparticles from the FCM into food simulants. Annex I of (EU) No 10/2011 includes some nanoparticles, such as zinc oxide, but the majority of the research (59%) included on FCMs investigated migration of Ag nanoparticles, followed by copper. Ag migration was found to be higher: from coated materials than materials with silver embedded into the polymer (FPF reported), for polymers with lower crystallinity, and from heated containers. Changes were also observed between different polymer types. The majority measured Ag in its cationic Ag+ form while only a few measured nanoAg. “The migration and transformation of metallic nanoplastics into cations, particularly under acidic conditions, is significant,” the authors reported. Other conclusion drawn on FCMs were that the migration is “systemic” (occurs from all products) and happens by the “detachment of flakes from the packaging surface and/or the dissolution of nanoparticles from the packaging surfaces, which transform into metal cations.”
Considering all consumer products, the study was not able to conclude the toxicity of the released nanoparticles, e.g., due to the lack of test methods. Together with wood, FCMs are the only consumer product category for which standardized methods for investigating nanoparticle release are available. However, for all consumer product types release can be expected at some point during a products lifecycle, “resulting in significant exposure to humans and/or the environment.” The authors continue, “[i]t should be therefore imperative to consider these factors before incorporating such nanoparticles into articles or products.” Importantly, the original pristine nanoparticles are mostly well characterized but don’t reflect the released nanoparticles which have received little attention.
EUON has also assessed consumer perception of nanotechnology and found low awareness of nanomaterials and a wish for labeling products accordingly (FPF reported). EUON is hosted and maintained by the European Chemicals Agency (ECHA) and funded by the European Commission.
Rakesh Kumar Gupta and co-authors from the Indian Institute of Technology Kharagpur, West Bengal, India, and co-authors reviewed the use of nanomaterials in food packaging, considering their characteristics (size, surface chemistry, dose, and structure), pathways of human exposure, environmental impacts, migration into food and methods for their toxicity assessment. Ultimately, they outlined knowledge gaps and proposed future research topics. Their article was published on September 12, 2024, in the Journal of Hazardous Materials Letters.
Exposure of nanomaterials from food packaging can be via inhalation of fine dust particles or aerosols which can become airborne throughout the lifecycle of the material or upon dermal contact. Furthermore, nanoparticles can migrate from the packaging into the food and this migration is increased under acid conditions. For instance, nanoclay has been found to migrate from low-density polyethylene (LDPE)-nanocomposite bags (FPF reported) and titanium dioxide particles from non-stick quasi-ceramic frying pans (FPF reported). According to Gupta and co-authors the main process of nanoparticle transfer from the packaging in the food is via diffusion. Nanoparticles have also been detected in several types of foods, including infant formula (FPF reported).
Regarding health effects, the review summarizes that in vivo and in vitro studies have connected nanomaterials with oxidative stress, genotoxicity, and inflammatory responses. Nanoparticles have also been linked to affecting intestinal functions (FPF reported), poor digestion (FPF reported), and cancer (FPF reported).
Outlined knowledge gaps include the long-term effects of nanomaterials on human health and behavior of nanomaterials in different types of food. Accordingly, “current guidelines for food safety may not account for the unique properties of nanoparticles.”
Engineered nanomaterials present in food can not only stem from FCMs but have also been used in food directly as additives to improve palatability and appearance or for nutritional purposes (FPF reported and here). In 2021, European Food Safety Authority (EFSA) released guidance documents on the technical requirements for measurement and risk assessment of nanomaterials in the food and feed chain, including migration testing (FPF reported).
References
Grupta, R.K. et al. (2024). “Investigating the toxicological effects of nanomaterials in food packaging associated with human health and the environment.” Journal of Hazardous Materials Letters. DOI: 0.1016/j.hazl.2024.100125
