Research has shown the widespread presence of microplastics in food including fish, seafood, salts, honey, beer, and bottled water, and its origin from food contact articles is being increasingly investigated. Seven research studies and one book volume published between January and mid-March 2023, on microplastics in food provide more evidence of that connection. A separate review has also assessed the data quality of studies on plastic particles in food and proposed a protocol for that purpose.
In an article published on January 6, 2023, in the journal Environmental Science and Pollution Research, Jianqiang Zhu from Taizhou University, Zhejiang, China, and co-authors analyzed microplastics released from 354 food containers made of polystyrene (PS) into water after incubation for 30 min at 95 °C. They collected samples from different restaurants in 28 Chinese cities. The scientists detected between five and 173 plastic particles per sample. The majority of microplastics resembled the containers in composition, indicating that they “were released from their inner surface.” However, 58% of the particles were made of other polymer types demonstrating that food packaging is not the only source of microplastic contamination in foods.
Based on the wide range of colors and polymer types, Pouran Makhdoumi from Kermanshah University of Medical Sciences, Iran, and co-authors, assumed microplastics present in table salts and sugars to originate from different sources, including packaging. In their article published on March 3, 2023, in the Journal of Food Composition and Analysis, they described that they analyzed packaged tables salts and sugars from four common Iranian brands. Using visual analysis (stereoscope) they identified an average of 55 particles/kg salt and 58 particles/kg sugar, while the respective amounts by Nile Red staining and fluorescence microscopy were 151 and 226 particles/kg. This shows that the type of analytical technique strongly affects the detected and reported particle number. Previous research found microplastics in 90% of tested salt brands worldwide.
In an article published on January 18, 2023, in the journal PeerJ, Sedat Gündoğdu and Ali Riza Köşker from Cukurova University, Adana, Turkey, analyzed microplastics in 33 brands of canned fish available on the Turkish market. They verified a total of 64 particles to be made out of plastic and at least one plastic particle in each sample. The average abundance was four particles per 100 g canned fish. Based on the identified polymer types (polyolefins being the most common), the scientists reported: “packaging and the production processes are the main possible sources of microplastics.” They also called for legislative limits on microplastics in seafood processing.
Water purification before packaging as a source of microplastics in bottled water was suggested in an article published on January 10, 2023, in the journal Science of the Total Environment, by Huan Li from the Chinese Research Academy of Environmental Sciences, Beijing, China, and co-authors. The researchers compared the levels of microplastics in three glass-bottled waters, seven polyethylene terephthalate (PET)-bottled waters, and tap water in which detected an average of 88, 66, and 50 particles (10-500 µm in size)/L, respectively. Since particles were more abundant in bottled water and mainly made of cellulose (68%), the authors think that microplastics are predominantly released “during extensive purification processes, especially from cellulose filter membranes.” Filter and membranes to remove contaminants from water, such as dyes and heavy metals, are commonly made of cellulose.
In an article published on March 10, 2023, in the Journal of Environmental Management, Abdullah Altunışık from the University of Recep Tayyip Erdoğan, Rize, Turkey, also assessed the microplastic levels in beverages across 30 soft drinks from ten brands in Turkey that were either packaged in PET or in Tetra Pak. They detected microplastics in all samples in amounts between five and fifteen plastic particles per L. On average, concentrations were higher in PET packaged samples (10 particles/L) compare to Tetra Pak packaged samples (7 particles/L). The researchers “determined that bottle-production processes and the substrates used for food production may be the main sources of these microplastics.” The authors explain the lower particle levels in the drinks in Tetra Pak (which also contains plastic) by the “difference in the processing of such packaging.”
Arianna Crosta and colleagues from the University of Milan, Italy, evaluated the microplastic presence in eleven soft drinks and three cold teas packaged in PET bottles with polyethylene (PE) caps available in Italian supermarkets. Their article was published on February 25, 2023, in the International Journal of Environmental Research and Public Health. They detected an average of ten and seven plastic particles/L soft drinks and cold tea, respectively. The authors concluded that microplastics “can originate from different sources, including water used in beverage production or washing procedures in the plants, contamination of the working area, and airborne contamination.”
In an article published on February 1, 2023, in the journal Environmental Pollution, Liping Liu from Xi’an Jiaotong University, China, and co-authors assessed the release of microplastics from six types of single-use breastmilk storage bags made of PE and PET during simulated use (ultrapure water with 100 g sodium dodecyl sulfate/L, 12 h, room temperature). Most released particles were made of PE, followed by PET, and nylon-6, with an average particle weight between 0.22 and 0.47 mg/storage bag. The scientists also calculated potential infant exposure to microplastics, which was found to be 0.61 to 0.89 mg/day when exclusively fed with breastmilk stored in these bags. Microplastic presence has been demonstrated in breast milk itself, and breastfeeding was assumed to be a source of microplastic exposure to lactating infants.
In a volume of Advances in Food and Nutrition Research edited by Fatih Özogul from Cukurova University, Adana, Turkey, available online since February 28, 2023, the authors summarize the current knowledge on micro- and nanoplastics toxicity in food quality and food safety research in ten chapters. Chapter 2 looks at the plastic particle occurrence in differently packaged food and also outlines regulation, migrations, and how food and packaging types may influence contamination. Chapter 8 focuses on the migration of microplastics from plastic food packaging into food, factors influencing migration, and measures to reduce it as well as potential human health impacts. Chapter 9 summarizes the effects on human health by taking a closer look not only at the occurrence in the food chain but also at the intake and accumulation of small plastic particles in the human body. According to Özogul, the published volume is targeted not only to the researcher in the areas of food engineering, processing, and packaging as well as food safety, quality, and control but also to the general public interested in the topic.
At present, even the most widely used methods for the detection and identification of micro- and nanoplastics in food are still far from validation and standardization. This is one reason why the reliability of such data is unclear. In an article published on March 1, 2023, in Frontiers of Environmental Science & Engineering, Lihua Pang from Ocean University of China, Qingdao, China, and co-authors evaluated the data quality of studies analyzing micro- and nanoplastics in food according to 10 criteria that they developed. They also propose to use the criteria as a preliminary framework for standardization and a protocol for quality assurance/control. To this aim, the authors searched Web of Science, PubMed, ScienceDirect, Springer, American Chemical Society, and Taylor & Francis for studies on the presence of plastic particles in food published before May 2022. For 71 data records from 63 eligible publications, they summarized the information on the method to identify the plastic polymers and the characteristics of the micro- and nanoplastics, including abundance, size, and shape.
Only three data records were found to be reliable (with or without restriction), meaning that 96% were considered not reliable for at least one of the criteria. “The reliability of the data was mainly restrained by the insufficient sample size, unspecified storage conditions of samples, and a lack of positive controls [58 records] and polymer identification [12 records].” The researchers further identified that the plastic particles identified in foodstuffs have different characteristics than those used in toxicological studies. Therefore, the outcomes of effect studies may not reflect the actual human health hazards caused by microplastics present in food. They call for more research on micro- and nanoplastic occurrence in a wider variety of foods to get a better picture of the plastic particles humans are actually exposed to and to reduce the uncertainty of health risk assessments.
The data quality assessment criteria the authors proposed can be grouped into (i) sampling (e.g., sample size and storage), (ii) contamination mitigation (e.g., clean materials and air condition, negative controls), (iii) sample purification/handling (e.g., sample treatment, positive controls), and (iv) particle characterization (e.g., polymer identification, quantity, size, shape). Pang and co-authors emphasized that their data quality criteria need future revision e.g. when improved analytical methods for the evaluation of micro- and nanoplastics in food products have been developed (which are still lacking but essential).
Altunışık, A. (2023). “Prevalence of microplastics in commercially sold soft drinks and human risk assessment.” Journal of Environmental Management. DOI: 10.1016/j.jenvman.2023.117720
Crosta, A. et al. (2023). “Microplastics Contamination in Nonalcoholic Beverages from the Italian Market.” International Journal of Environmental Research and Public Health. DOI: 10.3390/ijerph20054122
Gündoğdu, S. and Köşker, A.R. (2023). “Microplastic contamination in canned fish sold in Türkiye.” PeerJ. DOI: 10.7717/peerj.14627
Li, H. et al. (2023). “Occurrence of microplastics in commercially sold bottled water.” Science of the Total Environment. DOI: 10.1016/j.scitotenv.2023.161553
Liu, L. et al. (2023). “Release of microplastics from breastmilk storage bags and assessment of intake by infants: A preliminary study.” Environmental Pollution. DOI: 10.1016/j.envpol.2023.121197
Makhdoumi, P. et al. (2023). “Microplastic pollution in table salt and sugar: occurrence, qualification and quantification and risk assessment.” Journal of Food Composition and Analysis. DOI: 10.1016/j.jfca.2023.105261
Özogul, F. (2023). “Nano/micro-Plastics Toxicity on Food Quality and Food Safety.” Advances in Food and Nutrition Research. Volume 103
Pang, L. et al. (2023). “Data quality assessment for studies investigating microplastics and nanoplastics in food products: Are current data reliable?” Frontiers of Environmental Science & Engineering. DOI: 10.1007/s11783-023-1694-0
Zhu, J. et al. (2023). “Microplastics in polystyrene-made food containers from China: abundance, shape, size, and human intake.” Environmental Science and Pollution Research. DOI: 10.1007/s11356-022-25093-z
This article was originally published by Lisa Zimmermann at the Food Packaging Forum.