Study finds up to 6000 particles/L to be released from disposable drinking cups; scientists estimate humans ingest 37,613–89,294 microplastics through plastic cups use per year; study suggests consumption from plastic containers changes human gut and oral microbiota composition; review concludes that uptake of microplastics carrying pathogens may impact human health.
Two recent scientific studies assessed human exposure to plastic particles by consumption from disposable drinking cups and another two studies analyzed the potential associated health impact.
In an article published on September 9, 2022, in the journal Science of the Total Environment, Huier Chen and co-authors from China Jiliang University, Hangzhou, China, investigated the release of microplastics from disposable cups under daily use conditions. The scientists purchased 90 disposable cups made of polypropylene (PP), polystyrene (PS), or paper coated with polyethylene (PE) from 51 manufacturers between July 2021 and January 2021, and filled them for 20 min with 10, 40, 70, or 95 °C warm ultrapure water or room temperature warm carbonated drinks and soda water. Subsequently, they analyzed the water for released particles using scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman spectroscopy.
PP, PS, and PE-coated cups released between 781–4951, 838–5215, and 675–5984 particles/L into the 95 °C ultrapure water, respectively. While no difference in MP release was found for the different materials, the researchers reported that higher temperatures and acidic carbonated beverages would enhance microplastic release. Exposing the cups a second time, mimicking reuse, showed that microplastic transfer into water decreased with the use cycle. Chen et al. also assessed the microplastic characteristics. Most particles had a size of 5 to 10 µm and were of irregular shape.
Guanyu Zhou from Sichuan University, China, and co-authors also analyzed the release and estimated the ingestion of microplastics from disposable drinking cups . In their article published on September 13, 2022, in the Journal of Hazardous Materials, the scientists outlined that they analyzed PP, polyethylene terephthalate (PET), and PE cups of 10 brands in Chengdu, China. They filled the cups with deionized water for different periods (1 – 30 min) and kept them at different temperatures (room temperature, 5 °C, 60 °C). One part of the samples was oscillated (60 or 120 rpm) or washed before the experimental procedure. Using SEM and Fourier Transform Infrared spectroscopy (FTIR), the researchers found that plastic cups released between 723 and 1489 particles/cup within 5 min with the majority being smaller than 50 µm. Shaking, higher temperatures, and longer incubation times promoted microplastic release. Based on their results, the authors estimated that drinking from a plastic cup every four to five days leads to the ingestion of between 37,613 and 89,294 microplastics per year. One measure to reduce microplastic contamination is “washing plastic cups before use”, Zhou and co-authors further reported.
How the frequent consumption of food packaged in plastic may affect human health, was analyzed by Hua Zha from Zhejiang University School of Medicine, Hangzhou, China, and co-authors and reported in their article published on September 6, 2022, in the Journal of Hazardous Materials. The scientists recruited 390 students who reported frequently (more than 3-times a week) or occasionally (up to one time per week) or never consuming food from disposable plastic containers. Based on fecal and saliva samples, the human gut and oral microbiota composition were analyzed and differences between the three cohorts were evaluated.
The results demonstrated that occasional and frequent consumption from disposable plastic containers “could cause the alterations of composition, structure and functional pathways of the gut and oral microbiota…which could result in gastrointestinal dysfunction and cough.” The study did not analyze micro- and nanoplastic concentrations in food containers but hypothesized that the observed microbial alterations may be due to plastic particle contaminants in the food chain. That microplastics may affect humans’ gut microbiome has already previously been demonstrated (FPF reported and here).
However, not only the particles themselves may affect human health but also pathogenic bacteria that attach to their surface and end up in foodstuff together with the particles. In an article published on September 6, 2022, in the journal Trends in Food Science & Technology, Raffaella Tavelli and co-authors from Ghent University, Belgium, summarized the current knowledge on microbial food pathogens attaching to microplastics, the impacts of microplastics on the bacteria (e.g., growth, toxin production), as well as the role of microplastic to transport foodborne pathogens into humans. They identified knowledge gaps or inconclusive results concerning attachment of microbial toxins to plastic particles as well as the effect of microplastic on virulence and evolution of microbes. But overall, Tavelli et al. concluded that “biofilm-coated MPs in foodstuffs may pose several risks to food safety, but further research will be essential to determine the extent of their effect on human health.”