Micro- and nanoplastics are omnipresent in the environment as well as in foods and beverages leading to the direct exposure of humans. The small plastic particles have been analyzed and detected in a wide range of human biological samples, including breastmilk (FPF and placenta, and potential effects are being evaluated. Three recently published research articles investigated the presence of microplastics in humans, analyzing human vein and colon tissues, as well as urine. A review focused on the health implications of this particle presence looking into potential carcinogenic effects.
In an article published on February 1, 2023, in the journal Plos One, Jeanette M. Rotchell and co-authors from the University of Hull and Castle Hill Hospital, Cottingham, UK, reported on the presence of microplastics in the human vein tissue.
The scientists collected saphenous (leg) vein tissues from five patients with a mean age of 72 years undergoing surgery. Upon tissue digestion and filtration, they assessed the number, polymer type, and shape of plastic particles using μFTIR spectroscopy (5 µm size limit). Rotchell and co-authors detected 15 plastic particles/g of tissue after subtracting the corresponding blanks. While “microplastics levels within tissue samples were not significantly higher (p = 0.293) than those identified within combined procedural blanks”, they differed in polymer types. Alkyd resin, polyvinyl propionate/acetate (PVA), and nylon-ethylene-vinyl acetate were most abundant in the tissue. Comparing the levels with those reported for colon and lung, they were found to be similar for the vein tissue.
This is the first scientific evidence that small plastic particles are present in human vascular tissues supporting “the phenomenon of transport of microplastics within human tissues.” The small pilot study serves as a “starting point for more in depth analysis of the levels, types, and clinical implications of such presence.”
Looking into the implications of microplastic presence in the human body, Josefa Domenech from the Finnish Institute of Occupational Health, and co-authors were interested in their potential carcinogenicity. For their review article published on February 2, 2023, in the journal Mutation Research-Reviews in Mutation Research, they screened 126 studies on the topic available on PubMed of which 19 met their inclusion criteria. Another seven eligible studies were identified by cross-referencing. Most of the 26 reviewed studies performed experiments in vitro, while 40 % were performed in rodents.
The scientists summarized that included studies indicate that micro- and nanoplastics can cause DNA damage, and lead to the generation of reactive oxygen species and inflammation. Furthermore, they could induce genotoxicity which is “recognized as a strong predictor of carcinogenicity.” While available studies “may suggest an association between micro- and nanoplastics exposures and the carcinogenic potential,” Domenech and co-authors pointed out that “the limited number of available studies precludes reaching clear conclusions.” Therefore, they provided recommendations for future research to close the knowledge gaps and better understand the carcinogenic risk of microplastics.
In an article published on February 2, 2023, in the journal Environmental Chemistry Letters, Meltem Cetin and co-authors from Ataturk University, Erzurum, Turkey, aimed to widen the knowledge on the connection between microplastics exposure and human cancer. To this aim, they assessed if there is a difference in microplastics’ presence in the colon tissue of individuals with and without colorectal cancer.
Specifically, Cetin et al. analyzed three types of samples (i) tumoral colon tissues and (ii) non-tumoral colon tissue of patients diagnosed with colorectal adenocarcinoma (n = 16), and (iii) colon tissue from individuals without such diagnosis (controls; n = 15). They reported that the number of microplastics was significantly higher in the tumoral colon tissue compared to both types of non-tumoral colon tissue with 702.68 ± 504.26 , 207.78 ± 154.12 , and 218.28 ± 213.05 particles/g colon tissues, respectively. The authors concluded that their “findings suggest a possible connection between colorectal cancer and microplastic exposure.” However, a larger sample size should be investigated to validate their findings.
Concetta Pironti from the University of Salerno, Baronissi, Italy, and co-authors analyzed the presence of microplastics in human urine and their elimination from the human body. In their article published on December 30, 2022, in the journal Toxics, Pironti and co-authors described that they investigated urine samples from six Italians between 16 and 35 years by Raman microspectroscopy. The researchers detected microplastics in four out of the six samples and a total number of seven particles. Microplastics had a size of 4-15 µm, most were of irregular shape and made of polypropylene. The authors highlighted that their results stem from a preliminary study making the evaluation of more samples necessary to validate their findings and “to investigate the pathway of diffusion through the urinary system.”
Cetin, M. et al. (2023). “Higher number of microplastics in tumoral colon tissues from patients with colorectal adenocarcinoma.” Environmental Chemistry Letters. DOI: 10.1007/s10311-022-01560-4
Domenech, J. et al. (2023). “Insights into the potential carcinogenicity of micro- and nano-plastics.” Mutation Research-Reviews in Mutation Research. DOI: 10.1016/j.mrrev.2023.108453
Pironti, C. et al. (2022). “First Evidence of Microplastics in Human Urine, a Preliminary Study of Intake in the Human Body.” Toxics. DOI: 10.3390/toxics11010040
Rotchell, J. M. et al. (2023). “Detection of microplastics in human saphenous vein tissue using μFTIR: A pilot study.” Plos One. DOI: 10.1371/journal . pone.0280594
Peter Dennis (February 2, 2023). “Study: microplastics used in packaging and paint discovered in human veins.” Circular.
This article was originally published by Lisa Zimmermann at the Food Packaging Forum.