Introduction

Microplastic particles (MPs) have previously been confirmed to be found in the human body and are suspected to lead to systemic health effects (1). One biological matrix in which MPs have been detected is human faeces (2). While there is growing evidence suggesting potential impacts on the gut microbiome from animal (3) and in-vitro/ex-vivo studies (4), studies investigating this relationship in the human are still lacking.

Aims & Methods

This pilot study aimed to investigate the impact of short-term plastic reduction on the gastrointestinal tract of healthy participants, focussing on MP presence and gut microbial composition.
Sixty healthy volunteers participated by providing two stool samples: one prior to and one after a seven-day intervention during which they actively minimized plastic exposure. To facilitate the reduction, participants were provided with plastic-free alternatives (e.g., glass water bottles, wooden kitchen utensils, plastic-free dental care products, tin lunch boxes), together with instructions on how to avoid plastic-packaged goods and find alternatives. Dietary habits and plastic contact were recorded using detailed questionnaires to assess behavioural changes and identify potential sources of exposure. Stool samples were analysed using 16S rRNA gene sequencing for changes in microbial diversity and potential differential taxa. Additionally the samples were frozen at –80°C for future MP quantification, where method development is ongoing.

Results

Fifty-five participants completed the study, with an average self-reported success rate of 76% in adhering to the intervention. Forty percent of participants fully avoided plastic packaging, while 56% achieved partial avoidance. Participants noted challenges, particularly in avoiding plastic in meat and dairy products and during restaurant visits. Despite these obstacles, 92.7% expressed a lasting commitment to reducing plastic use post-intervention, with many reporting intentions to continue purchasing fresh products, reduce fast food intake, and adopt sustainable household practices, especially replacing plastic utensils. Initial microbiome analysis revealed no significant changes in alpha or beta diversity following reduced plastic exposure; however, differential abundance analysis identified potential specific taxa shifts. One species each within the genera Clostridium, Ruminococcus, and Blautia showed reduced abundance post-intervention, while species from the genera Bacteroides and Anaerostipes were associated with increased abundance after plastic fasting.

Conclusion

A short-term reduction in plastic exposure is feasible and can effectively raise awareness and promote long-term behavioural change in plastic consumption habits. However, no significant changes in gut microbial diversity were observed within the study period, with only shifts in a limited number of species visible. Due to the stability of the gut microbial composition, longer changes in plastic exposure might be necessary to trigger stronger effects.

References

(1) Prata, J. C., da Costa, J. P., Lopes, I., Duarte, A. C., & Rocha-Santos, T. (2020). Environmental exposure to microplastics: An overview on possible human health effects. The Science of the total environment, 702, 134455. https://doi.org/10.1016/j.scitotenv.2019.134455
(2) Schwabl, P., Köppel, S., Königshofer, P., Bucsics, T., Trauner, M., Reiberger, T., & Liebmann, B. (2019). Detection of Various Microplastics in Human Stool: A Prospective Case Series. Annals of internal medicine, 171(7), 453–457. https://doi.org/10.7326/M19-0618
(3) Hirt, N., & Body-Malapel, M. (2020). Immunotoxicity and intestinal effects of nano- and microplastics: a review of the literature. Particle and fibre toxicology, 17(1), 57. https://doi.org/10.1186/s12989-020-00387-7
(4) Tamargo, A., Molinero, N., Reinosa, J. J., Alcolea-Rodriguez, V., Portela, R., Bañares, M. A., Fernández, J. F., & Moreno-Arribas, M. V. (2022). PET microplastics affect human gut microbiota communities during simulated gastrointestinal digestion, first evidence of plausible polymer biodegradation during human digestion. Scientific reports, 12(1), 528. https://doi.org/10.1038/s41598-021-04489-w