Microplastics: State of the Evidence on Health Effects and Public Perception

Background: Microplastics, i.e., plastic particles ranging from 1 µm to 5 mm in size, are ubiquitous in the environment. They are to be distinguished from nanoplastics, which are defined as particles less than 1 µm or less than 100 nm in size (depending on the study). Microplastics have increasingly become a topic of discussion in the media. In this article we present the state of scientific and medical knowledge about microplastics and how they are perceived by the public.

Methods: This narrative review is based on pertinent publications retrieved by a search in PubMed and Scopus, supplemented by the findings of a random-quota online survey among the German-speaking population (N = 1135).

Results: Microplastic particles mainly enter the body by being inhaled or swallowed. According to current knowledge, most are excreted without being resorbed, while a small fraction of them could reach the tissues or the bloodstream depending on their size and become systemically bioavailable. Approximately 0.3% of particles measuring 1–10 µm in size are resorbed in the intestinal tract. Microplastics have been found in organs and tissues (e.g., placenta, atherosclerotic plaques), but no causal relation between their uptake and any health effects has yet been proven. Given the limited available evidence on microplastics, some segments of the general population are concerned about their potential effects on human health. In our random-quota survey, 84% of respondents considered the statement that microplastics in the body can worsen pre-existing medical conditions to be true.

Conclusion: Current evidence does not permit any definitive conclusion about the effects of microplastics on health. The information presented here may help physicians counsel their patients on this matter.

Cite this as:Janzik R, Sieg H, Braeuning A, Böl GF: Microplastics: State of the evidence on health effects and public perception. Dtsch Arztebl Int 2025; 122: 546–51. DOI: 10.3238/arztebl.m2025.0138

Microplastics, a mixture of various small plastic particles, are a ubiquitously present environmental contaminant. In most studies, particles ranging in size from 5 mm to 1 µm are classified as microplastics, although there is no universally accepted definition (1). They are distinguished from the even smaller nanoplastics—the size range of which starts from <1 µm or <100 nm—depending on the study. Both types of plastic are also distinct from larger macroplastics, that is to say, plastic waste in the centimeter range that is an environmental contaminant and ecotoxicological problem. Despite 20 years of research, microplastics remain a field of research with a highly complex evidence base, significant data gaps, and ongoing research needs (1, 2).

One reason for this is the lack of clarity as to which materials and forms fall under the definition of microplastics. Here, one often assumes plastics such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and polystyrene (PS), which are used, for example, in food packaging. However, a significant proportion of plastic contamination also comes from elastomers (rubber), synthetic resins, and synthetic fibers such as polyester or polyamide, which are used in road transport as well as materials and textiles manufacturing (3). To date, it has not been feasible to precisely determine the microplastics content in foods and consumer products, owing to the lack of validated quantification methods (4).

It is difficult to assess the health risks posed by microplastics ingested by humans, since it remains unclear to what extent the microplastics absorbed in the body become bioavailable and are able to enter distant organs via blood circulation. It has also not yet been conclusively established whether this has an impact on human health and, if so, what this impact is (5).

At the same time, microplastics are gaining increasing attention in public discourse. They have increasingly become a topic of discussion in the media, with reports often focusing on the results of individual studies (6). A prominent example is the claim that consumers ingest the equivalent of as much as one credit card (5 g) of microplastics per week (for example, [7])—a figure that has since been shown to be a miscalculation. Critical analyses yield figures in the single-digit microgram range, at approximately 4 μg (8). Moreover, people seem to be forming their own views on microplastics. Globally, studies suggest that the general public associates microplastics with health risks (9, 10, 11, 12, 13, 14).

The aim of this review article is to summarize the state of knowledge about the health effects of microplastics and how they are perceived by the public. In addition, the results of an online survey conducted in Germany are presented in order to supplement aspects for which the existing literature has hitherto provided only scant data (Box).

Box

Survey study on the public perception of microplastics in Germany

Methods

This narrative review is based on pertinent English-language publications retrieved by a search in PubMed and Scopus for the period 2014–2024, supplemented by relevant publications known to the authors.

The current state of knowledge on the health effects of microplastics

Sources and ingestion pathways

According to current knowledge, primary microplastics—particles specifically manufactured in the size range between 1 µm and 5 mm (1)—account for approximately 75% of microplastic emissions (3). The largest contribution arises from tire and road abrasion, as well as from losses occurring during waste disposal. Granules released into the environment from plastic production or from sports fields also contribute to total emissions. In contrast, textiles and cosmetic products are of only minor significance in terms of overall exposure. Secondary microplastics—which are formed when plastic waste that is improperly disposed of undergoes degradation under environmental influences such as UV radiation or fragmentation on beaches and in the sea (1)—currently account for around 25% of total emissions (3). Both types of microplastics accumulate in the environment and come into contact with humans via the airborne route or the food chain. The state of knowledge regarding smaller nanoplastics is even more limited, since these particles are hard to detect and little is known about their exposure and effects. Findings on microplastics cannot simply be extrapolated to nanoplastics, given that the latter differ fundamentally from the former—for example, in how they are formed as well as in their structure and surface properties (15).

Microplastics can enter the body via various routes. While plastic particles in the millimeter and micrometer range are unlikely to be taken up through the intact skin barrier (16), microplastic-containing dust may be inhaled, or contaminated food may be ingested. In all cases, uptake depends primarily on particle size (17, 18). It is likely that most inhaled microparticles settle in the nasopharyngeal region or the bronchioles and are subsequently coughed up or swallowed. The smallest particles (< 1 μm) can penetrate deep into the lungs and may potentially be absorbed—at least in animal studies and in-vitro investigations—by the alveoli, from which they can pass into the bloodstream or lymphatic system (17, 16). There is no evidence to date of alveolar uptake of this kind in humans. There have been reports that individuals with high occupational exposure to microplastic-containing dust are at increased risk for various lung diseases, but no causal relationships have been proven as yet (17). Swallowed microplastic particles are able to successfully traverse the gastric juices (19) and come into contact with the intestinal barrier in the small intestine. Here again, potential uptake and transport in the bloodstream depend on size, and only particles < 1.5 µm can become systemically bioavailable, albeit to a small extent (18). As such, the vast majority of particles pass through the intestinal passage and are excreted without being absorbed (20). Based on in-vitro studies with human tissue, it is assumed that approximately 0.3% of all particles measuring between 1 and 10 µm are absorbed in the intestine (20). Alongside toxicological mechanisms of action, the question of systemic bioavailability is another important factor in the assessment of possible health risks. It is also conceivable that smaller particles in both the intestine and lungs are taken up by immune cells capable of transporting plastic particles around the body (21). Injections and medical products may represent another uptake pathway, via which (even larger) microplastic particles can directly enter the bloodstream (22). The possible routes of absorption and distribution of microplastics and nanoplastics in the human body, based on current knowledge, are shown in the Figure.

Figure

Possible pathways of uptake and distribution of micro- and nanoplastics in the human body

Distribution in the body

Recent studies have demonstrated the presence of microplastics in various organs and tissues, including blood (23), atherosclerotic plaques (24), and placental tissue (25). However, the available analytical methods are still subject to significant limitations. There is no universally applicable method for measuring all particle parameters (26), and each method has resolution and detection thresholds (4).

In addition, the more complex the surrounding matrix, the more challenging the detection of microplastics becomes. While particles in water are relatively easy to detect (27), their detection in more complex foods or human tissue poses a greater challenge. A pilot study conducted by Leslie et al. (23), which analyzed microplastics in human blood samples, identified difficulties, for example, in the reproducibility of measurement results. For instance, microplastic contamination levels exceeding 4 µg/mL were measured in the blood of three out of 22 test subjects, but this result could not be reproduced in duplicate measurements. Contamination during sample preparation and measurement artifacts are also possible. For example, a study that reported the release of billions of plastic particles from tea bags has since been called into question, as the signals measured in that study were preparation artifacts—namely, oligomer crystals that formed only during sample preparation (28, 29). A study by Nihart et al. (30) that reported mass concentrations of microplastics of up to 4.8 µg/g in human brains is currently also the subject of critical debate, given that the signals detected from cellular fat components may have been misinterpreted as microplastics (polyethylene) (31). Consequently, at present, there is hardly any reliable information available on the actual distribution of microplastics in the body, but there are frequent calls for more robust testing methods. However, it is considered highly likely that orally ingested microplastics measuring more than 1.5 µm are not absorbed and distributed through the intestinal barrier in the first place (20).

Table

Views on microplastics

Toxicological effect

Although it is now considered certain that humans are exposed to microplastics via food, products, and the environment, our knowledge of the possible health effects remains incomplete (5, 2). No causal relationships have been proven to date between the uptake of microplastics and health effects. However, the available evidence suggests that, under certain conditions, microplastics may affect cellular signaling pathways, enzyme activity, and cell membrane properties. While effects on inflammatory processes and the immune response remain conceivable, none of these mechanisms of action have been confirmed for microplastic particles as yet. Marfella et al. (24) reported a correlation indicating that patients whose atherosclerotic plaques contained microplastics tended to have a more severe disease course compared to those in whose plaques no particles were detected. However, the authors do not prove a causal relationship (causality) between microplastics and measured health impairments in the form of inflammatory markers or a poorer clinical picture. This means that, although microplastic particles were detected in the tissue samples, no mechanistic link between these particles and the disease characteristics could be established. Moreover, toxicological data often stem from in-vitro or animal studies, many of which were conducted under unclear conditions or with extremely high particle concentrations, making them unsuitable for risk assessment purposes (5). For example, an animal study on the distribution of microplastic particles in mice (32) was heavily criticized within the scientific community for methodological weaknesses, including the particle size used in relation to intestinal barrier crossing and the small sample size (33). Studies of this kind cannot be readily extrapolated to the human context. Therefore, particular precision and caution are required in the risk characterization of microplastics. The absence of evidence is not proof of safety; thus, above all, cause-and-effect relationships need to be carefully examined.

Evidence on public understanding and perception of microplastics

Awareness and associations relating to contact

Awareness of and familiarity with a topic are prerequisites for making specific judgments. In the case of topics that are gaining media attention, these target variables may fluctuate over short periods of time. Although microplastics were scarcely known a few years ago (34, 35), recent studies indicate that awareness is increasing. Results from surveys conducted in Germany show awareness rates of approximately 80–90% (9, 12). In other European countries such as Greece (44%) and Slovakia (50%), the rates are comparatively lower (36), while surveys from Asia also indicate lower awareness in that part of the world (for example, 54% in Malaysia [13]).

Beyond mere awareness, studies to date have examined individual views on sources and exposure pathways only in a fragmented manner. Compared to effects and distribution, sources seem to play a more minor role in respondents’ associations regarding microplastics (37). Other findings suggest that people associate microplastics primarily with the environment and the resulting pollution, for example of beaches (34, 38). There is also awareness of their presence in the air and in the food chain (39). An international study found that, after informing respondents of the potential environmental and health consequences, less than 1% considered the statements that microplastics have been found in human food sources and that marine organisms have been shown to consume microplastics to be false (14).

Assumptions about behavior in the human body

Prevailing assumptions about how microplastics behave in the human body have also so far been investigated by previous research only in a fragmented manner. There is uncertainty among respondents regarding the extent to which microplastics are excreted from the human body (13). In line with this, an interview study showed that respondents assume microplastics gradually accumulate in the body and follow a dose–response relationship, whereby increasing amounts cause greater harm over time (39).

Concern about effects

Current research focuses primarily on the evaluation of summarizing views on the potential effects of microplastics. Using various measurement instruments (for example, “concern” versus “worry,” different scale widths), it has now been well documented that the majority of respondents who are aware of the topic are concerned about the impact of microplastics on human health (9, 10, 11, 12, 13, 14). This has been shown not only in European countries such as Germany (12) and Norway (11) but also in other regions like Australia (10) and Malaysia (13). This finding is supported by the results of qualitative interviews and focus groups, which identify risk perception as a key theme in individuals’ understanding of microplastics (34, 38, 39, 40).

Some studies show that concern about the effects of microplastics on the environment is greater than concern about the effects on human health (10, 11, 12).

Other research suggests that concern about the effects of microplastics varies based on individual variables. With regard to the sociodemographic background of respondents, studies show that women (11, 12), older individuals (11, 12), and those with lower educational levels (e1) exhibit greater concern. Furthermore, knowledge of microplastics is positively correlated with the extent of concern (10, e2) and attitudes towards the particles (e3).

This raises the question of the reasons for concern. It is often assumed that the narratives seen in media reporting on microplastics (for example, ingesting an amount of microplastics equivalent to a credit card; see the Introduction) shape public concern. Media content analyses suggest that microplastics are portrayed as a risk (6), and initial survey studies have identified a link between awareness of certain narratives and respondents’ perception of risk (12, e4). However, these results are not particularly reliable, since they are based on self-reports and may be subject to selective recall. Other approaches used to explain this phenomenon include a transfer of the potentially negative attitudes toward (macro)plastics over to microplastics (e5, 39), and the challenge of assessing the effects of particles of this size in complex organisms. Nevertheless, there is little reliable empirical evidence on this to date, meaning that further dedicated research into the conditions under which concern arises is needed.

Conclusion

The current state of knowledge suggests that the risk to consumers from microplastics is relatively low, given that the majority of particles do not become bioavailable, and the overall quantities taken up are likely insufficient to trigger health effects. Research is required in particular into mechanisms of action in order to establish a causal link between particle exposure and possible effects. There is also a need for robust, validated analytical methods capable of reliably quantifying microplastics in biological matrices. At the same time, the public perception of microplastics is characterized by an increasing awareness of the topic, comparatively limited knowledge, and high concern regarding the health effects.

This prevailing discrepancy between the state of knowledge and public perception should be taken into account when communicating on this topic. Physicians can play an important role here as trusted disseminators of information.

Acknowledgments

The authors would like to thank Dr. Natalie Berger and Dr. Severine Koch (BfR), Domagoj Vrbos and Dr. Giorgia Zamariola (EFSA), as well as Prof. Dr. Sabine Pahl and Dr. Mathew White (University of Vienna) for their contributions to the study presented here on the perception of microplastics.

Funding

The supplementary research project (random-quota online survey) mentioned in the manuscript was supported by the framework partnership agreement between the German Federal Institute for Risk Assessment (Bundesinstitut für Risikobewertung, BfR) and the European Food Safety Authority (EFSA) under specific agreement No. 3 of grant GP/EFSA/AMU/2020/02.

Conflict of interest statement
The authors declare that no conflict of interests exists.

Manuscript submitted on 19 December, 2024, revised version accepted on 21 July 2025.

Translated from the original German by Christine Rye.

Corresponding author
Dr. phil. Robin Janzik

References

2. Hartmann NB, Hüffer T, Thompson RC, et al.: Are we speaking the same language? Recommendations for a definition and categorization framework for plastic debris. Environ Sci Technol 2019; 53: 1039–47

3. Thompson RC, Courtene-Jones W, Boucher J, Pahl S, Raubenheimer K, Koelmans AA: Twenty years of microplastics pollution research—what have we learned? Science 2024; 386 (6720): eadl2746

4. Bertling J, Bertling R, Hamann L: Kunststoffe in der Umwelt: Mikro- und Makroplastik. Ursachen, Mengen, Umweltschicksale, Wirkungen, Lösungsansätze, Empfehlungen. Kurzfassung der Konsortialstudie, Fraunhofer-Institut für Umwelt-, Sicherheits- und Energietechnik UMSICHT (Hrsg.), Oberhausen, 2018.

5. Ivleva NP: Chemical analysis of microplastics and nanoplastics: Challenges, advanced methods, and perspectives. Chem Rev 2021; 121: 11886–936

6. Paul MB, Stock V, Cara-Carmona J, et al.: Micro- and nanoplastics—current state of knowledge with the focus on oral uptake and toxicity. Nanoscale Adv 2020; 2: 4350–67

7. Völker C, Kramm J, Wagner M: On the creation of risk: Framing of microplastics risks in science and media. Glob Chall 2020; 4: 1900010

8. Frankfurter Rundschau: Wir essen jede Woche „fast eine Kreditkarte“: Verheerende Ergebnisse in Plastik-Studie. www.fr.de/panorama/freie-radikale-verheerende-ergebnisse-plastik-studie-mikroplastik-darm-oxidativer-stress-92890862.html (last accessed on 27 November 2024).

9. Pletz M: Ingested microplastics: Do humans eat one credit card per week? J Hazard Mater Lett 2022; 3: 100071

10. Bundesinstitut für Risikobewertung (BfR): BfR-Verbrauchermonitor 02|2024. www.bfr.bund.de/cm/350/bfr-verbrauchermonitor-02–2024.pdf (last accessed on 27 November 2024).

11. Borriello A, Massey G, Rose JM: Extending the theory of planned behaviour to investigate the issue of microplastics in the marine environment. Mar Pollut Bull 2022; 179: 113689

12. Felipe-Rodriguez M, Böhm G, Doran R: Who worries about microplastics? The relative importance of personal values and individual risk judgements. PsyEcology 2024; 15: 9–31

13. Kramm J, Steinhoff S, Werschmöller S, Völker B, Völker C: Explaining risk perception of microplastics: Results from a representative survey in Germany. Global Environ Change 2022; 73: 102485

14. Praveena SM: Exploring public awareness, influencing factors and policy implications towards microplastic pollution: Perspectives from Malaysia. Mar Policy 2024; 161: 106042

15. Thiele CJ, Hudson MD: Uncertainty about the risks associated with microplastics among lay and topic-experienced respondents. Sci Rep 2021; 11: 7155

16. Gigault J, El Hadri H, Nguyen B, et al.: Nanoplastics are neither microplastics nor engineered nanoparticles. Nat Nanotechnol 2021; 16: 501–7

17. Facciolà A, Visalli G, Pruiti Ciarello M, Di Pietro A: Newly emerging airborne pollutants: Current knowledge of health impact of micro and nanoplastics. Int J Environ Res Public Health 2021; 18: 2997

18. Borgatta M, Breider F: Inhalation of microplastics—a toxicological complexity. Toxics 2024; 12: 358

19. EFSA Panel on Contaminants in the Food Chain (CONTAM): Presence of microplastics and nanoplastics in food, with particular focus on seafood. EFSA J 2016; 14: e04501

20. Stock V, Böhmert L, Lisicki E, et al.: Uptake and effects of orally ingested polystyrene microplastic particles in vitro and in vivo. Arch Toxicol 2019; 93: 1817–33

21. Wardani I, Hazimah Mohamed Nor N, Wright SL, Kooter IM, Koelmans AA: Nano- and microplastic PBK modeling in the context of human exposure and risk assessment. Environ Int 2024; 186: 108504

22. Persiani E, Cecchettini A, Ceccherini E, Gisone I, Morales MA, Vozzi F: Microplastics: A matter of the heart (and vascular system). Biomedicines 2023; 11: 264

23. Gopinath PM, Parvathi VD, Yoghalakshmi N, et al.: Plastic particles in medicine: A systematic review of exposure and effects to human health. Chemosphere 2022; 303: 135227

24. Leslie HA, van Velzen MJM, Brandsma SH, Vethaak AD, Garcia-Vallejo JJ, Lamoree MH: Discovery and quantification of plastic particle pollution in human blood. Environ Int 2022; 163: 107199

25. Marfella R, Prattichizzo F, Sardu C, et al.: Microplastics and nanoplastics in atheromas and cardiovascular events. N Engl J Med 2024; 390: 900–10

26. Ragusa A, Svelato A, Santacroce C, et al.: Plasticenta: First evidence of microplastics in human placenta. Environ Int 2021; 146: 106274

27. Braun U, Jekel M, Gerdts G, Ivleva NP, Reiber J: Discussion paper within the scope of the research focus Plastics in the Environment— Microplastics analytics: Sampling, preparation and detection methods. bmbf-plastik.de/en/publication/discussion-paper-microplastics-analytics (last accessed on 27 November 2024).

28. Schymanski D, Goldbeck C, Humpf HU, Fürst P: Analysis of microplastics in water by micro-Raman spectroscopy: Release of plastic particles from different packaging into mineral water. Water Res 2018; 129: 154–62

29. Hernandez LM, Xu EG, Larsson HCE, Tahara R, Maisuria VB, Tufenkji N: Plastic teabags release billions of microparticles and nanoparticles into tea. Environ Sci Technol 2019; 53: 12300–10

30. Busse K, Ebner I, Humpf HU, et al.: Comment on “Plastic teabags release billions of microparticles and nanoparticles into tea.” Environ Sci Technol 2020; 54: 14134–5

31. Nihart AJ, Garcia MA, El Hayek E, et al.: Bioaccumulation of microplastics in decedent human brains. Nat Med 2025; 31: 1114–9

32. The Transmitter: ‘Spoonful of plastics in your brain’ paper has duplicated images. Transmitter 2025. www.thetransmitter.org/publishing/spoonful-of-plastics-in-your-brain-paper-has-duplicated-images/ (last accessed on 10 June 2025).

33. Deng Y, Zhang Y, Lemos B, Ren H: Tissue accumulation of microplastics in mice and biomarker responses suggest widespread health risks of exposure. Sci Rep 2017; 7: 46687

34. Braeuning A: Uptake of microplastics and related health effects: A critical discussion of Deng et al., Scientific reports 7: 46687, 2017. Arch Toxicol 2019; 93: 219–20

35. Anderson AG, Grose J, Pahl S, Thompson RC, Wyles KJ: Microplastics in personal care products: Exploring perceptions of environmentalists, beauticians and students. Mar Pollut Bull 2016; 113: 454–60

36. Catarino AI, Kramm J, Völker C, Henry TB, Everaert G: Risk posed by microplastics: Scientific evidence and public perception. Curr Opin Green Sustain Chem 2021; 29: 100467

37. European Food Safety Authority (EFSA): Special Eurobarometer – March 2022: Food safety in the EU. EFSA 2022. DOI: 10.2805/729388.

38. Felipe-Rodriguez M, Böhm G, Doran R: What does the public think about microplastics? Insights from an empirical analysis of mental models elicited through free associations. Front Psychol 2022; 13: 920454

39. Henderson L, Green C: Making sense of microplastics? Public understandings of plastic pollution. Mar Pollut Bull 2020; 152: 110908

40. Janzik R, Koch S, Zamariola G, et al.: Exploring public risk perceptions of microplastics: Findings from a cross-national qualitative interview study among German and Italian citizens. Risk Anal 2024; 44: 521–35

41. Raab P, Bogner FX: Conceptions of university students on microplastics in Germany. PLoS One 2021; 16: e0257734

e1. Deng L, Cai L, Sun F, Li G, Che Y: Public attitudes towards microplastics: Perceptions, behaviors and policy implications. Resour Conserv Recycl 2020; 163: 105096

e2. Yoon A, Jeong D, Chon J: The impact of the risk perception of ocean microplastics on tourists’ pro-environmental behavior intention. Sci Total Environ 2021; 774: 144782

e3. Deng L, Li G, Peng S, Wu J, Che Y: Microplastics in personal care products: Exploring public intention of usage by extending the theory of planned behaviour. Sci Total Environ 2022; 848: 157782

e4. Pop V, Ozunu A, Petrescu DC, Stan AD, Petrescu-Mag RM: The influence of media narratives on microplastics risk perception. PeerJ 2023; 11: e16338

e5. Heidbreder LM, Bablok I, Drews S, Menzel C: Tackling the plastic problem: A review on perceptions, behaviors, and interventions. Sci Total Environ 2019; 668: 1077–93