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

Abstract

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.

Information on CME

This article has been certified by the North Rhine Academy for Continuing Medical Education. The questions on this article may be found (in German) at http://daebl.de/RY95 (Deutsches Ärzteblatt’s CME portal). Their English translation may be found in the PDF version of this article. The closing date for entries is October 2, 2026.

Participation is possible at cme.aerztebatt.de

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 (9–14).

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

The study was based on a random-quota online survey focusing on microplastics (stratification criteria: sex, age, education, federal state) conducted among the German-speaking population (N = 1135, 52 female, age: M = 49.3 years, SD = 16.2). Participants were recruited between March and May 2022 in cooperation with a professional market and social research service provider through its online panel.

• Results

With regard to awareness, nearly 94 of respondents reported that they had already heard of microplastics.

To investigate assumptions about the behavior of microplastics in the human body, respondents were asked to what extent they considered statements on potential effects of microplastics—irrespective of the current scientific evidence—to be true or false (Table). The majority of respondents considered statements on the accumulation of microplastics in the body, the worsening of pre-existing medical conditions, and the blocking of bodily functions to be true. Two-thirds of respondents also considered it to be true that microplastics have an effect on hormone levels.

There were significantly greater levels of concern (Table) about the environment compared to human health.

• Limitations

When interpreting the results, one needs to bear in mind methodological limitations such as potential selection bias in panel samples and limited oversight during study implementation.

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).

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 (9–14). 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, 38–40).

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

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.

Table.

Views on microplastics
In your opinion, are the following statements onmicroplastics true or false?	True			False
Pieces of microplastic in the human body can make tiny cuts in organs (e.g., stomach, heart).	54			46
Microplastics can enter the human body through skin.	55			45
Microplastics in the human body can influence hormone levels.	67			33
Microplastics in the human body can block bodily functions (e.g., blood flow in the arteries).	80			20
The smaller a microplastic particle is, the greater its potential for harm is.	81			19
Microplastics in the human body can worsen pre-existingmedical conditions.	84			16
Microplastics in the human body can accumulate over time and cause harm after a certain concentration is reached.	95			5
Concern about microplastics
Are you personally concerned about the effects ofmicroplastics on [ …]?	Not at all concerned	2	3	4	Veryconcerned	M (SD)
Human health	1	5	22	39	33	3.9 (0.9)
The environment	1	2	10	31	56	4.4 (0.8)

Valid, rounded percentage values are shown.

Views on microplastics: n = 1052–1056; concern about microplastics: n = 1045–1055.

M, mean; SD, standard deviation

Questions on the article in issue 20/2025:

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

The submission deadline is 02.10.2026. Only one answer is possible per question.

Please select the answer that is most appropriate.

Question 1

Microplastics are defined as measuring upwards of 1 µm.

What size is given in the article as the upper limit for microplastics?

1. 50 µm

2. 100 µm

3. 1 mm

4. 5 mm

5. 10 mm

Question 2

The article lists various materials that microplastics can be made of.

Which of the following materials is not among these?

1. Polyvinyl chloride;

2. polycellulose;

3. polyethylene

4. polypropylene;

5. polyester

Question 3

Which statement on the absorption of microplastics across the intestinal barrier is correct?

1. It is unlikely that microplastic particles can be absorbed across the intestinal barrier.

2. According to in-vitro studies, approximately 30 of all particles between 1 and 5 µm are absorbed in the intestine.

3. Animal studies show that almost 90 of microplastics measuring less than 5 µm are absorbed across the intestinal barrier.

4. Microplastic particles do not reach the intestine since they are completely broken down in the stomach by gastric acids.

5. It is unlikely that microplastic particles measuring more than 1.5 µm can be absorbed across the intestinal barrier and distributed.

Question 4

The article refers to a study by Nihart et al., in which microplastics with a mass concentration of up to 4.8 µg/g were measured in human brains. However, there is a discussion as to whether the detected signals were misinterpreted. To what is this likely attributable?

1. Laboratory instruments containing plastic introduced microplastics into the samples.

2. Protein fragments were misinterpreted as microplastics.

3. Fat components from tissue were misinterpreted as microplastics.

4. Sugar molecules from tissue were misinterpreted as microplastics.

5. Crystallized salts from the preparation medium used to process samples were misinterpreted as microplastics.

Question 5

The article presents a survey study on the perception of microplastics (random-quota survey). In the survey, which statement did 95 of participants consider to be true?

1. Pieces of microplastics in the human body can make tiny cuts in organs.

2. The smaller a microplastic particle is, the greater its potential for harm is.

3. Microplastics can enter the human body through skin.

4. Microplastics in the human body can accumulate over time and cause harm after a certain concentration is reached..

5. Microplastics in the body can influence hormone levels.

Question 6

According to the article, what is meant by secondary microplastics?

1. Microplastics that are formed from plastic waste by degradation or fragmentation under environmental influences.

2. Microplastics that are produced specifically for use in cosmetic products.

3. Microplastics that are biodegradable and therefore less harmful to the environment.

4. Microplastics that interfere with tissue sample analysis since they contaminate samples during processing through plastic-containing laboratory materials.

5. Microplastics that are produced for subsequent processing into larger plastic products.

Question 7

The article describes a random-quota survey on the perception of microplastics in Germany. What percentage of participants reported having already heard of microplastics?

1. Approximately 32;

2. approximately 53;

3. approximately 71

4. approximately 82;

5. approximately 94

Question 8

Which statement on the uptake and distribution of microplastics in the human body is most applicable?

1. According to current knowledge, microplastics are primarily taken up directly into the body through the skin.

2. Microplastics have already been detected in the placenta and atherosclerotic plaques.

3. According to current knowledge, microplastics accumulate primarily in muscle tissue.

4. According to a pilot study (Leslie et al.), the measurement results of microplastics in blood are highly reproducible.

5. To date, the highest concentrations of microplastics have been detected in the spleen.

Question 9

As a general rule, how are plastic particles with a diameter of < 1 µm referred to?

1. Picoplastics;

2. microplastics;

3. milliplastics;

4. nanoplastics;

5. femtoplastics

Question 10

Which statement most closely corresponds to the statements made in the general conclusion regarding the potential health risk and measurability of microplastics for consumers?

1. At present, public concern regarding the health effects of microplastics on the human body is lower than current scientific knowledge would warrant.

2. The current state of knowledge suggests that the health risk from microplastics is likely to be low, since their uptake and bioavailability are presumed insufficient to trigger health effects.

3. The current state of knowledge suggests that the health risk from microplastics is relatively high, given that recent studies have demonstrated causal relationships with gastrointestinal and hematological disorders.

4. Newly established analytical methods make it possible, for the first time, to reliably and reproducibly quantify microplastics in various human tissues, including complex tissue.

5. A causal relationship between microplastic uptake and kidney failure has already been demonstrated, and evidence of causal relationships with other diseases is likely to follow.