Communication 026/2024
19 June 2024

Do microplastic particles increase the risk for astroke?
The BfR has assessed a study on micro- andnanoplastics in deposits (plaque) in blood vessels.
An Italian research group detected micro- and nanoplastic particles (MNP) in theplaque in blood vessels (Marfella et al. [New England Magazine, 2024 Mar
7;390(10):900-910; doi: 10.1056/NEJMoa2309822]). Plaque samples from patients’
inner carotid arteries that showed a narrowing of the blood vessels wereinvestigated. These vessels supply the brain with blood. The plaque samples wereinvestigated for the presence of MNP. The material type and amount of thedetected particles were identified in the next step.
Based on the investigations, the patients were divided into two groups dependingon whether MNP were detectable in the plaque or not. These two groups ofpeople were examined for differences in regard to various physiological andmolecular-biological aspects. Around three years after the samples were taken, afollow-up investigation took place which focused on whether and how many of thepatients had died from a heart attack or stroke in this time period. The groupwhose plaque contained MNP fundamentally showed more pronounced diseaseprogression (more heart attacks and strokes, including fatal ones, as well as higherinflammation parameters) than the group in which no MNP was found.
However, the study only describes correlations and no causation, i.e., a simple linkis made between the presence of MNP in the plaque of the vessels and thediseases of the patients. It is not clarified as to whether the identified polyethylene(PE) and polyvinylchloride (PVC) particles cause plaque formation andinflammation of the vessel walls. Whether and how MNPs contribute to plaqueformation is also not addressed. Furthermore, the study makes no statements
regarding how the MNP enter the blood or the deposits.
The German Federal Institute for Risk Assessment (BfR) thus concludes that while
the study describes a link, it does not show causality and does not contribute any
evidence that MNP increases the risk for vessel diseases and resulting heart© BfR | bfr.bund.de/en | 1 / 5

attacks or strokes. In addition some scientific questions were identified which
require closer scrutiny.

Assessment of the studyThe basics
To the extent that this can be derived from the published material, the BfR is of the opinion
that the study appears to have been well planned, implemented and analysed. The reporting
followed the STROBE guidelines (https://www.strobe-statement.org/). Limitations werenoted and discussed in the text. The study is primarily relevant for older people. It could bethat some confounders were not considered during the analysis, which was also addressedby the authors. It is thus possible for expert readers to categorise the results and draw
conclusions. One aspect deserving of criticism is that a comparatively sweeping statement isoften initially made, with the relativisation and classification only becoming clear after
closer reading. This potentially makes it difficult for people who are not at all or only
cursorily versed in the scientific field to understand and interpret the study.
Design of the study
Plaque samples from people with circulatory diseases were investigated in the study. In allcases, therefore, the study involves patients (i.e., ill people, even if asymptomatic). There is
not a “healthy” control group without plaque. It was a blind study, which can be considered
positive, and the study-related limitations are clearly stated. Diseases were registered withina certain limited observational period.
The assignment of patients to one of the two groups took place depending on whether MNP
was present in the deposits (plaque) in blood vessels. This does not necessarily mean,
however, that people in which no MNP was detected actually had no particles at all in theirplaque.
The study is an observational study and creates correlations between MNP and effects. Thismeans that the study does not describe any causal context, which is also clearly stated.
Sometimes, the authors attempt to calculate incidences from the available data.
Analytics and particle quantification
There is no universal analytical process for detecting MNP in tissues which is internationallyscientifically recognised. The selected destructive processes are suitable for quantifying
partial elements of MNP but do not provide information about the MNP’s size and nature. In
contrast, spectroscopic processes do permit assertions regarding distribution andlocalisation, but they do not deliver a quantitative statement. The present study attempted
to work with a combination of the best measurement methods currently available. A process
was selected which is in alignment with current scientific knowledge. This also involves theevaluation of the raw data obtained.
Since every selected analytical method was checked by a second, independent process, it islikely that MNP was correctly identified during the study. The different measurable and non-© BfR | microplastic particles | Communication issued 19 June 2024

2/5measurable size ranges were stated and explained. It was likewise clearly stated thatcontaminations (e.g., from the air, during sample preparations) cannot be ruled out.
Direct correlation of the results from qualitative and quantitative analysis methods for MNP
is not possible in this type of study. It would, however, have been desirable for there to havebeen a classification of whether the qualitative and quantitative results of the analysis
plausibly suit each other. This only took place in part.
Interpretation of the results and correlation with health parameters
The presence and accumulation of plastics in fat-rich structures of the body such as arterial
plaque appears to be possible in pathophysiological terms. A causal context, i.e. that forinstance the presence of MNP has an influence on plaque formation or the occurrence of
cardiovascular diseases, cannot be established with the study. Mechanisms of action ormolecular events that are required for plaque to form are not the object of the study. The
study does not permit any assertions regarding possible MNP sources and routes ofexposure. It is possible there are different confounders that could have influenced theresults of the study.
Open questions requiring closer scrutiny
Several important scientific questions were not addressed by the study and require closer
consideration. Plaque was examined for a number of different materials. All the examinedplastic materials are most likely to be MNP. It remains unclear why only two materials(polyethylene and polyvinyl chloride) could be detected as usually a number of different
polymers are found when it comes to MNP particles. Further, the limits of quantification of
the used analysis methods remain undefined. A possible interpretation is that the MNP does
not come from everyday contamination sources close to the consumer, and instead there
was an exposure connected to a medical treatment, e.g., via injections or infusions. Thispossibility was, however, not mentioned in the study. The following points to such a cause:
the age of the patient population, the fact that the detected polymers are those most usedin medical applications, and that the detected particles are currently too large for it to be
likely that they entered via plausible transport mechanisms via other body barriers(specifically intestine, lungs). Moreover, it seems very questionable that such a commonlyoccurring contaminant such as microplastic (to which likely all test persons were exposed insome way) could not be detected in the plaque of all test persons. It seems possible thatMNP, provided it is systemically bioavailable, is absorbed by immune system cells which arespecialised in fighting structures foreign to the body. The patients with a worse prognosis
also showed overwhelmingly more inflammation in the plaque, i.e., an increased migrationof immune cells into the investigated areas. MNP, then, could enter the plaque via theimmune cells that infiltrate these areas when inflamed and bring MNP with them. The
negative correlation between the detected MNP and the amount of collagen is striking. A
mechanistic investigation of the causes underlying this would be useful.
Furthermore, there is a significant need for development and validation in regard to theanalytical methods used. A larger body of reliable reference materials would be helpful.
Using standard addition methods it would, in principle, be possible to further improve
instrumental-analytical processes.
Plausibility of microplastics exposure via various exposure pathways© BfR | microplastic particles | Communication issued 19 June 2024

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Fundamentally, the mere detection of microplastics does not allow for specific assertions
regarding possible exposure routes into the body. In the case of the patients in the above
study, exposure via products used in intensive medicine (e.g., infusion cannulas, catheters)
appears conceivable and plausible. The study involves patients who already have a long
history of illness. Therefore plastic particles, particularly PE and PVC, could directly enter thebloodstream via a corresponding vascular puncture.
The presence of microplastics in food has been shown in a number of studies. An intake ofMNP via food is thus, in principle, conceivable. Particle size is the biggest factor for theMNP’s entrance through the intestinal barrier. This also corresponds to the assessment of
the European Food Safety Authority (EFSA) from 2016 which states that the transport ofplastic particles via the intestine is predominately dependent on their size. Particles bigger
than 1.5 micrometres (µm) cannot pass the intestinal barrier, meaning they are notsystemically bioavailable (CONTAM-Panel 2016,
https://www.efsa.europa.eu/de/efsajournal/pub/4501). This also corresponds to the latest
scientific knowledge.

Further information about microplastics on the BfR website
Questions and answers on microplastics: Facts, research, and open questions
https://www.bfr.bund.de/en/microplastics__facts__research_and_open_questions-192775.html
BfR overview of microplastics
https://www.bfr.bund.de/de/a-z_index/mikroplastik-192184.html#fragment-2© BfR | microplastic particles | Communication issued 19 June 2024

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About the BfR
The German Federal Institute for Risk Assessment (BfR) is a scientificallyindependent institution within the portfolio of the Federal Ministry of Food andAgriculture (BMEL) in Germany. The BfR advises the Federal Government and theStates (‘Laender’) on questions of food, chemicals and product safety. The BfR
conducts independent research on topics that are closely linked to its
assessment tasks.

This text version is a translation of the original German text which is the only legally binding version.
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