Microplastics in Tap Water: What We Know and What a Faucet Filter Would Need to Prove
Microplastics in tap water cannot be answered with a single figure, because the term covers a whole spectrum of particle sizes and studies on the subject have so far used different methods. Based on the current, limited state of knowledge, the World Health Organization (WHO) considers the risk low; German water suppliers report very low or undetectable levels in their own networks; and at the same time, the WHO itself acknowledges that there is not yet a standardized measurement method. Anyone buying a faucet filter that advertises “microplastics” should therefore know which particle size is meant, which method was used for testing, and how old the cartridge was at the time of the test, because these three details determine whether a claim proves anything at all.
- “Microplastics” does not refer to a single particle size, but to a range of about 0.1 to 100 micrometers, and the pore size of the analytical method used often also affects the measurement result.
- The WHO and individual German water suppliers currently take a cautiously reassuring view, each with its own caveats about the available data.
- Reliable detection methods and filtration studies for very small particles are still lacking.
- The Hydrion faucet filter’s product page makes no claim about microplastics; it describes particle filtration and an effect on chlorine taste and odor.
What the term “microplastics” covers—and why particle size makes a difference
The term “microplastics” sounds like a single, clearly defined substance, but in practice it covers a broad range of sizes. Berliner Wasserbetriebe classifies plastic particles into three size categories: mesoplastics comprise particles from 0.1 to 5 millimeters, microplastics range from about 0.1 to 100 micrometers, and below that, in the range of 1 to 100 nanometers, comes the category of nanoparticles (Berliner Wasserbetriebe). This classification is more than a matter of definition, because it determines what was actually measured in two claims about the subject.
Particle size is central to the health question because the body absorbs larger and smaller particles differently. The WHO states that particles larger than about 150 micrometers are very unlikely to be absorbed by the human body, while the data on the absorption of smaller particles is much thinner. This least-researched lower range is also where detection and filtration are most difficult, a connection that shapes the rest of this article.
The same principle applies to measurement: an analytical method based on a particular filter pore size cannot, in principle, detect particles smaller than that pore size, regardless of how many are actually present in the water. A result of “no microplastics found” therefore says something about the method used before it says anything about the water itself.
What German water suppliers and the WHO say about microplastics in drinking water
In 2019, the WHO concluded in its most comprehensive summary of the available data to date that, based on the current, limited state of knowledge, microplastics in drinking water do not appear to pose a health risk, while explicitly calling for more research (WHO, 2019). This assessment is therefore not an unqualified all-clear, but a provisional evaluation based on what has been measurable so far.
Berliner Wasserbetriebe go a step further for their own network: Berlin’s drinking water comes from deep groundwater that passes through at least 30 meters of soil, a layer that, according to the supplier, retains undissolved particles, including microplastics. On this basis, the supplier describes Berlin’s drinking water as free of microplastics. This is a statement about a specific catchment area and its geological filter, not about tap water in Germany in general.
Gelsenwasser reports that in its own 2018 study at the Haltern waterworks, measured microplastic concentrations were within the range of the analytical blank values—that is, at the limit of what the method could still distinguish from background noise (Gelsenwasser). Three different sources, three slightly different claims, and all three are accurate in their own right as long as they are not generalized into a single, universal conclusion.
Why two study results on microplastics in water are rarely directly comparable
The WHO itself identifies the development of standardized measurement methods as a research priority, which implies that such a standard is still lacking across studies. Without a common method, a direct comparison of two figures from two studies must be treated with caution, even if both were conducted rigorously.
The Science Media Center asked experts about this, and they described the current state as follows: reliable detection of particles smaller than about one micrometer is not yet considered established; robust filtration studies focus on particles larger than around 50 micrometers; and, according to the researchers surveyed, there are no filtration studies at all yet for particles smaller than 10 micrometers (Science Media Center). This aligns with the size range discussed in the first section: the smallest, least-researched particles are precisely those whose behavior in the body and in filters is least understood.
For comparison: for large-scale technical facilities such as wastewater treatment, the WHO assumes that an additional, third treatment stage with filtration can retain more than 90 percent of microplastics. This figure comes from a completely different context—large, multi-stage wastewater treatment plants rather than a single faucet cartridge—and cannot simply be applied to a compact household device. It does, however, show that particle size remains the key technical parameter here, too.
What a faucet filter can do mechanically—and what the Hydrion filter’s product page actually says
A particle filter basically retains anything larger than its smallest effective pore size and lets through anything smaller. These two variables—the pore size and the method used to test performance—ultimately determine the value of a filter claim, as described in the previous section.
The product page for the Hydrion Keramik- und Aktivkohle-Wasserhahnfilter describes a replaceable cartridge that combines a porous ceramic layer with activated carbon. It describes the ceramic layer as responsible for particle filtration, while the activated carbon is intended to improve the taste and odor of chlorine in already-treated tap water. The product page does not specify a pore size or a tested particle-size range.
Why a manufacturer’s claim alone does not count as proof
A phrase like “particle filtration” describes how something works, not a verified performance limit. Without details about pore size, test method, and cartridge age at the time of testing, no reliable claim about microplastics can be derived from it. The Hydrion filter’s product page does not mention microplastics at all and positions the device for taste, odor, and sediment in already-treated tap water, not as a tested or certified solution for a specific contaminant class.
Other key specifications listed on the product page include a nominal flow rate of 1.2 liters per minute; a compact housing mounted directly on the faucet, with a manual selector and no power connection; and a cartridge lifespan of around six months as a guideline, which may vary depending on water quality and usage. To find out whether activated carbon changes a TDS reading, see the article on what TDS in water means: activated carbon affects taste, odor, and certain organic substances, not the dissolved minerals that make up the TDS value.
Three questions every filter advertisement about microplastics should answer
The previous sections provide the basis for a short, reusable checklist. Anyone reading an advertising claim about microplastics and a water filter can assess it by asking three questions.
| Question | What a real answer indicates | What a missing or vague answer indicates |
|---|---|---|
| What particle-size range was actually tested? | A specific range in micrometers, ideally stating whether it included the difficult-to-detect range below about 10 micrometers. | Only the word “microplastics” with no figure at all, or a range covering only the larger, easily filtered particles. |
| What measurement method was used? | A named, verifiable analytical method, ideally with a reference to a testing laboratory or standard. | No method at all, or merely a reference to “in-house tests” without further details. |
| How old was the cartridge at the time of testing? | Information about the cartridge’s age, since a new cartridge and one that is nearly used up can perform very differently. | Any omission of this information, leaving it unclear whether the result applies to the entire service life. |
As an exercise, it is worth checking any filter advertisement that mentions microplastics against this table, line by line. A claim like “removes microplastics” can only be assessed if it includes the particle-size range, the method, and the cartridge age; if any of these three details is missing, it remains unclear exactly what was tested, no matter how plausible the claim may sound.
How to assess the information—and what comes next
In summary: the WHO and individual German water suppliers currently tend to consider microplastics safe, each with its own caveats about the available data, and the gaps in detecting and filtering the smallest particles mean this assessment could still change as better methods become available. This is not a contradiction, but the normal state of a research question whose methods still need to catch up with the question itself.
The Hydrion faucet filter with a ceramic and activated carbon cartridge is described on its own product page for everyday use: taste, odor, and sediment in already-treated tap water, with a nominal flow rate of 1.2 liters per minute and a cartridge that, according to the manufacturer, lasts around six months. Anyone interested in it should weigh these stated features against their own needs, rather than expect a microplastics solution that the product page itself does not claim to offer.
Anyone looking for a broader perspective on contaminants can find it in the overview of contaminants in European tap water, while those more concerned about dissolved residues such as pesticides can find a deeper dive in the article on pesticide residues in tap water. Anyone considering a solution for the whole house rather than a single faucet can find the relevant considerations in the guide to whole-house water filtration.