Chemically identified microplastics have been reported in drinking-water distribution systems. The amount that can be distinguished from laboratory contamination depends on the sampling and identification method. Reviewed studies from Sweden and Denmark illustrate both findings and limits: a blank-corrected distribution-system measurement and a study in which larger particle observations could not be separated from background contamination.12
What this page covers
Tap water means drinking water sampled from a public supply or a connected distribution point. It is not the same sample as river water, wastewater, bottled water, or water deliberately spiked with plastic for a detection-method experiment. The studies below were selected for their explicit chemical identification and quality-control reporting. This is a selected literature synthesis, not an exhaustive survey of every public water supply.
What the studies found
Kirstein and colleagues followed a Swedish waterworks and connected distribution pipes. They analyzed particle counts by infrared imaging and polymer mass by a separate thermal method. Their count result was corrected with station-specific blanks. Feld and colleagues used a closed tap-sampling system in Denmark, screened larger objects visually, and checked selected objects chemically.12
Scroll horizontally for methods and limitations.
| Study and endpoint | Reported result | Size context | Interpretation |
|---|---|---|---|
| Swedish distribution-system count | 174 ± 405 MPs/m³ | 8 to 374 µm | Blank-corrected system average, with variable station results. |
| Danish larger-object identity check | four of 124 selected objects | Larger visually selected objects | Most examined objects were cellulosic; this is not a plastic concentration. |
| Danish selected small-particle analysis | three identified fragments | 20 to 150 µm | Observed in analyzed filter portions; PET and rubber also occurred in blanks. |
The Swedish method used 6.6 µm nominal minimum for identification under its image-processing rule. Its observed size range was evaluated using uncorrected detections, while its concentration used blank subtraction. Those are different analytical datasets. The size distribution therefore must not be described as though background particles had been removed from every size class.1
Why the blanks matter
In the Swedish investigation, researchers measured contamination alongside sample groups and subtracted counts by polymer. Some corrected count values became zero. This does not establish that the original water contained absolutely no plastic; it means that the subtraction method did not leave a positive count under those conditions. The study also found differences between infrared-derived estimates and direct thermal polymer-mass measurements at low concentrations.1
The Danish study calculated a larger-object detection threshold of 44 MP-like objects per sample. All water samples stayed below that threshold for the visual endpoint. Chemical analysis showed that many objects that looked like plastic were cellulose. A result described as MP-like should therefore remain MP-like unless spectroscopy confirms polymer identity. A low visual total cannot simply be reported as a confirmed plastic concentration.2
The additional smaller-particle analysis examined selected filter areas from selected locations. Its identified fragments show that a larger-object screen does not describe all size classes. At the same time, the presence of polymer material in a blank means that the smaller analysis cannot be used as an uncomplicated measure of contamination-free water sampling. The paper calls for broader assessment and more complete filter analysis.2
What the methods measure
Infrared imaging matches a particle’s spectrum with reference material and supplies dimensions. Thermal analysis breaks down polymers and measures chemical signals associated with polymer mass. Particle count, modeled mass from a particle’s shape, and directly measured polymer mass answer different questions. They cannot be substituted for each other with an assumed particle density or a representative diameter.1
Sampling volume, filter transfer, the fraction of a filter scanned, reference-library coverage, and the minimum-pixel rule all affect what can be reported. Closed sampling reduces opportunities for contamination but does not remove the need for blanks. Natural fibers, rubber from equipment, and uncertain spectra also require explicit handling rather than being automatically included in a synthetic-plastic total.21
What remains uncertain
These studies do not yield a universal tap-water count or a comparison of tap water with every bottled-water product. Their source waters, treatment systems, sample preparation, and size coverage differ. Neither study measures a human clinical outcome. Counts obtained in one system cannot determine the health effects of another supply, and a non-detection in a stated measurement window does not establish absence of smaller particles.12
The most useful reading of a water result keeps the sampled location, volume basis, polymer-confirmation method, size coverage, and treatment of blanks together. More directly comparable monitoring can establish whether patterns persist across seasons and systems. Until that evidence is available, source-specific results should remain separate from claims about all drinking water.
Regulatory status
The EU decision adopts a measurement methodology for water intended for human consumption, while California’s supplied methods describe analysis in treated drinking water. Their scope, size coverage and quality-control requirements matter when comparing these papers.345 The supplied California handbook copy is dated before its adoption meeting; its proposed monitoring calendar is not presented as the verified current timetable.6 These documents are not used here as a health-based particle ceiling or as proof that a particular bottled-water product falls within a public-water monitoring program. Read the scope notes.
References
- Drinking plastics? Quantification and qualification of microplastics in drinking water distribution systems by µFTIR and Py-GCMSResearch article
- A Study of Microplastic Particles in Danish Tap WaterResearch article
- Commission Delegated Decision (EU) 2024/1441: methodology to measure microplastics in water intended for human consumptionLegal instrument
- SWB-MP1-rev1: Infrared spectroscopy of microplastic particles in drinking waterOfficial method
- SWB-MP2-rev1: Raman spectroscopy of microplastic particles in drinking waterOfficial method
- California microplastics drinking-water policy handbook, supplied August 9 versionPolicy document