Microplastics
Microplastics are almost certainly in your water and in your body.
That much is established. Whether the amount in tap water harms you is not, and no agency has set a health-based limit. Both cheap moves cost little: the reverse osmosis already worth installing for other contaminants removes them, and switching from bottled to filtered tap cuts intake more than any device.
health-based level (none exists)
None
No agency anywhere, federal, state, or WHO, has set a health-based limit for microplastics in drinking water, because the science cannot yet say how much is too much.
Microplastics: what is it, and where does it come from?
Microplastics are synthetic polymer particles between 1 micron and 5 millimeters, and nanoplastics are smaller still.
They reach drinking water from the breakdown of larger plastic debris, from synthetic textile fibers and tire wear washing into source water, from plastic infrastructure and packaging, and, for bottled water specifically, from the bottle and cap.
They are chemically diverse, polyethylene, polypropylene, PET, polystyrene, PVC and others, and usually weathered and pigment-loaded rather than pristine. This is a post-1950 exposure with no evolutionary precedent, which is the structural reason it deserves to be taken seriously rather than waved off.
The container matters more than the source: bottled water carries far more than tap.
Microplastics: why does it matter?
The particles are present, including inside us, measured in human blood, in the placenta, and in arterial plaque.
And the evidence that they cause disease at real-world exposure is, as of early 2026, thin. The strongest harm signal comes from a study of patients with detectable plastics in their carotid plaque, who had a roughly 4.5-fold higher rate of heart attack, stroke, or death over about three years of follow-up.
That is a strong association, and an association only: the authors do not claim cause, every patient already had significant arterial disease, and the surgical environment itself contains microplastics. Authoritative reviews are blunt that no human dose-response and no proven disease causation exist yet.
In 304 patients undergoing carotid surgery, those with detectable micro- and nanoplastics in their arterial plaque had a roughly 4.5-fold higher rate of heart attack, stroke, or death over about three years. The authors are explicit that this is an association, not proof of cause.
Plastic particles were detected and quantified in the blood of 17 of 22 healthy adult donors, the first such measurement in human blood. This establishes presence and uptake, not harm.
A single-particle imaging method estimated roughly 240,000 plastic particles per litre of bottled water, about 90 percent of them in the nanoplastic range that standard tests miss.
Qian et al., 2024 (Proceedings of the National Academy of Sciences)
A 2025 peer-reviewed review concluded that no causal relationship between microplastic uptake and health effects has been proven to date, and that high-dose animal and in-vitro studies are unsuitable for human risk assessment.
Microplastics: what do we grade it against?
The table below lists each level that applies to Microplastics, what it is based on and who set it, and says which ones are enforceable.
| Contaminant | Health-based level | Legal limit | Source (health-based) |
|---|---|---|---|
| Microplastics in drinking water | None set no health-based reference value exists to interpret a result against | None not a regulated drinking-water contaminant, no federal or CA MCL | WHO drinking-water assessment, 2019 |
| California program status | Measurement only SB 1422 defined microplastics, set a test method, and runs monitoring, but sets no health limit | None no California MCL and no OEHHA Public Health Goal | CA State Water Resources Control Board |
| Bottled vs tap intake (particles/yr) | ~90,000 vs ~4,000 a bottled-only drinker ingests roughly 22 times the microplastics of a tap-only drinker | none set | Cox et al., 2019 (Environ Sci Technol) |
Health-based levels come from peer-reviewed research and government risk scientists working without cost constraints, while legal limits are enforceable compromises. Your report grades to the health column.
What helps against Microplastics?
The approaches below are the ones people use for Microplastics at home. Each entry says what it does and what it cannot do, and not every one helps.
Direct fixes
Reverse osmosis at the kitchen tap
Removes microplastics by size exclusion, with greater than 95 percent retention reported in the research literature. This is the same under-sink unit already worth installing for PFAS, chromium-6, and nitrate, so microplastics are removed at no extra cost.
Covers your drinking water, not the microplastics that enter through food packaging or the rest of daily life. Nanoplastic exclusion is expected on size-exclusion physics, not from a measured removal percentage.
Bigger retrofits
Activated carbon block
A partial answer. A carbon block strains out the larger microplastics and traps some more on its surface.
Misses the sub-micron and nanoplastic fraction, the part people are most worried about. Carbon misses the smallest particles. Reverse osmosis catches the nanoplastic fraction that carbon leaves behind.
Free and behavioral
Drop bottled water for filtered tap
The cheapest and largest lever, and it costs nothing. Bottled water carries roughly 22 times the microplastic particles of tap, so switching cuts your intake more than a filter does.
The $598 microplastics lab test
Available on request. It counts particles in the 1 to 10 micron range with no polymer identification.
It misses the roughly 90 percent nanoplastic fraction, costs about as much as an entire core water panel, and there is no health-based number to read the result against. We bring it up only when every other water test comes back clean and you ask for it.
We do not push the microplastics test, and we hold ourselves to peer-reviewed evidence, which is currently light.
The test likely will not change what we would tell you to do: if you already need reverse osmosis for a contaminant whose harm is settled, microplastics are covered as a side effect, and if you do not, dropping bottled water does most of the work for free. We will run the test if you want it. We are not going to sell it to you on anxiety.
Common questions about Microplastics
Is the plastic in my water actually harming me?
No one can say yet. The particles are present in tap water and in human tissue, that much is established. But no agency has set a health-based limit, because the science cannot yet say how much is too much or whether tap-water levels matter for health at all. We can describe presence; we cannot interpret a number against a health standard, because no such standard exists.
Should I pay for a microplastics water test?
Probably not by default. The test runs about $598, roughly the cost of an entire core water panel, and it counts only 1 to 10 micron particles, missing the roughly 90 percent nanoplastic fraction that is hardest to detect and most worrying. With no health-based number to read the result against, it likely will not change our recommendation. We will run it if you want it.
What is the single best thing I can do about microplastics?
Stop drinking bottled water. A bottled-only drinker ingests roughly 22 times the microplastics of someone drinking tap, so switching to filtered tap is the largest reduction available, and it costs nothing. If you also have a reverse osmosis filter for other contaminants, that removes microplastics from your drinking water as a side effect.
Does a reverse osmosis filter remove microplastics?
Yes, for your drinking water. RO removes microplastics by size exclusion, with greater than 95 percent retention in the research literature, and its pore size is far below even the smallest plastic particles. This is the same under-sink filter you would install anyway for PFAS, chromium-6, and nitrate. It does not touch the microplastics that reach you through food packaging or the rest of daily life.
Why does Stasis test for lead and PFAS but not microplastics?
Because for lead and PFAS the science of harm is settled and there is a health-based level to compare your water against. For microplastics, there is no such level anywhere, and the harm evidence is still thin. Testing would give you a partial particle count with nothing to judge it against, so we offer it on request rather than by default.
Sources cited for Microplastics
Every number on this Microplastics page traces to one of the 10 sources below: 7 peer-reviewed.
Peer-reviewed
- Marfella et al., 2024 (New England Journal of Medicine)
- Leslie et al., 2022 (Environment International)
- Ragusa et al., 2021, 'Plasticenta' (Environment International)
- Qian et al., 2024 (Proceedings of the National Academy of Sciences)
- Cox et al., 2019 (Environmental Science & Technology)
- Microplastics: State of the Evidence on Human Health Effects, review, 2025 (Deutsches Ärzteblatt International)
- Membrane-process removal review, 2023 (Water Science & Technology)
Institutional & standards