Plumbing
Microplastics: What We Know and What We Do Not
Rich Jordan · August 23, 2026 · 6 min read
Plumbing
Rich Jordan · August 23, 2026 · 6 min read
This is the third deep dive in our series on what is actually in your tap water. Microplastics are the category where the headlines are loudest and the science is youngest, which is an uncomfortable combination. So let me try to separate what is established from what is being extrapolated.
A microplastic is a plastic particle between one micrometer and five millimeters. Below one micrometer you are into nanoplastics, which are harder to detect and are probably the more important category, which we will get to.
They come from four main places:
The scale is genuinely hard to intuit. A 2024 review in Environment International surveying detection methods and occurrence in drinking water globally found contamination essentially everywhere researchers looked.
They are in tap water. Detected in municipal supplies on every continent that has been sampled.
They are in human tissue. Microplastics have been identified in human blood, in lung tissue, in placental tissue and in other organs. That means they cross biological barriers - the gut wall, the blood-brain barrier in animal studies, the placenta - that we had assumed would exclude them.
They carry other things with them. Plastic surfaces adsorb hydrophobic compounds from the surrounding water. A particle can arrive carrying pesticides, PCBs or endocrine-disrupting plasticizers on its surface. The particle is also often not pure polymer - it contains the additives, stabilizers, colorants and flame retardants that were compounded into it.
Whether the concentrations in drinking water harm people. The World Health Organization's assessment concluded that microplastics in drinking water do not appear to pose a health risk at currently observed levels. It also stated plainly that the evidence base is limited, that detection methods are inconsistent between studies, and that more research is needed - particularly on the smaller particles.
I have seen that WHO position quoted both ways: by people saying "see, it is fine," and by people saying "they admitted they do not know." Both readings are selective. The accurate reading is that the WHO looked at the available evidence, did not find a demonstrated risk at observed exposures, and flagged that the available evidence is thin.
What nanoplastics do. Most studies measure down to a few micrometers because that is what the instruments comfortably detect. Particles below that are much more numerous and much more biologically mobile, and they are the ones most likely to matter. We are largely measuring the category we can see rather than the category we should be worried about. That is a real limitation and researchers say so.
Whether the particle or the chemistry is the problem. If harm exists, it could come from physical presence causing inflammation, from the plastic's own additives leaching out, from the pollutants adsorbed onto the surface, or from some combination. These have different implications and the field has not resolved them.
Conventional municipal treatment is unexpectedly decent at this. Coagulation, flocculation and sand filtration remove a large share of larger microplastic particles - some studies report better than 80% removal of particles above a few micrometers.
Two problems remain.
The first is that removal efficiency drops sharply as particle size drops. The smaller the particle, the more likely it passes through, and the smaller particles are the more numerous ones.
The second is that the distribution system itself is a source. Plastic service lines, plastic pipe, gaskets, fittings and storage tank liners all shed. Water can leave the plant cleaner than it arrives at your tap.
This is one of the more satisfying categories, because microplastics are particles, and particles are the thing filtration is genuinely good at.
Reverse osmosis is essentially complete. An RO membrane has pores measured in fractions of a nanometer. Every microplastic and every nanoplastic is enormously larger than that. If your water goes through a functioning RO membrane, plastic particles do not. This is not a marginal reduction - it is an exclusion by size.
Sub-micron mechanical filtration works well. A carbon block filter rated at 0.5 microns or finer removes the great majority of microplastic particles by straightforward physical capture. This is the most cost-effective option if microplastics are your specific concern.
Standard whole-house sediment filters help but are coarse. A typical 5-micron sediment cartridge catches larger particles and passes the rest. Useful, not sufficient.
Pitcher filters vary enormously and most are not rated for particle removal at the relevant size.
Boiling has mixed evidence. Some research suggests boiling hard water causes calcium carbonate to precipitate and trap nanoplastics, which can then be strained out. It is an interesting result. It is not a treatment strategy, and it does nothing in soft water.
I keep coming back to it because it is the single most actionable finding in this entire post.
If you drink bottled water because you are worried about contaminants in your tap, you should know that on microplastics specifically, the research consistently finds bottled water contains more of them, not fewer. The bottle sheds. The cap sheds every time it is opened. Heat in a warehouse or a car accelerates it.
A filtered tap is cheaper, produces less waste, and on this contaminant performs better. That is not a sales pitch for a filter - it is true of any properly specified filter, including ones we do not sell.
If microplastics are your primary concern, a sub-micron carbon block filter at the kitchen tap handles it at modest cost. If you also care about PFAS, pharmaceutical residues or dissolved contaminants generally, go to reverse osmosis instead - it covers microplastics comprehensively and covers the dissolved categories that carbon alone does not.
And I would hold the uncertainty honestly. We know these particles are in the water and in our bodies. We do not know what they do there. Filtering is cheap, effective and reversible. Waiting for certainty on a question this young is also a decision, and it is the one that defaults to continued exposure.
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