Research on microplastics in drinking water has moved fast in the last five years. We now know they’re present in nearly all tap water tested globally, that bottled water contains more than tap, and that RO filtration removes them at high rates. What we don’t know yet is whether microplastics at the concentrations found in drinking water cause harm in humans.

That second point matters for how this page is written. Researchers have found associations between microplastic exposure and various health outcomes. They haven’t established that microplastics in drinking water at typical concentrations cause disease. Writing otherwise would overstate the evidence.

Disclaimer: The health effects of microplastics in drinking water are actively being studied. The EPA has not established a Maximum Contaminant Level for microplastics. Consult your doctor if you have specific health concerns.

What We Know About Microplastics in Tap Water

A 2023 study in Environmental Science and Technology found microplastics in 100% of tap water samples across multiple countries. A widely-cited 2018 analysis detected microplastics in 83% of US tap water samples.

The 2024 NEJM study that received heavy media coverage found an association between microplastic particles in arterial plaque and cardiovascular events. It was an association study, not causal proof. That distinction matters. Researchers found an association, not evidence that microplastics caused the outcomes.

The EPA and WHO are in a research phase. No MCL exists for microplastics. The precautionary logic for reducing exposure is reasonable. The claim that microplastics in your drinking water are directly harming you right now is not established by current evidence.

Which Filters Actually Work

Reverse osmosis (most effective):

RO membranes have a pore size of 0.0001 microns. Microplastics range from 1 micron on the small end to 5 millimeters. There’s no mechanism by which a microplastic can pass through an intact RO membrane, it’s a physical size barrier.

A 2025 study published in Nature npj Clean Water tested multiple filtration technologies and found RO removed more than 99.9% of microplastics. This is the strongest evidence currently available for any residential filtration technology.

RO also removes PFAS, lead, fluoride, nitrates, arsenic, and a range of other contaminants. If microplastic reduction is one of several reasons you’re considering a filter, RO addresses all of them with a single system. See the best under-sink RO systems.

Carbon block filters (meaningful reduction):

Carbon block filters are solid compressed carbon, not loose granules. The tight structure physically traps particles as water is forced through. Carbon block filters reduce microplastics, though specific reduction rates vary by filter design and microplastic size distribution.

Carbon block is used in many under-sink filters and in premium pitcher filters like Clearly Filtered. These perform differently than standard pitcher filters using granular carbon.

Granular activated carbon (GAC), largely ineffective:

The loose carbon granules in most basic pitcher filters (including standard Brita models) have large channels between the granules. Water flows through these channels, and microplastic particles move with it. GAC is effective for chlorine and some organic compounds. It’s not an effective microplastic barrier.

Ultrafiltration (UF), effective but less common at home:

UF membranes have pore sizes around 0.01 microns. That’s larger than RO but far smaller than most microplastics. UF removes microplastics, bacteria, and cysts. It’s common in some whole-house systems and commercial settings. Less common in residential point-of-use configurations, but some brands offer countertop UF units.

Boiling with settling, partial, for hard water:

The 2024 study from researchers at Guangzhou Medical University found that boiling hard tap water and letting it cool reduced microplastic concentrations by 84-90%. The mechanism: calcium carbonate precipitates out during boiling, and the falling calcium carbonate encapsulates microplastic particles, which then settle to the bottom of the container.

In soft water (low calcium), the effect was smaller, around 25%.

This is an interesting finding but not a primary recommendation. Boiling doesn’t help with PFAS, lead, or nitrates. It concentrates other dissolved minerals. And it’s inconvenient for daily drinking water. If you don’t have a filter and are on hard water, boiling and decanting the cooled water is a zero-cost interim measure. But it’s not a substitute for a proper filter.

The Bottled Water Problem

Switching to bottled water to avoid microplastics is one of the more counterproductive decisions you can make. The data is clear: bottled water contains more microplastics than tap water, not less.

The 2018 analysis that examined bottled water from 11 international brands found an average of roughly 325 microplastic particles per liter. Tap water in the same analysis averaged around 5 particles per liter. The plastic bottles themselves, the caps, and the filling process all introduce microplastics into the product.

Single-use plastic water bottles are also a primary source of microplastics entering the environment and eventually the water supply. Using a home filter and a reusable stainless or glass bottle reduces your microplastic exposure and your contribution to the broader problem.

What the Research Doesn’t Tell Us Yet

The health question remains genuinely open. Scientists are studying:

• Which sizes of microplastics are most bioavailable (able to enter cells and bloodstream)
• Whether the plasticizer chemicals embedded in particles cause harm independently of the particles themselves
• What concentrations matter clinically

The WHO concluded in 2019 that, based on available evidence, microplastics in drinking water don’t appear to pose a health risk at current levels. Research since then has introduced more complexity. The 2024 NEJM finding generated significant attention, though it was observational and can’t establish that microplastics caused the cardiovascular outcomes.

Writing “microplastics in your water are dangerous” overstates the evidence. Writing “there’s no reason to think about this” understates the concern. The honest position is that reducing exposure is a reasonable precaution, especially because the best filter for microplastics (RO) also addresses confirmed health-risk contaminants.

The Practical Recommendation

Test your water with a lab first. Find out what else is in it beyond microplastics. Then choose a filter that addresses your full contaminant profile.

If you want the broadest protection including microplastics, an NSF 58-certified RO system handles microplastics at 99.9%+ removal rates while also addressing PFAS, lead, arsenic, fluoride, and nitrates. That’s the strongest single intervention for drinking water quality.

If budget is the primary constraint and you’re specifically targeting microplastics, a carbon block filter (not granular) from a brand that publishes independent testing provides meaningful reduction at a lower cost.

For help matching your water quality to the right filter type, see what water filter do I need and the microplastics in drinking water overview.