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Microplastics in Drinking Water: What We Know and What You Can Do

Published April 9, 2026

Microplastics in Drinking Water: What We Know and What You Can Do

What Are Microplastics?

Microplastics are tiny plastic fragments smaller than 5 millimeters — about the size of a sesame seed or smaller. They come from the breakdown of larger plastic products, synthetic textiles, tire wear, food packaging, and cosmetics containing plastic microbeads.

They're not just in the ocean. Microplastics have been found in air, soil, food, and drinking water worldwide. They are now considered ubiquitous environmental contaminants.

Are Microplastics in My Drinking Water?

Almost certainly, yes — at some level.

A 2019 World Health Organization review found microplastics in more than 90% of bottled water samples tested globally, and in most municipal tap water samples analyzed in research studies. Concentrations varied widely depending on location, water source, and treatment methods.

Here's what makes microplastics different from other contaminants:

  • No federal standard exists. The EPA has not established a Maximum Contaminant Level (MCL) for microplastics in drinking water. There is no legal limit to measure against.
  • Not part of routine monitoring. No federal or state program currently requires utilities to test for microplastics. (Note: EPA's UCMR5 program monitors PFAS and other emerging contaminants, but not microplastics specifically.)
  • Wisconsin DNR does not test for microplastics. State compliance monitoring covers regulated contaminants like nitrate, lead, and disinfection byproducts — microplastics are not on the list.

This means your local water report won't mention microplastics, even if they're present. The data gap is real.

Should I Be Concerned?

The honest answer: we don't know yet.

The WHO's 2019 assessment concluded that "based on the limited information we have, microplastics in drinking water don't appear to pose a health risk at current levels." But the same report acknowledged significant data gaps — particularly around long-term exposure effects and the health impacts of the smallest particles (nanoplastics under 1 micrometer).

The concern isn't acute toxicity. It's cumulative exposure over decades: microplastics may carry chemical additives (phthalates, bisphenols) and can adsorb environmental pollutants. Research into whether chronic low-level exposure contributes to inflammation, gut disruption, or other health effects is ongoing but inconclusive.

This is an area of active scientific research, not settled science. Being informed — without being alarmed — is the right posture.

What Filtration Actually Works?

Not all water filters are equal when it comes to particles this small. Here's what the evidence shows:

Reverse Osmosis (NSF 58) — Strongest Evidence

RO membranes have a pore size of approximately 0.0001 microns. Microplastics range from 1 to 5,000 microns. The size difference means an RO membrane effectively blocks microplastic particles. Lab studies consistently show the highest reduction rates of any filtration technology.

RO is the most effective single technology for microplastics removal with the strongest body of evidence.

Carbon Block Filters (NSF 53) — Effective for Larger Particles

Solid carbon block filters certified under NSF 53 can trap larger microplastic particles through physical filtration. They are more effective than granular activated carbon (GAC) filters for particle removal because the compressed block structure creates smaller, more consistent passages.

However, carbon block effectiveness varies by manufacturer and filter density. Not all NSF 53 filters perform equally for microplastics.

NSF 401 — Limited and Evolving

NSF 401 addresses "emerging contaminants," but it was primarily designed for pharmaceuticals, pesticides, and herbicides — not microplastics. Some filters certified under NSF 401 may reduce microplastics incidentally, but the certification alone is not a guarantee of microplastics removal. The standard is still evolving.

What Doesn't Work

  • Standard pitcher filters — Pore sizes are generally too large to catch microplastics smaller than 50 microns.
  • Sediment filters alone — Designed for visible particles (sand, rust), not microscopic plastics.
  • UV treatment — Kills bacteria and viruses but does nothing to physically remove particles.

What You Can Do

  1. Check your water report. While it won't show microplastics, understanding what IS in your water helps you make informed filtration decisions. Search your water system on WaterAdvantage.

  2. If microplastics concern you, RO is the strongest evidence-based option. It addresses microplastics alongside many other contaminants including PFAS, lead, and nitrate.

  3. Get a site-specific water test. An on-site analysis provides the most accurate picture of your actual water quality — including contaminants that may not appear in annual reports.

Sources

This article is provided by WaterAdvantage.org. The site author is employed by Bottleless Nation, a commercial water filtration company. This content provides factual information based on public data, not brand-specific recommendations. Learn more.