Microplastics in Drinking Water: A Scientist’s Guide For Your Home

‍Eric Roy, PhD | Chief Scientist

When people talk about microplastics, they usually picture ocean pollution or beach litter. But for drinking water, this is a contaminant problem. Even more ironic, the solution many people turn to (bottled water) is often one of the highest-microplastic sources.

My goal here is to explain what microplastics are, how they enter drinking water, what the science currently supports, and how to remove them effectively at the tap.

What Are Microplastics?

The scientific research calls “Microplastics”  plastic particles smaller than 5 millimeters, but in drinking water we are mostly concerned with much smaller particles.

There are two scales that matter:

• Microplastics: Visible under a microscope.
• Nanoplastics: Smaller than a micron and harder to measure.

Plastic does not biodegrade. It breaks down mechanically into progressively smaller pieces. The smaller the particle, the more easily it can move through the environment and, potentially, through biological barriers.

Current Research Suggests:

• Larger microplastics are likely excreted.
• Smaller microplasitcs/nanoplastics may cross biological barriers, but this is still being studied.

The science is evolving, and the size distribution of particles matters as much as the material itself.

The Bottled Water Paradox

The people trying hardest to avoid contaminants often expose themselves to the highest microplastic levels.

Multiple studies show: Bottled water frequently contains more microplastics than tap water.

This is primarily due to packaging:

1. Plastic bottles shed particles during manufacturing.
2. Movement during shipping generates abrasion.
3. Even opening the cap releases microscopic fragments.

When you drink bottled water, you are often drinking particles shed from the container itself. Filtered tap water stored in glass or stainless steel is generally a better choice (and are far more environmentally friendly).

‍What the Science Says About Health Risks

Microplastics toxicology is early, but here is what is supported:

1. Ingestion Occurs: People ingest microplastics from food, bottled water, tap water, and household air.

2. Most Larger Particles Are Excreted:  Particles above several microns generally pass through the gut intact.

3. Nanoplastics Are Less Understood: Their size may allow them to interact with biological barriers that larger particles cannot, but research is ongoing.

4. Additives May Matter: Some plastics contain additives that may have independent health effects, separate from the particle itself.

Overall:  Microplastics have been detected in human blood, lung tissue, and placentas, but the long-term implications remain under investigation. That said, there are studies linking microplastic exposure to all kinds of health problems, including dementia.

How To Remove Microplastics From Drinking Water

Microplastics are physical particles, so removal is a physics problem.

• You need a mechanical barrier with pores smaller than the particle.
• The most reliable approach is Point-of-Use filtration at the tap you drink from.

Why Point-of-Use?Microplastics can shed from faucet components and downstream plumbing, so whole-home systems cannot address all sources.

Look for NSF/ANSI Testing for Particle ReductionThere is no NSF standard dedicated exclusively to “microplastics,” but NSF does certify filters for fine particle removal. These certifications are the best proxy for microplastic performance.

Filters that remove microplastics typically carry one or more of these:

1. NSF/ANSI Standard 42 – Particulate Reduction Class I

• Verified to remove particles 0.5 to 1 micron.
• Context: Most microplastics detected in water fall above this range.

2. NSF/ANSI Standard 53 – Cyst Reduction

• Found in select Carbon Blocks.
• This implies a very tight pore structure that captures small particles.

3. NSF/ANSI Standard 58 – Reverse Osmosis

• RO membranes have extremely small pore sizes and remove microplastics and many nanoplastics.

The Scientist's Rule: Look for “Particulate Class I (0.5–1 micron)” on the NSF certification listing. If this claim is missing, do not assume microplastic removal.

What Does Not Work

• Boiling water
• Pitcher filters (without particulate reduction claims)
• Refrigerator filters (that use loose granular carbon)
• Water softeners
• Sediment filters (rated only for large particles)

These products are not reliable for microplastic removal.

Frequently Asked Questions

Does boiling remove microplastics?No. It has no effect on plastic particles.

Is bottled water safer?Generally no. Studies show higher microplastic counts in bottled water compared to tap due to packaging degradation.

Can microplastics come from my plumbing?Yes. Some plastic pipes, fittings, and faucet components can shed particles.

Do fridge filters remove microplastics?Only if they use a solid block carbon element and are certified for Fine Particulate reduction.

What To Do Next

Switch From Bottled Water to Filtered Tap WaterThis is the single most effective way to reduce microplastic intake.

Install a Certified FilterChoose a point-of-use filter with NSF Particulate Reduction (Class I) or a Reverse Osmosis system.

Store Water SafelyUse glass or stainless steel, not plastic bottles that degrade with heat and abrasion.

Think About This PracticallyYou cannot eliminate microplastics from the environment. You can reduce avoidable exposure at the tap.

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