Microplastics in Tap Water: Should You Be Worried?

Microplastics are in tap water worldwide

Microplastics are plastic particles smaller than 5 millimeters. They come from the breakdown of larger plastic waste, synthetic textile fibers shed during laundry, tire wear, and direct release from manufacturing and packaging. A 2017 investigation by Orb Media found microplastics in 83% of tap water samples collected worldwide and 94% of samples collected in the United States. The average US sample contained 4.8 microplastic fibers per liter.

A 2019 WHO report estimated that people ingest approximately 5 grams of microplastic per week, roughly the weight of a credit card, though much of this comes from food and air rather than water alone. Drinking water is one of several exposure routes, alongside seafood, salt, beer, honey, and airborne particles that settle on food.

Where microplastics in water come from

Microplastics enter the water supply through multiple pathways:

• Plastic pipes: PVC and polyethylene pipes used in water distribution systems can shed particles over time, especially as they age and degrade.
• Water treatment plants: While treatment removes many particles, conventional processes were not designed to target microplastics specifically. Some particles pass through sand filtration and other treatment steps.
• Source water contamination: Rivers, lakes, and reservoirs contain microplastics from agricultural runoff, urban stormwater, wastewater discharge, and atmospheric deposition.
• Bottled water packaging: Studies have found bottled water contains even more microplastics than tap water. A 2018 study by Mason et al. published in Frontiers in Chemistry found an average of 10.4 microplastic particles per liter in bottled water, roughly double the tap water average. The bottling and packaging process itself appears to be a significant source.
• Home plumbing: Plastic supply lines, flexible connectors, and plastic fittings within your home can contribute additional particles.

Types and sizes

Microplastics in drinking water fall into several categories:

Type	Size range	Common source	Filtration difficulty
Fibers	100 to 5,000 micrometers	Synthetic clothing, textiles	Moderate (caught by fine filters)
Fragments	10 to 5,000 micrometers	Breakdown of larger plastic items	Moderate
Microbeads	10 to 1,000 micrometers	Personal care products (largely phased out)	Moderate
Nanoplastics	Less than 1 micrometer	Further breakdown of microplastics	Difficult (pass through most filters)

Nanoplastics (under 1 micrometer or 1,000 nanometers) are the emerging concern. These particles are small enough to cross biological barriers, including cell membranes, the blood-brain barrier, and the placental barrier. Current detection methods cannot reliably measure nanoplastics in water, so the true exposure level is unknown.

Health implications: what the science says

The health effects of microplastic ingestion are an active area of research with significant uncertainties:

What the WHO says

The World Health Organization published its first report on microplastics in drinking water in 2019. The key conclusions:

• Microplastics larger than 150 micrometers are unlikely to be absorbed by the human body and pose minimal health concern.
• At current detected levels, microplastics in drinking water do not appear to pose a health risk.
• Significant data gaps exist, particularly for nanoplastics and long-term exposure effects.
• The WHO called for more research but did not recommend routine monitoring of microplastics in drinking water at this time.

Emerging research concerns

Research published after the WHO report has raised additional questions:

• A 2022 study in the journal Environment International detected microplastics in human blood for the first time, suggesting particles can enter the circulatory system.
• Studies in laboratory animals have shown that high doses of microplastics can cause gut inflammation, disrupt the gut microbiome, and trigger immune responses.
• Microplastics can carry other contaminants on their surface, including heavy metals, persistent organic pollutants, and pathogens. This "hitchhiker effect" may increase exposure to these substances.
• Nanoplastics are of greater concern because they can cross cell membranes and accumulate in organs. However, there is not yet enough data to set safe exposure levels.

Current regulatory status

As of 2025, there are no EPA regulations for microplastics in drinking water. No maximum contaminant level has been set. California has taken the lead on this issue: in 2020, the California State Water Resources Control Board adopted the first state-level definition of microplastics in drinking water and mandated standardized testing methods. California utilities began reporting microplastic levels in 2023. No federal standard is expected in the near term because standardized detection methods are still being developed.

How to reduce microplastic exposure from water

Filtration options ranked by effectiveness

Filter type	Pore size	Microplastic removal	Nanoplastic removal	Cost
Reverse osmosis	0.0001 micrometers	Effectively 100%	Yes	$150-$400 under-sink
Ultrafiltration	0.01-0.1 micrometers	Effectively 100%	Partial	$200-$500
Carbon block (tight)	0.5-1 micrometer	Very good (removes most)	No	$50-$150
Ceramic filter	0.2-0.5 micrometers	Very good	Partial	$100-$300
Granular activated carbon	20-50 micrometers	Limited (catches fibers, misses fragments)	No	$30-$80
Standard pitcher filter	20-50 micrometers	Limited	No	$20-$40

Reverse osmosis is the most effective option because its membrane pore size (0.0001 micrometers) is orders of magnitude smaller than even nanoplastic particles. A tight carbon block filter (0.5 micrometer rating) is a good second choice and is simpler to install and maintain. See our under-sink filter guide.

Beyond filtration

• Avoid heating water in plastic containers. Microwaving or heating food in plastic increases particle release.
• Avoid bottled water when possible. Bottled water consistently shows higher microplastic counts than tap water. See our bottled vs. tap comparison.
• Use glass or stainless steel containers for storing drinking water.
• Replace aging plastic supply lines in your home with copper or PEX if renovating.

Should you be worried?

At current detected levels, microplastics in drinking water are not a proven health risk based on available evidence. The WHO and other health authorities have not raised alarm. However, the science is young, nanoplastics are poorly understood, and long-term exposure studies do not yet exist. If you want to reduce your exposure as a precaution, a reverse osmosis system or tight carbon block filter at your kitchen sink is an effective, affordable step. Check your city\'s water quality data for other contaminants that may be a higher priority for your area.