Microplastics in Water: What Brands Need to Know

Written by: Scott Steveson, Specialist

Key Takeaways

• August is National Water Quality Month, and 2026 marks the first federal attention to microplastics in drinking water, even though measurement standards are still not in place.
• Microplastics are plastic particles smaller than 5 mm. Current validated lab methods reliably detect only particles above 20–50 micrometers, so smaller particles remain out of reach.
• Studies have found microplastics in most tap and bottled water samples. Detection alone does not prove health harm, and regulatory definitions reach far below what labs can measure.
• No laboratory can prove a product is completely plastic-free because particle-size limits, many different plastic types, and batch variability prevent absolute negative claims.
• Brands that want credible claims should use independent verification of real lab data through the Wellness Quality Institute’s Plastic-Free Pathway Verification program.

How National Water Quality Month Connects to Microplastics

National Water Quality Month has been observed every August since the U.S. Environmental Protection Agency created it in 2005. Its policy foundation rests on two landmark laws. The Clean Water Act of 1972 set surface-water quality standards and restricted the discharge of toxic materials into waterways. The Safe Drinking Water Act of 1974 extended federal protection to groundwater and public water systems. The observance reminds both the public and water professionals that pollution entering streams and rivers upstream can eventually reach drinking-water sources, and that protecting those sources is a shared responsibility.

In 2026, National Water Quality Month coincides with real regulatory movement on microplastics. The EPA added microplastics to its draft Contaminant Candidate List 6 in April 2026, which is the first formal step toward possible federal regulation under the Safe Drinking Water Act. At the same time, EPA and HHS jointly announced actions on microplastics. HHS’s ARPA-H launched the $144 million STOMP program to detect and remove microplastics in the human body, and EPA added microplastics to its Contaminant Candidate List for drinking water. These moves send strong signals about future regulation. They are not yet regulations and do not solve the measurement limits described below.

Why Microplastics Dominate Today’s Water Quality Concerns

Microplastics matter because they are everywhere and hard to measure fully. Plastics are synthetic materials made from long chains of molecules called polymers, such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), PVC, and nylon. Plastic does not biodegrade. It breaks into smaller and smaller pieces over time.

Microplastics are plastic particles smaller than 5 millimeters. They include fragments, fibers, films, and beads that are large enough, at the upper end of the size range, to be counted and chemically identified with current laboratory methods. Nanoplastics are particles smaller than 1 micrometer, about a thousandth of a millimeter, and they sit below the reliable reach of most commercial testing methods.

Sources fall into two groups. Primary microplastics are manufactured small, such as microbeads in personal-care products and industrial pellets. Secondary microplastics, which are far more common, form when everyday plastic items break down. These include packaging, synthetic textiles, tire wear particles, agricultural films, and airborne dust that settles on food and open water. The scale of the problem tracks global production. The OECD’s Global Plastics Outlook reports that global plastics production roughly doubled from 234 million tonnes in 2000 to about 460 million tonnes in 2019, with production, use, and waste projected to rise another 70% by 2040 on current paths. Every item produced eventually breaks down somewhere.

Detection has followed this growth. A 2018 peer-reviewed study by Kosuth, Mason, and Wattenberg in PLOS ONE found anthropogenic particles in 81% of 159 tap water samples from five continents. The 2018 Mason et al. study in Frontiers in Chemistry found microplastic contamination in 93% of 259 bottled water samples across eleven brands, with a confirmed average of 10.4 particles larger than 100 micrometers per liter and an additional average of 325 particles per liter when including smaller particles between 6.5 and 100 micrometers identified by Nile Red tagging.

Why Detection of Microplastics Does Not Automatically Mean Harm

Finding a particle does not prove that it causes damage. This distinction sits at the center of the entire discussion, and blurring it creates misinformation in both alarmist and dismissive directions.

The World Health Organization’s 2019 assessment, Microplastics in Drinking-Water, reviewed three possible hazard routes: the physical particles, chemicals that may be carried on them, and micro-organisms that may attach to them. On the limited evidence available, the report found low concern for each route, while stressing that this conclusion rests on incomplete information and that more research is urgently needed.

Two separate questions often get mixed together. The first involves chemical additives carried by some plastics, such as phthalates and bisphenols. These substances are well established as endocrine-disrupting compounds, with evidence from animal studies, human clinical observation, and epidemiology, as summarized in the Endocrine Society’s scientific statement on endocrine-disrupting chemicals. The second question concerns what the physical microplastic particles themselves may do in the body.

A rapid systematic review of microplastic exposure effects on human digestive, reproductive, and respiratory health identified oxidative stress and systemic inflammation as the two most consistently described potential mechanisms across the literature. These are early findings from studies with small samples, and some have drawn methodological criticism. They show that particles are present and interacting with biological systems and that the topic deserves serious attention. They do not yet prove direct cause-and-effect harm in humans. Understanding what the evidence does and does not show matters because it shapes what claims laboratories can support, which leads directly to the measurement problem.

Why Laboratories Cannot Prove a Product Is Plastic-Free

No laboratory can prove that a product is completely plastic-free, and that limit rests on three technical realities.

First, particle-size limits. The two analytical methods published by the California State Water Board, which currently provide the most stringent public reference framework, have validated detection ranges that start at 20 micrometers for Raman spectroscopy and 50 micrometers for infrared spectroscopy. California’s regulatory definition of microplastics reaches down to 1 nanometer. The gap between what the definition covers and what any validated method can reliably detect spans thousands of times in scale. The 1–20 micrometer fraction is not validated under either method, and everything below that range currently sits beyond reliable commercial measurement.

Second, polymer diversity. No single test screens every plastic type in every product format. Each result is limited by the list of polymers that the laboratory chose to test.

Third, lot-to-lot variability. A clean result on one production lot does not guarantee the next lot will match it. The EPA excluded microplastics from its proposed sixth Unregulated Contaminant Monitoring Rule in July 2026 because more research is needed before reliable monitoring methods can be set. If the federal government cannot yet require a standard monitoring method, no brand can credibly claim that its product has been proven free of plastic.

A positive finding needs only one particle. A negative claim would need certainty about everything a method did not and could not measure. Those are fundamentally different standards of proof. The California State Water Board is a state agency in California that sets standards for water quality. Its microplastics framework appears here as an example of rigorous technical guidance, not as a requirement for all organizations.

How Brands Currently Approach Plastic-Related Claims

Brands operate today without a shared U.S. federal standard for plastic or microplastic content in consumer products. This gap creates a claims environment where companies lack a common yardstick, and buyers cannot easily tell a rigorous claim from a marketing slogan.

Three pressures now converge on brands:

• Regulators and retailers are asking companies to back sustainability claims with real evidence, not only supplier statements or internal interpretations.
• Consumers are increasingly worried about microplastics and nanoplastics in everyday food, beverages, and personal-care products.
• Legal and reputational risks are rising for plastic-free claims that cannot be substantiated, and a growing number of class-action lawsuits target companies in this space.

Many companies already hold useful laboratory data. They have commissioned independent testing and acted on the results. What they often lack is a trusted way to turn that data into a claim. A lab report alone does not create a defensible market statement. Self-reported results carry less weight than independently reviewed data, and without independent review, even strong data can look like marketing. A brand may hold a report that reads “no microplastics detected” without realizing that the finding is limited by that instrument’s detection floor. In practice, it means none found above a certain size using a specific method on a specific lot, not none present at all.

How the Wellness Quality Institute Turns Lab Data into Credible Claims

The Wellness Quality Institute (WQI) exists to close the gap between real data and claims a company can stand behind. The Wellness Quality Institute is an independent verification body that reviews companies’ existing third-party laboratory data on plastic and microplastic content against a defined standard. This approach helps brands substantiate real progress toward plastic-free standards instead of making impossible zero-plastic claims.

The Wellness Quality Institute does not run laboratory tests. Its role is to independently review a company’s existing dataset, testing methods, product scope, and supporting controls against clear criteria. This separation between the organization that tests and the organization that reviews creates credibility that self-reporting cannot match.

The core program, Plastic-Free Pathway Verification, is governed by the standard WQI-CS-01 and produces one of two outcomes. “Standard Met” carries a verification decision, a scope-locked license to use the WQI mark, a public registry listing, and approved claim language. “Standard Not Met” is a private outcome that is never described as a failed product and can be resubmitted with updated information.

The Wellness Quality Institute’s Plastic-Free Pathway Verification does not certify that a product contains zero plastic, microplastics, or nanoplastics. It shows that the company is on a verified pathway toward plastic-free standards. Verification applies only to the reviewed products, submitted datasets, tested ranges, polymer panels, production or sampling periods, and supporting controls. The Wellness Quality Institute verification is not a California approval, government certification, or health or safety certification.

Learn how independent verification can turn your existing laboratory data into defensible market claims.

What the Wellness Quality Institute Actually Verifies

The Wellness Quality Institute’s review criteria align with the California State Water Board’s drinking-water microplastics reference framework. This framework serves as a technical reference point, not a geographic boundary. Verification is available to U.S. companies nationwide, not only those operating in California. California did not create, approve, authorize, or endorse the Wellness Quality Institute or its standard.

The review examines a defined set of elements:

• Laboratory qualification, meaning whether the testing laboratory meets accreditation requirements for the method and product type.
• Analytical method, meaning whether the method fits the product and whether the tested particle-size range is appropriate.
• Polymer panel, meaning a minimum panel covering PE, PP, PET, PS, PVC, PA, PC, and PMMA, with required reporting for other confirmed polymers and unidentified particles.
• Data quality, including blank results, spike recoveries, replicates, chain of custody, and data recency.
• Product scope, meaning the specific product, SKU, and production or sampling period under review.

“Standard Met” requires two conditions together. The dataset must satisfy all applicable technical and data-quality requirements, and no reportable target polymer particles can be detected within the tested particle-size range and approved reporting limits. A non-detect result alone is not enough. The reporting limits themselves must meet the Wellness Quality Institute requirements, or the non-detect result has no practical meaning.

Every “Standard Met” product receives a public registry entry. The record lists the verified party, product scope, matrix, production or sampling period, tested particle-size range, lower method limit, polymer panel, reporting limits, testing laboratory and its accreditation, verification and expiration dates, registry ID, approved result statement, and current status. The verification period lasts 24 months from the sampling date of the most recent accepted dataset. After that period, continued claim use requires re-verification with current data.

The approved mark, “WQI Plastic-Free Pathway Verified,” may not appear as a standalone product claim. It must link to or sit beside access to the Verification Scope record. The mark does not imply plastic-free, microplastic-free, nanoplastic-free, zero plastic, California approval, government certification, or health or safety certification. The word “pathway” always remains part of the mark. It signals a verified pathway toward plastic-free standards, not a fully plastic-free product.

Next Steps for U.S. Brands That Want Defensible Claims

The measurement limits described here are hard technical limits, not gaps in diligence. They apply to every laboratory, every method, and every product on the market today. No brand can honestly claim that its product is free of plastic, because no method can confirm the complete absence of plastic across every particle size, polymer type, and production lot.

Brands can instead demonstrate genuine progress. They can do this through independent review of real laboratory data against defined criteria, with scope-locked outcomes and approved claim language that stays within what the evidence supports. This approach is more defensible than an absolute claim. In a market where unverifiable claims are becoming a legal liability, it is also more valuable.

A single Wellness Quality Institute assessment fee covers the review, verification decision, and registry listing. There is no separate mark-license or registry fee. Independent laboratory testing is arranged and billed separately by a qualified independent laboratory. Paying the assessment fee does not guarantee a verification decision.

Turn real lab data into a claim you can support. Talk to the Wellness Quality Institute about Plastic-Free Pathway Verification.

Frequently Asked Questions

What does “no microplastics detected” actually mean?

“No microplastics detected” usually means less than it sounds. The phrase means none were found above that instrument’s detection floor, for the plastic types it screened, in the lot it tested. A method validated to detect particles above 50 micrometers cannot see anything smaller, so “none detected” can coexist with particles that are present below that size threshold. As noted earlier, the gap between California’s regulatory definition, which reaches down to 1 nanometer, and validated detection methods, which begin at 20–50 micrometers, spans thousands of times in scale. A “none detected” result is a bounded statement about what one method found in one sample. It is not a guarantee that a product is free of plastic. Independent review of the method behind a result matters as much as the result itself.

Is bottled water worse than tap water for microplastics?

Research has generally found higher microplastic concentrations in bottled water than in tap water. The 2018 SUNY Fredonia study found an average of 325 microplastic particles per liter in bottled water, with polypropylene, the material used in many bottle caps, as the most common polymer. This pattern points to the packaging itself as a contamination route. That pattern does not mean tap water is clean. The tap water contamination rates cited earlier show widespread presence in municipal sources as well. Both sources contain detectable particles. Packaging material and the mechanical stress of filling and opening containers appear to be meaningful contributors to bottled water concentrations, which is worth considering when choosing containers and storage.

Can any filter remove all microplastics?

No filter can be said to remove all microplastics, because no method can confirm the complete absence of plastic particles across every size and polymer type. Reverse osmosis systems, which force water through membranes with pore sizes in the nanometer range, achieve among the highest removal rates in controlled studies, above 90% in some research, and are generally considered the strongest point-of-use option for reducing particle counts. High-quality solid carbon block filters certified to NSF/ANSI Standard 53 or 58 can reduce particles down to about 0.5 micrometers. Standard sediment filters in the 5–20 micron range are largely ineffective against nanoplastics smaller than 1 micrometer. No standard currently certifies specifically for microplastic removal, and filter performance depends on membrane condition, maintenance, and proper installation. The realistic goal is meaningful reduction, not guaranteed elimination.

NSF/ANSI Standard 53 or 58 refers to standards developed by NSF International and the American National Standards Institute. These standards set performance requirements for water treatment devices, including contaminant reduction claims.

Does WQI verification mean a product is plastic-free?

No. The Wellness Quality Institute’s Plastic-Free Pathway Verification does not certify that a product contains zero plastic, microplastics, or nanoplastics. Current laboratory technology cannot confirm the complete absence of plastic across every particle size and polymer type, and that limit applies across the industry. Verification confirms that a company’s existing laboratory dataset has been independently reviewed against defined criteria, within a specific tested particle-size range, for a specific product and production period, and that the dataset met all applicable technical and data-quality requirements. The mark, “WQI Plastic-Free Pathway Verified,” describes a verified pathway toward plastic-free standards, not an achieved plastic-free state. Verification applies only to the reviewed products, submitted datasets, tested ranges, polymer panels, production or sampling periods, and supporting controls. It is not a California approval, government certification, or health or safety certification.