California Microplastics Standard: A Guide for US Brands

Key Takeaways for US Brands

California’s State Water Resources Control Board (SWRCB) framework is the strictest public reference for microplastics in drinking water. It includes a formal definition, two validated test methods, and a phased monitoring program.
US brands can map their existing lab data to the California framework and gain a clear, external reference point for plastic-reduction claims, even though no lab can prove a complete absence of plastic.
Current validated methods only measure particles down to 20–50 micrometers. The 1–20 micrometer and nanoplastic ranges remain unmeasured, so “none detected” means “none above the method’s limit,” not “none at all.”
The Wellness Quality Institute’s Plastic-Free Pathway Verification (WQI-CS-01) reviews a company’s existing lab data against defined criteria and issues a scope-locked, registry-backed verification decision instead of an impossible zero-plastic claim.
See how the Wellness Quality Institute can translate your current lab reports into a defensible, registry-backed claim.

The US Landscape for Plastic-Reduction Claims

The United States has no federal standard for microplastics in consumer products. The US EPA’s April 2026 draft Sixth Contaminant Candidate List puts microplastics on the federal radar for the first time, but EPA declined to add microplastics to its proposed UCMR 6 monitoring list, in part because no validated federal drinking water test method exists yet. A June 2026 report confirmed that EPA has paused broader microplastics testing requirements for US drinking water.

In that vacuum, brands using “plastic-free,” “microplastic-free,” or similar language face growing risk. State attorneys general are already pursuing cases involving microplastics and plastic-reduction claims, and class actions targeting unsubstantiated claims are increasing. Retailers, procurement teams, and legal reviewers often treat self-reported lab results as marketing, not evidence, because no independent party has confirmed what those results actually support.

The California framework serves as the most credible reference point available today. It does not create a consumer-product compliance obligation for brands outside California. It matters because California is the only jurisdiction that has published a formal definition, validated analytical methods, and a structured monitoring program. Brands that align their lab data with that framework gain a clear, defensible external yardstick. Understanding exactly what that framework defines, and what it can and cannot measure, prepares brands to make claims that hold up under scrutiny.

Fragments of plastic suspended in blue water below the surface. — Plastic doesn't disappear — it fragments. These secondary microplastics are the breakdown products of everyday objects, and independent research now detects them across the water supply. Detection, though, establishes presence, not absence.

See how the Wellness Quality Institute’s independent review can turn your existing microplastics data into claims retailers and legal teams will accept.

California’s Microplastics Definition and Size Range

Under the SWRCB’s Policy Handbook (SWRCB-DDW-21-002E), the effective date of which remains TBD, California defines microplastics in drinking water as solid polymeric material with particles having at least three dimensions greater than 1 nanometer and less than 5,000 micrometers. In plain language, this covers any solid plastic particle larger than one billionth of a meter and smaller than five millimeters, measured across three dimensions.

That definition is intentionally broad, and it reaches beyond what current test methods can reliably measure. The California framework covers particles down to 1 nanometer. The best validated methods begin at 20 or 50 micrometers, which are thousands of times larger. This gap reflects the real limits of today’s measurement science, not a missed detail in the regulation. Understanding that gap forms the foundation of any honest, defensible claim.

Colorful plastic fragments in water inside a laboratory petri dish. — Microplastics are particles smaller than five millimeters. Current methods can count and identify them at the upper end of that range, but reliable measurement falls away as particles get smaller — a limit that shapes every honest claim.

Published Analytical Methods: SWB-MP1-rev1 vs. SWB-MP2-rev1

California has published two standard operating procedures for microplastics analysis in drinking water. The table below compares their key parameters in practical terms.

Parameter	SWB-MP1-rev1 (Infrared Spectroscopy)	SWB-MP2-rev1 (Raman Spectroscopy)
Analytical technique	Fourier-transform infrared (FTIR) microscopy	Raman microscopy
Validated particle-size range	>50 µm through 5,000 µm	>20 µm through 5,000 µm
Lower size limit (validated)	50 micrometers	20 micrometers
Unvalidated fraction	1–20 µm and below	1–20 µm and below
Primary strength	Less affected by fluorescence, suitable for liquids with suspended solids	Better resolution for smaller particles in very clean water
WQI acceptance status	Accepted method under WQI-CS-01	Accepted method under WQI-CS-01

The 1–20 micrometer fraction, which covers particles between one and twenty micrometers, is not validated under either method. Everything below 1 micrometer, often called the nanoplastic range, currently sits beyond reliable commercial measurement. Micro-Raman spectroscopy can reach particles as small as 1 micrometer in research settings, but that capability is not validated within the California framework. A “none detected” result from either method means no particles were found above that method’s lower limit, not that no plastic exists in the sample.

ISO 16094-2:2025 describes vibrational spectroscopy methods for microplastics in waters with low suspended solids, including drinking water. The Wellness Quality Institute may accept this standard as an analytical reference when the method, sample type, laboratory validation, and equivalence are documented and reviewed. It is not automatically interchangeable with the California methods, and WQI evaluates equivalence case by case.

2026 DTSC Candidate Chemicals Update for Microplastics

On June 18, 2026, the Department of Toxic Substances Control (DTSC) Safer Consumer Products Program finalized a regulation adding microplastics to California’s Candidate Chemicals List, with the listing effective October 1, 2026.

For most brands, the immediate impact is limited but signals what may come next. The July 2026 rulemaking does not create new duties for most manufacturers or retailers. New requirements would only follow if DTSC later identifies specific Priority Products through additional rulemaking. One clear exception already exists. AB 1200 automatically triggers labeling and website disclosure rules for cookware sold in California that contains microplastics in the handle or any food- or beverage-contact surface, effective as early as October 1, 2026.

DTSC’s definition for the Candidate Chemicals List is broader than the SWRCB drinking-water definition. It covers plastics under 5 millimeters in their longest dimension, including intentionally manufactured particles such as microbeads and particles created when larger plastic items break down. Single-use plastics are expected to be the first priority products identified. No current product mandates apply to water or simple-liquid products under this update. The listing still signals where regulation is heading and highlights the value of building strong, defensible data systems now.

How Evidence Quality Shapes Claim Scope

A lab result is only as strong as the method and controls behind it. When you review any dataset, whether for internal use or for independent review, several linked questions determine whether that data can support a claim.

Start with laboratory qualification. The lab should hold California ELAP accreditation for the applicable SWB method, or ISO/IEC 17025 accreditation with the method and sample type clearly listed in its scope. That qualification sets the baseline for whether the method itself is defensible.

Next, confirm that the analytical method fits the product. A method validated for clean drinking water may not work for a colored beverage or a viscous liquid with suspended solids. Once the method and matrix match, review the tested particle-size range and the method’s lower detection limit. A “none detected” result is defined entirely by that floor.

Then review the polymer panel. The result only covers the polymer types the lab actually screened. Blank and contamination controls also matter. Procedural blanks should be run and reported, because contamination during sample preparation is a known failure risk. A 2024 PNAS study that reported about 240,000 plastic particles per liter of bottled water was later critiqued in a PNAS commentary for contaminated blanks and weak quality control. Replicates and a documented chain of custody from collection through analysis further strengthen the dataset.

Scientists in white coats working with samples and microscopes in a laboratory. — Only a small number of laboratories can genuinely test for microplastics, and capability varies by instrument and method. WQI reviews a company's existing third-party laboratory data against a defined standard — it does not run the tests itself.

Finally, check data recency. Microplastics levels can vary from lot to lot, so older results may not reflect current production. Under the Wellness Quality Institute’s standard WQI-CS-01, verification applies only to the specific product, dataset, tested particle-size range, polymer panel, and production period that were reviewed. A company cannot extend one dataset to a full product line or to the entire brand.

For Brands: Turning Lab Data into Registry-Backed Claims

Many US brands already have independent lab data on microplastic content. The missing piece is often a trusted, independent review that converts those reports into claims that retailers, procurement teams, and legal reviewers will accept.

The Wellness Quality Institute’s Plastic-Free Pathway Verification (PFPV), governed by WQI-CS-01, provides that review in four steps.

Application. The company submits its existing independent lab dataset, method documentation, product scope, and quality-control records. The Wellness Quality Institute does not run the lab tests, so the company’s relationship with its laboratory stays the same.
Assessment. The Wellness Quality Institute reviews the dataset against WQI-CS-01 criteria. These criteria include lab qualification, analytical method, product matrix, sampling, tested particle-size range, target polymer panel (at minimum PE, PP, PET, PS, PVC, PA, PC, and PMMA), reporting limits, blank results, spike recoveries, replicates, chain of custody, data recency, and product scope.
Verification decision. The outcome is either Standard Met or Standard Not Met. Standard Met requires that the dataset meets all technical and data-quality requirements and that no reportable target polymer particles are detected within the tested particle-size range and approved reporting limits. A non-detect result alone is not enough if reporting limits fall short of WQI requirements. Standard Not Met is a private outcome, never described as a failed product, and companies may resubmit with updated information.
Registry listing and approved claim language. Products that meet the standard receive a public registry entry with a unique registry ID, a scope-locked license to use the mark “WQI Plastic-Free Pathway Verified,” and approved claim language tied directly to the reviewed evidence.

The approved mark and claim language follow WQI-TM-01. The mark cannot appear as a standalone product claim and must link to or sit beside the Verification Scope record. It must not suggest plastic-free, microplastic-free, nanoplastic-free, zero plastic, California approval, government certification, or any health or safety certification. Verification lasts 24 months from the sampling date of the most recent accepted dataset, after which new data and re-verification are required.

One assessment fee covers the review, verification decision, and registry listing. There is no separate fee for the mark license or registry entry. Independent lab testing is arranged and billed directly by a qualified independent lab. Paying the assessment fee does not guarantee a Standard Met decision.

Start a Plastic-Free Pathway Verification review with your existing data and see what claim scope the Wellness Quality Institute can support.

Practical Compliance Checklist for Plastic-Related Claims

The checklist below highlights key areas to address before you make or support a plastic-related claim. Treat these as practical guideposts. Your exact steps will depend on product type, existing data, and market expectations.

Technical

Confirm the laboratory holds California ELAP accreditation for the applicable SWB method, or ISO/IEC 17025 accreditation with the method and matrix clearly listed.
Verify that the analytical method fits the specific product matrix, such as clean water versus a colored or viscous liquid.
Document the tested particle-size range and the method’s lower detection limit.
Confirm that the polymer panel covers at least PE, PP, PET, PS, PVC, PA, PC, and PMMA.
Confirm that procedural blanks, spike recoveries, and replicates were run and documented.
Confirm that chain of custody is documented from sample collection through analysis.

Operational

Identify the specific products, SKUs, and production lots covered by the existing dataset.
Confirm that the dataset reflects current production conditions.
Set a re-testing schedule that aligns with a 24-month verification period.

Regulatory and Claim Scope

Review packaging, marketing, and website copy for absolute claims such as “plastic-free,” “microplastic-free,” or “zero plastic” that you cannot substantiate.
Confirm that no claim stretches a single product’s result to an entire product line or to the company overall.
For cookware brands selling in California, audit handles and food-contact surfaces for microplastics ahead of the October 1, 2026 AB 1200 disclosure requirement.
Confirm that all claims include or link to the required scope disclaimer.

Reputational and Commercial

Confirm that any plastic-related claim is backed by independent third-party review, not only by internal or self-reported data.
Ensure retailer and procurement documentation points to a publicly checkable registry entry instead of an internal lab report.
Confirm that legal and advertising-claims counsel has reviewed all public-facing claim language.

Frequently Asked Questions

Does “California microplastics standard compliance” mean my product must meet a California law?

Not necessarily. California’s State Water Resources Control Board framework, which includes its definition, analytical methods, and monitoring program, applies as a legal requirement to public water utilities operating in California. For consumer brands outside that utility context, the California framework functions as a technical reference point. It is the most stringent, publicly documented standard available in the US. Brands that align their lab data with that framework do so voluntarily because it provides the most credible external yardstick for plastic-related claims. The Wellness Quality Institute aligns its criteria with the California framework for that reason, not because California created, approved, or endorsed WQI or its standard.

What does “none detected” on a lab report actually mean?

“None detected” means the lab did not find particles above that instrument’s detection floor for the polymer types screened in the specific lot tested. Under California’s SWB-MP1-rev1 infrared method, the validated lower limit is 50 micrometers. Under SWB-MP2-rev1 Raman, the validated lower limit is 20 micrometers. As discussed earlier, the California definition reaches down to 1 nanometer while validated methods begin at 20–50 micrometers. That gap means “none detected” is a bounded statement about what was found above a specific threshold, not a promise that no plastic is present. The unvalidated 1–20 micrometer fraction and unmeasurable nanoplastic range, described in the methods section, are the reason “none detected” can never mean zero plastic.

What does the July 2026 DTSC Candidate Chemicals listing mean for my brand right now?

For most consumer product categories, the near-term impact is limited. Adding microplastics to the Candidate Chemicals List allows DTSC to evaluate specific products for possible future rules, but it does not by itself create new duties for manufacturers or retailers. DTSC would need to complete further rulemaking and name Priority Products before requirements such as alternatives analysis or use restrictions apply. Cookware is the one immediate exception. AB 1200 automatically triggers labeling and website disclosure rules for cookware sold in California that contains microplastics in the handle or any food- or beverage-contact surface, effective as early as October 1, 2026. For water and simple-liquid brands, the listing is a forward-looking signal. Single-use plastics are expected to be the first priority products, and this context reinforces the value of building defensible, independently reviewed data before pressure increases.

Can the Wellness Quality Institute verify that my product is plastic-free?

No independent body can make that claim honestly today. Current lab technology cannot confirm the complete absence of plastic across every particle size, polymer type, and production lot. As outlined earlier, the California definition reaches down to 1 nanometer, while the best validated methods begin at 20 or 50 micrometers. That gap is the core reason no product can be certified plastic-free. The Wellness Quality Institute can instead review a company’s existing lab dataset against defined criteria. When the dataset meets all technical and data-quality requirements and no reportable target polymer particles are detected within the tested range and approved reporting limits, WQI may issue a Standard Met decision. That decision is locked to the reviewed product, dataset, tested range, polymer panel, and production period. The approved mark, “WQI Plastic-Free Pathway Verified,” signals verified progress toward plastic-free standards, not a claim that the product contains no plastic.

Why does independent review matter if I already have a lab report?

A lab report and a defensible market claim serve different purposes. A lab report describes what the laboratory found. It does not, by itself, explain what kind of claim that result supports, whether the method fit the product, whether blanks and contamination controls were adequate, or whether reporting limits were tight enough to support any claim. Self-reported results are often discounted as marketing, because they resemble a company grading its own homework.

The Wellness Quality Institute’s review is independent. WQI has no commercial interest in the outcome, does not perform the testing it reviews, and publishes its criteria. That separation converts a lab report into a finding that an independent party is willing to stand behind. The resulting claim carries more weight with retailers, procurement teams, and legal reviewers.

Conclusion: Building Defensible Plastic-Related Claims

The California drinking-water microplastics framework, together with the July 2026 DTSC Candidate Chemicals update, offers the most rigorous public reference available for plastic-related claims in the United States. It includes a formal definition, two published analytical methods, and a phased monitoring program, yet it remains, by the State Water Resources Control Board’s own acknowledgment, an incomplete end-to-end regulatory method. The gap between what the definition covers and what any method can measure is the central fact that shapes every honest claim.

For US brands, the path forward is clear. As outlined at the start, absolute plastic-free claims remain indefensible, and the legal exposure from making them continues to grow. The safer position is a scope-locked, independently reviewed claim that states exactly what the data supports and nothing more.

The Wellness Quality Institute reviews companies’ existing independent lab data against criteria aligned with the California framework. It issues verification decisions that are publicly checkable, scope-locked, and paired with approved claim language that stays within the evidence. Phase 1 focuses on water and suitable simple-liquid products, where test methods are strongest. WQI verification is available to US companies nationwide. California serves as a technical reference point, not a geographic limit.

Turn your microplastics lab data into a registry-backed claim you can stand behind by working with the Wellness Quality Institute.