Independent Review Of Laboratory Plastic Testing: A Guide

Written by: Scott Steveson, Specialist, Wellness Quality Institute

Key Takeaways

• Independent review sits between the lab report and your marketing, and it turns raw plastic testing data into claims brands can defend.
• Testing alone does not define what you can safely say. A qualified reviewer examines the method, the sample, the controls, and the numbers before any claim goes public.
• “None detected” means the method found no particles above its detection floor for the polymers it checked in the lot it tested. It does not mean the product contains zero plastic.
• Accreditation scope, method validation, contamination controls, chain of custody, and data recency all shape how far a claim can honestly go.
• Talk to the Wellness Quality Institute about reviewing your lab data and building claims you can stand behind.

Why Independent Review Matters For Plastic Claims

The Wellness Quality Institute provides independent review that turns raw plastic testing data into claims brands can defend in the market. Independent review sits between the lab report and your marketing, and it protects you when retailers, regulators, or litigators ask hard questions.

Testing alone does not define what you can safely say. Independent review looks at the method, the sample, the controls, and the numbers, then translates that into clear, supportable language for your labels and campaigns.

What Independent Laboratory Plastic Testing Covers

Independent laboratory plastic testing means a third-party lab analyzes your product and has no commercial stake in the outcome. The lab does the measurements, and the brand does not grade its own homework.

Independence reduces conflicts of interest and builds trust with retailers, regulators, and attorneys. Many retailers and regulators now expect third-party testing before they accept plastic-related claims.

Independent review is a separate step. A qualified reviewer, who did not run the tests and has no financial interest in the result, examines the dataset, the method, and the controls. That review defines what the data actually supports and how far the claim can go.

Self-reported results, even when technically strong, often look like marketing. An independent reviewer explains whether the data is credible, whether the method fits the product matrix, and what the findings mean in plain language.

Why Independence Closes The Credibility Gap

Independence forms the backbone of credible plastic claims. ISO/IEC 17025:2017 Clause 4 requires laboratories to identify and manage risks to impartiality on an ongoing basis. The standard expects labs to keep commercial, financial, and other pressures from affecting test results.

ISO/IEC 17025:2017 Section 4.1.3 states that laboratories must prevent commercial, financial, or other pressures from compromising impartiality. Safeguards include prohibitions, disclosures, policies, and institutional structures. Section 4.1.4 requires labs to identify risks to impartiality that arise from ownership, governance, management, personnel, shared resources, finances, contracts, or sales commissions.

True independence means the laboratory has no financial incentive to reach a specific outcome. An independent reviewer adds another layer by evaluating data without having performed the tests and without any commercial tie to the result. That separation creates credibility that self-reporting cannot match.

Key Testing Methods And Standards For Plastic And Microplastic Claims

Plastic testing falls into several categories, each with its own standards. Knowing what each category measures, and what it cannot measure, helps you read reports accurately.

Mechanical testing evaluates physical performance. Standards such as ASTM D638 and ISO 527 for tensile testing of rigid and semi-rigid plastics measure tensile strength, stiffness, and elongation. ASTM D790 and ISO 178 for flexural properties use a three-point bend setup to measure flexural strength and flexural modulus. ASTM D256 (Izod) and ASTM D6110 (Charpy) measure impact resistance by reporting the energy a notched specimen absorbs when a pendulum fractures it.

Beyond mechanical performance, thermal testing looks at how plastics behave under heat. ASTM D648 measures Heat Deflection Temperature (HDT), the temperature where a plastic bends under a specific load. ASTM E793 and ISO 11357 for Differential Scanning Calorimetry (DSC) determine melting point, glass transition temperature, and crystallinity.

Chemical and spectroscopic identification matters most for microplastic claims. The main methods are micro-FTIR (Fourier-transform infrared spectroscopy), micro-Raman spectroscopy, and pyrolysis-GC/MS (gas chromatography-mass spectrometry). These three methods genuinely identify microplastics. Other approaches focus on counting particles and cannot reliably tell plastic from sand, mineral, or cotton.

For microplastics in water, the California State Water Board has published two reference methods. SWB-MP1-rev1 uses infrared spectroscopy and is validated for particles larger than 50 micrometers (µm) up to 5,000 µm. SWB-MP2-rev1 uses Raman spectroscopy and is validated for particles larger than 20 µm up to 5,000 µm. ISO 16094-2:2025 and ISO 24187:2023 provide international reference frameworks, and each application still needs its own method suitability work.

The 1–20 µm size range is not validated under either California method, and no method reliably reaches nanoplastics. Method choice sets the boundaries for what a “none detected” result can honestly say.

How To Evaluate A Laboratory Before You Test

Some laboratories can support defensible claims, and others cannot. Use this six-step framework before you spend money on testing.

1. Verify accreditation scope. ISO/IEC 17025 accreditation applies method by method and site by site. A lab can hold accreditation and still run a specific test outside its published scope. To verify accreditation, check the accreditation body’s public directory. In the U.S., bodies such as A2LA and ANAB maintain searchable listings. Confirm that the specific method and matrix appear. For drinking-water microplastics, California ELAP accreditation is a strong signal. Because a scanned certificate can be outdated, altered, or tied to a different site, always confirm status in the live directory.
2. Assess method validation. Confirm that the lab uses methods validated for your exact product matrix. A lab may be accredited for one method family and still perform related work under internal controls outside the formal scope. A method validated for one matrix, such as bottled water, does not automatically apply to another, such as juice or supplements.
3. Review demonstrated experience. Look for labs with specific microplastics experience. General polymer testing experience does not guarantee sound microplastics work. Some microplastics testing is carried out by people with limited analytical chemistry training who skip basic steps in sampling, preparation, and measurement. Ask about experience with your product type and matrix.
4. Examine contamination controls. Ask about blanks, spike recoveries, and replicates. Blanks are samples run alongside your product to measure background contamination. Spike recoveries confirm that the method can detect what it claims to detect. Replicates are repeated measurements that confirm consistency. These controls matter because the lab environment itself can introduce contamination. Lab gloves can shed particles that look like microplastics and inflate counts in environmental samples. A lab that cannot document blank results cannot support a defensible non-detect claim.
5. Confirm chain of custody. Chain of custody is the written record of sample handling from collection through analysis to the final report. Check that documentation exists at every step. Any break in chain of custody weakens the traceability of the result.
6. Verify data recency. Testing must reflect current production. A clean result on one lot applies only to that lot. It does not guarantee future runs or other SKUs, and it does not cover a different production period.

How To Read “None Detected” In A Lab Report

“None detected” is one of the most misunderstood phrases in plastic testing. It means the method did not find particles above its detection floor for the polymers it checked in the lot it tested. It does not mean the product contains zero plastic.

A microplastic report without a stated detection limit should not guide claims. Without that number, the result quietly overstates what the method can support. The detection limit is the lowest concentration the method can reliably separate from background noise. The reporting limit is the level above which the lab reports a number. Both values frame every finding.

When you review a lab report, use this checklist:

• Was the method appropriate for the product matrix?
• Were blanks run and reported?
• What is the reporting limit, and does it match the needs of the claim?
• What polymer panel was tested, and does it at least include PE, PP, PET, PS, PVC, PA, PC, and PMMA?
• What particle-size range did the method cover, and does that range match the claim?
• Were spike recoveries and replicates documented?
• Is chain of custody complete from sample collection through analysis?
• Does the data cover the specific product and production period in the claim language?

LOD and LOQ, the limit of detection and limit of quantitation, are specific to each method and matrix. Labs must calculate them, verify them experimentally, and document them with full traceability. A “none detected” result without these values cannot support a strong claim.

Common Claim Mistakes To Avoid

Several recurring errors weaken plastic-related claims, even when the testing itself is real.

• Overclaiming from a non-detect result. Claiming or implying “plastic-free” based on a non-detect result ignores the detection floor. The result is limited by the method, not by the total content of the product.
• Ignoring the particle-size gap. Particles found in human blood, placenta, and brain tissue often fall below the detection floors of common water tests, typically 1–10 µm. A “none detected” result at 20 or 50 µm says nothing about that smaller and more concerning fraction.
• Using a lab without proper accreditation. “ISO 17025 compliant” is a self-declared label. “ISO 17025 accredited” means an accreditation body has assessed and confirmed performance. These claims are not equivalent.
• Skipping or hiding blanks. Failure to run and interpret blanks can exaggerate or hide microplastics in a product. Background contamination from the lab environment can distort results in either direction.
• Stretching one result across products or time. One tested lot supports one claim about that lot. It does not cover other SKUs, other batches, or the entire brand.
• Treating a lab report as a finished claim. Weak sampling plans, wrong specimen geometry, or inconsistent conditioning can undermine accurate instrument readings. Even a technically sound report still needs independent interpretation before it becomes a market statement.

A lab can only report that it did not find particles above a certain size, for a defined polymer panel, in a specific lot. Claims must stay within those boundaries.

Learn how to reduce plastic exposure and explore plastic-free verification options for your company.

When To Bring In Independent Review

Independent review is a separate service from laboratory testing. Even with a strong lab and a clean report, brands still need an independent party to compare data against a clear standard before they make claims.

Testing generates numbers. Independent review checks whether those numbers are credible, whether the method fits the matrix, whether blanks and controls were run, and which claims the data can support without overreach.

The Wellness Quality Institute (WQI) is an independent verification body that reviews companies’ third-party lab data on plastic and microplastic content against a defined standard, WQI-CS-01. This standard aligns with the California State Water Board’s drinking-water microplastics reference framework and explains the technical concepts in everyday language for brands and consumers.

WQI does not run laboratory tests. That separation keeps its review independent from the testing it evaluates and strengthens trust in the outcome.

WQI’s Plastic-Free Pathway Verification program has two possible outcomes. A Standard Met outcome provides approved claim language, a scope-locked license to use the WQI mark, and a public registry listing that allows anyone to check the claim. A Standard Not Met outcome remains private, and the company can resubmit with updated information.

Verification applies only to the reviewed product, dataset, tested particle-size range, polymer panel, and production period. It does not extend to an entire company or product line.

WQI Plastic-Free Pathway Verification does not certify that a product contains zero plastic, microplastics, or nanoplastics. It confirms that the company follows 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. WQI verification is not a California approval, government certification, or health or safety certification.

Frequently Asked Questions

What Is Independent Laboratory Plastic Testing?

Independent laboratory plastic testing means a third-party lab with no commercial stake in the outcome analyzes your product. The brand does not test its own product in-house. Independence reduces conflicts of interest and increases trust with retailers, regulators, and litigators. Many buyers now expect this level of testing. Independent review then checks the data against a standard and explains what the results support.

Why Is Independence Important In Plastic Testing?

Self-reported results often look like marketing, even when the science is solid. ISO/IEC 17025:2017 requires labs to manage risks to impartiality, yet true independence also means the lab has no financial reason to prefer any outcome. An independent reviewer examines data without having run the tests and without a commercial tie to the result. That separation turns a lab report into a finding the market can trust.

What Standards Apply To Plastic Testing?

Common standards include ASTM D638 and ISO 527 for tensile properties, ASTM D790 and ISO 178 for flexural properties, and ASTM D256 for impact resistance. For microplastics, the California State Water Board’s SWB-MP1-rev1 and SWB-MP2-rev1 provide a leading public reference. As noted earlier, these methods are validated only above 50 µm and 20 µm respectively. ISO 16094-2:2025 and ISO 24187:2023 offer international frameworks, and each use case still needs its own method suitability work.

What Does “None Detected” Mean In A Lab Report?

As explained earlier, “none detected” is limited by the method’s detection limits, the particle-size range, and the polymer panel the lab tested. A method validated above 20 or 50 µm cannot see smaller particles. A report without a stated detection limit overstates what the method can support. The detection limit defines the boundary of the claim.

Conclusion: Turn Lab Results Into Claims You Can Defend

A lab report tells you what the lab measured. It does not, by itself, tell the market what that finding supports. Independence matters in the lab that runs the tests and in the review that translates data into clear, honest claims.

Accreditation scope, method validation, contamination controls, and data recency all play a role. Independent review against a defined standard then connects those pieces to your packaging, website, and retailer submissions.

Next steps are direct. Compare your current lab data against the checklists in this guide. If you plan new testing, confirm laboratory qualifications before you invest. When you are ready to turn real data into claims you can stand behind, work with an independent reviewer.

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

Read Next

• Independent Review of Laboratory Plastic Testing
• How To Evaluate Lab Results for Plastic Marketing Claims
• How to Verify Plastic-Related Claims Using Lab Data
• What Microplastics Testing Proves and Where It Stops
• Microplastics Claims: Independent Dataset Review Explained