The lab results behind the Kerrygold PFAS wrapper story

Kerrygold shows up in almost every "clean grocery list" — grass-fed, Irish, the butter people buy specifically to get away from processed food. So when a fact-check on a viral reel led back to an actual lab report, it was worth pulling the number itself instead of trusting a screenshot. Here is what the lab found, what the law says about it, and what the company did about it.

What was tested, and by whom

Mamavation, a consumer research group that regularly commissions independent lab testing on food and packaging, sent Kerrygold Pure Irish Butter wrappers to an EPA-certified lab. The lab did not test the butter itself — it tested the paper and foil the butter sits in — for total fluorine, using Determination of Total Fluorine by Oxygen Flask Combustion and Ion-Selective Electrode. When a sample showed detectable total fluorine, the lab ran a second pass to isolate organic fluorine, which is the standard screening marker researchers use as a proxy for PFAS ("forever chemicals") in a material, since PFAS compounds are built around carbon-fluorine bonds that don't occur naturally at these levels.

The lab's detection floor on this method was 10 ppm. Anything reported above that is a real, quantified result, not background noise.

The lab results

Mamavation doesn't publish the original certificate of analysis for these samples — the underlying report sits behind their membership wall, and we're not going to fabricate a scan of a document we don't have. What follows is our table, built from the analyte, method, detection limit and result figures the outlet has published and stood behind in the article text since 2023, laid out the way a lab report presents them:

Lab: EPA-certified laboratory commissioned by Mamavation (lab name not disclosed in the published report). Sample IDs above are our own labels for readability, not the lab's internal identifiers — Mamavation's article does not publish those. Data source: Mamavation, "Butter Wrappers & Indications of PFAS 'Forever Chemicals' — Buying Guide". The same figures were separately cited in the resulting litigation (below).

For scale: 10 ppm is the lab's detection limit, meaning it's roughly the smallest amount the method can reliably tell apart from zero. A result of 122 ppm is more than twelve times that floor. That's not measurement drift — it's a quantity that's actually in the wrapper.

Why 100 ppm is the number that matters

California's AB 1200, the Safer Food Packaging and Cookware Act, took effect January 1, 2023. It bans selling plant-fiber food packaging in the state that contains "regulated PFAS" — defined as either PFAS intentionally added for a functional effect, or PFAS present at 100 ppm or more of total organic fluorine, whichever trips first. New York passed an equivalent packaging restriction that landed the same window, effective December 31, 2022.

Run the original Kerrygold numbers against that line:

• Unsalted (61 ppm) — under the 100 ppm threshold, but six times the lab's detection floor.
• Salted (122 ppm) — over the 100 ppm threshold on its own, no other sample or average required.

That's the part that turned a lab result into a legal problem.

What actually happened next

The testing became the basis of a class action, Winans v. Ornua Foods North America, filed in a New York federal court in February 2023. The suit alleged Kerrygold's "Pure Irish Butter" marketing was misleading given what was in the wrapper touching the food. Kerrygold — made by the Irish dairy co-operative Ornua — pulled the product from shelves in New York and California in early 2023 rather than sell packaging that didn't meet the new state rules, then returned a couple of months later with reformulated packaging marketed in part on being PFAS-free.

Mamavation retested the new wrapper. It came back at 11 ppm organic fluorine — an 82% drop from the old unsalted foil wrapper, and safely under California's 100 ppm legal line. But 11 ppm is still above the lab's own 10 ppm detection floor. The fix moved the number out of legal violation, not down to non-detect.

The lawsuit itself didn't produce a verdict either way — a judge let the deceptive-labeling claims proceed, and the parties filed a stipulation dismissing the case with prejudice in August 2024, on terms that weren't made public. No finding of liability either direction. What's not in dispute is the lab numbers and the packaging change that followed them.

Why the wrapper is the part nobody checks

Grass-fed butter is exactly the kind of purchase where people feel like they've already done the diligence — Irish, pasture-raised, none of the corn-fed feedlot stuff. That's a real, checkable claim about what the cows ate. It says nothing about what the butter is wrapped in. The packaging isn't an ingredient, so it isn't on the ingredient list, and "Pure Irish Butter" as a phrase describes the contents, not the wrapper touching the contents. Nobody is misreading the label — there's just no line on the label that would tell you this.

Other butter brands in the same test batch

Kerrygold wasn't the only one Mamavation flagged. From the same investigation, brands that came back above the 10 ppm detection floor for organic fluorine included Kirkland Grass-fed Salted, Maple Hill Organic Grassfed, Organic Valley Sweet Cream, Land O'Lakes Salted, Wegmans Organic Unsalted, and HEB Organic Salted Sweet Cream — several with inconsistent results between samples of the same product, which is its own signal that the packaging supplier, not the recipe, is the variable.

Brands that came back non-detect in the same round of testing: Clover Sonoma, Straus Family Creamery, Horizon Organic, 365 Whole Foods, O Organics, Trader Joe's Organic, Kirkland Organic, Vital Farms, Nellie's Free Range, Cabot Natural Creamery, Grassland, Raw Farm, Truly Grassfed, and Sprouts store brand.

What to actually do about it

You can't lab-test your own groceries, and a wrapper testing PFAS-positive isn't something you can see, smell, or guess from the branding — the whole reason this took an EPA-certified lab to find is that it's invisible at the point of purchase. That's the gap Tallow is built for: scan a barcode and get the ingredient list broken down, additives flagged, and independent lab findings attached to the product when they exist, so a brand's story and what's actually been tested on that product are two separate things you can check before it's in your cart.

This article summarizes independent lab testing published by Mamavation and subsequent, publicly reported litigation, for consumer-information purposes. Allegations in a class action complaint are allegations, not findings of fact; the referenced case was dismissed with prejudice by stipulation, without any admission of liability by either party. Sources: Mamavation buying guide, Mamavation original Kerrygold lab results, California AB 1200 bill text, and ClassAction.org coverage of Winans v. Ornua Foods North America.