The PFAS Left Microwave Popcorn Bags. The Plastic Film Did Not.

The short answer

If you avoided microwave popcorn because of “forever chemicals”, the specific thing you were avoiding has largely been removed from American bags, and most of the internet has not caught up. That is worth knowing, and it is a real win for a regulatory process that rarely produces one.

It is also not the whole bag. A microwave popcorn bag is a laminate: paper on the outside, and bonded inside it a strip of plastic film with a microscopically thin layer of metal on it. That strip is the susceptor, and it exists because microwaves alone will not brown or sear anything. The susceptor converts microwave energy into direct heat, which is what gets the kernels to popping temperature. It is made of polyester — PET, the same polymer as a drinks bottle — and it is designed to get hotter than almost anything else in your kitchen while touching your food.

What actually changed in 2024

The FDA’s announcement on 28 February 2024 is the pivot point, and the wording matters more than the headline did. The agency said grease-proofing substances containing PFAS are no longer being sold by manufacturers for food-contact use in the US market. The named applications were fast-food wrappers, microwave popcorn bags, takeaway paperboard and pet food bags.

Three qualifications, all of which get flattened in most coverage:

• It was voluntary. The FDA obtained commitments from manufacturers in 2020 after a post-market safety assessment, and the companies exited the market — most of them ahead of the agreed date. That is a negotiated withdrawal, not a prohibition.
• It covered sales of the substances, not use of the packaging. Nothing was recalled. Packaging already manufactured was not withdrawn, and there was no testing programme attached to confirm what left the supply chain or when.
• It is a US measure. It says nothing about bags made for or sold in other markets.

So the accurate sentence is: the grease-proofing PFAS that defined this product’s reputation should be gone from bags manufactured for the US market since roughly 2024, on the manufacturers’ word, with no independent verification programme behind it. That is considerably better than where things stood in 2019. It is not the same as proven absence.

Why the famous statistic is now a historical one

Nearly every article on this subject cites the same finding: people who eat microwave popcorn have markedly higher PFAS in their blood, with daily eaters running up to 63% above average. It comes from Susmann and colleagues at the Silent Spring Institute, published in Environmental Health Perspectives in 2019, and it is a good study — a nationally representative sample, serum measurements paired with dietary recall, several PFAS compounds moving together.

The detail that gets dropped is the window. The analysis used NHANES data from 2003 to 2014. Every blood sample in it was drawn while the grease-proofing coatings were still in normal commercial use. The study is strong evidence that those coatings reached people. It is not evidence about a bag bought this year, and presenting it as though it were is the single most common mistake in the coverage.

Nobody has repeated it post-phase-out. That is the study worth wanting, and until it exists the honest position is that the exposure route was real and the coating is reported gone.

What a 2025 test of actual bags found

The most recent laboratory work is Hsu and colleagues at National Cheng Kung University, published in Molecules in 2025. They bought five microwave popcorn bags from online stores in Taiwan and measured what migrated out of them into food simulants — 10% and 50% ethanol, held at 70 °C for two hours.

They identified seven PFAS — PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnA and PFDoA — migrating at concentrations from 5.2 ng/g up to 274 ng/g, the highest being PFOA from one sample into the 50% ethanol simulant.

Two things must be said about that before anyone panics. These were Taiwanese bags, not American ones, and the paper does not state whether they predate any phase-out. It is not evidence that US bags still leach PFAS. What it does show is that the problem was never globally solved by a US market agreement.

The finding underneath the finding

The most interesting result in that paper is not the concentrations. It is what happened when the authors ran the same measurements through two different regulatory risk frameworks.

Using the EFSA approach, which considers four PFAS, hazard ratios came out between 0.01 and 0.8 — every sample below the threshold, which the authors describe as suggesting minimal health risks. Using the EPA approach, which converts all detected PFAS into PFOA equivalents, the same five bags scored 0.3 to 142.3, with four of the five exceeding 1 and therefore indicating potential health concerns.

Same bags, same laboratory, same numbers going in — and the two major regulatory methods disagree by more than two orders of magnitude. That is not a flaw in the study; it is an honest picture of how unsettled PFAS risk assessment still is, and it is worth holding onto the next time you read a confident claim in either direction.

The part nobody covers: the susceptor

Strip the PFAS question out entirely and there is still a piece of plastic in the bag, by design, doing the hottest job in your kitchen.

A susceptor is a very thin layer of aluminium vapour-deposited onto a polyester film, laminated to the paper. Microwaves pass through paper and food but are absorbed by that metal layer, which converts the energy to heat. Without it, the kernels at the bottom of the bag would not reach popping temperature before the ones above them burned. Every microwave popcorn bag has one; so do the crisping sleeves on frozen sandwiches and pizzas.

The temperatures involved are the point. Pop Secret’s own FAQ states that the bag reaches around 450 °F when the moisture in the kernel turns to steam. That is 232 °C. Patent literature for susceptor packaging describes films reaching up to 500 °F (about 260 °C), with designs specifically engineered so the polyester adjacent to the susceptor does not exceed roughly 425–450 °F.

Set that against the polymer. PET melts at 255–265 °C, and thermal degradation begins near the melting point. A bag operating at 232 °C is running roughly 25–30 °C below the temperature at which the film it is made from starts to come apart — and the fact that manufacturers engineer an explicit ceiling into the design tells you they know exactly where that line is.

What we still do not know

• No one has counted microplastic particles from a popcorn bag. There is no published measurement of particle release from a susceptor film under real popping conditions. If you see a figure, it was invented. This is a mechanism worth studying, not a quantified exposure.
• No post-2024 serum study exists. Susmann tells us the old coatings reached blood. Nothing tells us what current US bags do.
• What replaced the PFAS is not disclosed. Bags still need to resist grease. The substitutes are not named on any package, and “PFAS-free” describes what a coating is not, rather than what it is.
• The laminate adhesive is undocumented. No consumer brand publishes it.

What to actually do

This is one of the rare cases where the swap is complete rather than incremental, and costs less than the thing it replaces:

• Loose kernels in a pot. Two tablespoons of oil, a lid, medium heat. No bag, no susceptor, no coating, and plain kernels are a fraction of the price per serving of the bagged version.
• An air popper if you want it hands-off. Check the chute material — many are plastic, but the kernels pass through in seconds rather than sitting against a 232 °C film.
• A glass bowl with a lid or plate in the microwave. Kernels, a plate on top, three minutes. It genuinely works and keeps the convenience.
• Not a silicone popper on the strength of the material alone. Silicone is more heat-stable than PET, but it is far less studied, and a bowl you already own solves the same problem.
• If you are keeping the bags, do not re-microwave one. The susceptor is designed for a single controlled heating cycle, and an empty or re-run bag is the condition that pushes the film past its intended ceiling.

Related reading: what “microwave safe” actually means, PFAS explained, microplastics vs PFAS vs BPA, can you microwave Ziploc bags, and microplastics in fast food.