Where Firefighter PFAS Exposure Actually Comes From
Or: it's the foam. It's pretty much entirely the foam.
Full disclosure, because it matters for this one in particular. I run the company that makes NeutraOat, a modified oat fiber built to pull PFAS out of your gut and your blood. So I am not a neutral party. I have a direct financial interest in you finishing this post worried.
I've tried to write it so you can check me instead of trusting me. Everything below has a link on it. And you'll notice that two of the three exposure routes people worry about come out of this looking a lot weaker than you've probably been told, which is not the post I'd write if I were optimizing for scaring you into buying something. If you'd rather skip ahead to the part where I sell you things, it's the free pilot if you're a firefighter or you live somewhere with confirmed contamination, and a $20 refundable reserve if you're neither.
Firefighters carry more PFAS in their blood than pretty much anybody who doesn't work at a chemical plant. Nobody disputes that. What I keep running into is that the why gets treated as equally settled, and it really isn't.
Almost every piece written on this lists the three routes in a row, foam and gear and skin, in a way that implies the evidence behind them is comparable. It isn't, and the gap is not small. One of them has decades of dose-response data plus an accidental natural experiment behind it. The second is a genuinely open question that a lot of people are pretending is closed, in both directions and for money. The third is a petri dish study with a very effective press office.
So, in order of how much I'd actually worry about it:
One thing worth saying before we go: PFAS do damage at doses most people would wave off as trace amounts. Firefighters stack a job-related dose on top of the background everybody already carries. If you want the argument for why small numbers still matter, it's here: PFAS are dangerous at low doses.
How much PFAS do firefighters actually have in their blood?
Let's start with the biomarker data, because it's the only part of this whole argument that isn't downstream of somebody's marketing department or somebody's lawsuit.
Studies out of the US, Australia, and Europe consistently find firefighters running higher than the general population. Not on every compound and not in every department, but two names keep coming up: PFOS and PFHxS. In some groups the longer-chain acids like PFDA climb with years on the job too.
The cleanest one I've found is Rotander 2015, which measured 149 Australian aviation firefighters who'd spent decades training with foam. Their average PFOS and PFHxS came in around six to ten times general-population levels, and the most exposed men were roughly ten times higher. But the detail that actually convinced me was this: the guys hired after the foam got reformulated, doing the same job in the same gear on the same burning jet fuel, tested basically normal.
Departments vary a lot, though, and I don't want to oversell how tidy this is. A volunteer group in New Jersey came in below the general population on PFOS. An Ohio group ran high on PFHxS and low on everything else. And PFOA, which gets most of the press, usually isn't elevated in firefighters at all. California's biomonitoring had firefighters at 3.75 ng/mL against 3.61 in the general public, which is a difference you could produce by rounding. File that one away. It comes back in the gear section.
AFFF firefighting foam: the one source with real evidence behind it
This is the one with real evidence behind it, and it isn't close.
AFFF has been in use since the 1960s for flammable liquid and fuel fires, i.e. the ones where spraying water just moves the fire around. It works by laying a film across the surface of the fuel so the vapors can't feed the flames, and the fluorosurfactants are the entire reason the film works at all. It ships as a 3 or 6 percent concentrate and gets proportioned into the water on the way out of the line.
The chemistry lines up with the blood, which is what you want to see and almost never get. Legacy AFFF, meaning the stuff made before roughly 2002, was PFOS-based. It carried PFOS and PFHxS directly, and PFOA turned up only as a byproduct. Those are exactly the compounds firefighters test high for. The later fluorotelomer formulations moved to shorter-chain surfactants, mostly 6:2 fluorotelomer sulfonate.
And the numbers scale with exposure. In the Australian cohorts, PFOS and PFHxS both went up with years of foam contact, and one group enrolled in a treatment program averaged something like 197 ng/mL PFOS and 60 ng/mL PFHxS, against a general public sitting in the low single digits. That is not a subtle effect.
So you have dose-response, a chemical fingerprint that matches the source, and a before-and-after when the source got swapped out. For occupational data that's about as strong as it ever gets short of a randomized trial, and nobody is going to randomize firefighters into a foam arm. If you use the foam, this is your exposure. Everything after this section is smaller.
Turnout gear: does the PFAS in it actually reach your blood?
Turnout gear is full of PFAS. Whether any meaningful amount of it gets into your bloodstream is a completely separate question, and the honest answer is that nobody knows. Which you'd never guess from the product marketing or from the lawsuits, since both of them are extremely confident and, conveniently, confident in opposite directions.
The story starts in Massachusetts in 2017. Diane Cotter noticed that the inside of her husband's turnout gear was falling apart while the outside looked fine. Her husband was a 28-year Worcester firefighter with advanced prostate cancer. She sent the gear to Graham Peaslee, a physicist at Notre Dame, who found the outer shell and moisture barrier of gear from six different manufacturers loaded with fluorine. His group went on to watch PFAS migrate inward toward the liner that sits against your skin, transfer onto gloved hands, and pile up in the dust of gear storage rooms.
All of that holds up. The gear is contaminated and it sheds. I want to be clear that I believe that part before I get to the part where I annoy people.
What nobody has managed to show is that it ends up in the firefighter. Two things keep me skeptical.
The first is the serum mismatch, which is the one that really gets me. Firefighters run high in PFOS and PFHxS, which come from foam. PFOA is the compound that keeps turning up in gear testing. PFOA is also the compound that mostly isn't elevated in firefighters' blood. If the gear were delivering a real dose, the gear's chemicals should be showing up in the serum, and they aren't.
The second is the one direct test we have. When somebody finally went looking for a gear-to-blood link on purpose, a 2026 study on used turnout gear worn during training, what they got was trace PFOS in one sample and nothing else. That study didn't cover the most volatile PFAS, so I wouldn't call it the last word. But it points the same direction as the biomarker data, and at some point two independent things pointing the same way is worth something.
So what we've got is a confirmed contamination source with a completely unconfirmed dose. Keep it off your skin, keep it out of the room you sleep in, sure. That's cheap and obviously correct. I just don't think it's the emergency it's being sold as, and I'd point out that I'm saying that against my own commercial interest.
Worth knowing about this particular fight, too: a lot of the "the gear is fine" research traces back to scientists with PPE manufacturer ties, and a lot of the alarm traces back to law firms with active cases. Everybody arguing about this needs a specific answer to be true. Me included. Which is the whole reason I keep dragging you back to the blood data, because it's the only thing here that nobody has an angle on.
Does turnout gear off-gas PFAS when it gets hot?
Off-gassing is the adjacent worry: volatile PFAS evaporating off hot gear and getting breathed in. Gear does contain some volatile PFAS, so it's not a crazy thing to wonder about.
The number that gets quoted here is 122,000 mg F/kg of "total fluorine," which sounds enormous because it is enormous. It's also almost entirely PTFE, an inert plastic that sits in the fabric and goes nowhere. The fraction that can actually evaporate is closer to 20 mg F/kg. So the scary number is something like six thousand times bigger than the number that could plausibly reach you, which is a good thing to remember any time somebody quotes you a total fluorine figure.
And even the 20 isn't a dose. Something being present and volatile doesn't tell you how much of it ends up in a person, and nobody has tied gear off-gassing to a measurable change in anyone's blood. Reasonable hypothesis, untested.
Can PFAS be absorbed through your skin? What the 2024 study did and didn't show
This is the weakest of the three by a wide margin, and it's where the coverage got furthest out ahead of the actual finding.
The skin route used to get dismissed, for a decent mechanistic reason. Most PFAS carry a charge, and charged molecules aren't supposed to make it through the fatty barrier of the stratum corneum. Then in 2024 a group at Birmingham applied 17 PFAS to lab-grown human skin and 15 of them went through, with about 13.5% of the PFOA crossing and the shorter chains moving more easily. That's a real result and I'm glad somebody ran it.
It is not evidence that firefighters are absorbing PFAS through their skin. Four reasons:
- It's lab-grown skin. These models are thinner and leakier than the real thing, and outside experts said so at the time.
- The authors wouldn't make the jump themselves. The lead author said she couldn't conclude the PFAS would reach the bloodstream of a living person. Getting across a membrane in a dish is one step out of several. The doses were also well above anything you'd actually encounter.
- The older literature points the other way. Earlier PFOA work found it could park in the skin while almost none of it moved into blood.
- Firefighters don't show the pattern. Rotander went looking for a relationship between self-reported skin contact with foam and blood PFOS and didn't find one. If skin were a major route, that relationship should be sitting right there in a cohort of men who'd been handling the stuff for thirty years.
Real in a dish. Plausible in a person. Nobody has ever measured it in a firefighter. I'd file it under "worth another study" rather than "reason to change what you do tomorrow," and I'd be suspicious of anybody selling you something on the strength of it. Including me.
How long do PFAS stay in your blood?
The reason exposure history matters so much here is that PFAS just don't leave. In the Australian firefighters, serum half-lives ran about 5 years for PFOA, 6.5 for PFOS, and 7.8 for PFHxS. ATSDR gives a range of 2 to 27 years across the class, which is wide enough that I'd treat any single number with suspicion, but they're all long.
This is the bit I think people underrate. If something takes seven years to half-clear, twenty years of exposure isn't twenty separate doses. Each one is still mostly sitting there when the next one lands. You aren't drinking twenty beers over twenty years, you're filling a bathtub with a mostly-plugged drain. By the end of a career there's a real body burden in your serum, and it's going to stay there for a while no matter what you do about your gear.
Do PFAS cause cancer in firefighters? Sort of, probably, with caveats
Two IARC rulings frame this. In 2022, IARC put the job itself into Group 1, carcinogenic to humans, on solid evidence for mesothelioma and bladder cancer. In November 2023 it put PFOA in Group 1 and PFOS in Group 2B. NIOSH data has firefighters about 9% above the general public on cancer diagnoses and 14% above on cancer deaths, and the IAFF calls occupational cancer the leading cause of line-of-duty death.
Now the caveats, and there are a couple of real ones.
IARC classifies hazard, not risk. Group 1 means the thing can cause cancer under some set of conditions, not that your particular dose will. Processed meat is Group 1. So is sunlight. It's a useful category that routinely gets read as much scarier than it's meant to be, and some toxicologists think IARC pushed the PFOA and PFOS evidence past where it goes.
The bigger caveat is that firefighters inhale an enormous amount of other things that cause cancer. Combustion products, diesel exhaust, benzene, asbestos in older buildings. You can't look at a 9% excess and hand it to PFAS, and I'm not going to pretend you can. PFAS is one contributor. The blood work says it's a real one. It doesn't say it's the main one, and if I had to bet, I'd guess the smoke is doing more.
How to reduce PFAS exposure and lower the levels you already have
Most of what holds up is what the fire service is already telling you:
- Keep foam and dirty gear off your skin.
- Decon after a fire.
- Store gear somewhere other than where you sleep, eat, or drive.
- Move to fluorine-free foam and PFAS-free gear as you can get them.
For what's already circulating in you, the only intervention I know of with a randomized trial behind it is blood and plasma donation, which produced measurable drops in serum PFAS. That's a low bar that nothing else in this category has cleared, and if you're a firefighter with high levels you should be donating whether or not you ever buy anything from me.
What donation doesn't solve is speed. It comes off slowly, and if you're still running foam you're refilling faster than a seven-year half-life can empty. That gap is why my company exists, and it's also why I'd rather you understood the foam properly than came away vaguely afraid of your jacket.
If you want to do something about your own levels
- If you work in or live somewhere with confirmed high PFAS, firefighters very much included, look at the NeutraOat pilot. If you qualify you get 12 weeks of NeutraOat free, plus before and after PFAS tests and blood panels.
- If you're not a firefighter and you're not on a contaminated water system, you can reserve a spot in the first commercial batch, shipping this fall. It's a $20 refundable deposit, which funds the batch and shows our investors that people actually want this.
This is information, not medical advice. Nothing here says any product prevents, treats, or cures cancer or any other disease. If you have questions about your own exposure, talk to an occupational medicine doctor.