Per- or Poly-fluoro-alkyl substances (PFAs). They’ve been in the news of late.
This post is a quick refresher on PFAs. For me. I’m just trying to get my facts straight before seeing if a need to change anything in my life to try to avoid PFAs.
Short answer is no, but more from lack of information than for any positive reason.
Part 1: An easily-digested chemistry lesson.
Source: An on-line chemistry course from Western Oregon University.
Alkanes are chemicals consisting of nothing but carbon and hydrogen, where the carbon atoms are “saturated” with hydrogen. (That is, there are no high-energy “double bonds” or “triple bonds” among the carbon atoms.) The carbons can be arranged in a straight chain, a branched chain, or some form of circle. You are already know the names of some common straight-chain alkanes, above.
Aside from the fact that we can burn them as fuel, most common alkanes are unremarkable. These substances are produced routinely in nature (insert fart joke here) and will break down naturally. For example, the half-life of methane in the atmosphere is somewhere around 10 years.
But if you can take those run-of-the-mill alkanes, and somehow substitute fluorine atoms for hydrogen atoms … magic happens.
For example, the single most-common plastic in the world — polyethylene — found in milk jugs world-wide, becomes the slickest substances in the world — Teflon.
The quick upshot is that whenever you substitute fluorine for hydrogen in these long-chain carbon compounds, there’s a good chance you’ll end up with something that’s pretty cool. Something that is:
- completely inert (Halon). or
- works as a refrigerant (Freon), or
- produces a nearly-frictionless surface (Teflon), or
- makes fabric waterproof and oil-proof (Scotchguard)
The root of all of that is this:
Source: Chemtalk.
All these magical properties — inert, un-wettable, nearly frictionless — derive from the same source. Fluorine is the most electro-negative element in the known universe. That is, among all the elements, fluorine has the strongest attraction to electrons held by other atoms.
The upshot is that if you can manage to get fluorine to bond with carbon, it stays bound. It takes a large amount of energy to break that bond, precisely because fluorine wants to hold onto those carbon electrons more than any other element does. Better yet, that property of being tightly bound spreads to the adjacent carbon atoms, to some degree, so that much of the entire molecule is really strongly stuck together.
It is no small trick to create fluorocarbons in the first place. It takes more energy to get a fluorine atom hooked onto a carbon than it takes to get any other suitable element to do that.
This is why there are almost no naturally-occurring fluorocarbons. I just read that the count stands at 30 such, in all of nature. And many of the naturally occurring fluorocarbons are produced by a single family of exotic tropical plants. You are guaranteed scientific publication if you discover a new one. Correspondingly, nothing in nature has evolved to digest or decompose or otherwise deal with fluoro-carbon compounds, which is why all the plants in that family are incredibly toxic.
Sometime, when you want to feel uncomfortable, read up up what happens if you have any significant contact with hydrofluoric acid. That intrinsic property of free fluorine is part of the problem.
In short, once you manage to substitute fluorine for hydrogen in a carbon compound, you end up with something that doesn’t want to interact with any other chemicals. Not water. Not oil. Not nothin. The very properties that make PFAs desirable as industrial chemicals — inert, waterproof, oil-proof, slick — make them virtually indestructible in the natural environment.
In any case, given their properties, it’s not too surprising that we use a lot of them. I see a 2021 estimate from the EPA that we produce at least 85,000 tons of PFAs in the U.S. annually (Source: EPA-821-R-21-004, Page 5-3). If I did the math right, that’s (85,000 x 2000/330,000,000 =) at least a half-pound per person per year, in the U.S. And I’m pretty sure that was a partial inventory.
2: PFAs: The best of Freon and DDT.
Source: Socratic.org
“If those chemicals don’t break down under ordinary conditions”, you might reasonably ask, “then where do they end up?”
Seems like modern industrial society has asked that question a number of times now. And, somehow, the answer is never good.
Start with Freon. Any flavor of Freon. If Freon is inert, where does it end up? The answer for Freon is that it only diffuses into the air, until, some decades after it was released at ground level, it gets broken up by high-energy UV-C radiation in the upper atmosphere. There, the fragments of that former Freon turn out to be quite good at thinning out the earth’s protective ozone layer.
The twist for PFAs is that they start with the same near-indestructibility of Freon, and tack on the food-chain-accumulation properties of DDT. And in this case, we’re squarely at the top of that food chain. In addition, PFAs are eliminated from the body quite slowly — I see casual estimates of two to ten years. Given all that, it’s no surprise to find that 97% of Americans have detectable levels of PFAs in their blood, based on the National Health and Nutrition Examination Survey circa 2007.
Having high levels of this stuff in your blood — say from occupational exposure, or consuming something heavily contaminated — is undoubtedly bad. I’m not so clear on what the expected health effects would be at typical population exposures.
Part 3: Action items?
To cut to the chase, no, not really.
You can find advice in this area, but it all appears to be, of necessity, total guesswork. The fundamental problem is that there is no good assessment of where typical population exposure comes from. Not that I could find, anyway. Which means that you have no way to know what’s actually worth avoiding, and what’s somebody’s list of things that might contain PFAs.
For some of these, though, it’s clear that when the Feds started getting them out of consumer products, the average concentration in the blood of Americans began to fall. Like so, from the CDC, showing U.S. population blood levels of PFOS (perfluorooctane sulfonate, top line) after the EPA orchestrated a phase-out of use of that chemical in the US.
Source: US CDC
On the typical list of things to avoid, you’ll see Teflon frying pans and stain-proof/waterproof fabrics. I’m not sure about the extent to which the PFAs in those types of products actually end up in your blood.
But there’s a surprising amount of common skin-contact and food-contact material that may have more mobile sources of PFAs in it.
Waterproof cosmetics and sunblocks are on everybody’s list. Although I sure can’t find any that plainly contain -fluro- chemicals listed. I just checked a couple of bottles here, and many examples on Amazon, and I see nothing that I would recognize as a PFA. Plausibly, if those contain PFAs, they are inactive ingredients, and so typically aren’t listed?
But also grease-resistant food packaging, including pizza boxes, french-fry bags, hamburger wrappers, paper plates, microwave popcorn bags, and so on. Basically, a whole lot of stuff associated with take-out food. All because a lot of grease-proof paper/cardboard coatings contain PFAs. This Consumer Reports article was illuminating, and names names among fast-food restaurants.
Some cooking parchment paper has PFAs to make it extra slick. Some cleaners and waxes have PFAs.
But aside from “don’t eat fast food”, none of that seems terribly actionable.
For drinking water, of course this stuff is in drinking water. At least here, where around 10% of what’s flowing past the water intakes here in the Potomac River at Washington, DC came out of some sewage-treatment plant somewhere upstream.
It appears that either activated-charcoal or reverse-osmosis filters will remove PFAs. (That makes sense, because both of those technologies are good at removing large organic molecules.) No pitcher-type water filters remove PFAs. Oddly, I read that distilling water doesn’t remove PFAs either, though I have no idea why not.
4: Conclusion
My interest on PFAs was piqued by NY Times reporting that sewage sludge used as fertilizer passes PFAs from the sewage stream onto the land, to the plants grown on the land, to (in this case) the cows that eat those plants, and ultimately to people.
This is not news, really. There have been several EPA actions on PFAs, including cajoling industry into phasing out what appeared to be the worst PFAs. Even a cursory look shows a long history of EPA interest in monitoring these chemicals.
What caught my eye is the case of a farmer whose land was condemned for food production, due to toxic levels of PFAs in the soil, toxic enough to sicken the cattle grazing on that land. This, where the only plausible source for those PFAs is sewage sludge that has been spread on that soil. And since PFAs don’t break down, for all intents and purposes, the land is forever condemned for food production.
That’s unusual. Or, at least, you rarely hear of that out side of EPA Superfund sites.
But in terms of action items, for avoiding eating and drinking PFAs, I’m not seeing a lot of quantitative advice on what to do.
So, in the absence of any better information, I’m just going to put this one on my list of all the things I dislike about the modern world, but that I can’t do anything about.
