PFAS: A Short Summary
May 30th, 2022
I wrote this piece with the intention of giving a broad and brief overview of what PFAS are. PFAS are probably a chemical you’ve seen in the news recently. If you haven’t yet… you probably will soon. It’s a topic that’s near and dear, I ‘ve spent the last 7 years of my life studying them… so figuring out what to not put in was the more difficult part. I did not include any regulatory information because it’s an ongoing process with both federal and state governments weighing in. I don’t want to have to go back and edit this post every couple weeks. As with anything in science, the information here is incomplete, lacks nuance, and may likely change in a few years.
If anyone would like more information on any aspect of this post, want some clarification, or would like citations for anything I mention, feel free to ask, I’ll see what I can do. I’m more than happy to add to the post or write a new one on the topic.
Pure laboratory grade PFOS
Per- and poly-fluoro alkyl substances (PFAS) are very diverse chemical class of over 3,000 organic compounds. PFAS are of global regulatory interest due to their environmental persistence and mobility, tendency to bioaccumulate, and potential toxicity towards humans and wildlife. PFAS are completely anthropogenic, meaning they are only man made and do not naturally occur. Being part of a large group, PFAS can have many desirable chemical traits, but in general they are used because they are both oil and water resistant, durable and long lasting, non-reactive, and surfactant qualities (they coat surfaces they are applied to). They have been used in clothing, furniture, cookware, firefighting materials, packaging, electronics, aerospace equipment, and many other products over the last six decades.
Within the PFAS class, the sub-group perfluoro alkyl acids (PFAAs) have received most regulatory and research attention. The reasons for this are, loosely, that they were historically used more often, they are the most environmentally stable (many aren’t believed to significantly environmentally degrade), many other PFAS that do actually degrade tend to eventually degrade into PFAAs, and PFAAs tend to be the most toxic and bioaccumulative. Perfluorooctane sulfonate (C8F17SO3H, PFOS) and Perfluorooctanoic acid (C7F15COOH, PFOA) are the most notorious members of this group. You’ve likely seen products, like non-stick pans, displaying that they are PFOS or PFOA free. PFAAs have been detected in blood serum of nearly all tested individuals in several countries around the world. To date, most of the global environmental regulatory focus has been on PFAAs, primarily PFOS and PFOA, although in the last few years focus has expanded to more PFAAs and PFASs.
PFAS environmental contamination is typically associated with historic aqueous firefighting foams (AFFF) use, PFAS production and use, and waste treatment byproducts and sites. PFAS contamination is rarely a single congener, but rather a mixture. Once in the environment, PFAS are somewhat inert. Like many other environmental contaminants, the more water soluble the PFAS is, the more environmental mobility it has.
As I said earlier, many PFAS (the ones that actually do degrade) are chemically, environmentally, and biologically degraded into a variety of PFAAs like PFOA, PFOS, and perfluorohexanesulfonic acid (C6F13SO3H, PFHxS). Hence, due to PFAS degradation into PFOA and PFOS, locations that may meet PFOA and PFOS health advisory or regulatory standards one year may exceed them the next. “Precursor” or “unknown” fraction are common terms for these PFAS. I personally think this topic is pretty interesting, so I’ll probably dedicate a post to it in the future.
Dietary exposure to PFAS has been identified as the dominant exposure pathway for the general population. PFAS have been detected in a variety of fruits, vegetables, seeds, meats, dairy, and processed food products in and around the world. PFAS have been shown to be taken up and accumulated by plants from contaminated water and soil. Additionally, PFAS have been used extensively in packaging and processing material due to their ability to be both lipid and water resistant. PFAS use in food packaging can contribute to potential PFAS exposure from consuming that food.
As you can imagine, describing the toxicity of a group of chemicals that has 3000 members in a paragraph is bound to come up short in multiple ways. This is going to be very general, and most of the available information is from research on PFOS and PFOA. An important factor to keep in mind with PFAS toxicity is that many PFAS have extraordinary long biological half-lives (PFOS – 5.4 years, PFOA – 3.8 years. PFHxS – 8.5 years, PFBS – 25.8 days). A half-life is the time for half of a chemical to degrade or be removed, so with half-lives of 5+ years, even a small exposure to PFAS can be a decade long ordeal. Essentially, all humans currently have PFAS in their system, and have always had PFAS in their system, so pinpointing toxicity can be very difficult. PFAS disrupt lipid and cholesterol metabolism, leading to higher average body fat percentages and higher cholesterol. Human PFAS exposure may also be correlated with thyroid disruption, lower testosterone levels, weakened immune system, higher rates of vaccine failures, some cancers, and developmental disruption.
Learn more about PFAS with our other posts:
PFAS: The EPA Updates Interim Drinking Water Advisories
Our Publications on PFAS:
Plant Uptake of Per- and Polyfluoroalkyl Acids under a Maximum Bioavailability Scenario
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