A Perfluorinated Fiasco

Good gravy. What a freakin’ mess. It seems like everywhere investigators look, they find perfluorinated alkyl residues- drinking water, fish, people, etc. These fluorinated substances are known as PFAS, PFOS, PFOA, PFHxS or perfluorohexane sulfonic acid, and PFNA or perfluorononanoic acid. The “per” in front of perfluorinated just means that the molecule has as many fluorine atoms connected as possible.

According to the National Association for Surface Finishing, PFAS “properties are useful to the performance of hundreds of industrial applications and consumer products such as carpeting, apparels, upholstery, food paper wrappings, wire and cable coatings and in the manufacturing of semiconductors.“

I will use the term “PFAS” to represent any and all of variations in this small molecule category of perfluorinated substances.

The EPA has kicked into overdrive and is ginning up new regulations, including drinking water standards. “EPA’s proposal, if finalized, would regulate PFOA and PFOS as individual contaminants, and will regulate four other PFAS – PFNA, PFHxS, PFBS, and GenX Chemicals – as a mixture … PFOA and PFOS: EPA is proposing to regulate PFOA and PFOS at a level they can be reliably measured at 4 parts per trillion.” This is around the detection limit for these compounds.

From an EPA website–

PFAS can be present in our water, soil, air, and food as well as in materials found in our homes or workplaces, including:

• Drinking water – in public drinking water systems and private drinking water wells.
• Soil and water at or near waste sites – at landfills, disposal sites, and hazardous waste sites such as those that fall under the federal Superfund and Resource Conservation and Recovery Act programs.
• Fire extinguishing foam – in aqueous film-forming foams (or AFFFs) used to extinguish flammable liquid-based fires.  Such foams are used in training and emergency response events at airports, shipyards, military bases, firefighting training facilities, chemical plants, and refineries.
• Manufacturing or chemical production facilities that produce or use PFAS – for example at chrome plating, electronics, and certain textile and paper manufacturers.
• Food – for example in fish caught from water contaminated by PFAS and dairy products from livestock exposed to PFAS.
• Food packaging – for example in grease-resistant paper, fast food containers/wrappers, microwave popcorn bags, pizza boxes, and candy wrappers.
• Household products and dust – for example in stain and water-repellent used on carpets, upholstery, clothing, and other fabrics; cleaning products; non-stick cookware; paints, varnishes, and sealants.
• Personal care products – for example in certain shampoo, dental floss, and cosmetics.
• Biosolids – for example fertilizer from wastewater treatment plants that is used on agricultural lands can affect ground and surface water and animals that graze on the land.

Details on specific molecular pharmacology mechanisms are a bit thin. The perfluorinated part of PFAS is chemically quite inert and very hydrophobic, but often the perfluorinated group is connected to something polar like a carboxylic acid as with PFOA which can give surfactant properties. Most of the utility of PFAS comes from the fluorinated part. About the only way to get a chemical reaction with perfluorinated organic hydrocarbons is to contact them with alkali metals like sodium or potassium, or even with magnesium or aluminum. The last two are probably less reactive than the alkali metals. The good news is, precious few have alkali metals lying around to blunder into contact with Teflon^TM.

All of this toxicity talk seems to be at the “increased this” or “decreased that” correlation stage presently. Another table from the EPA website-

Current peer-reviewed scientific studies have shown that exposure to certain levels of PFAS may lead to:

• Reproductive effects such as decreased fertility or increased high blood pressure in pregnant women.
• Developmental effects or delays in children, including low birth weight, accelerated puberty, bone variations, or behavioral changes.
• Increased risk of some cancers, including prostate, kidney, and testicular cancers.
• Reduced ability of the body’s immune system to fight infections, including reduced vaccine response.
• Interference with the body’s natural hormones.
• Increased cholesterol levels and/or risk of obesity.

Along the way to the consumer are the PFAS chemical manufacturers and their customers that formulate the PFAS into their products. Then there are the retailers who sell PFAS-loaded products to the consumer. The benefits of perfluorinated materials are often revealed as claims for non-stick, repellency or fire retardancy. At some point the whole chain will have to back off on their repellency marketing.

Just for fun, the only substance that a gecko’s foot cannot stick to is PTFE.

So, should all use of PFAS substances be abolished? I think that applications can be prioritized according to relative importance. Fire retardancy is a health and safety related use and is a very important attribute in certain circumstances like fire extinguishing agents. Liquid fuel fires are special because spraying water on burning fuel will result in the fuel floating on top of water and continuing to burn. Foam is used because it can float on top of the fuel and smother it. A thoughtful evaluation of retaining PFAS agents for a select few applications like fire suppression should be made.

Using PFAS to prevent grease stains from soaking through fast food wrappers, water repellency or stain resistance on carpets is likely a basket of applications that we can live without.

In doing background reading for this I found something very interesting. There is such a thing as “Teflon Flu”, also known as polymer fume fever. When a perfluorinated non-stick coating, say, on a pan is subjected to temperatures of around 450 C, the coating begins to decompose and will generate vapors that are hazardous.

We should all remember that Teflon^TM is a Chemours trademark and refers to a polytetrafluoroethylene polymer (PTFE). PTFE is a macromolecule unlike PFAS substances. PTFE is in the same persistence class as a “forever substance,” but as an insoluble solid polymer it is not mobilized at the level of molecules so migration into the cellular architecture isn’t viable path as with PFAS. The PTFE polymer is extraordinarily useful in the world and has many, many uses as a polymeric, chemically inert material and should not be cast into the dumpster with its cousins, the PFAS compounds.

100-year concrete aging experiment ends in 2023

Somebody was thinking ahead at the University of Wisconsin-Madison in 1910. Civil engineering professor and later Dean of the College of Engineering, Morton O. Withey (1882-1961), began an experiment on the effect of age and environment on what was then a relatively new building material- concrete. Now, in 2023, a second 100-year batch of experimental castings are coming to completion.

Source: The Chi Phi Chakett, 1955

Withey, a 1904 Dartmouth graduate, began casting samples of various compositions of cement, sand and stone in 1910 when he initially cast 450 of the 6 x 12-inch cylinders. He cast other sets of samples in 1923 and 1937 for a total of over 2500 cylindrical castings.

According to the Wisconsin State Journal the 1910 samples were tested at the 100 year mark and the 1937 samples were tested at the 50 year mark. A comparison of the 1910 samples revealed that both the samples stored in the air and in water strengthened in similar increments for a time and thereafter the samples stored in water continued to strengthen. Exposure of the dry samples to carbon dioxide lead to chipping. The dry 1910 samples yielded to 75 tons of pressure whereas the wet samples yielded at up to 100 tons of pressure. This disparity is thought to arise from continuous hydration of the water-wet samples.

Since the time when the samples were cast, the chemistry of cement and concrete has changed to where the engineering data is no longer of interest for ongoing work. However, the experiment has broadened the envelop of known properties of various concrete compositions.

A wealth of interesting information on the properties of concrete can be found at the Wikipedia website.