PFAS are a group of manufactured chemicals that have been used in industry and consumer products since the 1940s because of their useful properties, such as stability and water/stain resistance. While an estimated 6,000 or so possible forms of PFAS compounds exist, most of the possible forms have not been manufactured. The most well-studied and characterized are Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS), both of which have been replaced in the United States with other PFAS in recent years.
Now, in the most recent UCMR 5, EPA regulators are honed in on PFAS compounds in consumer goods, and particularly in drinking water. A common characteristic of concern of PFAS is that many of these compounds break down very slowly (if at all) and can build up in people, animals and the environment over time. PFAS can be present in our water, soil, air and food as well as in materials found in our homes or workplaces such as drinking water, soil and water at or near waste sites landfills, disposal sites, and hazardous waste sites. The most common use of PFAS is in aqueous film-forming foams (or AFFFs) used to extinguish flammable liquid-based fires which is typically found at airports, shipyards, military bases, firefighting training facilities, chemical plants, and refineries.
Other sources of PFAS include a huge range of items like: chrome plating, electronics, certain textile and paper manufacturers, shampoo, dental floss, cosmetics, stain/water-repellent carpets, upholstery, clothing, and other fabrics, cleaning products, non-stick cookware, paints, varnishes, and sealants. Additionally, biosolids like fertilizer from wastewater treatment plants that are used on agricultural lands can contain PFAS and affect ground and surface water which directly impacts animals that graze on the land. Even in our food there is concern. For example, fish caught from water contaminated by PFAS, dairy products from livestock exposed to PFAS and even food stored/transported in grease resistant food packaging and containers.
And when we throw our stuff into the garbage or a landfill, any PFAS leech out can easily contaminate the surrounding groundwater. The strength of the C-F bond in the group of chemicals like perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) that keeps food from sticking to skillets and helps put out fires also resists decomposition and breakdown in the environment. It’s why this group of chemicals were nicknamed “forever chemicals.” For many consumers, out of sight means out of mind. But unfortunately, leachates from landfills and wastewater is often somebody's drinking water downstream.
Thus, removing PFAS from wastewater is a key step towards breaking the cycle of ongoing contamination. In April 2022, the U.S. Environmental Protection Agency announced three commitments to reduce PFAS pollution in the environment. Six weeks later, on June 15, the EPA revised its health advisories for four PFAS chemicals: PFOS, PFOS, Hexafluoropropylene Oxide (HFPO) Dimer Acid and its Ammonium Salt (GenX chemicals), and Perfluorobutane Sulfonic Acid and its Potassium Salt (PFBS). And wastewater industry insiders say that it’s only a matter of time until the EPA sets regulatory limits for certain PFAS compounds.
This means that testing wastewater for PFAS is more important than ever. As industry continues to wrap its head around the scale of the problem, companies will need to improve the scalability and cost-effectiveness of their testing workflows to ensure that the water going into our lakes and rivers and coming out of our taps is safe and clean.
Drinking Water: Small Amounts, Big Problem
Initially believed to be relatively harmless, it’s only been in the last decade or two that toxicologists, epidemiologists, and members of the public have begun to raise concerns about PFAS in the environment, especially in drinking water.
Toxicology studies have shown that these ‘forever’ chemicals are also ‘everywhere’ chemicals, being found everywhere from food crops to polar bears in the remote Arctic. And the concentration of PFAS needed to alter physiology in humans and wildlife is often minimal. National studies by the Centers for Disease Control and Prevention conducted between 1999 to 2014 found four PFAS chemicals in the blood of nearly everyone they tested. Other toxicology studies have found links between PFAS and immune problems, liver damage, and several types of cancer.
The long-lasting biological effects of even minimal amounts of PFAS chemicals is part of the reason the EPA set the health advisories of the four PFAS compounds at concentrations in the parts per trillion or parts per quadrillion range. Another factor is the sheer volume of PFAS compounds in the environment. Even low levels of individual chemicals can add up to significant amounts when there are hundreds or even thousands of them in the products we use, the food we eat, the water we drink, and the air we breathe.
While most of us can recognize that parts per trillion is an infinitesimal amount, it’s much harder to comprehend just how small this is. As the Massachusetts Water Works Association pointed out on Twitter, a part per trillion is a drop of water in 20 Olympic-sized swimming pools or $1.20 of all the US currency currently in circulation. Many of us probably have that much money currently hiding between our couch cushions.
Finding the PFAS Needle in the Haystack
The challenge for analytical chemists is detecting these miniscule amounts. Just as toxicologists have gotten better at detecting the health impacts of vanishingly small amounts of PFAS chemicals, technology has also improved our ability to detect even the tiniest amount of PFAS contaminant in a variety of substrates. Liquid chromatography followed by (most commonly) tandem mass spectroscopy (LC/MS/MS) can find PFAS in water samples at levels in the parts per trillion or parts per quadrillion range. However, it’s one thing to do this as part of a research study. Performing these tests repeatedly and at scale is quite different, especially when the EPA begins requiring PFAS testing for drinking water and wastewater.
The biggest challenge for those doing the testing is sample preparation. Currently, the Department of Defense Quality Standards Manual and the recently published, draft EPA 1633 requires a two-step solid phase extraction (SPE) followed by a clean-up step using a graphitized carbon black sorbent. This adds to the time needed per test for technicians as well as the cost of consumables. Some new stacked SPE/GCB cartridges on the market allow both processes to be performed in a single step, which has been demonstrated to improve method performance while saving both time and money, allowing for greater overall gains in lab efficiency.
Sample cleanup steps are often recommended because they help save money and time in the long run as a result of injecting cleaner samples into your LC-MS/MS system. If you do direct injection of an environmental sample (even with co-solvation with methanol extract) you risk injecting extraneous organic matter, like tannic acid and fulvic acid that can gunk up your system and cause signal depression, which will affect your sensitivity. This risk increases for wastewaters and groundwaters as they are much more complex than drinking water.
Though drinking water is cleaner, many utilities test their source waters for potential contamination as source waters from rivers, groundwaters have large amounts of organic matter, so there is still a risk for drinking water utilities when testing for PFAS contamination. Contract labs face an additional challenge as it’s difficult to know the type of sample coming into labs. Samples can be mixtures of sludge, biota, and other debris. It’s a big challenge to clean it up, and one of the reasons the EPA likes solid phase extraction for sample prep.
The New Regulations: Looking to the Future
So, what are drinking and wastewater operations managers, utility districts and other stakeholders to do? The recent publication of the single lab validated EPA 1633 that has been developed for PFAS in wastewater, groundwater, is meant to support the clean water act. This method covers a PFAS panel of just 40 common PFAS compounds. Looking ahead, a major challenge is screening for the vast amount of possible PFAS compounds and their precursors and byproducts produced during manufacturing.
The challenge is staying one step ahead of the chemicals that are being synthesized to be able to identify them in wastewater and then remove them before the water is returned to the environment or our taps. A PFAS chemical can have a chain of anywhere from 2 to 18 carbons (making it hydrophobic) plus a variety of different functional groups besides the perfluoroalkyl group (such as sulfonate, carboxylate, ethyl, or propyl groups) which can make the compound semi-volatile and more hydrophilic. It’s a large mixture, but the technology is excellent. We can find a needle in a haystack—literally. Ultimately, the problem of PFAS won’t be solved with analytics, but these techniques can help reveal the scope of the issue and the best way to manage it given their everyday utility. What the public needs to do is to say, “I’ll deal with grease on my pizza box, or risking some stains in my carpeting.” And without a doubt alternatives to firefighting foams need to be developed.
Even in a future scenario where PFAS could be largely banned within the U.S., in all likelihood we still import many products from abroad that don’t ban their manufacture – and those products will ultimately end up in landfills. The fast-moving regulatory environment and development of PFAS rules will be the largest motivator for agencies to establish prevention, monitoring and maintenance strategies. We’ll all need to continue to anticipate these, and where possible, get ahead of them, in pursuit of safer groundwater for everyone.