Editor’s Note (7/7/23): This story is being republished after a new study from the US Geological Survey found that chemicals called perfluorinated and polyfluorinated alkyl substances, or PFASs—suspected to cause health problems—may be found in almost half of the tap water in the US.
Perfluoro and polyfluoroalkyl substances, or PFASs, are considered indestructible chemicals. They are virtually non-degradable and accumulate in humans and the environment. Suspected health consequences include asthma, cancer and changes in the reproductive organs. How to get rid of PFASs has been completely unclear until now – and the first approaches to destroy the resistant molecules are showing promising results.
Heat is the major factor in breaking the carbon-fluorine bonds typical of this class of substances. In a study recently published in the Environmental engineering magazinethe U.S. Environmental Protection Agency discovered a heat and pressure-based technique known as supercritical water oxidation destroyed 99 percent of PFASs present in a water sample.
PFASs have a combination of properties that make them ideally suited for many technical applications. They repel both oil and water and resist damage from high temperatures and chemicals. As a result, they are found in many consumer products, but also in applications such as fire extinguishing foam. And they can now be found almost everywhere in the area. She, for example contaminate soil and groundwater in several German provinces. In the southwestern city of Rastatt, Germany, PFASs rendered drinking water useless in 2019. Studies show measurable concentrations of the substances in blood and breast milk in the European population.
The first attempts at using new methods to destroy these “indestructible” fabrics offer at least some hope. In the new EPA study, experts added oxidizing agents to water contaminated with PFASs and heated the fluid above the critical temperature of 374 degrees Celsius at a pressure of more than 220 bar. During this process, the water becomes supercritical: it is neither gas nor liquid. In this state, even water-repellent substances such as PFASs dissolve much more easily and at the same time the state speeds up chemical reactions. Several versions of this technique had previously been developed to break down different types of chemicals, but this is the first time it has been tested against PFASs in a peer-reviewed study.
The researchers tested methods from three companies. Each method differed slightly in the chemicals and processes used. But all trajectories produced the desired result, reports the team, which was led by EPA researcher Max J. Krause. In each case, the amount of PFAS in the water dropped by more than 99 percent.
“Since supercritical water oxidation systems are already commercially available, this could be a technology that could soon be deployed to significantly impacted sites or wastewater,” says Krause. “We are currently evaluating air emissions to understand all pathways and to make sure we destroy the PFAS.”
The new study also found that the number of previously identified PFASs in the water accounted for about a quarter of the substances destroyed in this category. This shows that existing analytical techniques only identify a fraction of these chemicals. The variety of industrially used PFASs is so great that many of them are hardly known.
Still, the finding shows that the technology used in the study reduces the invisible pollution caused by the vast number of known and obscure PFASs. But the success of the hot water method doesn’t completely mitigate the threat of forever chemicals.
“The idea of using a supercritical fluid to destroy PFAS seems like a smart option, but I wonder what its practical application is,” said Jamie DeWitt, an associate professor of pharmacology and toxicology at East Carolina’s Brody School of Medicine. University. who was not involved in the new study. “It might be a great idea on the bench, but can it be scaled up to a watershed or even a drinking water treatment plant?”
To begin with, the technology is relatively complex – and therefore expensive – due to the high temperatures and pressures involved. And for another, it is currently unrealistic to clean contaminated soils and groundwater in this way. Therefore, some experts argue that the use of PFASs should be limited to absolutely necessary applications.
“Some argue that the persistence of PFAS is so great that [they should be phased] out of production,’ says DeWitt, ‘because they are not part of a sustainable world.’
This article originally appeared in Spectrum of Wisdom and is reproduced with permission.