As researchers rush to tackle global contamination from a class of toxic chemicals known as PFAS, a new study demonstrates a novel way to detect the substances in wastewater – but also underscores how far scientists are from figuring out how to effectively overcome this worldwide threat to human and environmental health.
The new method makes use of a sensor to identify one type of per- and polyfluoroalkyl substances (PFAS) called perfluorooctanoic acid (PFOA) in heavily contaminated water based on changes in light emissions from metals on the device’s surface, according to a Jan. 16 study in the journal Analytical Chemistry. The researchers plan to develop the early model in to a portable device, according to a press release.
Current PFAS detection methods take place in a laboratory using a tool called a mass spectrometer, which charges molecules in a sample and then accelerate them using magnetic or electric fields so that scientists can identify them.
“Existing approaches are time-consuming,” said Zoe Pikramenou, a professor at the University of Birmingham in the United Kingdom who is an author of the study. “Our approach offers significant advantages of greater speed, ease of analysis, and reduced cost over currently-used methods.”
The prototype can so far only measure one PFAS chemical out of thousands. And although the sensor appears to be sensitive enough to illuminate PFAS in industrial wastewater, it may take another decade before the technology can be used for drinking water, which contains much lower levels of the chemicals, said Pikramenou.
Many other promising new technologies to detect so-called “forever chemicals”, which do not naturally break down, remain in the early stages of development. The Biden administration has called on federal agencies to restrict PFAS from entering US water, air, land, and food; set goals for the government to better assess and reduce PFAS exposure; clean up existing pollution; and expand health effects information.
“You’re looking at several trillion dollars worldwide for detection, remediation and all that,” said Jay Meegoda, a professor of civil and environmental engineering at the New Jersey Institute of Technology. “There’s a very big market, but there’s a long way to go.”
PFAS chemicals do not break down naturally and can leach into drinking water from industrial sites, sewage treatment plants, and landfills. PFAS have been found in at least 45% of US tap water and in the blood of about 97% of Americans. Exposure to the chemicals has been linked to numerous health problems, and a group of global cancer experts recently classified PFOA as carcinogenic to humans and perfluorooctanesulfonic acid (PFOS), another PFAS chemical, as possibly carcinogenic to humans.
The US Environmental Protection Agency (EPA) announced proposed drinking water standards last March for six PFAS chemicals last March, including standards of just 4 parts per trillion for PFOA and PFOS – the lowest level at which the chemicals can be reliably measured. The companies 3M, DuPont, and others agreed to settlements totaling up to $12.5 billion last summer that will help fund communities’ efforts to test for PFAS in their drinking water and remove the harmful chemicals.
But just how to do that testing remains a challenge.
“At the current time, we’re really limited in our ability to detect and quantify PFAS,” said Karen Howard, Director of Science and Technology Assessment for the US Government Accountability Office (GAO). “People are continually trying to come up with new and better methods for detecting PFAS in water.”
There are currently three EPA-validated methods for detecting PFAS chemicals in water, including two for drinking water and one for untreated surface, wastewater, and groundwater, according to a 2022 GAO report. Together, these methods can detect about 50 types of PFAS.
The methods rely on a laboratory technique called liquid chromatography mass spectrometry, which is very expensive and time-consuming, according to Meegoda. Testing water for PFAS using this spectrometer technology costs about $500 and takes about a month, he said.
Sensor technology has the potential to overcome the limits of traditional PFAS detection methods, allowing for easier, low-cost testing on-site, said Woo Hyoung Lee, an environmental engineering professor at the University of Central Florida. Lee favors electrochemical sensors over optical sensors, since they can detect PFAS at lower concentrations, he said.
In addition to the luminescent sensor, recent developments include a dyed polymer that shifts from fluorescent red to blue when PFOA or PFOS are present, and new research on the potential of hybrid forms of a common mineral in sand, which just received a nearly half million-dollar grant.
Scientists are also working on strategies to detect the chemicals in air, soil, and other aspects of the environment, Howard added, although so far reliable tests only exist for water.
Few new-and-improved ways of detecting PFAS have come close to being validated and approved by the EPA, said Howard – a standard that technologies must meet in order for drinking water utilities to rely on them for meeting state and federal guidelines.
Remove and destroy
Beyond developing better technologies to test for PFAS, many researchers share the loftier goal of getting the toxic chemicals out of drinking water and the environment.
Currently, treating PFAS in water involves a two-part strategy. First, the chemicals are removed using one of three methods – granulated activated carbon (GAC), ion exchange, or reverse osmosis.
“GAC is cheap,” said Howard. It’s basically like a giant coffee filter.” As water runs through a GAC system, PFAS cling to the carbon particles, staying behind as cleaner water passes through the other side. Like GAC, ion exchange produces a solid waste product, while reverse osmosis results in a concentrated stream of liquid waste.
Whatever the treatment method, taking PFAS out of water necessitates a second step – destroying it. This is not straightforward.
Incinerating waste that contains PFAS can emit air pollutants such as fluorinated greenhouse gases and products of incomplete combustion, according to a 2020 study. “Research is urgently needed on the potential presence of PFAS compounds in air emissions from commercially run incinerators,” the authors wrote.
If PFAS is not completely destroyed during incineration, smaller PFAS products or other byproducts can be formed “which may not have been researched and thus could be a potential chemical of concern,” says an EPA technical brief.
It is not known whether 100% of PFAS is eliminated during incineration because “we don’t have good methods to test the air that’s leaving the facility,” said Howard.
Other disposal methods include burying the PFAS waste in a well-contained landfill or an injection well, but these, too, have their drawbacks. Scientists don’t have good ways of determining if PFAS is released through landfill leachate and gases, said Howard, and since there are only two suitable injection wells for PFAS in the whole country, large quantities of highly contaminated waste must be shipped to the sites.
The average amount of PFAS-containing waste shipped around the US each month has almost quadrupled since 2018, according to an analysis released in November by the watchdog group Public Employees for Environmental Responsibility.
While a lot of research is focusing on how to improve existing methods for removing PFAS from water, and potentially finding ways to make them cheaper, “we have not heard a whole lot about new methods being developed for removal,” said Howard. “I think people are working on that but I don’t think there’s anything that’s really close.”
“If you can destroy PFAS in the water, to simply get rid of it without having to separate it out first, that would be the best,” said Meegoda. “If somebody does that, they will be extremely rich.”