Forever chemicals, particularly per- and polyfluoralkyl compunds (PFAS), are one of the biggest present environmental health hazards. These synthetic chemicals aren’t localised in a few contaminated areas; they are everywhere: in rivers, groundwater, wastewater, and even in household dust. They have been connected with various cancers and developmental diseases. And they are widespread. In the US, an estimated 98 per cent of people have detectable levels of PFAS in their blood, a pattern replicated around the world. World Bio Market Insights reported on the PFAS problem.
PFAS are found everywhere. They have been used for decades in ordinary consumer items such as non-stick pans, firefighting foam, and food packaging; because they were so effective in their functions: resist heat, retard flames, repel water, and reduce friction. The flipside of this: they almost cannot be broken down. Yes, there are methods that work fine in the lab. Like adsorption, electrochemical oxidation, UV irradiation, sonochemical degradation, or nanofiltration. The problem with most of these methods: they take too long, they are too costly, or they produce toxic byproducts.
MIT’s silken membranes
But the good news is that new treatment solutions have come to the surface. For instance, at MIT, Yilin Zhang, Benedetto Marelli, and four other researchers reported on a new silk-based PFAS problem remediation platform. They discovered this almost by accident. For another research project, the researchers had silk proteins processed into uniform nanoscale crystals. But once combined with cellulose nanocrystals, the silk proteins formed a completely new and powerful material that could remove contaminants: PFAS among them.
The problem with many biobased membranes is that bacteria and fungi quickly tend to take over. But this new material also had high antimicrobial properties. Moreover, it proved to be quite sustainable. And it could be cheaply produced from industrial side products. Like from the silk industry. Or from forestry wood waste pulp.
A fungal and circular PFAS problem platform
The membrane filtration approach is just one method of tackling the PFAS problem; but it is not the only one nor the most effective. Removing PFAS from soil or water raises the issue of what to do with the toxic material later. Actually breaking down the chemicals, not just filtering them out, is key.
Susie Dal of Texas A&M Agrilife Research developed an effective method. Her team found a fungus called ‘white rot’ that degrades PFAS at a rapid rate. The vast majority of the two PFAS types PFOA and PFOS were being removed. The team used a modified organism as the PFAS-degrading device. They constructed a ‘matrix’ from the leaves, stalks, and cobs of corn plants left in the field after harvest. These formed a porous biological structure that fixed the PFAS chemicals and the fungus over an extended period, this speeding up the process. This could have the potential for a low-cost and sustainable environmental clean-up. Fortunately, unlike other solutions to the PFAS problem, the platform does not produce other toxic waste products during the process of treatment.
PFAS-eating microbes
At universities around the US, another biobased tool for PFAS degradation is being developed: microbes that metabolise the chemicals, so they become easier to treat through more conventional means. At Northern University, a group of chemists researches the Acetobacterium bacteria group. Some of the microbes can split PFAS into smaller pieces; these could then be treated more easily by chemicals.
And at Princeton, the Acidimicrobium A6 is under investigation for its PFAS-eating properties. This is a rare microbe. It can apparently break apart the carbon-fluorine bond that makes the PFAS problem so resilient. The microbe was originally found in a very particular acidic and iron-rich wildlife management area.
Soil contamination
Around PFAS manufacturing sites, the soil can be hyper-contaminated. Could even these soils be cleansed? In Flanders, Belgium some groundwater concentrations are so high around a major PFAS manufacturing site that residents within 10 miles have been warned they should no longer eat home-grown produce. This will make difficult existing approaches to treat the PFAS problem. The volume of affected soil is so big that soil washing and thermal treatment are expensive and energy-intensive.
Microbial solutions might be an alternative. But then, scientists would have to find ways of consistently producing microbial strains that break down PFAS effectively. Scientists still do not understand the exact physiological and chemical mechanisms inside these creatures that can break down these chemicals. In other words, more work needs to be done.
A varied toolkit
And then, there are biobased methods to PFAS degradation. Their advantage of these is that they produce much fewer harmful chemical pollutants than other approaches. Moreover, a biobased PFAS treatment is more sustainable and biodegradable than chemical treatments.
Unfortunately, no single biobased method will be enough to tackle an environmental health problem of this scale. Treating the FAS problem effectively may require a multi-step process. This may combine different biobased, physical and chemical approaches. It is unlikely that ever a single solution will address the entire problem, as there are between 800 and 7 million chemicals within the PFAS group.
Many techniques required
Therefore, although a simple tap attachment in the home containing plant-based matrixes of microbes or fungi could become the first line of defence against bodily contamination, it will need to be complemented by equipment at existing water treatment plants; tackling the PFAS problem in a more centralised manner. Although microorganisms have proven particularly good at treating shorter-chain PFAS, the longer-chain PFAS will still have to be the target of chemical interventions. So, whatever the arrangement, it is clear that the sheer number of PFAS chemicals will demand various techniques and infrastructures; including biobased and circular platforms.
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PFAS problem, solved at last?
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