Due to their high stability, PFAS have been referred to as “forever chemicals”,
because they do not degrade naturally and persist in the environment. They
are not degraded naturally because polyfluorinated compounds are not
present in nature, so evolutionary pressure for degradation was never
present. [1,2]
The continuous production and use of PFAS have inevitably led to their
dispersion in the environment, with an estimated 5% of these substances
being found in various environmental media. Their widespread presence
often exceeds regulatory limits, resulting in significant exposure risk for both
wildlife and humans. [2,3,4]
Major sources for intake are drinking water, food, consumer products, and
house dust. Prolonged exposure can lead to bioaccumulation in organs and
blood serum and PFAS can easily biomagnify along the food chain. [1,5]
Concerns about these substances are growing due to emerging evidence
linking PFAS exposure to numerous health issues. These include problems
with the immune, endocrine, metabolic, and reproductive systems, as well
as an increased risk of cancer, hypertension, higher cholesterol levels,
ulcerative colitis, thyroid disease, pregnancy-related hypertension and
complications (low birth weight, increased miscarriages, and PFAS
transmission to the fetus), liver and kidney damage, and obesity. [3,6]
In addition to the physical health risks, PFAS exposure has serious
psychological effects. The invisible nature of these chemicals causes stress,
insecurity, disruption of routine, anxiety, a sense of helplessness, and fear.
These psychological impacts are often overlooked and insufficiently
addressed by institutions. [5]
Regulations and restrictions on PFAS production and treatment are continually
evolving. For example, since the 2000s, short-chain perfluorinated substances
made with GenX technology have been introduced to substitute traditional PFAS,
but their structure makes them more mobile and consequently more
deleterious to the environment. [1,7]
For PFAS degradation, two main approaches have been explored: adapting
existing technologies for PFAS destruction or developing new technologies for
remediation. Chemicals and physical treatments for PFAS are widely used
nowadays, though they require high energy, high costs, and often additional
post-processing. The process typically involves separating PFAS from the
medium followed by their destruction. Examples of separation technologies are
ion exchange resin (IXR), granular activated carbon (GAC), nanofiltration (NF),
and reverse osmosis (RO). Although IXR systems are more expensive than GAC,
they are favoured because they offer higher adsorption capacities, require less
contact time, and occupy a smaller footprint. Additionally, IXR can be
regenerated on-site to nearly their original capacity and reused multiple times,
unlike GAC, which cannot be feasibly regenerated on-site. With separation
technologies, PFAS remains a risk for people and the environment as they do
not degrade and so they are often stored until a suitable degradation method is
found. Finally, some destructive technologies include electrochemical
oxidation, plasma, photocatalysis, sonolysis, supercritical water oxidation,
thermal degradation/incineration, pyrolysis/gasification, and advanced
oxidation processes (AOPs). [6,8]
On the other hand, biological solutions may represent the best options, due to
lower costs and less environmental disruption. Bioremediation successfully
treats numerous long-lasting organic contaminants, but for PFAS the
biodegradation process is not fully understood. Some intermediate metabolites
have been hypothesised, and more studies are needed on microorganisms and
enzymes involved in PFAS biodegradation. [1]
Biodegradation strategies include:
