What are PFAS – and why are they sometimes known as “forever chemicals”?
Perfluoroalkyl and polyfluoroalkyl substances, or PFAS, are a group of nearly 15,000 different man-made chemicals. They all share a similarity in structure, as all contain carbon-fluorine bonds. These bonds are very strong, and the molecular structure works to repel water and oil, making PFAS molecules extremely resistant to degradation both in the environment and in the human body. This is why PFAS are often called “forever chemicals” – once they are released into the environment or human body they remain there in the same form for an exceptionally long time, and as more PFAS are released into these systems, the more they accumulate.
Because of these unique properties, PFAS became extremely popular in the mid-twentieth century, and were used in a lot of different everyday items including takeaway food packaging, non-stick pans, dental floss, cosmetics and makeup, stain-resistant fabrics and carpets, rainwear, and cleaning products, just to name a few. And as well as being used in consumer products, PFAS became a popular fire extinguisher in the form of aqueous film-forming foams, known as AFFFs.
What impact can PFAS chemicals have on the environment – and on us?
In the later decades of the 20th century, there were increasing concerns about the use of PFAS in consumer goods, and its effects on humans and the environment - concerns which came to a head when the public finally learned about the potential dangers of PFAS and their near-indestructible nature in the early 2000s. It became widely acknowledged that PFAS were not only used everywhere in consumer products, but could be found in nearly every environmental and biological medium – soil, water (including drinking water), plants, animals, and wind-blown dust. It was even shown that PFAS had made it into our food chain, and could even be detected in our own biological fluids such as urine, saliva and blood.
Around the same time, other studies showed that many of these PFAS were toxic to humans. Two particular types of PFAS commonly used in AFFFs, perflurooctane sulfonate (PFOS) and perfluooctanoic acid (PFOA), were linked to kidney and testicular cancer, high cholesterol, ulcerative colitis, and reduced immune response. Not only that, but PFOS and PFOA also remain suggestive of causing thyroid disease and kidney disease.
Because PFAS had been used in manufacturing across the world for decades by this point, there were many different ways these molecules had made it into the environment, with the most influential being manufacturing leaks and waste dumping, run-off from landfill, and the wide use of AFFF fire extinguisher. One key way they can quickly contaminate nearby sites is via water, as their molecular strength helps them travel and accumulate without deteriorating. Once PFAS has made it into a waterway via rainwater run-off from contaminated sites, or even via waste dumping in lakes or rivers, these compounds travel quickly and leach into nearby environments and can even contaminate aquifers.
Since the early 2000s, there has been an enormous effort to reduce the use of PFAS in consumer goods. However, it is likely that you still encounter PFAS in consumer items every day, on top of the PFAS which has already accumulated in the environment.
Your research focuses on developing devices called “biosensors”, which can be designed to detect PFAS compounds in water. First of all, what are biosensors?
The word “Biosensor” is an umbrella term for devices which use biological components to detect or quantify the particular chemical substances you want to measure - called the analyte - in samples such as soil, water, or bodily fluids, which from a chemistry perspective are quite complex.
Why use biological components? Because in order for living organisms to survive, nature has already solved many of the issues we face when finding ways to identify analytes. Over billions of years, the biological systems in living organisms of all types have evolved to identify and isolate particular chemical substances in complex mixtures using proteins, antibodies, nucleic acids, and even specialised cells. When designing biosensors, we harness these finely-honed processes to detect the analytes we choose.
There are other methods chemists use to detect analytes in complex samples, such as chromatography – a process which separates a sample into each of its components. These methods are fantastic, but getting results can take time, and requires large, expensive equipment which is immobile and needs to be operated by someone with specialist training. By contrast, biosensors are cheap, portable, easy to use, and results are delivered almost instantly. You don’t need specialist training to use one – in fact, many types of biosensors are widely used by the general community, including pregnancy tests, the Rapid Antigen Test (RAT) for COVID-19, and blood glucose monitors for diabetes management.
How could biosensors help in detecting and eliminating PFAS chemicals in the environment?
Because PFAS are toxic and found everywhere, they are monitored and their concentrations regulated in the environment both in Australia and across the world. Currently, the gold-standard method for detecting PFAS is liquid chromatography in combination with another process called mass spectrometry, which measures the exact mass and charge ratio of each of the sample’s components. Although this technique detects PFAS accurately and at low concentrations, the process is complex and requires the sample to be delivered to a well-equipped laboratory for analysis. This can lead long turn-around times at substantial cost to the sample collector, and these logistical barriers end up limiting the number of tests that companies are willing to complete - a big issue, as detecting and measuring PFAS in the environment is essential for public safety and environmental remediation.
To help solve this, our research group wondered if we could design an affordable PFAS-detecting biosensor which could be used in the field and deliver accurate results rapidly. The first step was to find a biological substance which would be able to detect PFAS. Sure enough, we found a particular fatty acid binding protein which binds strongly and specifically to PFAS – importantly, the toxic PFOS and PFOA.
Using this protein, we are now developing a handheld biosensor which quickly and efficiently detects PFOS and PFOA in water. We hope that by creating a cheap, handheld biosensor, we can help communities and environmental assessors more easily and efficiently determine the safety of their waterways and even their drinking water.
What do you hope the impact of your research will be?
Due to their remarkable stability, we are stuck with the “forever chemicals” for the long-term. As they continue to accumulate in soil, waterways and plants - and even in ourselves and in livestock and other animals - it is imperative we find more efficient and accurate ways of measuring PFAS to ensure our own, and the environment’s, safety into the future.
We hope that by developing an affordable, handheld biosensor which can efficiently detect and measure PFAS levels in a given sample, more frequent and accessible testing can be done to monitor these toxic compounds. A device like this could help regulators track PFAS in the environment at a larger scale in both populated and remote areas, making better environmental screening possible on top of the targeted analyses which are done currently. It could also help communities who may be concerned about the safety of their drinking water but cannot afford to send samples to a lab for a traditional test. In the future, we may even be able to quickly and easily screen PFAS levels in people who are at risk of prolonged exposure.
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Henry Bellette is a PhD student in the La Sense Research Group at the La Trobe Institute for Molecular Science (LIMS) and La Trobe’s School of Agriculture, Biomedicine and Environment (SABE), and a member of the Biomedical and Environmental Sensor Technology (BEST) Centre. Dr Saimon Moraes Silva is the Director of the Biomedical and Environmental Sensor Technology (BEST) Centre, and head of the La Sense Research Group.
