PFAS: The “Forever Chemicals”

Hilal Akman and Areej Qamar

2022-01-01 00:09:23

“Man-made chemical” sounds dangerous if we imagined it in relation to what we eat, put on as clothes, or use with our hands. We should not be obsessed with it, but it is important to be aware that there are a lot of things around us which might be contaminated with what is called “forever chemicals.”

Perfluoroalkyl substances (PFAS) are highly hazardous man-made chemicals that have been used since the 1940s. Some well-known examples of PFAS are perfluorooctanoic acid (PFOA, C8HF15O2), heptadecafluorooctanesulfonic acid potassium salt (PFOSK, CF3(CF2)7SO3K), and GenX (HFPO-DA, C6H4F11NO3). Although these substances are very useful in the chemical industry, the dispersion, low biodegradability, and high stability of the molecules have led to many environmental and health issues. PFAS molecules are very difficult to remove, let alone break down, and these molecules can accumulate over time. This is the reason why PFAS molecules are referred to as “forever chemicals.” They are extremely hard to break down due to the high strength of the carbon-fluorine (C-F) bond found in these compounds. This bond can have a bond dissociation energy of up to 546 kilojoules per mole (kJ/mol). Bond dissociation energy is the energy required to break a bond, and a high bond dissociation energy, as exhibited in a C-F bond, corresponds with a bond that has low energy and is very stable.

Applications of PFAS in industry

Why are these chemicals so extensively used in the chemical industry? PFAS molecules have been found to be very stable, and they exhibit properties that allow them to repel both oil and water. As a result of these properties, these chemicals have been successfully employed to act as a repellent for almost anything. Some examples of the various applicants of PFAS are surface coatings, surfactants, and flame retardants. With so many uses, these harmful toxins can be found in everyday items such as clothing, furniture, food packaging, adhesives, and much more.

PFAS contamination

How exactly are we exposed to PFAS chemicals? Besides the exposure from PFAS containing materials, the answer lies primarily in our water systems and environment. The majority of our drinking water contains these “forever chemicals.” As a result of their widespread manufacturing, usage, and improper disposal, these chemicals can enter our water systems and air through different sites. Another way PFAS has become so widely dispersed is through groundwater and soil receiving rainwater runoff. Since these chemicals are not easily broken down, they can remain in our waters for a great number of years. It is reported that about 110 million people could have PFAS contaminated water at levels of 2.5 parts per trillion (ppt) or even higher. This value is way above the safe level of exposure to PFAS, and this is not where it even ends. Approximately 60 million people have water utilities that are contaminated with PFAS exceeding   5 ppt, and 16 million people with water utilities exceeding 10-90 ppt of the chemical. It is estimated that 242 water utilities throughout the United States are contaminated with PFAS chemicals. These statistics show just how prevalent these harmful chemicals are in the United States. There is currently no federal limitation as to the concentration of these chemicals in our waters which is a huge problem. Most people have shown signs of these chemicals in their bloodstream, which truly indicates the widespread exposure to these harmful chemicals.

Health effects from PFAS exposure

This increased exposure to PFAS can cause and lead to many adverse health concerns. If the chemicals are ingested, they can actually accumulate in the body and remain there for long periods of time. Scientists are still conducting studies about the effects of PFAS, but the existing research has shown that these chemicals may cause developmental effects in infants, lead to decreased fertility in women, interfere with the body’s natural hormones and enzymes, increase cholesterol levels, affect the immune system, and increase the risk of particular cancers. The extensiveness of the health effects in a person depends on how long, how often, and how much PFAS they were exposed to. Due to all of these negative effects, PFAS are environmental pollutants that are included in the United States Environmental Protection Agency (EPA) Contaminant Candidate List.

Removal and breakdown of PFAS

The health concerns surrounding PFAS exposure make finding a solution to the problem a very urgent matter. There have been many past attempts to remove PFAS from the environment. However, not all of these attempts have resulted in the development of environmentally friendly methods. It is extremely important to find a way to remove PFAS in a manner that does not cause further harm to the environment. The current goal for PFAS removal is to formulate and implement an efficient, green, and cost-effective process – a goal that is especially challenging when considering the high strength of the carbon-fluorine bond in PFAS molecules.

Incineration

One technique that is being explored is incineration or destruction of PFAS through the use of heat. This is done by directing heat at objects contaminated by PFAS, such as soil, waste, and water. Incineration is a method that has been used for the destruction of many other chemicals. Even though incineration can destroy PFAS, there are many other risk factors that need to be taken into consideration. For example, incomplete combustion of PFAS could lead to problems with the resulting products of the reaction. The process of incineration leaves behind waste residues that need to be properly disposed of, which needs a solution of its own. Incineration also requires an extensive amount of energy and fuel. In addition, incineration can result in PFAS emissions entering the air, the effects of which have not been researched in depth.

Reverse osmosis and nanofiltration

Reverse osmosis and nanofiltration are other methods that are being investigated for the removal of PFAS. They have been shown to be effective in removing PFAS. In simple terms, this is a pressure-driven process in which water is filtered by pushing the water through a semipermeable membrane. This process is useful for removing PFAS from water sources, and recent advances in manufacturing have made it possible to use this process more efficiently. The methods involved with reverse osmosis and nanofiltration have previously been used with removing many other chemicals from water. The process is commonly used in water purification systems and industrial applications, and it is most often employed for desalination purposes. Despite the wide usage of the process, there are some operating considerations that must be looked at for reverse osmosis and nanofiltration systems. Membrane technology comes with the challenge of fouling, where the accumulation of matter from the filtration process can result in a reduction in the flux performance of the membranes. To avoid fouling, the membranes must be constantly modified, and the operating conditions need to be continuously changed. Additionally, replacing the membranes results in waste products that contain PFAS residue, and cleaning the membranes requires there to be a way to dispose of the used cleaning solution. The “reject stream” or stream of water post-filtration will contain concentrated amounts of PFAS and will need to be disposed of or treated. Thus, waste management is a big issue that needs to be addressed if the processes of reverse osmosis and nanofiltration are to be used for PFAS removal.

What’s next?

It is clear that a method for removing and destroying perfluoroalkyl substances urgently needs to be found. These molecules have harmed the environment and our lives in countless ways. Many past attempts have come with drawbacks and failed to be cost-effective and environmentally friendly. Until we have found a way to successfully eliminate PFAS from the environment without causing further damage, these “forever chemicals” will continue to affect us detrimentally. So, what can you do? Fortunately, there are ways to be aware of these harmful chemicals in our water. If you are living in the United States, you can have your water checked for PFAS by contacting your state for a list of certified laboratories that are using the EPA Method 537. You can visit EPA’s website to search online for EPA certified labs for drinking water testing (https://www.epa.gov/dwlabcert/contact-information-certification-programs-and-certified-laboratories-drinking-water).

References

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