The Emerging Crisis of “Forever” Chemicals
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Per- and polyfluoroalkyl substances (PFAS) have penetrated every corner of the globe; they’ve infiltrated rainwater, contaminate our food and drinking water and are ever-present in the environment – even in the most remote locations. These “forever chemicals” have existed for almost a century but have gone largely unnoticed until relatively recently – perhaps because of their invisible nature. PFAS are everywhere, and they’re persistent; evidence is increasingly revealing their damaging impact on the environment and human and animal health.
What do we know about them, why are they such a problem and do they really last “forever”?
What are PFAS?
PFAS are a family of highly toxic fluorinated chemicals dubbed “forever chemicals” because of their inability to degrade in the environment. “PFAS are manmade chemicals with unique properties – oil and water repellent, temperature resistant and friction reducing – which makes them difficult to treat in the environment,” explains Amy Dindal, PFAS program manager at Battelle, the world’s largest independent non-profit applied science and technology organization.
These unique physical and chemical properties are the consequence of one of the strongest bonds found in organic chemistry: the carbon–fluorine bond, and that’s why PFAS are unable to degrade without intervention.
Invented in the 1930s, they were initially used in nonstick and waterproof coatings, but by the 1950s, PFAS were used on a large-scale to create consumer and industrial products resistant to heat, oil, stains, grease and water. In the late 1960s, the US Navy began working with a major PFAS manufacturer to develop aqueous film-forming foam (AFFF) to rapidly extinguish fires. In the same decade, traces of PFAS began to appear in human blood samples, but the chemicals continued to be used.
Figures vary, but approximately 4,500 PFAS have been identified in hundreds of everyday products, from nonstick cookware to greaseproof paper, fast-food containers, stain-resistant textiles to cleaning products and paint – and even personal care products like shampoos, dental floss and cosmetics have shown traces of PFAS.
“The same properties that make them [PFAS] so useful for multiple applications also make them very difficult to remove from the environment, as well as our bodies,” Dindal says. “The sheer number and variety mean uncertainty about their impacts is high, as not all PFAS chemicals have been studied for human health impacts.”
Some PFAS have been utilized more extensively, and specific examples, like perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), are more widely studied, so it’s important to note that what we know about PFAS is based on just a handful of chemicals, not their entire catalog.
PFAS are long-lasting and move throughout the environment. It’s their persistence, rather than toxicity, that’s the problem – it allows them to travel over large distances causing long-term, and even life-long, exposure.
How are we exposed to PFAS?
PFAS are ubiquitous in global environments – in the soil, air, water and even our food. There is no “safe space” on earth to avoid PFAS and it’s vitally important they are rapidly restricted, according to researchers from Stockholm University that discovered levels of POFS and PFOA in rainwater “greatly exceeded” US EPA Lifetime Drinking Water Health Advisory levels.
It's estimated there are almost 3,000 sites in the United States alone contaminated with PFAS. How do they get there?
Many are released during production and use or following the disposal of PFAS-containing material. They’re usually present at relatively low levels, but higher concentrations are typically found at contaminated sites, like fluorochemical manufacturing plants, metal plating factories or facilities using PFAS to produce goods.
PFAS exposure occurs in many ways, and it’s difficult to know which is the most detrimental. A Centers for Disease Control (CDC) survey revealed most people in the US are exposed to some PFAS at relatively low levels, typically through their diet as the chemicals can be present in fish, meat and dairy. Drinking water is another major exposure source, especially in contaminated communities where people and animals may be exposed to higher levels of PFAS through ground and surface water sources. Occupation may also be a factor, with firefighters or those working in chemical or manufacturing plants using PFAS at a higher risk.
Exposure pathways are similar for animals. Animal studies suggest some PFAS are linked with liver toxicity, tumors in multiple organ systems, disruption of the immune and endocrine systems, adverse neurobehavioral effects, neonatal toxicity and death. However, the bioaccumulation process in animals is different from that of humans, so existing metrics must be adapted, alongside new mechanistic models, before any meaningful conclusions can be made.
Impact on human health
Studies have shown that some PFAS in the environment can bioaccumulate to the point where they are detectable in the blood of humans and animals all over the world – even in the Arctic and Antarctica. Although these remote areas register low levels, they still exceed even the most stringent guidelines designed to protect human health.
What do we know about the impact of PFAS on the human body? Our current understanding of the biological impacts of PFAS is based on just four of the thousands of different chemicals in the group: PFOS, PFOA, PFHxS and PFNA. This is because there is not enough data on the biological risks of the entire catalog of PFAS, especially where the chemicals are found in very small quantities. Consequently, most human exposure assessments focus on these and, likewise, wildlife studies are limited to targeted PFAS – around 30 in total.
PFAS bind to proteins, such as albumin, and circulate throughout the body where they linger after exposure.
A study conducted in pregnant women found that maternal PFAS concentrations were associated with an increased risk of late-onset preeclampsia. There is some indication that exposure to PFOA, PFOS and PFHxS can diminish a child’s antibody response to vaccination, increasing their risk of developing infectious diseases. Results from epidemiological studies have indicated associations between PFAS exposure and the risk of developing some cancers, namely prostate, kidney and testicular cancer, in addition to increased risk of high cholesterol levels and adverse developmental outcomes. For many of these associations identified in human subjects, data is corroborated by animal studies.
A 2018 CDC report showed a link between 14 different PFAS chemicals and cancer, birth defects, thyroid disease and liver damage, Dindal says: “Other studies have linked consumption of PFAS-contaminated water to high cholesterol and nerve disorders.”
Children may be more sensitive to the harmful effects of PFAS and are thought to be exposed when putting their hands to their mouths after crawling or playing on carpets and upholstery treated with PFAS to be stain and water repellant. The chemicals are associated with low birth weight, developmental delay, accelerated puberty, bone variation, and behavioral changes in children.
Improving our understanding
It's vitally important to improve our understanding of PFAS and the risks they pose. Research exploring the substances is ongoing, but it’s challenging to study and assess the potential risk of each individual chemical due to the thousands of PFAS used in consumer, commercial and industrial products.
Most studies over the last decade have focused on a limited number of substances and are unable to account for the different ways people are exposed at different stages of life. The types of PFAS and how they are used have also changed over time, and there isn’t enough data on exposure sources for the general population, or the contribution that food processing and packaging makes to PFAS levels in food.
Simply put, we still don’t know how harmful PFAS are – finding the answer will require a long-term in-depth evaluation. Improved laboratory methods are required to more effectively identify and measure PFAS in all media. Current analytical methods, such as liquid chromatography-mass spectrometry (LC-MS), collect data on specific substances with high precision and sensitivity, however, new techniques are needed to reveal the presence of unidentified PFAS in the environment and their characteristics.
We need to do more than just test for these dangerous chemicals; we need to better understand the release and environmental degradation pathways of PFAS to determine how the chemicals can be managed and disposed of.
Of particular interest is how to remove PFAS from drinking water sources. Current methods remove contaminants through techniques like filtration. While effective, it transfers these contaminants to other media, generating secondary waste that requires incineration or landfilling.
Researchers from Northwestern University have developed a method to “slot into” the water purification process after PFAS have been removed. The process is inexpensive, uses low temperatures and destroys PFOA using sodium hydroxide, commonly used to make household products like soap. It could be used to treat concentrated PFAS waste in a more energy-efficient manner.
“The degradation uses very simple conditions,” study lead Dr. Brittany Trang explains. The process involves “chopping off” the carbon-based head of the PFOA molecule, leaving the rest to fall apart. “However, integrating this into any industrial system would take much more optimization than we currently have done – we aren’t ready for that yet!”
Trang says further research is required before this method can be used on other PFAS, like perfluorosulfonic acids, but it’s promising and she hopes it will encourage people in the PFAS degradation field to think about designing destruction methods differently.
PFAS destruction using oxidation is a more attractive option, according to Dindal, “because it completely removes the chemicals from the environment,” and doesn’t generate any secondary waste.
Tackling the PFAS problem
PFOS and PFOA pollution is just the tip of the iceberg; there are thousands more PFAS that we know little about, and we know even less about the risks they pose.
The damage PFAS can have has been increasingly recognized, particularly in the last 20 years, and there are many safety levels in place that have been reduced over the years. However, these are often only advisory and so are not legally enforceable.
In 2002, one major manufacturer voluntarily phased out the production of PFOA and PFOS globally as a precautionary measure, including materials used to produce certain repellents and surfactant products, AFFF and coatings for food packaging
More recently, carpet manufacturers, who’d recently replaced one type of PFAS with another, eliminated all PFAS after learning they too could be problematic. They were encouraged by the Madrid statement, signed by hundreds of scientists who say no PFAS should be used as they never degrade, and could cause harm to health.
These are just two of the many strategies in place to reduce emissions, production and uses of specific PFAS. While many PFAS have already been phased out or substituted, there are plans to further restrict usage, manufacture and import of certain PFAS, expected on a chemical-by-chemical basis.
In June 2022, the EPA released a national testing strategy that requires PFAS manufacturers to provide the agency with toxicity data and information on categories of PFAS chemicals. The agency has selected PFAS to be tested based on an approach that breaks the large number of PFAS into smaller categories based on similar features and considers what existing data are available for each category. The aim is to address the data gap and investigate all PFAS one at a time, although this will be a challenging and time-consuming task.
It's clear that there is much more to be done. We need more research into the different types of PFAS and the damage they can do, more information on their replacements and alternatives – and any risks they might pose – and we need to discover more ways to destroy and eliminate the PFAS that are already in the environment. They might not have to be “forever” chemicals, as we once thought.