What are PFAS -‘forever chemicals’- and are they bad for us?

PFAS, a ubiquitous family of synthetic chemicals known as per- and polyfluoroalkyl substances, have woven themselves into the fabric of modern life. Their remarkable properties – water, grease, and stain resistance, along with extreme durability – have led to their incorporation into an astonishing array of everyday items. From the waterproof coatings on our raincoats and outdoor gear to the non-stick surfaces of our cookware, from the smudge-proof formulations in cosmetics and personal care products to the protective layers on food packaging and textiles, PFAS are present in countless objects we interact with daily. This pervasive presence extends beyond manufactured goods, however. Scientific studies have detected PFAS in our food supply, particularly in seafood and conventionally grown produce, and alarmingly, in our drinking water sources across the globe. Furthermore, these persistent chemicals have been found within the human body, a testament to their widespread environmental distribution and our constant exposure. But what precisely are these substances, and what are the implications of their presence for our health and well-being?

Mark Miodownik, a renowned scientist, delves into these critical questions, aiming to demystify PFAS and illuminate the potential dangers associated with their widespread use. His exploration, a BBC Ideas production in partnership with the Royal Society, seeks to provide a comprehensive understanding of these "forever chemicals." The film, directed by Christopher Brooks and presented by Mark Miodownik, offers a deep dive into the chemical structure, historical development, and environmental fate of PFAS.

At their core, PFAS are characterized by a chain of carbon atoms bonded to fluorine atoms. This carbon-fluorine bond is one of the strongest single bonds in organic chemistry, bestowing upon PFAS their extraordinary resilience. This strength means that PFAS do not readily break down in the environment or within living organisms. Instead, they persist for exceptionally long periods, hence the moniker "forever chemicals." This persistence is a double-edged sword: it makes them incredibly effective for their intended applications but also poses a significant long-term environmental and health challenge.

The history of PFAS dates back to the mid-20th century, with the discovery and commercialization of chemicals like PFOA (perfluorooctanoic acid) and PFOS (perfluorooctanesulfonic acid) by companies like DuPont and 3M. These early PFAS were lauded for their revolutionary capabilities. PFOS, for instance, was a key ingredient in firefighting foams used to extinguish highly flammable liquid fires, particularly at military bases and airports. PFOA was instrumental in the manufacturing of Teflon, enabling the creation of non-stick cookware that revolutionized home kitchens. Their applications rapidly expanded, permeating numerous industrial processes and consumer products.

However, as our understanding of chemistry and toxicology advanced, concerns about the potential health and environmental impacts of these chemicals began to emerge. Initial studies focused on occupational exposure in manufacturing facilities, where workers were exposed to higher concentrations. These studies revealed a correlation between PFAS exposure and a range of adverse health outcomes. Over time, research has expanded to examine the effects of lower-level, chronic exposure in the general population.

The sheer number of different PFAS compounds is staggering, with estimates ranging from several thousand to over ten thousand. This vast chemical family can be broadly categorized into perfluoroalkyl acids and polyfluoroalkyl substances. Perfluoroalkyl acids, like PFOA and PFOS, have fully fluorinated carbon chains with a functional acid group. Polyfluoroalkyl substances, on the other hand, contain at least one carbon atom bonded to fluorine atoms and at least one other carbon atom not bonded to fluorine. This structural diversity means that their properties and environmental behaviors can vary, but the common thread is the persistent carbon-fluorine bond.

The pathways through which PFAS enter our bodies are multifaceted. Ingestion is a primary route, stemming from contaminated food and water. As PFAS leach from food packaging into the food we eat, or are present in the water we drink, they are absorbed into our digestive system. Inhalation of dust particles containing PFAS, particularly in indoor environments where these chemicals are prevalent in consumer products, is another significant exposure route. Dermal absorption, though generally considered less significant than ingestion or inhalation, can also occur through contact with products containing PFAS.

The scientific consensus is increasingly pointing towards the potential for PFAS to cause a range of adverse health effects. Research has linked PFAS exposure to several health concerns, including:

• Immune system suppression: Studies suggest that exposure to PFAS can weaken the immune system’s ability to fight off infections and reduce the effectiveness of vaccines. This is particularly concerning for children, whose immune systems are still developing.
• Increased cholesterol levels: Elevated levels of certain PFAS have been associated with higher cholesterol, a known risk factor for heart disease.
• Thyroid hormone disruption: PFAS may interfere with the production and function of thyroid hormones, which are crucial for metabolism and development.
• Liver damage: Some research indicates a potential link between PFAS exposure and liver enzyme abnormalities, suggesting possible liver damage.
• Increased risk of certain cancers: While research is ongoing and more definitive links are needed, some studies have suggested potential associations between PFAS exposure and an increased risk of certain cancers, such as kidney and testicular cancer.
• Reproductive and developmental effects: Emerging evidence suggests that PFAS may impact reproductive health, including reduced fertility, and may have adverse effects on fetal development, potentially leading to lower birth weights or developmental delays.

The persistence of PFAS in the environment is a major concern. Once released, they can travel long distances through air and water, contaminating ecosystems far from their original source. They can accumulate in soil, sediments, and surface water, posing a long-term risk to wildlife and human populations. Their presence in the food chain means that predatory animals, including humans, can accumulate higher concentrations over time.

The global nature of PFAS contamination necessitates international collaboration and concerted efforts to address this complex issue. Regulatory bodies worldwide are beginning to take action, implementing stricter limits on PFAS levels in drinking water and food. Many countries are also working to phase out the use of certain PFAS in specific applications. However, the sheer number of different PFAS compounds and the historical widespread use mean that remediation and management efforts are challenging and costly.

The development of effective alternatives to PFAS is a critical area of ongoing research and innovation. Scientists and engineers are actively seeking to create new materials and technologies that can provide the desirable properties of PFAS without their persistent and potentially harmful characteristics. This includes exploring fluorine-free alternatives for water and stain repellency, as well as developing safer manufacturing processes.

Understanding the complex chemistry of PFAS, their widespread presence, and their potential health implications is the first step towards mitigating their impact. The ongoing work by scientists like Mark Miodownik, supported by institutions like the Royal Society, is crucial in raising public awareness and informing policy decisions. As consumers, becoming more informed about the products we use and advocating for safer alternatives can also play a vital role in driving change and protecting our health and the environment from these enduring "forever chemicals." The challenge posed by PFAS is a stark reminder of the unintended consequences that can arise from the widespread use of persistent synthetic chemicals and the importance of a precautionary approach to chemical innovation.