Per- and polyfluoroalkyl substances (PFAS) are a vast and diverse group of synthetic-fluorinated chemicals that have become indispensable in modern life. Comprising over 12,000 known compounds, PFAS have unique chemical and physical properties that make them valuable in industrial and consumer applications. These substances are widely used in consumer products, such as food packaging, firefighting foams, nonstick cookware, stain-resistant fabrics, and electronics. However, their resistance to degradation, often earning them the name 'forever chemicals', presents significant challenges to human health and environmental safety.

The PFAS can be classified into two main categories: non-polymer and polymer PFAS. Non-polymer PFAS, including perfluoroalkyl acids (PFAAs) and their precursors, are persistent, mobile, and bioaccumulative, making them a primary focus of environmental studies. Polymer PFAS, such as high-molecular-weight fluoropolymers, are less bioavailable and generally pose lower risks. Despite their utility, PFAS contamination has only recently gained attention, with advancements in detection methods during the early 2010s revealing their presence at trace levels in air, water, soil, and even in remote ecosystems. These findings have spurred toxicological research, uncovering the bioaccumulative nature of some PFAS and their potential health risks.

Sources of PFAS and its Global Spread

The widespread use of PFAS over several decades has led to their persistence in various environmental media (air, water, soil, living organisms).

Industrial emissions are among the primary sources of PFAS contamination. Factories producing or utilizing PFAS, such as those involved in fluoropolymer manufacturing, release these chemicals into the environment through untreated wastewater and atmospheric emissions. Airborne particles and vapours containing PFAS eventually settle on land or water, leading to widespread contamination. Studies have shown that industrial discharges contribute significantly to high PFAS concentrations in nearby rivers, lakes, and groundwater systems. Another significant source is firefighting foams, particularly aqueous film-forming foams (AFFF), used to suppress high-intensity fires. The AFFF has been extensively employed at airports, oil refineries, and military installations, where its repeated use has caused long-lasting contamination of soil and groundwater. Once released, PFAS from AFFF migrate into groundwater systems, contaminating drinking water sources.

To enhance durability and resistance to heat, water, and grease, PFAS have been commonly used in everyday consumer products like non-stick cookware, waterproof and stain-resistant textiles, food packaging, and certain cosmetics. Over the products' lifecycle, PFAS leach into the environment through wear, washing, and disposal. For example, non-stick cookware can release PFAS when exposed to high temperatures, while treated textiles shed PFAS during laundering, contaminating wastewater systems. Cosmetics (foundations, mascaras, sunscreens) can contain PFAS that wash off into water systems.

Landfills and solid and liquid waste management practices can be major sources of PFAS contamination. Disposed products containing PFAS could release them into landfill leachate, which can seep into surrounding soils and groundwater, if not adequately treated. The application of biosolids—sewage treatment byproducts identified as a PFAS source—as fertilizers in agriculture further disperses PFAS into soil and crops, potentially introducing them into the food chain. Additionally, irrigation with PFAS-contaminated water impacts the agricultural systems.

Another pathway for PFAS dispersion is atmospheric deposition. Here, volatile forms of PFAS released from industrial processes or consumer products can travel significant distances in the air before settling, thereby contributing to contamination in faraway areas. With detectable levels being found even in remote regions like the Arctic, these mechanisms underscore the global reach of PFAS pollution.

PFAS are highly mobile, travelling long distances through air and water. The grasshopper effect of PFAS migration from warmer areas to cooler regions has been documented. PFAS has been detected in remote areas such as polar ice caps and deep oceans. Their presence, persistence and ability to bioaccumulate in wildlife, including polar bears and fish, highlights the ecological risks posed by PFAS as they enter the food chain and spread their impact globally.

Public Health Impacts of PFAS Exposure

Due to their persistent nature and bioaccumulative properties, PFAS exposure has been linked to a wide range of adverse health effects, impacting various physiological systems. These chemicals, particularly perfluorooctanoic acid (PFOA) and perfluorooctane sulphonate (PFOS), interfere with cellular and biochemical processes, leading to chronic diseases and long-term health consequences.

One of the most severe health effects of PFAS exposure is the increased risk of liver, testicular, and kidney cancers. The carcinogenic potential of these chemicals arises from their ability to interfere with cellular functions, including DNA repair mechanisms, promoting tumour formation over time. The PFAS also disrupt endocrine and reproductive health by interfering with hormonal systems, affecting fertility and foetal development, as well as results in low birth weight, preterm births, and developmental delays (in children).

PFAS also impair immune responses, reducing the body's ability to produce effective antibodies, which diminishes vaccine efficacy and increases vulnerability to infections, especially in children and vulnerable adults. PFAS are linked to elevated cholesterol levels, obesity, and insulin resistance that contributes to increased risks of cardiovascular diseases and type-2 diabetes. Neurodevelopmental impacts (cognitive deficits, behavioural disorders, long-term neurological impairments) also occur. Further, chronic PFAS exposure is linked to kidney diseases, including reduced renal function and non-alcoholic fatty liver disease.

Evolving Challenges of Managing PFAS

The persistence, mobility, and widespread use of PFAS make them a challenging environmental issue, necessitating robust monitoring, mitigation strategies, and regulatory frameworks to protect human health and the environment. The PFAS are chemically stable, resistant to degradation, and cause long-term water, air, and land contamination. The PFAS remediation methods are intricate and expensive. The current remediation choices (like granular activated carbon) are often costly, energy-intensive, and not widely used. Cutting-edge technologies (e.g., electrochemical oxidation) are being designed, and they are in the scaling stage now, which means they will soon be available for real-world application.

There is a link between the exposure to PFAS and several health problems, including cancer. The bioaccumulative feature of PFAS in human and animal tissues leads to additional negative health effects, necessitating extensive research to find viable and cost-effective solutions.

Contrary to the fact that there is growing evidence showing the impact of PFAS, the regulation of PFAS varies widely among the regions and countries. There is no uniformity in the global PFAS standards for drinking water and emission control or on the safety of consumer products, making global risk management more complex.

The shift from PFAS with long chains (like PFOA) to those with short chains has presented newer problems as the latter are still persistent and can move around in the environment, thus bringing about the same health and environmental risks.

Consumers often lack knowledge and awareness of the presence (and hazards) of PFAS in several everyday products like clothing, furniture, food boxes, etc. This leads to a reduction in demand for safer alternatives.

Industrial restrictions imposed for PFAS management can alter global supply chains and international trade, which needs to be addressed effectively through the sustainable development lens.

Information about the toxicity, behaviour, and alternatives of PFAS is currently limited. Further research is necessary to find out new scalable, low-cost alternatives, and improved remediation techniques.

Rising global temperatures, altered water cycles, and severe weather events possibly can result in a shift of PFAS distribution as well as the mobilization pattern, increasing the environmental and health risks, especially in vulnerable ecosystems and for underprivileged communities.

Regulatory and Scientific Responses

Initiatives to address the widespread problem of PFAS contamination have been diverse, involving regulatory actions, scientific progress, and heightened industry responsibility.

Global regulatory frameworks aim to limit PFAS contamination and protect public health. The European Union plans to phase most PFAS by 2030, while the United States Environmental Protection Agency (USEPA) has set legally enforceable levels (maximum contaminant levels or MCLs) for six PFAS in drinking water. Australia's National PFAS Management Plan (2018) adopts a risk-based approach to manage exposure and remediation. These regulations reflect growing recognition of the urgency to control PFAS pollution through stringent guidelines and proactive policies.

Advancements in PFAS detection and remediation: Since the 2010s, advancements in analytical methods have enabled the identification of PFAS at environmentally relevant concentrations, leading to:

Identification of new PFAS compounds

Correlating health risks with PFAS levels

Establishment of regulatory limits for potable water and environmental media

However, as currently available analytical methods detect only a fraction of PFAS, there will be significant detection gaps. With regards to remediation, technologies such as granular activated carbon (GAC) and ion exchange resins have been widely used to remove PFAS from contaminated water, but they only concentrate PFAS on another medium. Emerging destruction techniques such as plasma-based technologies and electrochemical oxidation have been developed to break down the robust PFAS compounds into harmless byproducts. These scientific solutions are crucial for addressing PFAS contamination at its source and minimizing its long-term impacts.

Industry accountability: Through various regulatory frameworks and legal actions, industries are being held accountable for PFAS pollution. Increased public awareness and subsequent demands for safer alternatives are compelling businesses to transition to less hazardous substances, thereby reducing reliance on PFAS compounds. This shift reflects a growing trend towards sustainable practices and corporate responsibility, driven by both societal expectations and regulatory compliance.

The combined regulatory, scientific, and industrial responses constitute a comprehensive strategy for alleviating PFAS contamination. Ongoing collaboration and innovation across sectors are essential for effectively managing and ultimately eradicating the risks associated with these persistent chemicals.

Conclusion

The PFAS represent one of the most pressing environmental and public health challenges of the 21st century. Their persistence, mobility, and bioaccumulative characteristics have resulted in widespread contamination and significant health risks. Addressing PFAS necessitates immediate and coordinated action, integrating stringent regulations, innovative remediation technologies, and international collaboration. As scientific knowledge advances, adaptive strategies must be formulated to mitigate PFAS risks and protect ecosystems and human health. By prioritizing sustainable solutions and fostering collective action, we can pave the way for a healthier, more sustainable future while effectively addressing the challenges presented by these 'forever Chemicals'.

Bibliography

United States Environmental Protection Agency (USEPA). 2020. Landfill leachate and PFAS

United States Environmental Protection Agency (USEPA). 2020. PFAS master list of chemical substances  #