Well, it is a bit complicated as we are talking about PFAS as the collective name for a huge group of chemicals that according to some counts include over 12,000 synthetic per-and polyfluoroalkyl substances that have unique chemical uses including as lubricants, sealants and for waterproofing and heat resistance. The real problem is that they are highly resistant to degradation both in the environment and in human bodies and have thus been dubbed forever chemicals.
Although they have been around since the 1950s, concerns about their presence and toxicity have been gradually increasing. The reason being that the physical and chemical properties that make PFAS persistent and mobile in the environment also make them particularly challenging to analyse. Analytical methods sensitive enough to detect environmentally relevant concentrations didn’t become widely available until the early 2010s.
Now PFAS contamination has been found to be global. PFAS have been detected in regions with little human activity, including the atmosphere of remote locations, the Arctic and Antarctic seas and remote soils of every continent.
But let’s start from the beginning
PFAS have existed for over 90 years with the first form, polychlorotrifluoroethylene (PCTFE), discovered in 1934 in Germany. Bought by 3M in 1957, it was commercialised under the name Neoflon for use in semiconductors, chemicals and electronic components.
In parallel and almost by accident, DuPont had in 1938 found that a frozen, compressed sample of the fluorocarbon tetrafluoroethylene had spontaneously formed a white, waxy solid that would be dubbed PTFE (polytetrafluoroethylene) and later trademarked as Teflon. It was initially used in the Manhattan Project in gaskets and valves to hold toxic uranium hexafluoride in pipes when building the first nuclear bomb. Over the next several years, the company expanded the chemical’s use into cookware, stain repellents in fabrics and textiles and industrial coatings.
Not to be beaten, 3M scientists continued their development of PFAS chemicals resulting in perfluorooctanoic acid (PFOA) in 1947 and perfluorooctane sulfonic acid (PFOS) in 1953. They were both resistant to heat, oil, stains, grease and water. In 1951, 3M provided PFOA to DuPont to be used as an aid when coating products with Teflon. Both PFOS and PFOA would go on to be used as a component in a wide variety of products for years, including Scotchgard, stain resistant carpets and later firefighting foam. The 3M company kept expanding the range of PFAS by introducing perfluorohexane sulfonic acid (PFHxS) in 1958, again to be used in stain-resistant fabrics, fire-fighting foams, food packaging, and as a surfactant in industrial processes.
Within 20 years of its initial discovery in 1934, PFAS in its many forms had gone from a laboratory accident, to an atomic bomb project component, to an ingredient in everyday household products.
The dangers of PFAS
You would have thought that when synthesising indestructible compounds they would be extensively tested for potential toxicity before being released. Very conveniently according to publicly released information PFAS were long presumed to be biologically inert. However, legal disclosures and investigative reporting later uncovered evidence that companies that manufactured PFAS knew of their toxic effects on human health and the environment by 1970, forty years before it was generally known in the public health community.
Their human toxicity and ecosystem impacts have since received extensive public, scientific and regulatory attention. Testing of human blood in the USA, starting in 1999, found PFOA, PFOS, and PFHxS, the worst of the worst, in 99% of the sampled population. By 2006, PFAS had been found in ground and surface water, in soil and sediments, and in wildlife. The toxic properties and their inability to break down in the environment and to build up in human blood had become more evident.
Mounting evidence of the adverse health effects of PFAS showed that exposure to certain levels of the forever chemicals increased cancer risk such as liver, kidney, and testicular cancers, lowered birth weight in babies, produced higher levels of cholesterol, reduced kidney function, caused thyroid disease, altered sex hormone levels, and damaged the immune system resulting in a reduced vaccine response.
In 2007 a concerned European Commission asked the European Food Safety Authority (EFSA) to review health aspects of some PFAS as there was a clear need to assess the potential risks associated with human exposure to this class of substances. EFSA, in its opinion published in 2008, concluded that it was unlikely that adverse health effects from dietary exposure to PFOS or PFOA were occurring in the general population but stressed that this opinion was based on very limited data.
However, the more we look, the more alarming the health threat appears to be. Emerging research found PFAS in consumer products such as cosmetics, packaging, waterproofing, inks, pesticides, medical articles, polishes and paints, metal plating, pipes and cables, mechanical components, electronics, solar cells, textiles and carpets. As a result two of the highest-profile compounds, PFOS and PFOA, were added to the Stockholm Convention for the protection of human health and the environment from persistent organic pollutants (POPs) in 2009 and 2019, respectively, limiting their use and production. PFHxS was added to the list in 2022. In 2023, the International Agency for Research on Cancer (IARC) declared PFOA a category one human carcinogen.
What about exposure from food and water?
Potential human exposure pathways for PFAS include inhalation, incidental soil and dust ingestion, dermal contact, diet and drinking water. Diet and drinking water are considered the main sources of human exposure to PFAS in the general population. Two main processes are thought to lead to PFAS contamination of food, namely bioaccumulation in aquatic and terrestrial food chains, and transfer from contact materials used in food processing and packaging. Local water supply is a special case with high levels of PFAS detected close to industrial sites, military institutions and fire training facilities. Apart from water, foods like fish, fruit and eggs and egg products have been shown to contribute the most to human exposure.
In 2018, EFSA changed their tune based on new information for dietary exposure and toxicity. In establishing a tolerable intake of 13 ng/kg body weight per week (TWI) for PFOS and 6 ng/kg body weight per week for PFOA, they now concluded that exposure of a considerable proportion of the population exceeded the proposed limits for both compounds.
This was further strengthened in the EFSA opinion from 2020 evaluating the combined exposure to the sum of the four most potentially dangerous compounds: PFOA, PFNA, PFHxS and PFOS. Effects on the immune system with reduced antibody response to vaccination were considered the most sensitive and thus the most critical for the risk assessment. Since accumulation over time is important, the tolerable intake was lowered to a combined 4.4 ng/kg body weight per week for the four PFAS, considered protective also to other potential adverse effects observed in humans. Unfortunately parts of the European population exceed this TWI, which EFSA concluded was a concern.
International focus on PFAS
Worldwide, regulatory PFAS guidance has been rapidly evolving, with the inclusion of a wider range of PFAS covered in advisories and a continued decrease in what is deemed safe PFAS concentrations. In the USA a recent extensive review was published in 2022 by the National Academies of Sciences, Engineering, and Medicine titled Guidance on PFAS Exposure, Testing, and Clinical Follow-Up. The review found that an estimated 2,854 U.S. locations (in all 50 states and two territories) have some level of PFAS contamination and almost 100 percent of the U.S. population is exposed to at least one PFAS. They concluded that although not all of the contamination exceed health advisories, the pervasiveness of the contamination is alarming.
In a 2023 response to the PFAS challenge, the Government of Canada published a Draft State of Per- and polyfluoroalkyl substances (PFAS) Report. The report provides a qualitative assessment of the fate, sources, occurrence, and potential impacts of PFAS on the environment and human health in Canada. With the application of precautionary assumptions that are protective of human health and the environment when addressing gaps in information, the report provides the basis for a class-based approach to inform decision-making on PFAS in Canada. The report also conclude that PFAS as a class are harmful to human health and the environment.
Japan is no stranger to chemical contamination. But despite the history, combined with Japan having one of the world’s largest chemical industries and many Japanese companies producing or using PFAS chemicals, the attention paid to these chemicals has been far less than in the USA and Europe, at least in the public domain. Some researchers have recently warned of adverse effects on humans after high concentration levels of PFAS were detected in various parts of the country, which fuelled concern among residents. A report from Japan’s Food Safety Commission proposes the first-ever daily intake limits for PFOS and PFOA linked to health risks, emphasising safety in food consumption. It suggests a tolerable daily limit of 20 ng/kg body weight for each compound.
Based on advice from EFSA, the European Commission in 2022 established maximum levels for PFOS, PFOA, PFNA, and PFHxS in eggs, fish and bivalve molluscs and meat and offal. The varying maximum levels are laid out in Regulation (EC) 2022/2388.
Regulators worldwide have proposed or regulated varying concentrations for some PFAS in drinking water. Suggested maximum levels vary from 4 ng/L in the USA to 560 ng/L in Australia. However, it is impossible to compare the suggested maximum levels between countries as they are based on coverage of different numbers of PFAS. Some limits only cover PFOS and PFOA while others include all measurable PFAS.
The future is still uncertain
To eliminate the threat posed by PFAS will not be easy as they are still used in many applications where the use is considered proprietary with information not readily available or public. Gaining a complete picture of the threat is also a challenge because of the chemical and toxicological differences among individual PFAS and uncertainty about the exposure level at which their adverse effects may occur. In addition, many of the chronic diseases associated with PFAS exposure have also myriad other causes.
Unfortunately for all of us, it is difficult to reduce exposure to PFAS through personal behaviour modifications. There are so many routes of potential dietary exposure to PFAS from non-stick cookware, grease-resistant paper, fast food wrappers, microwave popcorn bags, and retail and convenience packaging. Add to that the use of PFAS in our clothes, our furniture, cosmetics, sunscreens, shampoos, carpets, menstrual products, dental products and even in artificial turf.
The best we can do is to keep up the pressure on regulatory authorities to lower the PFAS limits in the water supply and look at banning their use in most consumer products and food packaging.
And finally let’s learn from the mistake of releasing chemicals before they have been tested for harmful effects to humans and the total environment.