PFCs: A case study in favour of the precautionary principle

December 15, 2011 at 12:59 pm | Posted in H&E Features | 5 Comments

PFCs are an example of how production and marketing of a substance can outpace scientific research into its safety and placing regulatory restrictions on its use. In the case of PFCs, this has resulted in 3 generations of people being exposed to an unknown hazard while a complex consensus, based on weak data and economic interests, develops around restricting their use.

Here we summarise the emerging issues around PFCs and argue that, had the precautionary principle been applied to their production, then we would not now be facing unknown risks from their continued use.

PubMed citation counts per year for PFCs. These graphs are not a reflection of the absolute number of all PFC studies but are to illustrate the research trend. Note that research is only picking up long after PFC production began. Click to enlarge.

Poly- and perfluorinated compounds (PFCs) are a minor miracle of chemistry, supremely versatile and produced in as many as thousands of varieties. Being soluble in water, yet also oil- and water-repellent, they are useful in a range of applications, from stain repellents such as Scotchguard to layering Teflon onto non-stick cookware.

PFC molecules gain their properties from two basic parts: a water-soluble head and a fluoridated tail. The fluoridated tail is highly inert, resistant to thermal degradation and environmentally stable. The head readily attaches itself to fabric and paper while the tail repels liquids and oils, allowing stain- and water-resistant coatings to be applied to clothing and grease-proof papers.

PFCs also find widespread use as surfactants – agents which allow two liquids that do not normally mix (such as fat and water) to dissolve into each other. This makes them useful as leveling agents in paints, as an intermediate in the production of fluoroacrylic esters and for the manufacture of fluoropolymers (such as Teflon).

PFCs have been produced in industrial quantities since the 1950s, beginning in the USA when firstly 3M and then DuPont began synthesizing PFOA. At that time, companies were under no statutory obligation to either perform rigorous testing or disclose any significant environmental or toxicity data they might have had on their products.

DuPont sounded early internal warnings about the safety of PFOA in 1961 and carried out further studies on workers in 1981. The company’s failure to notify the US Environmental Protection Agency of the results of these studies became the basis of a 2004 EPA case against the company for not meeting its obligations under the Toxic Substances Control Act.

Overall, the occupational and animal testing carried out up to the late 90s was broadly inconclusive. Although DuPont considered it had enough evidence to self-impose a limit of 1ppb emissions into waterways, the consensus at the time appears to have been that the sample sizes in the studies were too small to force regulatory restrictions on the use of the substance. DuPont’s occupational studies indicated an increased risk of prostate cancer among workers exposed to PFOS and some suggestion that PFOA is a teratogen, with an unusually high incidence of female workers giving birth to children with birth defects.

A watershed moment came in August 2001 when the first class-action lawsuit alleging property and health damage from PFC exposure was filed against DuPont by residents living near the company’s Wood County, West Virginia (USA) Teflon plant. DuPont was found guilty of knowingly exceeding its own guideline limits on PFOA release into local waterways and is liable for compensating residents for medical conditions identified as resulting from PFOA exposure (Clapp & Hoppin, 2009) By this time it was also clear that human exposure to PFOA was ubiquitous, with 98% of the US population having detectable levels in their blood (Calafat et al. 2007).

In the last decade we have since seen a rapid increase in the number of toxicity studies on the substances, but before then research was held back by several major challenges in assessing the toxicity of PFCs and their presence in the environment.

The first is determining whether or not they are even there in the first place. Typically present in the environment at parts-per-billion concentrations, until the early 2000s exposure levels were below the limit of detection of equipment typically affordable by laboratories. Prior to then, human exposure could inferred from occupational surroundings, or measured if high enough, but only looking at workers limited sample size and the ability to make correlations between exposure and health outcomes.

Food contact paper, thread sealant tape, stone, tile and wood sealants, and carpet-care liquids have the highest concentrations of PFCs. Source: Wikipedia / Guo et al. (2009). Click to enlarge.

The second challenge is the often almost extreme, yet highly unpredictable, persistence of PFCs in the body, which varies tremendously not only from one species to the next but even one gender to the next. For example, PFOA half-life is 6 days in male rats, only 4 hours in females, but 5.4 years in humans (in whom gender makes little difference at all). The PFC found to be most persistent in humans so far is perfluorohexanesulfonate (PFHxS), with a half-life exceeding 8 years.

Long half-lives complicate epidemiology and understanding of exposure routes of people to PFCs, as modifications to behaviour, diet or occupation can take years before they result in measurable changes in PFC levels in a person’s body. This makes drawing out correlations between behaviour, diet, and occupation and exposure, and then exposure and health outcomes, much more difficult.

Academic research into PFCs really took off when affordable, reliable detection technology became available. This made it easier to perform more fine-grained exposure assessments and epidemiological studies, precipitating a relative flood of toxicological research beginning around 2006.

These more recent studies have in particular found associations between PFOA and higher cholesterol levels, with implications for cardiovascular disease, and elevated uric acid levels, which may increase risk of hypertension and cerebrovascular disease. Steenland et al. (2010) provides a good open-access summary of the epidemiological data.

Exposure routes consist of the usual suspects, with particularly elevated PFC levels seen in people who consume fish or water from contaminated waterways. House dust may be a significant source of exposure, especially for toddlers with their hand-to-mouth behaviours. There is some evidence that crops grown on contaminated soil may accumulate PFCs. This may present an exposure issue for the general population as sewage sludge can be relatively heavily contaminated with PFCs and their degradation products. Overall, food is considered to be the source of 90% of people’s exposure to PFCs, although these figures are produced by modeling subject to the many uncertainties described above.

Evidence of general exposure, toxicity, persistence and bioaccumulation of PFOS has accumulated to the point where regulatory action is beginning to be taken. PFOS and related compounds (numbering 96 in total) have been listed under Annex B of the Stockholm Convention, classifying them as persistent organic pollutants (POPs) and restricting their use to essential applications. The US EPA set a voluntary target of 95% reduction in emissions in PFOA and related compounds by 2010; the 8 companies which signed up to the targets (including 3M and DuPont) have shown a 70-100% reduction in emissions since 2001.

Overall, of the many PFCs it is only the use of PFOA and PFOS which are being subjected to the majority of research and regulatory scrutiny. Other PFCs such as PFHxS and perfluorononanoic acid (PFNA) are being detected in increasing concentrations in environmental and human samples. Perfluoralkyl phosphate esters (PAPs) and phosphoric acids (PFPAs) have recently been found in environmental matrices at concentrations similar to PFOA and PFOS. PAPs have also been found in human serum.

Measures to reduce exposure to PFOS and PFOA are meeting with some success, at least in Western nations, with US NHANES data showing recent declines in levels in humans which are consistent with the reduction in production in the US. Norwegian data show similar declines. However, in China PFOS exposures have dramatically increased, although PFOA exposure remains relatively limited.

We are only just now beginning to develop a picture, impossible 60 years ago, of how people are exposed to PFCs and what the consequences of this may be. What this means, however, is that research and regulatory initiatives are only just beginning to gather momentum at a time when there are already as many as several thousand PFCs in production, with unknown combined toxicity, to which 3 generations of people have now been exposed to an unknown degree.

It may turn out to be the case that PFCs are, for the most part, relatively harmless. However, we are going to determine this by gathering data from the millions of people being exposed to these substances before we have determined whether or not they are safe. We have done this many times already, with PCBs, asbestos, formaldehyde, dioxin and lead – tallying up the damage in human lives before taking action – so we had better hope that PFCs really are safe.

Generic PFC structures. The 8-carbon (8C) structures are shown. The 8C, or "long-chain" structures are generally the most persistent. Click to enlarge.

PFCs are ultimately another illustration of the importance of the precautionary principle in chemicals policy. Currently, the economic benefits of continued PFC production are being weighed against unknown harm they pose to the environment and health. However, even for PFOA and PFOS, thorough research only goes back about 13 years with the majority of studies only being published in the last 8 years, and toxicity studies only in the last 5. This is not the sort of data which can prove that PFCs are harming health, so cannot form the basis of a consensus that harm to health outweighs the economic benefits of continuing to market PFCs.

This mindset, however, results in data on PFCs being generated by measuring people’s exposure and correlating this with increased incidence of ill health. This requires we make people ill in order to justify restricting the use of PFCs – surely an unacceptable way of finding out the PFCs are harmful, yet exactly what has happened with PFOS and PFOA for 60 years and counting.

The alternative is to make sure a pedigree of safety for a substance is established before it is brought to market. This application of the precautionary principle is not reactionary or over-conservative. It simply acknowledges that the slow consensus-building process we see with PFCs, where existing economic benefits and producer interests are balanced against weak data on health effects, is inadequate for protecting the health of the millions of people exposed to PFCs over the decades it takes for that consensus to emerge.

If the precautionary principle had been in play when PFCs were first discovered, we would have been much clearer about the environmental and health risks they pose and been able to make a rational decision based on clear data about whether or not they should be manufactured: if the data was not available, they would not have been produced, and we would face no risks now; alternatively, if the data had shown they were safe, they would have been produced, and the likelihood of our facing a risk now would have been substantially reduced. Instead, we have a muddy process based on emerging data where all we know is, if PFCs do turn out to be harmful, we will regret ever making them in the first place.

Further Reading

Lindstrom AB, MJ Strynar, E Laurence Libelo (2011). Polyfluorinated Compounds: Past, Present, and Future. Environmental Science & Technology 2011 45 (19), 7954-7961

5 Comments »

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  1. A thoughtful and well written piece !
     

    It is so unfortunate that there has been a lack of testing of products for safety with regard to toxicity and effects on human health. Historically, those involved in Product Development have very often been negligent. Having begun my career in the late 1960’s in Plastics and Product Technology I remember quite well the general disregard for safety in product development and manufacturing.

     
    After developing PBDE and Antimony Trioxide Flame retardants for NASA, as a member of the team I asked when we would send our spandex fire retardant materials out for toxicological testing and being told ” that’s not our problem. We solved the problem for NASA now on to the next development project.” Little did we know that we created a scourge that would afflict the planet decades later. If the ‘Precautionary Principle’ had been exercised then, none of this would have happened.
     
    Since that time I have become socially and environmentally responsible. With years and study come wisdom and greying hair. In my retirement I have been active with my Senator to see PBDE’s removed from all products and now finally a letter from EPA indicates positive action.
     
    With regard to Fluoropolymers, Dupont had information early in the game but conveniently would not release it to the public. Back in the seventies we did have info but the sources seemed to magically dry up. Later, information began to be posted on the Internet. Those who posted negative information about the dangers of Teflon were told by Dupont to take down information or face a legal action.
     
    Everyone who is using non-stick cookware, persons involved in the manufacture of PTFE & Fluoropropylene copolymers and involved in manufacturing products made from Fluoropolymers such as Wire & cable, Non-stick cookware, appliances, grease resistant coatings etc. should beware. It has been known for many decades that the products of thermal decomposition from Fluoropolymers are very dangerous to human health. Unfortunately manufacturers of these products have been very diligent to hide and conceal the truth of that danger from the public.
     
    The only position Dupont can take is that their products are safe. An admission of the facts and dangers of C8 chemicals and the dangers from exposure to the products of thermal degradation of Fluoropolymers leaves them vulnerable, defenseless and open for lawsuits.
     
    In 2003 the publication known as “The Analyst” a trade magazine, published a paper written by David A. Ellis et al. at the Department of Chemistry, University of Toronto in Canada. In that paper the authors identified some of the products of thermal decomposition from the plastic polymer PTFE aka Teflon and other trade names.
     
    The authors did not consider gases such as carbonyl fluoride, hydrogen fluoride, & perfluoroisobutylene which are also released. Only the 19 novel decomposition products were considered and these were found released starting at 250 degrees centigrade.
     
    It should be noted that inhaled Carbonyl Fluoride Gas breaks down immediately when it comes in contact with the moist surfaces of the nose, throat and lungs. The decomposition products are Hydrogen Fluoride and Carbon Dioxide. The Hydrofluoric acid formed on moist surfaces causes permanent scaring of tissue. In the lungs it causes Bronchiolitis obliterans, a condition often misdiagnosed and sometimes classified as Asthma (mild scaring) and COPD (severe scaring). Tomography of the lung revels distinct mottling. The results are cumulative with exposure and worsening symptoms are irreversible.
     
    Here is a section of the paper quoted below:
     
    “The use of F NMR and mass spectrometry for the elucidation of novel fluorinated acids and atmospheric fluoro- acid precursors evolved in the thermolysis of fluoropolymers.”
     
    Authors: David A. Ellis et al Department of chemistry university of Toronto”. Thermal decomposition of PTFE begins at 250 degrees centigrade or 482 degrees Fahrenheit. The following are some of the decomposition compounds cited in the scientific paper:
     
    Table 1:
     
    “Chemical names, formula and acronyms of structures shown in Fig. 1 Structure Name Compound formula Acronym (PF-PerFluoro) “
     
    “(I) Trifluoroacetic acid C2HF3O2 TFA
    Pentafluoropropionic acid C3HF5O2 PFPrA
    Heptafluorobutyric acid C4HF7O2 PFBA
    Nonafluoropentanoic acid C5HF9O2 PFPeA
    Undecafluorohexanoic acid C6HF11O2 PFHxA
    Tridecafluoroheptanoic acid C7HF13O2 PFHpA
    Pentadecafluorooctanoic acid C8HF15O2 PFOA
    Heptadecafluorononanoic acid C9HF17O2 PFNA
    Nonadecafluorodecanoic acid C10HF19O2 PFDA
    Heneicosafluoroundecanoic acid C11HF21O2 PFUnA
    Tricosafluorododecanoic acid C12HF23O2 PFDoA
    Pentacosafluorotridecanoic acid C13HF25O2 PFTrA
    Heptacosafluorotetradecanoic acid C14HF27O2 PFTeA “
     
    “(II) These compounds are largely unreported in the literature. For simplicity we have elected to name them as the ether of the corresponding perfluoroacid. “
     
    “(III) Dichlorofluoroacetic acid C2HFCl2O2 DCFA
    (IV) Chlorodifluoroacetic acid C2HF2ClO2 CDFA
    (V) Difluoroacetic acid C2H2F2O2 DFA
    (VI) Monofluoroacetic acid C2H3FO2 MFA
    (VII) Hexafluoropropene C3F6 HFP
    (VIII) Chloropentafluoropropene C3F5Cl CPFP “
     
    In summary, toxic thermal decomposition products of Fluoropolymers are cumulative and should be avoided. Fluorinated chemicals can be found in the blood and all major body organs. They have a particular affinity for brain tissue and may contribute to dementia and possibly Alzheimer’s disease.
     
    No one should have C8 chemicals in their blood or tissue. This alone should be grounds to seek damages against Dupont and others contributing to the destruction of Public Health. Personally, I often do not believe manufacturers and with regard to Fluoropolymers and Fluorinated chemicals in my opinion they have lied for decades protected by certain Washington lobbyists.
     
    “In the face of uncertainty about the consequences of an action, but in the knowledge the action may be harmful, then it is better to avoid the action until its consequences are better understood.”
     
    Anthony Samsel, Retired Consultant Arthur D. Little, Inc. Cambridge, MA

  2. Thanks for the update. This blog post and the mentioned paper reports from an US-perspective when it comes to the regulatory aspects. How does it looks like in EU? I know that PFOS has been forbidden in the EU since 2008 (directive 2006/122/EG http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2006:372:0032:0034:EN:PDF). What about the other substances, are they produced in volumes over 1, 10 or 100 tonnes (the REACH data requirement steps)?
     
    Seems like the bisphenols might be a similar story. The ones we know something about are slowly being replace by similar substances we do not know anything about.

  3. […] process involves a lot of educated guesswork. The process is therefore not without its critics (as readers of H&E will know). The problem is, if things did not already look unreliable enough, the […]

  4. […] ago in a very different world. The pace of scientific research has accelerated exponentially (see this example about PFCs) while social media has completely transformed communication. Even review methods have […]

  5. […] PFCs: A case study in favour of the precautionary principle. PFCs are an example of how production and marketing of a substance can outpace scientific research into its safety and placing regulatory restrictions on its use. In the case of PFCs, this has resulted in 3 generations of people being exposed to an unknown hazard while a complex consensus, based on weak data and economic interests, develops around restricting their use. (December 2011) […]


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