PFOA and PFOS have been shown to be extremely persistent chemicals, both in the environment and in human tissue. A recent study has linked these chemicals to serious damage to the immune system in children (Grandjean et al, 2012). But PFOA and PFOS are just two of a family of fluorochemicals called PFCs, which in turn are part of the fluorocarbon family. Some manufacturers of domestically applied water-repellents claim that because their fluorocarbon products are PFOA or PFOS free, that they are risk free. Is that true? The following questions and answers should help you to make up your mind.
Dr. Philippe Grandjean of the Harvard School of Public Health discusses the issues raised by his recent research into the effects of PFCs on children.
What is the range of health issues that have been associated with PFCs in human and animal studies?
- Damage to immune system in children leading to an inability to respond to inoculations for tetanus and diphtheria (Grandjean et al, 2012).
- Increased incidence of cancer associated with PFC pollution (Bonefeld-Jorgensen et al, 2011)
- Compromised female fertility associated with PFC blood levels in women – delayed time to conception (Fei et al, 2009)
- Enlarged livers associated with PFC
- Low birth weight associated with PFC
- Reduced fertility associated with PFC
Does the claim "PFOA and PFOS free" demonstrate that a waterproofing product is not a fluorocarbon?
PFOS and PFOA are just two of the family of chemicals called perfluorinated compounds (PFCs). All fluorocarbon water-repellents are made with PFCs or products that can biodegrade to PFCs.
What is the difference between a PFC and PFOS or PFOA?
PFC is the name given to the broad family of products called perfluorinated compounds. PFOS and PFOA belong to that family. PFOS and PFOA are therefore both PFCs. The difference between family members is primarily determined by how many carbon atoms are in the perfluorinated chain. PFOS and PFOA are both Octyl, that is, they both have 8 carbons.
What is the difference between a C6 and a C8 PFC?
PFOA and PFOS are both C8 PFCs. That means that they have 8 carbons in their chemical backbone. C6 PFCs are exactly the same, except that they have 6 carbons in their chemical backbone. PFHxA, the C6 equivalent to PFOA, is a persistent material but may not bio-accumulate in humans as much as PFOA. On the other hand PFHxS, the C6 equivalent to PFOS, is also persistent and bio-accumulates just as much, and possibly more than PFOA or PFOS (US Environmental Protection Agency, 2009; Lasier et al, 2011).
Are PFOS and PFOA the only members of the PFC family shown to be potentially carcinogenic
Many members of the family, including some with fewer than 8 carbons have been shown to cause changes in cells that may lead to the development of tumors (Trosko and Ruch, 1998; Upham et al, 1998).
Are PFOS and PFOA the only members of the PFC family shown to be persistent in the environment, and to bio-accumulate in humans, or in other animals?
Not at all.
Most PFCs are potentially persistent in the environment and many bio-accumulate, including some which have carbon chains which are shorter than 8 (Dimitrov et al, 2004; Lasier et al, 2011; USEPA,2009).
How could a so-called PFOA-free fluorocarbon, which has been tested and found to be safe for pond life, degrade into dangerous PFOA?
PFCs are the chemical building blocks from which fluorocarbon water-repellents are made. When the PFC is chemically bonded into the fluorocarbon water-repellent, it is held safely in a large molecule that is non toxic. These large fluorocarbon water-repellent molecules contain fluorotelomers. As the fluorotelomer ages, it is biodegraded in the environment, or oxidizes, splits up, and releases smaller toxic PFC acids. If the fluorotelomer is based on a C8 PFC, then the end product of the biodegradation will be PFOA. So a so-called PFOA-free product can, over time, release PFOA into the environment (Dimitrov et al, 2004; Dinglasan et all, 2004; Ellis et al, 2004).
How long will it take for fluorocarbon water-repellents, or fluorotelomers, to degrade to dangerous PFC acids (of which PFOA is an example)?
There has been disagreement on how long the process will take. There is now general agreement that it does take place in a sufficiently short time to contribute to PFC pollution.
One study shows that trout which have been fed fluorotelomer subsequently convert the material to PFC acids in their livers (Butt et al, 2010). Therefore, in theory, the degradation can happen via digestion. This is a particularly important point to be taken into consideration when assessing whether fluorocarbon water-repellents should be used in the home. Food contamination could lead to the absorption of PFC acids direct into the body as a result of digestion.
The fluorocarbon industry produced research that indicated that biodegration in soil was an extremely slow process, taking thousands of years. However, when the US EPA repeated the research, they calculated a much faster rate of biodegradation and concluded that, "fluorotelomer-polymer degradation is a significant source of PFOA and other fluorinated compounds to the environment". Soil degradation is only one way in which the fluorocarbon water-repellents convert into more toxic PFC materials. (Washington et al, 2009)
Are C6 PFC based fluorocarbon water-repellents proven to be entirely safe?
C6 based fluorotelomers will degrade and biodegrade to PFC acids in the same way as C8 fluorotelomers. Although the ultimate biodegradation product, PFHxA, may be less dangerous to humans and the environment than PFOA, it is still potentially dangerous. Furthermore, PFHxA is only one of a group of chemicals which will result from the biodegradation of C6 fluorotelomers. As well as PFHxA, fluorotelomer acids – bigger chunks of broken up fluoropolymers – will be produced in the biodegradation process. Fluorotelomer acids have been shown to be at least as toxic to aquatic life as smaller PFC acids (Michelle. M. Phillips, 2007).
Are PFCs the only members of the fluorocarbon family to bio-accumulate in humans, or in other animals
In a study of beached dolphins and porpoises in Chinese waters, a range of PFC compounds and other fluorocarbon chemicals, including PFOA and PFOS were found at high levels. But up to 70 per cent of the fluorocarbon material found in the dolphins was found to be unknown fluorocarbon chemicals (Yeung et al, 2009). This implies that not just the main PFOS and PFOA acids are bio-accumulative, but also a range of fluorocarbon materials that may come from varied sources, including the biodegradation products of fluoropolymers or pesticides.
Are fluorocarbon water-repellent liquid products for use in the home marked " PFOA or PFOS free" completely safe for the user?
For all of the reasons mentioned above, all fluorocarbon water-repellents should be considered potentially hazardous for domestic use. To conclude, the factors below contribute to the conclusion that fluorocarbon water-repellent liquids are not ideal for use in the home:
- Liquids introduced into kitchens for use in washing machines can potentially cross-contaminate food.
- Fluorocarbon water-repellents biodegrade to a range of PFC acids including fluorotelomer acids
- Fluorotelomers, used in Fluorocarbon water-repellents, have been shown to biodegrade in rats and trout to PFC acids, and therefore may biodegrade via human digestion.
- PFOA and PFOS are just two examples of a family of toxic PFC acids
- PFC acids have been shown to be persistent in human tissue
- PFC acids have been linked to damage to the immune systems of children.
- The level of PFC acid required to potentially damage the human organism is extremely low: 10's of parts per billion. This would be the equivalent of less than a hundredth of a headache tablet, by weight, distributed in the whole body (Grandjean et al,2012).
- Humans cannot effectively excrete PFC acids (although some may be more easily excreted than others). Therefore PFC acids build up progressively in the human bloodstream over time even if there is a very small source of them.
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