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PFCs Last Forever

PFCs: Global Contaminants: PFCs Last Forever

April 3, 2003

April 2003

3M: PFOA is “...completely resistant to biodegradation”

EPA: “PFOA is persistent in the environment. It does not hydrolyse, photolyse or biodegrade under environmental conditions.” [Extract | Full Document]

Speed is of the essence in the ongoing government reviews. Every new molecule of PFOA produced by the chemical industry in the coming years will be with us forever. PFOA never breaks down.

 

Even if PFOA were banned today, the global mass of PFOA would continue to rise, and concentrations of PFOA in human blood could continue to build. Long after PFOA is banned, other PFC chemicals from 50 years of consumer products will continue to break down into their terminal PFOA end product, in the environment and in the human body.


Table showing half-lives of various industrial pollutants



Between 1973 and 1988 PCBs, DDT, and related chemicals were banned from use in the U.S. and abroad when it was discovered that their persistence and toxicity, combined with their ability to build up in the food chain and in people, were wreaking havoc on the environment.

Even as these notorious compounds were very publicly phased out and replaced by safer substances, studies performed on perfluorinated chemicals like PFOA were indicating that they also were persistent and bioaccumulative. As these studies were completed, PFC products were quickly making their way into every household in the U.S. in the form of 3M's Scotchgard and Scotchban products, DuPont's Stainmaster and Zonyl products, and DuPont's Teflon.

Industry scientists knew as far back as 1976 that PFCs like PFOA would resist breaking down in the environment. In a technical report summary of biodegradation tests, 3M scientists expound on the persistence of their chemicals in the environment:

“A vast array of organic compounds can be completely degraded by microorganisms. So vast in fact that it was once believed by some that given enough time and the proper conditions, microorganisms could degrade any organic material. This doctrine of microbial infallibility is still a common misconception...

Perfluorinated compounds are extremely resistant to biodegradation... Although compounds with single fluorines have been shown to release fluoride ions as a result of biodegradation, perfluorinated compounds have rarely or never been shown to undergo natural degradation. For this reason, no modification of the perfluoro components of compounds in this study was anticipated.” [1]).


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In 1978 PFOA was confirmed to be “completely resistant to biodegradation” in a study done by 3M to substantiate a similar finding in a 1972 National Academy of Sciences report [Degradation of Synthetic Organic Molecules in the Biosphere, NAS 1972). (FC-95 and FC-143).] The primary finding of the new 3M study — “...the results of this study suggest that these chemicals are likely to persist in the environment for extended periods unaltered by microbial catabolism” [1] [Extract | Full Document]. Subsequent studies showed that PFOA in water does not break down, either via the energy of sunlight or through reactions with water itself, processes called aqueous photolysis and hydrolysis. [2, 3]

Collectively, these studies show that PFOA does not break down by any known environmental degradation mechanism: hydrolysis, photolysis, or biodegradation. It is also not broken down in the human or animal gut, but remains unchanged in the body, and stays for years once it finds its way in.


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Unlike other persistent organic pollutants, all of which have some capacity to breakdown in the environment, PFOA will persist indefinitely even if banned, and will continually redistribute throughout the environment, the food chain, and the human population. PCBs and DDT have declined in total global mass in the decades following their respective bans in many countries, but the same will not be true for PFOA.


Persistent Organic Pollutants

 

3M touts perfluorinated compounds on its website:

"It's a good guess that somewhere in the world each day there is someone giving thanks for the powers of Scotchgard protection, that groundbreaking, invisible wonder created by scientists at 3M nearly 50 years ago." [4]


3M's own studies indicated that their "invisible wonder" chemicals were more persistent than DDT, PCB's and Dieldrin. In the late 1970s biodegradation studies performed by 3M indicated that PFOS and PFOA would not biodegrade in activated sewage sludge, a medium rich in microbes and used in standard indicator tests to define upper-bound rates at which bacteria can break down chemicals.

DDT has a reported half-life of seven hours (the time required for half the original mass of chemical to break down) in activated sewage sludge [5], and a half-life of up to 15 years in soil field plots [5]. Up to 66 percent of the commercial PCB mixture called Aroclor 1242 degraded after 28 days of exposure to activated sewage sludge. [6] Dieldrin has been reported to have a half-life of seven years in soil field plots. [7] In contrast, studies performed by 3M in 1976 and 1978 showed that PFOA, PFOS, and other terminal breakdown products of PFC products do not degrade at all, even in activated sewage sludge, giving them an infinite half-life.

Some PFCs break down, but the breakdown chain stops at PFOA, PFOS and other terminal products. Later studies indicated that some PFCs related to PFOS were capable of undergoing biodegradation, but analysis of the biodegradation products revealed that these chemicals decompose to terminal, non-biodegradable PFOS and PFOA [9] (Figure 1).


Figure 1. [Excerpt | Full Document]

Figure 2



Fluorotelomers break down into PFOA, which never breaks down. Of the fluorotelomers, used in Stainmaster and Zonyl paper and fabric protectors, DuPont's Korzeniowski is quoted in the April 12, 2001 edition of Environmental Science and Technology, as saying:

"PFOS seems to behave differently from our products [fluorotelomers]." and "Scientific information and studies on these materials are too limited to say whether they break down or not." [10]

But two separate studies show that fluorotelomers are not so different from the 3M compounds, in fact in some cases after biodegradation they are the same compounds, one published in the peer-reviewed literature in 1981, and another recently sponsored by 3M. In both of these studies, scientists found that biodegradation of the fluoroteolomers results in PFOA and other chemicals in the PFOA family with differing carbon chain lengths (the perfluorinated carboxylic acids).

For example, 3M found that after the Zonyl BA-type mixture of telomer alcohols was exposed to activated sewage sludge for 16 days, the mixture of fluorotelomers had largely decomposed to perfluorinated carboxylic acids containing between 5 and 12 carbon atoms [11] [Extract | Full Document]. Degradation of the longer chain fluorotelomers (16 carbons in length) was too slow to measure.

Scientists at Pace Analytical Services explain that each fluorotelomer alcohol will biodegrade to two perfluorinated carboxylic acids (PFOA and related chemicals), an acid containing one fewer carbon than the initial telomer, and an acid containing two fewer carbons than the initial telomer alcohol (Figure 2). [11] The fluorotelomer alcohol with a ten-carbon chain breaks down predominantly to PFOA.


Figure 2.

Figure 2



Degradation by hydroxyl radicals in the upper atmosphere (the troposphere) is another important means of environmental degradation. United Nations Environmental Program guidelines suggest that a compound with an atmospheric half-life of two days or five days or more should be considered persistent [12]; this is because atmospheric transportation is such a rapid method of molecule transport.

DDT, the PCB mixture Aroclor 1242, and Dieldrin have been reported to undergo decomposition by hydroxyl radicals with half lives of 5 days, 4.6 to 98 days, and 42 hours respectively [13]. POSF (a semivolatile precursor of PFOS), on the other hand, is proposed to undergo degradation with a half-life of greater than 3.7 years, if it occurs at all (in six of seven experiments, researchers observed no degradation of POSF) [14]. This greatly exceeds the UNEP recommendation and provides more evidence that the perfluorinated compounds are more persistent than the chlorinated compounds that raised such great concern in the 1970s. And PFOS and PFOA are not believed to degrade at all by this mechanism.

Studies indicate that PFOA and PFOS are also resistant to hydrolysis, another major means of environmental degradation, and although many PFOS derivatives are expected to undergo slow hydrolysis (N-EtFOSE-alcohol has an estimated hydrolysis half-life of 6.3 years or more than 27 years, in two studies), PFOS is the ultimate product of hydrolysis.

Slow breakdown rates of consumer product chemicals to PFOS and PFOA is a concern. EPA forced 3M to phase out use of its Scotchgard PFOS chemicals in May of 2000 because of concerns about current levels of PFOS in human blood in relation to levels shown to harm lab animals. EPA’s regulatory posture on PFOA also stems from concerns over current levels in humans. In both these cases, even if a total global production ban were in place, concentrations might continue to rise in human blood as the chemicals in consumer products (Stainmaster telomer alcohols, the original Scotchgard ingredients, and others), slowly break down in the environment over several decades to their terminal degradation products — PFOS and PFOA.

Some PFCs can build up in the food chain, to concentrate in humans.

Although early bioconcentration studies on PFCs were not without errors, they did indicate that PFCs would have the potential to build up in the food chain. In 1979, 3M’s Environmental Laboratory found that fish exposed to effluent from the Company's Decatur, Alabama fluorochemicals plant had significant concentrations of PFOS and Scotchgard’s raw ingredient N-Et PFOSE-alcohol. The authors concluded that these compounds build up, or bioconcentrate, in fish.

In 2003, in research supported by Health Canada and Environment Canada, Martin and coworkers determined that some PFCs could build up in the food chain to the same extent as PCBs [15], which despite their having been banned more than a quarter of a century ago, continue to render freshwater fish unsafe to eat in waters across 38 states [16].

PFOA is known to contaminate the food chain, including wild fish, other wildlife, and food on grocery store shelves [Extract | Full Document], but Martin’s study shows that other PFCs have a much greater potential to pollute the food supply. The bioconcentration factors (BCFs) reported for some of the longer-chain compounds in the PFOA family are equivalent to those for PCBs. These chemicals, like PFOA, are breakdown products of fabric and paper protection formulations (Table 1).


Table 1.

Chemical

Source in the environment

Bioconcentration Factor (potential to contaminate the food chain and concentrate in humans)

Known food supply contamination

PFOA (Teflon, Stainmaster)

Pollution from Teflon plants, offgas from Teflon, breakdown product of Stainmaster and other PFC products

4.0 ± 0.6

Found in produce, meat, and bread in grocery stores

PFDA (10-carbon version of PFOA)

Breakdown product of Stainmaster and other PFC products

450 ± 62

No tests available

PFOS (Scotchgard)

Breakdown product of 3M’s old Scotchgard formulation (pre-2000)

1,100 ± 150

Found in [list products]

PCBs (Aroclor 1242)

Banned chemicals, formerly used in electrical capacitors and other industrial applications

1,000 to 25,900

Widely contaminates meat and dairy products around the world

PFUnA (11-carbon version of PFOA)

Breakdown product of Stainmaster and other PFC products

2,700 ± 400

No tests available

PFDoA (12-carbon version of PFOA)

Breakdown product of Stainmaster and other PFC products

18,000 ± 2700

No tests available

PFTA(14-carbon version of PFOA)

Breakdown product of Stainmaster and other PFC products

23,000 ± 5300

No tests available


Source: Environmental Working Group compilation of BCF data in the peer-reviewed literature.


References:

  1. 3M. 2000. Biodegradation study of PFOS. US Environmental Protection Agency Administrative Record Number AR226-0057.
  2. 3M. 2001. Screening Studies in the Aqueous Photolytic Degradation of Perfluorooctanoic Acid (PFOA). U.S. EPA Administrative Record AR226-1030 Photolysis E00-2192.
  3. 3M. 2001. Hydrolysis Reactions of Perfluorooctanoic Acid (PFOA). U.S. EPA Administrative Record AR226-1030a090.
  4. 3M. About 3M. available online at www.3m.com/about3m/innovation/inventors_hall/index.jhtml.
  5. HSDB. DDT. available online at http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?HSDB.
  6. HSDB, rciHTH. 1981. J Water Pollut Contr Fed 53: 1503-18.
  7. Institute, HRcwHCIaT. 1992. Biodegradation and Bioaccumulation Data of Existing Chemicals Based on the CSCLJapan, Japan Chemical Industry Ecology — Toxicology and Information Center.
  8. Company, M. 1976. Biodegradation Studies of Fluorocarbons. U.S. EPA Administrative Record AR226-0356.
  9. 3M. 2001. Executive Summary of Biodegradation Studies. U.S. EPA Administrative Record AR226-1030a107.
  10. Renner, R. 2001. Growing Concern over Perfluorinated Chemicals. Environ. Sci. and Technol.: 154A-160A.
  11. Services, PA. 2002. Biodegradation Study Report: Biodegradation Screen Study for Biodegradation Screen Study for Telomer Type Alcohols,. U.S. EPA Administrative Record AR226-1149.
  12. UNEP. 1999. available online at www.chem.unep.ch/pops/POPs_Inc/INC_2/en/infs/inc2_inf2.htm.
  13. Syracuse Research Corporation., Meylan W.M. and Howard P.H. 1993. Chemosphere 26(as cited in the HSDB): 2293-2299.
  14. 3M. 2001. Indirect Photolysis of Gaseous Perfluorooctane Sulfonyl Fluoride (POSF) by Fourier Transform Infrared (FTIR) Spectroscopy. U.S. EPA Administrative Record AR226-1030a104.
  15. Martin, JW., Mabury, SA., Solomon, KR and Muir, DC. 2003. Bioconcentration and tissue distribution of perfluorinated acids in rainbow trout (Oncorhynchus mykiss). Environ Toxicol Chem 22(1): 196-204.
  16. EPA), UEPAU. 2002. Update: National Listing of Fish and Wildlife Advisories. available online at: http://www.epa.gov/waterscience/fish/advisories/factsheet.pdf.
  17. US Environmental Protection Agency (US EPA) (2001). Analysis of PFOS, FOSA, and PFOA from various food matrices using HPLC electrospray/mass spectrometry, 3M study conducted by Centre Analytical Laboratories, Inc.

 



Notes relating to graph

Assumptions

  1. Assumed environmental halflife for C-10 fluorotelomer alcohol: 8.6 years. We find no studies that measure degradation of C-10 under normal environmental conditions. We estimated an environmental halflife for the C-10 fluorotelomer alcohol by scaling the environmental halflife for DDT (10.9 years, detailed in assumption #4) by the ratio of halflives of the alcohol and DDT in activated sewage sludge (where DDT degrades by 50 percent in seven hours, according to Johnson (1976), and where 95% of C-10 degrades in 24 hours (Pace 2002)).
  2. Increases in PFOA are calculated based on predicted breakdown rates of C-10 fluorotelomer alcohol, assuming that 12/13ths of the mass of the alcohol converts to PFOA, consistent with Pace (2002).
  3. Implicit in this figure is the assumption that the total moles of C-10 fluorotelomer alcohol and PFOA in the environment, at the time PFOA is banned, are equal.
  4. Assumed environmental halflife for DDT: 10.9 years, based on observed 81 percent decline in breast milk in Germany between 1969 and 1995 (Solomon and Weiss 2002).

References (graph)

  1. Johnson RE. 1976. Res Rev 61:1-28.
  2. Pace Analytical Services. 2002. Biodegradation Study Report: Biodegradation Screen Study for Biodegradation Screen Study for Telomer Type Alcohols. U.S. EPA Administrative Record AR226-1149.
  3. Solomon GM and PM Weiss. 2002. Chemical contaminants in breast milk: time trends and regional variability. Environmental Health Perspectives. 110(6), A339-447.