Chemical Identity of the proposed substance
In September 2005, the government of Sweden made a proposal for listing perfluorooctane sulfonate (PFOS) and 96 PFOS-related substances in Annex A of the Stockholm Convention on Persistent Organic Pollutants (POPs).
Chemical name: Perfluorooctane Sulfonate (PFOS)
PFOS, as an anion, does not have a specific CAS number The parent sulfonic acid and some of its commercially important salts are listed below:
Perfluorooctane sulfonic acid (CAS No 1763-23-1)
Figure 1 Structural formula of PFOS shown as its potassium salt
PFOS, a fully fluorinated anion, is frequently utilized as a salt or as part of larger polymers It belongs to the extensive group of perfluoroalkyl sulfonate substances, which includes PFOS-related compounds that may contain PFOS impurities or can produce PFOS The potassium salt of PFOS exhibits specific physical and chemical properties, detailed in Table 2.
Table 2 Physical and chemical properties of PFOS potassium salt
(Data from OECD, 2002, unless otherwise noted).
PFOS can be generated through environmental microbial degradation or metabolic processes in larger organisms from substances that contain the PFOS moiety While it is challenging to predict the specific contributions of individual PFOS-related substances to the overall environmental levels of PFOS, it is understood that any molecule featuring the PFOS moiety has the potential to act as a precursor to PFOS.
PFOS-related substances primarily consist of high molecular weight polymers, with PFOS being just a small component of these polymers and their final products (OECD, 2002) Definitions of PFOS-related substances vary across different contexts, leading to multiple lists that categorize these substances (Table 3) These lists differ in the number of substances included, all of which are believed to potentially degrade into PFOS The extent of overlap among these lists varies based on the specific substances being evaluated and the national inventories of existing chemicals.
Table 3 Number of PFOS-related substances as proposed by UK – DEFRA, US – EPA, OECD, OSPAR, and Canada
Source Number of PFOS-related substances
Appearance at normal temperature and pressure White powder
Water solubility in pure water 519 mg/L (20 ± 0,5ºC)
Henry’s Law Constant 3,09 x 10 -9 atm m 3 /mol pure water
OECD (2002) 172 (22 classes of perfluoroalkyl sulfonate substances)
A significant variety of substances can lead to the formation of PFOS, exacerbating contamination issues According to DEFRA, UK (2004), a list of 96 PFOS-related substances has been proposed, although their specific properties remain largely undetermined These substances may exhibit diverse environmental traits, including varying levels of solubility, stability, and absorption or metabolism capabilities Despite these differences, it is anticipated that all these substances will ultimately degrade into PFOS.
Environment Canada’s ecological risk assessment identifies PFOS precursors as substances containing the perfluorooctylsulfonyl (C8F17SO2, C8F17SO3) moiety, which can transform or degrade into PFOS While around 50 substances are listed as PFOS precursors, this list is not exhaustive, and other perfluorinated alkyl compounds may also qualify The assessment was based on industry surveys, expert judgment, and CATABOL modeling, which evaluated 256 perfluorinated alkyl compounds to determine the potential for non-fluorinated components to chemically or biochemically degrade into PFOS.
To prevent the omission of substances that could be precursors to PFOS, this document defines PFOS-related substances as all molecules with the molecular formula C8F17SO2Y, where Y can be OH, metal salt, halide, amide, or other derivatives, including polymers This definition has been put forth by the European Union.
Conclusion of the POP Review Committee of Annex D information
At its inaugural meeting in Geneva from November 7 to 11, 2005, the Persistent Organic Pollutants Review Committee (POPRC) assessed Annex D and determined that perfluorooctane sulfonate (PFOS) satisfies the screening criteria outlined in the annex, as documented in decision POPRC-1/7.
Data sources
This document on PFOS is primarily based on data collected by the United Kingdom, including the hazard assessment report created in collaboration with the USA for the OECD, as well as the UK's risk reduction strategy.
The OECD (2002) report focuses on the hazard assessment of Perfluorooctane Sulfonate (PFOS) and its salts, highlighting the importance of cooperation among member countries in evaluating existing chemicals This assessment was presented during a joint meeting of the Chemicals Committee and the Working Party on Chemicals, Pesticides, and Biotechnology, emphasizing the need for comprehensive environmental safety measures.
Economic Co-operation and Development, Paris, 21 November 2002.
Risk & Policy Analysts Limited (RPA & BRE, 2004), in collaboration with BRE Environment, conducted a comprehensive analysis titled "Perfluorooctane Sulfonate – Risk Reduction Strategy and Analysis of Advantages and Drawbacks." This final report was prepared for the Department for Environment, Food and Rural Affairs and the Environment Agency for England and Wales, outlining the risks associated with Perfluorooctane Sulfonate and proposing strategies for effective risk reduction.
This report incorporates recent findings from open scientific literature up to October 2005, along with data submitted by Parties and observers that contribute valuable new information.
Summary of available risk information
The OECD's 2002 hazard assessment of PFOS highlighted significant environmental and health concerns due to its persistence, toxicity, and potential for bioaccumulation.
An environmental risk assessment conducted by the UK Environment Agency highlights concerns regarding PFOS, as discussed among EU member states under the existing substances regulation (ESR DIR 793/93).
In October 2004, Environment Canada and Health Canada released a Draft Assessment of PFOS, its salts, and precursors for public comment The assessments of ecological and human health have been updated and will be available to the public shortly The ecological risk assessment indicates that PFOS is persistent, bioaccumulative, and inherently toxic.
Sweden has notified the European Commission about its proposed regulations to restrict the marketing and use of PFOS and its 96 known derivatives The new Swedish regulation aims to prohibit any products that contain PFOS or related substances, ensuring that these items are not available for sale or distribution to consumers for personal use, nor can they be sold or used commercially.
This prohibition shall not apply to hydraulic fluids intended for use in aircraft.
The UK has implemented a national regulation banning the import of firefighting foams containing perfluorooctane sulfonate (PFOS) and its degrading substances This regulation also prohibits the supply, storage, and use of PFOS across all applications, with specific time-limited exemptions for certain uses.
The UK and Sweden have proposed the following classification for PFOS in EU (2005):
R40 Carcinogen category 3; limited evidence of carcinogenic effect
R48/25 Toxic; danger of serious damage to health by prolonged exposure if swallowed
R61 May cause harm to the unborn child
R51/53 Toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment
The EU is now considering a proposal on the prohibition of PFOS and PFOS-related compounds in some products and chemical mixtures
Norway is contemplating a ban on fire-fighting foams that contain PFOS and related compounds, which currently represent the primary application of these substances in the country.
In 2002, the Environmental Protection Agency (EPA) established two Significant New Use Rules (SNURs) mandating companies to notify the agency prior to the manufacturing or importing of 88 PFOS-related substances In March 2006, the EPA proposed an additional SNUR to regulate another 183 perfluoroalkyl sulfonates (PFAS) with carbon chain lengths of five or more Additionally, the EPA suggested an amendment to the Polymer Exemption rule, aiming to eliminate the exemption for polymers containing specific perfluoroalkyl moieties with CF3 or longer chains, thereby requiring new chemical notifications for these polymers.
Status of the chemical under international conventions
OSPAR: PFOS was added to the list of Chemicals for Priority Action in June 2003.
Persistent Organic Pollutants Protocol to the Long-Range Transboundary Air Pollution Convention (“LRTAP”): Perfluorooctane sulfonate and its precursors were approved under Track A and are currently under Track B review.
2 SUMMARY INFORMATION RELEVANT FOR THE RISK PROFILE
Sources
Production, trade and stockpiles
The primary method for producing PFOS and its related substances is electro-chemical fluorination (ECF), a process predominantly employed by 3M, the leading global manufacturer of PFOS before the year 2000.
Direct fluorination, electro-chemical fluorination ( ECF:)
C8H17SO2Cl + 18 HF C8F17SO2F + HCl + by products
Perfluorooctanesulfonyl fluoride (PFOSF) is the key intermediate in the synthesis of PFOS and related substances, primarily produced through the ECF method, which yields a mixture of isomers and homologues, with 35-40% being the straight-chain 8-carbon variant Commercial PFOSF products typically consist of approximately 70% linear and 30% branched derivatives From 1985 to 2002, 3M's estimated global production of PFOSF reached 13,670 metric tons, peaking at 3,500 metric tons in 2000 PFOSF can react with methyl- or ethyl-amine to produce N-ethyl- and N-methyl perfluorooctane sulfamide, which can further react with ethylene carbonate to form N-ethyl- and N-methyl perfluorooctane sulfamidoethanol (N-EtFOSE and N-MeFOSE), key components of 3M’s product lines PFOS is generated through the chemical or enzymatic hydrolysis of PFOSF.
Other production methods for perfluoroalkylated substances are telemerisation and oligomerisation However, to which extent these methods are applied for production of PFOS and PFOS-related substances is not evident
On 16 May 2000, 3M announced that the company would phase-out the manufacture of PFOS and PFOS-related substances voluntarily from 2001 onwards The 3M global production of PFOS and PFOS-related substances in year 2000 was approximately 3,700 metric tonnes By the end of 2000 about 90 % of 3M’s production of these substances had stopped and in the beginning of 2003 the production ceased completely
3M's voluntary phase-out of PFOS production has resulted in a substantial reduction in the use of PFOS-related substances, significantly impacting the market despite other companies potentially increasing their production capacity As 3M previously held the largest production capacity for these substances globally, their withdrawal has prompted industry sectors to actively seek alternatives and reduce reliance on PFOS, further contributing to the decline in usage.
1 In the OECD report, 2002, perfluorooctanesulfonyl fluoride is abbreviated POSF.
The US Environmental Protection Agency (US EPA) has identified a list of non-US companies believed to supply PFOS-related substances globally, which includes six plants in Europe, six in Asia—four of which are located in Japan—and one in Latin America, excluding the 3M plant in Belgium It is important to note that this list may not be comprehensive or up-to-date.
A recent submission from Japan to the SC reveals that a single manufacturer in the country continues to produce PFOS, with an estimated output of 1-10 tonnes as of 2005 Additionally, Brazil's submission indicates the production of lithium salt of PFOS, although no quantitative data has been provided.
Perfluorinated substances, such as PFOS, are characterized by their long carbon chains, which render them both lipid-repellent and water-repellent These properties make PFOS-related compounds effective surface-active agents in various applications Their remarkable persistence, attributed to the strong carbon-fluorine bond, allows them to withstand high temperatures and harsh chemical environments, including strong acids and bases.
PFOS-related substances have been historically utilized in various applications across the US, with confirmed uses also observed in the UK and the EU Notably, while the US has seen all identified applications, the EU's involvement is specifically linked to the final two uses mentioned However, it is important to acknowledge that the EU has also employed these substances in fire-fighting foams, highlighting a broader historical context of PFOS-related applications.
Industrial and household cleaning products
In the UK study (RPA & BRE, 2004), detailed information has been received from the following sectors that currently use PFOS-related substances:
Use of existing fire fighting foam stock
The sectors presented above account for the UK However, deviation in the current use pattern between EU countries can not be excluded
PFOS and its precursors are not produced in Canada; instead, they are imported as chemicals or products for various Canadian applications These substances are often found in imported manufactured items and are primarily utilized as repellents against water, oil, soil, and grease in materials such as fabric, leather, paper, packaging, rugs, and carpets Additionally, PFOS serves as a surfactant in applications like firefighting foams and coating additives (Environment Canada, 2004).
PFOS and its precursors are not produced in the US but can be imported for specific regulated uses, including as anti-erosion additives in aviation hydraulic fluids and components in photoresist substances for semiconductor manufacturing They are also utilized in coatings for imaging films and as intermediates for producing other chemicals Historically, PFOS was used in firefighting foams, cleaning products, and coatings for textiles and paper Existing stocks of PFOS and related products could be used until depleted after the 2002 regulations, although PFOS-containing insecticides were subject to a phaseout agreement that banned their use after 2015.
The table below outlines the estimated current demand for PFOS-related substances in these applications in the EU (RPA & BRE, 2004).
Estimated Current (2004) Demand for PFOS Related Substances in the EU
Industry Sector Quantity (kg/year)
In the survey on production and use of PFOS and related substances performed by OECD in
In 2004, data related to PFOS was challenging to isolate from information regarding other substances, particularly PFAS To enhance clarity, it is advisable to define PFAS on page 4 and use the full term consistently throughout the article.
Water is essential for extinguishing most fires, but it is ineffective against flammable liquid fires (Class B) because it sinks below the burning fuel This can even cause the flammable liquid to spill To combat these types of fires, fire fighting foams were developed, proving to be crucial and effective tools These foams are created by mixing foam concentrate with water and aspirating it with air to produce a low-density foam blanket that effectively extinguishes flammable liquid fires.
The fire fighting foams can be grouped in two main categories:
Fluorine containing foam types (some of them consist of PFOS-related substances)
Since the announcement of the voluntary cessation of production of PFOS-related substances by 3M, the presence of PFOS in fire fighting foams has gradually decreased (RPA & BRE,
In Canada, the primary imports of perfluorooctane sulfonate (PFOS) have historically been in the form of potassium salt, primarily utilized in fire-fighting foams Furthermore, Canada recognizes that current inventories of PFOS-containing fire-fighting foams may pose a continuing substantial risk of environmental release.
A 2004 survey by the Fire Fighting Foam Coalition revealed that the US had an estimated 9.9 million gallons of aqueous film-forming foam, with around 45% of this inventory consisting of PFOS-based foams manufactured before 2003, while the remaining 55% included telomere-based foams.
Textile, Carpet and Leather Protection
PFOS-related substances have historically been utilized to enhance the resistance of textiles, apparel, home furnishings, carpets, and leather products against soil, oil, and water These substances modify surface properties, creating a protective barrier that repels contaminants by reducing the material's surface energy However, following 3M's market withdrawal, the use of PFOS-related substances in these applications has significantly declined (RPA & BRE, 2004).
Releases to the environment
or oceanic currents (Yamashita et al., 2005, Caliebe et al., 2004), transport in air (volatile PFOS-related substances), adsorption to particles (in water, sediment or air) and through living organisms (3M, 2003)
Estimating the environmental releases of PFOS is challenging due to its formation from the degradation of related substances, with the rate and extent of this process currently unknown A study conducted on Swedish sewage treatment plants revealed that effluents contained higher concentrations of PFOS than the incoming sewage, suggesting that PFOS may be generated from PFOS-related compounds.
Environmental fate
Persistence
PFOS is extremely persistent It does not hydrolyse, photolyse or biodegrade in any environmental condition tested (OECD 2002)
A study conducted following the US-EPA OPPTS protocol 835.2210 investigated the hydrolysis of PFOS in water at pH levels ranging from 1.5 to 11.0 and a temperature of 50°C Despite these conditions designed to promote hydrolysis, the study found no evidence of PFOS degradation Consequently, the half-life of PFOS was determined to be greater than 41 years.
A recent study following the US-EPA OPPTS protocol 835.5270 investigated the photolysis of PFOS in water, revealing no signs of direct or indirect photolysis under the tested conditions Additionally, the indirect photolytic half-life of PFOS at 25°C was determined to exceed 3.7 years.
Numerous studies have assessed the biodegradation of PFOS through various tests Aerobic biodegradation has been examined in activated sewage sludge, sediment cultures, and soil cultures, while anaerobic biodegradation has been investigated in sewage sludge However, none of these studies have shown any evidence of biodegradation occurring.
The only known condition whereby PFOS is degraded is through high temperature incineration under correct operating conditions (3M, 2003) Potential degradation at low temperature incineration is unknown.
Bioaccumulation
[Note: Additional and more current information should be provided on the bioconcentration and effects of PFOS in wildlife See the following:
Ankley, G.T., D.W Kuehl, M.D Kahl, K.M Jensen, B.C Butterworth and J.W Nichols 2004 Partial life- cycle toxicity and bioconcentration modeling of perfluorooctanesulfonate in the Northern leopard frog (Rana pipiens) Environ Toxicol Chem 23, 2745-2755.
A study by Ankley et al (2005) investigated the reproductive and developmental toxicity of perfluorooctanesulfonate (PFOS) in fathead minnows (Pimephales promelas) using a partial-life cycle test The research, published in Environmental Toxicology and Chemistry, highlighted the bioconcentration of PFOS and its potential impacts on aquatic life, emphasizing the need for further examination of PFOS's environmental effects.
In addition, there was recent review paper on the topic that the authors of the document could consult to further update this section of the report
Beach S.A., J.L Newsted, K Coady and J.P Giesy 2006 Ecotoxicological evaluation of
PFOS exhibits unique bioaccumulation characteristics that diverge from the typical behavior of persistent organic pollutants, as it does not accumulate in fatty tissues due to its hydrophobic and lipophobic properties Instead, PFOS preferentially binds to plasma proteins like albumin and β-lipoproteins, as well as liver proteins such as liver fatty acid binding protein (L-FABP) These distinctive physical-chemical traits suggest that the bioaccumulation mechanism of PFOS is fundamentally different from that of other persistent organic pollutants.
In a study following OECD protocol 305, the bioaccumulation of PFOS in bluegill sunfish (Lepomis macrochirus) has been tested The whole-fish kinetic bioconcentration factor (BCFK) was determined to be 2796 (OECD, 2002)
In another study on rainbow trout (Oncorhynchus mykiss), a bioconcentration factor (BCF) in liver and plasma was estimated to be 2900 and 3100, respectively (Martin, et al., 2003).
The BCF values for PFOS fall below the 5000 threshold set by the Stockholm Convention Annex D, suggesting that these criteria may not fully capture the substance's bioaccumulation potential Monitoring data from top predators, particularly Arctic polar bears, reveal significantly elevated PFOS levels, highlighting its substantial bioaccumulation and biomagnification properties Notably, PFOS concentrations in polar bear livers surpass those of all other known organohalogens By comparing PFOS levels in predators with those in their primary food sources, such as seals, hypothetical biomagnification factors can be calculated, although uncertainties exist due to species-specific differences in protein binding that may influence organ concentration without affecting overall body levels.
Table 4 Measured concentrations of PFOS in biota from various locations Calculated BMF is shown where applicable
Location Concentrations of PFOS Reference
- Concentrations of PFOS in liver (1700 –
> 4000 ng/g) exceeding all other individual organohalogens.
- BMF > 160 based on concentrations in Arctic seals.
- Very high concentrations of PFOS in liver (6.1 - 1400 ng/g)
- Very high concentrations of PFOS in liver (40 - 4870 ng/g).
- BMF = 22 based on data from fish in the same area.
- Another mink study also show very high concentrations of PFOS in liver (1280 -
- BMF ~145 to ~4000 based on data from their prey such as crayfish (whole body), carp (muscle) and turtles (liver
Bald Eagle, US - Very high concentrations of PFOS in plasma (1 – 2570 ng/g).
Dolphin, US - Very high concentrations of PFOS in liver (10 – 1520 ng/g) 3M, 2003.
- Very high concentrations of PFOS in liver (30 – 1100 ng/g).
- BMF > 60 based on data from salmon in the same area.
A study by Kannan et al (2005) found that the whole body bioconcentration factor (BCF) for round gobies (Neogobius melanostomus) is approximately 2400, aligning with laboratory findings The biota-toxicity transfer, represented by bioconcentration factors (BMFs), shows that PFOS concentrations in round gobies' whole bodies yield BMFs of about 10-20 when compared to salmon liver concentrations In bald eagles, a mean PFOS liver concentration of 400 ng/g ww results in a BMF of four to five when compared to higher trophic level fish Additionally, for mink, BMFs ranging from 145 to 4000 are calculated based on a mean liver concentration of 18,000 ng/g ww, relative to prey items like crayfish, carp, and turtles.
Research indicates that biomagnification of PFOS occurs, as animals at higher trophic levels exhibit greater concentrations of this chemical compared to those at lower levels A study calculated a trophic magnification factor (TMF) of 5.9 for PFOS within a pelagic food web, which included the invertebrate species Mysis, forage fish species such as rainbow smelt and alewife, and the top predator, lake trout Additionally, a diet-weighted bioaccumulation factor of approximately 3 was found for lake trout (Martin et al., 2004).
Research indicates significant bioaccumulation of PFOS in marine ecosystems, with Morikawa et al (2005) highlighting high levels in turtles Tomy et al (2004) found that PFOS biomagnified within an eastern Arctic marine food web, particularly affecting seabirds and marine mammals through elevated liver concentrations Additionally, Houde et al (2006) demonstrated similar biomagnification of PFOS in the food web of Atlantic ocean bottlenose dolphins.
A study by Bossi et al (2005) provides evidence of biomagnification occurring in marine ecosystems The research involved analyzing liver samples from fish, birds, and marine mammals in Greenland and the Faroe Islands, revealing PFOS as the most prevalent fluorochemical, followed by perfluorooctane sulfonamide (PFOSA) Notably, the findings from Greenland indicated a clear biomagnification of PFOS through the marine food chain, with levels increasing from shorthorn sculpin to ringed seals and ultimately to polar bears.
The binding of PFOS to proteins raises the question of the saturation levels of these binding sites Serum albumin is likely the primary binding pool for PFOS, as indicated by research (Jones et al., 2003) Studies, such as Ankley et al (2005), have examined PFOS bioconcentration in fish at water concentrations up to 1 mg/L, revealing a nearly linear relationship between PFOS levels in water and plasma at doses up to 0.3 mg/L, with no signs of saturation observed Notably, the 1 mg/L concentration was not tested due to mortality risks, highlighting that these levels exceed environmentally relevant concentrations.
A study by 3M (2003) found that the bioconcentration factor (BCF) for PFOS in whole fish reached approximately 2800 at a concentration of 86 àg/l, with steady-state levels achieved after 49 days of exposure The depuration process was slow, with an estimated 50% clearance time of 152 days for whole fish tissues Due to mortality, a BCF could not be determined at the higher concentration of 870 àg/l This suggests that saturation of serum protein binding sites is unlikely to limit PFOS bioconcentration in fish While similar data for mammals is lacking, the high bioaccumulation observed in mammals and the significant protein content in mammalian serum imply that saturation of binding sites may also not restrict PFOS bioaccumulation in these animals.
Long range environmental transport
The potassium salt of PFOS exhibits a low vapour pressure of 3.31 x 10^-4 Pa, indicating limited volatilization potential With an air-water partition coefficient of less than 2 x 10^-6, PFOS is primarily expected to be transported in the atmosphere attached to particles, rather than in a gaseous form, due to its surface-active characteristics.
Certain PFOS-related substances exhibit significantly higher vapor pressures than PFOS, making them more volatile and facilitating their transport through the air Notable examples include EtFOSE alcohol, MeFOSE alcohol, MeFOSA, EtFOSA, and FOSA, which can evaporate into the atmosphere Once airborne, these precursors can remain in gas form, condense onto atmospheric particles, or be removed by precipitation (3M, 2000) Research by Martin et al (2002) in Toronto and Long Point, Ontario, detected average concentrations of N-MeFOSE alcohol at 101 pg/m³ in Toronto and 35 pg/m³ in Long Point, while N-EtFOSE alcohol averaged 205 pg/m³ in Toronto.
PFOS has been found in rainwater from an urban area in Canada at a concentration of 0.59 ng/L The source of PFOS remains uncertain, as it could either come from precursors that are transported and degraded to PFOS through wet deposition or from atmospheric degradation followed by wet deposition This study did not measure potential precursors for PFOS (Loewen et al, 2005).
PFOS is estimated to have an atmospheric half-life exceeding two days, a conclusion drawn from its demonstrated resistance to degradation in various tests Notably, an atmospheric half-life of 114 days has been calculated for PFOS using an AOP computer modeling program (RER, 2004, Environment Agency).
The indirect photolytic half-life of PFOS at 25°C has been estimated to be more than 3.7 years (OECD, 2002)
PFOS has been detected in various biota across the Northern Hemisphere, including the Canadian Arctic, Sweden, the US, and the Netherlands A study by Martin et al (2004) found PFOS levels in liver samples from Arctic species, indicating widespread contamination The presence of PFOS in these remote ecosystems, far from human activity, highlights its potential for long-range transport Although the exact mechanisms of this transport remain unclear, it may involve the movement of volatile PFOS-related compounds that ultimately degrade into PFOS.
A recent study on rainbow trout liver microsomes has revealed that N-ethyl perfluorooctanesulfonamide (N-EtPFOSA) acts as a precursor to PFOS in fish (Tomy et al., 2004a) This research, alongside findings of N-EtPFOSA concentrations reaching 92.8 ± 41.9 ng/g wet weight in Arctic aquatic organisms (Tomy et al., 2004b), supports the theory that perfluorinated sulfonamides are volatile precursors of PFOS that can be transported over long distances to the Arctic However, the notion that these precursors arrive at Arctic latitudes via atmospheric transport remains unverified by direct atmospheric measurements (Bossi et al., 2005).
Exposure
Bioavailability
Research indicates that perfluorooctane sulfonate (PFOS) exhibits significant bioconcentration in fish species, with bluegill sunfish and rainbow trout showing bioconcentration factors (BCFs) of 2796 for whole fish, 2900 for liver, and 3100 for plasma The primary method of PFOS uptake in these fish is through their gills (Martin et al., 2003).
PFOS is primarily released into the environment via wastewater from sewage treatment plants (STPs), making fish a significant pathway for PFOS to enter food chains Research indicates that PFOS has a high oral absorption rate of 95% within 24 hours in the gastrointestinal tract, as demonstrated in studies conducted on rats.
2002) Taken together, this could constitute the basis of the highly elevated levels that have been observed in top predators in food chains containing fish
Two human monitoring studies conducted on the Swedish population revealed that females with a high fish consumption had elevated levels of PFOS in whole blood, measuring 27.2 ng/g (range 3.0 – 67, n = 10), compared to the general female population, which had an average level of 17.8 ng/g (range 4.6 – 33, n = 26).
In a study conducted by the OECD in 2002, it was found that workers at 3M's perfluorochemical manufacturing plant in Decatur, US, exhibited the highest concentrations of PFOS The serum levels measured in these workers during the last recorded year, 2000, ranged from 0.06 to 10.06 µg/g.
A comprehensive study conducted across 12 European countries analyzed blood samples from families spanning three generations, revealing widespread contamination with chemicals such as PFOS and perfluorooctane sulfonamide (FOSA) PFOS was detected in 37 out of 38 samples, with concentrations ranging from 0.36 to 35.3 ng/g of blood, while FOSA was found in 36 samples, with levels between 0.15 and 2.04 ng/g (WWF, 2005).
Hazard assessment for endpoints of concern
Toxicity
Research indicates that PFOS toxicity has been demonstrated through various studies involving acute, sub-chronic, and chronic exposures in rats, as well as sub-chronic exposures in monkeys and a two-generation study on rats Additional findings from reproductive and teratogenicity studies conducted on rats and rabbits further contribute to the understanding of PFOS's harmful effects For comprehensive details, refer to the OECD assessment conducted in 2002.
A 90-day study on rhesus monkeys exposed to PFOS potassium salt via gavage at the doses
In a study assessing the toxicity of PFOS, doses of 0, 0.5, 1.5, and 4.5 mg/kg bw/day were administered to monkeys At the highest dose of 4.5 mg/kg bw/day, all four monkeys either died or were euthanized due to severe health deterioration No fatalities occurred at the lower doses of 0.5 or 1.5 mg/kg bw/day; however, gastrointestinal toxicity was observed The absence of a No Observed Adverse Effect Level (NOAEL) indicates that the lowest dose tested is a Lowest Observed Adverse Effect Level (LOAEL) Consequently, these findings confirm that PFOS meets the EU criteria for classification as Toxic, associated with the risk phrase R48.
A 90-day oral repeated dose toxicity study in rats that were fed diets containing 0, 30, 100,
In a study on the effects of PFOS potassium salt, it was found that all rats died when fed diets containing 300 mg/kg or higher, which corresponds to a dosage of 18 mg/kg body weight per day Additionally, at a lower concentration of 100 mg/kg (equivalent to 6 mg/kg body weight per day), 50% of the rats (5 out of 10) succumbed These findings highlight the significant toxicity of PFOS potassium salt at elevated dietary levels.
In a study involving PFOS at a dosage of 30 mg/kg (equivalent to 2.0 mg/kg/day), subjects survived until the conclusion; however, minor alterations in body and organ weights were observed Due to the lowest tested dose being classified as a Lowest Observed Adverse Effect Level (LOAEL), a No Observed Adverse Effect Level (NOAEL) could not be determined Additionally, the findings support the classification of PFOS as having chronic toxicity in rats, aligning with the R 48 designation under EU criteria.
A two-generation reproductive toxicity study on rats administered PFOS potassium salt via gavage revealed significant findings regarding pup viability At doses of 1.6 mg/kg bw/day and 3.2 mg/kg bw/day, a notable reduction in the survival of the F1 generation was observed, with 34% of pups in the 1.6 mg/kg group dying within four days of birth, and 45% of pups in the 3.2 mg/kg group dying within one day of delivery, with no survivors beyond day four These results are corroborated by a study conducted by Luebker et al (2005).
Maternal toxicity was observed at doses of 1.6 and 3.2 mg/kg bw/day, leading to decreased food intake, body weight gain, and overall terminal body weight, with localized alopecia noted at the higher dose The lowest observed adverse effect level (LOAEL) identified in this study was 0.4 mg/kg bw/day, linked to significant reductions in pup weight gain in the F1 generation The no observed adverse effect level (NOAEL) was determined to be 0.1 mg/kg bw/day.
A study by Grasty et al (2003) found that exposure to PFOS during the later stages of gestation can lead to complete mortality in pups, suggesting that the underlying cause may be the disruption of lung maturation.
Rat Maternal PFOS Doses and Tissue Levels
Dose mg/kg/d Serum ug/ml Liver ug/g Study
Maternal weight and thyroid hormone reductions; BMD05
Delayed eye opening 0.4 Luebker et al 2005a
Reduced maternal body weight and food consumption; reduced pup body weight
Pup weight and maternal thyroid hormone decreases
Decreased gestation and pup survival; BMD05
Decreased gestation 0.8 42.6 Luebker et al 2005b
Maternal and neonatal thyroid hormone decreases 1 19.6 † 85* Thibodeaux et al 2003
Lau et al 2003 Neonatal mortality;
Luebker et al 2005a Reduced maternal weight gain
LD50 neonatal mortality 3 71.9 † 288* Lau et al 2003
† Numerically from Lau et al (2004) to match Thibodeaux et al (2003) Figure 3
*Liver concentrations estimated from Thibodeaux et al (2003) Figure 3, and provided courtesy of Dr
Ecotoxicity
Environmental toxicity data for PFOS is predominantly found for aquatic organisms such as fish, invertebrates and algae
PFOS exhibits moderate acute toxicity to fish, with a lowest observed LC50 (96h) of 4.7 mg/l identified in studies involving Fathead minnow (Pimephales promelas) exposed to the lithium salt of PFOS Additionally, the lowest no observed effect concentration (NOEC) recorded is 0.3 mg/l.
Pimephales promelas at prolonged exposure (42d) and was based on mortality (OECD,
PFOS is classified under EU regulations as R 51 due to its toxicity to fish, indicating it is "toxic to aquatic organisms," and R 53, which highlights its potential to "may cause long-term adverse effects in the aquatic environment."
The Mysid shrimp (Mysidopsis bahia) exhibits the lowest LC50 (96h) value for aquatic invertebrates at 3.6 mg/l, while its lowest NOEC value is recorded at 0.25 mg/l, according to OECD (2002).
A study by Macdonald et al (2004) reported a 10 day NOEC of 0.0491 mg/L for the growth and survival of the aquatic midge (Chironomous tentans)
The most sensitive algae appear to be the green algae Pseudokirchnerilla subcapitata with a
IC50 (96h, cell density) of 48.2 mg/L The lowest NOEC value for algae was determined in the same study for Pseudokirchnerilla subcapitata, 5.3 mg/L (Boudreau et al., 2003)
In a 21-week study, mallard and bobwhite quail were fed diets containing PFOS, with a focus on various endpoints such as adult body and organ weights, feed consumption rates, fertility, hatchability, and offspring survival The lowest observed effect concentration (LOEC) identified was 10 ppm (10 mg/kg diet).
Exposure to PFOS in mallards (Anas platyrhynchos) has been linked to significant reproductive impacts, including reduced testes size, impaired spermatogenesis, and decreased hatchling survivability At the observed dosage, PFOS concentrations measured 87.3 µg/mL in serum and 60.9 µg/g in liver tissue.
The study conducted by the US EPA (OPPT AR 226-1735) reveals uncertainty due to the absence of a No Observed Adverse Effect Level (NOAEL) In adult quail (Colinus virginianus) fed a diet containing 10 ppm (10 mg/kg), minor signs of toxicity were noted, including increased liver weight in females and a higher incidence of small testes size in males Additionally, there was a reduction in survivability of quail chicks relative to the percentage of eggs set Serum concentrations in adult female quail reached 84 µg/mL, with liver concentrations at 8.7 µg/mL and 4.9 µg/kg wet weight, while adult male quail showed serum levels of 141 µg/mL and liver concentrations of 88.5 µg/kg.
Perfluorooctanesulfonic acid (PFOS) has raised concerns regarding its potential long-range environmental transport and the significant adverse effects it may have on human health and ecosystems Evidence suggests that PFOS can persist in the environment and bioaccumulate in living organisms, leading to detrimental impacts Comparative studies indicate that the risks associated with PFOS exposure, including developmental and reproductive toxicity, warrant global action to mitigate its effects Therefore, addressing PFOS contamination is crucial for protecting both human health and the environment.
Perfluorooctane sulfonate (PFOS) poses a significant risk as it meets the Annex D screening criteria, with levels increasing linearly in the absence of production controls, as evidenced by monitoring data from remote locations This substance is accumulating in human tissues and the environment, raising concerns due to troubling toxicological studies that indicate effects at tissue doses relevant to human exposure levels, which are currently under review PFOS, a fully fluorinated anion, is widely used in various applications, including firefighting foams and products designed to repel oil, water, grease, or soil Additionally, PFOS can be formed through the degradation of a group of related substances known as PFOS-related substances.
PFOS is recognized for its potential for long-range transport, as demonstrated by monitoring data indicating significantly high levels in various regions of the northern hemisphere, particularly in Arctic biota, which are distant from human activities Additionally, PFOS meets the specific criteria for atmospheric half-life, further supporting its persistence in the environment.
PFOS is recognized for its toxicity, exhibiting harmful effects on mammals even at low concentrations in sub-chronic repeated dose studies It has been linked to reproductive toxicity in rats, resulting in pup mortality shortly after birth due to impaired lung maturation Additionally, PFOS poses a significant threat to aquatic life, with mysid shrimp identified as the most sensitive organisms affected.
PFOS is highly persistent in the environment, demonstrating no degradation under hydrolysis, photolysis, or biodegradation across various tested conditions The sole method identified for degrading PFOS is high-temperature incineration.
PFOS exhibits significant bioaccumulation potential, as evidenced by the elevated concentrations detected in top predators like polar bears, seals, bald eagles, and minks These predators have high biomagnification factors (BMFs) based on the PFOS concentrations in their prey While fish show relatively high bioconcentration factor (BCF) values, they do not meet the specific numeric criteria necessary for assessment The unique properties of PFOS, which preferentially binds to proteins in non-lipid tissues, suggest that traditional numeric criteria for BCF or bioaccumulation factor (BAF) may not be suitable for this substance Alarmingly, high levels of PFOS have also been identified in Arctic wildlife, indicating the widespread impact of this contaminant, even in remote areas far from human activity.
Table 8 POP characteristics of PFOS.
Atmospheric half life > 2 days (estimated value based on photolytic half life > 3.7 years)
Sub-chronic exposure: Mortality in monkeys at 4.5 mg/kg bw/day. Reproductive toxicity: mortality in rat pups at 1.6 mg/kg bw/day
Acute toxicity to Mysid shrimp (Mysidopsis bahia): LC 50 (96h) = 3.6 mg/L
Acute toxicity to fish, Fathead minnow (Pimephales promelas): LC 50 = 4.7 mg/L
Persistence Yes Extremely persistent No degradation recorded in chemical or biological tests
Found in highly elevated concentrations in top predators Calculated hypothetical BMFs = 22 - 160
PFOS and its related substances have been utilized across various applications due to their unique properties Historically, these chemicals were employed in eight different sectors; however, current usage in industrialized nations appears to be restricted to five sectors It remains unclear if this trend reflects global usage patterns.
PFOS and related substances are released into the environment during their manufacturing processes, through their use in various industrial and consumer applications, and from the disposal of products containing these chemicals after they have been utilized.
The formation rate and extent of PFOS from its related chemicals remain largely unclear, making it challenging to assess the overall contribution of each PFOS-related substance to environmental PFOS levels Given its remarkable stability, it is anticipated that PFOS will ultimately be the final degradation product of all substances related to PFOS.