Perspectives on the Inclusion of Perfluorooctane Sulfonate into the

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Environ. Sci. Technol. 2009, 43, 5171–5175

Perspectives on the Inclusion of Perfluorooctane Sulfonate into the Stockholm Convention on Persistent Organic Pollutants1 THANH WANG YAWEI WANG CHUNYANG LIAO YAQI CAI GUIBIN JIANG* State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing

SHUTTERSTOCK

Reflections on the inclusion of perfluorooctane sulfonate into the Stockholm Convention on Persistent Organic Pollutants.

Persistent organic pollutants (POPs) have been of considerable public health and environmental concern for several decades. These are organic substances that persist in the environment, can undergo long distance transportation, are able to bioaccumulate, and pose a risk of causing adverse effects to animals and human health. As a measure to control and mitigate the threats of POPs, an international treaty was signed in 2001 and came into force on May 2004 for its signatories (1). The treaty, called the Stockholm Convention on Persistent Organic Pollutants (SC), initially listed twelve chemicals, the so-called “Dirty Dozen” for final elimination (Annex A), or restricted use (Annex B), and/or reduced releases of unintentional production (Annex C). The SC also included a section stating that additional chemicals can be nominated by its member parties, after which the candidate chemical would undergo several screening and evaluation rounds before it could be voted for inclusion into the Convention (Figure 1). The (possible) inclusion of one of these suspected POPs, perfluorooctane sulfonate (PFOS), is currently a controversial issue and we provide some of our viewpoints below, mainly concerning the current production pattern, adverse health effects, and economical issues. Review documents were mainly cited due to limitations on article length, and interested readers are advised to consult relevant articles cited within these reviews.

Environmental Concerns of PFOS

1 Editor’s Note: This manuscript was accepted for publication on April 24, 2009. On May 9, 2009, the Conference of the Parties 4 of the Stockholm Convention (COP-4) in Geneva placed perfluorooctane sulfonate and perfluorooctane sulfonyl fluoride (PFOS and PFOSF) in Annex B (see below for other included substances). Due to our production timelines, it was impossible to have this article appear prior to the COP-4 meeting (began May 4, 2009). Therefore the conditional/future tensing within this article, now made moot by the COP-4 decision, has been edited into parentheses. Much of this paper describes the toxicological considerations of PFOS/PFOSF that led to its inclusion. Taking the information in this Viewpoint article, readers may wish to consider the placement of PFOS/PFOSF as argued by the authors. According to the press release of the (COP-4) May 9, 2009 resolution (http://chm.pops.int/Convention/Pressrelease/ COP4Geneva9May2009/tabid/542/language/en-US/Default.aspx), the compounds listed in this paper were assigned as follows: PFOS, its salts, and PFOSF - Annex B, pentabromodiphenyl ether - Annex A, hexabromobiphenyl - Annex A, chlordecone - Annex A, pentachlorobenzene - Annex A and Annex C, lindane - Annex A, R- and β-hexachlorocyclohexane - Annex A.

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Perfluorinated compounds (PFCs) exhibit unique properties such as high surface activity, thermal and acid resistance, are both hydro- and lipophobic, and have therefore been found very useful in a wide range of applications: in industry as polymers, surfactants, lubricants, and pesticides; and in consumer products as textile coatings, nonstick coatings, stain repellent, food packaging, firefighting foams, and more (2). Unfortunately, the very properties that make these chemicals valuable also render some PFCs extremely resistant to environmental and biological breakdown. These chemicals were long assumed to be inert and thus safe, but it was found in recent years that PFCs can be released during certain industrial applications and during the lifetime of commercial products containing them (3). Among these, the eight carbon chained PFOS (Figure 2) and perfluorooctanoic acid (PFOA) were found to be environmentally persistent and globally prevalent even in remote areas such as the Arctic and have been detected in wildlife and humans, typically with PFOS at higher concentrations than PFOA (4). Therefore, these two compounds have lately drawn considerable scientific and public interest. Consequently, regulators have also begun to take action, and in the advent of increasing environmental and health concerns, Sweden proposed in 2005 to list PFOS and 96 so-called precursors, which contain the PFOS moiety (C8F17SO3-) and are suspected to be degradable to PFOS, in the SC for ultimate elimination. Once released into the environment, PFOS behaves very differently from what is usually expected for a POP. These differences include intrinsic properties such as the surface activity, water solubility, nonmeasurable octanol/water VOL. 43, NO. 14, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 1. General overview of the processes for adding new POPs into the Stockholm Convention on POPs and the interactions between the convention secretariat, the persistent organic pollutants review committee (POPRC), and the parties of the convention. Adapted from (44). Time frame from nomination to final submission of proposal to the Conference of Parties for decision is estimated to be minimum three and a half years. coefficient (Kow) values, and relatively low bioaccumulation potential (2). Despite these differences, the Stockholm Convention POPs Review Committee (POPRC) considered PFOS to meet the criteria of a POP after assessing its environmental properties during the initial screening stage (Annex D, (5)), the risk profile (Annex E, (6)), and risk management evaluation (Annex F, (7)), whereby the committee recommended that perfluorooctane sulfonic acid (PFOSH), its salts and the main production intermediate, perfluorooctane sulfonyl fluoride (PFOSF), be listed in the SC. The choice of PFOSH was mainly due to the lack of designated CAS number for the PFOS anion, and it was thought that inclusion of PFOSF would incorporate most of the precursors as PFOSF is used as starting chemical for synthesizing PFOS chemicals. The inclusion of PFOS will be up for vote at the fourth meeting of the Conference of Parties in May 2009 (see link in Editor’s Note above).

Production Consideration Production volume and use profiles are important assessment criteria for a suspected POP; high production volume of a persistent industrial chemical that can be readily released into the environment will ultimately lead to widespread global distribution at high concentrations, while low production volume is likely to have a lesser global impact. The actual production of PFOS chemicals is still unclear due to an absence of proper registration of current PFOS stockpiles and production in many countries. There is also confusion as to whether some of the reported amounts relate to PFOS alone, to PFOSF, or to combined PFOS-related substances. A standardization of terminology for reporting PFOS and related substances is therefore warranted. The commercial production of PFOS chemicals began over half a century ago, and total production (mainly as PFOSF) from 1970 to 2002 was estimated to be ∼100,000 t (3). By 2003, PFOS chemicals were no longer manufactured by 3M, the main U.S. producer. However, due to important uses in specialized industrial processes without suitable replacementss semiconductors, medical devices, aviation, metal plating, pest control, and photographic processessproduction of PFOS is still ongoing in other countries, though to a much smaller extent than previous to 2003 (7). Interestingly, as legislation has become stricter for PFOS products in developed countries, there has been a production shift to other countries with less robust environmental regulations. For 5172

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FIGURE 2. Chemical structure of relevant PFCs: (a) potassium salt of perfluorooctane sulfonate (PFOS); (b) perfluorooctylsulfonyl fluoride (POSF); (c) N-ethyl perfluorooctanesulfonamide (sulfuramid); (d) perfluorobutane sulfonate (PFBuS), (e) perfluorooctanoic acid (PFOA). example, companies in China fittingly began large scale production in 2003 at the advent of 3M’s phase out, having an annual production in 2004 of 200 t in 2006, of which 100 t was designated for export (8). Stricter regulations within countries with historical production or use of PFOS and PFOA (which is also facing a similar phase out process) cause companies to take precautionary steps in assessing cost benefit against potential public risks. These kinds of regulatory environment and precautious reasoning have, largely, still not reached developing or transition countries as the majority are still adopting the “grow first, clean up later” principle for the sake of domestic economic growth. The economic losses following a ban on PFOS would probably be large to affected industries, not to mention the extensive investment and timeconsuming efforts that might be needed for current producers and downstream users to develop and implement substitutions. However, an economic argument is likely to be viewed as unacceptable by many regulatory bodies of developed countries due to the environmental concerns of PFOS. Many of those principal companies with phased out PFOS or PFOA production have more or less already developed and started commercializing alternative chemicals and are also employing new PFC emission reduction technologies in their factories (9). One of the problems to tackle with an (eventual) inclusion of PFOS in the SC, is(/would be) how to formulate

appropriate support on capacity building to those affected developing countries in transition to suitable alternatives, and how willing the leading PFC industries are to share their knowledge.

Toxicity and Human Risk Assessment PFOS is well absorbed orally with relatively slow elimination. It mainly distributes in the blood serum and the liver and binds to proteins rather than to fatty lipids unlike other POPs (4). Ecotoxicological studies have shown that PFOS exhibits low to moderate acute toxicity to aquatic life forms (2). Some of the observed adverse end points on laboratory animals following PFOS exposure include decreased body weight, enlarged liver, hepatotoxicity, decreased serum cholesterol levels, teratogenicity, neurotoxicity, induced peroxisome proliferation, and endocrine disruption, but no direct genotoxicity was found (4, 10). Recent findings suggest that environmentally relevant levels can also affect immune functions in animals (11). Furthermore, PFOS might also interact with other molecules in chemical mixtures. For example, although PFOS is mostly found in extracellular spaces, its amphiphilic properties might facilitate the cell membrane permeability of other pollutants and thereby indirectly induce adverse effects caused by these chemicals (12, 13). Although toxicological research on PFOS has been expanded in recent years, the potential toxic end points from chronic exposure at environmentally relevant levels and modes of action are still insufficiently explored. Translating results from animal studies on PFOS to human health risk is an intricate task, further complicated by discrepancies in results obtained among different laboratory animals (4). Evidently harmful effects from laboratory studies often occur at levels that largely exceed environmentally relevant concentrations, except for accidental industrial or occupational spills that might cause locally high levels. Worldwide patterns for human blood serum suggest higher levels in developed countries and those with past and present PFOS industries (4). Serum PFOS levels have been found to decline in recent years for the general U.S. population (currently at lower parts-per-billion levels), suggesting that the phase-out of PFOS chemicals by 3M has been effective (14, 15). So far, there has been no clear evidence that occupational exposures of PFOS lead to adverse health effects despite relatively high individual serum levels of 3M workers reaching parts-per-million concentrations (13, 16-19). A confounding animal study that received notable attention concerned the developmental effects of PFOS: the reproductive functions of parental rats were largely unaffected at the highest exposure group (receiving a daily dose of 3.2 mg/kg body weight), but all first generation offspring died within 2 d of birth, and about one-third of offspring died within 4 d of birth at half the dose (20). However, clinical and epidemiological studies on the general human population have so far given inconclusive results. While some studies found correlation between PFOS levels and natal factors such as birth weight, others did not find corresponding associations (16). A recently published pilot study found that the decrease in sperm quality for a small cohort of young men was correlated with higher serum levels of PFOS and PFOA, but the results would have to be further confirmed by studying a larger cohort (21). Human elimination half-life has been estimated to be approximately 5 yr, which is much slower than the 100 d for laboratory rats and 100-200 d for cynomolgus monkeys, further pointing out the difficulties in extrapolating results from animal studies to humans (4, 22). Model estimations, based on published data, indicate that human exposure of PFOS mainly derives from food consumption and ingestion/inhalation of dust containing PFOS released from treated or contaminated products (23). Preliminary

assessments estimated the human exposure doses to be in the range 3.9-520 ng/(kg · d) for different age and gender groups in a generalized western population, although the intermediate doses were ∼15-33 ng/(kg · d) (24). However, limited available data and large uncertainty in the calculations involving sources, environmental fate, degradation mechanisms, pharmacokinetics, and exposure patterns of the general population and different subgroups (especially children) (25), makes it premature to properly assess the risks, and hinders the installment of proper governmental regulations. Based on available research, we view that the current information on toxicity and adverse health effects in humans is largely incomplete and too inconclusive to warrant an immediate global action against PFOS. However, the current health concern was deemed by the POPRC to be sufficient to justify listing of PFOS, partly in reference to the precautionary approach as stated in principle 15 in the Rio Declaration: “[w]here there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation” (26). The inclusion of the precautionary principle in an operational manner is one of the most significant aspects of the SC and provides a relatively solid foundation for the POPRC when assessing nominated substances (27). One of the disagreements within the scientific community and among the stakeholders is to what extent PFOS can cause threats of serious or irreversible damage.

Regulatory Frameworks and Guidelines The EPA has included PFOS into its significant new use rule (SNUR, (28)) to regulate its usage. The EU has already imposed severe restrictions and banned the marketing and use (with certain exemptions) of products that exceed 0.005-0.1% PFOS by mass under its directives (29). Canada has included PFOS in their “virtual elimination” list (30). These regulations will probably have minor impact on the market within countries with discontinued production and phased out usage of PFOS chemicals, but would impact regions with recently developed production and downstream usage, such as the textile industry in China (31). There are currently no existing national regulations concerning PFOS in drinking water or foodstuffs, although a few agencies have issued guidelines on recommended maximum allowable levels. The Minnesota Department of Health issued a health risk limit value of 0.3 µg PFOS/L in drinking water (32), whereas in Germany, the Drinking Water Commission of the Ministry of Health deduced a tentative Tolerable Daily Intake (TDI) of 100 ng/kg body weight (25). The European Food Safety Authority (EFSA) proposed a TDI of 150 ng/kg body weight, and it is noted that the current exposure of PFOS to the general population is well below the TDIs and not likely to promote adverse effects (25, 33).

Further Perspectives The negotiations leading to the original framework of the SC were lively, with debates concerning the adoption of the precautionary principle, financial mechanisms, and future addition of suspected POPs into the Convention, all of which culminated in compromising resolutions between opposing views (27, 34). During COP-4, PFOS was(/will be) reviewed together with a handful of other suspected POPs: commercial mixtures of penta- and octabrominated diphenyl ethers (PBDEs), hexabromobiphenyl, chlordecone, pentachlorobenzene, lindane, and alpha- and beta-hexachlorocyclohexane (see Editor’s Note at beginning). These chemicals will be the first batch to be considered for inclusion since the original “Dirty Dozen”, and will be a test of the process of adding new POPs to the SC. The practice of the precautionary principle during the screening processes is not unique to VOL. 43, NO. 14, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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PFOS; the POPRC considered that lack of conclusive information on the long-range transportation properties of chlordecone, a pesticide, should not prevent its inclusion. However, a distinction is that all known production of chlordecone has been ceased for several years (35). Although it is apparent that global large-scale production of PFOS products is no longer a feasible option, many of the current replacements are just shorter chained PFCs (9). Substitutes, such as perfluorobutane sulfonate (PFBuS), are considered less bioaccumulative (36, 37) and preliminarily found to be less adverse than PFOS, but research regarding their potential toxicity is still limited (38, 39), and the mode of (bio)action might be different from that of PFOS. Paradoxically, PFOS-based firefighting foams were one of the alternative replacements to halon-based fire extinguishers that were phased out following the Montreal Protocol on Substances that Deplete the Ozone Layer. Sulfuramid, which can degrade to PFOS, is used as an alternative to chlordane and mirex (both listed in the SC) for ant and termite control, especially in severely affected countries such as China and Brazil (40, 41). The lack of sufficient resources to enact environmental laws and regulations in these countries already represents a major obstacle, and these recurring bans might intimidate domestic industry stakeholders to hesitate before investing or acquiring licenses for new replacements or alternative technologies. It is also perceived that some parties without a current economic stake seem to readily approve inclusion, whereas other parties with production uses may be more cautious about restrictive measures (42). (Although it is currently unclear) how PFOS is(/would be) listed in the SC, (whether) in Annex (A or) B, several options have been discussed and explored (43). (Upon assessing the inclusion of PFOS into [Annex B of] the SC), we advise the parties to take into account the current relatively low production amount and high importance of PFOS in certain specialized industrial applications, where no suitable replacements are available in the foreseeable future. We further recommend that the parties of the SC actively communicate in finding a coherent solution. The fundamental principle of the Stockholm Convention is to protect the environment and human health, but the final fate of PFOS is also likely to be the subject of political and economical debates (40). Thanh Wang is a Ph.D. candidate at the State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, part of the Chinese Academy of Sciences. Yawei Wang is an associate professor in the same laboratory and works on the environmental fate and bioaccumulation of emerging organic chemicals such as PBDEs and PFOS. Chunyang Liao is currently an associate professor at the Yantai Institute of Coastal Zone Research for Sustainable Development, Chinese Academy of Sciences. His research focuses on the in vivo and in vitro ecotoxicological effects of environmental pollutants such as PFOS. Yaqi Cai is a professor at the State Key Laboratory of Environmental Chemistry and Ecotoxicology, and his field of research includes analytical method development and environmental monitoring of emerging pollutants. Professor Guibin Jiang is the Director of the State Key Laboratory of Environmental Chemistry and Ecotoxicology. His broad research areas include analytical methodology and the environmental fate and toxicological effects of persistent organic chemicals, organometallic compounds, and nanomaterials. Address correspondence about this article to [email protected].

Acknowledgments All authors declare they have no potential competing financial interest. The views expressed in this paper are those of the authors and do not necessarily reflect the views or policies of any stakeholders or funding agencies.

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