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Survey and environmental/health assessment of fluorinated substances in impregnated consumer products and impregnating agents 12 General discussion, conclusions and recommendations
12.1 Discussion, conclusions and recommendations concerning the chemical familyDuring the past years an awareness has arisen on a new type of persistent organic pollutants, which contains an alkyl chain typically between 4 and 12 carbon atoms, where all or most of the hydrogen atoms have been replaced by fluorine. This makes the chain very stable and practically non-degradable in the environment. The substances also contain a more reactive functional group, which may be an alcohol, a carboxylic acid, a sulfonic acid, a phosphoric acid or their derivatives. Today more than thousand polyfluorinated substances are known. These substances are surface active substances with an extreme low surface tension, and they repel water, grease and dirt, and are therefore used as surfactants or impregnating agents in numerous industrial products and consumer products under trade names such as Scotchgard®, Baygard®, Gore-Tex®, Zonyl® and Stainmaster®. Until the start of this century, the most used polyfluorinated compounds were PFOS (perfluorooctane sulfonate) and PFOS-related compounds. When it became clear that these persistent chemicals were global pollutants, and high levels were found in polar bears from remote arctic areas, the production and use of these compounds stopped, and a formal ban has recently been introduced in the European Union. Today PFOS has been substituted in products by either perfluorinated substances with a shorter chain length (C6 or shorter) or other classes of more complex polyfluorinated substances such as fluorotelomer alcohols (FTOH) and their derivatives. These more complex compounds may be precursors of and be degraded to the ultimate perfluorinated acids. The fluorocarbon tail is, however, rather stable. 12.2 Discussion, conclusions and recommendations concerning the use surveyThe purpose of this project has been to estimate the use of polyfluorinated compounds (PFCs) in impregnation and consumer products in Denmark, and to perform an update of the environmental and health assessment of polyfluorinated substances and their degradation products carried out previously for the Danish EPA (Poulsen et al. 2005). In order to estimate the use of fluorinated compounds used in consumer products in Denmark, the following approach has been used. Initially, a search was carried out in the Danish Product Register in order to determine the registered use of these substances in Denmark. Secondly, several companies in Denmark as well as foreign producers/suppliers of these fluorinated substances were contacted in order to obtain information for developing an estimate of the consumption of fluorinated chemicals in consumer products in Denmark. Searches on the Internet were used as an extra source of information, and information found about the level of fluorinated substances in products was combined with Danish statistical information in order to estimate an amount of fluorinated substances in consumer products within specific use areas in Denmark. Results of the survey The search in the Danish Product Register showed a total use of fluorinated substances of 16.5 tonnes. As a basis for the search OECDs Preliminary lists of PFOS, PFAS, PFOA and related compounds and chemicals that may degrade to PFCA (OECD, 2006) were used. In total 92 fluorinated substances were identified in the Danish Product Register, of which 48 substances were registered with a use of 0.00 tonnes (meaning either a very low consumption or that a use amount had not been registered, as it should have been done). The most important use areas (according to the reported totals) are releasing agents, paint and lacquers, glue, surface active substances and galvano-technical products, which accounts for about 15 of the 16.5 tonnes in total. Releasing agents are compounds used e.g. in moulds in order to get the moulded plastic product for example to release easily from the mould. However, releasing agents can also be used on e.g. frying pans to ensure a non-stick surface. The use in areas polish and care products, impregnating agents, cleaning agents and surface active substances (non-metal, e.g. for paper and cardboard) accounts for about 0.5 tonnes (of the last 1.5 tonnes). These uses are most likely much greater, as only chemical products labelled as dangerous have to be registered in the Danish Product Register. The Danish Product Register does not register all products containing fluorinated compounds on the Danish market, and the registered amounts do not give an adequate picture of the total sales in Denmark. In addition, imported finished products, such as raincoats containing fluorinated compounds, are not registered in the Product Register. As a supplement to the search in the Danish Product Register information was obtained from Danish Statistics on the content of fluorinated substances in different consumer products. The estimated total consumption of fluorinated substances in consumer products in Denmark is shown in Table 12.1. Table 12.1: Total estimated amount of fluorinated substances used or contained in products in Denmark
One thing is the use of fluorinated substances, another thing is, however, the type of fluorinated substances used, and the possibility of the substances to be degraded to PFOS, PFOA or other PFCAs in the environment, as these substances are the most critical in the environment. According to documentation from DuPont impurities of PFOA in products containing fluorinated substances are typically between 0.1 and 1% of the total content of fluorinated substances. Besides this potential content of PFOA as impurities, products may contain precursor compounds, such as fluorotelomer alcohols, being able to degrade to PFCAs. It must be noted that about 7.5 tonnes of the total 16.5 tonnes registered in the Danish Product Register count for substances that have a chain length lower than 8, and there are furthermore substances that are not on the OECD list of PFAS, PFOS, PFOA and other substances that can be degraded to PFCA. The rest of the chemicals may, however, have a potential to degrade to PFOA or other PFCAs in the environment. The exact amount is not known, as this would require detailed knowledge of the fluorinated substances used, as only specific types of fluorinated substances can be degraded to PFOS, PFOA or other PFCAs in the environment. Conclusions and recommendations to survey During this project several companies in Denmark as well as foreign producers and suppliers of fluorinated substances have been contacted in order to obtain information about the consumption of fluorinated substances in Denmark. This approach was, however, unsuccessful because either the companies had no knowledge about these fluorinated chemicals or they simply did not want to participate with information to the project. It is, therefore, difficult or impossible to obtain a more precise estimate of the consumption of these substances in Denmark than by using the information in the Danish Product Register. This is however, also problematic, as the data in the Danish Product Register is not complete. First of all, the Product Register data only covers chemical products (and only classified chemical products) and not consumer products/articles. Secondly, the information in the Product Register does not seem to be completely up to date – a lot of uses are registered with a consumption of 0.00 tonnes, indicating information is lacking. The complexity of the area is further demonstrated by the fact that the chemicals are not only found in chemical products (more easy to track and measure), but also as content or impurity in consumer products/articles. It is almost impossible to track e.g., which impregnating agents that have been used to produce all-weather clothes in China, and to find out, which amounts are sold in Denmark. The last resort has been to use Danish Statistics to estimate the consumption of fluorinated chemicals in consumer products in Denmark. These estimates have a high uncertainty as the statistics on supply on certain consumer products in Denmark, not necessarily is very precise – the product groups are too large for the purpose of this project. Furthermore, these statistical data have been multiplied with a concentration (range) of fluorinated substances in the products, in order to estimate a total amount used in consumer products in Denmark. This concentration range has been based on information from published chemical analysis of products and on information found on impregnating chemicals and use amounts on the Internet. In order to learn more about the content and concentration of fluorinated substances in consumer products in Denmark, more chemical analysis have to be carried out in order to learn more about the substances used and the range of concentrations that can be found. This survey has shown that chemical analysis have been carried out mainly for impregnating agents for e.g. footwear and all-weather clothes. In all other consumer product areas the information about the content of fluorinated substances is limited: carpets, footwear, sunshades etc., paints, printing inks, auto polish and waxes, floor polish and cleaning agents. According to the estimations carried out in this project, carpets seem to be the largest use areas. A use could not be estimated for sunshades, awnings, parasols etc., but this area also seems to be of relevance for further investigation. It is therefore suggested that these products are in focus if chemical analysis of the content of fluorinated substances are carried out. 12.3 Discussion, conclusions and recommendations concerning the environmental impactsEnvironmental fate and levels Concentrations of PFCs have been extensively reported for all environmental compartments all over the world. Most studies have been performed in the North American continent, Europe and Japan. The number of compounds analyzed has been extended to a large series of perfluorinated carboxylates with carbon number from 7 to 16. Besides PFOS, the list of sulfonates has been extended to compounds with 7, 9 or 10 carbon atoms. The attention has also been focused on the precursor and intermediates of the more persistent PFOS and PFCAs. Biodegradation studies of precursor compounds such as fluorotelomer alcohols (FTOHs) and perfluorosulfonamides demonstrated that these compounds are degraded to the more persistent PFOS and PFCAs. Several studies performed with the volatile precursor compounds in smog chambers have found that FTOHs and sulfonamides react in the atmosphere with OH radicals to yield the acidic compounds. The reaction time is long enough (about 20 days) for these compounds to be transported to remote regions, where deposition and further bioaccumulation in the food chain occurs. The “precursor” theory for explaining the presence of PFCs in remote regions (e.g. the Arctic) has been supported by atmospheric measurements of FTOHs and perfluorosulfonamides in both industrial and remote regions. Atmospheric concentrations were higher close to sources, but these compounds were also detected in the Arctic atmosphere. Oceanic transport of ionic PFCs has also been proposed as alternative or supplemental transport path to remote regions, with the compounds directly dissolved in water or present as a film on the surface foam. Another theory hypothesizes direct transport of PFOS and PFCAs directly from the sources directly bound on atmospheric particulate phase. Indoor measurements of PFCs concentrations have been performed in both gaseous and particulate phase. Indoor concentrations resulted up to 100 times higher than outdoor concentrations and carpets were identified as one of the major sources of PFCs on the basis of measurements of household vacuum cleaner dust; no actual analysis of carpets have been carried out. Improvements in analytical detection limits have made possible measurements of PFCs levels at ppt levels in environmental waters, included rainwater and oceanic waters, where PFCs have been detected at very low concentrations. Several studies have been published on concentrations and fate of PFCs in wastewater treatment plants (WWTPs), as these systems have been identified as important sources for PFCs to the aquatic and terrestrial environments. Precursors of PFOS and PFCAs have also been analyzed. These compounds have been found in wastewater together with PFOS and PFCAs. PFCs were also found in sludge from WWTPs. PFOS and PFCAs were found more or less not degradable in WWTPs. PFCs concentrations in wildlife have been reported for a wide range of animals at all latitudes, including the Arctic and the Antarctic. PFCs and especially PFOS have been more or less found in all samples with concentrations varying from sub-ng/g levels to several µg/g, with birds living close to a fluorochemical plant as the worst case. The bioaccumulation potential of PFCs has been confirmed by several bioaccumulation studies in different food webs. Temporal trends studies have been performed on archived biologic materials, in general covering time spans from the 1970s-1980s to the present. The PFCs concentrations, especially those of PFOS, have been found to gradually increase up to the present years. Only in a study from the Canadian Arctic it has been observed a decrease in PFOS concentration after 2000, which was explained as a rapid response after the stop of PFOS production in USA. Ecotoxicity PNEC (Predicted No Effect Levels) values of 0.0167 and 0.067 mg/kg food have been reported for secondary poisoning in the food chain for the aquatic environment for PFOS. The comparison of PNEC values with measured environmental PFOS concentrations raised concern about secondary poisoning in the aquatic environment. The toxicity of PFOS and PFOA has been tested for different aquatic organisms (algae, invertebrates and fish). Generally, PFOA and PFOS are not found to be toxic at the normal environmental concentrations in water. However, different effects have been observed for specific cellular functions such as mechanisms involving the uptake of xenobiotics. Other biological endpoints affected by PFOA and PFOS are survival, growth, and emergence. The degradation products of FTOH (saturated and unsaturated fluorotelomer acids) have been found to be more toxic than their end products (PFCAs) by a factor of 10,000. 12.4 Discussion, conclusions and recommendations concerning the human health impactsHuman levels Perfluorinated chemicals (PFC) have in contrary to most other persistent organic pollutants (POP) a low affinity to lipids in adipose tissues but bind to proteins in cell membranes and accumulate in various body tissues of exposed organisms, including in liver, kidneys, testes and brain. The accumulation in fats and muscles is minimal. In the blood perfluorinated chemicals are mainly bound to serum proteins, especially albumin. The mean half-lives in human blood were 5.4 years for PFOS, 8.5 years for PFHxS, and 3.8 years for PFOA in retired fluorochemical workers but the whole body half-life may be even longer, since the elimination of these chemicals from the human body is insignificant. Further, the half life for the lower steady state concentrations in the general population is probably much longer. Blood levels of perfluorinated chemicals have been monitored in many countries but most data has been developed in USA. In all countries, besides Korea, PFOS has been determined in far higher concentrations than the other PFCs. Typical average serum levels of PFOS in industrialized countries are 20-30 ng/mL with maximum levels less than 100 ng/mL. The second most abundant PFC is normally PFOA with typical average serum levels of 3-5 ng/mL. Some of the highest PFC blood levels (2-3 times the typical levels) in the general population were determined in industrial areas of USA and China. Such levels may be 10 times higher than in rural and remote area. Recently data from Denmark was published. The average PFOS level in blood serum was 35 ng PFOS/mL with a maximum concentration of 107 ng/mL. That is somewhat higher concentration than in our neighbour countries. It may at least partly be explained by that the Danish samples are old (1996-2002); thus there is a need for further studies. Some studies have analysed blood plasma or whole blood instead of serum. Analysis of plasma will give the same results as serum but whole blood levels will be 2-3 times lower than serum levels. Levels of PFCs in cord blood are about the half of levels in maternal blood thus some transfer to placenta occurs. Levels of PFCs in human semen are ten times lower than in blood serum and levels in human milk are 100 times lower than in blood, so these fluids are not suitable for biological monitoring of PFCs. Toxicokinetics In animal experiments the studied PFCs are readily absorbed in the gastro-intestinal tract and some compounds penetrate the intact skin. The peak blood levels are seen 1-2 hours after exposure and the substances clear rapidly from the blood. PFOA and PFOS are both considered being metabolically inert, and other perfluoroalkyl acids with shorter or longer alkyl chain do have similar properties. Their precursors and functional derivatives will ultimately be transformed to their basic acids. For example, the fluorotelomer alcohol 8:2 FTOH is rapidly transformed to PFOA, PFNA and other metabolites in mice and rats. In the same way EtFOSE is metabolised to FOSE, FOSA and finally to PFOS. Once absorbed in the body PFOA is eliminated as the free carboxylic acid mainly with urine and to a less extent in faeces. Thus the renal elimination is critical for detoxification, and the lamination decreases with increasing chain length among the perfluorocarboxylic acids (PFCAs). The biological half-life of PFOA in male rats is 70 times longer than that in female rats for which it was only 2 hrs. The sex-related clearance of PFOA differs between animal species. In hamsters it is opposite rats. In mice and rabbits there are no sex difference; and mice had a slow excretion as male rats; and rabbits had a fast excretion as female rats. In dogs the plasma half-life of PFOA was about 20 days in males and the half in females. In monkeys the biological half-life is several months. As mentioned above the excretion of PFCs in humans are insignificant, thus animals may not be a good model. Toxicology Although the perfluoroalkyl sulfonic acids and carboxylic acids are closely related structurally, these chemicals elicit different biological responses in vitro and in vivo. The acute lethal toxicity is moderate corresponding to a classification as harmful. PFOS is more toxic than PFOA, and the toxicity of perfluorinated chemicals increases generally with the length of the alkyl chain. PFCAs with a branched alkyl chain seem to be less toxic than linear isomers. The liver is the primary target organ for perfluorinated compounds. PFOS and PFCAs cause peroxisome proliferation in the rodent liver as well as induction of various enzymes involved in lipid metabolism. PFDA with a longer alkyl chain seems even accumulative and more active than PFOA. Toxic effects have been reported, such as induction of fatty liver and uncoupling of the mitochondrial respiratory chain. Subchronic exposure of animals to PFOS may lead to significant weight loss accompanied by hepatotoxicity and reduction of serum cholesterol and thyroid hormones. The lowest NOAEL for PFOA found was 0.06 mg/kg bw/d for increased liver weight in rats in a 13-week study. The lowest NOAEL for PFOS found was 0.03 mg/kg bw/d for decreased T3 levels in a 26-week monkey study. Inhibits cellular communication PFOS, PFOSA, PFHxS and perfluorinated carboxylic acids with carbon chain length of 7-10 can rapidly and reversibly inhibit gap junction intercellular communication in a dose-dependent manner, and with PFDA inhibiting more than PFOA. Gap junction intercellular communication (GJIC) is the major pathway of intracellular signal transduction, and it is thus important for normal cell growth and function. Defects in this communication may lead to teratogenesis, neuropathy, infertility, diabetes, autoimmune disorders, cancer, and other diseases. Endocrine disruptors Both PFOA and PFOS affect the serum levels of various hormones, i.e. reducing testosterone, and increasing estradiol in rats. Thus these substances may act as endocrine disruptors. Cancer Although the fluorinated chemicals do not seem to be mutagenic, PFOA induces testis tumors and PFOS and EtFOSE induce liver cancer in experimental animals. USEPA classifies PFOA as a carcinogen in animals. The experience from the work environment has not indicated any important adverse health effects among exposed workers, besides a retrospective cohort mortality study of a perfluorooctane sulfonyl fluoride (PFOSF) production workforce, which reported an excess of bladder cancer at high-exposure jobs. Developmental toxicity PFOS causes developmental effects including reduction of foetal weight, cleft palate, oedema, delayed ossification of bones, and cardiac abnormalities. However, the structural abnormalities were found in the highest PFOS dose groups, where significant reductions of weight gain and food consumption were also observed in the pregnant dams. Thus the relevance may be questioned. PFOA causes reduction of foetal weight. Other PFAS (PFBS and PFHxS) have neither a significant effect on reproduction or development even at high doses. Risk assessment The U.K. Committee on Toxicity (2006) has recommended a provisionally TDI for PFOA and PFOS of 3 mg/kg bw/d and 0.3 mg/kg bw/d, respectively, using an uncertainty factor of 100. They conclude that for some small children the TDI may already be exceeded. This assessment was based on results from animal experiments, which may be very arbitrary and unreliable, because the renal clearances of PFOA and PFOS are insignificant in humans, contrary to a large active excretion in experimental animals (Harada et al. 2005). This means that these chemicals in humans leave the blood by redistribution to internal organs and not by elimination from the body. This increases the internal exposure time in critical organs considerable Conclusions and recommendations to human toxicology The main exposures to perfluorinated substances seem to be by direct product exposure, through food intake or by inhalation/ingestion of indoor dusts but it is not sufficient explained. Perfluorinated chemicals are readily absorbed in the organism and concentrate in the blood and internal organs associated with proteins. The half-lives in the blood are several years in humans compared to hours or days in experimental animals, in which the renal clearance is fast contrary to in humans, where it is insignificant. The levels of perfluorinated chemicals in human blood differ between countries and areas. The levels are higher in industrial area than in rural areas. PFOS is still the most abundant followed by PFOA but here seems to be a time trend downwards for these chemicals and upward trend for PFNA. The blood levels of PFOS in Denmark are in the upper end of the global average, and new studies are warranted. The toxicology of PFOS and PFOA are rather well-studied in animals but the available information about the health-related properties of other polyfluorinated substances is limited. The great difference in residence time in the body between humans and animals makes it questionable using the animal data for risk assessment as it is presently done. The recent independent studies showing that exposure to perfluorinated chemicals at the present levels may affect pregnancy and decrease birth weight in humans is worrying but presently, we have insufficient information for evaluation of the full health impact of the present exposure levels in humans.
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