|Approaches for better information and monitoring of POPs in articles|
|Monitoring of POPs in articles and products|
|Alternative assessment approaches for chemical alternatives|
|Screening of potential POPs in chemical databases|
|Tools for the assessment of POPs properties of chemicals|
|Toxicity assessment of alternatives|
|Case study: Scientific assessment of a PFOS alternatives in chromium plating|
The Stockholm Convention Regional Centre for Capacity-building and the Transfer of Technology in Asia and the Pacific at Tsinghua University (Beijing/China) has conducted an assessment of an alternative substance for PFOS used in chromium plating in China
The electroplating industry in China is well developed, with an estimated >15,000 factories, >500,000 employees, >5,000 production lines and a production capacity of >300 million m2. A recent survey by a China market research centre revealed the total industrial output value to be almost 13,000 million USD in 2008. During the electroplating process, especially in ‘hard chrome plating’, mist suppressants are indispensable for the protection of employees from exposure to the airborne, highly toxic form of chromium (Cr(VI)). The most commonly used mist suppressants are based on perfluorooctane sulfonate acid and its salts (PFOS, C8F17SO3-). For example, the United Nations Industrial Development Organization (UNIDO) estimated that up to 10,000 kg/yr of PFOS-containing mist suppressants were being used for this purpose in Europe in 2004. Similarly, among the three major mist suppressants used in the Chinese market (Table 23), two of them are PFOS salts. According to the Chinese Electroplating Association, the estimated annual consumption of PFOS in China for electroplating was 30-40 t in 2007, which appears to be stable in recent years.
Perfluoroalkyl ether potassium sulfonate (F-53, C8F17O4SK) was first developed as a mist suppressant for the hard chrome plating industry, by the Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences in 1975.
After successful demonstrations in four local electroplating plants in Shanghai, F-53 was found to be excellent in performance but high in synthesis cost. F-53B is the modified version of F-53, with the replacement of one fluorine atom by chlorine (Table 24). This modification was made to simplify the production process (see Figure S1) and reduce the cost where chlorination is used in the last step, and prevent the use of toxic and expensive chemicals (e.g. SbCl5 and SbF3). Therefore the commercialized product was F-53B instead of F-53. For several years, this compound had remained as the only available mist suppressant in the Chinese electroplating industry, until the emergence of PFOS related substances FC-80 (C8F17O3SK) in 1982, and FC-248 (C16H20F17O3NS) later (see Table 24).
Table 24. Main mist suppressants on the Chinese market
As the main PFOS manufacturing country, there has been growing pressure on China to reduce production, which appears to have peaked in 2006. Therefore, F-53B as a PFOS alternative may be expected to obtain a larger market share and potentially expand from being solely used by the metal plating industry to other industries which currently use PFOS.
There is ample evidence that PFOS is environmentally persistent, bioaccumulative, and toxic to human and animals. The similarity in chemical structures between F-53B and PFOS makes it reasonable to assume that these chemicals possess similar physicochemical properties and environmental behaviour. However, data were lacking, with no information available on the environmental presence and potential impact of F-53B. Therefore in a research study conducted at the Stockholm and Basel Convention Coordination Center at Tsinghua University (Beijing/China), F-53B was firstly evaluated for its persistence, bioaccumulation and toxicity (PBT) to give further recommendation on substitution.
B) Biodegradation test
Laboratory tests of “ready biodegradability” have been used as conservative surrogates for the assessment of biodegradation in actual or simulated environmental matrices, which can indicate the propensity for a chemical to be degraded in the aquatic environment. Amid of them, the Closed Bottle Test (CBT, OECD 301D) is recommended as a first, simple test for the assessment of the biodegradability of organic compounds in the environment. The degradation process of the test substance is tracked by analysis of the demand of oxygen in a mineral medium inoculated with micro-organisms from a mixed population. In the testing, F-53B was added to make a final concentration of 3 mg/L. The demand of oxygen was measured in two vessels at 0, 7, 14, 21 and 28 d, and the results were used to calculate the biological oxygen demand (BOD) according to OECD Guideline 301D.
F-53B was classified as not readily degradable in the CBT, which implies that it is probably not biodegraded efficiently in wastewater treatment plants. Considering the stringency of the OECD 301 test pass criteria, this result does not necessarily demonstrate that F-53B is not degradable in the environment.
C) Advanced oxidation process (AOP) stability test
In addition, the stability of F-53B under various advanced oxidation process (AOP) conditions was tested as described in detail by Schröder and Meesters (2005). Briefly, the original analyte concentration was 45 mg/L, made in ultrapure water, with a reaction vessel volume of 250 mL, in all cases. Tests proceeded for 120 min, with samples taken every 20 min, in which F-53B was determined using the analytical method described below, after dilution. The following tests were carried out.
(i) UV photodegradation: F-53B water solution was added into the reactor chamber and irradiated with a high pressure mercury lamp (220V, 300W) in the XPA-2 photochemical reactor (Nanjing Xujiang Electromechanic Plant, Nanjing, China).
(ii) UV/H2O2 oxidation: 4.0 mL of 30% H2O2 was added into the reaction system of (i).
(iii) O3 oxidation: the dosage of O3 was 3.0 g/h; and the pH of solution was 11, using the reaction system of (i).
(iv) O3/H2O2 oxidation: 4.0 mL of 30% H2O2 was added into the reaction system of (iii).
(v) Fenton oxidation: 250 mg/L FeSO4, 30% H2O2, pH=3.
Under all AOP test conditions (i)-(v), the degradation of F-53B was very low. For test conditions (i) and (v), no concentration change could be found. After 2 hr reaction, the degradation of F-53B was observed as less than 5% under test condition (ii), about 10% under test condition (iii), and 25% under test condition (iv). These results clearly demonstrated that F-53B is very refractory even under the rigorous AOP conditions.
D) Estimation of bioaccumulation
It is difficult to predict the bioconcentration factor (BCF) or bioaccumulation factor (BAF) of PFOS and F-53B as their non-standard partitioning behaviour prevents meaningful Log Kow values being derived.
Due to the similarity in chemical structure it may be assumed that F-53B will bioaccumulate in the same order as PFOS and potentially more because of its larger size due to the replacement of one fluorine atom with chlorine. To test this assumption and in the absence of empirical data for F-53B, physicochemical properties were derived using EPI Suite 4.11. The results are shown in Table 24. Accepting the uncertainty associated with these estimations, then F-53B had a log Kow value of 5.24 compared to 4.49 for PFOS, and also had an associated higher BAF (3.81 and 3.28, respectively).
Table 25. Estimated BAF, BCF and physicochemical properties of F-53B and PFOS
a The water solubility of F-53B (potassium salt) was higher than 200 mg/L in pure water at a room temperature of 25 oC. The water solubility of potassium salt of PFOS was measured at 570~910 mg/L -.
b Both the BAF and BCF values were estimated for the fish in the upper trophic level based on Arnos-Gobas (2003) model.
E) Acute toxicity test
Toxicity tests were carried out at the Key Laboratory of Ecological Effect and Risk Assessment of Chemicals, the Chinese Research Academy of Environmental Sciences, in Beijing. Fish acute toxicity was tested according to Organisation for Economic Cooperation and Development (OECD) Guideline using zebrafish (Brachydanio rerio) as the test species.
The LC50 (96 h) of F-53B for Brachydanio rerio was just over 15 mg/L. This is less than 100 mg/L, but larger than 10 mg/L, which means that F-53B should be classified as a Category III chemical in terms of acute toxicity (harmful to aquatic life), according to the Globally Harmonised System (GHS) criteria for classification of chemicals. The same test was carried out for PFOS along with F-53B. F-53B seems to be similar to PFOS in terms of acute fish toxicity, belonging to the same toxicity class as PFOS according to the GHS definition. The acute toxcity for F-53B is close to the 10 mg/L EC50 limit for Class II “moderate toxicity”. The LC50 value is similar to the LC50 (96 h) values of PFOS acute toxicity for zebrafish (Danio rerio) from literature studies with 22.2 mg/L. and 71 mg/L
F-53B, a China-specific chrome mist suppressant widely used for over 30 years, is very similar to PFOS in respect to the PBT profiles. Therefore its appropriateness as a PFOS alternative is questionable and need further assessment.
 Wang S, Huang J, Yang Y, Hui Y, Ge Y, Larssen T, Yu G, Deng S, Wang B, Harman C (2013) First Report of a Chinese PFOS Alternative Overlooked for 30 Years: Its Toxicity, Persistence, and Presence in the Environment. Environmental Science & Technology 47, 10163–10170
 Dong, X.; Li, C.; Li, J.; Wang, J.; Huang, W., A game-theoretic analysis of implementation of cleaner production policies in the Chinese electroplating industry. Resources, Conservation and Recycling (in Chinese)2010, 54 (12), 1442-1448.
 Carloni, D., Perfluorooctane Sulfonate (PFOS) production and use: past and current evidence. United Nations Industrial Development Organization (UNIDO), Vienna, Austria, 2009, http://www.unido.org/fileadmin/user_media/Services/Environmental_Management/
 Lin, A.; Li, X., Reduction and alternative of POPs in electroplating industry. Technology & New Process (in Chinese) 2008, 12 (12), 10-13.
 Zhang, L.; Liu, J. G.; Hu, J. X.; Liu, C.; Guo, W. G.; Wang, Q.; Wang, H., The inventory of sources, environmental releases and risk assessment for perfluorooctane sulfonate in China. Environ. Pollut.2012, 165, 193-198.
 Shanghai Guangming Electroplating Plant; Shanghai Institute of Organic Chemistry at Chinese Academy of Sciences; Jiangsu Taizhou Electrochemical Plant, Preparation of F-53 and its application in chrome mist suppression. Material Protection (in Chinese) 1976, 3 (3), 27-32.
 Zhu, C., FC-80 Chrome Mist Suppressant. Plating & Finishing (in Chinese) 1985, 2 (2), 28-30.
 Wang S, Huang J, Yang Y, Hui Y, Ge Y, Larssen T, Yu G, Deng S, Wang B, Harman C (2013) First Report of a Chinese PFOS Alternative Overlooked for 30 Years: Its Toxicity, Persistence, and Presence in the Environment. Environmental Science & Technology 47, 10163–10170.
Organisation for Economic Cooperation and Development (OECD),(301D) Guideline for Testing of Chemicals (closed bottle test), 1992b, http://www.oecd-ilibrary.org/test-no-301-ready-biodegradability_5lmqcr2k7qmw.pdf?contentType
 Schröder, H. F.; Meesters, R. J., Stability of fluorinated surfactants in advanced oxidation processes—A follow up of degradation products using flow injection–mass spectrometry, liquid chromatography–mass spectrometry and liquid chromatography–multiple stage mass spectrometry. J. Chromatogr. A. 2005, 1082 (1), 110-119.
 Liu, C.; Gin, K. Y. H.; Chang, V. W. C.; Goh, B. P. L.; Reinhard, M., Novel Perspectives on the Bioaccumulation of PFCs – the Concentration Dependency. Environ. Sci. Technol. 2011, 45 (22), 9758-9764.
 Brooke, D.; Footitt, A.; Nwaogu, T.; Britain, G., Environmental risk evaluation report: Perfluorooctanesulphonate (PFOS). Environment Agency UK: 2004.
Inoue, Y.; Hashizume, N.; Yakata, N.; Murakami, H.; Suzuki, Y.; Kikushima, E.; Otsuka, M., Unique Physicochemical Properties of Perfluorinated Compounds and Their Bioconcentration in Common Carp Cyprinus carpio L. Arch. Environ. Contam. Toxicol. 2012, 62 (4), 672-680.
 United Nations, Globally Harmonized System of Classification and Labelling of Chemicals (GHS), ST/SG/AC.10/30/Rev.4, 4th revised edition, 2011,http://www.unece.org/fileadmin/DAM/trans/danger/publi/ghs/ghs_rev04/English/ST-SG-
 Sharpe, R. L.; Benskin, J. P.; Laarman, A. H.; MacLeod, S. L.; Martin, J. W.; Wong, C. S.; Goss, G. G., Perfluorooctane sulfonate toxicity, isomer-specific accumulation, and maternal transfer in zebrafish (Danio rerio) and rainbow trout (Oncorhynchus mykiss). Environ. Toxicol. Chem. 2010, 29 (9), 1957-1966.
 Ye, L.; Wu, L.; Jiang, Y.; Zhang, C.; Chen, L., Toxicological study of PFOS/PFOA to zebrafish (Danio rerio) embryos. Chinese Journal of Environmental Science (in Chinese) 2009, 30 (6), 1727-173.