Stockholm Convention on Persistent Organic Pollutants s3

UNITED NATIONS SC

UNEP/POPS/POPRC.7/3 Distr.: General 18 May 2011

Stockholm Convention Original: English on Persistent Organic Pollutants

Persistent Organic Pollutants Review Committee Seventh meeting Geneva, 10–14 October 2011 Item 6 (b) of the provisional agenda* Consideration of chemicals newly proposed for inclusion in Annexes A, B and/or C to the Convention: hexachlorobutadiene

Proposal to list hexachlorobutadiene in Annexes A, B and/or C to the Stockholm Convention on Persistent Organic Pollutants**

Note by the Secretariat

1. The annex to the present note sets out a proposal submitted by the European Union and its member States that are parties to the Stockholm Convention on Persistent Organic Pollutants to list hexachlorobutadiene in Annexes A, B and/or C to the Convention pursuant to paragraph 1 of Article 8 of the Convention. The proposal is being circulated as submitted and has not been formally edited. A detailed dossier prepared in support of the proposal is set out in document UNEP/POPS/POPRC.7/INF/4 and the Secretariat’s verification of whether the proposal contains the information specified in Annex D is discussed in document UNEP/POPS/POPRC.7/INF/8.

Possible action by the Committee 2. The Committee may wish: (a) To consider the information provided in the present note and in document UNEP/POPS/POPRC.7/INF/4; (b) To decide whether it is satisfied that the proposal fulfils the requirements of Article 8 of and Annex D to the Convention; (c) To develop and agree on, if it decides that the proposal fulfils the requirements referred to in paragraph 2 (b) above, a workplan for preparing a draft risk profile pursuant to paragraph 6 of Article 8.

*UNEP/POPS/POPRC.7/1. ** Stockholm Convention on Persistent Organic Pollutants, Article 8, paragraph 1.

K1171782 210611 UNEP/POPS/POPRC.7/3 Annex

Proposal to list hexachlorobutadiene in Annexes A, B and/or C to the Stockholm Convention on Persistent Organic Pollutants Introduction

Hexachlorobutadiene (HCBD) is a halogenated aliphatic compound, mainly created as a by-product in the manufacture of chlorinated hydrocarbons like tri- and tetrachloroethene and tetrachloromethane. HCBD was – and maybe still is in some countries – used as a fumigant. Some other minor uses of HCBD are reported. This dossier focuses solely on the information required under paragraphs 1 and 2 of Annex D of the Stockholm Convention and it is mainly based on the following document: - Hexachlorobutadiene, Dossier prepared in support of a proposal of Hexachlorobutadiene to be considered as a candidate for inclusion in the Annex I to the Protocol to the 1979 Convention on Long-Range Transboundary Air Pollution on Persistent Organic Pollutants (LRTAP Protocol on POPs)1. This extensive review report also serves as a source of further information referred to in paragraph 3 of Annex D of the Stockholm Convention on this candidate POP chemical.

1. Identification of the chemical The identity and chemical structure of HCBD is shown below:

CAS number: 87-68-3 EINECS number: 201-765-5 EINECS name: hexachlorobuta-1,3-diene Synonyms: Perchlorobutadien, 1,1,2,3,4,4-hexachlor-1,3- butadiene, 1,3-hexachlorobutadiene; Dolen-Pur; GP- 40-66:120

Chemical Formula: C4Cl6

2 Persistence Bosma et al. (1994)2 observed removal of HCBD under anaerobic conditions after an acclimation time of 4 months. The main reaction product was 1,2,3,4-tetrachloro-1,3-butadiene (>90%). This substance – which is known as an antifungal agent according to the authors - may be degraded further aerobically. No half lives are presented. Under aerobic circumstances in the same test system, no degradation was observed. Van Agteren et al. (1998)3 concludes that HCBD is a recalcitrant substance under aerobic conditions while under anaerobic conditions reductive dechlorination has been observed. Tabak et al. (1981)4 found that HCBD - using a static-flask screening method and concentrations of 5 and 10 mg/L with a test period of 7 days had disappeared partly after the first 7 days incubation period. However, when the study was continued with subcultures (in fact a study on adaptation potential) HCBD was increasingly recalcitrant. This suggests that the observation during the first week was an artefact and it implies that HCBD is recalcitrant to degradation under these aerobic conditions. In James (2009)5, the following explanation is given why chlorinated hydrocarbons are more resistant to aerobic degradation: “Due to the oxidised state conferred by the highly electronegative halogen

1http://www.unece.org/env/lrtap/TaskForce/popsxg/2000-2003/hcbd.pdf 2 Bosma, T.N.P. et al. (1994). Comparison of reductive dechlorination of hexachloro-1,3-butadiene in Rhine sediment and model systems with hydroxocobalamin. Environ. Sci. Technol. 28, 1124-28. 3 Van Agteren, M., S. Keuning and D.B. Jansen (1998). Handbook on biodegradation and biological treatment of hazardous organic compounds. Kluwer Academic Publishers. 4 Tabak, H.H., S.A. Quave, C.I. Mashni, E. Barth (1981). Biodegradability studies with organic priority pollutant compounds. Journal WPCF, 53, (10), 1503-1518.

2 UNEP/POPS/POPRC.7/3 substituents, the carbon backbone of chlorinated hydrocarbons cannot be attacked by oxygen (Wohlfahrt and Diekert, 1997)” Environment and Health Canada (2000)6 reported estimated half-lives in natural waters and soils of 4-52 and 4-26 weeks. Model calculations with the Syracuse BIOWIN model results in the following classifications: - HCBD does not biodegrade fast; - Ultimate biodegradation timeframe: recalcitrant; - Primary biodegradation timeframe: weeks. Based on the structure of HCBD it can be expected that first a dechlorination step is necessary before aerobic biodegradation can occur. This is confirmed by the degradation results in sediments supported by model calculations using the BIOWIN model, but contradicted by results from a controversial type of ‘adaptation-test’ in water. It is concluded that the – although scarce – information and expert judgement conclusions indicate that HCBD meets the criterion for persistence

3 Bioaccumulation Several bioaccumulation fish studies are available. However, only the study with O. mykiss is suitable for deciding if HCBD meets the bioaccumulation criterion.

Organisms BCF (L/KG) Comments Limanda limanda 700 (muscle) Exposure period: 27-39 days; exposure 10,000 (liver) concentration: 1.6 μg/l Micropterus salmoides 2.2-112.9 Exposure period: 10 days Pleuronectes platessa 500 (muscle) Exposure period: 21-106 days; exposure 7000 (liver) concentration: 1.7 μ/l Oncorhynchus mykiss 2000-6700 Exposure period: 8-119 days; exposure concentration: 0.1 ng/l; BCF based on wet weight; flow through Oncorhynchus mykiss 16000-19000 Exposure period: 7-105 days; exposure concentration: 3.4 ng/l; BCF based on wet-weight; flow through

4 Potential for long-range environmental transport The vapour pressure of HCBD at 20-25 °C is 20-32 Pa. The estimated half-life in air is 356 days based on 12-hour day and 1.5*106 OH/cm3. Mantseva et al (2004)7 developed a transport model for the evaluation of long-range atmospheric transport and deposition of POPs. Based on this model assessment a transport distance in Europe of almost 8800 km is calculated for HCBD. The residence time of HCBD in the atmosphere estimated on the basis of model calculations of its atmospheric transport is amounted to 118 days (see also Vulykh et al 2005)8. In Sweden HCBD was detected in air samples (8 samples, median conc. 0.16 ng/m3) and in atmospheric deposition samples (2 samples, max. conc. 0.042 ng/m2.day) collected in the Stockholm area (Kaj and Palm 2004)9. In sewage sludge and sediment no HCBD was observed (detection limit 4 μg/kg dry weight).

5 D.L James (2009). Biochemical dechlorination of hexachloro-1,3-butadiene. PhD thesis. (available at http://researchrepository.murdoch.edu.au/1674/2/02Whole.pdf) 6 Environment Canada and Health Canada (2000). Canadian Environmental Protection Act, 1999. Priority Substances List Assessment Report Hexachlorobutadiene (available at http://dsp- psd.pwgsc.gc.ca/Collection/En40-215-58E.pdf). 7 Mantseva E, S Dutchak, O Rozovskaya, V Shatalov. 2004. EMEP contribution to the preparatory work for the review of the CLRTAP Protocol on Persistent Organic Pollutants. EMEP MSC-E Information Note 5/2004. Meteorological Synthesizing Centre –East, Moscow, Russia. 8 Vulykh N, S. Dutchak, E. Mantseva, V. Shatalov. 2005. Model assessment of potential for long-range transboundary atmospheric transport and persistence of Hexachlorobutadiene. EMEP contribution to the preparatory work for the review of the CLRTAP Protocol on Persistent Organic Pollutants. Meteorological Synthesizing Centre –East, Moscow, Russia. 9 Kaj L, A Palm. 2004. Screening av Hexaklorbutadien (HCBD) i Miljon. (Screening of Hexachlorobutadiene (HCBD) in the Environment). Report B1543, Swedish Environmental Research Inst. (IVL), Stockholm, Sweden

3 UNEP/POPS/POPRC.7/3 HCBD has been detected in different arctic species. Vorkamp et al (2004)10 analysed HCBD in biota from Greenland and measured the following concentrations:  terrestrial species (ptarmigan muscle: 5 ng/g lw (0.19 ng/g ww), lower concentrations in lamb and muskox);  marine invertebrates (max. 0.57 ng/g lw);  marine fish (atlantic cod muscle 2.6 ng/g lw (0.02 ng/g ww), redfish muscle 2.1 ng/g lw (0.04 ng/g ww), lower in other species);  seabirds (3.4 ng/g lw in the muscle of common eider (0.1 ng/g ww), lower in other species) and;  marine mammals (median concentration of 0.40 and 0.80 ng/g lw (0.35 and 0.70 ng/g ww) in blubber of beluga and narwhal respectively).

HCBD was also detected in 5 out of 15 plasma and fat samples of polar bear from the arctic Svalbard Islands with an average concentration of 3.7 and a maximum of 8.9 ng/g ww (Gabrielsen et al 2004)11.

5 Adverse effects HCBD is as a vapour irritating to mucous membranes and corrosive as a liquid. HCBD should be regarded as a sensitising agent. HCBD is slightly to moderately toxic to rats based on acute oral tests. The target organ for toxicity is the kidney. Dose-related effects were a decreased relative kidney weight and tubular epithelial degeneration. The NOAEL in a 2 year oral study with rats was 0.2 mg/kg bw based on renal toxicity. The same NOAEL was determined in a 90 day oral study with mice. In a short-term inhalation study similar effects on the kidneys were observed. There is limited evidence for the genotoxicity of HCBD in animals and insufficient evidence in humans. Based on one oral study in rats there is limited evidence for the carcinogenicity of HCBD in animals and insufficient evidence in humans. An increased incidence of renal tubular neoplasms was observed but only at the highest dose of 20 mg/kg bw which also caused marked nephrotoxicity. The International Agency for Research on Cancer (IARC) has placed HCBD in Group 3: substances which cannot be classified because of insufficient data Ecotoxicological data are available for several species. Acute LC50 values vary from 0.032 mg/l for Palaemonetes pugio to 4.5 mg/l for Poecillia latiphinna. In an ELS test with Pimephales promelas a NOEC of 6.5 μg/l was observed. Only one reliable study is available for birds: in a 90 day study with Japanese quail a NOAEL of 3 mg/kg bw was found.

6 Statement of the reasons for concern According to the available data, HCBD is persistent in the environment and is found in environmental compartments. It has a great potential for bioaccumulation. Due to its physical and chemical properties and atmospheric half-life, and based on modelling data and findings in environmental samples, it has been proved that HCBD is transported long distances, far from its sources. HCBD is very toxic for aquatic organism and it is a nephrotoxic substance. Although HCBD production seems to have ceased in Europe and North America, it is unclear whether it may be still produced and used in other parts of the world. In addition, emission of HCBD to the environment can occur from the production of chlorinated hydrocarbons, from the disposal of waste from of production of chlorinated hydrocarbons containing HCBD and from magnesium production. Due to its harmful POP properties and risks related to its possible continuing production, use and releases to the environment, international action is warranted to control this pollution ______

10 Vorkamp K, Riget F, Glasius M, Pecseli M, Lebeuf M, Muir D. 2004. Chlorobenzenes, chlorinated pesticides, coplanar chlorobiphenyls and other organochlorine compounds in Greenland biota. Sci Total Environ. 2004 Sep 20;331(1-3):157-75. 11 Gabrielsen GW, LB Knuden, J Verreault, K Pusk, DC Muir, RJ Letcher. 2004. Halogenated organic contaminants and metabolites in blood and adipose tissue of polar bears (Ursus maritimus) from Svalbard. SFT project 6003080. Norsk Polar Institut. SPFO report 915/2004.