UNITED NATIONS SC

UNEP/POPS/POPRC.12/INF/12 Distr.: General 25 July 2016 English only Stockholm Convention on Persistent Organic Pollutants

Persistent Organic Pollutants Review Committee Twelfth meeting Rome, 1923 September 2016 Item 4 (c) (ii) of the provisional agenda* Technical work: consideration of recommendations to the Conference of the Parties: unintentional releases of hexachlorobutadiene

Draft evaluation of new information in relation to listing of hexachlorobutadiene in Annex C to the Stockholm Convention

Note by the Secretariat As referred to in the note by the Secretariat on new information in relation to the listing of hexachlorobutadiene in Annex C to the Stockholm Convention (UNEP/POPS/POPRC.12/6), the annex to the present note sets out the draft evaluation of new information in relation to listing of hexachlorobutadiene in Annex C to the Stockholm Convention. The present note, including its annex, has not been formally edited.

* UNEP/POPS/POPRC.12/1.

250716 UNEP/POPS/POPRC.12/INF/12 Annex

Draft evaluation of new information in relation to the listing of hexachlorobutadiene in Annex C of the Stockholm Convention

June 2016

2 UNEP/POPS/POPRC.12/INF/12 Table of Contents

Executive summary ...... 4

1. Introduction ...... 6 1.1 Overview ...... 6 1.2 Background to hexachlorobutadiene ...... 7 1.3 Aims of the evaluation ...... 8

2. Assessment of new information (since development of the draft risk management evaluation) . 8 2.1 Review of information provided by parties and observers ...... 8 2.1.1 Introduction to review of information provided ...... 8 2.1.2 Sources of unintentional formation, releases and emissions of hexachlorobutadiene identified in the risk management evaluation for the chemical as well as new sources ... 8 2.1.4 Alternative processes for the production of halogenated chemicals to reduce and elimate the unintentional production of hexachlorobutadiene ...... 10 2.1.5 Substitution of chlorinated chemicals identified as a source of unintentional releases of hexachlorobutadiene ...... 10 2.1.6 Cost of measures implemented to reduce and/or eliminate unintentional releases of hexachlorobutadiene ...... 12 2.2 Review of other new information (since development of the draft risk management evaluation) ...... 12 2.2.1 Introduction to review of other new information ...... 12 2.2.2 Unintentional releases from manufacturing of chlorinated ...... 13 2.2.3 Unintentional releases from incineration processes ...... 13 2.3 Development of an emission profile for hexachlorobutadiene ...... 14

3. Assessment of unintentional sources of hexachlorobutadiene ...... 15 3.1 Major unintentional emission sources ...... 15 3.1.1 Estimated global releases of hexachlorobutadiene ...... 15 3.1.2 Unintentional releases from manufacture of chlorinated solvents ...... 17 3.1.3 Unintentional releases from manufacture of Magnesium ...... 18 3.1.4 Unintentional releases from PVC production and manufacture of Vinyl Chloride Monomer (VCM) and Ethylene Dichloride (EDC) ...... 18 3.1.5 Incineration of waste (hazardous wastes and plastic containing waste) ...... 19 3.2 Assessment of existing control measures for major unintentional emission sources ...... 19 3.2.1 Potential control measures for unintentional emissions of hexachlorobutadiene ...... 19 3.2.2 Efficacy and efficiency of control measures ...... 21 3.2.3 Positive and/or negative impacts on society of implementing possible control measures ...... 22 3.3 Monitoring data for unintentional sources of hexachlorobutadiene ...... 22

4. Summary and conclusion ...... 23 4.1 Summary of information ...... 23 4.2 Conclusion ...... 24

5. References ...... 25

3 UNEP/POPS/POPRC.12/INF/12

Executive summary 1. During the ninth meeting of the Persistent Organic Pollutants Review Committee, a risk management evaluation for hexachlorobutadiene (HCBD) was presented (see Decision POPRC-9/2 and UNEP/POPS/POPRC.9/13/Add.2) and a decision made to recommend to the Conference of the Parties that it consider listing HCBD in Annexes A and C to the Convention (Decision POPRC-9/2). 2. At its seventh meeting (May 2015), the Conference of the Parties adopted decision SC-7/11, which proposed to list HCBD in Annex A of the Stockholm Convention without specific exemptions. In the same decision, the Conference of the Parties requested the Committee to further evaluate HCBD on the basis of the newly available information in relation to its listing in Annex C. This further evidence and recommendation to the Conference of the Parties on whether to list HCBD in Annex C would then be put forward for consideration at its eighth meeting (May 2017). 3. This document provides an overview of new information on unintentional releases of hexachlorobutadiene to assist the further evaluation by the Committee of the unintentional production of hexachlorobutadiene. In compiling this information the drafter has taken note of the new information provided by parties and observers of the Convention in line with Decisions SC-7/11 and POPRC-11/5. 4. As outlined in the risk management evaluation (UNEP/POPS/POPRC.9/13/Add.2), HCBD is a halogenated aliphatic compound which has been used in several technical and agricultural applications, e.g. as an intermediate in the chemical industry or as a commercial product in its own right (chemical identity see UNEP/POPS/POPRC.9/13/Add.2). In the past, it was intentionally produced and applied, e.g. as a (for rubber and other polymers); as a “scrubber” to recover -containing gas or to remove volatile organic components from gas; as hydraulic, heat transfer or transformer fluid; in gyroscopes; in the production of aluminium and graphite rods; and as a plant protection product. HCBD is not known to be currently intentionally produced or used (UNEP/POPS/POPRC.9/13/Add.2). 5. HCBD is unintentionally formed and released from industrial processes and other sources. Relevant sources are (a) the production of certain chlorinated , (b) production of magnesium, and (c) incineration processes (e.g. motor vehicle emissions, incineration processes of acetylene, incineration of chlorine residues where poor abatement control is in place). Releases can be minimised by alternative production processes, improved process control, emission control measures, or by substitution of the relevant chlorinated chemicals. Listing of HCBD in Annex C would subject this substance to the measures under Article 5 (measures to reduce or eliminate releases from unintentional production) of the Convention, and establish the goal of continuing minimization and, where feasible, ultimate elimination of HCBD releases. This would include an obligation to promote and require the use of best available techniques (BAT) for new HCBD sources if a Party has identified them as warranting such action in its action plan. Furthermore, parties shall promote the use of best environmental practices (BEP) for new HCBD sources, and promote the use of BAT/BEP for existing source of HCBD. Where production processes and supply chains are complex it would also mean closer tracking and monitoring of HCBD emissions from key points in the supply chain. 6. Currently, important releases of HCBD originate from the production of certain chlorinated chemicals particularly trichloroethylene, and . Based on this, estimates of releases can be derived from chlorine production data; for example, estimates for the UNECE Europe region finds that emissions to air are ~2.59 tonnes/year based on 1997 EU-25 chlorine production data (Van der Gon et al., 2007). More recently, estimates show that between ~0.7 kg/year up to a possible ~500 kg/year of HCBD are released during the production of various chlorinated chemicals (European Commission, 2012). Information based on a low number of samples and facilities indicate that releases from (a) production of relevant chlorinated solvents to air and solid residues can be negligible under BAT/BEP conditions and (b) from municipal and hospital waste incineration processes to solid residues can be negligible under BAT/BEP conditions. Specific data on releases to air from municipal and hospital waste incineration are not available. 7. Within many of the parties to the Stockholm Convention, the manufacture and use of trichloroethylene, tetrachloroethylene and carbon tetrachloride have been phased out or strictly controlled. There are exceptions e.g. carbon tetrachloride still remains of interest due to its use as an intermediate feedstock in the manufacture of hydrofluorocarbons (HFCs) compounds in some Party nations as described by Hu (2015) at the eleventh meeting of POPs Review Committee. It has also had application within the dry cleaning industry. Studies by Zhang et al. (2014; 2015) suggested that the continued use of carbon tetrachloride, without appropriate management, may represent a significant

4 UNEP/POPS/POPRC.12/INF/12 emission source of HCBD within the supply chain, although only limited data exist to quantify the potential unintentional emissions. 8. For the UNECE countries emissions of HCBD associated with unintentional sources have declined significantly over time. In the USA, 50 tons (US) were released to the environment in 1975 (US Department of Health and Human Services, 1994) compared to about 2 tons (US) in 2000 (UNEP/POPS/POPRC.9/13/Add.2). Similarly, a report by INERIS (2005) states that for the EU: in 1997 releases of HCBD amounted to 2 kg to air and 100 kg to water, which represented a 98% and 97% reduction in emissions respectively compared to 1985. These declines in emissions were likely caused by a combination of phase-out of production of specific chloro-organic substances, improved process design meaning reduced quantities needed, and application of improved abatement systems to meet the (requirements) of BAT and BEP. In Europe, HCBD emissions to air from chlor-alkali production sites have decreased to almost zero (Lecloux 2004 as cited in UNECE 2007). While the emissions to environment of HCBD within UNECE countries have declined signficantly (>95%) from phase out of specific substances, substitution with safer alternatives and through the implementation of BAT and BEP to control emisions, emissions in other global areas are less well defined. The importance of carbon tetrachloride as a feedstock in HFC production, along with the manufacture of chloromethanes and potential for HCBD as a contaminant of carbon tetrachloride, highlight potentially significant but not well understood sources of emissions 9. For industrial processes, particularly those related to the manufacture of certain chloro- organics, unintentional releases of HCBD can be minimised by abatement techniques and primary measures. Possible measures to minimise releases from unintentional formation as a by-product are e.g. to modify processes and process control; or by destruction and/or in-process recycling of HCBD according to BAT and BEP; or to apply alternative processes, such as closed loop systems or the substitution of the associated chlorinated hydrocarbons in various uses to avoid HCBD by-product formation. Currently, high temperature incineration is operated in some developed countries as an emission control technique for residues from the production of those relevant chlorinated chemicals. In France, stripping is also applied as a control technique for HCBD removal in one chlorinated solvent producing plant. In the USA, most of the disposed waste from the production of those relevant chlorinated is incinerated. 10. Although incineration of HCBD containing waste may be utilized in some developed countries, it may not be the most cost-effective option in all countries. For example, in some countries (e.g. small island countries) appropriate waste treatment facilities may not be available and additional costs may be incurred to store and then ship wastes to out-of-country treatment facilities. This movement of waste is addressed by the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and Their Disposal. 11. Monitoring of HCBD will induce additional costs; however, such costs for implementation of measures to reduce releases of HCBD, enforcement and supervision are considered low as the control measures for other unintentional POPs such as PCDD/PCDF are already applied. An important issue would be to ensure monitoring capacity for HCBD in developing countries and countries with economies in transition. 12. The evidence reviewed suggests that the potential unintentional generation and release of HCBD from unintentional sources has declined from a number of key sources since the 1970s. However, the existing and remaining sources are still important to the generation and release of HCBD. In some cases while it is possible to suggest that significant sources still exist, the full quantification of these releases is still not fully understood. Application of BAT and BEP has strong beneficial effects to further control and reduce emissions. Listing of HCBD in Annex C would help to further manage this issue at a global level.

5 UNEP/POPS/POPRC.12/INF/12

1. Introduction 1.1 Overview 13. During the ninth meeting of the Persistent Organic Pollutants Review Committee, a risk management evaluation for hexachlorobutadiene (HCBD) was presented (see Decision POPRC-9/2 and UNEP/POPS/POPRC.9/13/Add.2) and a decision made to recommend to the Conference of the Parties that it consider listing HCBD in Annexes A and C to the Convention (Decision POPRC-9/2). 14. At its seventh meeting (May 2015), the Conference of the Parties adopted decision SC-7/12 whereby it decided to list HCBD in Annex A to the Convention. By decision SC-7/11, the Persistent Organic Pollutants Review Committee was requested to further evaluate HCBD on the basis of the newly available information in relation to its listing in Annex C. Taking note of new information with regard to unintentional production of HCBD and additional information submitted by parties and observers, the Committee was requested to make a recommendation on listing HCBD in Annex C for further consideration at the eighth Conference of the Parties. Taking note of decision SC-7/11, the Committee established an intersessional working group to undertake the activities requested in paragraphs 1 and 3 of decision SC-7/11. The Committee also requested the Secretariat to collect any additional information from parties and observers that would assist the further evaluation by the Committee of the unintentional production and release of HCBD (Decision POPRC-11/5), including in particular information regarding: (a) Further detail on the sources of unintentional formation, release and emission of HCBD identified in the risk management evaluation for the chemical as well as new sources; (b) Standard methods for sampling, monitoring, analysis and reporting of unintentional releases of HCBD in various media; (c) Risk management measures implemented by parties and other stakeholders to reduce and eliminate unintentional emissions and releases of HCBD to air, water and sludge and as a constituent in products; (d) Alternative processes for the production of halogenated chemicals to reduce and eliminate the unintentional production of HCBD; (e) Substitution of chlorinated chemicals identified as a source of unintentional releases of HCBD; (f) Monitoring data on unintentional releases of HCBD; (g) Cost of measures implemented to reduce and/or eliminate unintentional releases of HCBD.

15. The deadline for submission was 15 January 2016. The following parties and observers have submitted additional information to the Secretariat1: Table 1: New information provided by parties and observers to the Secretariat Referencing Party/Observer Title of submission Date Format Council Directive of 16 June 1988 Netherlands - 07.01.2016 (88/347/EEC) Hexachlorobutadiene BUA- Netherlands BUA 1991 07.01.2016 Stoffbericht 62, 1991 Netherlands Chlorine Industry Review 2006-2007 Eurochlor 2007 07.01.2016 Hexachlorobutadiene, HCBD, Netherlands INERIS 2005 07.01.2016 INERIS 2005 Report of the Nicole Workshop, Netherlands NICOLE 2004 07.01.2016 Nicole Projects Reporting Day, 2004 Source screening of priority Netherlands WFD 2004 07.01.2016 substances under the WFD, 2004

1 Available at http://chm.pops.int/TheConvention/POPsReviewCommittee/Meetings/POPRC11/POPRC11Followup/HCBDInfo Request/tabid/4813/Default.aspx (accessed on 16.02.2016).

6 UNEP/POPS/POPRC.12/INF/12 Referencing Party/Observer Title of submission Date Format Annex 1 to the draft document Netherlands “Exploration of management options UNECE 2007 07.01.2016 for HCBD” 2 May 2007 USA Submission USA 2016 20.01.2016 IPEN Submission IPEN 2016 15.01.2016

16. In addition to the information provided by parties and observers, further information has been gathered from other open information sources and literature. Such information sources are listed in the reference section. 17. After this introductory section (section 1), discussion of the new information that has been provided or gathered since the draft risk managentment plan (UNEP/POPS/POPRC.9/13/Add.2) is presented in section 2. The document then provides an overview of the key unintentional emission sources, the potential controls and measures, and where possible monitoring data. The information which is presented in section 3 has been based as far as possible upon the new information detailed in section 2. However, where data gaps exist, information has also been taken from the risk management evaluation to ensure a complete picture and full context. The final section of this document (section 4) summarises those findings presented and includes conclusions of the evaluation. 1.2 Background to hexachlorobutadiene 18. HCBD is a halogenated aliphatic compound which has been used in several technical and agricultural applications e.g. as intermediate in the chemical industry or as a commercial product in its own right (chemical identity see UNEP/POPS/POPRC.9/13/Add.2). In the past it was intentionally produced and applied e.g. as a solvent (for rubber and other polymers), as a “scrubber” to recover chlorine-containing gas or to remove volatile organic components from gas, as hydraulic, heat transfer or transformer fluid, in gyroscopes, in the production of aluminium and graphite rods and as a plant protection product. HCBD is not known to be currently intentionally produced or used (UNEP/POPS/POPRC.9/13/Add.2). 19. HCBD is unintentionally formed and released from industrial processes and other sources. Relevant sources are (1) the production of certain chlorinated hydrocarbons, (2) production of magnesium, and (3) incineration processes e.g. motor vehicle emissions, incineration processes of acetylene, uncontrolled incineration of chlorine residues, incineration of hazardous waste and plastic containing waste (Deutscher and Cathro, 2001; Lenoir et al, 2001; Van der Gon, 2007; European Commission, 2012). Releases can be minimized by alternative production processes, improved process control, emission control measures, or by substitution of the relevant chlorinated chemicals. Listing of HCBD in Annex C would subject this substance to the measures under Article 5 (Measures to reduce or eliminate releases from unintentional production) of the Convention, and establish the goal of continuing minimization and, where feasible, ultimate elimination of HCBD releases with the use of best available techniques (BAT) and best environmental practices (BEP). 20. Cost effective BAT and BEP to reduce releases of unintentionally produced HCBD are available and described in relevant documents (the UNEP BAT and BEP guidelines (UNEP 2007) and in relevant EU guidance on best available techniques (BREF documents) (EC BREF LVOC 2003, EC BREF NFM 2014). Parties to the Convention already have obligations to implement control measures for other unintentionally produced persistent organic pollutants (POPs) (hexachlorobenzene (HCB), pentachlorobenzene (PeCB), polychlorinated biphenyls (PCB), and polychlorinated dibenzo-p-dioxins and dibenzofurans PCDD/PCDF) under the Convention. Similar to HCBD, substances PCDD/F, HCB, PeCB and PCB are unintentionally formed and released from thermal processes involving organic matter and chlorine as a result of incomplete combustion or chemical reactions (see e.g. UNEP 2007). These substances have similar emission sources, as HCBD, and therefore, there is a potential for emission reductions for HCBD based on the use of abatement for existing Annex C substances against emissions of HCBD (UNEP/POPS/POPRC.9/13/Add.2). Many of those control measures already in place for (e.g) dioxins and furans and polychlorinated biphenyls will also be effective at controlling releases of HCBD. 21. Several applications of tetrachloroethylene, trichloroethylene, and carbon tetrachloride, which may lead to emissions of HCBD where production is inappropriately managed, have been phased out; for the remaining industrial uses, manufacturing processes have been improved in such a way that less product is required in the process. Moreover the production volumes of tetrachloroethylene and trichloroethylene are declining in several countries that are parties to the Convention. Furthermore, where safer and technically feasible and cost-effective alternatives for specific uses of 7 UNEP/POPS/POPRC.12/INF/12 tetrachloroethylene and trichloroethylene exist, the unintentional production of HCBD can be eliminated by substituting certain chlorinated chemicals by other alternatives. This demonstrates that measures to reduce unintentional releases of HCBD through listing in Annex C could positively impact human health and the environment if such measures are applied more widely. Additional costs to industry for applying BAT and BEP and for control measures and emission estimates are considered low based on the review discussed in the risk management evaluation. Monitoring of HCBD will require additional costs for establishing monitoring capacity for HCBD particularly in developing countries and countries with economies in transition. However, additional costs for implementation of measures to reduce releases of HCBD, enforcement and supervision are considered low within the risk management evaluation as the control measures for other unintentional POPs such as PCDD/PCDF which are already being applied. (UNEP/POPS/POPRC.9/13/Add.2). 22. Further information on unintentional production of HCBD and control measures for these releases is detailed in the risk management evaluation on HCBD (see section 2.1 and 2.2 of UNEP/POPS/POPRC.9/13/Add.2). 1.3 Aims of the evaluation 23. The present document is intended to support the POPRC in its work to further evaluate HCBD on the basis of the newly available information in relation to its listing in Annex C and to make a recommendation to the Conference of the Parties on listing HCBD in Annex C for further consideration at its eighth meeting. To this end, the information provided by parties and observers and additional relevant information related to measures to reduce or eliminate releases from unintentional production of HCBD is evaluated.

2. Assessment of new information (since development of the draft risk management evaluation) 2.1 Review of information provided by parties and observers 2.1.1 Introduction to review of information provided 24. This sub-section provides an assessment of the new information provided by parties and observers to the Secretariat of the Convention. The information provided has been categorized according to the bullet points under paragraph 14 of section 1. The discussion in this sub-section will provide the review of this assessment against those criteria as separate sub-headings. Only limited new information was provided. 2.1.2 Sources of unintentional formation, releases and emissions of hexachlorobutadiene identified in the risk management evaluation for the chemical as well as new sources 25. The Netherlands provided information on unintentional releases of HCBD within Europe (Netherlands 2016). Serbia has also provided confirmation that the production and placing of HCBD on the market is banned in Serbia (Serbia, 2016). Furthermore a UNECE document provides an overview of the past inventory on HCBD for the UNECE region (Netherlands 2016). 26. Another report provided by the Netherlands (INERIS 2005) was already evaluated for the development of the risk manangement evaluation. Further, the Netherlands provided a “Report of the Nicole Workshop, 2004” (Nicole 2004). This document was already considered for the risk manangement evaluation of HCBD. It contains information on unintentional releases from polluted sites but not on unintentional production of HCBD. It does not contain new information which is relevant in the context of the present evaluation. The German document (BUA 1991) provides a very good insight into the unintentional production of HCBD. The document has already been evaluated when developing the risk management evaluation. However, the document as well as its supplement from 2006 (BUA 2006) was analysed once again in detail in order to identify any additional relevant information on unintentional HCBD releases. The Netherlands further provided a document titled “Source screening of priority substances under the WFD” from 2004. The document enables conclusions to be drawn on possible sources of unintentional production of HCBD. Finally, the Netherlands submitted Annex 1 to the document “Exploration of management options for HCBD” 2 May 2007. The corresponding final UNECE document from 20 June 2007 (UNECE 2007) had already been considered for the risk manangement evaluation. 27. IPEN recalls in its submission that, according to the risk management evaluation (UNEP/POPS/POPRC.9/13/Add.2), HCBD can be unintentionally produced by the production of certain chlorinated hydrocarbons, production of magnesium, and incineration processes (IPEN 2016). According to the risk profile (UNEP/POPS/POPRC.8/16/Add.2) unintentional production of HCBD

8 UNEP/POPS/POPRC.12/INF/12 during production of chlorinated hydrocarbons includes, tetrachloroethylene, trichloroethylene and carbon tetrachloride (a.k.a. tetrachloromethane, Halon 104, Freon 10, etc.). A presentation by Mr. Hu at POPRC-11 indicates that carbon tetrachloride has been, or is currently used as a feedstock for products including HFC-236fa (C3H2F6), intermediates in production of vinyl chloride monomer (and subsequently pyrethroid pesticides), chlorocarbons (and subsequently to produce HFC-245fa (C3H3F5) and new hydrofluoro-olefin refrigerants), and HFC-365mfc (C4H3F5) (Hu 2015). HFC compounds are used as refrigerants but are also potent greenhouse gases2 (see IPEN 2016). Against this background, IPEN provides information on alternatives to relevant chlorinated hydrocarbons, pyrethroid pesticides and HFC refrigerants. With respect to releases from unintentional production of HCBD from incineration, IPEN recalls the obligations of parties according to Article 5 of the Convention and the Convention’s BAT/BEP guidelines and their relevance to practical considerations for reducing and eliminating POPs – including from incinerators. In the USA, national emission standards that require the use of best available control technologies have been developed for sources categories emitting HCBD, including rubber tyre production, chlorine production, and miscellaneous organic chemical processes. HCBD is listed as a hazardous air pollutant under section 112 of the Clean Air Act. In addition, HCBD is among the chemicals for which emissions/releases must be reported as part of the U.S. Toxics Release Inventory (TRI) program. The most recent information on U.S. HCBD air emissions is summarized in Table 2. (USA 2016): Table 2: Releases of hexachlorobutadiene to air reported in the USA NEI for 2011

Emission Sectors kg Fuel Combustion – Industrial Boilers, Internal Combustion Engines (ICEs) – Natural 0.01 Gas Fuel Combustion – Industrial Boilers, ICEs – Other 15 Industrial Processes – Cement Manufacturing 114 Industrial Processes – Chemical Manufacturing 415 Industrial Processes – Not Elsewhere Classified 145 Industrial Processes – Petroleum Refineries 1.18 Industrial Processes – Storage and Transfer 11 Solvent – Dry Cleaning 0.64 Solvent – Industrial Surface Coating & Solvent Use 0.02 Waste Disposal 362 Total 1064 Source: National Emissions Inventory (2011 v2); data originally reported as short tons, converted to kg here for ease of interpretation. Note: 1 short ton = 907kg. 28. In view of new information from the USA (USA 2016) and the Netherlands (WFD 2004), it is noteworthy that “mineral oil and gas refineries” are not considered as a possible source in the risk management evaluation. According to (USA 2016) petroleum refineries are release sources contributing around 1 kg/y to HCBD releases in the USA. According to the EU E-PRTR data, in 2009 one facility (energy sector: mineral oil and gas refineries, located in Italy reported releases of HCBD to water (1.1 kg). There are no releases reported from mineral oil and gas refineries for 2013, 2012, 2011, 2010, 2008 or 2007. (Source: E-PRTR3). Hence, compared to other sources, unintentional production of HCBD from oil and gas refineries appear to be of low relevance. 29. According to a statement from the European Chlor-Alkali industry “… a total cessation of emissions of HCBD was unrealistic and cannot be achieved” (EuroChlor 2007). This is already reflected in the risk management evaluationwhich notes that releases can be minimised by technical abatement measures to very low levels, but are not eliminated with the current industrial practices (UNEP/ POPS/POPRC.9/13/Add.2). 30. Relevant information from BUA (1991) and the update BUA (2006) is already contained in the risk management evaluation on HCBD (UNEP/POPS/POPRC.9/13/Add.2). Possibly relevant additional information from BUA 1991 and BUA 2006 is compiled in the following. 31. In Germany approximately 10 tonnes per annum of HCBD were emitted around 1990 from the production of endosulfan from hexachlorocyclopentadiene (HCBD content was approximately 0.2%). The HCBD content was separated and incinerated as hazardous waste (BUA 1991). Endosulfan is

2 See e.g. http://www3.epa.gov/ozone/geninfo/gwps.html. 3 http://prtr.ec.europa.eu/#/pollutantreleases. 9 UNEP/POPS/POPRC.12/INF/12 listed under the Stockholm Convention. The production of endosulfan from hexachlorocyclopentadiene is therefore nowadays not considered a relevant source of unintentional releases of HCBD. 32. HCBD was also used as intermediate for the manufacturing of flame retardants of polymer resins and plastics. Data on the HCBD content of corresponding flame retardants are reportedly not available (BUA 1991). 33. In a simulated waste incineration, Lahaniatis et al. incinerated chloroorganic solvents and PVC, and detected HCBD in the incineration gas. Lahaniatis et al. conclude that the polymers contained in waste cause the formation of HCBD in detectable concentrations (Lahaniatis et al. 1981). According to Lahaniatis (1991), it is possible that the incineration of polymers in the presence of inorganic chlorinated compounds causes the unintentional formation of HCBD (see BUA 1991). Measurement values of HCBD in off-gases from waste incineration are not available (BUA 1991 and BUA 2006). 34. Conversely Vehlow (1997) conducted studies that illustrated an increase in chlorine levels within municipal solid waste consigned to incinerators caused no significant increase in the concentration of organochlorines in the raw exhaust gas. Rigo et al (1995) also noted on real practice combustion facilities, including high chlorine industrial and hospital waste which identified a majority of (57) cases where a change in the chlorine content did not influence organochlorine formation. There is also evidence that formation of HCBD, like other organochlorines in waste gases can be created ‘de novo’ where poor temperature control of exhaust gases allows for formation of HCBD and other chloro-organic POPs such as dioxins and furans. 35. According to BUA 1991, the total releases of HCBD to the environment in Germany can not be calculated. There are no data on releases from the production of tetrachloroethylene and carbon tetrachloride, or from incineration of HCBD containing waste. Releases to the atmosphere from the use of tetrachloroethylene (below 0.56 kg/year) and carbon tetrachloride (negligible) are estimated to be very low. On the basis of very rough estimations, releases to water from processes in the chemical industry where HCBD arises were estimated to amount up to 620 kg/year. The annual load in the river Rhine was estimated as 70 kg/year and for the river Elbe it was estimated 150 kg/year (BUA 1991). According to updated estimates for the year 1995 releases are estimated as below 10 kg/year to air and below 14 kg to water (Böhm et al. 2002 quoted in BUA 2006). The estimated HCBD loading of the river Elbe decreased from 96 kg/year in 1989 to below 1.6 kg/year in 2004 (ARGE Elbe 2005b quoted in BUA 2006). 36. Environmental monitoring data from water sediments and suspended matter and from surface waters in Germany show very low levels which are in most cases below the limits of detection (BUA 2006). Considering the low environmental concentration levels, it can be expected that releases of HCBD in Germany are low. 37. The text reviewed has highlighted the main industrial sources of unintentional release of HCBD. An important source is manufacture of chloro-organic solvents, along with a series of secondary sources which produce HCBD. The data also highlights a declining trend in emissions, with data from BUA (1991 and 2006) suggesting emissions were higher in 1990s. Despite this decline in releases, the current set of emissions reflect that emissions at appreciable levels are still ongoing, which may be complicated by supply chain and management of waste. This last issue reflects varied processes and management across global regions. 2.1.4 Alternative processes for the production of halogenated chemicals to reduce and elimate the unintentional production of hexachlorobutadiene 38. Based on information from a manufacturer BUA 2006 concluded that there is no unintentional generation of HCBD from manufacturing of trichloroethane from carbon tetrachloride by catalytic hydration (BUA 2006). 2.1.5 Substitution of chlorinated chemicals identified as a source of unintentional releases of hexachlorobutadiene 39. The risk management evaluation on HCBD identifies the key source for the unintentional release of HCBD as being from the manufacture of specific chloro-organic substances, particularly trichloroethylene, tetrachloroethylene and carbon tetrachloride. IPEN provides specific information on alternatives to relevant chlorinated hydrocarbons (IPEN 2016) in the following paragraphs. Similar information has already been considered by the POPRC in the draft risk management evaluation on HCBD (see UNEP/POPS/POPRC.9/5). 40. According to the HCBD Risk Management Evaluation, “As the manufacturing of some chlorinated chemicals (e.g, perchloroethylene, trichloroethylene) is identified as a potential source of

10 UNEP/POPS/POPRC.12/INF/12 HCBD emission, reducing and ultimately eliminating their production when safer technically feasible and cost-effective alternatives are available could be an effective way to prevent the unintentional formation of HCBD and other POPs.” (UNEP/POPS/POPRC.9/13/Add.2). Because a range of alternatives to the use of relevant chlorinated solvents exist and are used in practice, there are significant economic, environmental, and health benefits to be achieved by switching to alternative non-halogenated cleaning solvents or processes. Examples include the use of aqueous solvents, carbon dioxide blasting, and the use of supercritical fluids, which can act as substitutes for chlorinated chemicals identified as a source of unintentional releases of HCBD4. 41. IPEN (2016) state that alternatives are available for tetrachloroethylene use in dry cleaning, vapor degreasing, and automotive aerosols. Alternatives to tetrachloroethylene for use in dry cleaning do exist, although information on uptake rates of alternatives is not available. Based on a limited study by TURI (2012) potential viable alternatives include professional wet cleaning, liquid carbon dioxide, high flash hydrocarbons, acetal, propylene glycol ethers, cyclic volatile methyl siloxane, and n-propyl bromide (TURI 2012). Of these n-propyl bromide is not considered a safer alternative due to its carcinogenicity, reproductive toxicity, and neurotoxicity (TURI 2012). Carbon dioxide is safer than tetrachloroethylene but requires use of high-pressure equipment and the potential for leaks. High flash point hydrocarbons demonstrate concerns for aquatic toxicity, bioaccumulation, and nervous systems effects. Acetal possesses similar aquatic toxicity as tetrachloroethylene and other toxicity information is lacking. Propylene glycol ethers could have potential effects on the liver, kidneys or central nervous system. The methyl siloxane compound exhibits aquatic toxicity and potential for bioaccumulation and persistence. Wet cleaning poses the least risk to human health and the environment of the seven alternatives. Wet cleaning also requires the least amount of energy and other cost savings since no solvent recovery system is required for use, although it does require additional water demands and potentially the use of detergents. This may represent an issue for areas with water scarcity. 42. Alternatives to tetrachloroethylene use in vapor degreasing include a variety of halogenated and siloxane-based substances. The Toxics Use Reduction Institute (TURI) has successfully worked with industries in Massachusetts (USA) to implement aqueous based cleaning for nearly 90% of all companies they have worked with (TURI 2006). 43. Tetrachloroethylene is widely used and sometimes at high concentrations in automotive aerosols including in brake cleaning, engine cleaning, and tire cleaning (TURI 2006). The Toxics Use Reduction Institute (TURI) identified some cost effective alternatives for these uses with an improved toxicity profile compared to tetrachloroethylene, but some substances were persistent or possessed other environmental, health, and safety characteristics of concern (TURI 2006). 44. Alternatives are also available for trichloroethylene use in adhesive and paint applications, and degreasing. Solvent-based adhesive alternatives include methylene chloride, acetone/heptane combinations, and n-propyl bromide. Each of these has health and environmental hazards that would make them questionable substitutes as discussed above. Other alternatives for adhesive applications include mineral spirits, petroleum-based solvents, petroleum distillates, and VM and P naphthas, although these also present health and environmental hazards. Alternatives that pose the least risk to human health and the environment are aqueous based carriers using latex or latex-synthetic blends and hot melt applications with the use of a solvent-free 100% solids method. Trichloroethylene is also used as a carrier in solvent-based paints. Alternatives include the use of aqueous-based latex paints (TURI 2006). For operations within the European Union solvent based systems in adhesive and paint applications will require a VOC-abatement system in order to meet emission standards. For aqueous based systems these energy and cost intensive abatement techniques are not necessary. 45. Metal degreasing was the second largest consumer of trichloroethylene in the USA in 2011 (14.7 %), next to HFC-134a production (83.6%) (see Glauser, J., and C. Funda. 2012). For metal degreasing, there are several proven alternatives to trichloroethylene including hydrocarbon-based solvents such as terpenes, alcohols, acetone, ketones, and acetate (TURI 2006). Safer alternatives include aqueous and semi-aqueous processes, including ultrasonic processing. TURI has also conducted performance evaluations for certain applications that demonstrate the efficacy of aqueous degreasing alternatives as performing comparably or better than trichloroethylene (TURI 2008). Examples of where aqueous degreasing processes for metal surfaces are used include e.g. automotive sector, for beverage cans or for coil coating. 46. Tetrachloromethane (also known as carbon tetrachloride, Halon 104, or Freon 10) is listed in the Montreal Protocol5 for global elimination due to its damaging impact on the stratospheric ozone

4 UNEP/POPS/POPRC.9/13-Add.2 citing TURI, 2006; 2008; 2012. 5 Article 2d.

11 UNEP/POPS/POPRC.12/INF/12 layer. Treaty measures called for total phase-out by 2010. This substance was used as a feedstock in the production of chlorofluorocarbons, in pharmaceuticals, pesticides, blowing agents, and as an industrial degreaser. In the 2002 Assessment of the Technical Options Committee, established under provisions of the Montreal Protocol, a range of alternative substances and processes were identified to reduce and eliminate the production and release of ozone-depleting chemicals, including carbon tetrachloride. 47. At POPRC-11, Hu (2015) mentioned the use of carbon tetrachloride to produce pyrethroid pesticides but the specific substances were not stated nor the pest-crop combinations that are supposed to address were provided. Some options for alternatives to address these crop-pest combinations could reportedly be investigated if this information was available (IPEN 2016). 48. The new information provided by IPEN which focuses on the generation of HCBD from manufacture and use of chloro-organic compounds (trichloroethylene, tetrachloroethylene, and carbon tetrachloride) has highlighted that a range of alternatives do exist. Where such alternatives are already in commercial use and have proven viability as substitutes for those compounds that lead to the generation of HCBD, there is good justification for the phase out of chloro-organic products that are linked to HCBD. 2.1.6 Cost of measures implemented to reduce and/or eliminate unintentional releases of hexachlorobutadiene 49. Costs to control releases of HCBD arise particularly at companies in the chemical sector where HCBD is unintentionally generated. Abatement techniques are available and are already in place in France. Specifc information on costs is not available (INERIS 2005). 50. Further information on costs of implementation to reduce and/or eliminate releases of HCBD was not provided, and thus information on this issue remains limited. 2.2 Review of other new information (since development of the draft risk management evaluation) 2.2.1 Introduction to review of other new information 51. In 2015 a study commissioned by the German EPA on “Identification of potentially POP- containing Wastes and Recyclates – Derivation of Limit Values” was finalised (BiPRO 2015). The study focussed among other aspects on HCBD in waste and recyclates and the proposal of low POP content limit values for wastes. The study contains some specific information which is considered relevant with respect to unintentional production of HCBD and which is summarised in the following paragraphs. 52. The study discusses different uses and sources of unintentional production of HCBD in Germany with a focus of its possible occurrence in waste (see BiPRO 2015): (a) HCBD occurs unintentionally as a by-product during the manufacture of certain chlorinated chemicals, from where it can enter waste streams or be released to the environment. Manufacturing plants are able to mostly destroy or recover HCBD in the process. Through technological measures environmental releases can be kept to a minimum. It was considered possible that incineration residues (slag)6 that occur from the production of chlorinated organic compounds contain HCBD; (b) Poorly controlled incineration processes (e.g. releases from vehicles, incineration of acetylene and waste containing chlorine) are considered potential sources of unintended HCBD releases; (c) In the past, magnesium has been produced by the German company Metaleurop (since 2007 rebranded to the Recylex business group). Currently Germany is not producing primary magnesium (MPK 2015); accordingly magnesium production is not considered a potential source of unintentional production of HCBD in Germany; (d) Regarding the generation of HCBD in the manufacture of certain plastics, WWF (2005) refers to a preliminary document from Environment Canada (2000). The final document (Environment Canada 2000) no longer mentions the manufacture of plastics. Apart from this there is no specific indication that HCBD occurs during the manufacture of plastics. Accordingly the risk management evaluation (UNEP/POPS/POPRC.9/13/Add.2) does not quote plastics manufacture as potential source

6 Ashes are fed back into the incineration process in German plants. Slag is the only waste-relevant output from the incineration process.

12 UNEP/POPS/POPRC.12/INF/12 of unintentional HCBD production. Thus plastics manufacture is not considered as a relevant source of HCBD. 2.2.2 Unintentional releases from manufacturing of chlorinated solvents 53. Trichloroethylene, which as previously described may be a source of unintentional production of HCBD, is being used as starting material for the manufacture of fluorocarbons or as a solvent for high precision surface cleaning and degreasing (SAFECHEM 2014). Furthermore it is applied in laboratories for asphalt density detection (BG RCI 2012). In Germany, in 1990, the output was around 58,000 t/year of trichloroethylene (GeoDZ 2015). The production in Europe more generally decreased to 25,000 t/year of trichloroethylene in 2006. In 2009 there were only two European companies still producing trichloroethylene (ECSA 2011; ECSA 2014). Specific figures for the current production output are not available (BiPRO 2015). 54. On behalf of DOW Deutschland samples of waste gas from a waste incineration plant using tetrachloroethene and tetrachloromethane in the production were analysed for HCBD. During the incineration of 650 kg waste material, containing 480 kg hexachlorobenzene and hexachlorobutadiene per hour at 1,400°C, the air flow was 2,950 m3 per hour. Different volume samples of waste gas were taken: one sample on the 24.03.1992 had a volume of 10 m3 and two samples on the 22.07.1992 had a volume of 10 litres. In both cases no HCBD was detected. The detection limit for the 10 m3 sample was 0.5 µg HCBD absolute, the detection limit for the 10 l samples was 0.01 µg/sample (= 1 µg/m3) (DOW 1992 b from (BUA 2006)). As such, HCBD releases to the atmosphere from incineration are to be expected minor for Germany (BiPRO 2015). 55. A communication from the DOW Deutschland company mentions HCBD releases from the incineration of production waste resulting from tetrachloroethene and tetrachloromethane manufacture. According to this, in 1998, 60 g of HCBD was emitted into the atmosphere that resulted from production waste containing circa 50% hexachlorobenzene and circa 40% HCBD besides (DOW 2005 cited from (BUA 2006)). DOW produces tetrachloroethene and tetrachloromethane at two plants in Germany. Production residues are directly incinerated on-site. Ashes do not accrue during this process since they are redirected to incineration. The only solid residue from incineration is slag. Routine tests are conducted to check on halogenated organic compounds and no relevant amount is detectable. HCBD is not considered an important pollutant in air emissions based on monitoring. Specific measurements of HCBD concentration in the incineration residues are not available. On the basis of available data an assessment of HCBD releases via ashes/slag from the production process of organic solvents is not possible (BiPRO 2015). Whether there are relevant amounts of HCBD in waste therefore remains unclear. In consultation with the German EPA, it was therefore agreed to take samples of slag. Two slag samples were procured and analysed for HCBD concentration. No HCBD was found above the detection limits (detection limits 8.87 µg/kg and 9.24 µg/kg). According to the analytical results, from these two samples, the authors concluded that there are no relevant amounts of HCBD in incineration residues from the incineration of production waste generated in the manufacture of relevant chlorinated solvents in Germany (BiPRO 2015). 56. The information from BiPRO 2015 enables the following conclusion to be drawn on unintentional production and emission of HCBD during manufacturing of relevant chlorinated solvents (based on a low number of samples from only two facilities): (a) Releases from production of relevant chlorinated solvents can be negligible under BAT/BEP conditions. In both, waste gases and incineration residues, HCBD was not found above detection limits. 2.2.3 Unintentional releases from incineration processes 57. The unintentional generation of HCBD has repeatedly been reported in the literature (e.g. Euro Chlor 2004; Lenoir et al. 2001). The formation of organochlorine compounds, including HCBD, during the incineration of acetylene has been described. Acetylene is a component of all incineration processes (Lenoir et al. 2001). Other sources also report the release of HCBD from incineration processes without defining them in more detail (WWF 2005; INERIS 2005, UBA 2006a). One source indicates that, in France, HCBD emissions occurred during the incineration of chlorinated residues in 2003 (INERIS 2005). Another source reports that HCBD was generated during incineration processes in a similar fashion to dioxins, furans and hexachlorobenzene (CEPA 1999). 58. HCBD is suspected to be created ‘de novo’ under similar incineration conditions to dioxins and furans, thus it can occur during waste incineration (e.g. incineration of municipal waste, medical waste and hazardous waste) and might enter the waste stream through incineration residues (ashes and slag). HCBD is not a standard parameter for the analysis of solid residues (BiPRO 2015).

13 UNEP/POPS/POPRC.12/INF/12 59. Research by BiPRO has shown that there is no specific information available in Germany on the HCBD contamination of waste streams from incineration processes. Specific measured values are not available. Therefore it was unclear whether relevant amounts of HCBD occur in waste. In Germany, around 30,000 t/year of incineration residues are produced from incineration of medical waste. Incineration plants in Germany process wastes for incineration which include: (a) 1,500 t/year from the incineration of infectious waste; (b) 4 million t/year incineration residues from municipal waste incineration plants; and (c) Up to 440,000 t/year incineration residues from hazardous waste incineration plants. Due to those high amounts, it was concluded that relevant amounts of HCBD might occur (BiPRO 2015). 60. In order to clarify the potential relevance of waste incineration processes as a source for unintentional releases of HCBD emissions, samples (ashes and slag) from municipal waste incineration plants (two plants) and hazardous waste incineration plants (two plants) were acquired. One of these plants for the incineration of municipal waste had separate ovens for the incineration of medical wastes. Off-gas purification for municipal and medical waste incineration are combined and the incineration residues accrue as a mixture. On the basis of the information available there is no German plant that treats off-gases from medical waste incineration separately or takes separate samples of incineration residues (BiPRO 2015). 61. The obtained samples were analysed for HCBD concentrations in order to estimate the potential relevance of waste incineration processes. HCBD was not found above the detection limits (detection limits ranging from about 9 to 10 µg/kg). The analytical results imply that HCBD is not present in incineration residues from municipal waste incineration in relevant quantities in Germany (on the basis of five random samples) (BiPRO 2015). However, specific data on releases to air from municipal and medical waste incineration are not available. 62. The information from BiPRO 2015 enables the following conclusions to be drawn on unintentional production and emission of HCBD during waste incineration (based on a low number of samples and facilities): (a) Releases of HCBD from municipal and hospital waste incineration processes can be negligible under BAT/BEP conditions. In incineration residues, HCBD was not found above detection limits. However, specific data on releases to air from municipal and hospital waste incineration are not available. 2.3 Development of an emission profile for hexachlorobutadiene 63. To aid in the assessment of substances and sources of unintentional release, it is useful to develop what is termed an emission profile. This is a table of information which helps define the key sources and emission routes for discussion. Such a profile can also be used to assess at regional and national levels whether the sources listed are still relevant to that particular region/nation. The table below has been developed based on the information from the risk management evaluation (UNEP/POPS/POPRC.9/13/Add.2) and information provided by parties and observers subsequent to the 11th meeting of POPRC. Table 3 is also intended to support the review of sources and data presented in Section 3. Table 3 Emission profile for hexachlorobutadiene Release Major/Minor Source Description References vectors release vector Chlorinated solvents (major) Most commonly By-product from Air Major/minor Van der Gon includes: production by (historically et al., 2007; trichloroethylene, chlorolysis major release European tetrachloroethylene vector but Commission, releases are now 2012 close to zero in UNECE region) Carbon tetrachloride By-product of Air Major/minor Zhang et al., methanol based (major in China 2015; IPEN, production of but minor/non- 2016

14 UNEP/POPS/POPRC.12/INF/12 chlorinated existent methanes elsewhere) Other (minor) Electrolytic By-product from Air and Air (Minor) Deutscher production of production by and Cathro Waste Waste water magnesium electrolysis (a 2001 water (Minor) secondary/minor production process for Mg) Vinyl chloride By-product from Air Minor Thornton, production the production of 2002 PVC and releases from accidental burning of PVC in fires in buildings, warehouses, or landfills Waste disposal During the Air Air (Major) Lenoir et al., incineration or (mainly 2001; Sewage sludge landfill of products fugitive UNECE, (Minor) containing HCBD emissions 2002; – rather Water (Minor) European than point Commission, source) 2012 Sewage sludge Water Motor vehicles Air Minor WWF 2005

3. Assessment of unintentional sources of hexachlorobutadiene 3.1 Major unintentional emission sources 64. This section provides an overview of the global estimated releases, emission trends and further discussion on the individual major sources for unintentional release of HCBD. 3.1.1 Estimated global releases of hexachlorobutadiene 65. Information presented under this heading has been based on the risk management evaluation data, plus any new data highlighted from Section 2. 66. HCBD is on the list of chemicals subject to reporting on emissions registration and transfer of pollutants from Mexico (Annex F, Mexico 2013). The main emission/discharge sources of HCBD are: (a) unintentional release during the production of certain chlorinated hydrocarbons, (b) emission from disposed waste of certain chlorinated hydrocarbons, (c) emissions from other commercial uses and (d) emission from magnesium production (Annex F, Nigeria, 2013). 67. Historically, releases in the UNECE region were significantly higher than at present (for example, in the USA 50 tons (US) were released to the environment in 1975 compared to about 2 tons in 2000) (UNEP/POPS/POPRC.9/13/Add). Equally, the INERIS (2005) report states that for the EU, in 1997 releases of HCBD amounted to 2 kg to air and 100 kg to water, which represented a 98% and 97% reduction in emissions respectively compared to 1985. 68. Currently, the greatest unintentional releases of HCBD are from the production of certain chlorinated chemicals (particularly tri- and tetrachloroethylene and carbon tetrachloride) where HCBD is formed as a by-product through chlorolysis. Based on this, estimates of the releases can be derived from chlorine production data; for example, older estimates for the UNECE Europe region show that emissions to air were ~2.59 tonnes/year based on 1997 EU-25 chlorine production data (Van der Gon et al., 2007). More recently, estimates show that between ~0.7 kg/year up to a possible ~500 kg/year of HCBD were released during the production of relevant chlorinated chemicals. This wide range is

15 UNEP/POPS/POPRC.12/INF/12 particularly due to uncertainties in the destruction efficiency (99.90 to 99.99%), the HCBD content in the manufacturing residues (7 to 10%) and the share which was incinerated (1 to 50%) (European Commission, 2012). Release estimates from unintentional sources in Canada in 2004 are comparatively low (below 100 g in total for all sources including: products or mixtures containing HCBD as a contaminant, chemical industry, vinyl chloride monomer manufacture). 69. In 2013, the most recent reporting year for the European Pollutant Release and Transfer Register (E-PRTR), releases of HCBD from industrial activities totalled 265 kg with 14 facilities reporting. These HCBD releases were to water from waste and wastewater management (11 facilities; 132.5 kg), production of basic organic chemicals (2 facilities; 129.0 kg) and disposal of hazardous waste (1 facility; 3.5 kg). Note that the release data from the E-PRTR only includes releases of HCBD to water above an emission limit of 1 kg per year. Reporting of releases to air is not obligatory, and corresponding releases are thus not reported. 70. Urban wastewater treatment plants are the second main sources of HCBD. HCBD in wastewater treatment plants accumulate in the sewage sludge. The amount of HCBD which ends up in the sewage sludge in the EU 27 is estimated to be approximately 6 kg/year. It must be noted that this estimation is based on the sewage sludge contamination data from China, since no data from European facilities were identified (European Commission, 2012). 71. In 2011, the most recent reporting year for the U.S. Environmental Protection Agency’s Toxics Release Inventory (US TRI), the on- and off-site disposal or other releases of HCBD totalled 1,187 pounds (538 kg) across nine U.S. facilities reporting. The majority of these HCBD releases were fugitive air emissions (794 pounds or 360 kg) and point source air emissions (270 pounds or 122 kg). 72. Zhang et al. (2015) provides data from a study from China on the manufacture of chloromethanes via the methanol process, which produces carbon tetrachloride as a by-product. In this study, carbon tetrachloride is described as a waste residue for disposal rather than a commercical product. Sampling and analysis of the carbon tetrachloride produced via this route found HCBD at concentrations of 81.7 µg/g. Zhang estimates that based on China production rates for chloromethanes that c.90,000 tonnes of carbon tetrachloride would be produced annually, equating to 7350 kg of HCBD as a contaminant in the carbon tetrachloride residue. It is unclear how these residues are further managed, and whether they could be recycled as feedstock in HFC production. 73. For other non-UNECE regions, information is scarce. There is still a potential for unintentional release of HCBD from the production of certain chlorinated chemicals in most parts of the world. Reports from South India suggest that there are substantial ongoing HCBD emissions from industry, with a study by Juang et al, (2010) on the Shan river in Taiwan to analysis surface water concentrations of HCBD. The river Shan river is known to be heavily polluted by industrial sources; but study results from Juang et al (2010) indicating concentrations of HCBD over the course of one year ranged from 50 µg/l to 700 µg/l, suggesting continued ongoing contribution of HCBD to surface waters. 74. A summary of available estimates for HCBD releases as discussed above is presented in table 4. Table 4: Summary of unintentional release data for hexachlorobutadiene Year Estimated unintentional Geographic scope Reference releases 1975 50 tons (US)/year (to air) USA US Department of Health and Human Services (1994); U.S. EPA (2003) 2000 2 tons (US)/year (to air) USA UNEP/POPS/POPRC.9/13/Add.2 2011 1,064 kg/year (from all USA USA, 2016 emission sources/ to air 2004 <100 g (to air+) Canada UNEP/POPS/POPRC.9/13/Add.2 2000 2.59 tonnes/year-1 (to air from UNECE Europe Van der Gon et al. 2007 the manufacture of chlorinated chemicals) 2012 ~0.7 – 500 kg/year (from the EU-27 European Commission, 2012 manufacture of chlorinated chemicals)

16 UNEP/POPS/POPRC.12/INF/12 2012 6 kg/year (to sewage sludge) EU-27 European Commission, 2012 2013 265 kg/year (to water from EU-28 E-PRTR (only includes releases over waste and waste water the emission limit of >1 kg per year) management) 2015 7,350 kg/year (from HCBD China Zhang et al., 2015 impurities in carbon tetrachloride)

3.1.2 Unintentional releases from manufacture of chlorinated solvents 75. HCBD can be unintentionally produced during the manufacture of certain chlorinated chemicals. Emissions of HCBD due to by-product formation can be minimized by improved process control or alternative production processes, by emission control measures or by substitution, which may vary depending on the specific operation (UNECE 2007). As outlined previously, the main chlorinated solvents associated with the unintentional production of HCBD include trichloroethylene, tetrachloromethane, tetrachloroethylene and carbon tetrachloride. 76. Production processes for the simultaneous manufacturing of tetrachloroethene and tetrachloromethane include the high-pressure and the low-pressure chlorolysis processes and both may produce traces of HCBD. The low-pressure chlorolysis process tends to produce more HCBD than the high-pressure process. However, the HCBD formed in the low-pressure chlorolysis process can be significantly reduced in a subsequent distillation step, followed by incineration of the HCBD- containing off-gas (UNECE 2007). 77. The unintentional HCBD waste by-product, generated during the production of chlorinated chemicals was 3,600 tonnes (8 million pounds) in 1975, and had increased to 12,700 tonnes (28 million pounds) in 1982. In 2014, facilities reporting to the Toxics Release Inventory (TRI) indicated they managed 4,992 tonnes (11 million pounds) of HCBD as production-related waste, of which approximately 1.2 tonnes (2,600 lbs) were released (US EPA 2016). 78. In 1979, about 4,500 tonnes of HCBD were unintentionally generated in Germany as a result of manufacture of certain chlorinated chemicals, of which 1,021 tonnes was exported, 3,400 tonnes incinerated and 100 tonnes landfilled. In 1991, the figures had decreased to a quantity between 550 to 1,400 tonnes generated of which about 300 tonnes were exported as a product, and 250 to 1,100 tonnes were recycled in the process (BUA 1991). 79. In 1980, about 10,000 tonnes of HCBD were unintentionally generated from the manufacture of certain chlorinated chemicals, in the (then smaller) European Union of which 1,000 tonnes was exported, 5,580 to 6,120 tonnes incinerated and 2,880 to 3,420 tonnes was landfilled. In 1990, in Western Europe, a HCBD quantity of waste between 2,000 to 49,900 tonnes was estimated to have been created (BUA 1991). 80. Some sources indicated that there has been production in Austria.7 In a 2001 report from the Austrian Umweltbundesamt (UBA AT, 2001), emission standards for HCBD have been provided, which suggest HCBD has been produced in Austria. The production of organochlorines was ceased in the 1990s (UNEP/POPS/POPRC.9/13/Add.2). 81. In Canada, HCBD was mainly released as a by-product from the production of tetrachloroethylene. It was also formed as a by-product from the manufacture of trichloroethylene, carbon tetrachloride, vinyl chloride, allyl chloride, and epichlorohydrin. It could be found in the fly ash during refuse combustion. The two Canadian tetrachloroethylene producers ceased production in 1985 and 1992 (CCME 1999). 82. Zhang et al. (2015) reported the unintentional release of HCBD during the methanol-based production of chlorinated methanes in China using 2010 data from a factory in the Shandong province. HCBD was identified among the compounds in the carbon tetrachloride by-product at a ratio of 2.03:100 relative to pentachloroethane. 83. As reported at the POPRC-11, there is additional evidence of unintentional releases of HCBD during the ongoing manufacture of carbon tetrachloride in China where it is used as a feedstock for products including HFC-236fa (C3H2F6), intermediates in production of chlorocarbons (and subsequently to produce HFC-245fa (C3H3F5) and new hydrofluoro-olefin refrigerants – as alternative refrigerants), and HFC-365mfc (C4H3F5). Although the use of carbon tetrachloride to

7 See e.g. http://monographs.iarc.fr/ENG/Monographs/vol73/mono73-14.pdf.

17 UNEP/POPS/POPRC.12/INF/12 produce pyrethroid pesticides was specified in the presentation, the specific substances used and the pest-crop combination the pesticides are intended for were not specified – more information is needed here to provide comment on this particular application. (UNEP/POPS/POPRC.9/13/Add.2; IPEN, 2016). In earlier published research, Zhang et al. (2014) also reported concentrations of between <0.1−9 ng/g of HCBD in soils near to plants producing chlorine, carbon tetrachloride, and triazine herbicides. 84. Currently, high temperature incineration is operated in some developed countries as an emission control technique for residues from the production of chlorinated chemicals. In France, stripping is also applied as a control technique for HCBD removal in one chlorinated solvent producing plant. In the USA, most of the waste from certain chlorinated hydrocarbon manufacturing processes is incinerated thereby limiting further emissions from such production processes. In Europe, HCBD emissions to air from chlor-alkali production sites have decreased to almost zero due to implementation of BAT/BEP measures. (UNECE 2007). In Thailand, there are no chlor-alkali plants (Thailand PCDD/F inventory 2005). 3.1.3 Unintentional releases from manufacture of Magnesium 85. The release of HCBD from the production of magnesium can occur during electrolysis (Deutscher and Cathro 2001). HCBD by-products from non-chemical facilities producing magnesium are thought to be less than those arising from the production of chlorinated solvents as the main global production of magnesium is currently carried out by the reduction of the oxide at high temperatures with silicon. 86. No publications on levels of unintentionally produced HCBD in air emissions from industrial magnesium production have been found. 87. Emissions of HCBD from the production of magnesium can potentially be controlled by using measures based on the use of BAT, consisting of scrubbing and incineration of off-gases. The off- gases are treated in a series of wet scrubbers and wet electrostatic precipitators, before finally being subject to incineration. Water from the off-gas treatment is transferred to a wastewater treatment plant. Since wastewater treatment plants are usually not specifically designed to remove HCBD and other POPs, this may result in discharges of HCBD and other POPs directly into water. These measures aim to reduce or minimise the emissions of hydrocarbons (including HCBD) and PCDD/PCDF. The BREF for non-ferrous metals (2014) describes these details within chapter 2.12.5.3 (techniques to reduce dioxins emissions) including process control and temperature management to prevent de novo formation of dioxins and furans and related compounds such as HCBD in exhaust gases. Section 2.12.6 provides information on waste-water management including integrated control (European Commission BREF NFM 2014). They are also consistent with the approach of Annex V of the Aarhus Protocol on Persistent Organic Pollutants (BAT to control emissions of POPs from major stationary sources) (UNECE 2007) (UNEP/POPS/POPRC.9/13/Add.2). 3.1.4 Unintentional releases from PVC production and manufacture of Vinyl Chloride Monomer (VCM) and Ethylene Dichloride (EDC) 88. HCBD may also be unintentionally released during PVC production and the manufacture of vinyl chloride monomer (VCM) and ethylene dichloride (EDC). EDC (also known as 1,2- dichloroethane) and VCM are the main ingredients used in the production of PVC. Ethylene dichloride (EDC) and vinyl chloride monomer (VCM) both contain a source of chlorine which can be converted to HCBD during production. This would leave trace impurities of HCBD in the EDC/VCM waste by- products created. In 1990, DOW Chemical reported that its EDC heavy ends comprised 65% chlorine, of which 1.2% was found to be HCBD (Thornton, 2002). 89. Unintentional HCBD releases from this source in developed countries are reportedly minor; particularly during the production phase as EDC and VCM are carefully monitored so as to avoid the release of HCBD in compliance with BAT and BEP. Unintentional releases during combustion of PVC are also minor but can occur from the accidental burning of PVC in fires in buildings, warehouses, or landfills (Thornton, 2002). 90. Sediment samples from close to an oxychlorination reactor (used in the manufacture of EDC) in Sweden contained a wide variety of persistent organochlorines, including HCBD at a level of 0.6 percent by weight (Johnston et al., 1993). High levels of persistent organochlorines were also identified in the water, sediment, and fish at another site near two EDC/VCM producing facilities in the U.S. In some of the sediment samples concentrations of HCB, HCBD, and HCE exceeded 1,000 ppm; together, representing between 0.1% and 4.8 percent of the sediment’s total mass (Curry et al., 1996; Meyer et al., 2002; Thornton, 2002).

18 UNEP/POPS/POPRC.12/INF/12 91. As reported at the POPRC11, there is additional evidence of unintentional releases of HCBD in China during the manufacture of carbon tetrachloride – used as an intermediates in the production of vinyl chloride monomer (and subsequently pyrethroid pesticides) (IPEN, 2016; UNEP/POPS/POPRC.9/13/Add.2). 3.1.5 Incineration of waste (hazardous wastes and plastic containing waste) 92. Wastewater treatment plants are a possible secondary source of HCBD. Zhang et al. (2014) conducted sampling analysis on 37 wastewater treatment plants from 23 cities in China with proximity to chemical plants. HCBD was found in 76% of the samples analysed. Comparison to a previous study from 1998 did show a significant decline in concentrations, with the likely source of HCBD a combination of industrial waste flows and cycling within the human population for those communities close to the location of production facilities. Where HCBD enters the wastewater systems for processing by such wastewater plants, HCBD can be released to water and soil via sewage sludge (ESWI 2011). 93. Lenoir et al. (2001) observed the by-product formation of organochlorine compounds including HCBD from incineration processes of acetylene, which was indicated as being present in the flames of all incineration processes. Releases from incinerators have been reported by WWF (2005) and INERIS (2005). In 2003, according to the Association of Plastic Producers (Syndicat des Producteurs de Matières Plastiques, SPMP) in France, traces of HCBD have been detected in the effluents of an incinerator eliminating chlorine residues – however, it is believed that such traces cannot be treated (INERIS 2005). It was also reported that HCBD releases can take place during waste incineration, and that combustion sources of HCBD are similar to those of dioxins, furans and hexachlorobenzene (Environment Canada 2000). (UNEP/POPS/POPRC.9/13/Add.2). 94. In the USA, there is evidence of HCBD releases during the incineration of vinyl products in the waste stream and during the recycling of vinyl-containing metal products by combustion (Thornton, 2002). 95. There is no insight into the total number of waste sites affected by HCBD worldwide, nor on their releases of HCBD from such waste sites (Crump et al., 2004). 3.2 Assessment of existing control measures for major unintentional emission sources 96. This section provides an overview of the existing known control measures, their efficacy and efficiency and potential positive/negative implications for wider adoption of control measures where currently not in use. This section of the document has largely been based upon the risk management evaluation with update based on the information provided in Section 2. 3.2.1 Potential control measures for unintentional emissions of Hexachlorobutadiene 97. HCBD is unintentionally produced and released from certain industrial processes as well as from waste (see Section 3.1.2-3.1.5). Unintentional releases of HCBD can be minimised by abatement techniques and legislation. Possible measures to minimise releases from unintentional production as a by-product are e.g. to modify processes and process control or destruction and/or in-process recycling of HCBD according to BAT and BEP, or to apply alternative processes, such as closed loop systems or the substitution of the associated chlorinated hydrocarbons in various uses to avoid HCBD by-product formation. Listing of HCBD in Annex C would subject the chemical to the measures under Article 5 of the Convention, and establish the goal of continuing minimization and, where feasible, ultimate elimination of HCBD releases with the use of best available techniques (BAT) and best environmental practices (BEP) for HCBD sources. The text under section 3.2.1, has been provided from the risk management evaluation as the most representative data available. Manufacture of chlorinated chemicals 98. The risk management evaluation states: HCBD can be unintentionally generated during the manufacture of certain chlorinated chemicals. For example, HCBD is still unintentionally generated during the production of certain chlorinated hydrocarbons. Emissions of HCBD due to by-product formation can be minimised by improved process control or alternative production processes, by emission control measures or by substitution. In case significant amounts of HCBD are being formed, there should be strict control to minimise and, where feasible, eliminate such releases. Emission controls utilised by operators should be based on applying BAT (UNECE 2007). HCBD formed in the low-pressure chlorolysis process can be significantly reduced in a subsequent distillation step, followed by incineration of the HCBD-containing off-gas (UNECE 2007).

19 UNEP/POPS/POPRC.12/INF/12 99. Currently, high temperature incineration is operated in some developed countries as an emission control technique for residues from the production of those relevant chlorinated chemicals. In France, stripping is also applied as a control technique for HCBD removal in one chlorinated solvent producing plant. In the USA, most of the disposed waste from chlorinated hydrocarbon manufacturing processes is incinerated thereby eliminating/reducing further HCBD emissions. In Europe, HCBD emissions to air from chlor-alkali production sites have decreased to almost zero (UNECE 2007). Although incineration of waste from the relevant chlorinated hydrocarbon manufacturing processes may be effectively be utilized in developed countries, it may not be the most cost-effective option in all countries. For example, in some countries (e.g. small island countries) appropriate waste treatment facilities may not be available and additional costs may be incurred to store and then ship wastes to out-of-country treatment facilities. 100. Relevant BAT is specified in the EU BREF Document on production of Large Volume Organic Chemicals (EC BREF LVOC, 2003). This document is currently under review and the final meeting of the IPPC bureau has taken place in April 2016. The document specifies BAT for pollution prevention and minimisation and for the control of pollutants and residues (EC BREF LVOC, 2003, section 6). Primary and secondary measures aiming to reduce/minimise emissions of polychlorinated dibenzo-p- dioxins and dibenzofurans (PCDD/PCDF) and/or certain chlorinated hydrocarbons from chemical production are also described in Section VI.F Part III Chapter 4 of the UNEP BAT and BEP guidelines (UNEP 2007). This section focuses on processes for the manufacture of industrial chemicals that could theoretically give rise to persistent organic pollutants (particularly those chemicals listed in Annex C of the Stockholm Convention). Most of the processes described share common steps, including chlorination of organic or inorganic raw materials, purification of the products, separation of product streams (usually by distillation), destruction of high-molecular-weight side products and recycle or sale of . Efficient separation and destruction of chlorinated organic side products, which may include persistent organic pollutants, is key to best available techniques applicable to these processes, as is the associated guidance for any incorporated incineration processes (UNEP 2007). 101. Related to certain chlorinated chemicals, it is outlined (see Section 3.1.2) that the process to generate trichloroethylene and tetrachloroethylene involves chlorination, oxychlorination and pyrolysis, with by-products that will include chemicals listed in Annex C, and HCBD. These by- products can be separated from final product by distillation and isolated in a fraction known as heavy ends. Many years ago, heavy ends material was commonly landfilled; however, since the 1970s, hazardous waste incineration, or thermal destruction with recovery and reuse of HCl, is by far the more common treatment in some developed countries (UNEP 2007). It can be concluded that specific BAT is already common practice in the manufacturing of those chlorinated chemicals addressed here in a number of parties to the Convention. Measures already taken for other POPs will also be effective for HCBD. 102. Monitoring of HCBD during industrial production will induce additional costs; however, based on the risk management evaluation costs for implementing of measures to reduce releases of HCBD in industry, enforcement and supervision (by regulatory bodies) are considered low as the control measures for other unintentional POPs such as PCDD/PCDF are already applied. Another key issue will be the monitoring capacity for HCBD at industrial sites needed in developing countries and countries with economies in transition in cases where such monitoring is not already in place to cover other related Annex C substances. 103. As the manufacturing of some chlorinated chemicals (e.g, tetrachloroethylene, trichloroethylene) are identified as a potential source of HCBD emission, reducing and ultimately eliminating their production when safer technically feasible and cost-effective alternatives are available could be an effective way to prevent the unintentional formation of HCBD and other POPs. This is particularly relevant when the manufacturing process does not use techniques aiming at reducing the production of HCBD. Information is available on some substitutes for relevant chlorinated chemicals (TURI, 2006; 2008; 2012). Manufacture of Magneisum 104. The risk management evaluation states: There may be substantial amounts of by-product formation from non-chemical facilities producing magnesium (UNECE 2007, Denier van der Gon et al. 2007). The available information indicates possible releases from production of magnesium by electrolysis (Deutscher and Cathro 2001). However, the main global production of magnesium is currently carried out by the reduction of magnesium oxide with silicone at high temperatures, a process that is not known to lead to unintentional production of HCBD. Nevertheless, industrial magnesium production by electrolysis is still relevant. However, no publications on measured HCBD air emissions from industrial magnesium production have been found. Possible emissions of HCBD

20 UNEP/POPS/POPRC.12/INF/12 from the production of magnesium can potentially be controlled by using measures based on the use of BAT, consisting of scrubbing and incineration of off-gases. The off-gases are treated in a series of wet scrubbers and wet electrostatic precipitators, before finally being subject to incineration. Water from the off-gas treatment is transferred to a wastewater treatment plant. Since wastewater treatment plants are usually not specifically designed to remove HCBD and other POPs, this may result in discharges of HCBD and other POPs directly into water. These measures aim to reduce or minimise the emissions of hydrocarbons (including HCBD) and PCDD/PCDF. The BREF for non-ferrous metals (2014) describes details of best practice for these processes (further discussion of the BREF document has already been provided in section 3.1.3 on the unintentional releases from manufacturing of magnesium). The details held by the BREF are also consistent with the approach of Annex V of the Aarhus Protocol on Persistent Organic Pollutants which now provides guidance on BAT controls for major stationary sources8 (UNECE 2007). Primary and secondary measures aiming to reduce or minimise emissions of PCDD/PCDF and/or chlorinated hydrocarbons from magnesium production are also described in Section VI.B Part III Chapter 4 (see table 11 and Table 12) of the UNEP BAT and BEP guidelines (UNEP 2007). Other potential sources for unintentional formation of HCBD 105. The risk management evaluation states “other sources of unintentional formation of HCBD concern incineration processes (e.g. motor vehicle emissions, incineration processes of acetylene, incineration of chlorine residues). Lahaniatis et al. 1981 identified HCBD in fly ash samples from municipal and industrial waste incineration in the Netherlands. Further specific information on these sources is lacking. For HCBD formed as a by-product in incineration processes, there is a relation between PCDD/PCDF and other unintentional POPs releases from combustion. Most measures taken to reduce such POPs releases will lead to a significant reduction of releases of HCBD. BAT and BEP relevant to unintentionally produced POPs for various types of incinerators and other thermal sources are described in the UNEP BAT and BEP guidelines, in Section V, and in several EU BAT reference documents. BAT includes providing for appropriate incineration conditions. BAT and BEP relevant to unintentionally produced POPs from motor vehicles are described in the UNEP BAT and BEP guidelines, in section VI.H. BAT includes banning of halogenated scavengers and fitting motor vehicles with an oxidation catalyst or particulate filter”. 3.2.2 Efficacy and efficiency of control measures 106. The Risk Management Evaluation states: "BAT and BEP to minimise unintentional generation of HCBD are described in relevant documents (see above) and are technically feasible. The technical measures required to minimize releases of unintentionally produced HCBD are already required in a number of parties to the Convention according to existing BAT and BEP in the industrial manufacturing of chemicals and magnesium and for other possible sources (motor vehicle emissions and incineration processes). BAT and BEP as described in the relevant documents are being applied for other unintentionally produced substances such as hexachlorobenzene (HCB), pentachlorobenzene (PeCB), polychlorinated biphenyls (PCB) and PCDD/PCDF and will be effective for HCBD as well. Monitoring of HCBD will induce additional costs. Additional costs for implementation of measures to reduce releases of HCBD, enforcement and supervision are considered low as the control measures for other unintentional POPs such as PCDD/PCDF are already applied. Monitoring capacity for HCBD is needed in developing countries and countries with economies in transition". 107. The most relevant known sources for HCBD releases are as a by-product unintentionally formed during the production of certain chlorinated chemicals. This unintentional production can be minimised by improved process control, alternative production processes, emission control measures or by substitution (UNECE 2007). For the production of those chlorinated hydrocarbons referred to here, incineration at high temperatures and stripping have proved to be cost-effective measures to reduce emissions. However, incineration may not be the most cost-effective option in all countries, and there are concerns regarding the possible unintentional formation of POPs, as noted in Part II of Annex C to the Convention. HCBD emissions in the USA and Europe have significantly decreased due to decreased unintentional formation and deployment of emission control measures. In many cases, current control measures and application of BAT and BEP to address other unintentionally produced POPs are likely to also reduce emissions of HCBD. If measures are taken to reduce PCDD/PCDF, there are no extra costs to industry for the reduction of HCBD emissions from magnesium production (UNECE 2007). According to Nigeria, control measures, when effectively applied, would eliminate emission of HCBD; however, the consequences of installing control

8 http://www.unece.org/fileadmin/DAM/env/documents/2009/EB/eb/POPs/Guidance%20document%20on%20BA T.e.pdf.

21 UNEP/POPS/POPRC.12/INF/12 measures need to be studied further. Some of the measures, like substitution of production processes, maintenance, and substitution of raw materials have been documented. However, for nations needing capacity building, technical and funding assistance may be necessary (Annex F, Nigeria, 2013). 108. In addition, the substitution of the relevant chlorinated chemicals in their specific applications can contribute to reducing the production of these substances and can thus contribute to reducing corresponding HCBD releases. Technically feasible and cost-effective alternatives to tetrachloroethylene and trichloroethylene are available for certain applications and could be employed as part of BAT to reduce HCBD emissions (see Section 2.1.5). 109. There will be additional costs for industrial monitoring, namely for chemical analysis, even if monitoring programmes for other POPs (e.g. PCDD/PCDF, HCB and PCB) are already established. However, where a number of Annex C substances have related sources, if the necessary systems and logistics for industrial monitoring is in place already, it is possible to off-set some of these additional monitoring costs. Within the UNECE region, control costs are expected to be low and could consist of extra costs for measuring of HCBD content in products or from unintentional emissions, and for conducting emission inventories (UNECE 2007). According to Mexico, costs should be considered for monitoring environmental levels in order to demonstrate that levels decrease as a consequence of the control measures taken. 3.2.3 Positive and/or negative impacts on society of implementing possible control measures 110. The Risk Management Evaluation states: “Cost efficient BAT and BEP to reduce releases of unintentionally produced HCBD are available and described in relevant documents (UNEP 2007, EC BREF LVOC 2003, EC BREF NFM 2014). Countries already have obligations to implement control measures for other unintentionally produced POPs (HCB, PeCB, PCB, PCDD/PCDF) under the Convention. These may be similar to those for HCBD. The potential unintentional sources of HCBD for certain chlorinated hydrocarbons have been phased out or are stringently regulated in various signature states, since a range of alternatives exist and are in practice for many of those applications. Measures to reduce unintentional releases of HCBD through listing in Annex C would positively impact human health and the environment. Additional costs for applying BAT and BEP and for control measures and emission inventories are considered low. According to Canada, the costs of inventories are relative and would differ in each country. For Canada, there are no known intentional sources, but based on the known various unintentional sources considerable effort would be needed to research all of the potential sources and establish which sources may be emitting. This would need to be flagged as soon as possible to ensure that sufficient resources were devoted to the research and development of the inventories. The 4th statement9 in the conclusion is about unintentional by-product formation and states that measures to reduce other POPs will also reduce HCBD releases. This is very difficult to characterize in an emissions inventory and requires detailed information from facilities on past releases”. 3.3 Monitoring data for unintentional sources of hexachlorobutadiene 111. Only limited monitoring data providing information onunintentional production and release of HCBD from industrial production processes are available. This also takes into account that the emissions of HCBD have declined for UNECE regions. Largely due to a phase out of specific chloro- organic substances, better process design and emissions abatement control following BAT and BEP. As noted in Section 3.1.1 emissions in the USA have declined from 50 tons (US) in 1975 to 2 tons (US) in 2000; and in Europe INERIS (2005) report for the EU a decline of 98% and 97% to air and water respectively based on emissions in 1997 (2 kg air, 100 kg water) compared to 1985. The remainder of this sub-section provides what academic data has been identified detailing emissions of HCBD. 112. According to Euro Chlor, the only remaining significant source of HCBD is the low pressure chlorolysis for the combined production of tetrachloroethylene and tetrachloromethane. The residues of the low pressure chlorolysis contain 0.2-0.5 % HCBD. After further distillation the residues finally obtained from the process contain 7-10 % HCBD. The HCBD-containing residues are generally destroyed on-site by incineration at high temperatures of about 1,200°C or internally recycled (Euro Chlor 2004).

9 Concluding statement from the Risk Management Evaluation: “Like other unintentionally produced POPs listed in the Convention (HCB, PeCB, PCB and PCDD/PCDF), HCBD is unintentionally generated during combustion and other thermal processes and industrial processes. Most measures to reduce unintentional releases of POPs from such processes will lead to significant reduction of HCBD releases. Monitoring of HCBD will induce additional costs. Monitoring capacity for HCBD is needed in developing countries and countries with economies in transition.”

22 UNEP/POPS/POPRC.12/INF/12 113. The Zhang et al. Study (2015) mentioned in Section 3.1.1 highlights the presence of HCBD as a contaminant within the manufacture of chloromethanes in China based on production data in 2010. In this case, a range of chloromethane products manufactured via the methanol route also generate carbon tetrachloride as a by-product at approximately 3% of production rates. Samples of carbon tetrachloride taken from a production plant in the Shandong province of China were analysed with detected concentrations of 81.7 µg/g. Based on production rates, this could equate to a quantity of 7350 kg per annum generated within carbon tetrachloride. The study by Zhang describes the carbon tetrachloride as a waste by-product. It is unclear whether it would be recycled into feedstocks for manufacture of HFC products. 114. Euro Chlor (2004) states that for manufacture of tetrachloroethylene that emissions of HCBD in the 1970s equated to approximately 1.5% of the tetrachloroethylene manufactured. However, this emission rate is unlikely to be reflective of modern plants utilizing BAT and BEP. 115. A study by Deutscher and Cathro (2001) analysed the emissions of HCBD from the electrolytic production of magnesium. During this study a range of organochlorine pollutants were detected, with a mean average concentration to air for the emission of HCBD being 2.8 g/tonne of magnesium produced. As this study was conducted within laboratory conditions, the emissions detected were unabated. No comment is made about the emission rates for commercial manufacture of magnesium, further noting that electrolytic manufacture of magnesium is a less preferred route.

4. Summary and conclusion 4.1 Summary of information 116. HCBD is a halogenated aliphatic compound which previously had several technical and commercial applications (e.g. as a solvent for rubber and other polymers) which have now ceased globally. It is also produced and released to the environment unintentionally from a small number of industrial production processes. These emissions have been dominated in particular by the manufacture of chloro-organic solvents, namely trichloroethylene, tetrachloroethylene and carbon tetrachloride. Secondary sources of unintentional releases of HCBD to the environment, some of which follows from the use of HCBD in the production of certain chloro-organic solvents, include the electrolytic manufacture of magnesium, manufacture of ethylene dichloride and vinyl chloride monomer and waste processes and uncontrolled incineration of wastes containing chlorine. 117. Emissions to the environment of HCBD within UNECE countries have declined dramatically with data from the USA and Europe showing declines of >95% since the 1970s. These declines reflect the phase-out of specific named chloro-organic substances (trichloroethylene, tetrachloroethylene, and carbon tetrachloride) known to generate HCBD. They also reflect improvement in industrial processes to reduce the quantities required for applications, substitution to less toxic alternatives, and improvement in abatement systems in industry to ensure compliance with BAT and BEP. In particular data from Germany (BiPRO 2015) discusses waste management processes in chloro-organic manufacture to capture waste flows, which are then treated through a process of incineration. The same study comments on incineration processes for waste contaminated with hexachlorobenzene (HCB) and hexachlorobutadiene (HCBD) with presence in exhaust gases not detecting HCB or HCBD above the limits of detection (detection limits ranging from about 9 to 10 µg/kg). 118. In other global regions, the potential issue of unintentional releases of HCBD is less clear. During the presentations made at the 11th POPRC, Hu (2015) provided details that illustrate that carbon tetrachloride remains globally important, particularly as an intermediate feedstock in the manufacture of HFCs used as refrigerant gases, but also potentially as blowing agents for foams. A study by Zhang et al. (2015) in China also highlighted the potential generation of HCBD as a contaminant in residues of carbon tetrachloride from the manufacture of chloromethanes. While it is unclear how the quantities generated were processed (incineration, landfill, recycled as feedstock for HFCs), this highlights a potential issue that warrants further investigation. 119. An inclusion of HCBD under Annex C of the Stockholm Convention would also trigger the requirements of Article 5 of the Convention (measures to reduce or eliminate releases from unintentional production) and establish the goal of continuing minimization and, where feasible, ultimate elimination of HCBD releases. This would include an obligation to promote and require the use best available techniques (BAT) for new HCBD sources if a Party has identified them as warranting such action in its action plan. Furthermore, parties shall promote the use of best environmental practices (BEP) for new HCBD sources, and promote the use of BAT/BEP for exisitng source of HCBD. Where production processes and supply chains are complex it would also mean closer tracking and monitoring of HCBD emissions from key points in the supply chain including

23 UNEP/POPS/POPRC.12/INF/12 production of chloromethanes, production of carbon tetrachloride, use of carbon tetrachloride in HFC feedstocks, and greater understanding of the secondary sources mentioned. 4.2 Conclusion 120. The evidence reviewed suggests that the potential generation and release of HCBD from unintentional sources has declined from a number of key sources since the 1970s. However the existing and remaining sources are still important to the generation and release of HCBD. In some cases while it is possible to suggest that significant sources still exist, the full quantification and management of these releases is still not fully understood. Application of BAT/ BEP would likely have strong beneficial effects to further control and reduce emissions but would bring additional costs for those parties not currently applying BAT/BEP. There would also be additional costs for industrial monitoring but these costs may be partly off-set by overlap with existing monitoring carried out at industrial plants for existing Annex C substances. The information reviewed and provided here includes some new data on potential emissions and monitoring at industrial plants that produces HCBD as a by-product of other production. This information, which has been been supplemented with information from the risk management evaluation dossier where necessary, highlights that there may still be significant releases of HCBD globally, particularly for chloro-organic manufacture and in countries where BAT/ BEP are not fully applied.

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