Background document for sodium dichromate

Transcription

1 1 June 2009 Background document for sodium dichromate Document developed in the context of ECHA s first Recommendation for the inclusion of substances in Annex XIV 1. Identity of the substance Chemical name: sodium dichromate EC Number: CAS Number: (anhydrous) and (dihydrate) IUPAC Name: sodium dichromate 2. Background information 2.1. Intrinsic properties Sodium dichromate was identified as a Substance of Very High Concern (SVHC) pursuant to Article 57(a), (b), (c) as it is classified as Carcinogenic Category 2 1, Mutagenic, Category 2 and Toxic for reproduction, Category 2 and was therefore included in the candidate list for authorisation following ECHA s decision ED/67/2008 on 28 October Imports, exports, manufacture and uses Volume(s), imports/exports According to the Risk Assessment Report (RAR), sodium dichromate was manufactured in quantities of 110,000 t by 3 companies in the EU in 1997 (EC, 2005). Taking into account export and import, the amount of Na 2 Cr 2 O 7 used in the EU was estimated to be 25,000 t (77 % net export). Updated information reveals that EU manufacturing as well as export have been reduced significantly. At the same time the volume used in the EU has increased to over twice as much as in 1997 (Entec, 2008). In conclusion, the volume used in the EU is less than 100,000 t/y. 1 This document refers (here and in its other parts) to classification in accordance with Directive 67/548/EEC to keep the references in line with the entry in the published Candidate list. ECHA will update the Candidate list to follow the CLP Regulation ((EC) No 1272/2008) in future. 1

2 Manufacture and uses Manufacture and releases from manufacture There is one manufacturer and one major importer in the EU. Manufacturing takes place solely as a solution (no dermal or inhalation exposure during production) (Entec, 2008). Releases for total chromium due to production and processing from the one site producing sodium dichromate were retrieved from EPER database and given as 1.8 t/y to water and 2.93 t/y to air for 2007 (Entec, 2008) Uses and releases from uses The volume supplied to the EU market is used as indicated in Table 1. Table 1: Uses of Na 2 Cr 2 O 7 in EU according to Entec (2008) * % Uses of Na 2 Cr 2 O 7 intermediate/non-intermediate use 90 Manufacture of Cr (III) oxide intermediate < 7 Tanning salts intermediate ~ 3 Metal finishing non-intermediate < 1 Cr (VI) pigments intermediate ~ 0.8 Production of chromium metal intermediate << 1 Anticorrosive additive in coating non-intermediate << 1 Other uses - wood preservative - mordant for wool dye - montan wax production - vitamin K production - cleaning agent (covered by Directive 98/8/EC) non-intermediate intermediate intermediate non-intermediate * Export is not considered in presented mass balance. Since the exact tonnages of minor uses are not known, the total mass balance is above 100 %. ** Manufacture of montan wax may be a more significant use Intermediate use of Na 2 Cr 2 O 7 is for the manufacture of Cr (III) oxide and of tanning salts. The latter are made by reduction of Na 2 Cr 2 O 7 to chromium (III) sulphate. Cr (VI) pigments are made from Na 2 Cr 2 O 7 by attaching various cations to the chromate thereby determining their application (EC, 2005). For example, lead chromate is used in paints and as colorant in plastics. Zinc chromate is used in anticorrosive paints in aircraft industry. Strontium and barium chromate are mainly used for fireworks (EC, 2005). About 0.8 % of Na 2 Cr 2 O 7 is used for the manufacture of chromium metal by exothermic redox reaction with aluminium (Entec, 2008). A further intermediate use of Na 2 Cr 2 O 7 is in the production of montan wax, which is used in food packaging. Information on the exact use of Na 2 Cr 2 O 7 in the process is 2 Data given here refer to releases to the environment of all chromium compounds from production and processing on that one site, i.e. it is not possible to identify releases coming from the production of sodium dichromate only. 2

3 not available, but it is believed that Na 2 Cr 2 O 7 acts as reducing agent (Entec, 2008). The process is described as enclosed where no significant releases are expected (EC, 2005). Recent information suggests that, beside the montan wax manufacturer already identified (EC, 2005), there might be at least one other company manufacturing montan wax. However, involved tonnages account only for a small percentage of total consumption of Na 2 Cr 2 O 7 (HSE, 2007; Entec, 2008). A minor intermediate use (<< 1 %) is as oxidant in the manufacture of Vitamin K which takes place by oxidation of 2-methylnaphthalene with a solution of sodium dichromate acidified with sulphuric acid. Sodium dichromate is reduced to Cr (III) sulphate, which is sold to be used as tanning salt (Entec, 2008). Non-intermediate use of Na 2 Cr 2 O 7 occurs in metal surface treatment (e.g. passivation, electroplating) to achieve a certain finish or prevent corrosion, especially in the aeronautics and metal packaging (canning) industry (Entec, 2008). Metal finishing covers a wide range of varied and complex processes carried out by industry and involves both chemical and physical processes. There is however no information available about releases from the use of Na 2 Cr 2 O 7 in metal finishing (Entec, 2008). Aeronautics industry Consultation with the industry revealed that many of the parts that are used to make aircrafts are made by SMEs and are supplied to the large engine and airframe manufacturers. Therefore processes using sodium dichromate are to a large extent used by small to medium sized specialist engineering companies. Large parts of the airframe will be made by the aircraft manufacturers so the substance is also used by these large companies. No information on the amounts used in different processes by the aerospace industry is available (Entec, 2008). Metal packaging The main process involved in steel packaging is tinplate passivation. It occurs only in a few large plants in the EU. The process of passivation is used to make a stable steel-tin-lacquer system thereby preventing migration of metal components into the canned product (Entec 2008). There are other non-intermediate uses of Na 2 Cr 2 O 7, e.g. as a mordant for wool dye (Na 2 Cr 2 O 7 added to fix dyes to wool and is thereby reduced to Cr (III)), use in industrial cleaning ( de-smut ), and cleaning of laboratory glassware. No further information on tonnages involved and respective releases could be obtained. However, as these uses are all minor (in total << 1 %), potential releases are assumed to be minor as well. Uses as biocide are not within the scope of Title VII of REACH. The use of chromium as wood preservative is covered by the Biocidal Products Directive (98/8/EC), and wood preservatives containing Na 2 Cr 2 O 7 have been phased out by 01/09/2006 (Commission Regulation (EC) No 1048/2005). 3

4 Geographical distribution and conclusions in terms of (organisation and communication in) supply chain There is one producer within the EU situated in the United Kingdom (Entec, 2008). The major importer is based in Germany (Entec, 2008). There is no specific information available regarding the geographical distribution for the non-intermediate uses of Na 2 Cr 2 O 7. Metal finishing as the main non-intermediate use (about 3 % of total tonnage) takes place mainly at SMEs and some larger industrial settings. Although the number and geographical distribution are unknown, it can be assumed that they are widely distributed within the EU Availability of information on alternatives 3 Aeronautics industry The aeronautics industry has funded a number of research projects on the replacement of hexavalent chromium (rather than sodium dichromate per se; Entec 2008). There are possible alternatives for a number of different uses, but none are presently known to fulfil the technical and airworthiness safety that is required for aircraft. In addition, in many cases where possible alternatives could be identified, these could only be used for the production of new aircraft as maintenance of existing aircraft requires the use of the substances that are currently used because of compatibility with existing materials. Metal packaging There are signs that the industry may be moving away from chromium (VI) to either chromium (III) or chrome-free alternatives (Entec, 2008). Electrolytic chromium/chromium oxide coated steel (ECCS) has been developed as an alternative to tinplate. In that technique, chromium plating of steel strip (known as blackplate) is performed electrolytically in chromic acid baths. The coating obtained consists of chromium metal and chromium oxides. However, ECCS can only be used with an additional organic coating. It is less weldable than tinplate and, therefore, the use of ECCS is limited to about 20% of the total amount of steel for packaging (Entec, 2008) Existing specific Community legislation relevant for possible exemption No data available Any other relevant information (e.g. for priority setting) No data available. 3 Please note that this information was not used for prioritisation. 4

5 3. Conclusions and justification 3.1. Prioritisation The volume used in the EU is less than 100,000 t/a. Approximately 97% of the sodium dichromate supplied to the EU market is used as an intermediate for synthesis of chromium (III) compounds. Beside some minor non-intermediate uses (in total <<1%), the main non-intermediate use is in metal finishing in the aeronautics and metal packaging (canning) industry. The volume of sodium dichromate supplied to metal finishing is high (< 3,000 t/y). Metal finishing takes place in a larger number of SMEs and in some industrial settings. The use of sodium dichromate in metal finishing can therefore be considered as widespread. However, as no information is available about releases from that use, a conclusion whether the use of sodium dichromate in metal finishing must be considered as wide dispersive cannot be drawn without supplementary information becoming available. The regulatory effectiveness of subjecting the use of the sodium dichromate salt alone to the authorisation requirement can be considered questionable because it might in many cases be easy to bypass the authorisation requirement by replacing the sodium salt by another hexavalent chromium compound with a similar hazard potential. Therefore, ECHA recommends not to prioritise sodium dichromate for inclusion in Annex XIV Recommendation for Annex XIV entry As the substance was not prioritised for inclusion in Annex XIV no recommendation for its Annex XIV entry has been developed. 4. References EC (2005): European Union Risk Assessment Report: chromium trioxide, sodium chromate, sodium dichromate, ammonium dichromate, potassium dichromate. 3 rd Priority List, Volume 53. European Commission, Joint Research Centre. Entec (2008): Data on manufacture, import, export, uses and releases of sodium dichromate as well as information on potential alternatives to its use. Report prepared for ECHA. HSE (2007): Human health risk reduction strategy for chromates. Prepared by Health and Safety Executive, UK. 5