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SODIUM ACETATE
This dossier on sodium acetate presents the most critical studies pertinent to the risk assessment of sodium acetate in its use in coal seam gas extraction activities. This dossier does not represent an exhaustive or critical review of all available data. The majority of information presented in this dossier was obtained from the ECHA database that provides information on chemicals that have been registered under the EU REACH (ECHA). Where possible, study quality was evaluated using the Klimisch scoring system (Klimisch et al. , 1997).
Screening Assessment Conclusion – Sodium acetate is classified as a tier 1 chemical and requires a hazard assessment only.
1 BACKGROUND
Sodium acetate is the salt of acetic acid, and acetic acid is widely used in the coal seam gas industry as a pH adjuster and for iron control (DoEE, 2017a).
Sodium acetate disassociates in water to form sodium ions (Na+) and acetate (H 3 C2O 2 - ) ions. Both of these chemical species are naturally occurring and ubiquitous in the aquatic environment. The acetate ion is readily biodegradable, is not expected to bioaccumulate, and has a low potential to adsorb to soil or sediment. The acetate ion is of low acute toxicity concern to aquatic organisms.
2 CHEMICAL NAME AND IDENTIFICATION
Chemical Name (IUPAC): Sodium acetate
CAS RN: 127-09-
Molecular formula: C 2 H 4 O 2 .Na
Molecular weight: 82.03 g/mol
Synonyms: Acetic acid, sodium salt, Sodium acetate anhydrous, Acetic acid sodium salt
3 PHYSICO-CHEMICAL PROPERTIES
Key physical and chemical properties for the substance are shown in Table 1.
Table 1 Overview of the Physico-chemical Properties of Sodium Acetate
Property Value Klimisch score
Reference
Physical state at 20oC and 101.3 kPa crystalline or white granular powder
1 ECHA
Melting Point 324 °C @ 101.3 kPa 1 ECHA Boiling Point Not applicable as substance is solid.
Density 1530 kg/m^3 @ 20 °C 1 ECHA
Property Value Klimisch score
Reference
Vapour pressure Not applicable - ECHA Partition Coefficient (log Pow) -3.72 2 ECHA Water Solubility 1,250 g/L @ 25 °C 1 ECHA Dissociation Constant (pKa) 4.756 4 ECHA
Sodium acetate disassociates in water to form sodium ions (Na+) and acetate (H 3 C2O 2 - ) ions. Acetate is ubiquitous in natural water and acts as a key nutrient, supplying energy to heterotrophic algae under aerobic conditions. Acetate is also formed by anaerobic bacteria through natural fermentation processes as a source of energy. Sodium ions are similarly naturally ubiquitous in the environment (DoEE, 2017a).
4 DOMESTIC AND INTERNATIONAL REGULATORY INFORMATION
A review of international and national environmental regulatory information was undertaken (Table 2). This chemical is listed on the Australian Inventory of Chemical Substances – AICS (Inventory). No conditions for its use were identified. No specific environmental regulatory controls or concerns were identified within Australia and internationally for sodium acetate.
Based on an assessment of hazards, NICNAS identified the substance as a chemical of low concern to human health and the environment (NICNAS, 2017 and DoEE, 2017b). Chemicals of low concern are considered to have a low likelihood of causing adverse human health effects should an exposure occur and are unlikely to have adverse environmental effects if they are released to the environment from coal seam gas operations.
Table 2 Existing International Controls
Convention, Protocol or other international control Listed Yes or No? Montreal Protocol No Synthetic Greenhouse Gases (SGG) No Rotterdam Convention No Stockholm Convention No REACH (Substances of Very High Concern) No United States Endocrine Disrupter Screening Program No European Commission Endocrine Disruptors Strategy No
5 ENVIRONMENTAL FATE SUMMARY
A. Summary
Sodium acetate disassociates in water to form sodium ions (Na+) and acetate (H 3 C2O 2 - ) ions. Both of these chemical species are naturally occurring and ubiquitous in the aquatic environment. The acetate ion is readily biodegradable, is not expected to bioaccumulate, and has a low potential to adsorb to soil or sediment.
B. Aquatic Toxicity
Acute
The aquatic toxicity data for sodium acetate are presented in Table 3.
Table 3. Acute Aquatic Toxicity Studies on Sodium Acetate
Test Species Endpoint Results (mg/L) Klimisch Score Reference
Brachydanio rerio 96h-LC50 > 100 mg/L 2 ECHA
Daphnia magna EC50 (48h) >385.60 2 ECHA
Acartia tonsa LC50 (48h) 2075.20 2 ECHA
Algae and cyanobacteria (unspecified)^1
EC50 (unspecified duration)
417.92 2 ECHA
1 – testing read across from potassium acetate
Chronic Studies
No chronic data are available.
C. Terrestrial Toxicity
No studies are available.
7 CATEGORISATION AND OTHER CHARACTERISTICS OF CONCERN
A. PBT Categorisation
The methodology for the Persistent, Bioaccumulative and Toxic (PBT) substances assessment is based on the Australian and EU REACH Criteria methodology (DEWHA, 2009; ECHA, 2008).
Sodium acetate is readily biodegradable; thus, it does not meet the screening criteria for persistence.
Bioaccumulation of sodium acetate is not expected to occur because the substance dissociates completely in aqueous media to acetate and its sodium ion. Both ions are ubiquitous in the environment. Acetate is naturally found in eukaryotic and prokaryotic cells and is involved in their biochemical pathways. The log Kow for sodium acetate is -3.72. Thus, sodium acetate does not meet the screening criteria for bioaccumulation.
The acute toxicity values for tested species are all > 1mg/L. Thus, sodium acetate does not meet the screening criteria for toxicity.
There are no chronic toxicity studies on sodium acetate. The acute E(L)C 50 values were greater than 1 mg/L. Thus, sodium acetate does not meet the criteria for toxicity.
The overall conclusion is that sodium acetate is not a PBT substance.
B. Other Characteristics of Concern
No other characteristics of concern were identified for sodium acetate
9 REFERENCES, ABBREVIATIONS AND ACRONYMS
A. References
Department of the Environment, Water, Heritage and the Arts [DEWHA] (2009). Environmental risk assessment guidance manual for industrial chemicals, Department of the Environment, Water, Heritage and the Arts, Commonwealth of Australia.
Department of the Environment and Energy (DoEE). 2017b. Environmental risks associated with surface handling of chemicals used in coal seam gas extraction in Australia, Project report prepared by the Chemicals and Biotechnology Assessments Section (CBAS), in the Chemicals and Waste Branch of the Department of the Environment and Energy as part of the National Assessment of Chemicals Associated with Coal Seam Gas Extraction in Australia, Commonwealth of Australia, Canberra.
DoEE. 2017a. Environmental risks associated with surface handling of chemicals used in coal seam gas extraction in Australia, Project report Appendices A, B, C, D, F, and G prepared by the Chemicals and Biotechnology Assessments Section (CBAS) in the Department of the Environment and Energy as part of the National Assessment of Chemicals Associated with Coal Seam Gas Extraction in Australia, Commonwealth of Australia, Canberra.
ECHA. ECHA REACH database: http://echa.euroa.eu/information-on-chemicals/registered- substances.
European Chemicals Agency (ECHA). (2008). Guidance on Information Requirements and Chemical Safety Assessment, Chapter R11: PBT Assessment, European Chemicals Agency, Helsinki, Finland.
Klimisch, H.J., Andreae, M., and Tillmann, U. (1997). A systematic approach for evaluating the quality of experimental and toxicological and ecotoxicological data. Regul. Toxicol, Pharmacol. 25:1-
NICNAS. 2017. Chemicals of low concern for human health based on an initial assessment of hazards, Project report prepared by the National Industrial Chemicals Notification and Assessment Scheme (NICNAS) as part of the National Assessment of Chemicals Associated with Coal Seam Gas Extraction in Australia, Commonwealth of Australia, Canberra.
B. Abbreviations and Acronyms
°C degrees Celsius
AICS Australian Inventory of Chemical Substances
COC constituent of concern
DEWHA Department of the Environment, Water, Heritage and the Arts
EC effective concentration
ECHA European Chemicals Agency
EU European Union
IUPAC International Union of Pure and Applied Chemistry
kPa kilopascal
LC lethal concentration
mg/L milligrams per litre
OECD Organisation for Economic Co-operation and Development
PBT Persistent Bioaccumulative Toxic
REACH Registration, Evaluation, Authorisation and Restriction of Chemicals
SGG Synthetic Greenhouse Gases
ThOD Theoretical oxygen demand
