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Crystalline Silica, Cristobalite (CAS No Crystalline Silica, Quartz (CAS No. 14808-60-7) Crystalline Silica, Cristobalite (CAS No. 14464-46-1) Crystalline Silica, Tridymite (CAS No. 15468-32-3) Diatomaceous earth (CAS No. 61790-53-2) This dossier on crystalline silica, quartz, cristobalite and tridymite and diatomaceous earth presents the most critical studies pertinent to the risk assessment of these substances in their use in drilling muds and cement additives. 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). For the purpose of this dossier, crystalline silica, quartz (CAS No. 14808-60-7) has been reviewed as representative of crystalline silica cristobalite and tridymite. Crystalline silica, quartz is also considered representative of diatomaceous earth, as they both consist mainly of silicon dioxide. Screening Assessment Conclusion – Crystalline silica, quartz, cristobalite and tridymite and diatomaceous earth are classified as tier 1 chemicals and require a hazard assessment only. 1 BACKGROUND Crystalline silica is a common mineral found in the earth's crust. Materials like sand, stone, concrete and mortar contain crystalline silica. It is also used to make products such as glass, pottery, ceramics, bricks and artificial stone. Silica, in the form of sand, is used as the main ingredient in sand casting for the manufacture of metallic components in engineering and other applications. The high melting point of silica enables it to be used in such applications. Crystalline silica is used in hydraulic fracturing of formations which contain tight oil and shale gas. 2 CHEMICAL NAME AND IDENTIFICATION Chemical Name (IUPAC): dioxosilane CAS RN: 14808-60-7 Molecular formula: SiO2 Molecular weight: 60.084 g/mol Revision date: March 2021 1 Synonyms: Cristobalite, Dioxide, Silicon 3 PHYSICO-CHEMICAL PROPERTIES Silica is an off-white granule that occurs naturally in various crystalline and amorphous or other non- crystalline forms. Crystalline silica is characterised by silicon dioxide (SiO2) molecules oriented in fixed, periodic patterns to form stable crystals. The primary crystalline form of silica is quartz. Other crystalline forms of silica include cristobalite, tripoli and tridymite. Particle size is a key determinate of silica toxicity, since toxicity is restricted to particles that are small enough to be deposited into the target regions of the respiratory tract. See attached OECD-SIDS Initial Targeted Assessment Profile on Quartz and Cristobalite, SIAM 32, 19- 21 April 2011. 4 DOMESTIC AND INTERNATIONAL REGULATORY INFORMATION A review of international and national environmental regulatory information was undertaken (Table 1). 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 crystalline silica, quartz. Based on an assessment of environmental hazards, NICNAS identified members of this group (crystalline silica, quartz, cristobalite and tridymite) as a chemical of low concern to the environment (NICNAS, 2017). Chemicals of low concern are unlikely to have adverse environmental effects if they are released to the environment from coal seam gas operations. Table 1 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 Crystalline silica is characterised by silicon dioxide (SiO2) molecules oriented in fixed, periodic patterns to form stable crystals. The primary crystalline form of silica is quartz. It is a stable solid under typical environmental conditions. It will not biodegrade, bioaccumulate, nor will it sorb to sediments or soils. Revision date: March 2021 2 B. Biodegradation No data are available. Based on the crystalline form of the substance it in not expected to biodegrade. C. Environmental Distribution No experimental data are available for crystalline silica. As a stable inorganic solid, it is not soluble in water and it will not sorb to soils or sediment. D. Bioaccumulation There are no bioaccumulation studies on crystalline silica. 6 ENVIRONMENTAL EFFECTS SUMMARY A. Summary Although no data are available, crystalline silica is expected to exhibit low acute toxicity to aquatic organisms. B. Aquatic Toxicity No terrestrial toxicity data were available. C. Terrestrial Toxicity No terrestrial toxicity data were 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, 2008a). Crystalline silica is an inorganic mineral. Thus, biodegradation is not applicable to this substance. For the purposes of this PBT assessment, the persistent criteria are not considered applicable to crystalline silica. As an inorganic complex it is not expected to bioaccumulate. Thus, crystalline silica does not meet the screening criteria for bioaccumulation. Crystalline silica is not expected to cause adverse effects in environmental receptors. Thus, this substance does not meet the screening criteria for toxicity. Therefore, crystalline silica is not a PBT substance. Revision date: March 2021 3 B. Other Characteristics of Concern No other characteristics of concern were identified for crystalline silica, quartz. Revision date: March 2021 4 8 SCREENING ASSESSMENT Chemical Databases of Concern Bioaccumulative Persistence Assessment Step Toxicity Assessment Step Assessment Step Assessment Step Overall PBT Risk Assessment Actions Chemical Name CAS No. Listed as a COC Identified as Assessment 1 P criteria Other P T criteria Acute Chronic Required3 on relevant Polymer of Low B criteria fulfilled? fulfilled? Concerns fulfilled? Toxicity 2 Toxicity2 databases? Concern Crystalline silica, quartz 14808-60-7 Not a PBT No No NA No No No 1 1 1 Crystalline Silica, cristobalite 14464-46-1 Not a PBT No No NA No No No 1 1 1 Crystalline silica, tridymite 15468-32-3 Not a PBT No No NA No No No 1 1 1 Diatomaceous earth 61790-53-2 Not a PBT No No NA No No No 1 1 1 Footnotes: 1 - PBT Assessment based on PBT Framework. 2 - Acute and chronic aquatic toxicity evaluated consistent with assessment criteria (see Framework). 3 – Tier 1 – Hazard Assessment only. Notes: NA = not applicable PBT = Persistent, Bioaccumulative and Toxic B = bioaccumulative P = persistent T = toxic Revision date: March 2021 5 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. ECHA. ECHA REACH database: http://echa.europa.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. 25:1-5. NICNAS. (2017). National assessment of chemicals associated with coal seam gas extraction in Australia,Technical report number 14 - 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. B. Abbreviations and Acronyms AICS Australian Inventory of Chemical Substances COC constituent of concern DEWHA Department of the Environment, Water, Heritage and the Arts ECHA European Chemicals Agency EU European Union IUPAC International Union of Pure and Applied Chemistry PBT Persistent, Bioaccumulative and Toxic REACH Registration, Evaluation, Authorisation and Restriction of Chemicals SGG Synthetic Greenhouse Gases Revision date: March 2021 6 Appendix OECD-SIDS Initial Targeted Assessment Profile on Quartz and Cristobalite, SIAM 32, 19-21 April 2011 https://hpvchemicals.oecd.org/ui/handler.axd?id=b68bb357-e6dd-4db9-b05c-8148223fc0ff Revision date: February 2021 7 SIAM 32, 19-21 April 2011 CAN INITIAL TARGETED ASSESSMENT PROFILE (Human Health) CAS No. Quartz: CAS RN 14808-60-7 Cristobalite: CAS RN 14464-46-1 Chemical Name Quartz and Cristobalite Molecular Formula: SiO2 Structural Formula Unit Cell: Trigonal symmetry Unit Cell: Tetragonal symmetry Quartz: CAS RN 14808-60-7 Cristobalite: CAS RN 14464-46-1 SUMMARY CONCLUSIONS OF THE TARGETED ASSESSMENT NOTE: The present assessment is targeted to address the following human health endpoints: repeated dose
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