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EC number: 231-448-7 | CAS number: 7558-79-4
Table1 Oxygen Consumption Rates and Percentage Inhibition Values after 3 Hours Contact Time
[Increase in respiration rate as compared to controls]
R1– R2= Replicates 1 to 2
Table2 pH Values of the Test Preparations at the Start and End of the Exposure Period
Table3 Observations on the Test Preparations Throughout the Test Period
Observations on Test Preparations
Dark brown dispersion
Clear colourless solution, no undissolved test item visible*
Dark brown dispersion, no undissolved test item visible
Cloudy homogenous dispersion, no undissolved test item visible*
Dark brown dispersion, no undissolved reference item visible
*Observations made prior to the addition of synthetic sewage and activated sewage sludge
Litchfield, J T and Wilcoxon, F (1949) A Simplified Method of Evaluating Dose-Effect Experints. J Pharmacol Exp Ther96, 99-113.
Xlfit, ID Business Solutions Ltd.
A study was perford to assess the effect of the test item on the respiration of activated sewage sludge. Thethod followed that described in the OECD Guidelines for Testing of Chemicals (1984) No 209 "Activated Sludge, Respiration Inhibition Test", Method C.11 of Commission Regulation (EC) No. 440/2008 and US EPA Draft Ecological Effects Test Guidelines OPPTS 850.6800.
Activated sewage sludge was exposed to an aqueous solution of the test item at concentrations of 10, 32, 100, 320 and 1000 mg/l for a period of 3 hours at a temperature of 21 ± 1°C with the addition of a synthetic sewage as a respiratory substrate.
The rate of respiration was determined after 3 hours contact tiand compared to data for the control and a reference item, 3,5-dichlorophenol.
The effect of the test item on the respiration of activated sewage sludge gave a 3-Hour EC50of greater than 1000 mg/l. The No
No Observed Effect Concentration (NOEC) after 3 hours exposure was1000mg/l.
It was considered unnecessary and unrealistic to test at concentrations in excess of 1000 mg/l.
The reference item gave a 3-Hour EC50value of 7.9 mg/l, 95% confidence limits 6.2 - 10 mg/l.
The EC50 was estimated to be greater than 1000 mg/L for disodium hydrogen phosphate as found in the source study performed with dipotassium hydrogen phosphate. As explained in the justification for type of information, the differences in molecular structure between disodium hydrogen phosphate and dipotassium hydrogen phosphate are unlikely to lead to differences in the EC50 that are higher than the typical experimental error of the test method.
One key study to assess the toxicity of disodium hydrogenorthophosphate to STP microorganisms exists, this study is conducted on an analogous substance. The study was performed under GLP conditions and to an appropriate guideline (OECD 209).The additional supporting data provided were not considered to be adequate or reliable to fulfil neither the guideline nor the regulatory requirements. Further, there is no evidence within this data to suggest that essential validity criteria are met. A number of literature papers relating to bioavailability and tolerance of inorganic phosphates in aquatic ecosystems are included in Section 6.6 to support the conclusions made in this endpoint.
The effect of the test item on the respiration of activated sewage sludge micro-organisms gave a 3-Hour EC50 of greater than 1000 mg/l. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 1000 mg/l.
In accordance with REACH Annex XI, Section 1.5, of Regulation (EC) No. 1907/2006 (REACH) the standard testing regime may be adapted in cases where a grouping or read-across approach has been applied.
The similarities may be based on:
1. A common functional group
2. The common precursors and/or the likelihood of common breakdown products via physical or biological processes, which result in structurally similar chemicals; or
3. A constant pattern in the changing of the potency of the properties across the category
The source chemical and disodium hydrogenorthophosphate have the following similarities:
1. Both substances are inorganic salts of a monovalent cation from Group 1A of the periodic table, sodium or potassium, and phosphoric acid. Thus, they all share the Na+ or K+ cation and the PO43- anion as common functional groups.
2. All members of the group will ultimately dissociate into the common breakdown products of the Na+ or K+ cations and the PO43- anion.
3. Sodium and potassium orthophosphates have been shown to have a similar toxicological profile and physicochemical nature and therefore this data is considered to be adequate and reliable for use in read-across.
Any further testing would not be scientifically justified as all substances will dissociate to their anionic and cationic forms in natural waters and these ions (Na+, K+ and PO43-) are all ubiquitous and are not considered to pose a risk of ecotoxicity.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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