Magnesium hydroxide sulfate (Mg6(OH)10(SO4)), hydrate (1:3)

Endpoint summary

Additional information

Aquatic Toxicity (Ecotoxicological information)

Testing was carried out on the following endpoints using the following guidelines:

Short-term toxicity to fish - OECD Guidelines for Testing of Chemicals (1992) No 203, "Fish, Acute Toxicity Test" referenced as Method C.1 of Commission Directive 92/69/EEC (which constitutes Annex V of Council Directive 67/548/EEC).

Short-term toxicity to aquatic invertebrates - OECD Guidelines for Testing of Chemicals (April 2004) No 202, "Daphnia sp, Acute Immobilisation Test" referenced as Method C.2 of Commission Directive 92/69/EEC (which constitutes Annex V of Council Directive 67/548/EEC).

Short-term toxicity to aquatic algae and cyanobacteria - OECD Guidelines for Testing of Chemicals (1984) No 201, "Alga, Growth Inhibition Test" referenced as Method C.3 of Commission Directive 92/69/EEC (which constitutes Annex V of Council Directive 67/548/EEC).

Short-term toxicity to microorganisms - OECD Guidelines for Testing of Chemicals (1984) No 209 "Activated Sludge, Respiration Inhibition Test", EEC Commission Directive 87/302/EEC and US EPA Draft Ecological Effects Test Guidelines OPPTS 850.6800.

The results of these studies are detailed below:

Short-term toxicity to fish

The 96-Hour LC₅₀ based on nominal test concentrations was greater than 38 mg/l and correspondingly the No Observed Effect Concentration was 38 mg/l. Analysis of the test preparations at 0, 24 and 96 hours showed measured test concentrations to range from 86% to 110% of nominal and so the results are based on nominal test concentrations only.

Short-term toxicity to aquatic invertebrates

The 48-Hour EC₅₀ for the test material to Daphnia magna based on nominal test concentrations was greater than 38 mg/l and correspondingly the No Observed Effect Concentration was 38 mg/l. Analysis of the test preparations at 0 and 48 hours showed measured test concentrations to range from 95% to 115% of nominal and so the results are based on nominal test concentrations only.

The 48-Hour EC₅₀ for the reference material to Daphnia magna based on nominal concentrations was 0.60 mg/l with 95% confidence limits of 0.53 – 0.68 mg/l. The No Observed Effect Concentration was 0.32 mg/l.

Short-term toxicity to aquatic algae and cyanobacteria

Exposure of Scenedesmus subspicatus to the test material gave an E_bC₅₀ (72 h) value of 4.1 mg/l and an E_rC₅₀ (0 - 72 h) value of 10 mg/l*. The No Observed Effect Concentration was 2.35 mg/l. The analytical procedure used for the quantification of dissolved test material concentrations in the test preparations was based on the determination of magnesium by ion chromatography as the test material predominately existed as a magnesium hydroxide complex.  Analysis of the test preparations at 0 hours showed measured test concentrations to range from 1.58 to 9.89 mg/l. Analysis of the test preparations 72 hours showed measured concentrations to range from 1.85 to 18.3 mg/l.

During validation of the method of analysis it was evident that a significant amount of magnesium was present in the test medium and as such all test sample concentrations were corrected for the concentration found in the control samples. Furthermore it was also observed that an increase in magnesium concentration occurred over the test period which was considered to be due to the chelating properties of the EDTA present in the test medium (Vogel 5^th Edition). Whilst a significant proportion of the magnesium present at 0 hours was bound to the EDTA and hence undetected the decrease in pH of the test cultures over the test period was considered to reduce the chelating properties of the EDTA resulting in a much greater proportion of the magnesium present being available for detection at 72 hours.

Additional studies conducted on this test material (Acute Toxicity to Rainbow Trout and Acute Toxicity to Daphnia magna (IUCLID 5 sections 6.1.1 and 6.1.3 respectively) using both dechlorinated tap water and reconstituted water in which no EDTA was present did not show such an effect. As such an apparent increase in test material concentrations was observed over the 72-Hour test period. Given this increase in measured test concentrations it was considered justifiable to base the results on the 0-Hour measured test concentrations only in order to give a "worst case" analysis of the data.

Short-term toxicity to microorganisms

In the test vessels prepared at a concentration in excess of the test material solubility, the effect of the test material on the respiration of activated sewage sludge gave a 3‑Hour EC₅₀ of greater than 1000 mg/l. The No Observed Effect Concentration (NOEC) after 3 hours exposure was1000 mg/l. In the test vessel prepared at a concentration of 34 mg/l, the effect of the test material on the respiration of activated sewage sludge gave a 3‑Hour EC₅₀ of greater than 34 mg/l. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 34mg/l. The reference material gave a 3-Hour EC₅₀ value of 7.6 mg/l, 95% confidence limits
6.0 – 9.7 mg/l.

The above studies have all been ranked reliability 1 according to the Klimisch system. This ranking was deemed appropriate because the studies were conducted to GLP and in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.