Calcium magnesium strontium carbonate hydroxide phosphate (4.3-4.7 : 0.1-0.3: 0.2-0.5 : 0.3-0.5 : 0.2-0.6 : 3)

Toxicity to aquatic algae and cyanobacteria

Description of key information

EC50 (72hr) > 100 mg/l (nominal)

EC50 (72hr) > 1.56 mg/l (measured)

Key value for chemical safety assessment

EC50 for freshwater algae:

100 mg/L

Additional information

The toxic potential of the substance is evaluated by considering data on similar substances. Justification for Read Across is given in Section 13 of IUCLID.

The toxic potential of the substances to aquatic algae was evaluated according to the OECD Guideline 201. Pseudokirchneriella subcapitata was exposed to Similar Substance 05 at 0, 4, 9, 21, 45, and 100 mg/l (nominal) and to Similar Substance 06 at 0.3, 1, 3.1, 9.8, 31.3, and 100 mg/l for 72 hours. The concentration of the test substances was analyzed using ICP at the beginning (0 hour) and the end (72 hours) of the test. Analytical results indicated that the test substances were sparsely soluble in water. Morphological changes of algal cells were observed including expansion, aggregation, atrophy, and decoloration at 72 hours after exposure. Based on average specific growth rate and yield:

EC50 (72hr) > 100 mg/l (nominal) - Similar Substance 05 and Similar Substance 06

EC50 (72hr) > 4.4 mg/l (measured) - Similar Substance 06

EC50 (72hr) > 1.56 mg/l (measured) - Similar Substance 05

Pacholski (2009) conducted a standard 72-h algal growth test with the alga Pseudokirchneriella subcapitata; additional testing details and endpoint calculations were provided in HydroQual (2009; 2013 pers. comm.). Control performance was acceptable, and the results were corrected for the control responses. The 72-h IC10 was 36000 µg/l and the IC20 was 47000 µg/l; the IC10 was used for the Chronic Effect Benchmarl (CEB) determination. The algae demonstrated a hormetic response, with growth stimulation occurring at strontium concentrations up to 23000 µg/l, but inhibition of growth at higher concentrationstions. Magnesium toxicity was also determined after a 72 -hr exposure of Chlorella sp. to 3 -1200 mg/l of magnesium sulfate.

Based on growth rate the following rates were determined:

IC50 (72h) = 1215 mg/l - Mg(measured), IC50 (72h) = 6014 mg/l -MgSO₄(measured)

IC10 (72h) = 43 mg/l - Mg(measured), IC10 (72h) = 213 mg/l - MgSO₄(measured)

The substance is also expected to have an EC50 > 100 mg/l (nominal) or above the limit of solubility. The substance is poorly soluble in water rendering its bioavailability lower and thus an exposure of the aquatic invertebrates is not expected.

HydroQual (HydroQual Laboratories Ltd.). 2009. Aquatic Toxicity Assessment on Strontium. Reported prepared for Golder Associates Ltd., Calgary, AB, by HydroQual Laboratories Ltd., Calgary, AB. May 8, 2009.

Pacholski, L. 2009. Toxicity of Stable Strontium in Surface Freshwaters of the Oil Sands Region in Alberta, Canada – Deriving an Aquatic Guideline and Refined Chronic Effects Benchmark. University of Ulster, Londonderry, Northern Ireland.