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EC number: 208-915-9 | CAS number: 546-93-0
Short-term toxicity to aquatic invertebrates
Administrative data
Link to relevant study record(s)
Description of key information
No studies on the short-term toxicity of magnesium carbonate to aquatic invertebrates are available and further testing is scientifically unjustified.
The key study was conducted on an analogous substance and assesses the short term toxicity of magnesium chloride hexahydrate to Daphnia magna. The 48 h LC50 for magnesium was 322 mg Mg/L (with food) which demonstrates that magnesium and magnesium chloride hexahydrate are not acutely toxic to invertebrates at the concentrations tested. The results from this study can be read across to magnesium carbonate and hence the equivalent LC50 value for magnesium carbonate is equal to 1127 mg/L (with food).
Key value for chemical safety assessment
Additional information
Rationale for read across:
Magnesium chloride hexahydrate is significantly more soluble in water than magnesium carbonate and therefore represents the worst case in terms of bioavailability in natural waters. Although magnesium carbonate is less soluble, both magnesium chloride hexahydrate and magnesium carbonate are expected to dissociate to their ionic forms in water and therefore the toxicity results can be read across.
The key study (Biesinger and Christensen, 1972) assessed the acute toxicity of magnesium chloride hexahydrate to Daphnia magna at various different concentrations. No adverse effects were reported in the study and the 48 h LC50 for magnesium was 322 mg Mg/L (with food). The equivalent LC50 value for magnesium carbonate would be equal to 1127 mg/L.
This result is supported by the study by Mount et al (1997) which assessed the acute toxicity of magnesium chloride to Daphnia magna at various different concentrations. Based on the 48 h LC50 value for magnesium chloride, the equivalent LC50 value for magnesium carbonate would be equal to 1176 mg/L.
The concentration of magnesium carbonate that might cause acute toxicity is therefore greater than the maximum solubility of magnesium carbonate in water (110 mg/L at 20 °C).
Magnesium is naturally abundant in the environment meaning that aquatic organisms are constantly exposed to magnesium without suffering from any adverse or detrimental effects. Indeed, each of the Mg2+, Cl- and CO3^2- ions are ubiquitous in the aquatic environment. Magnesium is a major contributor to water hardness. Water from areas rich in magnesium-containing rocks may contain magnesium in the concentration range 10 to 50 mg/L. The sulfates and chlorides of magnesium are very soluble, and water in contact with such deposits may contain several hundred milligrams of magnesium per litre.
The abundance of magnesium in the aquatic environment and the low toxicity demonstrated by the presented studies demonstrate that any further testing is scientifically unjustified.
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