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Short-term toxicity to aquatic invertebrates

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short-term toxicity to aquatic invertebrates
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Acceptable, well-documented publication, which meets basic scientific principles. Rationale for read-across: in the environment, lime substances rapidly dissociate or react with water. These reactions, together with the equivalent amount of hydroxyl ions set free when considering 100mg of the lime compound (hypothetic example), are illustrated below: Ca(OH)2 <-> Ca2+ + 2OH- 100 mg Ca(OH)2 or 1.35 mmol sets free 2.70 mmol OH Ca(OH)2 + 2Ca2SiO4 +9CaCO3 + 13H2O <-> 14Ca2+ + 2SiO2 + 9CO2 + 28OH- 100 mg “Reaction mass of limestone and dicalcium silicate” or 0.08 mmol sets free 2.24 mmol OH- has to be noted that CO32- is not expected to directly release two hydroxyl ions under most environmental conditions (depends on CO2 concentrations and pH) and this is therefore a worst case assumption. From these reactions it is clear that the effect of "Reaction mass of limestone and dicalcium silicate" will be caused either by calcium or hydroxyl ions. Since calcium is abundantly present in the environment and since the effect concentrations are within the same order of magnitude of its natural concentration, it can be assumed that the adverse effects are mainly caused by the pH increase caused by the hydroxyl ions. Furthermore, the above mentioned calculations show that the base equivalents are within a factor 2 for lime (chemical), hydraulic and calcium hydroxide. As such, it can be reasonably expected that the effect on pH of "Reaction mass of limestone and dicalcium silicate" is comparable to calcium hydroxide for a same application on a weight basis. Consequently, read-across from calcium hydroxide to "Reaction mass of limestone and dicalcium silicate" is justified.

Data source

Reference Type:

Materials and methods

Test guideline
no guideline followed
Principles of method if other than guideline:
Toxicity test was conducted by a standard method developed by the laboratory.`Test organisms were exposed, 96 h, to different concentrations of the test item in test solutions, prepared in natural seawater.
GLP compliance:
not specified

Test material

Details on test material:
IUPAC name: calcium dihydroxide

Sampling and analysis

Analytical monitoring:
Details on sampling:
Water quality was measured daily

Test solutions

Details on test solutions:
Test solutions were prepared for the samples in natural seawater, acclimated to 15+/-1°C, and initial water quality was measured.

Test organisms

Test organisms (species):
Crangon septemspinosa
Details on test organisms:
- Common name: sand shrimp
- Strain: Say, 1818
- Source: collected from Kouchibouguac Bay, NB, Canada

Study design

Test type:
Water media type:
Limit test:
Total exposure duration:
96 h

Test conditions

Test temperature:
15 ± 1 °C
7.68 (in control) - 12.46 (at highest dose)
Nominal and measured concentrations:
Nominal concentrations: 0, 5, 50, 500, 5000, 50000 mg/L
Details on test conditions:
Ten replicate 1 L mason jars were filled with each test concentration and acclimated to 15+/-1°C. One sand shrimp was introduced into each test vessel. The tests were checked for mortality and water quality daily.

Results and discussion

Effect concentrations
96 h
Dose descriptor:
Effect conc.:
158 mg/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
Remarks on result:
other: 95% CL: 50-500 mg/L
Details on results:
There was no mortality in control (pH 6.60-8.03) to 50 mg/L (pH 8.17-9.12) treatments, but 100% mortality in treatments with concentrations of 500 mg/L (pH 8.58-10.32) to 50000 mg/L (pH 12.39-12.61).
Reported statistics and error estimates:
The NOEC was approximated from the concentrations resulting in <=10% mortality in fish.

Applicant's summary and conclusion

Validity criteria fulfilled:
not specified
In the current test with sand shrimp, the 96h-LC50 for hydrated lime was 158 mg/L. Based on pH values measured at t=0 this is equivalent to 9.70 (9.12-10.3) pH units.