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Ecotoxicological information

Toxicity to soil microorganisms

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Reference
Endpoint:
toxicity to soil microorganisms
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Bulk calcium carbonate and uncoated nano calcium carbonate are chemically identical. The only difference between them is the particle size, which may result in minor differences in physico-chemical properties. However, in biological systems and in the environment, both bulk and uncoated nano calcium carbonate are expected to have identical (eco)toxicological and environmental fate properties.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Uncoated nano calcium carbonate (Source): Refer to IUCLID section 1.2 for information on purity and impurities.
Bulk calcium carbonate (Target): Refer to IUCLID section 1.2 for information on purity and impurities.
The majority of new studies have been performed using uncoated nano calcium carbonate as the test material, hence it has been designated as the ‘Source’ in the read-across justification. However, for some endpoints data on bulk calcium carbonate are available and used to read-across to uncoated nano calcium carbonate so for these endpoints, marked with a * in the read-across justification document, bulk calcium carbonate is the ‘Source’.
3. ANALOGUE APPROACH JUSTIFICATION
Please refer to the justification attached in Section 13 of the dataset
4. DATA MATRIX
Please refer to the justification attached in Section 13 of the dataset
Reason / purpose for cross-reference:
read-across source
Qualifier:
according to guideline
Guideline:
OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.21 (Soil Microorganisms: Nitrogen Transformation Test)
Deviations:
no
Duration:
28 d
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate

Description of key information

The effect of uncoated nano calcium carbonate on the nitrogen transformation activity of soil microorganisms has been investigated in a GLP study performed in accordance with OECD Guideline 216. The 28 day EC50 was >1000 mg/kg soil dw and the NOEC was 1000 mg/kg soil dw.

The result from this study demonstrates that calcium carbonate is not toxic to soil microorganisms.

Key value for chemical safety assessment

Additional information

The key study (Clarke, 2010) was performed to OECD TG 216 and in accordance with GLP. The study assessed the effect of uncoated nano calcium carbonate on the nitrogen transformation activity of soil microorganisms at a nominal concentration of 1000 mg/kg. No adverse effects on the nitrogen transformation rate were exhibited at the concentration tested. Hence, the 28 day EC50 for uncoated nano calcium carbonate was found to be >1000 mg/kg soil dw and the NOEC was 1000mg/kg soil dw.

Calcium carbonate is therefore not toxic to soil microorganisms.

The nano form of calcium carbonate was tested because this form was anticipated to represent the worst case as it is likely to be more soluble than the bulk form due to the smaller particle size and hence greater surface area. However, the results are directly applicable to the bulk form of calcium carbonate.