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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

3 h EC50  > 1000 mg/L, 3 h NOEC >= 1000 mg/L (above the limit of water solubility); OECD 209, EU Method C.11, RCC 2006

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information

The inhibitory effect of the test material, dicerium tricarbonate, on the respiration rate of aerobic wastewater microorganisms of activated sludge was investigated in a 3-hour respiration inhibition test which was conducted in accordance with standardised guidelines OECD 209 and EU Method C.11.

In accordance with the EU Commission Directive 92/69/EEC (C.1, C.2, and C.3) and the OECD Series on Testing and Assessment No. 23 (Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures, 2000), a limit test was performed with one concentration of dicerium tricarbonate of nominal 1000 mg/L, to demonstrate that the test material had no toxic effect on activated sludge microorganisms up to and including this concentration.

In addition, two controls and three different concentrations of the reference item 3,5 dichlorophenol (5, 16, and 50 mg/L) were tested in parallel. The results of these reference treatments (EC50 = 12 mg/L within the guideline-recommended range of 5 - 30 mg/L) confirmed suitability of the activated sludge and the method used.

The test material, dicerium tricarbonate, had no significant inhibitory effect on the respiration rate of activated sludge after the incubation period of three hours at the limit test concentration of 1000 mg/L. Thus, the 3-hour NOEC of dicerium tricarbonate to activated sludge microorganisms was at the limit of water solubility of dicerium tricarbonate under the test conditions, or at 1000 mg/L. The 3-hour EC20, EC50 and EC80 were clearly higher than the limit of water solubility of dicerium tricarbonate under the test conditions, or higher than 1000 mg/L.


This is the only reliable activated sludge respiration inhibition study that is available for the substance. It has been performed on a structural analogue, cerium carbonate. The similar toxicological profiles of cerium carbonate and cerium oxalate, along with the structural similarity, mean that this is considered to be an acceptable read-across approach.

The study was performed in line with a recognised OECD guideline and to GLP standard. It is assigned a score of 2 in line with the reliability scoring system of Klimisch et al (1997), based on the fact that a read across approach has been used.