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Ecotoxicological information

Toxicity to microorganisms

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activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP-Guideline study
according to guideline
other: OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
according to guideline
other: EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
GLP compliance:
yes (incl. QA statement)
Ministerium für Arbeit, Integration und Soziales des Landes Nordrhein-Westfalen, Düsseldorf, Germany
Analytical monitoring:
Details on sampling:
- Concentrations: 20 mg DOC/L test item + 20 mg DOL/L reference item
- Sampling method: CO2 was trapped in sodium hydroxide and measured as inorbanic carbon. On the days of CO2 measurement, the sodium hydroxide absorbers were disconnected and aliquots of the solutions were measured regarding the TIC concentration. New absorbers (each containg 200 mL fresh 0.05 M sodium hydroxide) were connected to the test vessel.
On the 28th day 1 mL of concentrated hydrochloric acid was added to each test vessel. Subsequently, they were aerated overnight to drive off the carbon dioxide present in the test suspension. On day 29 the last analysis of evolved carbon dioxide was done. Additionally, the biodegradation was measured by determining the DOC in samples of suspension taken at start and 28 d after addition of the test item. The samples at day 28 were taken before the concentrated hydrochloric acid was added.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Preparation of inoculum for exposure: The sludge was washed in mineral medium and centrifuged (at 1100 g for 10 minutes). The supernatant was discarded. The concentrated sludge was suspended in mineral medium to a concentration of 1 - 3 g suspended solids/L. The sludge was aerated with CO2-free air over night to purge the system of carbon dioxide. A sample was withdrawn just before use for the determination of the dry weight of the suspended solids.
- Initial biomass concentration: The concentration of activated sludge used in the test was 29 mg dry mass/litre (87 mg dry mass/3 L).
Test type:
Water media type:
Limit test:
Total exposure duration:
28 d
Test temperature:
20 ± 2 °C
Nominal and measured concentrations:
20 mg DOC/L
Details on test conditions:
- Test vessel: 5-litre flasks containing 2400 mL mineral medium

- Photoperiod: Darkness

Reference substance (positive control):
28 d
Dose descriptor:
Effect conc.:
> 20 mg/L
Nominal / measured:
Conc. based on:
other: DOC
Basis for effect:
inhibition of total respiration
respiration rate

Description of key information

No effects on microorgansims 

Key value for chemical safety assessment

Additional information

Toxicity of 2 -isocyanatoethyl-methacrylate (MOI) on microorganisms was assessed on the basis of a toxic control tested in the biodegradation study conducted by Simon (2012). This test was performed according to OECD Guideline 301B and EU Method C.4 -C under GLP conditions. In this toxic control, test substance and reference substance were incubated in activated sludge at a concentration of approximately 20 mg/L DOC, respectively, at 22 ± 2 °C. At the end of the test, the biodegradation was 100%, indicating that MOI has no inhibitory effect on the activity of the sludge microorganisms.