Perhydroimidazo[4,5-d]imidazole-2,5-dione

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1999

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

Qualifier:

according to guideline

Guideline:

ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Test substance: Tetrahydra-imidaza-(4,5-d)-imidazol-2,5-dion.
Batch number: Intermediate product from partie 692.
Date of manufacturing: 27 July 1998.
Purity: 97,6 % resp. 109,3 % based an elementary analysis of carbon and nitrogen respectively.
Impurities: 0.024% urea and 0.02% water.

Analytical monitoring:

yes

Details on sampling:

Not specified.

Vehicle:

yes

Remarks:

Synthetic medium 8mL/vessel 100-fold concentrated OECD Medium.

Details on test solutions:

The highest concentration tested for the test substance was 1000mg/L.
The highest concentration tested for the reference substance was 100mg/L.

Test organisms (species):

activated sludge

Details on inoculum:

The inoculum waws washed, brought to a concentration of 5g/L dry substance and aerated for 24 hours. 50mL were added to a total volume of 250mL to obtain a concentration of 1g/L dry susbtance in the test.

Test type:

not specified

Water media type:

not specified

Limit test:

no

Total exposure duration:

30 min

Remarks on exposure duration:

Exposure was carried out in Erlenmeyer-vessels.

Post exposure observation period:

Observation was carried out 30 minutes post exposure to the test substance.

Hardness:

Not specified.

Test temperature:

20 ± 2 °C.

pH:

6.7-7.2.

Dissolved oxygen:

Oxygen concentration during aeration: >2.5mg/L.
Oxygen concentration immediately before measurement: >6.5mg/L.
Duration of the measurement of oxygen consumption: 6-10mins.

Salinity:

Not specified.

Conductivity:

Not specified.

Nominal and measured concentrations:

The nominal concentration was the highest concentration tested; 1000mg/L.

Details on test conditions:

The EC20 is regarded as a limit value tor possible toxic effects in wastewater treatment plants. The test concentration in biodegradation tests should not exceed the EC20. The EC-values are based an added nominal concentrations and not an analytically determined values. The nominai concentrations which indicate a respiration inhibition of 20, 50 and 80 % can be taken from the graph of the inhibition curve.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks on result:

other: negative

Details on results:

No significant inhibition of respiration was measured up to the highest tested concentration of 1000mg/L.

	EC20 mg/L	EC50 mg/L	EC 80 mg/L	Highest concentration tested
Test Substance	-	-	-	1000
Reference substance	ca. 2	ca. 21	ca. 77	100

Validity criteria fulfilled:

yes

Conclusions:

No significant inhibition of respiration was measured up to the highest tested concentration of 1000mg/L. It can therefore be concluded that the test substance showed no signs of toxicity to micro-organisms.

Executive summary:

This study aimed to determine the inhibition of oxygen consumption by aerobic micro-organisms (activated sludge) by the test substance in the activated sludge respiration inhibition test. This was conducted according to Annex of EEC Directive 88/302/EEC (November 1987), and corresponding to OECD guideline 209 (1993) and ISO standard 8192 (1986). The test results were reported as effective concentrations, indicating a respiration inhibition of 20,50, and 80% compared to a control assay without the test substance.

The results showed that no significant inhibition of respiration was measured up to the highest tested concentration of 1000mg/L. Based on the results it can be concluded that the test substance is non-toxic to micro-organisms under EC 1272/2008, within the experimental conditions of this study.

Description of key information

A study was performed to assess the inhibitory effect of the test substance on the oxygen consumption rate of aerobic micro-organims (activated sludge) after short term exposure (30 minutes). This was conducted according to; Annex of EEC Directive 88/302/EEC (November 1987), and corresponding to OECD Guideline 209 (1993) and ISO 8192 (1986). The test results were reported as effective concentrations, indicating a respiration inhibition of 20,50, and 80% compared to a control assay without the test substance.

EC50 = >1000 mg/L (nominal)

EC10 = >1000 mg/L (nominal)

NOEC = >1000 mg/L (nominal)

The results showed that no significant inhibition of respiration was measured up to the highest tested concentration of 1000mg/L. Therefore based on the test results, the test substance is non-toxic to micro-organisms under EC 1272/2008.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L