Germanium

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

Reliability:

1 (reliable without restriction)

Justification for type of information:

see section 13 of IUCLID for read across justification

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes

Specific details on test material used for the study:

PPM Pure Metals GmbH

Analytical monitoring:

yes

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

The activated sewage sludge sample was maintained on continuous aeration in the laboratory at a temperature of approximately 21 ºC overnight prior to use in the test. On the day of collection the activated sewage sludge (9 liters) was fed synthetic sewage (400 mL). This was a deviation to the study plan as the activated sewage sludge should have been fed at a rate of 50 mL of synthetic sewage per liter of activated sewage sludge but was considered to have had no adverse effects on the study given that all validation criteria were satisfied. The pH of the sample on the day of the test was 7.8 measured using a Hach HQ40d Flexi handheld meter. Determination of the suspended solids level of the activated sewage sludge was carried out by filtering a sample (100 mL) of the activated sewage sludge by suction through a pre-weighed GF/A filter paper* using a Buchner funnel which was then rinsed 3 times with 10 mL of deionized reverse osmosis water and filtration continued for 3 minutes. The filter paper was then dried in an oven at approximately 105 ºC for at least one hour and allowed to cool before weighing. This process was repeated until a constant weight was attained. The suspended solids concentration was equal to 3.0 g/L prior to use.

Test type:

static

Water media type:

other: synthetic sewage was diluted to 250 mL with water and 250 mL of inoculum added in a 500 mL conical flask

Limit test:

yes

Total exposure duration:

3 h

Remarks on exposure duration:

Observations were made on the test preparations throughout the test period. Observations of the test item vessels at 0 hours were made prior to addition of activated sewage sludge.

pH:

7.0-8.0 adjusted

Dissolved oxygen:

Measured (depletion) measured throughout.

Nominal and measured concentrations:

Nominal: 10, 100, 1000 mg GeO2/L

Details on test conditions:

A synthetic sewage of the following composition, was added to each test vessel to act as a respiratory substrate:
16 g Peptone, 11 g Meat extract, 3 g Urea, 0.7 g NaCl, 0.4 g CaCl2.2H2O, 0.2 g MgSO4.7H2O, 2.8 g K2HPO4
All dissolved in a final volume of 1 liter of water with the aid of ultrasonication

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Results with reference substance (positive control):

The reference item gave a 3-Hour EC50 value of 7.6 mg/L, 95% confidence limits 6.0 to 9.7 mg/L.

Validation Criteria

The coefficient of variation of oxygen uptake in the control vessels in the initial test was 4.1% and the specific respiration rate of the controls was 27.15 mg oxygen per gram dry weight of sludge per hour. The coefficient of variation of oxygen uptake in the definitive test in the control vessels was 3.8% and the specific respiration rate of the controls was 25.66 mg oxygen per gram dry weight of sludge per hour.

The validation criteria have therefore been satisfied.

Validity criteria fulfilled:

yes

Conclusions:

Test well documented and to be used in classification.

Executive summary:

The toxicity to Activated Sludge in a Respiration Inhibition Test, using GeO2 revealed a NOEC of 100 mg/L and an EC50 <1000 mg/L.

Description of key information

Study results were available on the toxicity to several bacteria and yeast strains.

These studies were conducted with GeO2 according to standard protocols.

 

The GeO2 No Observed Effect Concentration (NOEC) in the activated sewage sludge respiration test, after 3 hours exposure was 100 mg/L.

The effect of the test item on the respiration of activated sewage sludge gave a 3-Hour EC50 value of greater than 1000 mg/L.

It was considered unnecessary and unrealistic to test at concentrations in excess of 1000 mg/L.

For Ge, these values would be 70 mg/l, and 700 mg/l, respectively.

Key value for chemical safety assessment

EC50 for microorganisms:

700 mg/L

EC10 or NOEC for microorganisms:

70 mg/L

Additional information

In the activated sewage sludge respiration test, the 3 -h NOEC for Ge was 70 mg/L, whereas the EC50 >700 mg/L.