Trialuminium bismuth hexaoxide

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)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

not required

Details on sampling:

Samples for chemical analysis not a requirement of the study guideline

Vehicle:

no

Details on test solutions:

Nominal amounts of test item (5, 50 and 500 mg (500 mg in triplicate)) were each separately dispersed in approximately 200 mL of deionized reverse osmosis water and subjected to ultrasonication for approximately 15 minutes followed by magnetic stirring for 24 hours, at room temperature, in order to maximize the dissolved test item concentration. All test vessels were shielded from the light during mixing.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK
- Preparation of inoculum for exposure: 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 was fed synthetic sewage. The pH of the sample on the day of the test was 7.4. Determination of the suspended solids level of the activated sewage sludge was carried out by filtering a sample 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 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 1 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:

freshwater

Limit test:

no

Total exposure duration:

3 h

Hardness:

Not specified

Test temperature:

Temperatures between 19.2 °C and 20.2 °C.

pH:

pH values ranged from 7.4 to 7.9 at the start of test ahead of inoculum addition in test solutions. At the end of the test this ranged from 7.3 to 7.6.

Dissolved oxygen:

The dissolved oxygen concentrations after 30 minutes contact time in all vessels were above 60% of the dissolved oxygen saturation level of 8.9 mg O2/L

Salinity:

Not specified

Conductivity:

Not specified

Nominal and measured concentrations:

Nominal: 10, 100 and 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 500 mL glass conical flask
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: 500 mL
- Aeration: The mixture was aerated with clean, oil-free compressed air via narrow bore glass tubes at a rate of 0.5 to 1.0 liter per minute.
- No. of vessels per concentration (replicates): 1 replicate at 10 and 100 mg/L and 3 replicates at 1000 mg/L
- No. of vessels per control (replicates): 4 replicates in the controls
- Sludge concentration (weight of dry solids per volume): 3 g/L suspended solids concentration
- Nitrification inhibitor used (delete if not applicable): none

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The test water used for the test was deionized reverse osmosis water containing less than 1 mg/L Total Organic Carbon (TOC).
- Particulate matter: No
OTHER TEST CONDITIONS
- Adjustment of pH: No adjustment required
- Photoperiod: Continuous under normal laboratory lighting
- Light intensity: Not specified
- Details on termination of incubation: After respiration rates were measured over a 10 minute period aeration ceased.
EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : 3 hour EC50 and NOEC
TEST CONCENTRATIONS
- Spacing factor for test concentrations: Standard as per guideline

- Range finding study
- Test concentrations: 10, 100 and 1000 mg/L
- Results used to determine the conditions for the definitive study: Definitive study not required as no effects were observed in the range finding study.

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

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

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: Analytical measurements not a requirement of the guideline.
- Effect concentrations exceeding solubility of substance in test medium: Not applicable
- Adsorption (e.g. of test material to the walls of the test container): Not applicable
- Blank controls oxygen uptake rate: The s pecific respiration rate of the controls was 24.83 mg oxygen per gram dry weight of sludge per hour
- Coefficient of variation of oxygen uptake rate in control replicates: The coefficient of variation of oxygen uptake in the control vessels was 4.03%.

Results with reference substance (positive control):

The EC50 value for 3,5-Dichlorophenol was 6.6 mg/L which satisfied validation criterion for the reference item.

Reported statistics and error estimates:

The percentage inhibition values were plotted against concentration for the reference item only, a line fitted using the Xlfit software package (IDBS) and the EC10, EC20, EC50 and EC80 values determined from the equation for the fitted line. 95% confidence limits were calculated for the reference item EC50 value using the method of Litchfield and Wilcoxon (Litchfield and Wilcoxon, 1949).

In order to determine the NOEC, one way analysis of variance incorporating Bartlett's test for homogeneity of variance and Dunnett's multiple comparison procedure for comparing several treatments with a control was carried out on the oxygen consumption data for the range-finding test after 3 hours for the control and all test concentrations to determine any statistically significant differences between the test and control groups. All statistical analyses were performed using the SAS computer software package (SAS, 1999 - 2001).

Oxygen consumption rates and percentage inhibition values after 3 hours contact time:

Nominal concentration (mg/L)		Initial O2 reading (mgO2/L)	Measurement period (minutes)	Final O2 reading (mgO2/L)	O2 Consumption Rates (mg O2/L/hour)	% Inhibition
Control	R1	4.9	4	2.3	39	-
	R2	4.9	4	2.5	36	-
	R3	4.2	3	2.3	38	-
	R4	4.8	4	2.4	36	-
Test Item	10	3.9	3	2.0	38	- 2
	100	4.1	3	1.9	44	- 18
	R1 1000	5.2	5	2.2	36	3
	R2 1000	4.7	4	2.3	36	3
	R3 1000	4.3	4	1.9	36	3
Reference Item	3.2	5.7	8	2.4	24.75	34
	10	6.5	10	3.9	15.6	58
	32	7.2	10	6.4	4.8	87

Validity criteria fulfilled:

yes

Conclusions:

The effect of the test item on the respiration of activated sewage sludge micro-organisms gave a 3-Hour EC50 value of greater than 1000 mg/L. The NOEC after 3 hours exposure was 1000 mg/L.

Description of key information

An OECD guideline, GLP compliant ASRIT study is available. No effects were seen at the highest does tested (1000 mg/L) and accordingly it is not appropriate to set an EC50 value as this was greater than the maximum concentration tested. The NOEC value is set as the highest concentration tested.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L