potassium titanium oxide (K2Ti6O13)

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:

(Range-finding test) 22 February 1999 (Definitive test) 29 March 1999

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Version / remarks:

87/302/EEC

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.6800 (Modified Activated Sludge, Respiration Inhibition Test for Sparingly Soluble Chemicals)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

(Date of inspection: 23 March 1998 Date of Signature: 21 July 1998)

Analytical monitoring:

no

Details on sampling:

Not performed. Analysis of the concentration, homogeneity and stability of the test material in the test preparations was not appropriate to the Test Guideline.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)

- Method: The test material was prepared by a direct dispersion in water. An amount of test material (500 mg) was dispersed in approximately 250 ml of water and subjected to ultrasonication for approximately 30 minutes. Synthetic sewage (16 ml), activated sewage sludge (200 ml) and water were added to a final volume of 500 ml to give the test concentration of 1000 mg/l.

- Controls: The control group was maintained under identical conditions but not exposed to the test material.

(Positive control) For the purposes of the study a reference material, 3,5-dichlorophenol (Aldrich Batch No 81112 ES02611 ES) was used. Two stock solutions of 50 and 160 mg/I were prepared by direct dispersion in water with the aid of ultrasonic disruption. Aliquots (10 and 100 ml) of the 160 mg/I stock solution were removed and dispersed with activated sewage sludge, synthetic sewage and water to give the final concentrations of 3.2 and 32 mg/l. Similarly, a 100 ml aliquot of the 50 mg/I stock solution was used to prepare the 10 mg/I concentration.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Laboratory culture: A mixed population of activated sewage sludge micro-organisms was obtained on 29 March 1999 from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK

- Method of cultivation / Preparation of inoculum for exposure: The activated sewage sludge sample was maintained on continuous aeration in the laboratory at a temperature of approximately 21ºC and was used on the day of collection. The pH of the sample was 7.5 and the suspended solids equal to 3.7 g/l prior to use.

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
dissolved in 1 litre of water.

Test type:

other: aerobic

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Post exposure observation period:

Not applicable.

Hardness:

100 mg/l as CaCo3.

Test temperature:

21ºC.

pH:

(inoculum) 7.5.

Dissolved oxygen:

(Test system) Approximately 8.3 mg O2/l and 1.0 mg O2/l.
(Initial, test solution, after 3 hours)6.8 - 7.3 mg O2/l.
(Final, test solution, after 3 hours) 0.54 - 0.61 mg O2/l.

Salinity:

Not reported.

Nominal and measured concentrations:

Range-finding Test: (Nominal) 100, 1000 mg/l.

Definitive test: (Nominal) 1000 mg/l.

Details on test conditions:

TEST SYSTEM
For the range-finding test and definitive test, at time "0" 16 ml of synthetic sewage was diluted to 300 ml with water and 200 ml of inoculum added in a 500 ml conical flask (first control).
The mixture was aerated with compressed air via narrow bore glass tubes at a rate of approximately 0.5 – 1 litre per minute. Thereafter, at 15 minute intervals the procedure was repeated with appropriate amounts of the reference material being added. The test material vessels were prepared. Finally a second control was prepared.

- Test vessel: 250 ml darkened glass Biological Oxygen Demand (BOD) bottle.
- Type (delete if not applicable): open.
- Aeration: Yes.
- No. of vessels per concentration (replicates): 3.
- No. of vessels per negative control (replicates): 2.
- No. of vessels per positive control (replicates): 3.


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Dechlorinated laboratory tap water.

OTHER TEST CONDITIONS
- Adjustment of pH: No.
- Light intensity: Normal laboratory lighting.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
As each vessel reached 30 minutes contact time an aliquot was removed from the conical flask and poured into the measuring vessel (250 ml darkened glass Biological Oxygen Demand (BOD) bottle) and the rate of respiration measured using a Yellow Springs dissolved oxygen meter fitted with a BOD probe. The contents of the measuring vessel were stirred constantly by magnetic stirrer. The rate of respiration for each flask was measured over the linear portion of the oxygen consumption trace for an approximate 10 minute period (between approximately 8.3 mg O2/l and 1.0 mg O2/l). This procedure was repeated after 3 hours contact time.


TEST CONCENTRATIONS
- Justification fof the test concentration: Based on the results of the range-finding tests.

RANGE-FINDING TESTS
- Test concentrations: 10, 1000 mg/l.

- Results used to determine the conditions for the definitive study: No significant effect on respiration was observed at either concentration tested.
Based on this information, a single test concentration, in triplicate, of 1000 mg/I was selected for the definitive study.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

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:

respiration rate

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

Remarks:

respiration rate

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

Remarks:

respiration rate

Details on results:

Not reported.

Results with reference substance (positive control):

EC50 (30 min): 11 mg/l
EC50 (3 h): 9.5 mg/l

Reported statistics and error estimates:

Not reported.

Validity criteria fulfilled:

yes

Conclusions:

The effect of the test material on the respiration of activated sewage sludge microorganisms gave a 3-Hour EC50 greater than 1000 mg/l. Correspondingly the No Observed Effect Concentration (NOEC) was equal to 1000 mg/l.

Executive summary:

Methods.

A study was performed to assess the effect of the test material on the respiration of activated sewage sludge. The method followed that described in the OECD Guidelines for Testing of Chemicals (1984) No 209 "Activated Sludge Respiration Inhibition Test" and EEC Commission Directive 87/302/EEC andEPA Ecological Effects Test Guidelines OPPTS 850.6800.

 

Procedure.

Following a preliminary range-finding study, activated sewage sludge was exposed to an aqueous dispersion of the test material at a concentration of 1000 mg/I (three replicate flasks) for a period of 3 hours at 21ºC with the addition of a synthetic sewage as a respiratory substrate.

The rate of respiration was determined after 30 minutes and 3 hours contact time and compared to data for the control and reference material, 3,5-dichlorophenol.

 

Results.

The effect of the test material on the respiration of activated sewage sludge gave a 3-Hour EC50 of greater than 1000 mg/l. Correspondingly the No Observed Effect Concentration (NOEC) was equal to 1000 mg/l.

Description of key information

A study was performed to assess the effect of the test material on the respiration of activated sewage sludge. The effect of the test material on the respiration of activated sewage sludge gave a 3 Hour EC50 of greater than 1000 mg/L. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 1000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

Only one study is available for this endpoint and this will be submitted as a key study for the substance. The effect of the test material on the respiration of activated sewage sludge gave a 3 Hour EC50 of greater than 1000 mg/l. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 1000 mg/L.

The method followed that described in the OECD TG 209 and conducted at a GLP-facility with a reliability of the study 1, according to the scoring system of Klimisch et al., 1997).