2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one

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:

2002-11-25 to 2002-11-28

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

Version / remarks:

adopted 1984

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EU Commission Directive 87/302/EEC, Part C.11; adopted 1988

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test item was mixed into the tap water by ultrasonic treatment over 15 minutes and intense stirring over 24 hours at room temperature in the dark to dissolve a maximum amount of the test item and/or disperse it as homogeneously as possible. Then, 16 mL of synthetic wastewater and 200 mL of the activated sludge inoculum were added.
- Eluate: tap water or synthetic wastewater
- Controls: yes ( two controls (tap water, synthetic wastewater, and activated sludge inoculum, without test item))

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Laboratory culture: no (source: ARA Ergolz 11, Füllinsdorf, Switzerland)
- Preparation of inoculum for exposure: The sludge was washed once twice with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighed, thereafter dried and the ratio of wet to dry weight was calculated.
- Pretreatment: Based on this ratio, an aliquot of washed sludge was suspended in tap water to obtain a concentration equivalent to 3 g dry material per liter. During holding of three days prior to use, the sludge was fed daily with 50 mL synthetic wastewater per liter and was kept at room temperature under continuous aeration until use.
- Initial biomass concentration: 200 mL activated sludge inoculum with a sludge concentration of 3.4 g/L dry weight (corresponding to about 1.3 g dry material per liter test medium)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

19 °C at the start and at the end of the incubation period

pH:

7.5-7.6 (start); 8.0 - 8.2 (end)

Dissolved oxygen:

at least 8.7 mg/L

Nominal and measured concentrations:

nominal: 6.3,12.5, 25, 50, and 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 1000-mL brown glass flasks
- Aeration: continuous aeration until use
- No. of organisms per vessel: 200 mL activated sludge inoculum with a sludge concentration of 3.4 g/L dry weight (corresponding to about 1.3 g dry material per liter test medium)
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: synthetic wastewater (16 g peptone; 11 g meat extract; 3 g urea; 0.7 g NaCI; 0.4 g CaCl2 x 2H2O; 0.2 g MgS04 x 7H2O; 2.8 g K2HPO4 filled up to a final volume of 1 liter with deionized water)


OTHER TEST CONDITIONS
- Adjustment of pH: The pH of the activated sludge inoculum was adjusted from 8.3 to 7.1 with a diluted sulfuric acid solution.
- Photoperiod: in the dark (brown glass flasks)
- Light intensity:

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

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

Remarks:

respiration rate

Remarks on result:

other: clearly higher than the water solubility limit of the test item, or higher than 100 mg/L

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: clearly higher than the water solubility limit of the test item, or higher than 100 mg/L

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: clearly higher than the water solubility limit of the test item, or higher than 100 mg/L

Details on results:

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values:
- Effect concentrations exceeding solubility of substance in test medium: Thus, the 3-hour NOEC, EC20, and EC50 are cleariy higher than the water solubility limit of the test item under the present test conditions, or higher than 100 mg/L.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: The 3-hour EC50 of the reference item 3,5-dichlorophenol (positive control) was calculated to be 14 mg/L with 95% confidence limits from 7 to 27 mg/L. The 3-hour EC50 is within the guideline-recommended range of 5-30 mg/L, confirming the suitability of the activated sludge used.

Down to the test concentration of 25 mg/L, a part of the test item was suspended in the test media. Thus, these test concentrations were clearly above the water solubility limit of the test item under the present test conditions. The appearance of the test solutions of the two lowest test concentrations of 6.3 and 12.5 mg/L could not be assessed since brown glass flasks were used for the test (because of the light sensitivity of the test item). Up to and including the concentration of 100 mg/L, the test item had no significant inhibitory effect (< 15%) on the respiration rate of activated sludge after the incubation period of 3 hours.

Concentrations above 100 mg/L were not tested. The saturation concentration (water solubility limit of the test item under the present test condition) was obviously reached and no significant inhibition was observed after three hours contact time. Thus, the 3-hour NOEC, EC20, and EC50 are cleariy higher than the water solubility limit of the test item under the present test conditions, or higher than 100 mg/L. The oxygen consumption rates of the two controls (run at the start or at the end of the test) differed only by 3% (guideline-recommended maximum variation: 15%).

Validity criteria fulfilled:

yes

Conclusions:

The inhibition of the degradation activity of activated sludge is not anticipated when introduced to biological treatment plants in appropriate low concentrations.

Executive summary:

In this guideline (OECD 209) study, the 3 hour EC50 (EC 444-860-9) of the test material to sewage microorganisms was determined to be >100 mg/l (nominal). The test was conducted upon a washed activated sewage sludge taken from a municipal sewage treatment plant. The test material is not expected to inhibit sewerage microorganisms at low concentrations.

Description of key information

Study conducted to recognised testing guidelines with GLP certification.

Key value for chemical safety assessment

EC50 for microorganisms:

100 mg/L

Additional information

The inhibition of microbial activity by the test substance was determined by measurement of oxygen consumption of the activated sludge in the respiration inhibition test according to OECD Guideline 209 (RCC Ltd. 2003). A NOEC of > = 100 mg/L and an EC50 of > 100 mg/L was determined after 3 h. The inhibition of the degradation activity of activated sludge is not anticipated when introduced in appropriate low concentrations.