4,8-dicyclohexyl-6-hydroxy-2,10-dimethyl-12H-dibenzo[d,g][1,3,2]dioxaphosphocin

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:

1997-11-17 - 1997-11-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Study conducted under GLP according to EU method C.11 on the registered substance itself with marginal deficiencies in documentation in the test report; the available information allows to draw the conclusion that the test was conducted properly without deviation from the guideline.

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

as set out in 88/302/EEC

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

not applicable

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: direct weighing
- Controls: yes
- Evidence of undissolved material (e.g. precipitate, surface film, etc): none noted

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Pretreatment: none
- Initial biomass concentration: 400 mg/L

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

30 min

Test temperature:

20±2°C

pH:

7.5

Dissolved oxygen:

initially 5.1 - 6.3 mg/L

Nominal and measured concentrations:

0, 100, 1000, 10000 mg/L

Details on test conditions:

TEST SYSTEM
- Material, size, headspace, fill volume: total 250 ml fill volume
- Aeration: permanent for 30 min (incubation time)
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2
- Biomass loading rate: 400 mg/L

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Oxygen consumption

TEST CONCENTRATIONS
- Test concentrations: 0, 100, 1000, 10000 mg/L

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Key result

Duration:

30 min

Dose descriptor:

EC10

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: none noted

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: 5; 10; 20 mg/L led to a respiratory rate of 24.0; 8.6; 4.3 mg/L * h and a respiratory inhibition of 11.1; 68.1; 84.1%.; EC50 = 9.2 mg/L

Validity criteria fulfilled:

yes

Conclusions:

The study was conducted under GLP according to EU method C.11 on the registered substance itself with marginal deficiencies in documentation in the test report; the available information allows to draw the conclusion that the test was conducted properly without deviation from the guideline. The method is considered reasonable and the reference substance produced the appropriate response. Hence, the results can be considered as reliable to assess the effects of 12H-Dibenzo[d,g][1,3,2]dioxa-phosphocin, 4,8-dicyclohexyl-6-hydroxy-2,10-dimethyl- to aquatic microorganisms, here, activated sludge. The determined EC values for respiratory inhibition, i.e. EC50 and EC10, were > 10000 mg/L, clearly indicating that the test substance does not inhibit respiration and shows the relative non-toxicity of 12H-Dibenzo[d,g][1,3,2]dioxa-phosphocin, 4,8-dicyclohexyl-6-hydroxy-2,10-dimethyl- towards microorganisms.

Executive summary:

In a study according to EU method C.11 under GLP, a defined quantity of activated sludge is mixed with synthetic medium and the respiratory rate is measured under static conditions. This rate is compared to those measured in test preparations with various concentrations of 12H-Dibenzo[d,g][1,3,2]dioxa-phosphocin, 4,8-dicyclohexyl-6-hydroxy-2,10-dimethyl-, i.e. 100, 1000, and 10000 mg/L (nominal). In order to check the sensitivity of the activated sludge used, 3,5-dichlorophenol is used as a reference substance. The reference substance produced the appropriate results, the EC₅₀and EC₁₀values of 12H-Dibenzo[d,g][1,3,2]dioxa-phosphocin, 4,8-dicyclohexyl-6-hydroxy-2,10-dimethyl- were determined to be > 10000 mg/L. This toxicity study is classified as acceptable and satisfies the guideline requirement for a toxicity study in microorganisms.

Description of key information

Toxicity to microorganisms: 0.4 g/L activated sludge of a predominantly domestic sewage, static, 30 min exposure, 0, 100, 1000, 10000 mg/L (nominal): EC10, EC50 > 10000 mg/l (EU method C.11, GLP)

Key value for chemical safety assessment

EC50 for microorganisms:

10 g/L

EC10 or NOEC for microorganisms:

10 g/L

Additional information

Nominal concentration is above the water solubility of the test item: Its estimated water solubility is 1.171 E-5 mg/l and the test item needs to be considered as insoluble.