1,4-Benzenediol, 2-(6-oxido-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl)-

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:

Februare 2020

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

In the blank control vessels, 16 mL nutrient solution was mixed with 234 mL water. The positive control vessels and the treatments were prepared by putting the appropriate amount of positive control solution respectively test item into the respective test vessel, adding 16 mL nutrient solution and water to reach a total volume of 250 mL. Then, 250 mL inoculum was added in 5 minutes intervals and the mixtures were aerated.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Test type:

static

Water media type:

freshwater

Remarks:

Tap water

Limit test:

no

Total exposure duration:

3 h

Post exposure observation period:

After 3 hours, the content of the first vessel was poured in a 250 mL narrow-neck bottle and the respiration rate was determined by measurement of the O2-concentration over a period of max. 5 minutes. The following vessels were measured likewise in 5 minutes intervals.

Hardness:

1.18 mmol/L

Test temperature:

18.2-20.3 oC

pH:

8.12

Conductivity:

270 μS/cm

Nominal and measured concentrations:

1,10,100,1000 mg/L nominal concentrations

Details on test conditions:

Duration 3 hours
Replicates
Positive Control 1 replicate/concentration
Test item 1 replicate/concentration (lower concentrations) 5 replicates/concentration (highest concentration 1000 mg/L)
Blank Control 2 replicates before and 2 after measuring positive control and test item, respectively
Water tap water, see annex 2, page 24
Aeration purified air, using Pasteur pipettes,
Feeding nutrient solution, 16 mL/vessel
Temperature 18.2 – 20.3 °C

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol (1,3-Dichloro-5-hydroxybenzene, C6H4Cl2O, CAS-No. 591-35-5) was used as positive control. A stock solution in deionised water containing 500 mg/L was freshly prepared for the experiment.

Key result

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

Key result

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Key result

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):

3h-EC50 = 9.5 mg/L

Reported statistics and error estimates:

For the treatments with the test item concentrations 1000 mg/L, it was tested whether the differences between treatment and blank control were significant. For this determination, the values of the O2 consumption were used.
In order to select a suitable test for significance, it was checked whether equality of variance was given.
As equality of variance is given, the t-test is used.

Validity criteria fulfilled:

yes

Remarks:

A value of 9.5 mg/L for positive control lies within the recommended range of 2 – 25 mg/L. The coefficient of variation of oxygen uptake rate in blank control replicates of 4%was determined is less than 30% at the end of the test.

Conclusions:

One experiment was performed.
The test item was tested using 4 concentrations ranging from 1000 to 1 mg/L nominal con-centration. For the treatment 1000 mg/L, 5 replicates were used; for the other treatments, 1 replicate each.
Because no significant inhibition was observed, no additional experiment had to be per-formed.

Executive summary:

The test item was tested using 4 concentrations ranging from 1000 to 1 mg/L nominal concentration. Toxicity to microorganisms is greater then 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