2,4-dimethyl-4-phenyltetrahydrofuran

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:

20 to 28 August 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

Qualifier:

according to guideline

Guideline:

ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)

Qualifier:

according to guideline

Guideline:

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

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes (incl. QA statement)

Remarks:

Date of Inspection: 20 to 21 November 2018 and 7 June 2019 / date of Decision: 21 August 2019

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Laboratory culture:
- Name and location of sewage treatment plant where inoculum was collected: Bois-de Bay, 1242 Satigny, Switzerland
- Method of cultivation: The sludge was kept aerobic until being used.
- Preparation of inoculum for exposure: The suspended solids content was determined by drying 50 ml of the sludge and weighing. A final concentration of 1.5 g/L of suspended solid was used for inoculum as per ISO 8192-1986.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

20 ± 2°C

pH:

8.18 - 8.42

Dissolved oxygen:

4.70 - 7.90 mg/L (at beginning of the test)

Nominal and measured concentrations:

Nominal concentration: 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 500-ml scaled cylinders
- Type (delete if not applicable): closed
- Aeration: compressed air
- Sludge concentration (weight of dry solids per volume): 2.04 g/L
- Weight of dry solids per volume of reaction mixture per unit of time: 1.5 g/L
- Nutrients provided for bacteria: A synthetic sewage feed

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Dissolved oxygen
TEST CONCENTRATIONS
- Test concentrations: 100 mg/L

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

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

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

> 100 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.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

The respiration rates were calculated from the recorder traces on a linear portion of the curve. They are expressed in mg/(l*min).

Percent inhibition was calculated as following:

% inhibition = (1 – (6Rs / RC1 + RC2 + RC3 + RC4 + RC5 + RC6)) x 100

 

where Rs = respiration rate at tested concentration of the test substance

RC1 = respiration rate of control C1

RC2 = respiration rate of control C2

RC3 = respiration rate of control C3

RC4 = respiration rate of control C4

RC5 = respiration rate of control C5

RC6= respiration rate of control C6.

 

Conditions for the validity of the test:

- The variation coefficient of the controls was 4.3%. This is within the validity range (30%).

- the EC₅₀ (3 hours) of 3,5-dichlorophenol is between 2 and 25 mg/L.

 

Table 6.1.7/1: Results for test substance

Vessel	pH	O2[mg/I] T2.5 min	O2[mg/I] T7.5 min	Δ O2[mg/I]	Time [min]	Rate	% Inhibition	Concentrationfinale [mg/I]
C1	8.30	7.00	5.80	1.20	5.0	0.24	-	-
C2	8.28	6.90	5.75	1.15	5.0	0.23	-	-
C3	8.29	6.15	5.05	1.10	5.0	0.22	-	-
S1	8.32	6.75	5.65	1.10	5.0	0.22	3.6	100.02
S2	8.18	5.75	4.70	1.05	5.0	0.21	8.0	100.08
S3	8.21	6.75	5.65	1.10	5.0	0.22	3.6	99.96
R1	8.40	7.55	6.80	0.75	5.0	0.15	34.3	2.04
R2	8.34	7.10	6.35	0.75	5.0	0.15	34.3	2.02
R3	8.37	6.95	6.30	0.65	5.0	0.13	43.1	2.00
R4	8.36	7.90	7.55	0.35	5.0	0.07	69.3	25.06
R5	8.37	7.85	7.50	0.35	5.0	0.07	69.3	25.16
R6	8.42	7.90	7.60	0.30	5.0	0.06	73.7	24.98
C4	8.39	7.30	6.20	1.10	5.0	0.22	-	-
C5	8.36	7.30	6.20	1.10	5.0	0.22	-	-
C6	8.33	7.20	6.00	1.20	5.0	0.24	-	-

 

Validity criteria fulfilled:

yes

Conclusions:

An activated sludge respiration inhibition test was performed for test substance according to OECD Guideline No. 209, ISO 8192-1986 and EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test). 3 hour EC10 and EC50 were determined to be > 100mg/L and NOEC = 100 mg/L

Executive summary:

An activated sludge respiration inhibition test was performed for test substance according to OECD Guideline No. 209, ISO 8192-1986 and EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test).

In a limit test, a concentration of 100 mg/L (nominal) was evaluated. 3,5-dichlorophenol was used as a reference substance to check the activity of the sludge: its EC₅₀ (3 hours) was found to be within the range 2 to 25 mg/L.

A dissolved oxygen measuring device composed of a flat bottom flask (BOD type, Karlsruher Flasche) in which an O2electrode (StirrOx G, WTW, Weilheim, Germany) fits tightly and an oxygen-meter (inolab Oxi 730, WTW, Weilheim, Germany) connected to personal computer with data recording software (Multilab®pilot v.5.21) is used to measure oxygen concentration versus time.

The pH of the sewage sludge was not measured before the test. The validity of the study is not impacted, as toxicities observed with the of the reference substance were in the expected range. The dry weight of suspended solids was 2.04 g/L. Therefore, in order to obtain the intended final suspended solids concentration of 1.5 g/L, instead of dosing 250 mL of sludge at a concentration of 3.0 g/L as stipulated in the respective standard operation procedure, 370 mL of sludge at a concentration of 2.04 g/L was dosed. The volume of water dosed was reduced accordingly. The validity of the study is not impacted, as the final concentration of sludge in the test cylinders remained unchanged.

At the tested concentration (nominal 100 mg/L) no significant inhibition was observed. Therefore, 3-hour EC₁₀ and EC₅₀ were determined to be > 100mg/L and NOEC = 100 mg/L.

Description of key information

OECD guideline, 209, GLP, key study, Klimish 1:

NOEC=100 mg/L (Limit test)

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

100 mg/L

Additional information

To assess the toxicity of the registered substance to microorganisms, one experimental study is available.

This valid study was performed according to OECD Guideline No. 209, with GLP statement to assess the effect of the registered on the respiration of activated sludge. In a limit test, a concentration of 100 mg/L (nominal) was evaluated.  According to the results of this study, all validity criteria were fulfilled and no significant inhibition was observed at tested concentration (100 mg/L). Therefore, 3-hour EC₁₀and EC₅₀were determined to be > 100mg/L and NOEC = 100 mg/L.