1-[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole

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:

14 March 1990

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:

1984

Deviations:

yes

Remarks:

Instead a centrifuged sludge a settled sludge was used. Due to the poor solubility of the test substance at test concentrations, no stock solution was prepared. The test substance was given directly into the medium.

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Preparation of the test solution: 23.2, 6.4, 2.4, 0.9 and 0.21 mg of the test substance were weighed and added to the test medium. The volume was adjusted to 200 mL with water and aerated for 3 hours. Dechlorinated drinking water was used to make the test medium.

NUTRIENTS OF THE TEST MEDIUM (per liter dechlorinated drinking water):
- 16 g Peptone
- 11 g Meat extract
- 3.0 g Urea
- 0.7 g NaCl
- 0.4 g CaCl2 · 2 H20
- 0.2 g MgSO4 · 7 H20
- 2.8 g K2HPO4

Test organisms (species):

activated sludge

Details on inoculum:

- Collection date: Activated sludge collected from the a sewage treatment plant on 13/03/1990.
- Method of preparation: The preparation was carried out according to the method described in the guideline. The sludge was separated from the aqueous layer by settling instead of centrifugation.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Hardness:

Not reported

Test temperature:

18 - 22°C

pH:

Not reported

Dissolved oxygen:

Not reported

Salinity:

Not reported

Conductivity:

Not reported

Nominal and measured concentrations:

- Nominal concentrations: 1.05, 4.5, 12.0, 32.0, and 116.0 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 ml BOD flasks with gas inlet
- Aeration: Yes
- Sludge concentration: 1.4 g/L
- Replication: One vessel for each of the test substance concentration and positive control concentration and 2 vessles for the blank control.

EFFECT PARAMETERS MEASURED :
- Oxygen consumption per hour in mg/L with a ORION - ElectrodeType 97-08, ORION Microprocessor Ionalizer 901 and plotted on a recorder.

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Details on results:

No significant inhibition effects were observed after 3 hours exposure. Based on the nominal concentrations, the EC20-, EC50- and EC80 of the test substance were graphically determined to be over 100 mg/L. Therefore, the NOEC is determinded as 100 mg/L. See Table 1 in "Any other information in results incl. tables" for an overview of the results.

Results with reference substance (positive control):

Based on the nominal concentrations, the EC50 of the reference substance was graphically determined to be 22 mg/L.

Table 1. Overview of the oxygen consumption and inhibition results.

Sample	Conc. (mg/L)	Consumption rate (mg/L/h)	Inhibition (%)
Blank 1	0.00	50.36	-1
Blank 2	0.00	49.09	1
Reference 1	32.00	15.62	69
Reference 2	10.00	43.16	13
Reference 3	3.20	48.89	2
Test conc. 1	116.00	51.43	-3
Test conc. 2	32.00	46.67	6
Test conc. 3	12.00	60.00	-21
Test conc. 4	4.50	47.31	5
Test conc. 5	1.05	51.27	-3

 

The relatively great variations of the values are due to the extremely bad distribution of the test substance in the test medium.

Validity criteria fulfilled:

yes

Remarks:

See "Any other information on materials and methods incl. tables"

Conclusions:

After the incubation period of three hours, the test substance had ≤ 21% inhibition on the respiration rate of activated sludge at concentrations up to and including 116 mg/L, the highest concentration tested. Based on the findings, the 3-hour EC20, EC50 and EC80 were ≥100 mg/L. Therefore, the NOEC was determinded to be 100 mg/L.

Executive summary:

The inhibitory effects of the test substance on the respiration of aerobic waste water bacteria were studied according to OECD guidelines No. 209 (April 1984) at nominal concentrations of 1.05, 4.5, 12.0, 32.0 and 116.0 mg/L. There were two separate controls and 3,5-dichlorophenol as a reference substance at concentrations of 3.2, 10 and 32 mg/L. Instead a centrifuged sludge a settled sludge was used. Due to the poor solubility of the test substance at test concentrations, no stock solution was prepared. The test substance was given directly into the medium. The test was carried out in complicance in GLP and at a temperature of 20 ± 2°C. After the incubation period of three hours, the test substance had ≤ 21% inhibition on the respiration rate of activated sludge at concentrations up to and including 116 mg/L, the highest concentration tested. Relatively great variation in the results were observed due to bad distribution of the test substance in the test medium. Based on the findings the 3-hour EC20, EC50 and EC80 of the test substance were ≥100 mg/L, and the EC50 of the reference substance was graphically determined to be 22 mg/L. Therefore, the NOEC was determined to be 100 mg/L.

Description of key information

All available data was assessed. The study representing the worst-case effects was included here and its effect value was used as the key value. Other studies are included as supporting information.

3-h NOEC = 100 mg/L; Activated sludge; inhibition of total respiration; OECD TG 209; Bader, 1990

3-h EC50 > 100 mg/L; Activated sludge; inhibition of total respiration; OECD TG 209; Bader, 1990

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

100 mg/L

Additional information

Two studies are available for this endpoint. The study representing the worst-case effects was included as the key study and its effect value was used in the CSA. In the key study, the inhibitory effects of the test substance on the respiration of aerobic wastewater bacteria were studied according to OECD TG 209 at nominal concentrations of 1.05, 4.5, 12.0, 32.0 and 116.0 mg/L. There were two separate controls and 3,5-dichlorophenole as a reference substance at concentrations of 3.2, 10 and 32 mg/L. The 3-hour EC50 and NOEC of the test substance were determined to be ≥100 mg/Land 100 mg/L, respectively (Bader 1990, GLP, Reliability 1). The second study on an activated sewage sludge system supported these results showing no significant effect of the test substance up to 100 mg/L in a 5-day test (Spare 1980, no standard guidelines followed, GLP not specified, Reliability 2).