Sodium 2-[[4-[3-(4-chlorophenyl)-4,5-dihydro-1H-pyrazol-1-yl]phenyl]sulphonyl]ethanesulphonate

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:

September 18, 2002

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

adopted on 4 April 1984

Principles of method if other than guideline:

The study described in this report was conducted in accordance with ISO/IEC 17025.

GLP compliance:

not specified

Analytical monitoring:

no

Details on test solutions:

These test concentrations were prepared by direct addition of the test substance.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Inoculum: activated sludge from the aeration tank of a municipal biological waste water treatment plant, not adapted, not pre-conditioned.
- Source: ARA Werdhölzli, CH-8048Zürich (18 September 2002;9.30 a.m.).
- Concentration: 1.6 g/l dry matter in the final mixture.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Nominal and measured concentrations:

125, 250, 500, 1000 and 2000 mg/l nominal

Details on test conditions:

TEST SYSTEM
- Test vessel: 1000 ml flasks containing a total volume of test suspension of 500 ml.
- Aeration: aerated by shaking (120 r.p.m.).
- No. of vessels per concentration: one replicate.
- No. of vessels per control: 2 replicates.

TEST MEDIUM / WATER PARAMETERS
- Source of dilution water: synthetic sewage feed prepared with tap water.16 ml of 100-fold sewage concentrate per 500 ml of final test mixture.

EFFECT PARAMETERS MEASURED
The oxygen concentration, in mg/|, was measured with a oxygen electrode inserted to a 300 ml BOD bottle and recorded for about 5 to 10 min.

Reference substance (positive control):

yes

Remarks:

3,S-dichlorophenol

Duration:

3 h

Dose descriptor:

IC50

Effect conc.:

> 2 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

At the applied test concentrations, the following toxic effects to the activated sludge were observed: 2000 mg/l (45 %), 1000 mg/l (41 %), 500 mg/l (34 %), 250 mg/l (31 %),125 mg/(25 %).
Based on these data the EC20 value of test item was estimated to be lower than 125 mg/l. The EC50 and EC80 values were estimated to be higher than 2000 mg/l.

The variation between the two controls was ± 2.8 %.

Results with reference substance (positive control):

The EC50 value of the reference substance 3,5-dichlorophenol was estimated to be 2.5 mg/ which was low but in the range of 5 mg/l thus confirming suitability of activated sludge and test conditions.

Definitive test: activated sludge respiration rates after 3 h of exposure to the test material and calculation of the inhibition.

Nominal concentration (mg/l)	O2 consumption rates (mg/O2l/h)	Respiration inhibition (%)
Control	23.8	-
Control	25.2	-
Test item 125	18.3	25.1
Test item 250	16.9	30.9
Test item 500	16.2	33.8
Test item 1000	14.5	40.8
Test item 2000	13.4	45.2
Reference 3	11.5	53.1
Reference 10	7.0	71.4
Reference 30	2.7	88.9

Validity criteria fulfilled:

yes

Remarks:

The variation between the two controls was ± 2.8 % and the EC50 of reference substance was 2.5 mg/l

Conclusions:

IC50 (3h) > 2000 mg/l

Executive summary:

The inhibitory effect of test item on the oxygen consumption of activated sludge microorganisms of a municipal sewage treatment plant was investigated under aerobic static conditions. The inhibitory effect may include the effect on respiration and nitrification. The exposure time of the test substance on the activated sludge was 3 hours.

The nominal concentrations of test item were 125, 250, 500, 1000 and 2000 mg/l, respectively. These test concentrations were prepared by direct addition of the test substance. No chemical analysis of test concentrations was conducted. For the calculation of the effective concentration leading to 20, 50, and 80 % respiration inhibition the nominal content of the test substance was used, assuming the test compound to be stable in water over 3 h.

At the applied test concentrations, the following toxic effects to the activated sludge were observed: 2000 mg/l (45 %), 1000 mg/l (41 %), 500 mg/l (34 %), 250 mg/l (31 %),125 mg/(25 %).

Based on these data the EC20 value of test item was estimated to be lower than 125 mg/l. The EC50 and EC80 values were estimated to be higher than 2000 mg/l.

Conclusion

IC50 (3h) > 2000 mg/l

Description of key information

IC50 (3h) > 2000 mg/l

Additional information

The inhibitory effect of test item on the oxygen consumption of activated sludge microorganisms of a municipal sewage treatment plant was investigated under aerobic static conditions. The nominal concentrations of test item were 125, 250, 500, 1000 and 2000 mg/l.

At the applied test concentrations, the following toxic effects to the activated sludge were observed: 2000 mg/l (45 %), 1000 mg/l (41 %), 500 mg/l (34 %), 250 mg/l (31 %),125 mg/(25 %). Based on these data the EC20 value of test item was estimated to be lower than 125 mg/l. The EC50 and EC80 values were estimated to be higher than 2000 mg/l.