(2S)-3-Methyl-2-[N-({2'-(1H-1,2,3,4-tetrazol-5-yl)-[1,1-biphenyl]-4-yl}methyl)pentanamido]alkanoic acid

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:

May - Aug 2009

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

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

After the 3-hour contact time, a well mixed sample of the contents was poured into a 300 ml oxygen bottle,
and the flask was sealed with an oxygen electrode connected to a recorder, forcing the air out of the
vessel. Oxygen consumption was measured and recorded for approximately 10 minutes. During measurement, the sample was not aerated but
continuously stirred on a magnetic stirrer.
The pH and temperature were determined in the remaining part of the reaction mixture.
This procedure was repeated for all concentrations of the test substance. Two controls without test substance were tested in each test series, one at the start and one at the end.

Vehicle:

yes

Remarks:

Milli-RO water

Details on test solutions:

Since VALSARTAN/DS 21 was hardly soluble in water test concentrations were prepared separately in Milli-RO water (tap water purified by reverse osmosis; Millipore Corp., Bedford, Mass., USA). One litre test bottles were filled with 250 ml test substance mixtures with initial loading rates exceeding the final test concentration by a factor of 2. These mixtures were stirred in closed bottles for 24-27 hours. In the first experiment the mixtures were also treated with ultrasonic waves (5 minutes) before the stirring period. Subsequently, 16 ml synthetic sewage feed, 200 ml sludge and Milli-RO water up to 500 ml were added resulting in the required loading rate. Optimal contact between the test substance and test
organisms was ensured applying continuous aeration and stirring.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

The sludge was coarsely sieved, washed and diluted with ISO-medium. A small amount of the sludge was
weighed and dried overnight at ca. 105°C to determine the amount of suspended solids 3.8, 6.31 and 4.0 g/l of sludge as used for experiment 1, 2 and
3, respectively). The pH was 6.6, 7.8 and 7.8 on the day of testing of experiment 1, 2 and 3, respectively.
The batch of sludge was used one day after collection; therefore 50 ml of synthetic sewage feed was added per litre of activated sludge at the end of the collection day. The sludge was kept aerated at test temperature until use.

Test type:

not specified

Water media type:

freshwater

Total exposure duration:

3 h

Post exposure observation period:

Oxygen consumption was measured and recorded for approximately 10 minutes.

Test temperature:

The temperature of the test medium was between 19.3 and 19.8°C in the first experiment,
between 18.2 and 18.6°C in the second experiment and between 17.2 and 19.0°C in the third
experiment.

Details on test conditions:

Experiment 2: Since the incubator was not switched on the sludge was not dried overnight before the start of the test. As a result of this the amount of sludge was not made up to 4 g/l. The sludge was dried after the start of the test. The amount of suspended solids was determined to be 6.3 g/l.
Evaluation: The results of the second experiment are only indicative and not used for the final conclusion of this study.

Experiment 3: The temperature in 3 test vessels of the reference substance (30 mg/I) was below the range of the protocol (R3 =17.1 °C, T3=17.3°C and T5=17.2°C).
Evaluation; A deviation of s 0.9°C is no problem for the outcome of the study. The EC50 of 3,5-dichlorophenol was in the accepted range of 5-30 mg/I. The temperature measured in the other test vessels was in the range as described by the protocol (20 ± 2°C, based on round off values).
The acceptability criteria for the test were met.
The study integrity was not adversely affected by the deviations.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol solution

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

750 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.:

> 750 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the present project, no significant inhibition of respiration rate of the sludge was recorded at and below a loading rate of 750 mg/I (=NOEC).
The EC50 was above a loading rate of 750 mg/I.

Description of key information

Under the conditions of the present project, no significant inhibition of respiration rate of the sludge was recorded at and below a loading rate of 750 mg/I (=NOEC).

The EC50 was above a loading rate of 750 mg/I.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

750 mg/L