2,4(1H,3H)-Pyrimidinedione, 1-(3,5-di-O-acetyl-2-deoxy-.beta.-L-erythro-pentofuranosyl)-5-methyl-

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:

Apr - June 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

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: 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)

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.

Vehicle:

yes

Details on test solutions:

A 3,5-dichlorophenol solution with a final concentration of 0.5 g/1 was prepared. To this end a weighed amount of 250.8 mg was dissolved in 5 ml 1 N NaOH (Merck, Darmstadt, Germany), and subsequently diluted to approximately 15 ml with Milli-Q water (tap water purified by reverse osmosis and subsequently passed over activated carbon and ion-exchange cartridges; Millipore Corp., Bedford, Mass., USA). Then, while stirring 1 N H2S04 (Merck) was added to the point of incipient precipitation, and finally Milli-Q water was added to make up the volume to 500 ml. The
pH was 8.0. Aliquots of 50 ml were stored in a freezer until use. On the day of testing the reference substance solution was defrosted at room temperature and diluted to reach the test concentrations. Three concentrations were tested: 5.0, 12 and 30 mg/I.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Number of micro-organisms:
Number of micro-organisms was determined as the amount of Mixed Liquor Suspended Solids (MLSS) per litre test medium.
Preparation of the sludge:
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 g/1 of sludge, as used for the test). The pH was 6.6 on the day of testing. 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.
Medium:
Adjusted ISO medium, formulated using RO-water (tap-water purified by reverse osmosis; GEON Waterbehandeling, Berkel-Enschot, The Netherlands)
with the following composition:
CaCl2.2H20 211.5 mg/I
MgS04.7H20 88.8 mg/I
NaHC03 46.7 mg/I
KCI 4.2 mg/I

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

19.2 - 20.6

pH:

7.5 - 7.6

Nominal and measured concentrations:

1000 mg/I

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

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

Details on results:

No inhibition of respiration rate of the sludge was recorded at 1000 mg LDT600 C3 per litre and therefore no further testing was needed. Hence, the EC50 of LDT600 C3 exceeded 1000 mg/I (based on nominal concentrations).

Results with reference substance (positive control):

Determination of the EC50-value for 3,5-dichlorophenol
Conc. (mg/l) Inhibition 1%
5.0 32
12 72
30 100

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of this present test, LDT600 C3 was not toxic to waste water (activated sludge) bacteria at a nominal concentration of 1000 mg/I. The EC50 of LDT600 C3 exceeded 1000 mg/I.

Description of key information

Under the conditions of this present test, LDT600 C3 was not toxic to waste water (activated sludge) bacteria at a nominal concentration of 1000 mg/I. The EC50 of LDT600 C3 exceeded 1000 mg/I.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

EC10 or NOEC for microorganisms:

1 000 mg/L