3-ethyloxetane-3-methanol

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:

30/07/12-1/08/12

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

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

not required

Details on sampling:

No information provided

Vehicle:

no

Details on test solutions:

A nominal 5000 mg/l stock solution of TMPO was prepared in reverse osmosis water. A nominal 500 mg/l solution of TMPO was prepared by dilution of the 5000 mg/l stock in reverse osmosis water. Test solutions were prepared by addition of a known volume of these stock solutions to a total volume of 100 ml reverse osmosis water, synthetic sewage and activated sludge.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Activated sludge was obtained from the Totnes Sewage Works, Totnes, Devon, UK, on the day of exposure of the test and reference substance. The activated sludge was settled and supernatent decanted. The settled sludge was fed with 50 ml of OECD syynthetic sewage feed per litre of sludge per day and aerated at room temperature until t was used in the test. The pH was measured at 6.9 and was adjusted to 7.2 prior to use.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Post exposure observation period:

Not applicable

Hardness:

No information provided

Test temperature:

20 ±2oC

pH:

7.5-8.4

Dissolved oxygen:

No information provided

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentration = 10, 100 and 1000 mg/l

Details on test conditions:

See methods below

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

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

< 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

In test flask dosed with TMPO, >10% inhibition was observed in all tested concentrations.
The respiration rate of the abiotic controls was negligible. The 3-hour EC50 was found to be greater than 1000 mg/l. The 3-hour EC20 was determined to be 150 mg/l and the 3-hour NOEC was determined to be less than 10 mg/l.

Results with reference substance (positive control):

The 3-hour EC50 for the reference substance (3,5-dichlorophenol) was found to be 3.2 mg/l. As this was in the 2 to 25 mg/l recommended range, the test is considered valid.

Reported statistics and error estimates:

The per centage inhibition was calculated as follows:

%inhibition = [1-[respiration rate of test flask/mean respiration rate of controls]] x 100

Table 1: Inhibition results.

Test substance	Nominal test concentration (mg/l)	pH start	pH end	Respiration rate (mg/L/h)	Percentage inhibition
Control	Control	7.5	8.1	31.6	-
3,5 -DCP	32(abiotic)	7.5	7.4	-	-
3,5 -DCP	32	7.5	8.3	4.3	86
3,5 -DCP	10	7.4	8.4	8.7	72
3,5 -DCP	3.2	7.7	8.4	15.6	50
3,5 -DCP	1.0	7.6	8.3	15.0	52
Control	Control	7.7	8.1	30.8	-
TMPO	1000 (abiotic)	7.5	7.5	-	-
TMPO	1000	7.6	8.2	21.2	32
TMPO	1000	7.8	8.2	21.6	31
TMPO	100	7.7	8.1	25.5	18
TMPO	10	7.7	8.1	27.3	12

Validity criteria fulfilled:

yes

Conclusions:

The 3-hour EC50 of TMPO to activated sludge micro-organisms is >1000 mg/l and the 3-hour NOEC is <10 mg/l.

Executive summary:

A 3-hour OECD 209 activated sludge respiration inhibition test was carried out using trimethylolpropane oxetane. Test solutions were created containing the test substance at concentrations of 10, 100 and 1000 mg/l along with synthetic sewage, activated sludge and reverse osmosis water. 3,5-dichlorophenol was used as a reference substance. The respiration rate of each culture was measured after 3 hours and compared with the mean respiration rate of the controls to determine the percentage inhibition.

The 3 -hour EC50 was found to be greater than 1000 mg/l, while the 3-hour NOEC was found to be less than 10 mg/l.

Description of key information

 The 3-hour EC50 was found to be >1000 mg/l, thereby exceeding the normal highest dose recommended for such studies (1000 mg/L). Therefore, in the chemical safety assessment performed according to Article 14(3) in connection with Annex I section 3 (Environmental Hazard Assessment) no hazard was identified, therefore no PNEC can be derived.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

Additional information

A 3-hour OECD 209 activated sludge respiration inhibition test was carried out using 3-ethyloxetane-3-methanol. Test solutions were created containing the test substance at concentrations of 10, 100 and 1000 mg/l along with synthetic sewage, activated sludge and reverse osmosis water. 3,5-dichlorophenol was used as a reference substance. The respiration rate of each culture was measured after 3 hours and compared with the mean respiration rate of the controls to determine the percentage inhibition.

The 3-hour EC50 was found to be greater than 1000 mg/l, while the 3 -hour NOEC was found to be less than 10 mg/l.