2-isopropyl-N-hydroxyethyl 1,3-oxazolidine;methyl carbonato-N-ethyl-2-isopropyl-1,3-oxazolidine;reaction mass of: carbonato-bis-N-ethyl-2-isopropyl-1,3-oxazolidine

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:

from 1998-05-18 to 1998-09-18

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The study is regarded as reliable without restrictions because it was conducted in compliance with GLP regulation and guideline.

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method:
In outline, the study comprised a series of test mixtures containing a fixed quantity of synthetic sewage to provide a uniform respiration substrate. Each was amended with water and the appropriate weight of test substance or volume of reference substance stock solution. The test mixtures were completed sequentially at timed intervals of 15 ± 1 minutes by adding equal volumes of inoculum. Incubations entailed aerating the test preparations with a supply of compressed air delivered to each vessel by a Pasteur pipette for 3 h. At the end of the incubation, electrochemical dissolved oxygen (DO) measurements were made with a DO meter and probe from a sub-sample of each preparation. Incozol LV was tested in duplicate over the following four concentrations: 1.0, 10, 100 and 1000 mg/L. All mixtures comprised 16 mL synthetic sewage diluted to 300 mL with either reverse-osmosis water alone, or with reverse-osmosis water and the 3,5-DCP stock solution. Incozol LV was dosed directly to the appropriate vessels and the resulting mixtures were ultrasonicated prior to inoculation. Inoculation entailed addition of 200 mL activated sludge prepared.

- Controls:
The reference substance employed in this study was 3,5-dichlorophenol (3,5-DCP). A stock solution was prepared by dissolving 0.1250 g 3,5-DCP (97 %) in warm reverse-osmosis water before making the volume up to 250 mL. The reference inhibitor, 3,5-DCP, was run in unreplicated preparations at concentrations of 5, 15 and 45 mg/L. Four controls were set up - two at the start and a pair at the end of the test series.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Culture: A sample of activated sludge was collected from one of the return lines at Burley Menston sewage treatment works (Yorkshire Water, UK), a treatment works whose waste-water catchment is predominantly domestic.
The suspended solids concentration was determined by filtering a 25 mL subsample through a pre-dried and pre-weighed glass microfibre filter (Whatman GF/C). The filter and retained solids were then dried in a microwave oven, re-weighed and the contribution made by the sludge solids determined by the difference.
- Preparation of inoculum for exposure: On the basis of the suspended solids determination, a portion of the sample was diluted with dechlorinated mains water to provide 8 L inoculum with a nominal dry suspended solids concentration of 4 g/L. Following dilution in this manner, the pH of the sludge was 7.34. The inoculum was fed overnight with 400 mL synthetic sewage. A second pH check immediately prior to use indicated that the pH had fallen overnight to 6.43, but was still within the acceptable range of pH 6 to 8. The inoculum was, therefore, used without further adjustment.
- Initial biomass concentration: 4 g/L

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20.3 to 21.3 °C

pH:

6.43

Nominal and measured concentrations:

range finding test: 1.0, 10, 100 and 1000 mg/L

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

IC50

Effect conc.:

> 1 000 mg/L

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Details on results:

No significant inhibition was observed at any of the four Incozol LV concentrations, including 1000 mg/L and it was consequently impossible to determine an EC50 value from the data generated in the range-finder.

Results with reference substance (positive control):

- Results with reference substance valid: yes
- Relevant effect levels:
EC20 : 3 mg/L
EC50: 10 mg/L
EC80: 31 mg/L

Treatment	Log10 conc	Respiration rate, (mg O2/L.h)	Mean	Percentage inhibition
Control	na na na na	53.0 50.5 51.2 58.2	51.5	na
Incozol LV, 1.0 mg/L	0.0000	56.7 57.2	57.0	0
Incozol LV, 10 mg/L	1.000	56.5 53.1	54.8	0
Incozol LV, 100 mg/L	2.000	52.8 55.3	54.1	0
Incozol LV, 1000 mg/L	3.000	48.4 50.5	49.5	4
5 mg/L 3,5-DCP	0.6990	35.9	na	30
15 mg/L 3,5-DCP	1.1761	19.5	na	62
45 mg/L 3,5-DCP	1.6532	5.7	na	89

Validity criteria fulfilled:

yes

Conclusions:

Incozol LV did not inhibit the respiration of activated sludge at concentrations up to and including 1000 mg/L. The concentration of Incozol LV causing a 50 % reduction in respiration rate, relative to untreated controls (EC50), could not be determined from the results of this study, but it exceeded 1000 mg/L.

Executive summary:

A study was conducted according to OECD TG 209 and Directive 87/302/EEC part C, to asses the capacity of Incozol LV to inhibit the aerobic respiratory process of the assorted microorganisms present in activated sludge. Therefore, samples of activated sludge were exposed to various nominal concentrations of Incozol LV, ranging from 1.0 to 1000 mg/L, and their respiration rates measured after 3 h contact time. There was no evidence of significant inhibition at any of these concentrations, and consequently no definitive experiment was performed. Incozol LV did not inhibit the respiration of activated sludge at concentrations up to and including 1000 mg/L. The concentration of Incozol LV causing a 50 % reduction in respiration rate, relative to untreated controls (EC50), could not be determined from the results of this study, but it exceeded 1000 mg/L.

Description of key information

Incozol LV did not inhibit the respiration of activated sludge at concentrations up to and including 1000 mg/L. The concentration of Incozol LV causing a 50 % reduction in respiration rate, relative to untreated controls (EC50), could not be determined from the results of this study, but it exceeded 1000 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

A study was conducted according to OECD TG 209 and Directive 87/302/EEC part C, to asses the capacity of Incozol LV to inhibit the aerobic respiratory process of the assorted microorganisms present in activated sludge.Therefore samples of activated sludge were exposed to various nominal concentrations of Incozol LV, ranging from 1.0 to 1000 mg/L, and their respiration rates measured after 3 h contact time. There was no evidence of significant inhibition at any of these concentrations, and consequently no definitive experiment was performed. Incozol LV did not inhibit the respiration of activated sludge at concentrations up to and including 1000 mg/L. The concentration of Incozol LV causing a 50 % reduction in respiration rate, relative to untreated controls (EC50), could not be determined from the results of this study, but it exceeded 1000 mg/L.