Butyl (S)-2-hydroxypropionate

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:

2016-10-18 to 2017-02-16

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 (incl. QA statement)

Specific details on test material used for the study:

Test item: Butyl-(S)-lactate
Chemical name: Butyl(S)-2-hydroxypropionate
CAS number: 34451-19-9
EC-No.: 252-036-3
Lot number: 1604001332
Active components: 99 %
Stability: Not available
Vapour pressure: 0.4 mBar (20°C)
Relative density: 0.98 g/mL (20 °C)
Water solubility: Soluble
Consistency: Liquid (20 °C)
Colour: Colourless/light yellow
Source: Purac Biochem bv
Water solubility: Soluble
Application test item: Test item was added directly

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

500 mg of the test item were added directly into the test vessels to obtain a final concentration of 1000 mg/L. The pH of the test solution was measured before addition of inoculum.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Activated sludge from the municipal wastewater treatment plant Staufener Bucht was used as test system. The treatment plant has a capacity of 140 000 population equivalents and clarifies predominantly domestic wastewater. Sampling date of activated sludge was 19 October 2016. The activated sludge was kept aerated and fed with synthetic sewage (50 mL per litre and day) until use. Dry solid of the activated sludge was determined as 5.06 g/L by weight measurements before and after 3 h drying at 105 °C (mean of triplicate measurements). The activated sludge was washed twice by settling the sludge, decanting the supernatant and re-suspending the sludge in aerated tap water. Before using, the activated sludge was diluted to 3 g/l dry solids with tap water, in order to obtain a final concentration of 1.5 g/l dry solids in the test.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

21.5 to 22.0 °C.

pH:

7.4

Dissolved oxygen:

4.21 mg/L to 7.87 mg/L

Nominal and measured concentrations:

Limit test:
Nominal test item concentration: 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 1000 mL beakers (Schott, Mainz, Germany)/250-300 mL BOD bottles
- Type (delete if not applicable): Open
- Fill volume: 500 mL for set-up
- Aeration: Stirred and aerated for 180 min at 0.5-1 L/min using room air (membrane pump)
- No. of organisms per vessel: Not applicable
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
The test was performed at five treatment concentrations (three replicates) and a control (with four replicates). According to the test guideline OECD 209 (2010) six controls and five replicates per treatment are in most cases recommended. However, a document from the German Federal Environmental Agency from March 2012 relating to the OECD 209 (2010) indicates that a deviation of the number of replicates is permitted, if the statistical reliability is guaranteed (http://www.reach-info.de/dokumente/Q+A-Document_on_the_new_OECD_209_eng_20120302.pdf). In this study, the coefficient of variation of the controls was well below the requested 30 % and performing the test with less replicates than recommended by the the test guideline is acceptable.
- Biomass loading rate: Not reported. Dry weight of the activated sludge was determined as 3.7 g/L. A final concentration of 1.5 g dw/L was used in the test.

OTHER TEST CONDITIONS
- Adjustment of pH: No

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Respiration rate

TEST CONCENTRATIONS
- Spacing factor for test concentrations: n.a.
- Range finding study: No
- Test concentrations (full test): 1000 mg/L

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol 97 %

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

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- Relevant effect levels: The EC50 of 3,5-dichlorphenol was calculated as 20.6 mg/L and was therefore within the acceptable range of 2 to 25 mg/L. The pH in the reference vessels was 7.3.

Reported statistics and error estimates:

Not applicable: Limit test.

Validity criteria fulfilled:

yes

Conclusions:

An activated sludge respiration inhibition test according to OECD 209 resulted in an EC50 > 1000 mg/L and a NOEC ≥ 1000 mg/L.

Executive summary:

To investigate potential harmful effects of butyl-(S)-lactate on microorganisms, an activated sludge respiration inhibition test was performed according to OECD 209 and under GLP.

Test item

A limit test with the concentration of 1000 mg/L was performed. The pH in the test vessels was 7.4. No inhibition was observed in the test vessels with 1000 mg/L test concentration (–13 to 3 %). The respiration rates in the test vessels were not significantly lower than the respiration rate of the controls (Student’s t-test).

The result is therefore:

EC₅₀ > 1000 mg/L

NOEC ≥ 1000 mg/L

Reference item

The EC₅₀ of 3,5-dichlorphenol was calculated as 20.6 mg/L and was therefore within the acceptable range of 2 to 25 mg/l. The pH in the reference vessels was 7.3.

Blanks

The respiration rate of five of six blanks were within 22.1 and 37.7 mg/(L × h) and the coefficient of variation (CV) was 18 % and therefore less than 30 % . The pH in the blank vessels was 7.3.

The temperature range within the test duration was between 21.5 and 22.0 °C.

Description of key information

A limit test with the concentration of 1000 mg/L was performed according to OECD 209 and under GLP. The pH in the test vessels was 7.4. No inhibition was observed in the test vessels with 1000 mg/L test concentration (–13 to 3 %). The respiration rates in the test vessels were not significantly lower than the respiration rate of the controls (Student's t-test).

The result is therefore:

EC₅₀ > 1000 mg/L

NOEC ≥ 1000 mg/L

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L