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Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
22-23 September 1999
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
according to outdated OECD 209 (adopted 1997), max. concentration tested was 100 mg/L
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
adopted 1997
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
Version / remarks:
adopted 1999
GLP compliance:
yes
Analytical monitoring:
not required
Vehicle:
no
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Oakley sewage treatment works
- Laboratory culture: no
- Preparation of inoculum for exposure: homogenisation, filtration through Whatman GFC filter paper; synthetic sewage (50 mL/L) was added and the mixture aerated overnight
- Initial biomass concentration: 4 g suspended solids/L
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Hardness:
of dilution water (dechlorinated tap water): 200 - 250 mg/L as CaCO3
Test temperature:
Values (°C) at start (0 h) and end (3 h)
----------------------------------
Controls: 19.7-20.0 / 19.1-19.2
1,3-BG (1, 10, 100 mg/L): 20.0-20.1 / 18.8-19.6
3,5-DCP (3, 10, 32 mg/L): 19.7-19.8 / 18.6-19.4
pH:
Inoculum (activated sludge): pH 7.3
Reference substance (3,5-DCP) stock solution (500 mg/L): pH 7.8
Test substance (1,3-BG) stock solution (500 mg/L): pH 8.2

Values at start (0 h) and end (3 h)
------------------------------
Controls: 7.1-7.4 / 7.8
1,3-BG (1, 10, 100 mg/L): 7.3-7.4 / 7.8-7.9
3,5-DCP (3, 10, 32 mg/L): 7.1-7.3 / 7.8-8.0

Nominal and measured concentrations:
Nominal: 0, 1, 10, 100 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: test beakers, fill volume: 500 mL
- Aeration: oil-free compressed air via Pasteur pipette
- No. of vessels per concentration (replicates): 1 replicate each for 1 mg/L and 10 mg/L, 3 replicates for 100 mg/L
- No. of vessels per control (replicates): 2
- No. of vessels per vehicle control (replicates): not applicable


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: dilution water to prepare synthetic sewage: tap water, softenend and treated by reverse osmosis and purified by UHP (resisitivity: 18 Megohm/cm); synthetic sewage was prepared following the guideline


OTHER TEST CONDITIONS
- Adjustment of pH: no


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : BOD after 3 h of exposure (duration of measurement: 10 min)


TEST CONCENTRATIONS
- Spacing factor for test concentrations: factor 10
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol (3,5-DCP)
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
other: EC80
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
other: EC20
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
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: 3.0, 10.0, 32.0 mg/L
- Other: EC50 = 11.2 mg/L (95% CL: 8.7 - 14.6 mg/L)

Nominal concentration (mg/L)

Respiration rate

mg O2/g*h

% inhibition

Control 1

0

26.8

-

Butane-1,3-diol

1

27.3

0

10

26.3

3

100

26.3

3

100

28.3

0

100

27.8

0

3,5-DCP

3

20.3

25

10

15.9

41

32

5.4

80

Control 2

0

27.3

-

Validity criteria fulfilled:
yes
Remarks:
- 3-h EC50 for 3,5-DCP (11.2 mg/L) is within the required range (5 -30 mg/L); variation of respiration rates in the control < 15%
Conclusions:
The 3-h EC50 of 1,3-butanediol for respiration inhibition of activated sludge is > 100 mg/L.
Executive summary:

The effects of 1,3 -butanediol on the respiration rate of activated sludge were tested in a 3 -h respiration inhibition test following OECD TG 209. Three test concentrations plus two controls (0 mg/L) were set up: 1, 10, 100 mg/L. The highest concentration was tested in triplicate. 3,5 -DCP was used as reference compound and was tested at 3, 10 and 32 mg/L. With the test substance no adverse effects were measured up to 100 mg/L. Therefore, the 3 -h EC50 is > 100 mg/L. The validity criteria were fulfilled. Disturbances of waste water treatment processes are not to be expected when 1,3 -butanediol is released in appropriate amounts.

Description of key information

3-h EC50 (respiration inhibition of activated sludge) > 100 mg/L (OECD TG 209, Barnes, 1999)

40h-IGC50 (growth inhibiting effect to ciliate Tetrahymena pyriformis) = 18035 mg/L (TETRATOX assay, Schultz, 1997)

Key value for chemical safety assessment

EC50 for microorganisms:
18 035 mg/L

Additional information

Weight of evidence approach for toxicity to microorganisms of butane-1,3 -diol

There were two studies available that tested the toxicitiy of butane-1,3 -diol to microorganisms. In the first study, the effects of 1,3 -butanediol on the respiration rate of activated sludge were tested in a 3 -h respiration inhibition test following OECD TG 209 (RL2). Three test concentrations plus two controls (0 mg/L) were set up: 1, 10, 100 mg/L. The highest concentration was tested in triplicate. The test substance showed no adverse effects up to 100 mg/L. Therefore, the 3 -h EC50 > 100 mg/L. The validity criteria were fulfilled. In the other study, the growth inhibiting effect of 1,3 -butanediol on the ciliate Tetrahymena pyriformis was determined using the TETRATOX assay (RL2). The resulting IGC50 (40 h) of 18035 mg/L indicated no significant toxicity of 1,3 -butanediol to microorganisms (ciliates).