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Toxicity to microorganisms

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Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
4 March 2010
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Read-across to study performed according to OECD and/or EC guidelines and according to GLP principles.
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
Deviations:
no
Qualifier:
according to
Guideline:
ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
Since Standolized linseed oil was hardly soluble in water test concentrations were prepared separately in Milli-RO water (tap water purified by reverse osmosis; Millipore Corp., Bedford, Mass., USA). Two 1 litre test bottles were filled with 250 ml of test substance mixtures with initial loading rates of 200 mg/l. These mixtures were stirred in closed bottles for 24 hours.
Subsequently, 16 ml synthetic sewage feed, 200 ml sludge and Milli-RO water up to 500 ml were added resulting in a loading rate of 100 mg/l . Optimal contact between the test substance and test organisms was ensured applying continuous aeration and stirring during the 3-hour exposure period.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
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 (4.2 g/l of sludge, as used for the test). The pH was 8.0 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.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Post exposure observation period:
Oxygen consumption was measured and recorded for approximately 10 minutes afther the 3-hour exposure period.
Test temperature:
between 19.9 and 20.1°C.
pH:
8.3 - 8.4
Dissolved oxygen:
Oxygen consumption:
Controls: 62 - 64 mg O2/l/h
Standolized linseed oil: 63 mg O2/l/h
The oxygen concentration at the start of measurents was at least 4.2 mg O2/l.
Nominal and measured concentrations:
Loading rate of 100 mg/l
Details on test conditions:
TEST SYSTEM
- Type (delete if not applicable): open
- Material, size, headspace, fill volume:All glass, approximately 300 ml oxygen bottles and 1 litre test bottles.
- Aeration: During exposure with clean, oil-free air.
- No. of vessels per concentration (replicates):2
- No. of vessels per control (replicates):2
- Biomass loading rate: 1.7 g/l suspenden solid in final test mixture.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Tap-water purified by reverse osmosis (Milli-RO)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
The respiration rate from each vessel, in mg O2/l/hr, was calculated from the linear part of the respiration curve, which was generally between 2.5 and 6.5 mg O2/l.

TEST CONCENTRATIONS
-limit test at a loading of 100 mg/l.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
No inhibition of respiration rate of the sludge was recorded at a loading rate of 100 mg Standolized linseed oil per litre. The duplicate measurement confirmed the result of the first measurement. Therefore, no further testing was needed.
Results with reference substance (positive control):
The EC50 of 3,5-dichlorophenol was in the accepted range of 5-30 mg/l (9.8 mg/l)
Reported statistics and error estimates:
For the reference substance the percentage inhibition was plotted against the logarithm of the concentrations and the EC50 was determined using linear regression analysis.
For Standolized linseed oil no EC50 could be calculated because the test substance proved to be non-toxic (EC50 > 100 mg/l).
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of this present test, Standolized linseed oil was not toxic to waste water (activated sludge) bacteria at a loading rate of 100 mg/l. The 3-hour EC50 of Standolized linseed oil exceeded a loading rate of 100 mg/l.
Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
See attached justification
Reason / purpose:
read-across source
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
No inhibition of respiration rate of the sludge was recorded at a loading rate of 100 mg Standolized linseed oil per litre. The duplicate measurement confirmed the result of the first measurement. Therefore, no further testing was needed.
Results with reference substance (positive control):
The EC50 of 3,5-dichlorophenol was in the accepted range of 5-30 mg/l (9.8 mg/l)
Reported statistics and error estimates:
For the reference substance the percentage inhibition was plotted against the logarithm of the concentrations and the EC50 was determined using linear regression analysis.
For Standolized linseed oil no EC50 could be calculated because the test substance proved to be non-toxic (EC50 > 100 mg/l).
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of this present test, Standolized linseed oil was not toxic to waste water (activated sludge) bacteria at a loading rate of 100 mg/l. The 3-hour EC50 of Standolized linseed oil exceeded a loading rate of 100 mg/l.

Description of key information

The 3-hour EC50 of Standolized soybean oil is expected to exceed a loading rate of 100 mg/l

Key value for chemical safety assessment

EC50 for microorganisms:
100 mg/L

Additional information

The data for soybean oil, polymerized was read-across from two studies with linseed oil, polymerized.

Two studies are available. In a key study conducted under GLP and according to OECD 209, Standolized linseed oil (viscosity 49 Poise) was not toxic to waste water (activated sludge) bacteria at a loading rate of 100 mg/l. The 3-hour EC50 of Standolized linseed oil exceeded a loading rate of 100 mg/l.

In a second study Standolized linseed oil (viscosity 800 Poise) was not toxic to Pseudomonas putida at an EC50 of > 100 g/L. In this test, an emulsifying agent was used. Therefore, and as the latter test was not conducted according to GLP and because the observed toxicity value was higher, this study was considered as a supporting study.