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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
March 7, 2017 to June 15, 2017
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 (Carbon and Ammonium Oxidation))
Version / remarks:
2010
GLP compliance:
yes
Specific details on test material used for the study:
Test Substance Name: Octafluoropentyl Methacrylate
Purity: 99.7%
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
Synthetic sewage, the appropriate amount (g) of test substance and an appropriate volume of deionized water needed to achieve a volume of 250 mL were combined. After the deionized water was added, 250 mL of inoculum was added to bring the total volume up to 500 mL.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Activated sludge collected from the Easton Wastewater Treatment Facility, Easton, Maryland, which receives wastes from predominately domestic sources.

The sludge was sieved using a 2 mm screen and allowed to settle for 30 minutes. The supernatant above the settled solids was removed and the total suspended solids (TSS) concentration of the settled sludge was determined. Total suspended solids in the settled sludge were adjusted to a nominal concentration of approximately 3000 mg/L by dilution with deionized water. Fifty mL of synthetic sewage was added to each liter of adjusted sludge per day. The sludge was maintained at an average temperature of 20 ± 2°C and continuously aerated overnight. The pH and total suspended solids concentration of the activated sludge were determined on the day of use in the study.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
20.09 – 21.85 °C
pH:
7.95
Dissolved oxygen:
respiration rates in the two controls were 27.23 and 26.82 mg O2/L/hr.
Nominal and measured concentrations:
Nominal: 10, 100, 1000 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 1000 mL Erlenmeyer flasks
- Material, size, headspace, fill volume: total volume 500 mL
- Aeration: Yes
- No. of vessels per concentration (replicates): 1 vessel for 10, and 100 mg/L and 3 vessels for 1000 mg/L
- No. of vessels per control (replicates): 2
- No. of vessels per abiotic control (replicates): 1
- Sludge concentration (weight of dry solids per volume): Total suspended solids = 2687 mg/L.
EFFECT PARAMETERS MEASURED:
- Dissolved oxygen concentrations for 30 minutes; contact time for each concentration of reference or test substance with the activated sludge was 30 minutes for the first sampling and 3 hours and 15 minutes for the second sampling.
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
Details on results:
- Blank controls oxygen uptake rate: The respiration rates in the two controls were 27.23 and 26.82 mg O2/L/hr. Controls had an average respiration rate above 26.87 mg O2/L/hr, which is the low limit based on the validity criteria for mixtures with 1.34 g dry weight of suspended solids per liter.
- Coefficient of variation of oxygen uptake rate in control replicates: The coefficient of variation of the two control respiration rates was 1.06%, and was within the 30% limit established for the test.
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- Relevant effect levels: 3,5-dichlorophenol reference EC50 of 15.00 mg/L
Reported statistics and error estimates:
Confidence limits (95%) for the EC50 and the EC50 value itself (when applicable) were determined using binomial probability with nonlinear interpolation only.

The test was considered valid only if the following criteria were met:

         - the two control respiration rates should not be less than 20 mg oxygen per one gram dry weight of activated sludge solids in an hour –the two controls were 20.32 and 20.02 mg O2/L/hr per gram dry weight of activated sludge solids;

         - the two control oxygen uptake rates have a coefficient of variation of 30% or less - coefficient of variation of the two control respiration rates was 1.06%;

         - the EC50 (3 hours) of 3,5-dichlorophenol is in the accepted range of 2 to 25 mg/L - 3,5-dichlorophenol reference group, which resulted in an EC50 value of 15.00 mg/L.

Validity criteria fulfilled:
yes
Conclusions:
An inhibitory dose response effect was not observed for the treatment groups; therefore the NOEC is 1000 mg/L. The 3-hour EC50 values for Octafluoropentyl Methacrylate were greater than 1000 mg/L, the highest concentration tested.
Executive summary:

A GLP-compliant study according to OECD Guideline 209 was conducted to assess the toxicity of octafluoropentyl methacrylate to activated sludge. Activated sludge collected from a predominantly domestic sewage treatment facility was exposed to 10, 100, or 1000 mg/L of test substance for 3 hours. An abiotic control and a positive reference control were included in the study design.

 

The 3-hour EC50 values for octafluoropentyl methacrylate were greater than 1000 mg/L, the highest concentration tested. The abiotic treatment mixture dosed with 1000 mg/L of octafluoropentyl methacrylate had respiration rates of 0.4 mg O2/L/hr showing there was no significant uptake or release of oxygen resulting from abiotic reactions of the test substance. An inhibitory dose response effect was not observed for the treatment groups; therefore, the NOEC is 1000 mg/L.

Description of key information

A GLP-compliant study according to OECD Guideline 209 was conducted to assess the toxicity of octafluoropentyl methacrylate to activated sludge.  Activated sludge collected from a predominantly domestic sewage treatment facility was exposed to 10, 100, or 1000 mg/L of test substance for 3 hours. An abiotic control and a positive reference control were included in the study design.

 

The 3-hour EC50 values for octafluoropentyl methacrylate were greater than 1000 mg/L, the highest concentration tested. The abiotic treatment mixture dosed with 1000 mg/L of octafluoropentyl methacrylate had respiration rates of 0.4 mg O2/L/hr showing there was no significant uptake or release of oxygen resulting from abiotic reactions of the test substance. An inhibitory dose response effect was not observed for the treatment groups; therefore the NOEC is 1000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
1 000 mg/L
EC10 or NOEC for microorganisms:
1 000 mg/L

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