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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:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This study was conducted under GLPs and followed OECD guidelines. There were no deviations.
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
not required
Vehicle:
no
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Activated sludge collected from the Cambridge Wastewater Treatment Facility, Cambridge, Maryland on 23 July 2012 was utilized as the inoculum for the test. The Cambridge facility receives wastes from predominately domestic sources. The sludge was sieved using a 2 mm screen and allowed to
settle for approximately 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 4000 mg/L by dilution with municipal water.
Test type:
static
Water media type:
freshwater
Limit test:
no
Post exposure observation period:
None
Test temperature:
19.7 - 20.3 C
pH:
8.0
Nominal and measured concentrations:
Nominal concentrations: 10, 100, 1000 mg/L
Details on test conditions:
Temperatures measured throughout the period of sludge maintenance and during the test ranged from 19.7 – 20.3°C. The initial total suspended solids (TSS) concentration of the activated sludge after removal of the supernatant layer measured 22,956 mg/L. The measured TSS concentration of the sludge on the day of testing was 4187 mg/L. The measured pH of the sludge on the day of testing was 8.0.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
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
Details on results:
The respiration rates in the two controls were 93.6 and 102.9 mg O2/L/hr. Both controls had respiration rates above 33.5 mg O2/L/hr, which is the low limit based on the validity criteria for mixtures with 1.67 g dry weight of suspended solids per liter. The coefficient of variation of the two control respiration rates was 6.7%, and was within the 30% limit established for the test. The validity of the test was further supported by the results from the 3,5-dichlorophenol reference group, which resulted in an EC50 value of 22.4 mg/L, with 95 percent confidence limits of 15 mg/L and 50 mg/L. The EC50 for the reference substance was within the 2 to 25 mg/L range considered acceptable for the test.
Results with reference substance (positive control):
The 3,5-dichlorophenol reference group resulted in an EC50 value of 22.4 mg/L, with 95 percent confidence limits of 15 mg/L and 50 mg/L.
Validity criteria fulfilled:
yes
Conclusions:
The EC50 value for BADGE IPD (#33) is greater than 1000 mg/L, the highest concentration tested.
Executive summary:

The effect of BADGE IPD (#33) on activated sludge microorganisms maintained in an aerobic environment was assessed by the Activated Sludge Respiration Inhibition Test Method (OECD Guideline 209). The test contained control, reference and treatment groups. The control replicates were used to determine the background respiration rate of the sludge and were not dosed with the test or reference substance. The reference group was dosed with 3,5-dichlorophenol, a known inhibitor of respiration, at concentrations of 3, 15 and 50 mg/L. The treatment group was dosed with BADGE IPD (#33) at concentrations of 10, 100, and 1000 mg/L. The 1000 mg/L treatment was tested in triplicate. An abiotic control was dosed with the test substance at a concentration of 1000 mg/L to discriminate between abiotic uptake by the test substance and microbial respiration.

The respiration rates in the two controls were 93.6 and 102.9 mg O2/L/hr. Both controls had respiration rates above 33.5 mg O2/L/hr, which is the low limit based on the validity criteria for mixtures with 1.67 g dry weight of suspended solids per liter. The coefficient of variation of the two control respiration rates was 6.7%, and was within the 30% limit established for the test. The validity of the test

was further supported by the results from the 3,5-dichlorophenol reference group, which resulted in an EC50 value of 22.4 mg/L, with 95 percent confidence limits of 15 mg/L and 50 mg/L. The EC50 for the reference substance was within the 2 to 25 mg/L range considered acceptable for the test. An inhibitory dose response effect was observed for the treatment groups; however, the EC50 value

for BADGE IPD (#33) is greater than 1000 mg/L, the highest concentration tested. The abiotic treatment mixture dosed with 1000 mg/L of BADGE IPD (#33) had a respiration rate of –0.6 mg O2/L/hr showing there was no chemical uptake of oxygen by the test substance.

Description of key information

The effect of BADGE IPD (#33) on activated sludge microorganisms maintained in an aerobic environment was assessed by the Activated Sludge Respiration Inhibition Test Method (OECD Guideline 209).

Key value for chemical safety assessment

Additional information

The effect of BADGE IPD (#33) on activated sludge microorganisms maintained in an aerobic environment was assessed by the Activated Sludge Respiration Inhibition Test Method (OECD Guideline 209). The test contained control, reference and treatment groups. The control replicates were used to determine the background respiration rate of the sludge and were not dosed with the test or reference substance. The reference group was dosed with 3,5-dichlorophenol, a known inhibitor of respiration, at concentrations of 3, 15 and 50 mg/L. The treatment group was dosed with BADGE IPD (#33) at concentrations of 10, 100, and 1000 mg/L. The 1000 mg/L treatment was tested in triplicate. An abiotic control was dosed with the test substance at a concentration of 1000 mg/L to discriminate between abiotic uptake by the test substance and microbial respiration.

The respiration rates in the two controls were 93.6 and 102.9 mg O2/L/hr. Both controls had respiration rates above 33.5 mg O2/L/hr, which is the low limit based on the validity criteria for mixtures with 1.67 g dry weight of suspended solids per liter. The coefficient of variation of the two control respiration rates was 6.7%, and was within the 30% limit established for the test. The validity of the test

was further supported by the results from the 3,5-dichlorophenol reference group, which resulted in an EC50 value of 22.4 mg/L, with 95 percent confidence limits of 15 mg/L and 50 mg/L. The EC50 for the reference substance was within the 2 to 25 mg/L range considered acceptable for the test. An inhibitory dose response effect was observed for the treatment groups; however, the EC50 value for BADGE IPD (#33) is greater than 1000 mg/L, the highest concentration tested. The abiotic treatment mixture dosed with 1000 mg/L of BADGE IPD (#33) had a respiration rate of –0.6 mg O2/L/hr showing there was no chemical uptake of oxygen by the test substance.