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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
Study period:
3 hours
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
OECD 209 guideline followed to GLP, June 2016
Assessed to be scientifically valid
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
yes
Specific details on test material used for the study:
COCAMIDOPROPYL PG - DIMONIUM CHLORIDE PHOSPHATE; LOT # 50113A16
Date and Quantity Received: 07 Mar 16
Physical Description: Clear liquid
Storage Conditions: Room temperature
Purity: 41% actives in water.
The substance that has been used in this test is not an alkyl betaine but can hydrolyse to betaines under biological conditions through hydrolysis of the phosphate ester. In the absence of primary data for alkyl betaines and cetyl betaine in particular, it has ben assessed as a reasonable surrogate to assess this end point until primary data can be accessed.
Analytical monitoring:
not required
Vehicle:
no
Details on test solutions:
Substance diluted directly into water.
Test organisms (species):
activated sludge
Details on inoculum:
Samples of activated sludge were obtained from the Brazos Valley Sewer (Sugar Land, Texas) and aerated during transport and storage
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
pH:
Buffered to pH 7.0
Nominal and measured concentrations:
Nominal 62.5, 125, 250, 500, 1000 mg/l actives
Reference substance (positive control):
yes
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 500 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth inhibition
Duration:
3 h
Dose descriptor:
EC100
Effect conc.:
ca. 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth inhibition
Duration:
3 h
Dose descriptor:
EC0
Effect conc.:
> 500 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth inhibition
Details on results:
At concentrations up to and including 500 mg/l, there was an enhancement of oxygen consumption
The test report cites a calculated EC50 of 495 mg/l that is clearly incorrect in view of enhanced effects seen at 500 mg/l.
Results with reference substance (positive control):
Considered valid.
Validity criteria fulfilled:
yes
Conclusions:
The substance enhanced microbial activity at up to 500 mg/l actives in the main test (although in a range finder, there was up to 25% inhibition noted at 100 mg/l). At 1000 mg/l in the range finder and main studies, there was a clear inhibition, with over 90% inhibition in some replicates. The EC50 is not possible to calculate, but is in the range 500 - 1000 mg/l
Executive summary:

The results suggest that the substance should be readily biodegrable at concentrations below 500 mg/l actives in view of enhanced activity; however, at higher concentrations, there appears to be significant inhibition.The EC50 is not possible to calculate, but is in the range 500 - 1000 mg/l.

The substance that has been used in this test is not an alkyl betaine but can hydrolyse to betaines under biological conditions through hydrolysis of the phosphate ester. In the absence of primary data for alkyl betaines and cetyl betaine in particular, it has ben assessed as a reasonable surrogate to assess this end point until primary data can be accessed.

Description of key information

OECD 209 Sludge inhibition

The results suggest that the substance should be readily biodegrable at concentrations below 500 mg/l actives in view of enhanced activity; however, at higher concentrations, there appears to be significant inhibition.

The EC50 is not possible to calculate, but is in the range 500 - 1000 mg/l

Key value for chemical safety assessment

EC50 for microorganisms:
500 mg/L
EC10 or NOEC for microorganisms:
500 mg/L

Additional information

The substance that has been used in this test is not an alkyl betaine but can hydrolyse to betaines under biological conditions through hydrolysis of the phosphate ester. In the absence of primary data for alkyl betaines and cetyl betaine in particular, it has ben assessed as a reasonable surrogate to assess this end point until primary data can be accessed.