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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:
24 April 1981
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
no
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Not specified
- Purity: Not specified
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Concentration of stock solution: 3000 mg/L
Test organisms (species):
activated sludge, industrial
Details on inoculum:
- Initial biomass concentration: 1000 mg/L
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
30 min
Nominal and measured concentrations:
Nominal test concentrations (mg/L): 15, 75, 150, 375, 750 and 1995; control
Details on test conditions:
TEST SYSTEM
- Fill volume: 200 mL
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- Sludge concentration (weight of dry solids per volume): 1000 mg/L
Reference substance (positive control):
no
Key result
Duration:
30 min
Dose descriptor:
NOEC
Effect conc.:
1 995 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
- Blank controls oxygen uptake rate: 19 mg O2/Lh
Test material conc. (mg/L) Oxygen uptake rate (mg O2/L h) Inhibition (%)
15 23 -21
75 20 -5
150 16 16
375 20 -5
750 28 -47
1995 21 -11
Validity criteria fulfilled:
not specified
Conclusions:
No significant inhibitory effects were observed at the highest test material concentration. A NOEC of 1995 mg/L was determined.
Executive summary:

An activated sludge respiration inhibition test was performed following a comparable method to OECD guideline 209. Activated sludge with an initial biomass of 1000 mg/L was exposed statically to cyclohexanol at concentrations of 15, 75, 150, 375, 750 and 1995 mg/L for 30 minutes. A single vessel per concentration and unexposed control was used. A stimulation of respiration was observed in most test concentrations, including the highest concentration tested. A NOEC of 1995 mg/L was determined, based on the absence of inhibitory effects >= 20% at any concentration tested.

Description of key information

NOEC >1995 mg/L, 30 min, equivalent to OECD 209, BASF(1981)

EC50 = 960 mg/L, EC10 = 470 mg/L, 17 h, DIN 38412, part 8, BASF(1991)

Key value for chemical safety assessment

Additional information

An activated sludge respiration inhibition test (BASF 1981) was performed following a method comparable to that of OECD guideline 209. Activated sludge with an initial biomass of 1000 mg/L was exposed statically to cyclohexanol at concentrations of 15, 75, 150, 375, 750 and 1995 mg/L for 30 minutes. A single vessel per concentration and unexposed control was used. An EC20 of >1995 mg/L was determined, based on the absence of inhibitory effects at the highest concentration. This result indicates that cyclohexanol is not harmful to bacteria under the conditions of the study, which is considered to be relevant, adequate, and reliable for the purposes of classification and risk assessment.

A single species test with Pseudomonas putida (BASF 1991) was performed according to a German guideline (DIN 38412, part 8). Bacteria were exposed to cyclohexanol at concentrations of 312.5, 625, 1250, 2500, 5000, 7500 and 10000 mg/L for 17 hours. Four vessels per concentration and unexposed control were used. According to cell multiplication inhibition results, an EC10 of 470 mg/L and an EC50 of 960 mg/L were derived. This supporting study confirms the results from the key study (BASF 1981). Additional data from the public literature also demonstrate that cyclohexanol has generally low potential for toxicity to aquatic microorganisms.