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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:
weight of evidence
Study period:
1983
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Published study conducted according to accepted methods, only available in German with minimal information on the methods.
Qualifier:
no guideline followed
Version / remarks:
Published study conducted according to accepted methods.
Principles of method if other than guideline:
Acute toxicity to bacteria; respiration inhibitiom test according to the method of Robra (1976).
GLP compliance:
no
Remarks:
Published study
Analytical monitoring:
yes
Details on sampling:
The concentration of heavy water-soluble substances were measured by gas chromatography.
Vehicle:
not specified
Details on test solutions:
No information available.
Test organisms (species):
Pseudomonas putida
Details on inoculum:
No information available.
Test type:
not specified
Water media type:
not specified
Total exposure duration:
30 min
Post exposure observation period:
No information available.
Hardness:
No information available.
Test temperature:
No information available.
pH:
The test medium was neutralised.
Dissolved oxygen:
No information available.
Salinity:
No information available.
Conductivity:
No information available.
Nominal and measured concentrations:
Nominal maximum concentration 500 mg/L.
Details on test conditions:
Bacteria were incubated with the test substance for 30 minutes, and the oxygen consumption measured. The 30 minutes incubation duration was chosen as this is roughly the length of a bacterial generation.
Reference substance (positive control):
not specified
Key result
Duration:
30 min
Dose descriptor:
EC10
Effect conc.:
> 500 mg/L
Nominal / measured:
nominal
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
The 30 minute EC10 based on respiration rate inhibition was > 500 mg/L.
Results with reference substance (positive control):
No information available.
Reported statistics and error estimates:
No information available.

The 30 minute EC10 based on respiration rate inhibition was > 500 mg/L.

Validity criteria fulfilled:
not specified
Conclusions:
The 30 minute EC10 based on respiration rate inhibition was > 500 mg/L.
Executive summary:

The toxicity of pentaerythritol to the bacteria Pseudomona putida was investigated in a respiration inhibition test. Respiration rate was determined by measuring the oxygen consumption during a 30 minute exposure (roughly the length of a bacterial generation). The EC10 was defined as the concentration of a substance that causes a 10% inhibition of consumption compared to the control sample. In this case the EC10 was > 500 mg/L.

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
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Details on sampling:
Not applicable
Vehicle:
no
Details on test solutions:
A 5 g Pentaerythritol Mono Grade/L stock solution was prepared by adding Pentaerythritol Mono Grade (5.0015 g) to a 1000 mL volumetric flask and bringing to volume with deionised water. The solution was ultrasonicated for ca 5 min to aid dissolution.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
A sample of activated sewage sludge was obtained from Haddington Municipal Sewage Works (a local sewage processing plant, which handles predominantly domestic sewage) on 26 January 2010. On arrival at the laboratory, the sludge was aerated for approximately 10 min prior to the contents being allowed to settle without aeration, following which 1 L of the overlying supernatant was siphoned off and discarded. Synthetic sewage feed was added at a rate of 50 mL/L sludge and the sludge held under constant aeration. The solid content of the sludge was determined by shaking the bottle of sludge by hand to homogenise thoroughly. Duplicate sub-samples (5 mL) of the homogenised sludge were dried in an oven at approximately 105°C and the suspended solids content determined as 3.9 g/L, which was acceptable for use. The pH of the sludge was measured as 7.87 upon receipt.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Post exposure observation period:
Not applicable
Hardness:
Not applicable
Test temperature:
18.8 to 19.3°C
pH:
The pH of the sludge was measured as 7.87 upon receipt.
Dissolved oxygen:
Measured during the study.
Salinity:
Not applicable
Conductivity:
Not applicable
Nominal and measured concentrations:
Nominal exposure concentrations were 10, 31.6, 100, 316 and 1000 mg/L.
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
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Results with reference substance (positive control):
The 3 h EC50 for 3,5-DCP to activated sludge was estimated to be 11.97 mg/L with 95 % confidence limits of 10.15 and 14.11 mg/L, under the conditions of this test.
Reported statistics and error estimates:
The respiration rate for each vessel was calculated from the recorded oxygen concentrations and expressed as mg O2/L/h for the period between approximately 6.5 and 2.5 mg O2/L. Where respiration was low the calculation was conducted over the full linear range.

The EC50 and associated 95% confidence interval was estimated using the non-parametric Trimmed Spearman-Karber Method (Hamilton et al, 1977), where appropriate.

Respiration rates and percentage inhibition

Treatment

Nominal concentration (mg/L)

Respiration rate
(mg O2/L/h)

% inhibition

Control 1

0

36.90

-

Control 2

0

36.65

-

Mean of controls

-

36.78

-

% difference in controls

-

0.7

-


3,5,-DCP

5

32.74

10.96

15

13.64

62.90

30

7.77

78.87



Pentaerythritol

10

44.55

0

31.6

41.04

0

100

41.60

0

316

40.80

0

1000

41.78

0

 

Validity criteria fulfilled:
yes
Conclusions:
As there was no inhibition of respiration at any pentaerythritol concentration, the 3 h EC50 for pentaerythritol to activated sludge was estimated as >1000 mg/L, under the conditions of this test.
Executive summary:

The toxicity of pentaerythritol to activated sewage sludge was investigated in a respiration inhibition test according to OECD test guideline 209. Following three hours exposure to pentaerythritol, the EC50 was observed to be > 1000 mg/L (based on nominal exposure concentrations), the corresponding NOEC was observed to 1000 mg/L.

Description of key information

The toxicity of pentaerythritol to the bacteria Pseudomona putida was investigated in a respiration inhibition test. Respiration rate was determined by measuring the oxygen consumption during a 30 minute exposure (roughly the length of a bacterial generation). The EC10 was defined as the concentration of a substance that causes a 10% inhibition of consumption compared to the control sample. In this case the EC10 was > 500 mg/L (Knie, 1983).

 

The toxicity of pentaerythritol to activated sewage sludge was investigated in a respiration inhibition test according to OECD test guideline 209. Following three hours exposure to pentaerythritol the EC50 was observed to be > 1000 mg/L (based on nominal exposure concentrations), the corresponding NOEC was observed to 1000 mg/L (Knight, 2010).

Key value for chemical safety assessment

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

Additional information