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Toxicity to microorganisms

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Administrative data

Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
This study was conducted between 24 October 2016 and 25 October 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Reliability 1 is assigned because the study conducted according to OECD TG 209 in c ompliance with GLP, without deviations that influence the quality of the results

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report date:
2017

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))
Version / remarks:
2010
Deviations:
no
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
EDA-BADGE-EDA
Cas Number:
854009-15-7
Molecular formula:
C25H40N4O4
IUPAC Name:
EDA-BADGE-EDA
Constituent 2
Chemical structure
Reference substance name:
EDA-BADGE-EDA-BADGE-EDA
Molecular formula:
C48H72N6O8
IUPAC Name:
EDA-BADGE-EDA-BADGE-EDA
Constituent 3
Chemical structure
Reference substance name:
EDA-BADGE α-glycol
Molecular formula:
C23H34N2O5
IUPAC Name:
EDA-BADGE α-glycol
Constituent 4
Reference substance name:
reaction product of 2,2'-[(1-methylethylidene)bis(4,1-phenyleneoxymethylene)]bisoxirane and ethylene diamine
IUPAC Name:
reaction product of 2,2'-[(1-methylethylidene)bis(4,1-phenyleneoxymethylene)]bisoxirane and ethylene diamine
Constituent 5
Reference substance name:
Unidentified reaction product of 2,2'-[(1-methylethylidene)bis(4,1-phenyleneoxymethylene)]bisoxirane and ethylene diamine
IUPAC Name:
Unidentified reaction product of 2,2'-[(1-methylethylidene)bis(4,1-phenyleneoxymethylene)]bisoxirane and ethylene diamine
Test material form:
liquid: viscous
Specific details on test material used for the study:
Identification: 4,4'-Isopropylidenediphenol, oligomeric reaction products with 1-chloro-2,3-epoxypropane, reaction products with ethylenediamine
Physical state/Appearance: yellow/brown extremely viscous liquid
Batch: BBF01102V1
Purity: unknown
Expiry Date: 01 January 2021
Storage Conditions: room temperature in the dark
Intended use/Application: substance to be used in industry

Sampling and analysis

Analytical monitoring:
no
Remarks:
As it was not a requirement of the Test Guidelines, no analysis was conducted to determine the homogeneity, concentration or stability of the test item formulation. This is an exception with regard to GLP and is reflected in the GLP compliance statement.

Test solutions

Vehicle:
no
Details on test solutions:
Range-Finding Test
Test Item Preparation
In the range-finding test, activated sewage sludge micro-organisms were exposed to a series of nominal test concentrations of 10, 100 and 1000 mg/L. The test item was dispersed directly in water.
The test item was heated to approximately 50 ºC to ensure test item was homogenous. Nominal amounts of test item (5, 50 and 500 mg (in triplicate)) were each separately dispersed in approximately 200 mL of deionized reverse osmosis water and subjected to ultrasonication for approximately 15 minutes followed by magnetic stirring for 24 hours, at measured temperatures of between 19 and 21 C, in order to maximize the dissolved test item concentration. All test vessels were shielded from the light during mixing. Synthetic sewage (16 mL), activated sewage sludge (250 mL) and water were added to a final volume of
500 mL to give the required concentrations of 10, 100 and 1000 mg/L (3 replicates).
The pH of the test item dispersions was measured after stirring using Hach HQ40d Flexi handheld meter and adjusted to between pH 7.0 and 8.0.

Reference Item Preparation
A reference item, 3,5-dichlorophenol, was included in the range-finding test at concentrations of 3.2, 10 and 32 mg/L in order to confirm the suitability of the inoculum. A stock solution of 0.5 g/L was prepared by dissolving the reference item directly in water with the aid of ultrasonication for approximately 20 minutes. The pH of this stock solution was measured to be pH 5.8 and was adjusted to pH 7.1 using 1.0 M NaOH. The pH values were measured using a Hach HQ40d Flexi handheld meter. Aliquots (3.2, 10 and 32 mL) of the stock solution were removed and dispersed with activated sewage sludge (250 mL), synthetic sewage (16 mL) and water to a final volume of 500 mL to give the required concentrations of 3.2, 10 and 32 mg/L. The volumetric flask containing the reference item was inverted several times to ensure homogeneity of the solution.



Test organisms

Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
A mixed population of activated sewage sludge micro-organisms was obtained on
25 October 2016 from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK which treats predominantly domestic sewage

Preparation of Inoculum
Preparation of Inoculum
The activated sewage sludge sample was maintained on continuous aeration in the laboratory at a temperature of approximately 21 ºC and was used on the day of collection. The pH of the sample was 7.6 measured using a Hach HQ40d Flexi handheld meter. Determination of the suspended solids level of the activated sewage sludge was carried out by filtering a sample (100 mL) of the activated sewage sludge by suction through a pre-weighed GF/A filter paper* using a Buchner funnel which was then rinsed 3 times with 10 mL of deionized reverse osmosis water and filtration continued for 3 minutes. The filter paper was then dried in an oven at approximately 105 ºC for at least one hour and allowed to cool before weighing. This process was repeated until a constant weight was attained. The suspended solids concentration was equal to 3.0 g/L.

Study design

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h

Test conditions

Hardness:
Not reported
Test temperature:
19 - 20”C
pH:
7.6 - 8.4
Dissolved oxygen:
5.8 - 8.7 mg O2/L or 65 - 98% of Dissolved Oxygen Saturation Level of 8.9 mg O2/L
Salinity:
Not reported
Conductivity:
Not reported
Nominal and measured concentrations:
Range-Finding Test
Nominal test concentrations of 10, 100 and 1000 mg/L

Details on test conditions:
Experimental Design and Study Conduct
Range-Finding Test

Test Item Preparation
In the range-finding test, activated sewage sludge micro-organisms were exposed to a series of nominal test concentrations of 10, 100 and 1000 mg/L. The test item was dispersed directly in water.
The test item was heated to approximately 50 ºC to ensure test item was homogenous. Nominal amounts of test item (5, 50 and 500 mg (in triplicate)) were each separately dispersed in approximately 200 mL of deionized reverse osmosis water and subjected to ultrasonication for approximately 15 minutes followed by magnetic stirring for 24 hours, at measured temperatures of between 19 and 21”C, in order to maximize the dissolved test item concentration. All test vessels were shielded from the light during mixing. Synthetic sewage (16 mL), activated sewage sludge (250 mL) and water were added to a final volume of
500 mL to give the required concentrations of 10, 100 and 1000 mg/L (3 replicates).
The pH of the test item dispersions was measured after stirring using Hach HQ40d Flexi handheld meter and adjusted to between pH 7.0 and 8.0.
As it was not a requirement of the Test Guidelines, no analysis was conducted to determine the homogeneity, concentration or stability of the test item formulation. This is an exception with regard to GLP and has been reflected in the GLP compliance statement.
The control group was maintained under identical conditions but not exposed to the test item.

Reference Item Preparation
A reference item, 3,5-dichlorophenol, was included in the range-finding test at concentrations of 3.2, 10 and 32 mg/L in order to confirm the suitability of the inoculum. A stock solution of 0.5 g/L was prepared by dissolving the reference item directly in water with the aid of ultrasonication for approximately 20 minutes. The pH of this stock solution was measured to be pH 5.8 and was adjusted to pH 7.1 using 1.0 M NaOH. The pH values were measured using a Hach HQ40d Flexi handheld meter. Aliquots (3.2, 10 and 32 mL) of the stock solution were removed and dispersed with activated sewage sludge (250 mL), synthetic sewage (16 mL) and water to a final volume of 500 mL to give the required concentrations of 3.2, 10 and 32 mg/L. The volumetric flask containing the reference item was inverted several times to ensure homogeneity of the solution.
The exposure conditions for each flask were as described in Section 3.3.1.4.

Preparation of Inoculum
The activated sewage sludge sample was maintained on continuous aeration in the laboratory at a temperature of approximately 21 ºC and was used on the day of collection. The pH of the sample was 7.6 measured using a Hach HQ40d Flexi handheld meter. Determination of the suspended solids level of the activated sewage sludge was carried out by filtering a sample (100 mL) of the activated sewage sludge by suction through a pre-weighed GF/A filter paper* using a Buchner funnel which was then rinsed 3 times with 10 mL of deionized reverse osmosis water and filtration continued for 3 minutes. The filter paper was then dried in an oven at approximately 105 ºC for at least one hour and allowed to cool before weighing. This process was repeated until a constant weight was attained. The suspended solids concentration was equal to 3.0 g/L.

Preparation of Test System
At time "0" 16 mL of synthetic sewage was diluted to 250 mL with water and 250 mL of inoculum added in a 500 mL conical flask (first control). The mixture was aerated with clean, oil-free compressed air via narrow bore glass tubes at a rate of 0.5 to 1.0 liter per minute. Thereafter, at 15 minute intervals the procedure was repeated for the second control followed by the reference item vessels with appropriate amounts of the reference item being added. The test item vessels were prepared as describedabove. Finally two further control vessels were prepared.
The test was conducted under normal laboratory lighting in a temperature controlled room at measured temperatures of between 19 and 20 C.

Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol Physical state/Appearance: pale brown crystalline solid Batch: MKBV7274V; Purity: 99.6%; Expiry Date: 01 September 2017; Storage Conditions: room temperature

Results and discussion

Effect concentrationsopen allclose all
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Key result
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
10 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Details on results:
Range-Finding Test
The dissolved oxygen concentrations after 30 minutes contact time in all vessels were above 60% of the dissolved oxygen saturation level of 8.9 mg O2/L.
No statistically significant toxic effects were shown at the test concentration of 10 mg/L, however statistically significant toxic effects were shown at the test concentrations of 100 and 1000 mg/L.

Validation Criteria
The coefficient of variation of oxygen uptake in the control vessels was 3.1% and the specific respiration rate of the controls was 26.97 mg oxygen per gram dry weight of sludge per hour. The validation criteria have therefore been satisfied.
The validation criterion for the reference item EC50 value was also satisfied

Inhibition of Respiration Rate
4,4'-Isopropylidenediphenol, oligomeric reaction products 3,5-dichlorophenol
ECx (3 hours)(mg/mL) 95% Confidence LImits (mg/mL) ECx (3 hours)(mg/mL) 95% Confidence Limits (mg/mL)
EC10 10-100 - 1.4 -
EC20 10-100 - 2.0 -
EC50 >100 - 6.7 5.1-8.8
EC80 >100 - 22 -
NOEC 10 - - -

No statistically significant toxic effects were shown at the test concentrations of 10 mg/L, however statistically significantly toxic effects (P < 0.05) were shown at the test concentrations of 100 and 1000 mg/L. Based on these results the No Observed Effect Concentration (NOEC) after 3 hours exposure was 10 mg/L.
In some instances, the initial and final dissolved oxygen concentrations were outside those recommended in the test guidelines (7 mg O2/L and 2 mg O2/L respectively). This was considered to have had no adverse effect on the results of the study given that in all cases the oxygen consumption rate was determined over the linear portion of the oxygen consumption trace
Results with reference substance (positive control):
See "Details on Results" (above)

Any other information on results incl. tables

Table 1: Dissolved Oxygen Concentrations of the Test Preparations after 30 Minutes Contact Time in the Range-Finding Test

Dissolved Oxygen Concentrations of the Test Preparations after

30 Minutes Contact Time in the Definitive Test

 

 Dissolved Oxygen Concentration

(mg O2/L)

 Expressed as a Percentage of a Dissolved Oxygen Saturation Level of 8.9 mg O2/L

 Control

 R1

 5.8

 65

 

 R2 5.8  65
   R3  6.1  69
   R4  7..0  79
 Test Item  10  6.2 70
 

 100

 6.3

 71

 

 1000 R1

 8.7

 98

 

 1000 R2

 5.9

 66

 

 1000 R3

 6.3

 71

 3,5 -dichlorophenol

 3.2

 6.5

 73

 

 10

 7.6

 85

 

 32

 8.7

 98

Table 2: Oxygen Consumption Rates and Percentage Inhibition Values after 3 Hours Contact Time in the Range-Finding Test

 Nominal

Concentration

(mg/L)

Initial O2

Reading

(mg O2/L)

 

Measurement Period

(minutes)

 

Final O2 Reading

(mg O2/L)

O2 Consumption Rates

(mg O2/L/hour)

 

 % Inhibition

 Control R1

 5.6

5

 2.2

 40.80

 -

 R2

 6.0

6

 2.0

 40.00

 -

 R3

 5.7

 6

 1.8

 39.00

 -

 R4

 4.8

 4

 2.0

 42.00

 -

 Test Item 10

 5.6

 5

 2.2

40.80

 [1]

 100

 7.1

 10

 3.5

 21.60

47

 1000 R1  8.7  10  8.5  1.20  97
 1000 R2  8.8  10  8.7  0.60  99
 1000 R3  8.9  10  8.8 0.60  99
 3,5 -dichlorophenol 3.2  7.0  10  2.3  28.20  30
 10  7.4  10  4.9  15.00  63
 32  8.3  10  7.5  4.80  88

R1 – R4 = Replicates 1 to 4

[Increase in respiration rate as compared to controls]

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The effect of the test item on the respiration of activated sewage sludge gave a 3 Hour EC50 value of greater than 100 mg/L. The No Observed Effect Concentration (NOEC) after
3 hours exposure was 10 mg/L.
The reference item gave a 3-Hour EC50 value of 6.7 mg/L, 95% confidence limits 5.1 to 8.8 mg/L
Executive summary:

A study was performed to assess the effect of the test item on the respiration of activated sewage sludge.  The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (2010) No. 209 "Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation)".

 Methods

Activated sewage sludge was exposed to an aqueous dispersion of the test item at concentrations of 10, 100 and 1000 mg/L (3 replicates of the 1000 mg/L test concentration) for a period of 3 hours at measured temperatures of between 19 and 20 C with the addition of a synthetic sewage as a respiratory substrate.

The rate of respiration was determined after 3 hours contact time and compared to data for the control and a reference item, 3,5-dichlorophenol.

Results

The effect of the test item on the respiration of activated sewage sludge gave a 3 Hour EC50 value of greater than 100 mg/L.  The No Observed Effect Concentration (NOEC) after

3 hours exposure was 10 mg/L.

The reference item gave a 3-Hour EC50 value of 6.7 mg/L, 95% confidence limits 5.1 to 8.8 mg/L.