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Toxicity to microorganisms

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Reference
Endpoint:
toxicity to microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Study period:
07 Feb - 18 Mar 2008
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Data based on the inhibition control of a ready biodegradability study. This approach is in accordance with the Guidance on information requirements and chemical safety assessment (Chapter R.7b: Endpoint specific guidance, ECHA 2012).
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
other: EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Qualifier:
according to
Guideline:
other: OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes (incl. certificate)
Remarks:
Hessisches Ministerium fur Umwelt, ländlichen Raum und Verbraucherschutz, Wiesbaden, Germany
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Preparation: 24.7 mg test item + 24.3 mg reference item + 5 mL activated sludge + 239 mL test water (244 mL final volume)
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Source of inoculum/activated sludge: sewage plant Darmstadt Germany
- Preparation of inoculum for exposure: the aerobic activated sludge was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in tap water and centrifuged again. The procedure was repeated 3 times. The sediment was re-suspended in test water and aerated for 2 d. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to dry weight was determined. Based on this ratio, aliquots of 1.5 g dry material/L were mixed with test water. This suspension was used for the experiment.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
28 d
Test temperature:
22 °C (test flasks were incubated in a climatised room)
pH:
7.6 (measured at the start of the test), 6.9-7.7 (measured at the end of the test)
Nominal and measured concentrations:
96 mg/L based on ThODNH4
Details on test conditions:
TEST SYSTEM
- Test vessel: Manometric Test System with test flask containing a volume of approx. 500 mL (BSB Seonsomat system, Aqualytic Langen)
- No. of vessels per concentration (replicates): 2
- No. of vessels per inoculum control (replicates): 2
- No. of vessels per procedure control (replicates): 1
- Abiotic sterile control: 1 replicate, sludge poisoned with HgCl2 (stock solution of 48.84 mg/mL)
- Test performed in closed vessels: yes
- Details of trap for CO2: potassium hydroxide solution (45%) was used for trapping the produced carbon dioxide
- Other: a correction for potential uptake of oxygen by nitrification was considered. Therefore, analysis of nitrate and nitrite using ion chromatography was conducted (Dionex DX 120 ion chromatography system - UV detector UVD 340s and AS 50 Autosampler, wavelength: 225 nm, column: IonPac AS4 A-SC 4 mm x 250 mm, eluent: 15 mmol/L KCl in deionised water, eluent flow: 1.5 mL/min, temperature: 10 - 30 °C)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: according to guideline
- Intervals of water quality measurement: temperature was measured every day. pH was measured in controls at the beginning and in all flasks at the end of the test.

OTHER TEST CONDITIONS
- Photoperiod: continuous darkness

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :pressure decrease in the reaction vessels was measured every day over the 28 d test period

Reference substance (positive control):
yes
Remarks:
sodium benzoate, loading rate of 102 mg/L, corresponding to an oxygen demand of about 170 mg/L [ThOD(NH4)]
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
96 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
other: ThOD(NH4)
Basis for effect:
other: COD
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
102 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
other: COD
Results with reference substance (positive control):
88% biodegradation after 14 d and to a mean of 92% after 28 d of incubation.
78% biodegradation of sodium benzoate in the toxicity control after 14 d and 85% within 28 d based on ThOD(NH4). The test substance is assumed to be not inhibitory to the aerobic activated sludge microorganisms.

Table 1: Cumulative Biochemical Oxygen Demand (mg O2/L) in the toxicity control during the test period of 28 d

Time [d]

Toxicity control [%]

1

19

 

2

29

 

3

49

 

4

56

 

5

59

 

6

63

 

7

65

 

8

67

 

9

69

 

10

71

 

11

73

 

12

75

 

13

76

 

14

78

 

15

79

 

16

79

 

17

81

 

18

82

 

19

83

 

20

83

 

21

83

 

22

84

 

23

84

 

24

85

 

25

85

 

26

85

 

27

85

 

28

85

 

21

83

 

22

84

 

23

84

 

24

85

 

25

85

 

26

85

 

27

85

 

28

85

 

Table 2: % biodegradation of the toxicity control based on ThODNH4

Time [d]

Toxicity control [%]

1

19

 

2

29

 

3

49

 

4

56

 

5

59

 

6

63

 

7

65

 

8

67

 

9

69

 

10

71

 

11

73

 

12

75

 

13

76

 

14

78

 

15

79

 

16

79

 

17

81

 

18

82

 

19

83

 

20

83

 

21

83

 

22

84

 

23

84

 

24

85

 

25

85

 

26

85

 

27

85

 

28

85

 

Description of key information

NOEC (28 d) > 102 mg/L (nominal, OECD 301 F)

Key value for chemical safety assessment

Additional information

No studies investigating the toxicity of D-Glucopyranose, oligomeric, undecyl glycoside (CAS 98283-67-1) to microorganisms are available. However, a toxicity control was performed in the study testing the ready biodegradability (Ibacon GmbH, 2008). These results were used to assess the endpoint `toxicity to microorganisms´. A treatment containing the test item at a concentration of 96 mg/L and sodium benzoate, as a reference substance, at 170 mg/L (both concentrations based on ThOD(NH4)), was inoculated with sewage sludge microorganisms and incubated for 28 d. 88% biodegradation was noted within 14 d based on O2 consumption. Thus, the test item can be assumed to be not inhibitory up to the tested concentration to the activated sludge microorganisms (NOEC (28 d) ≥102 mg/L).