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Toxicity to microorganisms

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Reference
Endpoint:
toxicity to microorganisms, other
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
August 11 to September 12, 2005
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
This study was performed according to OECD Guideline 301F with GLP statement. All validity criteria were fulfilled.
Reason / purpose for cross-reference:
reference to same study
Qualifier:
according to guideline
Guideline:
other: OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
Swiss GLP compliance programme (inspected on March 31-April 01, 2005 / signed on June 2005)
Specific details on test material used for the study:
- Physical state: White crystals
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge, domestic
Details on inoculum:
Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City of Geneva, Peney-Dessous) was used.
The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept
aerobic until being used on the same day.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
32 d
Remarks on exposure duration:
Exposure duration of the biodegradation study
Hardness:
No data
Test temperature:
22°C
pH:
The pH is measured and if necessary adjusted to 7.4 ± 0.2 with phosphoric acid or potassium hydroxide
Dissolved oxygen:
No data
Salinity:
Not applicable
Conductivity:
No data
Nominal and measured concentrations:
100 mg/L
Details on test conditions:
The toxicity of the test substance for the inoculum was checked in the biodegradation study. A pair of flasks of the volumetric respirometer was filled with mineral medium + test substance (100 mg/I) + reference substance (Benzoic acid, sodium salt 100 mg/l) + inoculum and their respirations were recorded according to the OECD Guideline 301F. If they are lower than those of the flasks containing mineral medium + reference substance ( 100 mg/l) + inoculum, the test substance can be assumed to be inhibitory to the inoculum used.
Reference substance (positive control):
yes
Remarks:
benzoic acid, sodium salt 100 mg/L
Key result
Duration:
32 d
Dose descriptor:
NOEC
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: O2 consumption
Details on results:
The curves obtained with the reference substance alone and with the test substance + reference substance showed no toxic effect of the test substance to the micro-organisms at the test concentration (100 mg/L).
Results with reference substance (positive control):
See table in "Any other information on results incl. tables".
Reported statistics and error estimates:
None

Table 6.1.7/1: Biodegradability of the reference substance and test substance toxicity control

 

Days

5

7

14

21

28

32

BOD sludge

1st flask

2nd flask

Mean

7.0

4.0

5.5

11.0

8.0

9.5

17.0

17.0

17.0

25.0

26.0

25.5

28.0

29.0

28.5

28.0

29.0

28.5

BOD reference substance

1st flask

2nd flask

Mean

127.0

135.0

131.0

143.0

150.0

146.5

161.0

168.0

164.5

173.0

179.0

176.0

181.0

187.0

184.0

181.0

187.0

184.0

% biodegradation reference substance

1st flask

2nd flask

Mean

73

78

75

80

84

82

86

91

89

89

92

90

92

95

93

92

95

93

BOD refer. + test substance (toxicity control)

1st flask

2nd flask

Mean

148.0

162.7

155.3

157.4

172.7

165.0

168.7

186.8

177.8

176.0

197.8

186.9

182.1

205.8

193.9

183.1

206.8

194.9

BOD: Biological Oxygen Demand, mg O2/L, adjusted to nominal concentrations.

As BOD values of the toxicity control are not lower than those of the flasks containing mineral medium + reference substance ( 100 mg/l) + inoculum (BOD reference substance), the test substance can be assumed to be not toxic to the inoculum used.

Validity criteria fulfilled:
not applicable
Conclusions:
Under the test conditions, test substance should be regarded as not toxic to microorganisms up to 100 mg/L.
Executive summary:

The toxicity effect of the test substance to microorganisms has been determined in the Manometric Respirometry Test according to the OECD Guideline No. 301F, EU Method C.4 -D with GLP compliance, in a toxicity control. A nominal concentration of test substance (100 mg/L) was introduced in the system. The results obtained with the reference substance alone (benzoic acid, sodium salt) and with the test substance + reference substance show no toxic effect of the test substance to the micro-organisms at the test concentration (100 mg/L).

In conclusion, test substance should be regarded as not toxic to microorganisms up to 100 mg/L, under the test conditions.

Description of key information

OECD Guideline 301F, EU Method C.4-D, GLP, Weight of evidence, validity 1:

Not toxic to microorganisms up to 100 mg/L

Key value for chemical safety assessment

Additional information

No activated sludge respiration inhibition test is available on the registered substance. However, a toxicity control was performed in the biodegradation study (Givaudan, 2005) performed on the registered substance and can be used to fulfil this endpoint.

The toxicity effect of the test substance to microorganisms has been determined in the Manometric Respirometry Test according to the OECD Guideline No. 301F, EU Method C.4 -D with GLP compliance, in a toxicity control. A nominal concentration of test substance (100 mg/L) was introduced in the system. The results obtained with the reference substance alone (benzoic acid, sodium salt) and with the test substance + reference substance shows no toxic effect of the test substance to the micro-organisms at the test concentration (100 mg/L).

In conclusion, test substance should be regarded as not toxic to microorganisms up to 100 mg/L, under the test conditions.