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Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
15-31 March 1989
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP and according to guideline. Limited info on identity.
Justification for type of information:
Data from structural analogue sodium heptogluconate (CAS no.: 31138-65-5) is used for read across to (Gluconate)3 -FeNa3 (CAS no.: 2101772-89-6)
REPORTING FORMAT FOR THE ANALOGUE APPROACH
See Chapter 13 for read across document
Reason / purpose:
read-across source
Qualifier:
according to
Guideline:
other: ISO/TC 147/SC 5/WG
Deviations:
yes
Remarks:
described in test conditions
Principles of method if other than guideline:
The study design is very similar to current ISO 10712 (1995) guideline apart from the absence of a reference substance
GLP compliance:
yes
Remarks:
in house QA
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
The media for bacterial growth (culture and preculture) contained per dm3 demiwater; K2HPO4 1.55 g; NaH2P04, 0.85 g; NH4CL, 0.5 g; MgSO4(H20)7 0.1 g; 0.2 cm3 trace element solution; glucose, 2 g; yeast extract, 0.1 g.
The test substance was dissolved in the growth medium.
All media were sterilized for at least 20 minutes at 120°C.
After inoculation of the cultures, the extinction did not exceed 0.1.
Bacterial suspensions with extinction values >= 0.8 were diluted with demiwater
Test organisms (species):
Pseudomonas putida
Details on inoculum:
The P. putida strain was obtained from the Agricultural University Wageningen, Dept. of microbiology, Wageningen, The Netherlands.
The strain was maintained on yeast/glucose slants which contain per dm3 demiwater 15 g agar; 5 g glucose and 1 g yeast extract.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
16 h
Post exposure observation period:
None
Hardness:
No specific data
Test temperature:
Not given
pH:
No data given
Dissolved oxygen:
No data
Nominal and measured concentrations:
Nominal concentrations: 0.25-0.50-1.00-2.00-4.00 g/L
Details on test conditions:
See test solutions. Incubation for 16 hours. The extinction values of the diluted suspensions were used for the calculation of inhibition percentages. Triplicate measurements per concentration were performed at 435 nm with monochromatic light.
Reference substance (positive control):
no
Duration:
16 h
Dose descriptor:
EC50
Effect conc.:
> 4 g/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Details on results:
No dose dependent inhibition could be observed. Inhibition compared to the controls were 5-16% based on triplicate measurements.
Reported statistics and error estimates:
No data given

Concentration

(g/L)

Mean Extinction

after 16 hours (n=3)

%

inhibition

control

0.255

-

0.25

0.214

16

0.5

0.219

14

1.0

0.233

12

2.0

0.242

5

4.0

0.237

7

Validity criteria fulfilled:
no
Remarks:
partly due to lack of positive control, but growth validity fulfilled
Conclusions:
Study lacks some data (e.g. temperature). Principle of test according to current ISO guideline. The absence of reference substance and the lack of result wrt toxicity it can not be concluded the test was properly performed. Results are considered supportive when additional data/other studies would be available.
Executive summary:

In this study the toxicity of Dissolvine CSA to Pseudomonas putida was investigated. Triplicate measurements of the extinction as indication of growth were performed and compared to controls. Although some minor inhibition was observed (5 -16%) no dose dependency was apparent. It is therefore concluded that the test substance is not toxic for P. putida at nominal concentrations ranging 0.25-4.0 g/L. The EC50 would therefore be concluded at > 4.0 g/L.

Description of key information

No activated sludge respiration inhibition tests have been performed with the Reaction mass of (Gluconate)3Fe-Na3 and NaCl. No inhibition of the oxidation was observed in the preliminary ready biodegradability screening study at 9.3 mg/L the Reaction mass of (Gluconate)3Fe-Na3 and NaCl or 7.1 mg a.i./L (Ginkel, 2018). Based on the absence of any effect on daphnia in the acute daphnia test upto 1000 mg/L it is expected that Reaction mass of (Gluconate)3Fe-Na3 and NaCl will have like Sodium glucoheptonate no effect the respiration of activated sludge upto 1000 mg/L.

For this reason the available study from the structurally similar substance Sodium glucoheptonate (CAS no 31138 -65 -5) has been read across to the Reaction mass of (Gluconate)3Fe-Na3 and NaCl.

One toxicity test with micro-organisms have been performed for which a NOEC of 1000 mg a.i./L was found. In the study from van Ginkel (1989) which was performed according to ISO/TC 147/SC 5/WG after 16 h exposure of P. putida bacteria was evaluated.

Key value for chemical safety assessment

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

Additional information

Introduction:

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 active ingredient (a.i.)/L (3 replicates of the 1000 mg a.i./L test concentration) for a period of 3 hours at a temperature of 20 ± 2°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 EC50value of greater than 1000 mg a.i./L. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 1000 mg a.i./L.

 

It was considered unnecessary and unrealistic to test at concentrations in excess of 1000 mg a.i./L.

 

The reference item gave a 3-Hour EC50value of 12 mg/L, 95% confidence limits 9.6 - 15 mg/L.