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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
other: EEC guideline 79/831/EEC, Annexe V, part C: Methods for the determination of ecotoxicity, algae: Test of growth inhibition, May 1988
GLP compliance:
yes
Analytical monitoring:
yes
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
Test species: Scenedesmus subspicatus
Strain: CHODAT SAG 86.81
Source: Algae collection Goettingen, SAG 86.81
Test type:
static
Water media type:
freshwater
Limit test:
no
Test temperature:
23 ± 2 °C
pH:
7.65 - 8.80
Details on test conditions:
Aeration: none
No. of replicates:
3 inoculated replicates
1 uninoculated replicate for measuring the pH-value of the uninoculated test concentrations after an incubation time of 72 h.
Controls: negative control

TEST MEDIUM / WATER PARAMETERS
Dilution water: according to EEC guideline 79/831/EEC, Annexe V, part C:
Methods for the determination of ecotoxicity, algae: Test of growth inhibition, May 1988 and the SOP of the laboratory
Deviation from the SOP: Each test concentration was mixed according to the following regimen:
1 part of inoculum (1E+05 cells/ml in test medium)
1 part of test medium (10 times concentrated)
8 parts of test substance (in appropriate water dilutions)

TEST CONDITIONS
Illumination: 120 uEinstein/m*m*s (permanent Illumination, Color of light was universal white, L 25 (Osram))
Inoculation density: 10000 cells/mL (initial concentration in the test)

TEST CONCENTRATIONS
Test concentrations: 100 mg/L - 0.39 mg/L
Stock solution: 125 mg/L
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.39 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
0.78 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.7 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
2.77 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC90
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate

Effect on the development of biomass:

EbC 10 = 0.48 mg/L

EbC 50 = 1.01 mg/L

EbC 90 = 100 mg/L

Effect on growth rate:

ErC 10 = 0.70 mg/L

ErC 50 = 2.77 mg/L

ErC 90 >= 100.0 mg/L

No observed effect concentration (95 % significance level):

NOEC (72 h) = 0.39 mg/L

Lowest observed effect concentration:

LOEC (72 h) = 0.78 mg/L

VALIDTY CRITERIA:

The validity criteria were maintained.

Factor of cell division (cell count) after 72 hours: 46

SUMMARY OF THE CONCENTRATION CONTROL ANALYSIS:

The concentrations 100 and 12.5 mg/L, the untreated control and the stock  solution (125 mg/L) were analysed. Test

conditions and results are listed in the GLP-reports 94LOO650 and  94LOO663, dated 22 Nov 1994, from Dr. Scholtissek, BASF AG, ZAX/OF.

Time scan:

begin of test (0 h) - uninoculated replicate

end of test (72 h) - uninoculated replicate

end of test (72 h) - inoculated replicate after removal of algal cells through centrifugation

Recovery in %:

                   control   /       test      /     stock solution /

-----------------------------------------------------------

t= 0 h uninoculated    <DL    / 100-104 /      99.2       /

t= 72 h uninoculated   <DL    /  96-99  /      98.4       /

t= 72 h inoculated     <DL    /  99-104 /        -        /

-----------------------------------------------------------

DL= detection limit (1 mg/L)

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
yes
Remarks:
modified test system without iron limitation (medium differing to OECD)
Principles of method if other than guideline:
The study was conducted according to the EU guideline EEC/79/831, Annex V, C, Algae and the standard operating procedures (SOP) of the BASF laboratory.
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
Stock solutions:
249.75 mg/L (Na4-EDTA)
177.55 mg/L (FeCl3 × 6*H2O)
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
Test species: Scenedesmus subspicatus
Strain: CHODAT SAG 86.81
Source: Algae collection Goettingen, SAG 86.81
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
23 ± 2 °C
pH:
ca. 8
Nominal and measured concentrations:
Test concentrations: 263.04 µmol/L - 1.03 µmol/L
Details on test conditions:
TEST CONDITIONS
Illumination: 120 µEinstein/m×m×s (permanent Illumination, Color of light was universal white, L 25 (Osram))
Inoculation density: 10000 cells/mL (initial concentration in the test)

TEST SYSTEM
Aeration: none
No. of replicates:
3 inoculated replicates
1 uninoculated replicate for measuring the pH-value of the uninoculated test concentrations after an incubation time of 72 h.
Controls: negative control

TEST MEDIUM / WATER PARAMETERS
Dilution water: OECD medium differing to the SOP of the laboratory
Each test concentration was mixed according to the following regimen:
1 part algal cell suspension in OECD medium
1 part OECD medium 9-times concentrated
4 parts FeCl3 x 6 H2O dilutions in H2O
4 parts Na4-EDTA dilutions in H2O
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC90
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
The validity criteria were fulfilled.
Factor of the cell proliferation (cell count) after 72 h: 36.7

Effect on Biomass:
------------------
EbC 10 = > 263.04 µmol/L (> 100 mg/L Na4-EDTA)
EbC 50 = > 263.04 µmol/L (> 100 mg/L Na4-EDTA)
EbC 90 = > 263.04 µmol/L (> 100 mg/L Na4-EDTA)

Effect on Growth rate:
----------------------
ErC 10 >= 263.04 µmol/L (> 100 mg/L Na4-EDTA)
ErC 50 >= 263.04 µmol/L (> 100 mg/L Na4-EDTA)
ErC 90 >= 263.04 µmol/L (> 100 mg/L Na4-EDTA)

NOEC (72 h) = 263.04 µmol/L (100 mg/L Na4-EDTA)
LOEC (72 h) >= 263.04 µmol/L (> 100 mg/L Na4-EDTA)

Observations:
-------------
Over the whole range of test concentrations, a stimulation of the cell proliferation was observed (max. 30.4 % based on biomass).

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Remarks:
Summary of available data used for the endpoint assessment of the target substance.
Adequacy of study:
weight of evidence
Justification for type of information:
Refer to the Analogue Approach Justification document provided in Section 13.
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across source
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: RA-A, CAS 64-02-8, BASF SE, 1995, D. subspicatus, 72 h, RL2; 95/9999/60/1
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: RA-A, CAS 64-02-8, BASF SE, 1995, D. subspicatus, 72 h, RL2; 95/9999/60/1
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.7 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: RA-A, CAS 64-02-8, BASF SE, 1995, D. subspicatus, 72 h, RL2; 94/1080/60/1
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
2.77 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: RA-A, CAS 64-02-8, BASF SE, 1995, D. subspicatus, 72 h, RL2; 94/1080/60/1

Description of key information

EDTA species are considered to be of low toxicity to aquatic algae based on the available studies.

Key value for chemical safety assessment

Additional information

Since no studies investigating the toxicity trisodium hydrogen EDTA (CAS 150-38-9) to freshwater algae are available, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5 a read-across to structurally related EDTA species was conducted. This read-across is justified in detail in the overall summary (IUCLID Section 6.1) and within the analogue justification in IUCLID Section 13.

For the assessment of toxicity to algae data from the source substance tetrasodium EDTA (CAS 64-02-2) was used. Testing algae toxicity with complexing agents is considered to be challenging. Complexation of essential nutrients from the algae test medium necessary for algae growth can clearly limit algae growth even though the effect is not directly associated with intrinsic toxicity of the substance. Thus, it’s important to adapt the test system (e.g. enriched nutrient medium or addition of extra nutrients) in order to minimize effects caused by complexation (see “Guidance on Information Requirements and Chemical Safety Assessment Chapter R.7b: Endpoint specific guidance”; ECHA, 2017).

Two studies are available performed with the source substance tetrasodium EDTA. Both were performed according to EU method C.3 under GLP conditions using the freshwater algae Desmodesmus subspicatus. To take into account the possible negative effects of complexation of nutrients from the algae medium both studies were conducted under different test conditions. In the first study an ErC50 of 2.77 mg/L and an ErC10 of 0.7 mg/L were recorded. The inhibitory effect of Na4-EDTA on the cell multiplication of Scenedesmus subspicatus is likely to be caused by complexing essential ferrous ions from the test medium. This assumption was confirmed in a second study where the simultaneous application of equimolar concentration of FeCl3×6H2O and EDTA up to 263.04 µmol/L (100 mg/L Na4-EDTA) resulted in no inhibition of the algal growth (EC50 (72 h) > 100 mg/L; NOEC (72 h) ≥ 100 mg/L). The addition of additional nutrients to the test medium allowed for normal growth of algae cells. Thus, Na4-EDTA itself has no intrinsic toxicity towards algae.
In conclusion EDTA species are considered to be of low toxicity to aquatic algae based on the available studies.