Registration Dossier

Ecotoxicological information

Toxicity to aquatic plants other than algae

Currently viewing:

Administrative data

Endpoint:
toxicity to aquatic plants other than algae
Type of information:
experimental study
Adequacy of study:
key study
Study period:
not reported
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study
Justification for type of information:
Empirical evidence and environmental dissociation constants of Co substances provide sufficient justification for a category approach for which the read-across hypothesis is based on (bio) transformation to common compound(s) (RAAF Scenario 5). All Co substances transform, at differing rates, to the dissolved Co2+ ion in solution, and assessment of the toxic properties of any substance releasing Co into solution may be predicted by the effects observed in studies conducted with the source substance, CoCl2. See Section 7.0 for a detailed read-across justification statement.
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2007

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 221 (Lemna sp. Growth Inhibition Test)
Deviations:
no
Principles of method if other than guideline:
not applicable
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Cobalt dichloride dihydrate
- Molecular formula (if other than submission substance): CoCl2.2H2O
- All other report endpoints: not reported
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):not applicable

Sampling and analysis

Analytical monitoring:
yes
Details on sampling:
The dissolved cobalt concentrations were determined in each concentration at the beginning and at the end of the exposure period. In chronic tests, the dissolved cobalt concentration in each of the different treatments was determined (in duplicate) in the following samples:exposure medium at the beginning of the test: medium at the start and before the first renewal)exposure medium at the end of the test: (new medium used for the last renewal and at the end of the test)The average of the values observed in “new” media was used for the determination of the different effect concentrations.Analysis of dissolved Co-levels is done as follows: Test media samples are filtered (0.45 µm) and 0.14N HNO3 (ultrapure) is added

Test solutions

Vehicle:
no
Details on test solutions:
Stock solutions of Co were prepared by dissolving CoCl2.6H2O in culture medium (SSI-medium). The tested CoCl2-solutions were prepared 24h prior to the start of the acute test. For each tested concentration, the appropriate amount of SIS-medium (400 mL) was thoroughly mixed with the desired amount of CoCl2 (taken from the Cu-stock solution). The spiked test media were brought into poly-ethylene vessels and stored at 4°C in dark.

Test organisms

Test organisms (species):
Lemna minor
Details on test organisms:
The plants that were used in this study were taken from a laboratory standard culture that has been maintained in the contractors laboratory. Starting material were monocultures, free from contamination by other organisms such as algae and protozoans. Healthy plants of L. minor consisted of colonies comprising between two to five fronds. At least seven days before testing, sufficient colonies were transferred aseptically into fresh sterile medium and cultured for 7-10 days under the conditions of the test.

Study design

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
7 d
Post exposure observation period:
. Changes in plant development (e.g., frond size, appearance, necrosis, chlorosis, root length, morphological changes, etc.) or significant features of the test medium (e.g., algal growth, presence of undissolved material) were also recorded.

Test conditions

Hardness:
not reported
Test temperature:
24 ± 2°C
pH:
6.5 ± 1.5
Dissolved oxygen:
not reported
Salinity:
not reported
Nominal and measured concentrations:
see table 42 below
Details on test conditions:
TEST SYSTEMTest chambers: 500 ml glass jars automatic pipettes (1 and 5 mL)Temperature and pH meterglass pipette (diameter: ± 3 mm) Temperature controlled room (24-25°C)100 mL measuring cylinderBalance4 replicates per concentration, with colonies containing 2 to 4 visible fronds, and with 12 fronds per replicate. The test vessel for each replicate had to be large enough for the fronds of the different colonies in the control vessels to grow without overlapping at the end of the test. Roots were allowed to touch the bottom of the test vessel (required depth: > 20 mm). In practice, the dimensions of the test vessel were 70 cm², with a depth of 8 cm. The volume of test medium was 100 mL. It is important that the number of colonies and fronds were the same in each test vessel. Exposure media were brought into the test vessels 3 hours before transferring the organisms into these cups. During this 3h-period, the vessels were placed in the 25°C temperature controlled room, so that a temperature shock did not occur when plants were transferred. A randomized design for location of the test vessels was required to minimize the influence of spatial differences in light intensity or temperature. GROWTH MEDIUMComposition of the modified SSI-culturing and test medium.Final test medium: 1 L deionised water, containing:•10 mL of stock solution I•5 mL of stock solution II•5 mL of stock solution III•5 mL of stock solution IV•1 mL of stock solution V•5 mL of stock solution VI•1 mL of stock solution VII (MOPS)•+ pH adjustment to 6.5 ± 0.2SubstanceConcentration in stock solution (g/L)Stock solution INaNO38.5KH2PO41.3Stock solution IIMgSO4.7H2O15.0Stock solution IIICaCl2.2H2O7.2Stock solution IVNa2CO34.0Stock solution VH3BO31.0MnCl2.2H2O0.20Na2.MoO4.2H2O0.010ZnSO4.7H2O0.050CuSO4.5H2O0.0050Co(NO3)2.6H2O0.010Stock solution VIFeCl3.6H2O0.17Na2-EDTA.2H2O (1)0.28Stock solution VIIMOPS (buffer)490(1): DOC replaces Na2-EDTA.2H2O that is recommended in the SSI-mediumOTHER TEST CONDITIONSLight-dark cycleContinuous warm or cool white fluorescent lightingIllumination 6500 – 10,000 lux (maximum allowed differences: 15%)EFFECT PARAMETERS At the start and end of the test, frond and colony numbers in the test vessels were counted and recorded, taking care to ensure that overlapping but distinctly visible fronds were not overseen. Intermediate counts of colony numbers and fronds were required on at least two occasions during the 7 day exposure period and at test termination in order to determine specific growth rate at intervals during the exposure period. RANGE-FINDING STUDYnot applicable
Reference substance (positive control):
no

Results and discussion

Effect concentrationsopen allclose all
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
4.9 µg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 2.7-8.7
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
90.1 µg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 69.9-116.1
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
3 µg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Basis for effect:
growth rate
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
8.8 µg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Basis for effect:
growth rate
Details on results:
the observed growth rates (based on the total number of fronds) met control criteria
Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
The derived growth rates for the individual replicates (see Annex B) were used for fitting a logistic concentration-response relation and a 7d-EC10 and EC50 were derived. Individual growth rates were also used for the derivation of a 7d-NOEC and 7d-LOEC-value. All derived effect concentrations (+ 95% confidence limits).

Applicant's summary and conclusion

Conclusions:
The 7d-EC10, based on growth rate, is 4.9 µg Co diss./L (95% CL: 2.7-8.7 µg Co diss./L). The 7d-EC50, based on growth rate, is 90.1 µg Co diss./L (95% CL: 69.9-116.1 µg Co diss./L). The 7d-NOEC, based on growth rate, is 3.0 µg Co diss./L. The 7d-LOEC, based on growth rate, is 8.8 µg Co diss./L.