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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH

The basis for this read-across is the “Read-Across Assessment Framework” (RAAF) (ECHA 2017). The analogue approach is applied. The read-across hypothesis is that the target and the source substances have similar (eco)toxicological and fate properties as a result of structural similarity. According to the RAAF this approach is covered by scenario 2: “Different compounds have the same type of effect(s)”.
“This scenario covers the analogue approach for which the read-across hypothesis is based on different compounds with qualitatively similar properties. For the REACH information requirement under consideration, the property investigated in a study conducted with one source substance is used to predict properties that would be observed in a study with the target substance if it were to be conducted. Qualitatively similar properties or absence of effect are predicted. The predicted property may be similar or based on a worst-case approach” (ECHA 2017) (for details see read-across statement in section 13).

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)

The target and the source substances are waxy solids. Their physical and chemical properties are in the same range. The target and the source substances are of highest purity. Thus, there are no impurities to consider in this read-across approach (for details see read-across statement in section 13).

3. ANALOGUE APPROACH JUSTIFICATION

No indication for a different ecotoxicological mode of action of the source and the target substance is given. This is justified based on structural similarity and similar physical-chemical properties. This is also supported by a profiling performed with the OECD QSAR Toolbox v4.3. As neutral organics the substances are both classified as Basesurface narcotics by the profiler Acute aquatic toxicity MOA by OASIS. Basesurface narcotics are defined as “inert chemicals that are not reactive and do not interact with specific receptors in the organisms” (explanation of profiler Acute aquatic toxicity MOA by OASIS in the OECD QSAR Toolbox v4.3).
Regarding short-term toxicity to invertebrates, a study according to OECD Guideline 202 and GLP is available for the source substance. No adverse effects were observed at the saturated concentration. Therefore, the study was conducted as a limit test at a nominal concentration of 100 mg/L. No toxic effect was observed. Therefore, the EC50 based on mobility was above 100 mg/L.
Additionally, the source substance was tested in a growth inhibition study in algae according to OECD Guideline 201 and GLP. No adverse effects were observed at the saturated concentration. Therefore, the study was conducted as a limit test at a nominal concentration of 100 mg/L. No toxic effect was observed. Therefore, the EC50 based on growth rate was above 100 mg/L.
Based on the given justification the target substance is considered to be also not toxic to aquatic invertebrates and algae at saturated concentration (EC50 > 100 mg/L).

4. DATA MATRIX
for details see read-across statement in section 13
Reason / purpose:
read-across source
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
biomass
Details on results:
- Exponential growth in the control (for algal test): yes
- Any stimulation of growth found in any treatment: yes, the mean growth rates found in the treatments after 24, 48 and 72 h were higher than the mean growth rates in the vehicle control.
Validity criteria fulfilled:
yes
Conclusions:
An aqueous preparation of 100 mg/L (nominal) of the test material revealed no toxic effect in the test system. Analytically, the 72 hours EC50 to Desmodesmus subspicatus could not be determined; it exceeded the maximum solubility of the test material in reconstituted water. The read-across analogue approach is based on similarity in chemical structure, physical-chemical properties, toxicokinetic behaviour and toxicological study results. As a conclusion, it is scientifically justified to fill (eco)toxicological data gaps for the target substance with data on the respective source substance. Therefore, the same result can be applied to the target substance.
Executive summary:

The source substance was tested for toxicity to algae in an acute growth inhibition test according to OECD Guideline 201 following GLP.

Purpose

The purpose of this assay was to identify the aquatic toxicity potential the test material in algea to provide a rational basis for hazard estimation for the test item in aquatic environments.

Study design

The influence of the test material on the growth and growth rate of the green algae species Desmodesmus subspicatus was tested. The study design included one control and one test material group with six replicates, each containing about 100 mL reconstituted water or test medium and 10,000 cells/mL at the start of the experimental phase. The algae were exposed to a filtrate of nominal 100 mg/L and the study was performed as a limit test in an open static test system. The growth was calculated after 24, 48, and 72 hours exposure in the test medium.

Results

The calculation of the water solubility yielded a low value of 0.0004 mg/L. Due to this low water solubility estimate, the the test material concentration in the reconstituted water could not be determined. For the test material, the following EC50 values and no effect concentration for Desmodesmus subspicatus were obtained:

Parameter (0-72h) Growth rate Yield
EC10 (mg/L)
95% confidence interval   
>0.00004 mg/L (nominal >100 mg/L)
n.d.
>0.00004 mg/L (nominal >100 mg/L)
n.d.
EC20 (mg/L)
95% confidence interval
> 0.00004 mg/L (nominal >100 mg/L)
n.d.
> 0.00004 mg/L (nominal >100 mg/L)
n.d.
EC50 (mg/L)
95% confidence interval
> 0.00004 mg/L (nominal >100 mg/L)
n.d.
> 0.00004 mg/L (nominal >100 mg/L)
n.d.
NOEC (mg/L) 0.00004 mg/L (nominal >100 mg/L) 0.00004 mg/L (nominal >100 mg/L)
LOEC (mg/L) >0.00004 mg/L (nominal >100 mg/L) >0.00004 mg/L (nominal >100 mg/L)

n.d.   could not be determined

Conclusions

An aqueous preparation of 100 mg/L (nominal) of the test material revealed no toxic effect in the test system. The 72 hours EC50 exceeded the maximum solubility of the test material in reconstituted water (EC50 > 0.00004 mg/L).

The read-across analogue approach is based on similarity in chemical structure, physical-chemical properties, toxicokinetic behaviour and toxicological study results. As a conclusion, it is scientifically justified to fill (eco)toxicological data gaps for the target substance with data on the respective source substance. Therefore, the same result can be applied to the target substance.

Description of key information

Read-across, key, growth rate inhibition, D. subspicatus, limit test, OECD 201, GLP: EC50 > 100 mg/L (nominal), EC10 > 100 mg/L (nominal) after 72 h.

Key value for chemical safety assessment

Additional information

The source substance was tested for toxicity to algae in an acute growth inhibition test according to OECD Guideline 201 following GLP.

Purpose

The purpose of this assay was to identify the aquatic toxicity potential the test material in algea to provide a rational basis for hazard estimation for the test item in aquatic environments.

Study design

The influence of the test material on the growth and growth rate of the green algae species Desmodesmus subspicatus was tested. The study design included one control and one test material group with six replicates, each containing about 100 mL reconstituted water or test medium and 10,000 cells/mL at the start of the experimental phase. The algae were exposed to a filtrate of nominal 100 mg/L and the study was performed as a limit test in an open static test system. The growth was calculated after 24, 48, and 72 hours exposure in the test medium.

Results

The calculation of the water solubility yielded a low value of 0.0004 mg/L. Due to this low water solubility estimate, the the test material concentration in the reconstituted water could not be determined. For the test material, the following EC50 values and no effect concentration for Desmodesmus subspicatus were obtained:

Parameter (0-72h) Growth rate Yield
EC10 (mg/L)
95% confidence interval   
> 0.00004 mg/L (nominal >100 mg/L)
n.d.
> 0.00004 mg/L (nominal >100 mg/L)
n.d.
EC20 (mg/L)
95% confidence interval
> 0.00004 mg/L (nominal >100 mg/L)
n.d.
> 0.00004 mg/L (nominal >100 mg/L)
n.d.
EC50 (mg/L)
95% confidence interval
> 0.00004 mg/L (nominal >100 mg/L)
n.d.
> 0.00004 mg/L (nominal >100 mg/L)
n.d.
NOEC (mg/L) 0.00004 mg/L (nominal >100 mg/L) 0.00004 mg/L (nominal >100 mg/L)
LOEC (mg/L) > 0.00004 mg/L (nominal >100 mg/L) > 0.00004 mg/L (nominal >100 mg/L)

n.d.   could not be determined

Conclusions

An aqueous preparation of 100 mg/L (nominal) of the test material revealed no toxic effect in the test system. The 72 hours EC50 exceeded the maximum solubility of the test material in reconstituted water (EC50 > 0.00004 mg/L).

The read-across analogue approach is based on similarity in chemical structure, physical-chemical properties, toxicokinetic behaviour and toxicological study results. As a conclusion, it is scientifically justified to fill (eco)toxicological data gaps for the target substance with data on the respective source substance. Therefore the same result can be applied to the target substance.