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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
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
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
mobility
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
mobility
Details on results:
In this open static test system, Daphnia magna exposed to a nominal concentration of 100 mg/L revealed no biological effects in the source substance.
The one-to-one read across is based on chemical similarity, almost identical phys chem profile and comparable response in biological assays. Therefore, the same can be applied to the target substance.
Validity criteria fulfilled:
yes
Conclusions:
Under the given experimental conditions, the source test material showed no aquatic toxicity up to the limit of water solubility. The 24 hour and 48 hour EC50 could not be determined, because it exceeded the maximum solubility of the source test material in reconstituted water (EC50> 100 mg/L). The one-to-one read across is based on chemical similarity, almost identical phys chem profile and comparable response in biological assays. Therefore, the same result can be applied to the target substance.
Executive summary:

Purpose

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

Study design

For this purpose, juvenile Daphnia magna were exposed to an aqueous test material preparation over 48 hours, under defined conditions. The GLP study was performed as a limit test according to OECD TG 202.

The study comprised of four test vessels per concentration and control group containing five daphnids each, i.e. 20 daphnids per concentration (test medium group) and control group.

Daphnids were exposed to a nominal test material concentration of 100 mg/L (limit test) in an open static system.

Results

The follwing results have been obtained:

   

Nominal concentration Immobilization immobilized / exposed

[g/L]  24 hours  48 hours 
0.0  0/20 0/20 
0.1  0/20  0/20 

Daphnia magna exposed to an aqueous preparation of the nominal concentration of 100 mg/L of test item were not affected.

For the test material the following EC50 values for Daphnia magna were determined:

24 h EC50 > 0.1 g/L (nominal)

48 h EC50 > 0.1 g/L (nominal)

Conclusions

Under the given experimental conditions, the test material showed no aquatic toxicity. The 48 -h EC50 was determined to be greater than 100 mg/L. The one-to-one read across is based on chemical similarity, almost identical phys chem profile and comparable response in biological assays. Therefore, the same result can be applied to the target substance.

Description of key information

Read-across, key, acute immobilisation, D. magna, limit test, OECD 202, GLP: EC50 > 100 mg/L (nominal) after 48 h.

Key value for chemical safety assessment

Additional information

Read-across, Acute immobilisation, OECD 202

Purpose

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

Study design

For this purpose, juvenile Daphnia magna were exposed to an aqueous test material preparation over 48 hours, under defined conditions. The GLP study was performed as a limit test according to OECD TG 202.

The study comprised of four test vessels per concentration and control group containing five daphnids each, i.e. 20 daphnids per concentration (test medium group) and control group.

Daphnids were exposed to a nominal test material concentration of 100 mg/L (limit test) in an open static system.

Results

The follwing results have been obtained:

   

Nominal concentration Immobilization immobilized / exposed

[g/L]  24 hours  48 hours 
0.0  0/20 0/20 
0.1  0/20  0/20 

Daphnia magna exposed to an aqueous preparation of the nominal concentration of 100 mg/L of test item were not affected.

For the test material the following EC50 values for Daphnia magna were determined:

24 h EC50 > 0.1 g/L (nominal)

48 h EC50 > 0.1 g/L (nominal)

Conclusions

Under the given experimental conditions, the test material showed no aquatic toxicity. The EC50 value was determined to be greater than 100 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 ecotoxicological data gaps for the target substance with data on the respective source substance.