6-cyclopentylidenehexanal

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

14 May 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

1. SOFTWARE
iSafeRat® High-Accuracy-Quantitative Structure-Activity Relationship (HA-QSAR) based on a holistic approach for predicting physicochemical and ecotoxicological endpoints: Short-term toxicity to Daphnia (immobilisation)

2. MODEL (incl. version number)
iSafeRat® holistic HA-QSAR v1.9

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
SMILES: O=CCCCC/C=C1CCCC/1

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached QMRF

5. APPLICABILITY DOMAIN
See attached QPRF

6. ADEQUACY OF THE RESULT
See attached QPRF

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

not applicable

Remarks:

QSAR model

Principles of method if other than guideline:

The ACUTE TOXICITY TO DAPHNIDS (48-HOUR EC50) was determined using iSafeRat® daphEC50, a validated QSAR model for the Mechanism of Action (MechoA) in question (MechoA 3.1, i.e. hard electrophile) (Bauer et al., 2018). The purpose of this QSAR model is to accurately predict the acute toxicity to daphnids as would be expected in a laboratory experiment following OECD Guideline 202 and EC method C.2. The model provides an in silico prediction for the 48-hour EC50 value that can effectively be used in place of an experimentally derived 48-hour EC50 value. The regression based method used to achieve this has been fully validated following the OECD recommendations (OECD, 2004). The QSAR model is based on validated data for a training set of 5 chemicals derived from 48-hour test on daphnids.

GLP compliance:

no

Remarks:

QSAR model

Specific details on test material used for the study:

- log KOW: 4.18 (Phytosafe, 2013)
- Water Solubility: 17.6 mg/L (KREATiS, 2020)

Analytical monitoring:

no

Details on sampling:

not applicable

Vehicle:

no

Details on test solutions:

not applicable

Test organisms (species):

other: Daphnia magna, Daphnia pulex

Details on test organisms:

No difference in terms of toxic mechanism of action between invertebrate (or indeed other) aquatic species is expected. Any observed differences may be attributed to lifestyle related parameters (e.g. shell closing in molluscs) and relative duration of study versus bodysize rather than to a specific toxic mechanism causing species differences.

Test type:

other: QSAR model

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Remarks on exposure duration:

Results from a test duration of 48 hours only were used for daphnid species.

Post exposure observation period:

not applicable

Hardness:

The QSAR is based on data from studies performed at acceptable hardness to ensure control survival.

Test temperature:

The temperatures varied from approximately 20 to 23 °C depending on the species used to construct the algorithm. This small difference is not expected to contribute to the variability of the EC50 values found in experimental data.

pH:

Test results were taken from studies with measured pHs between 6 - 9.

Dissolved oxygen:

The model is based on data from studies performed at acceptable oxygen concentrations (generally >60%).

Salinity:

not applicable

Conductivity:

not applicable

Nominal and measured concentrations:

Studies were used only where sufficient evidence was presented to determine that the substance was stable under test conditions (i.e. maintained within ± 20 % of the nominal) or, if not, the result was based on measured concentrations as geometric mean.

Details on test conditions:

Preferentially results from semi-static studies were used. However, substances tested using a static design were accepted (preferably accompanied by analytical measurements over the study period). For suspected volatile substances only tests performed in closed vessels were accepted unless accompanying analytical monitoring proved such a design was not necessary.

Reference substance (positive control):

no

Remarks:

QSAR model

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

0.76 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95% confidence interval (α = 0.05): 0.53 – 1.1 mg/L

Details on results:

The test item falls within the applicability domain of the model and was therefore reliably predicted for its acute toxicity (48h-EC50) to daphnids. Therefore, this endpoint value can be considered valid for use in risk assessment and classification and labelling.
The 48h-EC50 of the test item to daphnids was predicted as 0.76 mg/L.

Results with reference substance (positive control):

not applicable

Reported statistics and error estimates:

95% confidence interval (α = 0.05): 0.53 – 1.1 mg/L

Applicability Domain

Descriptor domain

The Subcooled Liquid Water Solubility value (17.6 mg/L or -3.974 in log10 (mol/L)) given as the input to the iSafeRat® daphEC50 model falls within the descriptor domain of the model between a Subcooled Liquid Water Solubility of -5.15 to -0.080 in log10 (mol/L).

Structural fragment domain

All chemical groups within the molecular structure are taken into account by the model.

Mechanistic domain

Currently, the iSafeRat® daphEC50 model can reliably predict the aquatic toxicity for chemicals with the following mechanisms of action of toxicity (MechoA):

• non-polar narcosis (MechoA 1.1)

• polar narcosis of alkyl-/alkoxy-phenols (MechoA 1.2)

• polar narcosis of aliphatic amines (MechoA 1.2)

• cationic narcosis of quaternary ammoniums (MechoA 1.3)

• mono-/poly-esters whose hydrolysis products are narcotics (MechoA 2.1)

• hard electrophile reactivity (MechoA 3.1)

• RedOx cycling of primary thiols (MechoA 4.4)

• Proton release of carboxylic acids (MechoA 5.2)

The MechoA of molecules is predicted directly from the structure. The test item as an aldehyde is expected to exert a MechoA 3.1 and can be taken into account by the model (Bauer et al., 2018).

Validity criteria fulfilled:

yes

Conclusions:

The test item falls within the applicability domain of the model and was therefore reliably predicted for its acute toxicity (48h-EC50) to daphnids. Therefore, this endpoint value can be considered valid for use in risk assessment and classification and labelling.
The 48h-EC50 of the test item to daphnids was predicted as 0.76 mg/L.
95% confidence interval (α = 0.05): 0.53 - 1.1 mg/L.

Executive summary:

A Quantitative Structure-Activity Relationship (QSAR) model was used to calculate the ACUTE TOXICITY TO DAPHNIDS (48-HOUR EC50) of the test item. This QSAR model has been validated to be compliant with the OECD recommendations for QSAR modeling (OECD, 2004a) and predicts the endpoint value which would be expected when testing the substance under experimental conditions in a laboratory following the Guideline for Testing of Chemicals No. 202, "Daphnia sp., Acute Immobilisation Test" (OECD, 2004b), referenced as Method C.2 of Commission Regulation No. 440/2008 (European Commission, 2008). The criterion predicted was the EC50 (Median Effective Concentration), a statistically derived concentration which is expected to cause immobility in 50%

of test animals within a period of 48 hours.

The ACUTE TOXICITY TO DAPHNIDS (48-HOUR EC50) was determined using iSafeRat® daphEC50, a validated QSAR model for the Mechanism of Action (MechoA) in question (MechoA 3.1, i.e. hard electrophile reactivity) (Bauer et al., 2018). The QSAR model is based on validated data for a training set of 5 chemicals derived from 48-hour test on daphnids, for which the concentrations of the test item had been determined by chemical analyses over the test period.

The test item falls within the applicability domain of the model and was therefore reliably predicted for its acute toxicity (48h-EC50) to daphnids. Therefore, this endpoint value can be considered valid for use in risk assessment and classification and labelling.

The 48h-EC50 of the test item to daphnids was predicted as 0.76 mg/L.

95% confidence interval (α = 0.05): 0.53 - 1.1 mg/L.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

disregarded due to major methodological deficiencies

Study period:

From May 21, 2013 to May 28, 2013

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Remarks:

This study was performed according to OECD Guideline 202 with GLP certificate. All validity criteria were fulfilled. However, this study is not reliable due to high concentration of solvent used. Indeed, a large quantity of acetone was used as solvent in this study. Because of the potential for interaction with the test chemical resulting in an altered response in the test, solvent use should be restricted to situations where no other acceptable method of test solution preparation is available. The use of solvent is not the best method at the time being. In addition, the concentration/quantity of solvent used in the treatment solutions was 5 mL/L , corresponding to 3.95 g/L (with a density of 0.79), which is 50 times higher than the recommended maximum level of solvent (below 0.1 mL/L; OECD No. 23) and represent almost half of the EC50 of acetone (which was reported in the ECHA disseminated dossier at 8.8 g/L). Acetone is suspected to have affected the definitive results. Some solvent/substance interactions may have occurred in this study with this high concentration of acetone.

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

April 2004

Deviations:

yes

Remarks:

Solvent was used, which is not the best method existing at the time being.

GLP compliance:

yes (incl. QA statement)

Remarks:

Inspection date on 14 June 2012 / GLP certificate signed on 10 January 2013

Specific details on test material used for the study:

- Storage condition: Room temperature protected from direct sun light

Analytical monitoring:

yes

Details on sampling:

The test item concentrations were measured before and after each renewal/adjustment.

Vehicle:

yes

Remarks:

acetone

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The treatment solutions were prepared in acetone. Information concerning the preparation of the test item treatments is given in Table 6.1.1/1 in "Any other information on materials and methods incl. tables".
- Controls: water controls (the control tubes received 10 mL of M4 mineral medium) and solvent control (another set of 4 replicate tubes received 0.05 mL of acetone alone so as to ascertain that the vector had no adverse effects towards daphnids.
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): acetone
- Concentration of vehicle in test medium (stock solution and final test solution(s) or suspension(s) including control(s)): 5 mL/L
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): not reported

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Strain/clone: Daphnia magna
- Source: received from a commercial breeder. These organisms were regularly sub-cultured at the Phytosafe site and fed with living cells of the green algae.
- Age of parental stock (mean and range, SD): Young daphnids produced within 24 hours were used for the tests.
- Feeding during test: Daphnids were not fed during the exposure period.

Test type:

semi-static

Water media type:

freshwater

Remarks:

M4 mineral medium

Limit test:

no

Total exposure duration:

48 h

Hardness:

64.8 mg/L of NaHCO3 in the reconstituted water.

Test temperature:

The temperature conditions were checked to be 20°C kept constant at +/- 1°C for both the range-finding test and the definitive test.

pH:

7.5 to 8.1. Both the initial and the final values for pH were silimar to the controls for every test item treatments.

Dissolved oxygen:

80.2 to 87.3 %. In every case the final oxygen concentration represented more than 80% of the saturation level.

Salinity:

Not applicable

Nominal and measured concentrations:

- Nominal treatment concentrations: 1.0, 2.1, 4.1, 8.2 and 16.4 mg/L.
- Measured concentrations: See table 6.1.1/2 in "Any other information on results incl. tables".
The initial concentrations did not deviate by more than 7% from the nominal values. After 24 hours of testing the measured concentrations were decreased down to 76-88% of the nominal values and the daphnids were transferred into newly prepared test tubes. At the end of test, the measured concentrations represented 42-81% of the nominal values. Based on mean measured concentrations over each successive period, and duration of each successive period, mean exposure concentrations were calculated as 0.8 - 1.6 - 3.5 - 7.1 and 15.0 mg/L.

Details on test conditions:

TEST SYSTEM
- Test vessel: 15 mL capacity glass tubes
- Type (delete if not applicable): The tubes were maintained at dark in a climatic chamber, and were tightly capped during the exposure period so as to avoid volatilization of the test item. The controls were conducted accordingly.
- Material, size, headspace, fill volume: filled with 10 mL of M4 mineral medium
- Renewal rate of test solution (frequency/flow rate): semi-static methodology. The daphnids were transferred into newly prepared test tubes after 24 hours of exposure for the test item treatments, the water controls and the solvent controls.
- No. of organisms per vessel: 5 daphnids per replicate unit
- No. of vessels per concentration (replicates): 4 replicate units
- No. of vessels per control (replicates): 4 replicate units
- No. of vessels per vehicle control (replicates): 4 replicate units

TEST MEDIUM / WATER PARAMETERS
The M4 mineral medium was freshly reconstituted from mineral stock solutions.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Each test tube was checked for immobilized daphnids 24 and 48 hours after the start of the test. Any abnormal behavior or appearance, if any, was reported.

VEHICLE CONTROL PERFORMED: yes

RANGE-FINDING STUDY
- Test concentrations: 0.04 - 0.20 - 1.0 - 5.1 and 25.3 mg/L
- Results used to determine the conditions for the definitive study: No immobilization was observed throughout the test period for the water control and the solvent control. That was also the case for both the 0.04 and 1.0 mg/L test item treatments. At 0.20 mg/L one daphnid died on day 2 but the phenomenon was not confirmed at 1.0 mg/L and was not taken as a treatment induced effect. All the daphnids were immobilized after 24 hours of testing at 25.3 mg/L. The 5.1 mg/L test item treatment gave intermediate results.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

2.4 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95% confidence interval : 1.3 - 4.6 mg/L

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

1.6 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

See table 6.1.3/3 in "Any other information on results incl. tables".

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- ECx: 24h-EC50 for Potassium dichromate fell within 0.6 - 2.1 mg/L. Calculation gave 1.34 mg/L as the measured value.

Table 6.1.3/2 : Measured concentrations for the test substance (mg/L) throughout the test period

Nominal values	Day 1		Day 2
	New media	Old media	New media	Old media
1.0  mg/L 2.1 mg/L 4.1 mg/L 8.2 mg/L 16.4 mg/L	1.03 2.09 4.40 7.88 16.37	0.78 1.58 3.60 7.02 13.74	1.08 2.12 4.14 8.15 17.09	0.44 0.87 2.21 5.79 13.30

Table 6.1.3/3 : Definitive test - % immobilized daphnids for the controls and the test item treatments

		% immobilization after 24 hours				% immobilization after 48 hours
		Rep 1	Rep 2	Rep 3	Rep 4	Rep 1	Rep 2	Rep 3	Rep 4
Water control		0	0	0	0	20	0	0	0
Solvent control		0	0	0	0	0	0	0	0
Test substance	0.8 mg/L 1.6 mg/L 3.5 mg/L 7.1 mg/L 15.0 mg/L	0 20 20 40 60	0 0 40 20 40	0 20 20 40 60	0 0 20 20 60	0 40 80 100 100	0 40 60 100 100	0 40 80 80 100	0 0 80 80 100

Validity criteria fulfilled:

yes

Remarks:

Immobilization was less than 10% in the controls; the dissolved oxygen concentration exceeded 3 mg/L in the controls and every test item treatment; the 24h-EC50 for potassium dichromate was between 0.6 and 2.1 mg/L.

Conclusions:

The 48h-EC50 value was determined at 2.4 mg/L, with a 95% CI of 1.3 - 4.6 mg/L, based on geometric mean measured concentrations.
Even if all validity criteria were fulfilled, this study is not reliable due to high concentration of solvent used.

Executive summary:

This study was performed according to OECD Guideline 202 with GLP statement, to assess the acute toxicity of the test substance to aquatic invertebrates Daphnia magna.

Following a preliminary range-finding study, 5 daphnids per replicate unit (4 replicate units per treatment) were exposed to the test item (prepared with acetone as solvent) at nominal concentrations of 1.0 - 2.1 - 4.1 - 8.2 and 16.4 mg/L, corresponding to geometric mean measured concentrations of 0.8 - 1.6 - 3.5 - 7.1 and 15.0 mg/L, for 48 hours under semi-static test conditions. The number of immobilised Daphnia was recorded after 24 and 48 hours.

Based on geometric mean measured concentrations, the 48 hour EC50 for the test item to Daphnia magna was 2.4 mg/L with 95% confidence limits of 1.3 - 4.6 mg/L. The highest tested concentration without observed effect was 1.6 mg/L.

Even if all validity criteria were fulfilled, this study is not reliable due to high concentration of solvent used. Indeed, a large quantity of acetone was used as solvent in this study. Because of the potential for interaction with the test chemical resulting in an altered response in the test, solvent use should be restricted to situations where no other acceptable method of test solution preparation is available. The use of solvent is not the best method at the time being. In addition, the concentration/quantity of solvent used in the treatment solutions was 5 mL/L , corresponding to 3.95 g/L (with a density of 0.79), which is 50 times higher than the recommended maximum level of solvent (below 0.1 mL/L; OECD No. 23) and represent almost half of the EC50 of acetone (which was reported in the ECHA disseminated dossier at 8.8 g/L). Acetone is suspected to have affected the definitive results. Some solvent/substance interactions may have occurred in this study with this high concentration of acetone.

Description of key information

iSafeRat® High-Accuracy-Quantitative Structure-Activity Relationship, KREATIS, 2020 :

48h-EC50 = 0.76 mg/L (95% confidence interval: 0.53 - 1.1 mg/L)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.76 mg/L

Additional information

One experimental study and one QSAR prediction are available to assess the short-term toxicity of the registered substance to aquatic invertebrates.

The experimental study (Phytosafe, 2013) was considered as not reliable and was disregarded due to major methodological deficiencies. Indeed, a large quantity of acetone was used as solvent in this study. Because of the potential for interaction with the test chemical resulting in an altered response in the test, solvent use should be restricted to situations where no other acceptable method of test solution preparation is available. The use of solvent is not the best method at the time being. In addition, the concentration/quantity of solvent used in the treatment solutions was 5 mL/L , corresponding to 3.95 g/L (with a density of 0.79), which is 50 times higher than the recommended maximum level of solvent (below 0.1 mL/L; OECD No. 23) and represent almost half of the EC50 of acetone (which was reported in the ECHA disseminated dossier at 8.8 g/L). Therefore, solvent/substance interactions may have occured in this study with this high concentration of acetone and the result cannot be considered fit for use.

The QSAR prediction (KREATiS, 2020) was considered as reliable. The QSAR model has been validated to be compliant with the OECD recommendations for QSAR modelling (OECD, 2004) and predicts the endpoint value which would be expected when testing the substance under experimental conditions in a laboratory following OECD Guideline 202.The immobility of the daphnids was determined using a validated QSAR model for the Mechanism of Action (MechoA) in question (MechoA 3.1, i.e. hard electrophile reactivity) (Bauer et al., 2018). The QSAR model is based on validated data for a training set of 5 chemicals derived from 48 -hour test on daphnids, for which the concentrations of the test item had been determined by chemical analyses over the test period. The test item falls within the applicability domain of the model and was therefore reliably predicted for its acute toxicity (48h-EC50) to daphnids. Therefore, this endpoint value can be considered valid for use in risk assessment and classification and labelling.

The 48-h EC50 of the registered substance to daphnids was predicted at 0.76 mg/L (95% CI: 0.53 - 1.1 mg/L).