6-cyclopentylidenehexanal

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

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® toolbox – in Silico Algorithms For Environmental Risk And Toxicity version 2.4

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

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
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 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Deviations:

not applicable

Remarks:

QSAR model

Principles of method if other than guideline:

The TOXICITY TO ALGAE (72-HOUR ErC50 and NOECr) was determined using iSafeRat® algEC50, 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 6 chemicals derived from 72-hour ErC50, for which the concentrations of the test item had been determined by chemical analyses over the test period. The QSAR model for 72-hour NOECr was not applicable for the test item due to the limitation of the mechanistic domain.

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: Pseudokirchneriella subcapitata, Desmodesmus subspicatus, Scenedesmus quadricauda

Details on test organisms:

No difference in terms of toxic mechanism of action between algae (or indeed other) aquatic species is expected. Any observed differences may be attributed to lifestyle related parameters and relative duration of study versus cell size 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:

72 h

Remarks on exposure duration:

Results from a test duration of 72 hours only were used for this algorithm.

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 25 °C depending on the species used to construct the models. This small difference is not expected to significantly contribute to the variability of the values found in experimental data.

pH:

Test results were preferably taken from studies with measured pHs between 6 - 9. However it is recognized that in some cases (due to high luminosity) the pH may increase in the control and lower concentrations (which do not cause significant effect over the study period). This pH increase did not generally disqualify the study from being used in the test and validation set for non-polar chemicals.

Dissolved oxygen:

The temperatures varied from approximately 20 to 25 °C depending on the species used to construct the algorithm. This small difference is not expected to contribute to the variability of the ErC50 values found in experimental data.

Salinity:

not applicable

Conductivity:

no data

Nominal and measured concentrations:

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

Details on test conditions:

Following the guideline OECD 201, all studies were from a static test design. 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:

72 h

Dose descriptor:

EC50

Effect conc.:

0.2 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% confidence interval (α = 0.05) for 72h-ErC50: 0.080 – 0.51 mg/L

Details on results:

The test item falls at least within the applicability domain of the iSafeRat® algErC50 and was therefore reliably predicted for its TOXICITY TO ALGAE (72-HOUR ErC50 and NOECr). Therefore, this endpoint value can be considered valid for use in risk assessment and classification and labelling.

Results with reference substance (positive control):

not applicable

Reported statistics and error estimates:

95% confidence interval (α = 0.05) for 72h-ErC50: 0.080 – 0.51 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® algErC50 model falls within the descriptor domain of the model between a Subcooled Liquid Water Solubility of -5.15 to -0.82 in log10 (mol/L).

Structural fragment domain

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

Mechanistic domain

Currently, the iSafeRat® algErC50 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 iSafeRat® algNOECr model can only reliably predict the aquatic toxicity for chemicals with the mechanism of action of non-polar narcosis (MechoA 1.1).

The MechoA of molecules is predicted directly from the structure. The test item as an aldehyde is expected to exert a MechoA 3.1 (Bauer et al., 2018) and can only be taken into account by the iSafeRat® algErC50 model.

Validity criteria fulfilled:

yes

Conclusions:

The QSAR models used to achieve the study have been fully validated following the OECD recommandations (OECD, 2004). The test item falls at least within the applicability domain of the iSafeRat® algErC50 and was therefore reliably predicted for its TOXICITY TO ALGAE (72-HOUR ErC50 and NOECr). Therefore, this endpoint value can be considered valid for use in risk assessment and classification and labelling.

The 72h-ErC50 of the test item to algae was predicted as 0.20 mg/L.
The 72h-NOECr of the test item to algae was not predicted.
95% confidence interval (α = 0.05) for 72h-ErC50: 0.080 – 0.51 mg/L.
95% confidence interval (α = 0.05) for 72h-NOECr: not determined.

Executive summary:

Two Quantitative Structure-Activity Relationship (QSAR) models were used to calculate the TOXICITY TO ALGAE (72-HOUR ErC50 and NOECr) of the test item. These QSAR models have been validated to be compliant with the OECD recommendations for QSAR modeling (OECD, 2004) and predict the endpoint values which would be expected when testing the substance under experimental conditions in a laboratory following the Guideline for Testing of Chemicals No. 201, "Freshwater Alga and Cyanobacteria, Growth Inhibition Test" (OECD, 2006), referenced as Method C.3 of Commission Regulation No. 440/2008 (European Commission, 2008). The criterions predicted were the Median Effective Concentration (ErC50), a statistically derived concentration which is expected to cause 50% inhibition of intrinsic rate of growth of the test system and the No Observed Effect Concentration (NOECr), a tested concentration which is expected to cause no effect on intrinsic rate of growth of the test system. Both criterions were determined for a period exposure of 72 hours.

The TOXICITY TO ALGAE (72-HOUR ErC50 and NOECr) was determined using iSafeRat® algEC50, 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 6 chemicals derived from 72-hour ErC50, for which the concentrations of the test item had been determined by chemical analyses over the test period. The QSAR model for 72-hour NOECr was not applicable for the test item due to the limitation of the mechanistic domain.

The QSAR models used to achieve the study have been fully validated following the OECD recommandations (OECD, 2004). The test item falls at least within the applicability domain of the model iSafeRat® algErC50 and was therefore reliably predicted for its TOXICITY TO ALGAE (72-HOUR ErC50 and NOECr). Therefore, this endpoint value can be considered valid for use in risk assessment and classification and labelling.

The 72h-ErC50 of the test item to algae was predicted as 0.20 mg/L.

The 72h-NOECr of the test item to algae was not predicted.

95% confidence interval (α = 0.05) for 72h-ErC50: 0.080 – 0.51 mg/L.

95% confidence interval (α = 0.05) for 72h-NOECr: not determined.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

disregarded due to major methodological deficiencies

Study period:

From May 17, 2013 to May 31, 2013

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Remarks:

This study was performed according to OECD Guideline 201 with GLP certificate. All validity criteria were fulfilled. However, this study is considered not reliable due to the very high range of confidence interval reported for the EC50 value (95% CI: 0.0 - 217.9 mg/L). In addition, insufficient information was provided on the semi-static methodology used. A validation study should be provided to validate this method and, at the time being, a semi-static system is not accepted as an adaptation of the OECD Guideline. With this method, parent and degradation products are present simultaneously, so interactions can occured. In addition, 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 0.5 mL/L, corresponding to 395 mg/L (with a density of 0.79), which is 5 times higher than the recommended maximum level of solvent (below 0.1 mL/L; OECD No. 23) but is below the NOEC of acetone (which was reported in the ECHA disseminated dossier at 530 mg/L). Finally, only 3 control replicates were used, instead of the recommendation of 6 replicates.

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

March 2006

Deviations:

yes

Remarks:

Semi-static design not clearly explained; solvent used falsifying measurement of exposure values at each solution replacement; only 3 replicates in control; very high range of confidence interval reported for the EC50 value.

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

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 controls consisted of 100 mL of mineral medium) and solvent control (the solvent controls received the same volume of acetone as used for the test item treatments and the same amount of acetone as required for the semi-static methodology with the test item treatments).
- 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)): 0.5 mL/L
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): not reported

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Strain: No.72
- Source (laboratory, culture collection): Museum d'histoire naturelle (Paris,France). The strain was regularly sub-cultured in OECD medium at the Phytosafe site.
- Method of cultivation: the inoculum culture was prepared 2-4 days before the start of the test and incubated under the same conditions as the test cultures

ACCLIMATION
- Culturing media and conditions (same as test or not): the inoculum culture was prepared 2-4 days before the start of the test and incubated under the same conditions as the test cultures such to adapt the test algae to test conditions and ensure that the algae were in the exponential growth phase when used to inoculate the test solutions.

Test type:

semi-static

Water media type:

freshwater

Remarks:

OECD medium (OECD TG 201, according to ISO 8692)

Limit test:

no

Total exposure duration:

72 h

Hardness:

50 mg/L as NaHCO3 in the reconstituted water.

Test temperature:

The temperature was set in the range of 21° to 24°C and kept constant to within +/- 2°C.

pH:

from 7.9 to 8.8
The initial pH value was within the range 7.9-8.2 for the controls and every test item treatments at test initiation. At the end of the test the pH value of the test media was similar to that of the controls for the three lowest test item treatments. At both 1.5 and 3.2 mg/L reduced final pH values confirmed that algae growth was inhibited.

Salinity:

Not applicable

Nominal and measured concentrations:

- Nominal treatment concentrations: 0.3, 0.5, 1.0, 2.0 and 4.0 mg/L.
- Measured concentrations: See table 6.1.1/2 in "Any other information on results incl. tables".
Successive analytical verifications showed that the test item concentrations were not maintained within 80-120% of the nominal values throughout the test period even though the test media were adjusted twice per day. Nevertheless, decrease of the test item treatments was reproductible: the loss of material was approximately 10-15% over a 9h-period, and 30-40% over a 15h-period. Based on mean measured concentration over each successive period, and duration of each successive period, the actual test concentrations were calculated as 0.2, 0.4, 0.8, 1.5 and 3.2 mg/L.

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass Erlenmeyer flasks of 250 mL capacity
- Type (delete if not applicable): closed : the test vessels were capped with air-permeable stoppers
- Material, size, headspace, fill volume: flasks filled with 100 mL of culture
- Renewal rate of test solution (frequency/flow rate): Due to the high instability of the test item in water, it was anticipated that the test item treatments will not remain within 80-120 % of the nominal values. As a consequence, the test item treatments were set at 120% of the nominal values and the treatments were adjusted twice per day. Mean exposure concentrations were further calculated as the geometric mean of the measured concentrations in the old and new media throughout the test period.
- Initial cells density: The initial biomass in the test cultures was the same in all test cultures and sufficiently low to allow exponential growth throughout the incubation period without any risk of nutrient depletion. Historical data at Phytosafe site show that 2 to 5 x 10^3 cells/mL is an appropriate number.
- No. of vessels per concentration (replicates): 3 replicates for each the five test item treatments
- No. of vessels per control (replicates): 3 replicate units for the water control, for the solvent control and for each of five test item treatments

GROWTH MEDIUM
- Standard medium used: yes,OECD medium (OECD TG 201, according to ISO 8692) was freshly reconstituted by dilution of mineral stock solutions in pure water.

OTHER TEST CONDITIONS
- Photoperiod: continuous uniform fluorescent illumination
- Light intensity and quality: 60-120 µE.m^-2.s^-1. The light intensity did not deviate by more than 15% from the average light intensity over the incubation area.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : The algal biomass in each flask was determined daily over the test period using small volumes removed from the test solution by pipette. These volumes were not replaced. The numeration was done using an electronic cell counter. The results were expressed as cells per liter of solution.
The inoculum culture was examined microscopically to verify that it was normal and healthy in appearance and to detect any abnormal appearance of the algae (as may be caused by exposure to the test substance) at the end of the test.

TEST CONCENTRATIONS
- Range finding study : yes
- 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 adverse effects were observed in the solvent control and the test item treatments up to and including 1.0 mg/L. Both specific growth rate and yield were reduced at 5.1 and 25.3 mg/L.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

2.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CI = 0.0 - 217.9 mg/L

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.4 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

See tables 6.1.1/3 and 4 in "Any other information on results incl. tables".
The cells appeared healthy in the controls and the test item treatments. The growth was solely inhibited without any abnormal appearance.
The specific growth rate was regular in both the water controls and the solvent controls throughout the test period. The standard deviation between the three replicate units did not exceed 8% of the mean value at each sampling time and was less than 2% for the average specific growth rate per day over the entire test period.
On the first day of testing mean specific growth rate was significantly reduced at 0.8, 1.5 and 3.2 mg/L. A slight reduction was observed for the 0.2 mg/L test item treatment but this was not confirmed at 0.4 mg/L.
On the second day of testing, mean specific growth rate was significantly reduced for the sole 3.2 mg/L test item treatment and similar to the water controls in every other cases.
On the third day of testing, mean specific growth rate was significantly reduced for the two highest test item treatment but similar to the water controls for the solvent controls and the three lowest test item treatments.
For the entire test period, mean specific growth rate per day was considered as significantly reduced at 0.8, 1.5 and 3.2 mg/L but similar to the water controls for the solvent controls and the two lowest test item treatments (0.2 and 0.4 mg/L).

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- EC50: EC50 for specific growth rate between 0.6 and 1.0 mg/L. Calculation gave 0.87 mg/L as the measured value.

Reported statistics and error estimates:

F-variance analysis at a 5% confidence level was used to judge the difference for mean specific growth rate (section-by-section and total values) for each test item treatment compared to the water controls.
The regression was performed using the three highest test item treatments. The two lowest values were excluded because of the plateau phase. The coefficient of determination was 90.9%.

Table 6.1.5/2: Mean measured concentrations of the test substance in the test item treatments and % of the nominal values

	Nominal treatment concentrations (mg/L)
	0.25	0.51	1.01	2.02	4.04
Initial (T0)	0.28 109.9%	0.57 112.0%	1.15 113.3%	2.41 119.1%	4.36 107.8%
T0+7h – Old media	0.20 78.8%	0.41 80.5%	0.82 81.4%	1.68 82.9%	3.49 86.3%
T0+7h – New media	0.26 103.4%	0.58 114.7%	1.13 111.8%	2.15 106.3%	4.47 110.5%
T0+22h – Old media	0.10 38.3%	0.23 45.9%	0.47 46.9%	0.79 39.1%	1.81 44.7%
T0+22h – New media	0.32 127.4%	0.72 142.5%	1.51 149.7%	2.64 130.8%	5.59 138.2%
T0+31h – Old media	0.21 83.8%	0.50 99.0%	1.07 105.9%	2.14 105.8%	4.42 109.4%
T0+46h – Old media	0.03 11.3%	0.12 23.0%	0.30 30.1%	0.96 47.3%	1.78 44.0%
T0+46h – New media	0.33 131.1%	0.65 127.8%	1.17 115.5%	2.11 104.5%	5.05 124.9%
T0+55h – Old media	0.10 38.4%	0.22 44.3%	0.44 43.3%	1.08 53.6%	2.64 65.4%
T0+55h – New media	0.19 77.0%	0.45 88.9%	0.72 70.8%	1.80 89.3%	3.39 83.9%
T0+72h	0.13 50.9%	0.26 52.0%	0.75 74.2%	1.08 53.5%	2.25 55.6%
Geometric mean	0.2 mg/L	0.4 mg/L	0.8 mg/L	1.5 mg/L	3.2 mg/L

Table 6.1.5/3: Definitive test - Measured specific growth rates per day (section-by-section and total)

	0 to 24h	24 to 48h	48 to 72h	Total period
Water control
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.62 1.71 1.58 1.64±0.06	1.75 1.51 1.56 1.60±0.12	1.92 1.96 2.13 2.00±0.11	1.76 1.72 1.76 1.75±0.02
Solvent control
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.36 1.59 1.66 1.54±0.16	1.87 1.45 1.68 1.67±0.21	1.99 2.10 1.99 2.03±0.07	1.74 1.72 1.78 1.74±0.03
Test substance, 0.2 mg/L
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.41 1.50 1.41 1.44±0.05	1.69 1.84 1.82 1.79±0.08	2.04 1.97 1.93 1.98±0.06	1.72 1.77 1.72 1.74±0.03
Test substance, 0.4 mg/L
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.43 1.66 1.47 1.52±0.12	1.95 1.70 1.75 1.80±0.14	1.85 1.88 2.00 1.91±0.08	1.75 1.75 1.74 1.74±0.00
Test substance, 0.8 mg/L
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.40 1.40 1.55 1.45±0.09	1.75 1.92 1.81 1.83±0.09	1.90 1.77 1.80 1.82±0.07	1.68 1.70 1.72 1.70±0.02
Test substance, 1.5 mg/L
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.31 1.51 1.36 1.39±0.11	1.49 1.49 1.45 1.48±0.02	1.32 1.34 1.49 1.39±0.10	1.37 1.45 1.44 1.42±0.04
Test substance, 3.2 mg/L
Replicate 1 Replicate 2 Replicate 3 Mean±SD	0.83 0.71 0.77 0.77±0.06	0.66 0.76 0.61 0.68±0.07	-0.29 -0.29 -0.25 -0.28±0.02	0.40 0.39 0.38 0.39±0.01

Table 6.1.5/4 : Definitive test - Percentages inhibition of specific growth rates per day (section-by-section and total)

	0 to 24h	24 to 48h	48 to 72h	Total period
Solvent control	6.0%	-3.9%	-1.2%	0.2%
0.2 mg/L	11.9%	-11.3%	1.1%	0.7%
0.4 mg/L	7.0%	-12.3%	4.7%	0.2%
0.8 mg/L	11.2%	-13.9%	8.9%	2.6%
1.5 mg/L	14.8%	7.9%	30.8%	18.8%
3.2 mg/L	52.8%	57.9%	113.9%	77.7%

Negative values indicate that the growth rate was increased as compared to the controls.

Validity criteria fulfilled:

yes

Remarks:

See "Overall remarks"

Conclusions:

Based on specific growth rate, the 72h-NOEC and 72h-ErC50 values were determined at 0.4 and 2.1 mg/L (95% CI: 0.0 - 217.9 mg/L), respectively, based on geometric mean measured concentrations.
This study is considered not reliable due to the very high range of confidence interval reported for the ErC50 value and the insufficient information provided on the semi-static methodology used.

Executive summary:

This study was performed according to OECD Guideline 201 with GLP statement to assess the effect of the test substance on the growth of Desmodesmus subspicatus.

Following a preliminary range-finding study, Desmodesmus subspicatus was exposed to the test material (prepared with acetone as solvent) at a nominal concentrations of 0.3, 0.5, 1.0, 2.0 and 4.0 mg/L for 72 hours, under continuous uniform fluorescent illumination at a temperature of 21 -24 +/- 2°C and semi-static methodology.

Due to the high instability of the test item in water, the test item treatments were not maintained within 80-120% of the nominal value during the test period even though the test item treatments were set at 120% of the nominal values and the treatments were adjusted twice per day. The calculations were based on the geometric mean of the measured concentrations during the test period in the old and the new media: 0.2, 0.4, 0.8, 1.5 and 3.2 mg/L.

Exposure of Desmodesmus subspicatus to the test material gave 72h-ErC50 value of 2.1 mg/L [95% CI = 0.0 - 217.9 mg/L] and 72h-NOEC of 0.4 mg/L, based on specific growth rate and geometric mean measured concentrations.

All validity criteria were fulfilled. However, this study is considered not reliable due to the very high range of confidence interval reported for the EC50 value [95% CI: 0.0 - 217.9 mg/L]. In addition, insufficient information was provided on the semi-static methodology used. A validation study should be provided to validate this method and, at the time being, a semi-static system is not accepted as an adaptation of the OECD Guideline. With this method, parent and degradation products are present simultaneously, so interactions can occured. In addition, 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 0.5 mL/L, corresponding to 395 mg/L (with a density of 0.79), which is 5 times higher than the recommended maximum level of solvent (below 0.1 mL/L; OECD No. 23) but is below the NOEC of acetone (which was reported in the ECHA disseminated dossier at 530 mg/L). Finally, only 3 control replicates were used, instead of the recommendation of 6 replicates.

Description of key information

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

72h-ErC50 = 0.20 mg/L (95% confidence interval: 0.080 - 0.51 mg/L)

Key value for chemical safety assessment

EC50 for freshwater algae:

0.2 mg/L

Additional information

One experimental study and one QSAR prediction are available to assess the toxicity of the registered substance to aquatic algae.

The experimental study (Phytosafe, 2013) was considered as not reliable due to the very high range of the confidence interval reported for the ErC50 value (2.1 mg/L with 95% CI: 0.0 - 217.9 mg/L) and was disregarded due to major methodological deficiencies. Indeed, insufficient information was provided on the semi-static methodology used. A validation study should be provided to validate this method and, at the time being, a semi-static system is not accepted as an adaptation of the OECD Guideline. With this method, parent and degradation products are present simultaneously, so interactions can occured. In addition, 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 0.5 mL/L, corresponding to 395 mg/L (with a density of 0.79), which is 5 times higher than the recommended maximum level of solvent (below 0.1 mL/L; OECD No. 23) but is below the NOEC of acetone (which was reported in the ECHA disseminated dossier at 530 mg/L).

The QSAR prediction (KREATiS, 2020) was considered as reliable and was used as key data. Two QSAR models have been validated to be compliant with the OECD recommendations for QSAR modelling (OECD, 2004) and predict the endpoint values which would be expected when testing the substance under experimental conditions in a laboratory following OECD Guideline 201: 72h-ErC50 and NOECr values. The toxicity to algae was determined using iSafeRat® algEC50 only, 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 6 chemicals derived from 72-hour ErC50, for which the concentrations of the test item had been determined by chemical analyses over the test period. The QSAR model for 72-hour NOECr was not applicable for the test item due to the limitation of the mechanistic domain. The test item falls at least within the applicability domain of the model iSafeRat® algErC50. Therefore, the prediction 72h-ErC50 endpoint value can be considered valid for use in risk assessment and classification and labelling.

The 72h-ErC50 of the test item to algae was predicted at 0.20 mg/L (95% CI: 0.080 - 0.51 mg/L).

The 72h-NOECr of the test item to algae was not predicted.