6,8-dimethylnon-7-enal

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:

October 18th, 2019

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 v1.8

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
O=CCCCCC(C)C=C(C)C
The toxicity of the test item was predicted using the iSafeRat® Ecotox module providing the Subcooled Liquid Water Solubility (SLWS) as the input. The SLWS has been predicted using the iSafeRat® Water Solubility module providing the experimental log KOW value as the input. Water Solubility of the test item = 40.2 mg/L (or -3.622 in log (mol/L).

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 purpose of this QSAR model is to accurately predict the toxicity to algae as would be expected in a laboratory experiment following the OECD Guideline 201 and EC method C.3 for specific, named mechanisms of action. The model provides an in silico prediction for the 72-hour ErC50 value that can effectively be used in place of an experimentally derived 72-hour ErC50 value. The regression is method used to achieve this has been fully validated following the OECD (2004) recommendations.

GLP compliance:

no

Remarks:

QSAR model

Specific details on test material used for the study:

- log KOW = 3.87 (Phytosafe, 2008, EU Method A.8, Flask Method)
- Water Solubility 40.2 mg/L (KREATiS, 2019)
- Mechanism of action: MechoA 3.1: hard electrophiles (Bauer et al., 2018)

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:

None

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 algorithm. This small difference is not expected to contribute to the variability of the ErC50 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.:

0.43 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95%CL: 0.18 - 1.0 mg/L

Details on results:

The test item falls within the applicability domain of the model and was therefore reliably predicted for its toxicity (72h-ErC50) to algae. 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): 0.18 – 1.0 mg/L
QSAR statistical parameters are given in the QMRF and the QPRF

Analysis of the Applicability Domain of the model

Descriptor domain

The Subcooled Liquid Water Solubility value (40.2 mg/L or -3.622 in log (mol/L)) given as the input to the Ecotox module of the iSafeRat® Holistic HA-QSAR falls within the descriptor domain of the model between a log water solubility (in log (mol/L)) of -5.15 to -0.82.

Structural fragment domain

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

Mechanistic domain

Currently, the ecotoxicity module of the iSafeRat® Holistic HA-QSAR 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.

See QMRF in "attached background material".

Validity criteria fulfilled:

yes

Conclusions:

The test item falls within the applicability domain of the model and was therefore reliably predicted for its toxicity (72h-ErC50) to algae. 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 0.43 mg/L.
95% confidence interval (α = 0.05): 0.18 – 1.0 mg/L

Executive summary:

A Quantitative Structure-Activity Relationship (QSAR) was used to calculate the inhibition of growth to algae of the test item. This QSAR model has been validated to be compliant with the OECD recommendations for QSAR modeling (OECD, 2004) 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. 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 criterion predicted was the ErC50 (Median Effective Concentration for specific growth rate), a statistically derived concentration which is expected to cause 50% inhibition of intrinsic rate of growth of the test system within a period of 72 hours.

The growth inhibition of algae was determined using validated QSAR model for the Mechanism of Action (MechoA) in question (MechoA 3.1, i.e. hard electrophiles as aldehydes) (Bauer et al., 2018). The QSAR model is based on validated data for a small but fully validated training set of chemicals derived from 72-hour ErC50 test on algae, for which the concentrations of the test item had been determined by chemical analyses over the test period. The correlation coefficients R2 and Root Mean Standard Errors (RMSE) values for 72h-ErC50 QSAR model were respectively 0.9747 and 0.2640.

The 72h-ErC50 of the test item to algae was predicted as 0.43 mg/L.

95% confidence interval (α = 0.05): 0.18 - 1.0 mg/L.

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:

September 4, 2010 to October 9, 2010

Reliability:

4 (not assignable)

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 assignable due to non sufficient information 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 for testing substances with a reasonable level of water solubility. Considering the acceptably high water solubility of the substance (40,2 mg/L) and the concentrations used in this study, this method could have been avoided. Furthermore, solvents are generally not appropriate for multiconstituent substances, like the test substance (which is a mixture of isomers), where the use of the solvent can preferentially dissolve one or more components and thereby affect the toxicity. Then, 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, the effects results were based on nominal concentrations instead of measured concentrations. Due to high instability of the test substance in water, it was not possible to maintain the test concentration within 80 -120% of the nominal values, even though the concentrations were adjusted twice per day. Analytical assessments showed that the test concentrations were decreased to less than 80% of the nominal values within 6 hours. Therefore, these results cannot be used and the study was disregarded.

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

March 2006

Deviations:

yes

Remarks:

Solvent was used ; effects results were based on nominal concentrations instead of measured ; test concentrations had decreased down less to 80% of the nominal values in every case

GLP compliance:

yes

Remarks:

Good Laboratory Practice statement signed on October 19, 2010.

Specific details on test material used for the study:

- Storage condition of test material: Stored at room temperature protected from direct sunlight

Analytical monitoring:

yes

Remarks:

Even though the treatment was renewed at each period of observation (new media), analytical checks showed that the test concentration was decreased to less than 50% at T0+24H, T0+30H, T0+48H, T0+54H and at the end of the test.

Details on sampling:

- Concentrations: 5 test item treatments : 0,8 ; 1,5 ; 2,8 ; 5,3 and 10 mg/L
- Sampling method: The test item was quantified at test initiation and at the end of test and at each adjustment of test item concentrations in the old and in the new media.
The algal biomass in each flask was determined daily obver 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 (Coulter counter ZM). The results were expressed as cells per liter of solution.

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The treatment solutions were prepared in acetone. The concentration of the treatment solutions were set in such a manner that the treatment concentrations were achieved when delivering 50 µL of the treatment solution per test vessel. Aliquots of 35, 100, 125 and 165 µL were added to the test vessels and the volumes adjusted with reconstituted water such to achieve treatment concentrations of 0,2 ; 0,6 ; 0,75 and 1,0 mg/L.
- 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

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Strain: Desmodesmus subspicatus
- Source (laboratory, culture collection): The strain was provided in December 2007 by the Museum National d'Histoire Naturelle (Paris, France) and regularly sub-cultured in the OECD medium at the Phytosafe site.
- Age of inoculum (at test initiation): The inoculum culture pepared 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.
- The surface of the cultures received continuous uniform fluorescent illumination of 4440 - 8880 lux, which is said to correspond approximately to the recommended light intensity 60-120 µE.m^-2.s^-1.

Test type:

semi-static

Water media type:

not specified

Limit test:

no

Total exposure duration:

72 h

Remarks on exposure duration:

No

Test temperature:

21-24 +/ 2°C

pH:

from 7.7 to 8.5

Nominal and measured concentrations:

The test item was highly unstable in water. Maintaining the test concentration within 80-120% of the nominal values was not feasible even though semi-static methodology was applied, with adjustment of the test concentration twice per day.
Analytical check 15 min after the initial treatment application gave approximately 80-120% recovery, as required but after 6 hours of testing, the test concentrations had decreased down to less than 80% of the nominal values in every case. The treatments were renewed and recovery exceeded 120 % in every case.
Time-course changes of the test concentration remained the same throughout the test period : analytical checks showed that the test concentration was decreased to less than 50% at T0+24h, To+30h, To+48h, To+54h and at the end of test (old media), even though the treatment was renewed at each period of observation (new media).

Details on test conditions:

TEST SYSTEM
- Test vessel: glass Erlenmeyer flasks
- Type (delete if not applicable): closed : the test vessels were capped with air-permeable stoppers.
- Material, size, headspace, fill volume: capacity of 250 mL, filled with 100 mL of culture
- Renewal rate of test solution (frequency/flow rate): adjustment of the test concentration twice per day
- Initial cells density: the initial biomass in the test cultures was the same in all test cultures and sufficiently low to allow
- No. of vessels per concentration (replicates): 3 replicates per concentration
- No. of vessels per control (replicates): 3 replicates per control
- No. of vessels per vehicle control (replicates): 3 replicates per solvent control

GROWTH MEDIUM
- Standard medium used: yes, OECD TG 201, according to ISO 8692

TEST CONCENTRATIONS
- Spacing factor for test concentrations:
- Justification for using less concentrations than requested by guideline:
- Range finding study: 0,01 - 0,1 - 1,0 - 10,0 and 98,7 mg/L
- Test concentrations: 0,8 -1,5 - 2,8 - 5,3 and 10,0 mg/L
- Results used to determine the conditions for the definitive study: Both growth rate and yield in biomass were considered as affected at both 10.0 and 98,7 mg/L test item treatments. The definitive test was thus performed for treatment concentrations between approximately 1 and 10 mg/L.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate was used as reference substance.

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: The test item was highly unstable in water. Maintaining the test concentration within 80-120% of the nominal values was not feasible even though semi-static methodology was applied, with adjustment of the test concentration twice per day.

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

2.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control (for algal test): yes

Results with reference substance (positive control):

The 72h-EC50 for Potassium dichromate was between 0,6 and 1,0 mg/L for the specific growth rate and between 0,2 and 0,75 mg/L for the yield. The results fulfilled the validity criteria based on Phytosafe historical data.

Definitive test : measured specific growth rates per day (section-by-section and total)

	0 to 24h	24 to 48h	48 to 72h	Total period
Control
Replicate 1	1,69	1,39	1,47	1,51
Replicate 2	1,71	1,41	1,4	1,51
Replicate 3	1,71	1,4	1,51	1,54
Mean +/- S.D.	1,70 +/- 0,01	1,40 +/- 0,01	1,46 +/- 0,06	1,52 +/- 0,02
Solvent
Replicate 1	1,73	1,43	1,35	1,5
Replicate 2	1,76	1,4	1,34	1,5
Replicate 3	1,68	1,39	1,44	1,5
Mean +/- S.D.	1,72 +/- 0,04	1,41 +/- 0,02	1,38 +/- 0,05	1,50 +/- 0,00
Noreenal 0,8 mg/L
Replicate 1	1,81	1,52	1,35	1,56
Replicate 2	1,78	1,46	1,33	1,52
Replicate 3	1,75	1,6	1,35	1,57
Mean +/- S.D.	1,78 +/- 0,03	1,53 +/- 0,07	1,34 +/- 0,01	1,55 +/- 0,02
Noreenal 1,5 mg/L
Replicate 1	1,83	1,58	1,26	1,56
Replicate 2	1,81	1,61	1,29	1,57
Replicate 3	1,82	1,69	1,32	1,61
Mean +/- S.D.	1,82 +/- 0,01	1,62 +/- 0,06	1,29 +/- 0,03	1,58 +/- 0,03
Noreenal 2,8 mg/L
Replicate 1	1,86	1,52	1,28	1,56
Replicate 2	1,85	1,51	1,39	1,58
Replicate 3	1,79	1,62	1,32	1,57
Mean +/- S.D.	1,83 +/- 0,04	1,55 +/- 0,06	1,33 +/- 0,06	1,57 +/- 0,01
Noreenal 5,3 mg/L
Replicate 1	1,93	1,35	1,1	1,46
Replicate 2	1,93	1,29	1,15	1,46
Replicate 3	1,85	1,46	1,16	1,49
Mean +/- S.D.	1,90 +/- 0,05	1,37 +/- 0,09	1,14 +/- 0,03	1,17 +/- 0,02
Noreenal 10,0 mg/L
Replicate 1	1,46	0,57	0,76	0,93
Replicate 2	1,51	0,61	0,7	0,94
Replicate 3	1,53	0,55	0,89	0,99
Mean +/- S.D.	1,50 +/- 0,04	0,58 +/- 0,03	0,79 +/- 0,10	0,96 +/- 0,03

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
Noreenal
	-4,50%	-9,20%	7,90%	-2,00%
1,5 mg/L	-7,10%	-16,00%	11,70%	-3,80%
2,8 mg/L	-7,80%	-10,60%	8,70%	-3,40%
5,3 mg/L	-11,90%	2,50%	22,10%	3,40%
10,0 mg/L	11,80%	58,60%	46,20%	37,10%

(1) Negative values indicate that the growth rate was increased as compared to the control

Definitive test: Analysis of the test solutions

	Nominal concentration (mg/L)	Old medium – Measured concentration (mg/L)	% recovery	New medium – Measured concentration (mg/L)	% recovery
T0	0.8			0.91	121.5
	1.5			1.45	99.9
	2.8			2.71	96.8
	5.3			5.16	97.3
	10.0			8.89	88.9
T0+6h	0.8	0.51	67.8	1.17	156.0
	1.5	0.85	58.4	1.96	135.0
	2.8	1.39	49.6	3.76	134.2
	5.3	2.33	44.0	7.48	141.2
	10.0	4.51	45.1	11.44	114.4
T0+24h	0.8	0.19	25.9	1.05	139.9
	1.5	0.46	31.7	2.01	138.3
	2.8	0.76	27.1	3.24	115.6
	5.3	1.26	23.7	6.57	123.9
	10.0	2.02	20.2	9.67	96.7
T0+30h	0.8	0.40	53.4	1.30	173.4
	1.5	0.83	57.5	2.17	149.8
	2.8	1.31	46.6	4.60	164.2
	5.3	2.64	49.8	8.40	158.6
	10.0	4.13	41.2	14.03	140.3
T0+48h	0.8	0.13	17.1	0.85	113.0
	1.5	0.33	22.8	1.71	117.6
	2.8	0.71	25.2	3.31	118.1
	5.3	1.48	27.9	7.16	135.1
	10.0	3.38	33.8	10.85	108.5
T0+54h	0.8	0.15	20.3	1.09	144.8
	1.5	0.48	33.1	2.19	151.3
	2.8	0.98	35.0	4.17	149.0
	5.3	2.52	47.6	8.08	152.5
	10.0	4.36	43.6	14.69	146.9
T0+72h	0.8	0.15	20.4
	1.5	0.21	14.4
	2.8	0.44	15.9
	5.3	1.08	20.4
	10.0	1.78	17.8

 

Validity criteria fulfilled:

yes

Conclusions:

The 72h-ErC50 and 72h-NOEC values for growth rate were determined at >10.0 and 2.8 mg/L, respectively, based on nominal concentrations.
This study is considered not assignable due to non sufficient information provided on the semi-static methodology used.

Executive summary:

The influence of the test substance on survival of Desmodesmus subspicatus was investigated according to OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test) (March 2006), with GLP compliance statement. Algae were exposed to the test item under semi-static conditions, for 72h.

Based on the results of a range-finding test, a definitive test was performed, exposing Desmodesmus subspicatus to 5 different nominal concentrations : 0.8 ; 1.5 ; 2.8 ; 5.3 and 10.0 mg/L.

The test item concentration and its stability in water throughout the test period were checked by appropriate analytical verification of the test solutions at both initiation and test completion, and after each adjustment, in the old and in the new medium. Due to high instability of the test item in water, it was not possible to maintain the test concentration within 80 -120% of the nominal values, even though the concentrations were adjusted twice per day. Analytical assessments showed that the test concentrations were decreased to less than 80% of the nominal values within 6 hours.

The 72h-ErC50 and 72h-NOEC values for growth rate were determined at >10.0 and 2.8 mg/L, respectively, based on nominal concentrations.

Even if all validity criteria were fulfilled, study is considered not assignable due to non sufficient information 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 for testing substances with a reasonable level of water solubility. Considering the acceptably high water solubility of the substance (40,2 mg/L) and the concentrations used in this study, this method could have been avoided. Furthermore, solvents are generally not appropriate for multiconstituent substances, like the test substance (which is a mixture of isomers), where the use of the solvent can preferentially dissolve one or more components and thereby affect the toxicity. Then, 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 higher than the suggested 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, the effects results were based on nominal concentrations instead of measured concentrations.

Description of key information

iSafeRat® High-Accuracy-Quantitative Structure-Activity Relationship, KREATIS, 2019 :

72h-ErC50 = 0.43 mg/L (95% confidence interval: 0.18 – 1.0 mg/L)

Key value for chemical safety assessment

EC50 for freshwater algae:

0.43 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, 2010) was considered as not assignable due to insufficient information 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 201. With this method, parent and degradation products are present simultaneously, so interactions can occur. 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 for testing substances with a reasonable level of water solubility. Considering the acceptably high water solubility of the substance (40.2 mg/L) and the concentrations used in this study, this method could have been avoided. Furthermore, solvents are generally not appropriate for multiconstituent substances, such as this test substance (which is a mixture of isomers), where the use of the solvent can preferentially dissolve one or more components and thereby affect the toxicity. Then, 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).

Under the test conditions, the 72h-ErC50 and NOEC values of the test substance to Desmodesmus subspicatus, based on growth rate, were determined at > 10.0 mg/L and 2.8 mg/L, respectively, based on nominal concentrations. Due to high instability of the test substance in water, it was not possible to maintain the test concentration within 80 -120% of the nominal values, even though the concentrations were adjusted twice per day. Analytical assessments showed that the test concentrations were decreased to less than 80% of the nominal values within 6 hours. Therefore, these results cannot be used and the study was disregarded.

The QSAR prediction (KREATiS, 2019) was considered as reliable and was used as key data. The QSAR model has been validated to be compliant with the OECD recommendations for QSAR modeling (OECD, 2004) and predicts the endpoint value which would be expected when testing the substance under experimental conditions in a laboratory following the OECD Guideline 201. The growth inhibition of algae was determined using validated QSAR model for the Mechanism of Action (MechoA) in question (MechoA 3.1, i.e. hard electrophiles as aldehydes) (Bauer et al., 2018). The QSAR model is based on validated data for a small but fully validated training set of chemicals derived from 72-hour ErC50 test on algae, for which the concentrations of the test item had been determined by chemical analyses over the test period. The correlation coefficients R2 and Root Mean Standard Errors (RMSE) values for 72h-ErC50 QSAR model were respectively 0.9747 and 0.2640.

The result below is the toxicity values anticipated during a 72-hour study on algae based on measured concentrations. 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 0.43 mg/L (95% CI: 0.18 – 1.0 mg/L)