2-(3,3-dimethylcyclohex-1-enyl)-2,5,5-trimethyl-1,3-dioxane

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:

experimental study

Adequacy of study:

disregarded due to major methodological deficiencies

Study period:

From August 7, 2015 to November 27, 2015

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

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 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. 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 test solutions were prepared with a solvent (acetone), which is not an appropriate method to conduct toxicity tests for substances with a solubility at the level of this substance (15.4 mg/L). In addition, the concentration/quantity of solvent used in the treatment solutions was 0.5 mL/L, corresponding to 395 mg/L (acetone has 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).

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.

GLP compliance:

yes (incl. QA statement)

Remarks:

Inspection dates: 12 and 13 June 2014 / Certificate signed on 5 March 2015

Specific details on test material used for the study:

- Physical state: Colourless translucent liquid
- Storage condition: Room temperature protected from direct sun light

Analytical monitoring:

yes

Details on sampling:

One additionall set of vessels were prepared without algae for each test item treatment used for the definitive test. They were maintained under the same environmental conditions as the test system, and were used for analytical check of the test item concentrations throughout the test period.

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. The different treatment solutions are shown in Table 6.1.5/1 in "Any other information on materials and methods including tables".
- 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. see Table 6.1.5/1

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 such to adapt the test alge to test conditions and ensure that the algae were in the exponential growth phase when used to inoculate the test solutions.

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

Limit test:

no

Total exposure duration:

72 h

Hardness:

No data

Test temperature:

21 - 24°C +/- 2 °C

pH:

from 8.1 to 9.3
The initial pH value was within the range 8.1-8.2 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 water controls for the solvent control and the test treatments.

Dissolved oxygen:

No data

Salinity:

Not applicable

Conductivity:

No data

Nominal and measured concentrations:

Nominal test concentrations : 2.0 - 3.0 - 4.4 - 6.7 and 10.0 mg/L
Geometric mean measured concentrations: 0.6 - 1.0 - 1.5 - 2.0 and 3.5 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 would not remain within 80-120 % of the nominal values. As a consequence, the test item 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 ultures 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 test vessels were kept under orbital shaking so as to keep the algae in suspension and to facilitate the transfer of CO2.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : The cell density was counted at test initiation and then after 24h, 48h and 72h of culture; growth rate and yield were evaluated.
- Determination of cell concentrations: electronic cell counter (cells/L 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: 0.004, 0.02, 0.1, 0.5 and 2.5 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 2.5 mg/L. Because the limit of solubility for the test substance was determined appoximately 7 mg/L, the definitive test was focused on higher concentration rates.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 3.5 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Remarks:

the highest tested concentration

Basis for effect:

growth rate

Remarks on result:

not determinable

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

3.5 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Remarks:

the highest tested concentration

Basis for effect:

growth rate

Remarks on result:

not determinable

Details on results:

The cells appeared healthy in the controls and the test item treatments.

Analytical verification of the test item treatments: 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 60% over a 9h-period, and was almost total 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 0.6, 1.0, 1.5, 2.0 and 3.5 mg/L instead of 2.0, 3.0, 4.4, 6.7 and 10.0 mg/L.

No regression curve was calculated because there was no significant effect over the test range, and the 72h-ErC50 was reported as > 3.5 mg/L which was the highest test substance concentration in the present study (geometric mean of the measured concentrations)

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
- Other: EC50 for yield between 0.2 and 0.75 mg/L

Reported statistics and error estimates:

F-variance analysis at a 5% confidence level was used to judge upon the difference for mean specific growth rate (section-by-section and total values) foe each test item treatment compared to the water controls.
No significant difference was observed for the solvent control and the test item treatments up to and including 3.5 mg/L as referred to section-by-section or overall specific growth rate per day.

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

	Nominal concentrations, mg a.i./L
	2.0	3.0	4.4	6.7	10.0
T0	1.45 mg/L 72.0%	2.47 mg/L 81.8%	3.27 mg/L 74.0%	4.86 mg/L 72.2%	8.67 mg/L 86.3%
T0+6h – Old medium	0.90 mg/L 44.9%	1.25 mg/L 41.6%	1.81 mg/L 41.0%	2.65 mg/L 39.3%	3.78 mg/L 37.6%
T0+6h – New medium	1.60 mg/L 79.6%	2.79 mg/L 92.6%	3.41 mg/L 77.1%	5.34 mg/L 79.3%	6.09 mg/L 60.6%
T0+21h – Old medium	0.05 mg/L 2.7%	0.28 mg/L 9.2%	0.25 mg/L 5.6%	0.64 mg/L 9.5%	1.24 mg/L 12.4%
T0+21h – New medium	2.17 mg/L 107.9%	3.61 mg/L 119.8%	5.25 mg/L 118.8%	6.52 mg/L 96.9%	9.28 mg/L 92.4%
T0+30h – Old medium	0.74 mg/L 36.7%	1.04 mg/L 34.6%	1.74 mg/L 39.3%	2.00 mg/L 29.7%	3.81 mg/L 37.9%
T0+30h – New medium	1.99 mg/L 99.2%	3.05 mg/L 101.0%	4.50 mg/L 101.7%	5.10 mg/L 75.7%	10.06 mg/L 100.1%
T0+45h – Old medium	0.12 mg/L 5.8%	0.22 mg/L 7.4%	0.94 mg/L 21.3%	0.32 mg/L 4.8%	0.92 mg/L 9.1%
T0+45h – New medium	2.34 mg/L 116.3%	3.56 mg/L 118.1%	5.29 mg/L 119.6%	7.13 mg/L 105.9%	10.67 mg/L 106.2%
T0+54h – Old medium	0.54 mg/L 26.7%	1.06 mg/L 35.2%	1.54 mg/L 34.9%	1.99 mg/L 29.5%	4.03 mg/L 40.1%
T0+54h – New medium	2.14 mg/L 106.5%	3.07 mg/L 101.7%	4.25 mg/L 96.2%	6.56 mg/L 97.5%	8.51 mg/L 84.7%
T0+72h	0.18 mg/L 8.9%	0.13 mg/L 4.4%	0.14 mg/L 3.3%	0.30 mg/L 4.4%	0.57 mg/L 5.7%
Geometric mean	0.6 mg/L	1.0 mg/L	1.5 mg/L	2.0 mg/L	3.5 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	1.21 1.32 1.15 1.22±0.09	1.76 1.63 1.75 1.71±0.08	1.90 1.98 2.00 1.96±0.06	1.62 1.64 1.63 1.63±0.01
Solvent control
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.09 1.26 1.12 1.16±0.09	1.77 1.75 1.81 1.78±0.03	2.00 1.90 1.92 1.94±0.05	1.62 1.64 1.62 1.63±0.01
Test substance, 0.6 mg/L
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.18 1.27 1.19 1.22±0.05	1.70 1.58 1.74 1.67±0.08	1.86 2.02 1.89 1.92±0.08	1.58 1.62 1.61 1.60±0.02
Test substance, 1.0 mg/L
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.03 1.37 1.10 1.17±0.18	1.86 1.51 1.91 1.76±0.22	1.86 1.93 1.89 1.89±0.03	1.59 1.60 1.63 1.61±0.02
Test substance, 1.5 mg/L
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.01 1.27 1.23 1.17±0.14	1.77 1.45 1.75 1.66±0.18	1.86 2.14 1.95 1.98±0.14	1.55 1.62 1.65 1.60±0.05
Test substance, 2.0 mg/L
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.29 1.07 1.25 1.21±0.12	1.67 1.85 1.58 1.70±0.14	1.99 1.88 1.90 1.92±0.06	1.65 1.60 1.58 1.61±0.04
Test substance, 3.5 mg/L
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.32 1.19 1.29 1.27±0.07	1.50 1.66 1.77 1.64±0.14	1.90 1.95 1.84 1.90±0.06	1.57 1.60 1.63 1.60±0.03

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	5.4%	-3.7%	1.0%	0.4%
0.6 mg/L	0.7%	2.2%	2.0%	1.8%
1.0 mg/L	4.6%	-2.8%	3.4%	1.5%
1.5 mg/L	4.4%	3.2%	-1.2%	1.7%
2.0 mg/L	1.6%	0.9%	1.8%	1.4%
3.5 mg/L	-3.3%	4.0%	3.3%	1.9%

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

Validity criteria fulfilled:

yes

Conclusions:

No regression curve was calculated because there was no significant effect over the test range. The 72h-NOEC and 72h-ErC50 values based on growth rate were reported at 3.5 and >3.5 mg/L, respectively, which was the highest test substance concentration in the present study (geometric mean of the measured concentrations)
This study is considered not assignable due to insufficient information provided on the semi-static methodology used.

Executive summary:

This study was performed to assess the effect of the tested item on the growth of Desmodesmus subspicatus. The method followed that described in the OECD Guideline No. 201.

Following a preliminary range-finding study, Desmodesmus subspicatus was exposed to the test material (prepared with acetone as solvent) at concentrations of 2.0 - 3.0 - 4.4 - 6.7 and 10.0 mg/L (nominal) for 72 hours, under continuous uniform fluorescent illumination at a temperature of 21-24 +/- 2°C.

Due to high volatility of the test item, the test solutions were adjusted twice per day. Despite this, the test concentrations were not maintained within 80 -120% of the nominal values and resulted in 0.6 - 1.0 - 1.5 - 2.0 and 3.5 mg/L, respectivey, as the geometric means of the measured concentrations in the old and the new media.

The cells appeared healthy in the controls and the test item treatments. In addition, no regression curve was calculated because there was no significant effect over the test range. The 72h-NOEC and 72h-ErC50 values based on growth rate were reported at 3.5 and >3.5 mg/L, respectively, which was the highest test substance concentration in the present study (geometric mean of the measured concentrations)

All validity criteria were fulfilled. However, this study is considered 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. 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 test solutions were prepared with a solvent (acetone), which is not an appropriate method to conduct toxicity tests for substances with a solubility at the level of this substance (15.4 mg/L).

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).

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

October 16th, 2019 to 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
CC1(C)C=C(C2(OCC(C)(C)CO2)C)CCC1
The toxicity of the test item was predicted using the iSafeRat® Ecotox module providing the Subcooled Liquid Water Solubility (SLWS) as the input. TThe 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 = 15.4 mg/L (or -4.190 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:

no

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 (OECD, 2006) and EC method C.3 (European Commission, 2008) 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 recommendations (OECD, 2004).

GLP compliance:

no

Remarks:

QSAR model

Specific details on test material used for the study:

- Mechanism of action : MechoA 1.1: non-polar narcosis (Bauer et al., 2018)
- Log Kow: 4.37 at 20°C and pH 7.1 (Phytosafe, 2015; EEC A.8; Shake-Flask method)
- Water solubility : 15.4 mg/L (KREATiS, 2019)

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 QSAR is based on data from reliable studies performed at acceptable oxygen concentrations.

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.:

1.2 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95%CL: 1.0 - 1.6 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.

Results with reference substance (positive control):

Not applicable

Reported statistics and error estimates:

95% confidence interval (α = 0.05): 1.0 – 1.6 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 (15.4 mg/L or -4.190 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 -4.38 to 0.49.

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 a cetal (i.e. diether) is expected to exert a MechoA 1.1 and can be taken into account by the model.

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 1.2 mg/L.
95% confidence interval (α = 0.05): 1.0 – 1.6 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 1.1,i.e. non-polar narcosis) (Bauer et al., 2018). The QSAR model is based on validated data for a training set of 40 chemicals derived from 72-hour ErC₅₀test on algae, 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 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 1.2 mg/L.

95% confidence interval (α = 0.05): 1.0 – 1.6 mg/L

Description of key information

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

72h-ErC50 = 1.2 mg/L (95% confidence interval: 1.0 – 1.6 mg/L)

Key value for chemical safety assessment

EC50 for freshwater algae:

1.2 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, 2016) 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 test solutions were prepared with a solvent (acetone), which is not an appropriate method to conduct toxicity tests for substances with a solubility at the level of this substance (15.4 mg/L).

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).

Under the test conditions, no significant effect over the test range was observed. The 72h-ErC50 and NOEC values of the test substance to Desmodesmus subspicatus, based on growth rate, were reported as greater than 3.5 mg/L, the highest test substance concentration the present study (geometric mean of the 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 test concentrations were adjusted twice per day. Based on all these deviations, 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 1.1, i.e. non-polar narcosis) (Bauer et al., 2018). The QSAR model is based on validated data for a training set of 40 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 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 registered substance to algae was predicted at 1.2 mg/L (95% CI: 1.0 – 1.6 mg/L)