(2-methyl-5-propan-2-ylcyclopentyl) propanoate

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 September 13, 2010 to September 24, 2010

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 for the following reasons: - 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. - 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). - Loss of substance were observed during the test but the results were based on nominal concentrations instead of measured concentrations. - Finally, the initial measured tested concentrations at each renewal period were above the real water solubility value, so the experimental results cannot be used.

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; 3 replicates in control instead of 6; results based on nominal instead of measured values; concentrations > water solubility.

GLP compliance:

yes (incl. QA statement)

Remarks:

Date of inspection 23-24 July 2009 / GLP certificate signed on 01 June 2010

Specific details on test material used for the study:

- Appearance: Colourless translucent liquid
- Storage condition of test material: Room temperature protected from direct sun light

Analytical monitoring:

yes

Details on sampling:

The test item concentrations were measured at test initiation and at the end of test, and at each adjustment of the test item concentration, in the old and in the new medium.

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
- 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 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 7.6 to 8.8
The deviation throughout the test period in the control group remained lower than 1.5 units.

Salinity:

Not applicable

Nominal and measured concentrations:

- Nominal treatment concentrations: 9.9, 15.9, 25.4, 40.6 and 65.0 mg/L.
- Measured concentrations: See table 6.1.1/2 in "Any other information on results incl. tables".
The results showed that the test substance was highly instable in water. Maintaining the test concentration, within 80-120% the nominal value 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 45-70% recovery only. After 6 hours of testing, the test concentration had decreased down to less than 10% of the nominal values in every case. The treatment was renewed, and check within 15 min. gave 68-85% recovery of the nominal concentrations. Time-course changes of the test concentration remained the same throughout the test period: analytical checks showed that the test concentration was decreased to almost zero at T0+24h, T0+32h, T0+48h, T0+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 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): The test concentration was adjusted twice per day, after 6, 24, 32, 48 and 56 hours of testing by adding new 50 µL of treatment solution per vessel (semi-static methodology)
- 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
The test vessels were continuously shaken in a culture apparatus (Innova Shaker 44R) so as to keep the algae in suspension and facilitate the transfer of CO2.
- Photoperiod: continuous uniform fluorescent illumination of 4440 - 8880 lux
- 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.

TEST CONCENTRATIONS
- Range finding study : yes
- Test concentrations: 0.01, 0.10, 1.0, 10.0 and 100.0 mg/L
- Results used to determine the conditions for the definitive study: The control cultures exhibited an exponential growth throughout the test period. The multiplication rate was 80 for the water control and 75 for the solvent control. That was also the case for the test item treatments up to and including 10.0 mg/L. The growth was almost totally inhibited at 100.0 mg/L. The definitive test was thus performed for treatment concentrations between approximately 10 and 100 mg/L.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

56.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CI = 30.5 - 104.6 mg/L

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

9.9 mg/L

Nominal / measured:

nominal

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 control cultures showed exponential growth throughout the test period. The multiplication rate was approximately 250 for both the water control and the solvent control (mean value). The multiplication rate was decreased for the test item treatments in every case except 9.9 mg/L.
The specific growth rate was regular in the control group throughout the test period, and the standard deviation between the 3 replicate units corresponded to less than 35% of the mean value at each sampling time. The standard deviation for the average specific growth rates throughout the entire test period in the replicate control cultures did not exceed 7% as required.
For the first day of testing, the specific growth rate was significantly reduced at both 40.6 and 65.0 mg/L test item treatments. For the second day and the third day of testing, the specific growth rate was significantly reduced at 25.4 mg/L also. Over all examination for the entire test period showed that the specific growth rate was significantly reduced in every case except 9.9 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 0.79 mg/L as the measured value.

Reported statistics and error estimates:

F-variance analysis at a 5% confidence level served to judge upon the difference in mean specific growth rates (section-by-section and total values) within each test item treated groups as compared to the control ones. The threshold value for F at the 5% confidence level was calculated to be 7.71.

Table 6.1.5/2: Analysis of the test solutions

	Nominal concentration	Old medium		New medium
		Measured (mg/L)	% recovery	Measured (mg/L)	% recovery
T0	9.9 mg/L 15.9 mg/L 25.4 mg/L 40.6 mg/L 65.0 mg/L			5.07 7.09 14.81 23.80 45.18	51.2 44.7 58.4 58.6 69.5
T0+6h	9.9 mg/L 15.9 mg/L 25.4 mg/L 40.6 mg/L 65.0 mg/L	0.93 1.31 2.06 3.37 5.55	9.4 8.2 8.1 8.3 8.6	6.70 11.41 20.64 29.50 55.39	67.6 71.9 81.3 72.7 85.3
T0+24h	9.9 mg/L 15.9 mg/L 25.4 mg/L 40.6 mg/L 65.0 mg/L	0.23 1.12 0.54 0.77 1.40	2.3 7.0 2.1 1.9 2.2	6.32 10.97 20.65 31.32 45.67	63.7 69.2 81.4 77.1 70.3
T0+30h	9.9 mg/L 15.9 mg/L 25.4 mg/L 40.6 mg/L 65.0 mg/L	1.61 0.71 1.27 2.13 3.54	16.2 4.5 5.0 5.3 5.4	7.47 12.29 19.90 36.00 49.13	75.4 77.5 78.4 88.7 75.6
T0+48h	9.9 mg/L 15.9 mg/L 25.4 mg/L 40.6 mg/L 65.0 mg/L	0.30 0.62 0.66 0.98 1.66	3.0 3.9 2.6 2.4 2.6	6.57 9.76 15.07 25.56 52.84	66.3 61.5 59.4 62.9 81.3
T0+54h	9.9 mg/L 15.9 mg/L 25.4 mg/L 40.6 mg/L 65.0 mg/L	0.49 2.10 1.05 1.79 2.78	4.9 13.3 4.2 4.4 4.3	6.93 11.06 15.88 32.28 54.15	69.9 69.8 62.6 79.5 83.3
T0+72h	9.9 mg/L 15.9 mg/L 25.4 mg/L 40.6 mg/L 65.0 mg/L	1.30 0.37 0.44 0.73 1.30	13.1 2.3 1.7 1.8 2.0

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	1.88 1.86 1.89 1.88±0.02	1.90 1.96 1.91 1.93±0.03	1.71 1.77 1.75 1.75±0.03	1.83 1.87 1.85 1.85±0.02
Solvent control
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.92 1.86 1.92 1.90±0.03	1.87 1.92 1.80 1.86±0.06	1.76 1.73 1.86 1.79±0.07	1.85 1.84 1.86 1.85±0.01
Test substance, 9.9 mg/L
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.98 1.99 1.90 1.96±0.05	1.92 1.88 1.97 1.93±0.05	1.73 1.77 1.73 1.74±0.02	1.88 1.88 1.87 1.88±0.01
Test substance, 15.9 mg/L
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.96 1.95 1.96 1.96±0.01	1.77 1.76 1.79 1.77±0.02	1.69 1.68 1.65 1.67±0.02	1.81 1.79 1.80 1.80±0.01
Test substance, 25.4 mg/L
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.87 1.93 1.90 1.90±0.03	1.54 1.64 1.66 1.61±0.07	1.39 1.31 1.37 1.36±0.04	1.60 1.63 1.64 1.62±0.02
Test substance, 40.6 mg/L
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.76 1.67 1.68 1.70±0.05	1.21 1.29 1.29 1.26±0.04	0.85 0.75 0.73 0.78±0.07	1.28 1.24 1.23 1.25±0.02
Test substance, 65.0 mg/L
Replicate 1 Replicate 2 Replicate 3 Mean±SD	1.38 1.34 1.30 1.34±0.04	0.66 0.82 0.67 0.70±0.10	0.34 0.29 0.34 0.32±0.03	0.78 0.82 0.77 0.79±0.03

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

Test substance	0 to 24h	24 to 48h	48 to 72h	Total period
9.9 mg/L	-4.0%	0.0%	0.1%	-1.3%
15.9 mg/L	-4.0%	7.9%	4.2%	2.7%
25.4 mg/L	-1.1%	16.3%	22.2%	12.2%
40.6 mg/L	9.5%	34.3%	55.4%	32.6%
65.0 mg/L	28.8%	63.5%	81.6%	57.4%

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 9.9 and 56.6 mg/L (95% CI: 30.5 - 104.6 mg/L), respectively, based on nominal concentrations.
This study is considered not reliable due to the choice of tested concentrations greater than the real water solubility value, the high concentration of solvent used 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 9.9, 15.9, 25.4, 40.6 and 65.0 mg/L for 72 hours, under continuous uniform fluorescent illumination at a temperature of 21 -24 +/- 2°C and semi-static methodology.

Due to high instability of the test item in water, it was not possible to maintain the test concentrations at 80 -120% of the nominal values even though the test item treatments were renewed twice per day. Analytical assessments showed that the test concentrations were decreased to less than 10% of the nominal values within 6 hours.

Exposure of Desmodesmus subspicatus to the test material gave 72h-ErC50 value of 56.5 mg/L [95% CI = 30.5 - 104.6 mg/L] and 72h-NOEC of 9.9 mg/L, based on specific growth rate and nominal concentrations.

All validity criteria were fulfilled. However, this study is considered not reliable for the following reasons:

- 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.

- 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).

- Loss of substance were observed during the test but the results were based on nominal concentrations instead of measured concentrations.

- Finally, the initial measured tested concentrations at each renewal period were above the real water solubility value, so the experimental results cannot be used.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

29 July 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® – in Silico Algorithms For Environmental Risk And Toxicity

2. MODEL (incl. version number)
iSafeRat® algErC50 v1.9

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
SMILES: CCC(=O)OC1C(CCC1C(C)C)C
Water solubility: 15.4 mg/L (KREATiS, 2020)

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

Reason / purpose for cross-reference:

reference to other study

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 and iSafeRat® algNOEC, two validated QSAR models for the Mechanism of Action (MechoA) in question (MechoA 2.1, i.e. mono-/poly-esters whose hydrolysis products are narcotics) (Bauer et al., 2018). The purpose of this study 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 QSAR models are based on validated data for a training set of 44 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: 4.3 (Phytosafe, 2011)
- Water Solubility: 15.4 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.:

2.9 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: 2.4 – 3.5 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). 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: 2.4 – 3.5 mg/L

Applicability Domain

Descriptor domain

The Subcooled Liquid Water Solubility value (15.4 mg/L or -4.111 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 -5.57 to 0.93 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 ester is expected to exert a MechoA 2.1 (Bauer et al., 2018) and can be taken into account by the model iSafeRat® algErC50 but not by the model iSafeRat® algNOECr.

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

The TOXICITY TO ALGAE (72-HOUR ErC50) of the test item was predicted as 2.9 mg/L.
The TOXICITY TO ALGAE (72-HOUR NOECr) of the test item was not predicted.
95% confidence interval (α = 0.05) for 72h-ErC50: 2.4 – 3.5 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 and iSafeRat® algNOEC, two validated QSAR models for the Mechanism of Action (MechoA) in question (MechoA 2.1, i.e. mono-/poly-esters whose hydrolysis products are narcotics) (Bauer et al., 2018). The QSAR models are based on validated data for a training set of 44 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 within the applicability domain of the model for 72-HOUR ErC50 and was therefore reliably predicted for its TOXICITY TO ALGAE (72-HOUR ErC50). Therefore, this endpoint value can be considered valid for use in risk assessment and classification and labelling. The test item falls out of the mechanistic domain of the model for TOXICITY TO ALGAE (72-HOUR NOECr).

The TOXICITY TO ALGAE (72-HOUR ErC50) of the test item was predicted as 2.9 mg/L.

The TOXICITY TO ALGAE (72-HOUR NOECr) of the test item was not predicted.

95% confidence interval (α = 0.05) for 72h-ErC50: 2.4 – 3.5 mg/L.

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

Description of key information

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

72h-ErC50 = 2.9 mg/L (95% confidence interval: 2.4 - 3.5 mg/L)

Key value for chemical safety assessment

EC50 for freshwater algae:

2.9 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 reliable mainly due to the choice of tested concentration greater than the real water solubility value 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. Then, 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. 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, loss of substance were observed during the test but the results were based on nominal concentrations instead of measured concentrations, and the initial measured tested concentrations at each renewal period were above the real water solubility value, so this experimental result cannot be used.

 

The QSAR prediction (KREATiS, 2020) was considered as reliable and was used as key data. Two QSAR models were used to calculate the toxicity to algae (72h-ErC50 and 72h-NOECr) of the registered substance. 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 OECD Guideline 201. The toxicity to algae (72h-ErC50 and 72h-NOECr) was determined using iSafeRat® algEC50 and iSafeRat® algNOEC, two validated QSAR models for the Mechanism of Action (MechoA) in question (MechoA 2.1, i.e. mono-/poly-esters whose hydrolysis products are narcotics) (Bauer et al., 2018). The QSAR models are based on validated data for a training set of 44 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 QSAR model for 72h-NOECr was not applicable for the test substance due to the limitation of the mechanistic domain. 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 2.9 mg/L (95% CI: 2.4 – 3.5 mg/L)