[No public or meaningful name is available]

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

effects on growth of green algae

Type of information:

mixture rules calculation

Adequacy of study:

key study

Study period:

08 December 2021 to 03 January 2022

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

yes

Remarks:

(tested according to the Water Accommodated Fraction (WAF) approach, i.e. OECD technical guideline 23)

Principles of method if other than guideline:

The TOXICITY TO ALGAE (72-HOUR ErL50 and NOELr) was determined using iSafeRat® calculation method adapted for a mixture of compounds with the Mechanism of Action (MechoA) in question (MechoA 1.1, i.e. non-polar narcosis) (Bauer et al., 2018). This method has previously been validated in an internal publication for acute exposure of non-polar narcosis compounds (Bicherel and Thomas, 2014). The algorithm is based on two QSAR models which have been validated to be compliant with the OECD recommandations for QSAR modeling (OECD, 2004, 2007). The QSAR models are based on validated data from a training set of 40 chemicals (for 72-hour ErC50) and 31 chemicals (for NOECr) derived from 72-hour test on algae, for which the concentrations of the test item had been determined by chemical analyses over the test period. Further to this the effective loading rate of the WAF is determined by using a series of calculation steps using phase equilibrium thermodynamics and excluding the non-bioavailable fraction.

GLP compliance:

no

Remarks:

(calculation method)

Specific details on test material used for the study:

not applicable

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: calculation method based on QSAR model predictions

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 the models.

Post exposure observation period:

None

Hardness:

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

Salinity:

Not applicable

Conductivity:

Not applicable

Nominal and measured concentrations:

Studies were used for QSAR model development 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):

not required

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

5 mg/L

Nominal / measured:

nominal

Conc. based on:

other: loading rate of Water Accomodated Fraction (WAF)

Basis for effect:

growth rate

Remarks on result:

not determinable

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

2.1 mg/L

Nominal / measured:

nominal

Conc. based on:

other: loading rate of Water Accomodated Fraction (WAF)

Basis for effect:

growth rate

Remarks on result:

not determinable

Results with reference substance (positive control):

not applicable

Prior Analysis of the MechoA constituents of the test item.

The calculation method used in this study is based on toxic additivity principle. That means the toxic parts of each constituent are added up. Therefore the constituents considered within the mixture should act with a similar MechoA. The MechoA of the consituents are determined using the methodology described by Bauer et al. (2018) and reported in the Table below.

 

constituents	MechoA	Description
const1	1.1	non-polar narcotic
const2	1.1	non-polar narcotic
const3	1.1	non-polar narcotic
const4	1.1	non-polar narcotic
const5	3.2	soft electrophile reactivity
const6	1.1	non-polar narcotic
const7	1.1	non-polar narcotic
const8	1.1	non-polar narcotic
const9	1.1	non-polar narcotic
const10	3.1	hard electrophile reactivity
const11	3.2	soft electrophile reactivity
const12	1.1	non-polar narcotic
const13	3.1	hard electrophile reactivity
const14	3.1	hard electrophile reactivity
const15	1.1	non-polar narcotic
const16	1.1	non-polar narcotic
const17	1.1	non-polar narcotic
const18	1.1	non-polar narcotic
const19	1.1	non-polar narcotic

Not all the constituents share the same MechoA (i.e. MechoA 1.1). Some constituents are classified for having another MechoA than MechoA 1.1. However the toxicity of the test item is used in a calculation method based on additivity approach. To apply the calculation method to the test item, all the constituents were considered as following a mechanism of toxic action of non-polar narcosis (i.e. MechoA 1.1) prior to predict their individual aquatic toxicity. Therefore, the global result is considered as reliable with restrictions (mechanism domain).

 

Posterior Analysis of the WAF composition at the toxicity value (ErL₅₀/NOELr) for the typical composition.

The Pareto chart within the study report hightlights the importance of each constituent in order to explain the global toxicity of the WAF of the mixture for the toxic loading rate (E/LL₅₀). They indicate limonene explains ca. 70% of the test item toxicity.

Validity criteria fulfilled:

yes

Conclusions:

The TOXICITY TO ALGAE (72-HOUR ErL50 and NOELr) of the test item has been determined using the iSafeRat® calculation method for mixtures tested according to the Water Accomodated Fraction (WAF) approach. Each constituent of the test item does not completely fall within the applicability domain of the model used to determine their individual TOXICITY TO ALGAE (72-HOUR ErC50 and NOECr). Therefore, the final result for the test item is considered as an extrapolation (reliable with restrictions). The result remains valid for use in risk assessment and classification and labelling.
The TOXICITY TO ALGAE (72-HOUR ErC50 and NOECr) of the test item tested according to the WAF method was predicted as a loading rate of 5.0 mg/L for the 72-HOUR ErL50 and 2.1 mg/L for the NOELr based on the typical composition

Executive summary:

A calculation method was used to assess the TOXICITY TO ALGAE (72-HOUR ErL50 and NOELr) of the test item, a Natural Complex Substance, tested according to the Water Accommodated Fraction (WAF) approach. This calculation method 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) adapted for testing of a mixture using the WAF method. The criterions predicted were the Median Effective Loading rate (ErL₅₀), 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 Loading rate (NOELr), a tested loading rate 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 ErL50 and NOELr) was determined using iSafeRat® calculation method adapted for a mixture of compounds with the Mechanism of Action (MechoA) in question (MechoA 1.1, i.e. non-polar narcosis) (Bauer et al., 2018). This method has previously been validated in an internal publication for acute exposure of non-polar narcosis compounds (Bicherel and Thomas, 2014). The algorithm is based on two QSAR models which have been validated to be compliant with the OECD recommandations for QSAR modeling (OECD, 2004, 2007). The QSAR models are based on validated data from a training set of 40 chemicals (for 72-hour ErC50) and 31 chemicals (for NOECr) derived from 72-hour test on algae, for which the concentrations of the test item had been determined by chemical analyses over the test period. Further to this the effective loading rate of the WAF is determined by using a series of calculation steps using phase equilibrium thermodynamics and excluding the non-bioavailable fraction.

 

Each constituent of the test item does not completely fall within the applicability domain of the model used to determine their individual TOXICITY TO ALGAE (72-HOUR ErC50 and NOECr). Therefore, the final result for the test item is considered as an extrapolation (reliable with restrictions). The result remains valid for use in risk assessment and classification and labelling.

 

Based on the composition provided by the sponsor, the TOXICITY TO ALGAE of the test item tested according to the WAF method was predicted as a loading rate of 5.0 mg/L for the 72-HOUR ErL50 and 2.1 mg/L for the NOECr.

 

95% confidence interval (α = 0.05): not determined

Description of key information

calculation method , KREATIS, 2022 :

72h-ErL50 = 5 mg/L (95% confidence interval: not determined)

72h-NOELr = 2.1 mg/L (95% confidence interval: not determined)

Key value for chemical safety assessment

EC50 for freshwater algae:

5 mg/L

EC10 or NOEC for freshwater algae:

2.1 mg/L

Additional information

To assess the toxicity of the registered substance to aquatic algae one QSAR prediction (KREATIS, 2022) is available. 

A calculation method was used to assess the TOXICITY TO ALGAE (72-HOUR ErL50 and NOELr) of the test item, a Natural Complex Substance, tested according to the Water Accommodated Fraction (WAF) approach. This calculation method 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) adapted for testing of a mixture using the WAF method. The criterions predicted were the Median Effective Loading rate (ErL₅₀), 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 Loading rate (NOELr), a tested loading rate 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 ErL50 and NOELr) was determined using iSafeRat® calculation method adapted for a mixture of compounds with the Mechanism of Action (MechoA) in question (MechoA 1.1, i.e. non-polar narcosis) (Bauer et al., 2018). This method has previously been validated in an internal publication for acute exposure of non-polar narcosis compounds (Bicherel and Thomas, 2014). The algorithm is based on two QSAR models which have been validated to be compliant with the OECD recommandations for QSAR modeling (OECD, 2004, 2007). The QSAR models are based on validated data from a training set of 40 chemicals (for 72-hour ErC50) and 31 chemicals (for NOECr) derived from 72-hour test on algae, for which the concentrations of the test item had been determined by chemical analyses over the test period. Further to this the effective loading rate of the WAF is determined by using a series of calculation steps using phase equilibrium thermodynamics and excluding the non-bioavailable fraction.

 

Each constituents of the test item which have been considered fall within the applicability domain of the model used to determine their individual TOXICITY TO ALGAE (72-HOUR ErL50 and NOELr). Not all the constituents were identified with the same MechoA (i.e. MechoA 1.1: non-polar narcosis). However the toxicity of the test item is determined by using a calculation method based on additivity approach for MechoA 1.1. To apply the calculation method to the test item, all the constituents were considered as non-polar narcotic prior to predict their individual aquatic toxicity. Therefore, the global result is considered as reliable with restrictions (mechanism domain).

 

Based on the composition provided by the sponsor, the TOXICITY TO ALGAE of the test item tested according to the WAF method was predicted as a loading rate of 5.0 mg/L for the 72-HOUR ErL50 and 2.1 mg/L for the NOECr.

 

95% confidence interval (α = 0.05): not determined