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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
November 30th 2017
Reliability:
2 (reliable with restrictions)
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:
Cedarwood texas oil (cedrene) is an UVCB substance. Regarding the different solubility of its constituents that make the testing difficult and a known fraction 90.47%, calculation from the ecotoxicity of the known constituent appears as an acceptable approach.
Principles of method if other than guideline:
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", (1) referenced as Method C.3 of Commission Regulation No. 440/2008 (2) adapted for testing of a mixture using the WAF method. The criterion measured was the median effective loading rate of the mixture ErL50 (Median Effective Loading for specific growth rate), a statistically derived loading rate 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 a validated calculation method for the Mode of Action (MOA) in question (non-polar narcosis). It has been validated in an internal publication for MOA 1 (non-polar narcosis) and acute exposure (Bicherel and Thomas, 2014) (3). The algorithm is based on a QSAR model which has been validated to be compliant with the OECD recommandations for QSAR modeling (OECD, 2004) (4). The QSAR model is based on validated data from a training set of 40 chemicals 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, this approach is based on validated data derived from 72-hour ErL50 tests on algae, for which the concentrations of the test item had been determined by chemical analyses over the test period.

(1) OECD Guideline for testing of chemicals No. 201, "Freshwater Alga and Cyanobacteria, Growth Inhibition Test", adopted March 23, 2006; Annex 5 corrected July 28, 2011.
(2) Commission Regulation (EC) No. 761/2009 amending Regulation (EC) No. 440/2008, Part C, C.3.: "Algal Inhibition Test", p. 36-56, Official Journal of the European Union (EN), dated August 24, 2009, L 220:1-94.
(3) Bicherel P and Thomas PC (2014) iSafeRat® WAF calculation method to predict acute aquatic toxicity. Position paper prepared by KREATiS.
(4) OECD (2004) Principles for the validation, for regulatory purposes, of (Quantitative) Structure Activity-Relationship Models, http://www.oecd.org/env/ehs/risk-assessment/oecdquantitativestructure-activityrelationshipsprojectqsars.htm.
GLP compliance:
no
Remarks:
Not required for a calculation based on multiple QSARs method.
Specific details on test material used for the study:
Typical legal entity composition provided by the registrant of the substance, REACH NCS Sesquiterpenes HC / Alc consortium. Composition is as agreed in the Substance Identification Profile version-4.1 dated 14 August 2017. See test material information: Cedarwood texas oil (cedrene) (QSAR)

Analytical monitoring:
no
Remarks:
Not relevant for a calculation based on multiple QSARs method
Details on sampling:
Not relevant.
Test organisms (species):
other: green algae
Water media type:
freshwater
Total exposure duration:
72 h
Key result
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 163 mg/L
Nominal / measured:
nominal
Conc. based on:
other: Water Accomodated Fraction
Basis for effect:
growth rate
Remarks on result:
other: Calculation based on QSARs/nominal solubility limit
Remarks:
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.
Details on results:
The Analytically Measurable Aqueous Phase is maximum 2.07 mg/L of the test item and the Water Accommodated Fraction (WAF) maximum is 163 mg/L. Using a loading rate of 163 mg/L, i.e. at the maximal solubility of the UVCB in water, and after removal of the non-bioavailable fraction, the remaining solubilised fraction is not sufficient to exert any toxicity effect based growth rate observations. Therefore it is not possible to determine a 72h-ErL50 below the water solubility limit.
Validity criteria fulfilled:
yes
Remarks:
QSAR model validated to be compliant with the OECD recommendation for QSAR modelling (OECD, 2004) described within the QMRF.
Conclusions:
The 72h ErL50 (mg test item.L-1) = above the water solubility limit (> 163 mg/L)

Executive summary:

A calculation method was used to predict the inhibition of algal growth exposed to the test item Cedarwood texas oil (cedrene). 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", (1) referenced as Method C.3 of Commission Regulation No. 440/2008 (2) adapted for testing of a mixture using the WAF method. By using a "known constituents approach" based on non-polar-narcosis MOA-1 QSARs and WAF "adapted water solubilities”, the algae 72h-ErL50 is concluded to be above the WAF estimated at 163 mg/L.

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
November 30th 2017
Reliability:
2 (reliable with restrictions)
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:
Cedarwood Texas oil (Thujopsene) is an UVCB substance. Regarding the different solubility of its constituents that make the testing difficult and a known fraction 95.5%, calculation from the ecotoxicity of the known constituent appears as an acceptable approach.
Principles of method if other than guideline:
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", (1) referenced as Method C.3 of Commission Regulation No. 440/2008 (2) adapted for testing of a mixture using the WAF method. The criterion measured was the median effective loading rate of the mixture ErL50 (Median Effective Loading for specific growth rate), a statistically derived loading rate 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 a validated calculation method for the Mode of Action (MOA) in question (non-polar narcosis). It has been validated in an internal publication for MOA 1 (non-polar narcosis) and acute exposure (Bicherel and Thomas, 2014) (3). The algorithm is based on a QSAR model which has been validated to be compliant with the OECD recommandations for QSAR modeling (OECD, 2004) (4). The QSAR model is based on validated data from a training set of 40 chemicals 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, this approach is based on validated data derived from 72-hour ErL50 tests on algae, for which the concentrations of the test item had been determined by chemical analyses over the test period.

(1) OECD Guideline for testing of chemicals No. 201, "Freshwater Alga and Cyanobacteria, Growth Inhibition Test", adopted March 23, 2006; Annex 5 corrected July 28, 2011.
(2) Commission Regulation (EC) No. 761/2009 amending Regulation (EC) No. 440/2008, Part C, C.3.: "Algal Inhibition Test", p. 36-56, Official Journal of the European Union (EN), dated August 24, 2009, L 220:1-94.
(3) Bicherel P and Thomas PC (2014) iSafeRat® WAF calculation method to predict acute aquatic toxicity. Position paper prepared by KREATiS.
(4) OECD (2004) Principles for the validation, for regulatory purposes, of (Quantitative) Structure Activity-Relationship Models, http://www.oecd.org/env/ehs/risk-assessment/oecdquantitativestructure-activityrelationshipsprojectqsars.htm.
GLP compliance:
no
Remarks:
Not required for a calculation based on multiple QSARs method.
Specific details on test material used for the study:
Typical legal entity composition provided by the registrant of the substance, REACH NCS Sesquiterpenes HC / Alc consortium. Composition is as agreed in the Substance Identification Profile version-4.1 dated 14 August 2017. See Test material information: Cedarwood Texas oil (Thujopsene) (QSAR)

Analytical monitoring:
no
Remarks:
Not relevant for a calculation based on multiple QSARs method
Details on sampling:
Not relevant.
Test organisms (species):
other: green algae
Water media type:
freshwater
Total exposure duration:
72 h
Key result
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 31.1 mg/L
Nominal / measured:
nominal
Conc. based on:
other: Water Accomodated Fraction
Basis for effect:
growth rate
Remarks on result:
other: Nominal solubility limit/ Calculation based on QSARs.
Remarks:
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.
Details on results:
The Analytically Measurable Aqueous Phase is maximum 2.07 mg/L of the test item and the Water Accommodated Fraction (WAF) maximum is 31.1 mg/L. Using a loading rate of 31.1 mg/L, i.e. at the maximal solubility of the UVCB in water, and after removal of the non-bioavailable fraction, the remaining solubilised fraction is not sufficient to exert any toxicity effect based growth rate observations. Therefore it is not possible to determine a 72h-ErL50 below the water solubility limit.
Validity criteria fulfilled:
yes
Remarks:
QSAR model validated to be compliant with the OECD recommendation for QSAR modelling (OECD, 2004) described within the QMRF.
Conclusions:
The 72h ErL50 (mg test item.L-1) = above the water solubility limit (> 31.1 mg/L)

Executive summary:

A calculation method was used to predict the inhibition of algal growth exposed to the test item Cedarwood Texas oil (Thujopsene). 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", (1) referenced as Method C.3 of Commission Regulation No. 440/2008 (2) adapted for testing of a mixture using the WAF method. By using a "known constituents approach" based on non-polar-narcosis MOA-1 QSARs and WAF "adapted water solubilities”, the algae 72h-ErL50 is concluded to be above the WAF estimated at 31.1 mg/L.

Description of key information

A calculation method was used to predict the inhibition of algal growth exposed to the test item Cedarwood Texas distilled Terpenes 1 (Cedrene). 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", (1) referenced as Method C.3 of Commission Regulation No. 440/2008 (2) adapted for testing of a mixture using the WAF method. By using a "known constituents approach" based on non-polar-narcosis MOA-1 QSARs and WAF "adapted water solubilities”, the algae 72h-ErL50 is concluded to be above the WAF estimated at 163 mg/L.

Similarly, a calculation method was used to predict the inhibition of algal growth exposed to the test item Cedarwood Texas distilled Terpenes 2(Thujopsene). 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", (1) referenced as Method C.3 of Commission Regulation No. 440/2008 (2) adapted for testing of a mixture using the WAF method. By using a "known constituents approach" based on non-polar-narcosis MOA-1 QSARs and WAF "adapted water solubilities”, the algae 72h-ErL50 is concluded to be above the WAF estimated at 31.1 mg/L.

Key value for chemical safety assessment

Additional information

For both Cedarwood Texas distilled Terpene qualities, the ErL50 values were therefore estimated above their WAF solubilities, at least > 31.1 mg/L.