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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
19 April 2018 - 19 April 2018
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:
Himalayan Cedarwood oil is an UVCB substance. Regarding the different solubility of its constituents that make the testing difficult and a known fraction of 91.57%, calculation from the ecotoxicity of the known constituent appears as an acceptable approach.
Principles of method if other than guideline:
A calculation method was used to predict the inhibition of algal growth exposed to the test item Himalayan Cedarwood oil, a Natural Complex Substance, using the WAF method. 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 Mechanism of Action (MechoA) in question (MechoA 1, i.e. narcosis) (3). This method has previously been validated in an internal publication for acute exposure of non-polar narcosis compounds (Bicherel and Thomas, 2014) (4). The algorithm is based on a QSAR model which has been validated to be compliant with the OECD recommendations for QSAR modeling (OECD, 2004; OECD, 2007) (5,6). 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. Furthermore 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) Bauer, F.J., Thomas, P.C., Fouchard, S.Y., and Neunlist, S.J.M. (2018). A new classification algorithm based on mechanisms of action. Comput. Toxicol. 5, 8–15.
(4) Bicherel P and Thomas PC (2014) iSafeRat® WAF calculation method to predict acute aquatic toxicity. Position paper prepared by KREATiS.
(5) 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
(6) OECD (2007) Guidance document on the validation of (Quantitative)Structure-Activity Relationships [(Q)SAR] models. ENV/JM/MONO(2007)2. Environment Directorate OECD. Paris. Mars 2007.
GLP compliance:
no
Remarks:
Not required for a calculation based on multiple QSARs method.
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.:
8.8 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
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.
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 72 hour ErL50 of Himalayan Cedarwood oil was concluded 8.8 mg/L.
Executive summary:

A calculation method was used to predict the inhibition of algal growth exposed to the test item Himalayan Cedarwood oil, a Natural Complex Substance, using the WAF method. 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", referenced as Method C.3 of Commission Regulation No. 440/2008  adapted for testing of a mixture using the WAF method. The test item falls within the applicability domain of the model and was therefore reliably predicted for its toxicity (72h-ErC50) to algae. 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 8.8 mg/L.

Description of key information

A calculation method was used to predict the inhibition of algal growth exposed to the test item Himalayan Cedarwood oil, a Natural Complex Substance, using the WAF method. 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", referenced as Method C.3 of Commission Regulation No. 440/2008  adapted for testing of a mixture using the WAF method. The test item falls within the applicability domain of the model and was therefore reliably predicted for its toxicity (72h-ErC50) to algae. 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 8.8 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
8.8 mg/L

Additional information