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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
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:
The executive summary of the QSAR prediction is presented in the endpoint summary. The QMRF and QPRF documentation files are included in the Attached justification section.
Reference:
Composition 0
Qualifier:
according to
Guideline:
other: REACH Guidance R.6: QSARs and grouping of chemicals. Version May 2008.
Version / remarks:
In the QMR attached the model specifications are presented. In this QMR is referenced to the Methodology document for the Ecological Structure-Activity Relationship model (ECOSAR) Class Program MS Windows v1.11'. United States Environmental Protection Agency, Office of Pollution Prevention and Toxics, Washington DC (2012).
Deviations:
not applicable
GLP compliance:
no
Remarks:
not required
Test material information:
Composition 1
Test organisms (species):
Daphnia sp.
Water media type:
freshwater
Total exposure duration:
48 h
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
14.1 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: Log Kow 2.82; ECOSAR class: Esters
Validity criteria fulfilled:
yes
Remarks:
The ECOSAR-Ester equation is valid when using the OECD criteria. In addition, N=40 and R2 is 0.798
Conclusions:
The Daphnia 48-h EC50 is 14.1 mg/L
Executive summary:

The acute Daphnia EC50 for the ester Herbacet #1 is predicted to be 14.1 mg/L based on the ECOSAR SAR for esters using an estimated log Kow of 2.82, molecular weight of 166.2 and the equation: Log 48h-LC50 (mmol/L) = -0.6305 (log Kow) + 0.7049. The LC50 in ECOSAR is considered equivalent to the EC50 as defined in OECD TG 202.

Herbacet #1 is in the applicability domain of the ECOSAR prediction because: a) Herbacet #1 is an ester; b) its log Kow is 2.82 (=< 5); c) its MW is 166.2 (< 1000); and; d) the toxicity predicted is below its measured water solubility of 739 mg/L.

The measured and predicted log Kow’s of Herbacet #1 are very similar (2.8 and 2.82, respectively). The closest analogue in the training set is Octyl lactate, with a log Kow of 2.8 and a molecular weight of 202. The predicted EC50 value of this ECOSAR analogue is 18.6 mg/L and the measured value is 37 to 45 mg/L, presenting the limited uncertainty of the prediction for Octyl lactate and therefore for Herbacet #1.

The fit in the applicability domain and the availability of an analogue in the training set results in limited uncertainty of the Herbacet #1 prediction. This shows that the prediction is reliable and a Klimisch 2 can be assigned. In accordance with REACH Annex XI, the validity of the (Q)SAR is documented in a QMR for acute Daphnia toxicity on esters. The adequate and reliable documentation, presented in the attached justification section, further supports this prediction.

Description of key information

The acute Daphnia EC50 for the ester Herbacet #1 is predicted to be 14.1 mg/L based on the ECOSAR SAR for esters using an estimated log Kow of 2.82, molecular weight of 166.2 and the equation: Log 48h-LC50 (mmol/L) = -0.6305 (log Kow) + 0.7049. The LC50 in ECOSAR is considered equivalent to the EC50 as defined in OECD TG 202.

Herbacet #1 is in the applicability domain of the ECOSAR prediction because: a) Herbacet #1 is an ester; b) its log Kow is 2.82 (=< 5); c) its MW is 166.2 (< 1000); and; d) the toxicity predicted is below its measured water solubility of 739 mg/L.

The measured and predicted log Kow’s of Herbacet #1 are very similar (2.8 and 2.82, respectively). The closest analogue in the training set is Octyl lactate, with a log Kow of 2.8 and a molecular weight of 202. The predicted EC50 value of this ECOSAR analogue is 18.6 mg/L and the measured value is 37 to 45 mg/L, presenting the limited uncertainty of the prediction for Octyl lactate and therefore for Herbacet #1.

The fit in the applicability domain and the availability of an analogue in the training set results in limited uncertainty of the Herbacet #1 prediction. This shows that the prediction is reliable and a Klimisch 2 can be assigned. In accordance with REACH Annex XI, the validity of the (Q)SAR is documented in a QMR for acute Daphnia toxicity on esters. The adequate and reliable documentation, presented in the attached justification section of the study record, further supports this prediction.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
14.1 mg/L

Additional information