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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:
August 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 prediction is presented in this justification section. Full documentation of QPR and QMR are attached in the files.
The 48h acute Daphnia EC50 for the neutral organic substance Diola (hexyl methyl ether) is predicted to be 2.30 mg/L based on the ECOSAR for neutral organics using a partition coefficient (log Kow) of 3.6, a molecular weight (MW) of 116.2 and the equation: 48h LC50 (mg/L) = MW x 10^ (-0.858 log Kow + 1.3848).
Diola is in the applicability domain of the ECOSAR prediction because: a) Diola is an ether presenting the toxicity solely by its bioavailability (i.e. without fragments that activate this neutral organic); b) its predicted log Kow is 2.52 (measured 3.6) (=<8.0); c) its MW is 116.2 (< 1000); and d) the toxicity predicted is below its predicted water solubility of 726.2 mg/L (measured = 660.9 mg/L).
There is limited uncertainty. The difference between the predicted and the measured values of Diola for its log Kow is greater than 0.5 (2.5 and 3.6, respectively). This difference is outside our validity criteria. Therefore the measured value of log Kow will be used in the ECOSAR equation, which is a conservative approach. The ECOSAR substance in the training set with a similar log Kow as Diola shows a measured value similar to the predicted one (< a factor of 2). This further supports the limited uncertainty of the prediction.
The fit in the applicability domain and the availability of a substance with a similar log Kow in the training set further presents the reliability of the value derived 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 neutral organics (see attached report). The adequate and reliable documentation presented, further supports this prediction.
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 Programm MS Windows v1.1'. United States Environmental Protection Agency, Office of Pollution Prevention and Toxics, Washington DC (2011).
GLP compliance:
no
Test organisms (species):
Daphnia sp.
Water media type:
freshwater
Total exposure duration:
48 h
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
2.3 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: ECOSAR class: Neutral organics
Validity criteria fulfilled:
yes
Remarks:
The substance is in the applicability domain of the ECOSAR - neutral organic model.
Conclusions:
The Daphnia 48-h EC50 is 2.30 mg/L using ECOSAR - Neutral organic equation.

Description of key information

The EC50 for Daphnia was calculated to be 2.30 mg/l based on ECOSAR - Neutral organic model.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
2.3 mg/L

Additional information