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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:
October 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 below in the Attached justification section.
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 v1.11'. United States Environmental Protection Agency, Office of Pollution Prevention and Toxics, Washington DC (2012).
GLP compliance:
no
Remarks:
not required
Test organisms (species):
Daphnia sp.
Water media type:
freshwater
Total exposure duration:
48 h
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
2.4 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: Log kow 3.8; ECOSAR class: Neutral organics
Validity criteria fulfilled:
yes
Remarks:
The substance is in the applicability domain of the model and the scientific validity of the model is met as presented in the QMR.
Conclusions:
The Daphnia 48-h EC50 is 2.4 mg/L.
Executive summary:

The acute Daphnia EC50 for the neutral organic Dimeth Cyclormol is predicted to be 2.4 mg/l based on the ECOSAR SAR for neutral organics using an experimental log Kow of 3.8,molecular weight of 178.28 and the equation: Log 48h-LC50 (mmol/L) = -0.858 log Kow + 1.3848.

Dimeth Cyclormol is in the applicability domain of the ECOSAR prediction because: a) Dimeth Cyclormol is a neutral organic presenting the toxicity solely by its bioavailability (i.e. without fragments that activate this neutral organic); b) its log Kow is 3.8 (= < 5); c) its MW is 178.28 (< 1000); and; d) the toxicity predicted is below its water solubility of 467.3 mg/l.

For the prediction the measured log Kow (3.8) is used because the predicted log Kow (2.8) is more than 0.5 unit different (lower) compared to the measured one (IFF criterion). The uncertainty of the prediction is further minimised because ECOSAR two analogues are present with a similar predicted log Kows and with experimental and predicted values within a factor 3. This is Trans-Anethole (CAS 4180-23-8, Log Kow of 3.4 (EPI) and molecular weight of 148) and 1,2,4-Trichlorobenzene (CAS 120-82-1, Log Kow of 3.9 (EPI) and molecular weight of 182). For trans-Anethole the experimental versus the predicted Daphnia toxicity is 7.8 versus 4.45 mg/l. For 1,2,4-Trichlorobenzen the experimental versus the predicted values are 2.7/0.7 (two measured values are available) versus 1.88 mg/l, showing limited uncertainty of the prediction for these substances and thus also for Dimeth Cyclormol.

The fit in the applicability domain and the availability of analogues in the training set results in limited uncertainty of the Dimeth Cyclormol 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 neutral organics (see attached report). The adequate and reliable documentation, presented below, further supports this prediction.

Description of key information

The acute Daphnia EC50 for the neutral organic Dimeth Cyclormol is predicted to be 2.4 mg/l based on the ECOSAR SAR for neutral organics using an experimental log Kow of 3.8,molecular weight of 178.28 and the equation: Log 48h-LC50 (mmol/L) = -0.858 log Kow + 1.3848.

Dimeth Cyclormol is in the applicability domain of the ECOSAR prediction because: a) Dimeth Cyclormol is a neutral organic presenting the toxicity solely by its bioavailability (i.e. without fragments that activate this neutral organic); b) its log Kow is 3.8 (= < 5); c) its MW is 178.28 (< 1000); and; d) the toxicity predicted is below its water solubility of 467.3 mg/l.

For the prediction the measured log Kow (3.8) is used because the predicted log Kow (2.8) is more than 0.5 unit different (lower) compared to the measured one (IFF criterion). The uncertainty of the prediction is further minimised because ECOSAR two analogues are present with a similar predicted log Kows and with experimental and predicted values within a factor 3. This is Trans-Anethole (CAS 4180-23-8, Log Kow of 3.4 (EPI) and molecular weight of 148) and 1,2,4-Trichlorobenzene (CAS 120-82-1, Log Kow of 3.9 (EPI) and molecular weight of 182). For trans-Anethole the experimental versus the predicted Daphnia toxicity is 7.8 versus 4.45 mg/l. For 1,2,4-Trichlorobenzen the experimental versus the predicted values are 2.7/0.7 (two measured values are available) versus 1.88 mg/l, showing limited uncertainty of the prediction for these substances and thus also for Dimeth Cyclormol.

The fit in the applicability domain and the availability of analogues in the training set results in limited uncertainty of the Dimeth Cyclormol 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 neutral organics (see attached report). The adequate and reliable documentation, presented below, further supports this prediction.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
2.4 mg/L

Additional information