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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Remarks:
EC10/NOEC
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 derivation of chronic algae toxicity is presented:
The chronic algae toxicity for the neutral organic substance Diola (hexyl methyl ether) is predicted to be 1.15 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: 96h ChV(mg/L) = MW x 10^ (-0.6029 Log Kow + 0.1648).
Diola is categorised as a neutral organic and fits in the applicability domain. The measured value of log Kow will be used because the predicted value log Kow is more than a factor 0.5 lower compared to the measured on (2.5 versus 3.6, respectively), which is a conservative approach. The data used for deriving the regression equation can deviate around a factor of three from the regression line. Therefore the predicted versus the measured value may also differ a factor of 3. The ECOSAR substance in the training set with a similar log Kow as Diola presents a similar measured and predicted value (difference < factor 2) supporting the limited uncertainty. This means 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 chronic algae toxicity on neutral organics. The adequate and reliable documentation presented further supports this prediction.
Qualifier:
according to
Guideline:
other: REACH guidance R.6
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
1.15 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
growth rate
Validity criteria fulfilled:
yes
Remarks:
The substance is in the applicability domain of the scientific valid model.
Conclusions:
The EC10/NOEC is 1.15 mg/l based on the ECOSAR Neutral Organic equation
Endpoint:
toxicity to aquatic algae and cyanobacteria
Remarks:
ErC50 at 72h
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 presetent. The accompanying files are attached.
The acute algae ErC50 for the neutral organic substance Diola (hexyl methyl ether) is predicted to be 3.15 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: Log 96h-ErC50 (mmol/L) = -0.6922 log Kow + 0.9253. 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 of the prediction. The measured value of log Kow will be used instead of the predicted one because the difference in log Kow is > 0.5, which is a conservative approach. The prediction will have the similar uncertainty as the regression equation. The acute algae toxicity data from the ECOSAR substance in the training set show that the variation between predicted and measured is < 2. This further supports the limited uncertainty.
The fit in the applicability domain and the availability of a substance with a similar log Kow in the training set, with a similar predicted and measured value, results in limited uncertainty of the predicted EC50 algae value for the substance. 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 algae toxicity on neutral organics (see attached report). The adequate and reliable documentation presented further supports this prediction.
Reason / purpose:
(Q)SAR model reporting (QMRF)
Guideline:
other: REACH Guidance R.6: QSARs and grouping of chemicals. Version May 2008.
GLP compliance:
no
Test organisms (species):
other: green algae
Water media type:
freshwater
Total exposure duration:
96 h
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
3.15 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: ECOSAR class: Neutral organics (ether)
Details on results:
The ErC50 is 3.15 mg/l.
Validity criteria fulfilled:
yes
Remarks:
The substance is in the applicability domain of the scientific valid model.
Conclusions:
The 96-h ErC50 is 3.15 mg/L based on the ECOSAR Neutral Organic prediction model.

Description of key information

The EC50 for algae is 3.15 mg/l and EC10/NOEC is 1.15 mg/l using the ECOSAR Neutral Organics model. 

Key value for chemical safety assessment

EC50 for freshwater algae:
3.15 mg/L
EC10 or NOEC for freshwater algae:
1.15 mg/L

Additional information