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Long-term toxicity to aquatic invertebrates

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Description of key information

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater invertebrates:
208 mg/L

Additional information

Results from fully reliable studies on chronic toxicity of methanol to aquatic invertebrates are not available.

The results of a 21 d study on the toxicity of methanol on Daphnia magna are reported in a publication of Dom et al. (2012). The study reports a NOEC of 122 mg/L for reproduction of Daphnis magna. The reliability of this study is however questionable. It can be expected that significant oxygen consumption due to the presence of micro-organisms may have impacted the study outcomes despite the semi-static conditions.

Additionally, several short-term toxicity study are available for aquatic invertebrates, all consistently demonstrating a very low acute toxicity of methanol.

Methanol is a simple organic compound and contains only C, H and O atoms, excluding alpha-beta unsaturated carbonyl groups as electrophilic functionalities. Baseline toxicity is expected therefore for methanol (Schüürmann et al., Chem. Res. Toxicol., 18: 536 -555).

Since methanol exerts toxicity with a non-specific mode of action (narcotic toxicity), the chronic toxicity to Daphnia magna can be reasonably extrapolated from acute data using an acute to-chronic ratio of 10 (Raimondo et al., Environ. Toxicol. Chem. 26, 2007; Roex at al., Environ. Toxicol. Chem. Cryo Letters. 2004 Nov-Dec; 25(6):415-2419, 2000).

Estimates of long-term toxicity for Daphnia magna carried out with the OECD QSAR Toolbox v 3.1 (using category approach and trend analysis) predict a NOEC (21 d) value for Daphnia magna of 208 mg/L . This value is in good agreement with the chronic value extrapolated from the acute data and confirms the low toxicity of methanol for Daphnia magna even under long-term exposure conditions. The prediction fulfils the OECD criteria on evaluation on QSARs and grouping of chemicals:

Algorithm used for the prediction:

NOEC (log(1/mol/L)) = 2.76(+/-0.40) + 0.898(+/-0.121) * logKow

Applicability domain:

1) Referential boundary:

The target chemical should be classified as Basesurface narcotics by Acute aquatic toxicity MOA by

OASIS

2) Referential boundary:

The target chemical should be classified as Discrete chemical by Substance Type

3) Referential boundary:

The target chemical should be classified as Neutral Organics by Aquatic toxicity classification by

ECOSAR

4) Referential boundary:

The target chemical should be classified as Amides OR Substituted Ureas OR Vinyl/Allyl Halides by

Aquatic toxicity classification by ECOSAR

5) Parametric boundary:

The target chemical should have a value of log Kow which is >= -1.76

6) Parametric boundary:

The target chemical should have a value of log Kow which is <= 5.97

The target chemical FALLS within applicability domain of the prediction.

Adequcy of prediction:

Model satistic: r² = 0.859, r²adj = 0.855, s 0 0.611

Mechanistic interpretation:

Mechanistic basis of the model is the reversible, drug-induced loss of consciousness (general anaesthesia), better known as baseline toxicity

The predicted NOEC is therefore used as key value for chemical safety assessment