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Methanol is the first and simplest member of the series of aliphatic alcohols. Like other non-reactive, non-ionizable organic chemicals ("neutral organics") such as ketones, ethers, alkyl halides, aryl halides and aromatic hydrocarbons methanol is expected to exert toxicity to aquatic species through simple narcosis.

A large amount of data on the toxicity of methanol is available for a broad spectrum of aquatic organisms (fish, invertebrates and algae).

The results from the most reliable and relevant available studies are listed below

Short-term toxicity

Fish

LC50 (96h) = 28100 mg/L                            Pimephales promelas

LC50 (96h) = 20100 mg/L                            Oncorhynchus mykiss

LC50 (96h) = 15400 mg/L                           Lepomis macrochirus

Daphnids

EC50 (48h) = 18000 mg/L                             Daphnia magna

EC50 (48h) > 10000 mg/L                            Daphnia magna

Green algae

EC50 (96h) ca. 22000 mg/L                         Selenastrum capricornutum

Microorganisms

EC 50: 19800 mg/L                                      activated sludge

IC50: >1000 mg/L                                        activated sludge

IC50: 880 mg/L                                            Nitrosamonas

toxic limit concentration: 530 - 6600 mg/L     Pseudomonas, Microcystis aeruginosa.

All the available data demonstrate consistently the very low acute toxicity to methanol for aquatic organisms 

Long-term toxicity

No fully reliable results and no guideline studies are available concerning long-term toxicity of methanol to aquatic species. Given the Biological Oxygen Demand of methanol and its rapid biodegradation, it is indeed difficult to maintain in long-term tests the required levels of oxygen concentration. Due to this aspect, it also difficult to assess the reliability of studies, in which the oxygen concentration is not well documented.

Since methanol belongs to the category of chemicals acting with a non-specific mode of action (simple narcosis) the chronic toxicity to aquatic organism can be reasonably predicted from data on acute toxicity using an appropriate acute-to-chronic ratio. An ACR of 10 has been proposed in the literature for such kind of chemicals(see for example Raimondo et al., Environ. Toxicol. Chem. 26, 2007; Roex at al., Environ. Toxicol. Chem. Cryo Letters. 2004 Nov-Dec; 25(6):415-2419, 2000).

Taking into account the toxicity mode of action of methanol the chronic toxicity to aquatic organisms can be also reasonably predicted using Structure-Activity Relationship models (QSARs).

The available information and the results from toxicity estimations indicate a very low chronic toxicity of methanol to aquatic organisms, with no-effect levels well above the concentrations which are normally used in limit tests on long-tern toxicity.

 

 Fish

NOEC (predicted chronic value): 447 mg/l   Pimephales promelas

NOEC (200h) = 7900 - 15800 mg/L             Oryzias latipes

Daphnids

NOEC (21 d) = 208 mg/L (predicted)           Daphnia magna

NOEC (21 d) = 122 mg/L                              Daphnia magna