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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The acute toxicity of methanol was reported with an ErC50(96h) value of 22000 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
22 000 mg/L

Additional information

One toxicity study on alga is available for sodium methanolate. However, in the aquatic environment due to the rapid hydrolysis of the compounds the toxicity of the degradation products, sodium hydroxide and methanol are also relevant. The studies are listed in Table 1 below, reporting differently reliable studies on the test substance as well as its degradation products.

 

The toxicity of sodium methanolate to Scenedesmus subspicatus was tested according to DIN 38412 part 12 (no GLP, no analytical monitoring; study director 1989c). Since the available data were insufficient for assessment, the study was classified as not assignable according to the Klimisch code. Sodium methanolate revealed an EC50(24h) of 302.2 mg/L for the assimilation inhibition for the species Scenedesmus subspicatus supporting the low acute toxicity of sodium methanolate.

A publication by Cho et al. (2008) determined effects of methanol on Selenastrum capricornutum according to OECD 201, with a reported endpoint of ErC50(96h) of 22.000 mg/L. Three further studies are available on effects of methanol on different algae species and reported toxic threshold values from 530 mg/L, however EC50 values from 20300 mg/L with studies over 10 to 14 days.

A valid algal test is not possible for sodium hydroxide: according to OECD 201 guideline the pH of the test solutions should not normally deviate by more than one unit during the test. The results can be predicted based on the increase of the pH of the test solution (OECD SIDS sodium hydroxide, 2002). However, the results will depend on the algal species selected and the composition of the test medium and its buffer capacities and will not reflect the variable conditions in the environment.

With release of sodium hydroxide into the environment, there can be a significant variation of the natural pH in receiving aquatic ecosystems. There will be differences in sensitivity of ecosystems to pH change and the different buffer capacities of ecosystem and hence different responses to change in pH in exposed ecosystems. Each respective release will require the need to assess the environmental effect in terms of the hydroxide component of sodium methanolate into the environment or a sewage treatment plant.

Table 1: Available studies with endpoints and reliabilities for sodium methanolate and its metabolite methanol.

Sodium methanolate

Species

Parameter

Effects

Reference

Klimisch

Scenedesmus subspicatus

EC50(24h),

assimilation inhibition

302.2 mg/L

89-0460-DKO

RL4

Methanol

Species

Parameter

Effects

Reference

Klimisch

Selenastrum capricornutum

ErC50(96h)

22000 mg/L

Cho et al., 2008

RL2

Anabaena spp./Nostoc sp.

EC50(10 -14d)

20300-43290 mg/L

Stratton, 1987

RL2

Chlorella pyrenoidosa

EC50(10 -14d)

28440 mg/L

Stratton and Smith, 1988

RL2

Scenedesmus quadricauda

TGK(8d)

8000 mg/L

Bringmann and Kuehn, 1978

RL2

 Microcystis aeruginosa  TGK(8d)  530 mg/L

Bringmann and Kuehn, 1978

RL2