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Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

Link to relevant study record(s)

Description of key information

Magnesium methanolate hydrolyses rapedly in contact with moisture or water into methanol and magnesium hydroxide (detailed description in section 5.1.2). Both hydrolysis products are natural occuring substances and according to the available data are not dangerous for aquatic organisms and no classification is required.

Hydrolysis product methanol:

The toxicity threshold of methanol for the alga Scenedesmus quadricauda after an exposure of 8 days was reported to be at 8000 mg/L (Bringmann and Kuehn, 1978). EC50 reported by Stratton (1987) with different test species of blue-green algae range between 20300 - 43290 mg/L. The average concentration causing 50% inhibition in growth rate was found to be at 28400 mg/L during an exposure period of 10 – 14 days (Stratton and Smith, 1988). Cho et al. (2008) in a 96h test period report a concentration causing 50% inhibition in growth rate of 22000 mg/L for the green algae Selenastrum capricornutum in a 96h well documented test conducted according to OECD 201 Guideline.

According to the available data, the hydrolysis product methanol can be considered as not harmful to aquatic algae.

Hydrolysis product magnesium hydroxide:

The key study concluded that Magnesium hydroxide slightly reduced growth rate and inhibited the yield of this fresh water algae species at 100 mg/l, being the highest test concentration. In conclusion, both the EC50 for growth rate reduction (ErC50: 0-72h) and the EC50 for yield inhibition (EyC50:0-72h) exceeded an analytically confirmed concentration of 100 mg/l.

The supporting study concludes that the Magnesium ion was tolerated extremely well by Chlorella vulgaris. This may be influenced by the fact that magnesium is the central atom in the chlorophyll molecule. 56 ions were tested for the tolerance of Chlorella towards them, and it was found that magnesium had the lowest inhibitory effect.

According to the available data, the hydrolysis product magnesium hydroxide can be considered as not harmful to aquatic algae .

Key value for chemical safety assessment

Additional information