Magnesium ethanolate

Long-term toxicity to aquatic invertebrates

Description of key information

Magnesium ethanolate hydrolyses rapidly in contact with moisture or water (t1/2<1 minute) into ethanol and magnesium hydroxide (detailed description in section 5.1.2). Ethanol and magnesium hydroxide are natural occuring substances. Magnesium ethanolate and ethanol are readily biodegradable. No long-term risk is expected for magnesium ethanolate and for the hydrolysis products ethanol or magnesium hydroxide.

Valid long-term toxicity data for invertebrates are available for the organic hydrolysis product ethanol.

Hydrolysis product ethanol:

Different species (molluscs, shrimps, fish, daphnia) were tested with respect to long-term effects on mortality and reproduction/developmental toxicity. The EC50 values for mortality are well above 100 mg/l and for reproduction/developmental toxicity approximately 10 mg/l.

Magnesium ethanolate hydrolyses rapidly in contact with moisture or water (t1/2<1 minute) into ethanol and magnesium hydroxide (detailed description in section 5.1.2). Ethanol and magnesium hydroxide are natural occuring substances. Magnesium ethanolate and ethanol are readily biodegradable. No long-term risk is expected for magnesium ethanolate and for the hydrolysis products ethanol or magnesium hydroxide.

Valid long-term toxicity data for invertebrates are available for the organic hydrolysis product ethanol.

Hydrolysis product ethanol:

Different species (molluscs, shrimps, fish, daphnia) were tested with respect to long-term effects on mortality and reproduction/developmental toxicity. The EC50 values for mortality are well above 100 mg/l and for reproduction/developmental toxicity approximately 10 mg/l.

Additional information

There are no studies available that provide useful and reliable information on the long term toxicity of magnesium ethanolate [MgOEt] to invetebrates. All available results are obtained from studies using ethanol, the hydrolysis product of MgOEt. A waiver is therefore used since the chemical safety assessment according to Annex IX, 9.1., column 2 of the REACH regulation does not indicate the need to further investigate the effects on aquatic organisms, and therefore chronic testing in invertebrates is not justified.

Ethanol:

In a very well reported invertebrate reproduction study, Daphnia magna were exposed to ethanol over a period of approximately 10 days, sufficient for the production of 3 broods of offspring. An LC50 of 454mg/l was reported for the adults but a much lower NOEC of 9.6mg/l was reported for the reproduction test, based on criteria of total progeny, number of broods and mean brood size. In the same study, Ceriodaphnia dubia were similarly exposed. An LC50 of 1806mg/l was reported for the adults and the same NOEC of 9.6mg/l as for the D magna and based on the same findings.  A very low NOEC of 2mg/l was reported for the Ceriodaphnia adults, but it was unclear what exact end points were used for this or why this figure was vastly lower than the LC50. For this reason, the NOEC for this study is based on the reproduction end point.

In a study to assess the sensitivity of the grass shrimp developmental cycle to the ethanol, a 4 day assay, was used to determine the acute toxicity of embryos from the daggerblade grass shrimp (Palaemonetes pugio) to ethanol. This test (known as SEATOX) included exposure through the development prior to hatch and through the time of hatch, which is regarded as a critical life stage of these embryos and this species. The LC50 obtained was 12.07g/l, which suggests that Ethanol is not acutely toxic to invertebrate embryos.

In two studies to assess the sensitivity of the grass shrimp developing embryos to ethanol, embryos from the daggerblade grass shrimp were exposed to the test substance from the tissue cap stage embryo stage (day 3 - late gastrula) through to 2 days post hatch, a total of 12 days exposure in a test known as the "Shrimp embryo teratogenesis assay - Palaemonid" or SETAP.  In the first study, the LC50 obtained based on mortality was 3.63g/l, which suggests that ethanol is not acutely toxic to invertebrate embryos. However, the NOEC based on developmental toxicity, in this case developmental delay, was 79mg/l. In the second study, the reported LC50 for embryo mortality was 0.53g/l.  A NOEC was not reported.

In a 21 day daphnia reproduction study that used ethanol as a vehicle, a single concentration of 0.001% ethanol (approximately 10mg/l) had no adverse effects on any of the reproductive parameters monitored for the daphnia magna test species. However,

another study examined the influence of varying a number of parameters on daphnia reproduction, including the presence of carrier solvents such as ethanol. A single concentration of ethanol of 7.9mg/l was found to significantly increase the fecundity of daphnia (increased number of broods and number of young) under the standard photoperiod. A higher level of feed (7.5 -15x) was used than the OECD protocol permits. (Higher still levels of feed still increased the fecundity but by a lower factor.) The authors reported that the reasons for the effect of ethanol on fecundity remain unclear. The study reports other work on acetone (the other solvent examined in this study) that reported conflicting results suggesting that there is a variability in reproductive end points between species and clones of daphnids. ecause there was only a single dose examined and because a high level of feed was used, which the study itself indicates influences outcome and because the impact was an increase in fecundity, it is difficult to interpret this study in terms of defining a critical NOAEC, so this result cannot be used as a key study.

In a multigeneration study, the freshwater tropical snail Biomphalaria tenagophila was exposed to ethanol for a period of 8 weeks. Three dose levels were used with geometric spacing to cover a wide concentration range (20, 200, 2000mg/l approx). Significant adverse effects were seen at the two highest doses tested in all three generations (F0, F1, F2), manifest as reduced fecundity (reduced egg masses produced) and developmental effects (increased mortality, malformations and later hatching times.) Whilst there was a trend towards adverse effects in the incidence of malformations in both the F1 and F2 generations at the lowest dose, this was not a statistically significant increase. However, there was a significant increase in hatching times in the F2 generation. On this basis, a no effect level was not found, however, for all other effects apart from hatching time (F2) the NOAEL was 20mg/l.