Magnesium hydroxide

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

For details and justification of read-across please refer to the attached report in section 13 of IUCLID.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

1 330 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: magnesium chloride

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

1 820 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: magnesium sulphate

Validity criteria fulfilled:

yes

Conclusions:

In conclusion magnesium sulphate and magnesium chloride, and hence the magnesium ion, have a very low toxicity to Daphnia magna (LC50>100 mg/L)

Executive summary:

The aquatic toxicity of magnesium chloride and magnesium sulphate was tested in a daphnia acute toxicity test. The exposure duration was 48 h, test animals were daphnia magna. These biotests were performed following the standard protocols developed by the Environmental Protection Agency (EPA. 1991). The dapnia were exposed to concentration of the test item of 10,000, 5,000, 2,500 and 1,250 mg/L in a moderately hard reconstituted water. After 24 and 48 hours of exposure the mortality of the exposed daphnia was recorded. The 48 h LC50 of magnesium chloride was 1330 mg/L, for magnesium sulphate the LC50 was 1820 mg/L after 96h.

In conclusion magnesium sulphate and magnesium chloride, and hence the magnesium ion, have a very low toxicity to daphnia magna (LC50>100 mg/L).

The study was used are read across for magnesium hydroxide, the recalculated 96h LC50 based on MW would be 815 mg/L (from magnesium chloride) and 882 mg/L (from magnesium sulphate).

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2005-09-23 till 2005-09-23

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Remarks:

Not a GLP study. Also, test material is diluted to 60% in aqueous suspension so the results were recalculated to represent 100% Magnesium hydroxide. Analytical measurements not available.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: US EPA Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms, 2002 EPA-821-R-02-012 and Test method 2021.0

GLP compliance:

no

Specific details on test material used for the study:

Test material: FloMag H (Aqueous suspension of Mg(OH)2 98.8% purity), typical concentration 61.0%

Analytical monitoring:

not specified

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
Chemical stock solutions were freshly prepated on the day of the use with dilution water.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Strain/clone: not available
- Age at study initiation: < 24h
- Method of breeding: internal breeding
- Source: MACTEC cultures
- Feeding during test : no

ACCLIMATION
- Acclimation period: yes
- Acclimation conditions: same as test conditions
- Type and amount of food: algae (Selenastrum carpicornutum) and a yeast/trout chow mixture
- Health during acclimation: no mortality observed

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test temperature:

19.7 - 20.7 °C

pH:

8.0 - 10.1

Dissolved oxygen:

7.9 - 8.6 mg/L

Nominal and measured concentrations:

Nominal concentrations: 96.88, 193.75, 387.50, 775, 1550, 3100 and 6200 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 30 mL cups
- Type: closed
- Material, size, fill volume: plastic, 2cm x 2cm x 4cm (high), 30 mL
- Volume of solution: 25 mL
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source of dilution water: chem prepared mod hard, Perrier/miliQ mix

OTHER TEST CONDITIONS
- Adjustment of pH: no details available
- Photoperiod: 16 h light - 8 h dark
- Light intensity: not available, flourescent

EFFECT PARAMETERS MEASURED
Organisms were observed daily and observations recorded. At test termination, survival was determined by observing, counting and recording the organisms alive, dead or not found. Water quality was monitored daily.

Reference substance (positive control):

yes

Remarks:

NaCL

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

ca. 284.76 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95% CL

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

170.86 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: recalculated for 100% substance

Details on results:

- Behavioural abnormalities: no
- Observations on body length and weight: no
- Other biological observations: no
- Mortality of control: no
- Other adverse effects control: no
- Immobilisation of control: no
- Abnormal responses: no
- Any observations that might cause a difference between measured and nominal values: no
- Effect concentrations exceeding solubility of substance in test medium: no

Results with reference substance (positive control):

- Results with reference substance valid?: yes
- Relevant effect levels:
EC50: 2.18 g/L (95% CI: 1.5 - 3.17 g/L)

Table 1. Percent survival of D. magna at the conclusion of acute toxicity tests using dilutions of the test substance

Control or chemical exposure	Concentration of test substance (mg/L)	Mobility (%) after 48 hours	EC50 (mg/L)
Control	0	100	284.76
Test substance	96.88	95
Test substance	193.75	70
Test substance	387.5	25
Test substance	775	5
Test substance	1550	15
Test substance	3100	5
Test substance	6200	0

 

The EC50 (48h) for D.Magna was recalculated to give a more accurate result with 100% concentration of Magnesium chloride as the original EC50 was calculated with a 60% Magnesium hydroxide concentration. The recalculated EC50 (48h) for D.Magna was determined to be 170.86 mg/L.

Validity criteria fulfilled:

yes

Conclusions:

In a 48 hour acute static definitive toxicity test with Daphnia magna, the EC50 value was determined to be 284.76 mg of test substance (61% Mg(OH)2 aqueous suspension).
The recalculated EC50(48h) with pure magnesium hydroxide for D.Magna was determined as 170.86 mg/L.

Executive summary:

The acute toxicity of the test material, a solution of about 61 % Mg(OH)2, to the fresh-water crustacean Daphnia magna was determined as described in a non GLP test. The test was carried out with 4 × 5 daphnias (quadruplicate test solutions) at each concentration, and the test solutions were not replaced. The exposure duration was 48 hours. The nominal concentrations tested were 96.88, 193.75, 387.5, 775, 1150, 3100 and 6200 mg/L.

At the start of the test the test substance appeared to be completely dissolved at all concentrations tested. The actual concentrations of the substance were not determined.

The results of the test were (as nominal concentrations):

48h EC50 (mortality): 284.76 mg/L

48h EC50 (mortality) recalculated for 100% of substance: 170.86 mg/L

The study is classified as supporting as no analytics and no detailed information on the solubility of the test material is available. The measured effects could be induced due to the hight pH.

Description of key information

In the key study on the short-term toxicity of magnesium chloride and magnesium sulphate to daphnia magna it was concluded that magnesium sulphate and magnesium chloride, and hence the magnesium ion, have a very low toxicity to daphnia.The 48 h LC50 of magnesium chloride was 1330 mg/L, for magnesium sulphate the LC50 was 1820 mg/L after 48h.

Additionaly tests with magnesium hydroxide were conducted, but without analytics and no detailed information on the solubility of the test material. The recalculated EC50 (48h) for Daphnia Magna was determined to be 170.86 mg/L with 100% magnesium hydroxide concentration. For the risk assessment the worst case is used, which is the recalculated EC50 (48h) of 170.86 mg/L for aquatic invertebrates from the supporting study Heinen 2005.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

170.6 mg/L

Additional information

The aquatic toxicity of magnesium chloride and magnesium sulphate was tested in a daphnia acute toxicity test for 48h. These biotests were performed with daphnia magna following the standard protocols developed by the Environmental Protection Agency (EPA. 1991). The daphnia were exposed to concentration of the test item of 10,000, 5,000, 2,500 and 1,250 mg/L in a moderately hard reconstituted water. The 48 h LC50 of magnesium chloride was 1330 mg/L, for magnesium sulphate the LC50 was 1820 mg/L after 48h.

Additionaly tests with magnesium hydroxide were conducted, but without analytics and no detailed information on the solubility of the test material: The recalculated EC50 (48h) for Daphnia Magna was determined to be 170.86 mg/L with 100% magnesium hydroxide concentration. For the risk assessment the worst case is used, which is the recalculated EC50 (48h) of 170.86 mg/L for aquatic invertebrates.