Magnesium hydroxide

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to fish

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:

96 h

Dose descriptor:

LC50

Effect conc.:

2 120 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Remarks on result:

other: Magnesium chloride

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

2 820 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

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 Pimephales promelas (LC50>100 mg/L).

Executive summary:

The aquatic toxicity of magnesium chloride and magnesium sulphate was tested in a fish acute toxicity test. The exposure duration was 96 h, test animals were Pimephales promelas. These biotests were performed following the standard protocols developed by the Environmental Protection Agency (EPA. 1991). The fishes 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, 48, 96 hours of exposure the mortality of the exposed fishes was recorded. The 96 h LC50 of magnesium chloride to Pimephales promelas was 2120 mg/L, for magnesium sulphate the LC50 was 2820 mg/L after 96h.

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

The study was used are read across for magnesium hydroxide, the recalculated 96h LC50 based on MW would be 1298 mg/L (from magnesium chloride) and 1366 mg/L (from magnesium sulphate).

Reference 2

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2005-08-09 to 2005-08-16

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Remarks:

Not GLP. Test material is diluted to 61% magnesium hydroxide in aqueous solution so results were recalculated to 100%. Analytical measurements missing.

Principles of method if other than guideline:

Protocol for Acute Lethality - Test using Rainbow Trout EPS 1/RM/9, Environment Canada, 1990 (with 1996 amendments).

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:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
Test solutions were prepared by adding appropriated amounts of the test substance on a weight to volume basis (mg/L) directly to test chambers containing dilution water. Each solution was mixed thoroughly prior to test initiation.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: rainbow trout
- Source: Rainbow Springs Hatchery, RR #2 Thamesford, ON Canada NOM 2 MO
- Mean fish weight (± 2 SD): 0.45 (± 0.31) g
- Mean fish fork length (± 2 SD): 38.2 (± 7.4) mm

ACCLIMATION
no data

FEEDING DURING TEST
no data

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Test temperature:

15 °C

pH:

8.4 - 10

Dissolved oxygen:

8.8 - 9.3 mg/L

Nominal and measured concentrations:

Nominal concentration: 0, 295, 527, 941, 1680, 3000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: cylindrical pails fitted with a food-grade plastic liner
- Material, depth of test solution, fill volume: polyethylene, 24 cm, 22.5 L
- Aeration: yes, 6.5 mL/min/L
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- Biomass loading rate: 0.30 g/L

TEST MEDIUM / WATER PARAMETERS
- Source of dilution water: Well water with no chemicals or substances added

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16h / 8h
- Light intensity: 100- 500 lux (full spectrum fluorescent)

EFFECT PARAMETERS MEASURED

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Range finding study: no data

Reference substance (positive control):

yes

Remarks:

Potassium chloride

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

527 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

1 293 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Remarks on result:

other: Based on 61% test item

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

775.8 mg/L

Remarks on result:

other: recalculated to 100% test item

Details on results:

- Other abnormalities: no
- Observations on body length and weight: no
- Other biological observations: no
- Mortality of control: no
- Other adverse effects control: no
- Abnormal responses: no
- Any observations that might cause a difference between measured and nominal values: no

The 96 -hour LC50 for Onchorinchus mykiss (rainbow trout) was recalculated to bring the concentration of Magnesium hydroxide up to 100% as the concentration of Magnesium hydroxide was only 60% when determining the original LC50 for Onchorinchus mykiss. The recalculated LC50 (96h) for Onchorinchus mykiss was determined to be 775.8mg/L.

Results with reference substance (positive control):

The reference substance potassium chloride had a calculated LC50 value of 3567 mg/L (date: 2005-08-19) which is in range of the warning limits (3034 - 4601 mg/L).

Sublethal observations / clinical signs:

Table 1. Mortality rate Onchorinchus mykiss at different test concentrations

Test concentration (mg/L)	Mortality (%)
3000	100
1680	90
941	20
527	0
295	0
Control	0

 

 

Validity criteria fulfilled:

yes

Conclusions:

The 96 -hour LC50 for Onchorinchus mykiss (rainbow trout) was recalculated to be 775.8 mg/L.

Executive summary:

In a 96-h acute toxicity study, Onchorinchus mykiss were exposed to magnesium dihydroxide at nominal concentrations of 0, 295, 527, 941, 1680, 3000 mg/L under static conditions. The recalculated 96-h LC₅₀ was 775.8 mg/L. Sublethal effects were not observed in the groups exposed to magnesium dihydroxide. Based on the results of this study, the test substance would be not classified.

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.

Reference 3

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2005-09-13 till 2005-09-17

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 results were recalculated to 100%. Analytical measurements missing.

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. Tests were conducted in accordance with 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):

Pimephales promelas

Details on test organisms:

TEST ORGANISM
- Common name: Fathead minnow
- Source: Marinco Bioassay Laboratory (Sarasota, Florida)
- Age at study initiation: at least 13 days old

ACCLIMATION
- Acclimation period: no data
- Acclimation conditions: same as test conditions
- Type and amount of food during acclimation: brine shrimp (Artemia sp.)
- Feeding frequency during acclimation: prior to test initiation
- Health during acclimation: no mortality observed

FEEDING DURING TEST
- Food type: brine shrimp (Artemia sp.)
- Amount: no data
- Frequency: priot to test solution renewal on day 2

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Test temperature:

19.8 - 21.7 °C

pH:

7.9 - 10.5

Nominal and measured concentrations:

Nominal concentrations: 0, 24.22, 48.44, 96.88, 193.75, 387.5, 775 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: glass beakers (8cm x 8cm x 12 cm)
- Test system: open
- Material, size, fill volume: glass, 600 mL, 200 mL
- Aeration: no data
- Renewal rate of test solution: after 48 h
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2
- Biomass loading rate: no data

TEST MEDIUM / WATER PARAMETERS
- Preparation of dilution water: moderately hard water, aerated

OTHER TEST CONDITIONS
- Adjustment of pH: no data
- Photoperiod: 16 hours light and 8 hours darkness
- Light intensity: flourescent lighting

EFFECT PARAMETERS MEASURED
Water quality was monitored daily, and both before and after renewal. 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.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Range finding study : no data available

Reference substance (positive control):

yes

Remarks:

sodium chloride

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

511.31 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Remarks on result:

other: 60% test substance

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

306.79 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Remarks on result:

other: recalculated to 100% test substance

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

22.44 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Remarks on result:

other: 60 % test substance

Details on results:

- Other abnormalities: no
- Observations on body length and weight: no
- Other biological observations: no
- Mortality of control: no
- Other adverse effects 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

The LC50 (96h) of P. Promelas was recalculated to bring the concentration of Magnesium hydroxide up to 100% as the concentration of Magnesium hydroxide was only 60% when determining the original LC50. The concentration was recalculated giving an LC50 of 306.79 mg/L for freshwater fish.

Results with reference substance (positive control):

The 48-hour LC50 value for the reference toxicant test conducted was 6.80 g NaCl/L (95% Cl: 6.29 - 7.36 g NaCl/L). Survival in the control exposure was 100 %. The result was within the current control limits at MACTEC and demonstrated the organisms were within their expected sensitivity range.

Sublethal observations / clinical signs:

Table 1. Percent survival of P. promelas at the conclusion of acute toxicity tests

Control or chemical exposure	Concentration of test substance (mg/L)	Survival (%) after 96 hours	mg/L LC50
Control	0	100	511.31
Test substance	24.22	100
Test substance	48.44	95
Test substance	96.88	95
Test substance	193.75	85
Test substance	387.5	60
Test substance	775	35

Validity criteria fulfilled:

yes

Conclusions:

In a 96-h acute toxicity study, Pimephales promelas were exposed to magnesium dihydroxide. The 96-h LC50 was 306.79 mg/L.

Executive summary:

In a 96-h acute toxicity study, Pimephales promelas were exposed to magnesium dihydroxide at nominal concentrations of 0, 24.22, 48.44, 96.88, 193.75, 387.5, 775 mg/L under semi-static conditions. The recalculated 96-h LC₅₀ was 306.79 mg/L. Sublethal effects were not observed in the groups exposed to magnesium dihydroxide. Based on the results of this study, the test substance would be not classified.

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 Pimephales promelas it was concluded that magnesium sulphate and magnesium chloride, and hence the magnesium ion, have a very low toxicity to Pimephales promelas. The 96 h LC50 of magnesium chloride to Pimephales promelas was 2120 mg/L, for magnesium sulphate the LC50 was 2820 mg/L after 96h.

Additionaly tests with magnesium hydroxide were conducted, but without analytics and no detailed information on the solubility of the test material. The measured effects could be induced due to the hight pH. In both studies the LC50 was determined to be above 100 mg/L.

For the risk assessment the worst case is used, which is the recalculated LC50 (96h) of P.Promelas at 306.79 mg/L for freshwater fish from the supporting study Heinen 2005.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

LC50

Effect concentration:

306.79 mg/L