Magnesium chloride

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1972

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Not a guideline study but meets generally accepted scientific standards, well documented.

Qualifier:

no guideline followed

Principles of method if other than guideline:

A bioassay procedure was developed for Daphnia magna to serve as a representative aquatic invertebrate test species to evaluate the toxicity of selected inorganic pollutants (including MgCl2.6H2O).
The toxicities of various metals to Daphnia magna were evaluated on the basis of a 48-hr 50% lethal concentration (LC50).

GLP compliance:

not specified

Analytical monitoring:

yes

Details on sampling:

Chemical characteristics of Lake Superior water (Table 1) were monitored during the testing period according to procedures outlined by the American Health Association andprocedures employing atomic absorption spectroscopy.

Vehicle:

no

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna
- Age at study initiation (mean and range, SD): 12±12h old
- Strain/clone: clone originally obtained from the University of Michigan
- Source: University of Michigan
- Feeding during test : Yes
- Food type: the food suspension was prepared by adding 0.5 g of powered dried grass and 10 g of enriched trout-fry granules to 250 mL of Lake Superior water (test and culture medium) and mixing vigorously in a blender (5 min). The suspension was the strained through #20 bolting cloth. The food thus prepared was then stored in the refrigerator and mixed thoroughly each time a an aliquot was withdrawn.
- Amount: daphnids were fed with 1mL of suspension/Liter
- Frequency: Twice weekly for rearing and once weekly for testing.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

no data

Hardness:

Hardness: 45.3 mg/L (range 44-53 mg/L)

Test temperature:

18±1°C

pH:

7.74 (range 7.4-8.2) measurments of pH were made in the test containers when medium was added and 1 week later when the medium and toxicant were replaced by fresh solutions. at or below concentrations havins a chronic partial effet adddtions of Mg did not alter the pH by more than +/-0.3 of unit of the control water

Dissolved oxygen:

Dissolved oxygen concentrations in test containers were near saturation at all times. At damn, before the lights came on, the concentration was about 9 mg/L ; late in the day oxygen sometimes slightly exceeded saturation because of photosynthesis by algae.

Nominal and measured concentrations:

The numbers of concentration tested All ion concentrations measured in the stock solutions were compared to nominal values.
The numbers of concentration tested ranged from 5 to 12 depending on the toxicant and the initials effects observed. As daphnids response to toxicity was often within extremely narrow limited, a geometric series of concentrations was used for obtaining an approximation of toxicity; a linear series of concentrations was often used to delineating reproductive impairment levels. After concentrations to be tested were determined 3 to 7 tests were run for each toxicant. The results from all tests for each toxicant concentrations were pooled for statistical analysis.

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL beaker
- Type (delete if not applicable): The beaker were covered with a pane of glass to minimize evaporation
- Material, size, headspace, fill volume: 250 mL beaker filled with 200mL of test solution
- Renewal rate of test solution (frequency/flow rate): weekly renewal
- No. of organisms per vessel: 5 daphnids in 200 ml
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- Biomass loading rate: no data

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Source : Lake Superior water
- Total organic carbon: no data
- Particulate matter: no data
- Metals: cf. Table 1
- Pesticides: no data
- Chlorine: 1.217
- Alkalinity: 42.3 mg/L
- Ca/mg ratio: Ca/Mg ratio = 4.4 in the lake Superior water (test medium)
- Conductivity: no data
- Salinity: no data
- Culture medium different from test medium: No
- Intervals of water quality measurement: weekly measured

OTHER TEST CONDITIONS
- Adjustment of pH: pH was not adjusted
- Photoperiod: 16h photoperiod (automatically controlled)
- Light intensity: 115 ft-c

VEHICLE CONTROL PERFORMED: no

RANGE-FINDING STUDY
- Test concentrations: 5 concentrations tested ranging between 3.6 and 256 mg of Mg/L (or between 14.1 and 1002.7 mg of MgCl2/L).
- Results used to determine the conditions for the definitive study: Since daphnids had not been previously exposed to Mg on a chronic basis, experiments have repeated before appropriate concentrations could be tested. As daphnid response to toxicity was within extremely narrow limits, a linear serie of concentrations was used for delineating reproductive impairment levels.

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

140 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element

Remarks:

Mg

Basis for effect:

mortality

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

548.4 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

- Behavioural abnormalities: No behavioural abnomailities were observed
- Observations on body length and weight: body length and weight were not recorded
- Mortality of control: No mortality observed in the control

Reported statistics and error estimates:

Results were stastistically evaluated with the method of Lichtefield and Wilcoxon (1949) for establishing approximations of the 95% confidence limits for survival effects. Reproductive effects were analysed in a similar manner exluding confidence limits, but are given in terms of impairment by percentage.

Validity criteria fulfilled:

yes

Remarks:

The test was considered as valid when fewer than 10% of the animals in the control solutions were unable to swim, when the pH value was not below 7.0 and the measured oxygen concentration was always near-saturation.

Conclusions:

The 48h LC50 for Magnesium Chloride to Daphnia magna is = 140 mg of Mg/L (i.e 548.4 mg of MgCl2/L).

Executive summary:

Five daphnids (Daphnia magna) were placed in each test and control vessel, i.e. 20 animal per concentration test (4 replicates). After 48h the number of animals in the control and test solutions that could swim was counted.

The test was considered as valid when fewer than 10% of the animals in the control solutions were unable to swim, when the pH value was not below 7.0 and the measured oxygen concentration was always near-saturation.

The 48h LC50 calculated arithmetically from the concentration/effect ratio. Thus calculated 48h LC50 value for Daphnia magna was 140 mg Mg/L (i.e 548.4 mg of MgCl2/L).

Description of key information

Three reliable studies are available for the acute toxicity of Magnesium Chloride to freshwater and seawater invertebrates:

For the freshwater, the lowest 48h EC50 value for Daphnia magna was 548.4 mg of MgCL2 /L (i.e 140 mg Mg/L), Biesinger et al. (1972)

For the seawater, the lowest 48h LC50 obtained for Americamysis bahia was 3259 mg of MgCl2/L (i.e 832 mg Mg/L), (Pillard et al. (2000))

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

548.4 mg/L

Marine water invertebrates

Marine water invertebrates

Effect concentration:

3 259 mg/L

Additional information

Relevant information is available on the acute toxicity of magnesium compounds to invertebrates. In total, 3 studies were judged reliable with restriction (Klimisch 2). The effect of MgCl2 was investigated to a range of aquatic invertebrates, including Daphnia magna, in both freshwater and marine water.

-         Biesinger et al. (1972) investigated the acute toxicity of Magnesium Chloride to freshwater Daphnia magna. Five daphnids (Daphnia magna) were placed in each test and control vessel, i.e. 20 animal per concentration test. 5 concentrations tested ranging between 3.6 and 256 mg of Mg/L (or between 14.1 and 1002.7 mg of MgCl2/L). The 48h LC50 value for Daphnia magna was 140 mg Mg/L (i.e 548.4 mg of MgCl2/L). This study was not a guideline study but meets generally accepted scientific standards, well documented. As this study reports the lowest 48h EC50 value for the daphnia magna, it is selected as a key study.

-         Mount et al. (1997) investigated the acute toxicity of Magnesium Chloride to freshwater Daphnia magna and Ceriodaphnia dubia. The invertebrates were exposed to one single concentration of the test item in a moderately hard reconstituted water during 48h. The 48h LC50 values to Daphnia magna and Ceriodaphnia dubia were 339 mg of Mg/L and 225 mg of Mg/L, respectively (i.e 1328 and 881.4 mg of MgCl2/L respectively).

This study was performed following the standard protocols developed by the Environmental Protection Agency (EPA, 1991), and thus were judged as reliable with restrictions (No guideline study, but well documented and scientifically acceptable)

 

 - Pillard et al. (2000) investigated the acute toxicity of Magnesium Chloride to saltwater mysid shrimp (Americamysis bahia). The study was conducted at salinities of 10, 20 and 31‰. The lowest 48h LC50 observed value was obtained for Americamysis bahia exposed in lab saltwater with a salinity of 10 ‰ : 48h LC50 = 832 mg of Mg/L (i.e 3259 mg of MgCl2/L). This study was performed following the standard protocols developed by the Environmental Protection Agency (EPA, 1991), and thus were judged as reliable with restrictions (water characteristics measured but not reported).

=> All reliable L(E)C50 values were higher than 100 mg Mg/L, with the lowest 48h EC50 value for Daphnia magna 140 mg Mg/L (i.e 548.4 mg of MgCL2 /L) for freshwater, and 832 mg Mg/L (i.e 3259 mg of MgCl2/L) for marine invertebrates (Americamysis bahia).