Magnesium chloride

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

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.

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 effect of MgCl2 on the reproduction of Daphnia magna of selected inorganic substances (including MgCl2.6H2O) .

GLP compliance:

no

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

Details on test solutions:

No data

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 The food thus prepared was then stored in the refrigerator and mixed thoroughly each time a an aliquot was withdrawn.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:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

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.

Salinity:

no data

Nominal and measured concentrations:

Analytical measurments in test containers were made for Na, Ca, Mg, Fe, Mn, Zn and Cd at the time of addition and 1 week later.
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 solutio
- 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

Duration:

21 d

Dose descriptor:

other: EC16

Effect conc.:

82 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

other: EC16

Effect conc.:

321 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

reproduction

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
The study reports a 21 days EC16 of 82 mg Mg/L for the effect of MgCl2 on the reproduction of Daphnia magna (i.e 321 mg of MgCl2 /L).

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:

not specified

Conclusions:

The study reports a 21 days EC16 of 82 mg Mg/L for the effect of MgCl2 on the reproduction of Daphnia magna (i.e. 321 mg of MgCl2 /L).

Executive summary:

The objective of this test was assess the effect of Magnesium Chloride on reproduction of Daphnia magna. For this, five young female Daphnia per replicate (4 replicate per concentration), aged less than 24 hours at the start of the test (12 +/-12h old), were exposed (in test and control vessel - 200mL) to the test substance added to water at a range of concentrations. The test duration was 21 days. At the end of the test, the total number of living offspring produced per parent animal alive at the end of the test were assessed.

The 21 days EC16 (16% reproductive-impairment concentration) was arithmetically calculated from the concentration/effect ratio. The 16% reproductive-impairment concentration was given since it represented a minimal reproductive value below which the variability in the reproduction could not be detected from controls. Background concentration of the test medium was approximately 3 mg Mg/L, which corresponds to a soft water medium.

 

Thus calculated 21 days EC16 value for Daphnia magna was 82 mg of Mg/L (i.e 321 mg of MgCl2/L).

As a conservative approach, the No Observed Effect Concentration (NOEC) was derived by dividing the EC16 value by a factor of two, resulting in a NOEC of 41 mg Mg/L (i.e 160.5 mg of MgCl2/L).

Description of key information

One reliable (Klimisch 2) chronic toxicity tests with MgCL2 was identified.

In this study, 5 daphnids (Daphnia magna) were placed in each test and control vessel, i.e. 20 animal per concentration test (4 replicates per concentration). At the end of the test, the total number of living offspring produced per parent animal alive at the end of the test were assessed. The 21 days EC16 value for Daphnia magna was 82 mg of Mg/L (i.e 321 mg of MgCl2/L).

As a conservative approach, the No Observed Effect Concentration (NOEC) was derived by dividing the EC16 value by a factor of two, resulting in a NOEC of 41 mg Mg/L (i.e 160.5 mg of MgCl2/L).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

NOEC

Effect concentration:

160 mg/L

Additional information

One study is judged reliable (Klimisch 2) (Biesinger and Christensen, 1972). This study is not a guideline study but meets generally accepted scientific standards, well documented and it is selected as a key study.

The NOEC value determined for Magnesium Chloride is higher than 100 mg MgCl2/L for freshwater invertebrates, indicating that Magnesium Chloride has a very low long-term toxicity to aquatic invertebrates.