Magnesium chloride

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

study generated according to valid and internationally accepted testing guidelines and performed according to GLP

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

certified laboratory

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material :
Not appropriate

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Prior to the main test, a range-finding test was performed with concentrations of 0, 0.01, 0.1, 1 10, 100 mg/L
- Sample storage conditions before analysis: After sampling, the samples were mixed with 1 mL 65 % nitric acid and stored at room temperature until analysis. At the analytical laboratory, the samples were filtered through a Chromafil RC-45/25 filter. If necessary, the samples were further diluted with 1 % nitric acid prior to analysis by ICP-MS.

Vehicle:

no

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: Scenedesmus subspicatus
- Strain: strain no. SAG 86.81
- Source (laboratory, culture collection): algae used were purchased from the Albrecht-von-Haller-Institut für Pflanzenwissenschaften, experimentelle Phykologie und Sammlung von Algenkulturen, (SAG), Universität Göttingen, Nikolausberger Weg 18, 37073 Göttingen, Germany.
- Method of cultivation: The algae are grown semi-continuously in the laboratory in aerated liquid cultures under permanent illumination. Old medium is periodically replaced by fresh mineral solution in order to keep the algae in an exponential growth state. Stock cultures are also kept on slanted agar tubes and are ordered regularly from the culture collection. Culture conditions were as follows:
(i) Illumination: from the top, OSRAM light tubes (L 30 W/32-930, Lumilux, L 30 W/72-965, Biolux) approx. 5000 lux
(ii) Temperature: 21 - 25° C
(iii) Culture flasks: 1000 mL screw cap bottles
(iv) CO2 supply by aeration. The air is filtered through ORBOTM - 402Tenax® Tubes (Supelco)
Cells from this semi-continuous liquid stock culture were used for test.


ACCLIMATION
- Culturing media and conditions (same as test or not):
NH4Cl 30 mg/L
MgCl2.6 H2O 24 mg/L
CaCl2.2 H2O 36 mg/L
MgSO4.7 H2O 30 mg/L
KH2PO4 3.2 mg/L
FeCl3.6 H2O 0.128 mg/L
Na2EDTA. 2H2O 0.2 mg/L
H3BO3 0.37 mg/L
MnCl2.4 H2O 0.830 mg/L
ZnCl2 6 µg/L
CoCl2. 6H2O 3 µg/L
CuCl2.2H2O 0.02 µg/L
Na2MoO4. 2H2O 14 µg/L
NaHCO3 100 mg/L

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 d

Post exposure observation period:

Not appropriate

Hardness:

Not reported

Test temperature:

Temperature values recorded during the test are shown in the folowing Table.

Temperature [°C]
Time [h] min max.
0 22 23
24 23 23
48 23 26
72 23 26

pH:

pH values measured during the test are shown in the folowing Table

MgCl2.6 H2O [mg/L] t = 0 h* t = 72 h
0 7.31 8.01
100 7.33 8.31
* measured after 1 h of aeration in one representative sample

Dissolved oxygen:

In all tests, dissolved oxygen ranged from 7.2 to 7.6 ± 0.1 (SE) mg/L.

Salinity:

Not reported

Nominal and measured concentrations:

The test was performed under static conditions. The concentration of the active ingredient Magnesium Chloride was checked in test medium by analysing samples collected during the test period. Samples were collected after initiation of the test and at the end of the test (after 3 days). As the main test was performed in limit test design, only 0 and 100 mg/L were measured. The lead compound was Mg, which was present in the original test medium as blank value, added as MgCl2.6 H2O (24 mg/L) and MgSO4. 7 H2O (30 mg/L).

- Test item nominal [mg/L] : 0 => Nominal concentration = 5.83 mg/L // Analysed concentrations = 6.41, 6.22, 6.17, 6.2 mg/L
- Test item nominal [mg/L] : 100 => Nominal concentration = 17.79 mg/L // Analysed concentrations = 16.86, 17.1, 21.46 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 500 mL Erlenmeyer flasks with aluminium caps and two baffles.
- Aeration: CO2 supply by aeration. The air is filtered through ORBOTM - 402Tenax® Tubes (Supelco)
- Renewal rate of test solution (frequency/flow rate):
- Initial cells density: 5000 cells/mL
- No. of vessels per concentration (replicates): 6 replicates
- No. of vessels per control (replicates): 6 replicates

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
The composition of the test medium was as follows:
NH4Cl 30 mg/L
MgCl2 . 6 H2O 24 mg/L
CaCl2 . 2 H2O 36 mg/L
MgSO4. 7 H2O 30 mg/L
KH2PO4 3.2 mg/L
FeCl3. 6 H2O 0.128 mg/L
Na2EDTA. 2H2O 0.2 mg/L
H3BO3 0.37 mg/L
MnCl2. 4 H2O 0.830 mg/L
ZnCl2 6 µg/L
CoCl2 .6H2O 3 µg/L
CuCl2.2H2O 0.02 µg/L
Na2MoO4.2H2O 14 µg/L
NaHCO3 100 mg/L

- Culture medium different from test medium: no
- Intervals of water quality measurement: t=0, t=1 day, t=2 days, t=3 days

OTHER TEST CONDITIONS
- Sterile test conditions: no
- Adjustment of pH: No

Reference substance (positive control):

no

Duration:

3 d

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: EC values (EC50, NOEC and LOEC) could not be determined due to no toxic effects of the test item.

Duration:

3 d

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: EC values (EC50, NOEC and LOEC) could not be determined due to no toxic effects of the test item.

Details on results:

EC values (EC50, NOEC and LOEC) could not be determined due to no toxic effects of the test item.
All validity criteria of OECD Guideline for Testing of Chemicals No. 201 were fulfilled:
- Cell numbers, measured in the controls between 0 d and 3 d, were found to increase by a factor of 116.72 which exceeds the threshold of 16, this corresponds to a growth rate of 1.59/d.
- The coefficient of variation of average growth in replicate control cultures was 1.3 % and did not exceed 7 % for the whole test period.
- The mean coefficient of variation for the section-by-section specific growth rates (days 0 - 1, 1 - 2 and 2 - 3) in the control cultures was 17 % and did not exceed 35 %.

Reported statistics and error estimates:

- The coefficient of variation of average growth in replicate control cultures was 1.3 % and did not exceed 7 % for the whole test period.
- The mean coefficient of variation for the section-by-section specific growth rates (days 0 - 1, 1 - 2 and 2 - 3) in the control cultures was 17 % and did not exceed 35 %.

Validity criteria fulfilled:

yes

Remarks:

All validity criteria of OECD Guideline for Testing of Chemicals No. 201 were fulfilled

Conclusions:

No toxic effects of the test item :
- The 72h EC50 of Magnesium Chloride to algae is >100 mg MgCl2/L.
- No observed effect concentration (NOEC) = 100 mg MgCl2/L.

Executive summary:

The algae were exposed to one single concentration of the test item under defined conditions in a synthetic growth medium during several generations. Cell division under test conditions was compared with and without the influence of test item.

After 24, 48, and 72 hours of growth, the cell numbers were determined by fluorescence detection, and the growth was recorded.

The mean value of the cell concentration was plotted versus time to produce growth curves for each concentration.

The main test was performed in a limit test design. The limit test was performed with 100 mg MgCl2 6H2O/L. and control without test item. Both study groups were prepared in six replicates. The average cell numbers and the resulting growth rates of the controls and the 100 mg MgCl2 6H2O/L. test solutions were determined. The results were checked by Dunnett’s t test (SAS). No significant differences from controls were found. Hence, due to no toxic effects of the test item, the EC values (EC50 and LOEC) could not be determined.

Description of key information

A GLP guideline study was performed to assess the acute toxicity of Magnesium Chloride hexahydrate(DENG, 2010) to the Single Cell Green Alga Desmodesmus subspicatus in a limit test (0 -100 mg of MgCl2 6H2O/L), according to the OECD guideline 201.

The 72h EC50 was found to be >100 mg MgCl2 6H2O/L. No mortalities or adverse effects were noted at this concentration: NOEC = 100 mg of MgCl2 6H2O/L.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

100 mg/L

Additional information

The toxicity of the MgCl2 to freshwater green algae Desmodesmus subspicatus was investigated in one GLP-compliant study performed in accordance with standard methods, without deviation. The study is considered as reliable (Klimisch 1) and is selected as a key study for the endpoint.

Two further supporting studies, reported in the IUCLID Dataset (2000) present two EC50s to Scenedesmus subspicatus of 562 and 1195 mg Mg/L

A further literature study (den Dooren de Jonget al., 1965) which assessed the toxicity of Magnesium Chloride to the algal species Chlorella vulgaris reports a NOEC of 980 mg Mg/L (or 3838 mg of MgCl2/L).