Lithium hydride

Long-term toxicity to aquatic invertebrates

Administrative data

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012-09-09 to 2012-09-30

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP and OECD guideline study on a read across substance (lithium)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2012

Report date:

2012

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Version / remarks:

updated 3rd October 2008

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.20 (Daphnia magna Reproduction Test)

Version / remarks:

May 30, 2008

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1300 (Daphnid Chronic Toxicity Test)

Version / remarks:

1996

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Lithium

EC Number:

231-102-5

EC Name:

Lithium

Cas Number:

7439-93-2

IUPAC Name:

lithium

Test material form:

other: solution

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

During the test, the concentrations of the test item were determined at regular intervals. Since the concentrations of the test item were expected to remain within ± 20 % of the nominal concentrations, analysis was performed in the highest and lowest test concentrations (plus control), when freshly prepared and at renewal (2 times per week sampling for analytics). These determinations were repeated at weekly intervals. During the first two weeks (day 0 – 9), concentrations of 0.50 and 5.70 mg/L (as highest and lowest) were measured. Due to the absence of living animals in the three highest test concentrations (2.53 – 5.70 mg/L), concentration of 1.70 mg/L was measured as the highest test concentration from the third occasion of analytical determination (day 14).

Test solutions

Vehicle:

yes

Details on test solutions:

The test solutions used in the test were prepared by mechanical dispersion without using any solubilising agent. The test solutions were freshly prepared at the beginning of the experiment, in the testing laboratory. Dilutions/solutions were performed with the test medium, Elendt M4 Medium.
Additionally, please see above in "Confidential details on test material".

Test organisms

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna (Straus)
- Source: Laboratory of Hydrobiology (Central Agricultural Office, Directorate of Plant-, and Soil Protection) 2100 Gödöllő, Kotlán S. u. 3. Hungary. The Daphnia are bred in the Laboratory of TOXI-COOP ZRT.
- Age of parental stock: less than 24 hours old and not the first brood progeny
- Feeding during test: The Daphnia were fed daily and the supplied diet was based on the amount of organic carbon (C) provided to each parent animal. This amount was 0.15 mg C/Daphnia/day.

ACCLIMATION
The stock animals were maintained in culture conditions (light, temperature, medium, feeding and animals per unit volume) to avoid the necessity of longer adaptation prior to the test. Brood daphnids were maintained in Elendt M4 Medium under test conditions for 10 days prior to the start of the test.

Study design

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Post exposure observation period:

No post exposure observation

Test conditions

Hardness:

> 140 mg/L (expressed in CaCO3), the lowest value was 189.9 mg/L (as CaCO3).

Test temperature:

19.8 - 22.0

pH:

The pH remained within the range 6 – 9 and varied not more than 1.5 units during the test.
The lowest value measured was 7.06 and the highest value was 8.45.

Dissolved oxygen:

> 3 mg/L, the lowest value was 6.27 mg/L

Nominal and measured concentrations:

The following nominal concentrations were tested: 0.50, 0.75, 1.13, 1.70, 2.53, 3.80 and 5.70 mg lithium/L.
The measured test item concentrations (lowest and highest test concentrations) remained within ± 20 % of the nominal concentration values during the test, therefore all biological results are based on the nominal concentrations.

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass beakers (150 mL volume) with 50 mL test medium
- Aeration: no aeration
- Renewal rate of test solution (frequency/flow rate): semi - static renewal, 3 times per week (When the medium was renewed a second series of test vessels was prepared and the parent animals transferred to them by a pipette of a suitable diameter. The volume of test medium transferred with the Daphnia was minimized)
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per vehicle control (replicates): 10

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: with test medium Elendt M4 Medium (according to OECD Guideline 211)

OTHER TEST CONDITIONS
- Adjustment of pH: the pH of the stock solution was adjusted to the pH of the Elendt M4 Medium using 1N HCl at each occasion of test solution preparation.
- Photoperiod: 16 h light : 8 h dark
- Light intensity: an average intensity of 1025 lux that corresponds to 13.9 µE m-2s-1

EFFECT PARAMETERS MEASURED (with observation intervals if applicable):
- Measurement of environmental parameters: the temperature, oxygen concentration and pH values were measured at each water renewal in fresh and old media in the control and in the highest test item concentration. Measurement of the hardness was performed at least once a week during the test in the control and in the highest test item concentration. Due to the absence of living animals in the three highest concentrations (2.53 - 5.70 mg/L), environmental conditions were measured at the concentration of 1.70 mg/L being the highest test concentration from the 7th renewal period (day 14

- Growth measurement and other parameters: The length of the parent animals (i.e. body length excluding the anal spine) was measured at the end of the test. Other parameters measured include: time to production of first brood (and subsequent broods), number and size of broods per animal, and the number of living offspring produced per animal per day from the first day offspring observed.

VEHICLE CONTROL PERFORMED: yes, the dilution water (Elendt M4 Medium) without the test item was used as control solution

Reference substance (positive control):

yes

Remarks:

For the evaluation of the quality of the Daphnia clone potassium dichromate was tested in a Daphnia magna acute toxicity test at least twice a year.

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

1.7 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Effect concentrations 2

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

2.53 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Effect concentrations 3

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

> 1.7 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Effect concentrations 4

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

2 mg/L

Nominal / measured:

nominal

Conc. based on:

other: calculated for lithium hydride

Basis for effect:

reproduction

Effect concentrations 5

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

2.9 mg/L

Nominal / measured:

nominal

Conc. based on:

other: calculated for lithium hydride

Basis for effect:

reproduction

Effect concentrations 6

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

> 2 mg/L

Nominal / measured:

nominal

Conc. based on:

other: calculated for lithium hydride

Basis for effect:

reproduction

Details on results:

Offspring:
The offspring produced by each parent animal were removed and counted daily from the appearance of the first brood. The first brood appeared in the treated concentrations and in the control in the period of 8th – 13th days of the test. The mean number of offspring produced per animal was 89.63 in the control group. The mean number of offspring produced per animal was slightly lower (85.60, 82.40, 72.60 and 79.20) in concentrations of 0.50, 0.75, 1.13 and 1.70 mg/L respectively. Based on the performed statistical analysis, the offspring production of these concentrations were not statistically significant from that of the control (Bonferroni t-Test, α=0.05*). In the three highest tested concentrations (2.53, 3.80 and 5.70 mg/L) all parent animals died by the 13th day of the test without producing any offspring. Therefore the results of these concentrations were excluded from the data analysis related to the reproductive output. Additionally the “living juveniles produced per animal per day from the first day offspring observed” values were calculated. These results showed similar trend to the evaluation of the total number of offspring.

*α = symbol for letter "alpha"

Growth measurement:
At the end of the test body length measurement was performed and the obtained data were statistically evaluated by analysis of variance (ANOVA) and Bonferroni t-Test ( = 0.05) using TOXSTAT software.
Statistically significant difference was not observed in the remained living parent daphnids (in the concentration range of 0.50 – 1.70 mg/L) compared to the control group.

Other parameters:
Aborted broods, presence of male neonates or ephippia were not noticed.

Mortality:
The mortality among the parent animals was recorded daily.
In the control group two parent animals (20 %) died during the test which was within the acceptability criteria.
In the concentration range of 0.50 – 1.70 mg/L mortality of parent animals was not observed during the experiment.

Reported statistics and error estimates:

For the estimation of the LOEC, and hence the NOEC, for effects of the test item on reproductive output, the mean value and standard deviation of the reproductive output across replicates of each concentration was calculated using analysis of variance (ANOVA).
Similar evaluation and statistical analysis was performed with the additional determined body length values.
The data were checked for homogeneity of variance and normality.
The mean for each concentration was compared with the control mean using an appropriate multiple comparison method (Bonferroni t-Test, α=0.05).
The obtained results did not allow the calculation of an exact 21-day EC50 value in the assay.

Any other information on results incl. tables

In the three highest tested concentrations (2.53, 3.80 and 5.70 mg/L) all parent animals died by the 13th day of the test without producing any offspring*. Therefore the results of these concentrations were excluded from the data analysis related to the reproductive output.

*Except in the case of one daphnia (the 7th replicate (10 daphnids / replicates in a dose group)) at a concentration of 2.53 mg/L, where eight juveniles were found on the day the parent animal was noticed dead (day 11). This result was excluded from the data analysis.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

In the 21-day semi-static chronic toxicity test to Daphnia magna with lithium, the 21-day No Observed Effect Concentration (NOEC) value and the Lowest Observed Effect Concentration (LOEC) value, related to reproduction were 1.70 mg/L and 2.53 mg/L respectively.
The 21-day EC50 value was determined to be higher than 1.70 mg/L.
Based on read across approach, the calculated NOEC for Lithium hydride was 2.0 mg/L, the LOEC was 2.9 mg/L and the EC50 was >2.0 mg/L.

Executive summary:

In the three highest tested concentrations (2.53, 3.80 and 5.70 mg/L) all parent animals died by the 13th day of the test without producing any offspring. Therefore the results of these concentrations were excluded from the data analysis related to the reproductive output. In the control group two parent animals (20 %) died during the test which was within the acceptable validity criteria. In the concentration range of 0.50 – 1.70 mg/L mortality of parent animals was not observed during the experiment. The reproduction was not reduced statistically significantly in the concentration range of 0.50 – 1.70 mg/L compared to the untreated control group. During the evaluation of the body length of parent animals at the end of the test, statistically significant difference was not observed in the remained living parent daphnids (in the concentration range of 0.50 – 1.70 mg/L) compared to the control group. Aborted broods, presence of male neonates or ephippia were not noticed during the test.
Accordingly, the 21-day NOEC value related to reproduction was determined to be 1.70 mg/L and the LOEC value as 2.53 mg/L. The obtained results were not sufficient for an exact EC50 value estimation. The 21-day EC50 was determined to be higher than 1.70 mg/L.

Based on read across approach, the calculated NOEC for Lithium hydride was 2.0 mg/L, the LOEC was 2.9 mg/L and the EC50 was >2.0 mg/L.