Lithium

Long-term toxicity to fish

Description of key information

Long-term toxicity test in fish with lithium is not available. Consequently, read-across was applied using study results obtained from lithium hydroxide monohydrate. In a long-term toxicity test in Zebrafish (Danio rerio) a LOEC value of 24.35 mg/L and a NOEC value of 17.35 mg/L were determined for lithium hydroxide monohydrate. Based on read-across approach, the calculated LOEC and NOEC values for lithium metal were 4.03 and 2.87 mg/L respectively.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

2.87 mg/L

Additional information

Long-term toxicity test in aquatic to fish with lithium is not available. Consequently, read-across was applied using study results obtained from lithium hydroxide monohydrate.

The purpose of this study was to evaluate the chronic toxicity of the test item lithium hydroxide monohydrate to early life stages (embryo, larvae and juveniles) of fish.

For this purpose, eggs were exposed in a semi static test to aqueous test media containing the test item for 34 days at a range of concentrations under defined conditions. Lethal and sub-lethal effects were assessed and compared with control values to determine the lowest observed effect concentration (LOEC) and hence the no observed effect concentration (NOEC) for each response assessed.

The test was considered to be valid as assay acceptance criteria were fulfilled.

Based on the preliminary chronic fish toxicity test result the following nominal test concentrations were selected for the early life stage toxicity test: 1.8 mg/L, 3.0 mg/L, 7.2 mg/L, 15.0 mg/L and 21.1 mg/L.

Test item concentrations were analyzed in the test solutions by flame photometry. Lithium hydroxide monohydrate concentration in the test solutions was determined at 5 renewal periods by flame photometry. The measured concentrations of the lithium hydroxide monohydrate varied between 102 % and 151 % of the nominal concentration during the test. Mean measured concentrations were calculated for each parallel test chambers and for each treatment concentrations. The measured concentrations of each parallel treatment were within the range of ± 20 % of the mean measured values meeting the validity criteria. Since concentrations of the test substance were satisfactorily maintained within ± 20 % of the mean measured values during the test in all treatment groups, all biological results are reported on the basis of the mean measured concentrations: 2.43 mg/L, 3.82 mg/L, 8.60 mg/L, 17.35 mg/L and 24.35 mg/L.

Seventy nine to eighty two eggs were tested per test concentrations and the control in two parallels in the test groups and in the control group (approximately 40-40 eggs per each parallel treatments). Based on microscopic observation embryos were at approximately 64 to 128 cell stages at start of treatment.

Environmental parameters (water temperature, pH, LDO) were monitored during the test. There were no deviations from the defined ranges.

Animals were fed from elimination of the yolk sac (free-feeding stage) to the end of the test with appropriate type and amount of food ad libitum, and thus starvation did not have any effect on the results obtained.

Cumulative mortality (observed from Day 0 to the end of the test on Day 34), mortality observed at embryonic/eleutheroembryonic (i.e. early larval) stage (from Day 0 to the end of hatching on Day 5) and mortality observed at larval/juvenile stage (from Day 6 - free feeding stage - to the end of the test on Day 34) were statistically evaluated. Statistically significant (p < 0.01) cumulative mortality compared to the control was observed at treatment concentration of 24.35 mg/L (21.1 mg/L nominal). No significant lethal effect was observed until embryonic/eleutheroembryonic stage. Since mortality observed from Day 6 to Day 34 was statistically significant (p < 0.01) it is considered that the test item influenced the survival of the test organism at larval/juvenile stage rather than at embryonic stage. No statistically significant lethal effect was observed in other test concentrations (neither during embryonic nor larval/juvenile stage).

No significant effect on hatching of the larvae was observed at any concentrations tested. No significant differences were observed either in starting or duration of hatching. Numbers of larvae hatched daily were statistically evaluated on Day 4 and Day 5 and no significant differences were observed.

At the end of the test, group body weights were measured. No significant differences were observed.

Body length was measured for each animal individually and the data were statistically evaluated. Statistically significant (p < 0.05), but biologically not relevant difference was observed at test concentration of 8.61 mg/L (7.2 mg/L nominal).

Other sub-lethal effects were monitored with limited extent: numbers of embryos/larvae/juveniles with deformities or abnormal behavior were recorded. No obvious test item related changes in the behavior of fish could be observed.

Under the conditions of this early life stage toxicity study, the test item lithium hydroxide monohydrate had significant lethal effect on early life stages of Zebrafish (Danio rerio). The observed effect was associated with larval/juvenile stages, but no significant effect was observed during the embryonic stage.

The following endpoints (34 days LOEC and NOEC) were calculated in the study:

The 34 d LOEC 24.35 mg test item/L

The 34 d NOEC 17.35 mg test item/L

Based on a read-across approach, the calculated LOEC and NOEC values for lithium metal were 4.03 and 2.87 mg/L respectively.