Dilanthanum tricarbonate

Endpoint summary

Additional information

No data were available for the terrestrial toxicity to Lanthanum carbonate. Therefore, information from different analogue substances Lanthanum chloride, anhydrous, Lanthanum nitrate and mixtures of rare earth chlorides (RE chlorides) were taken into account for the toxicological assessment of this endpoint. A summary of the information about the analogue source substances is given in the data matrix of the justification for the analogue source substances approach, which can be found either in the CSR or as an attachment in IUCLID section 13.

 

1. Toxicity to soil macroorganisms except arthropods:

No information is available for the toxicity to terrestrial soil macroorganisms except arthropods with Lanthanum carbonate, but data are available for this endpoint with a mixture of rare earth elements (REE).

No mortality of earthworms (Eisenia fetida) was observed in nine natural chinese soils within 6 weeks (Wen et al. 2006). The total content of Lanthanum, Yttrium, Cerium, Praseodymium and Neodymium in these soils was 18.61 - 162.28 mg REE/kg dw, the concentration of Lanthanum was in a range of 4.6 - 71.9 mg La/kg dw. So generally, a LC0 > 71.9 mg La/kg could be stated. Furthermore, the more than two fold higher value of the total content of rare earth elements compared to the content of La, for which also no mortality of the earthworms was stated showed, that the LC0 for Lanthanum is clearly underestimated.

 

2. Toxicity to soil macroorganisms

No information is available on the toxicity to terrestrial arthropods with Lanthanum carbonate, but data are available for this endpoint with a mixture of rare earth chloride hexahydrates (Li et al. 2006). The mixture was composed mainly of Cerium, Lanthanum and Praseodymium, the fractions of individual rare earth elements were not given.

The short-term toxicity of a mixture of rare earth chloride hexahydrate on Holotrichia parallela (Coleoptera, larvae in the third stage) was tested in a filter paper contact test, yielding a LC50 > 3000 mg/L.

In a prolonged soil test groups of larvae (Holotrichia parallela) at the third larval stage were kept in the soil, spiked with mixed rare earth chloride hexahydrate. The exposure lasted until adult eclosion. Mortality, pupation and emergence were assessed after the exposure and revealed a NOEC value of > 3000 mg/kg soil.

Although the test substance was a mixed rare earth chloride hexahydrate with Cerium, Lanthanum and Praseodymium as rare earth elements, and therefore a calculation of a NOEC value in mg La/kg dw is not possible, the overall high concentration without effects on mortality, emergence or pupation could be used for the assessment of the effect of Lanthanum carbonate on terrestrial arthropods as a worst case scenario.

 

3. Toxicity to terrestrial plants:

No information is available for the toxicity to terrestrial plants with Lanthanum carbonate, but one study was available with a plant soil system, using Lanthanum nitrate as test substance.

Seedlings of Zea mays were grown in a red loamy soil, spiked with up to 2.5 g La/kg (Hu et al. 2006). Primary root elongation and dry weight of roots and shoots were measured after 14 d of application. The NOEC and LOEC for primary root elongation and root dry weight were 250 and 500 mg La/kg dw, respectively.

Since Lanthanum nitrate has a high water solubility (957 g/L at 25 °C) compared to the water solubility of Lanthanum carbonate (1.24 mg/L at 20°C), the test conditions has to be evaluated as a worst case scenario. It is to be expected, that the same study perfomed with Lanthanum carbonate will show no effects in this concentration range, since the Lanthanum ion of this test item is considerable lower bioavailable for plants.

 

4. Toxicity to microorganisms:

No data are available for the toxicity to soil microorganisms with Lanthanum carbonate. Therefore data from the analogue source substance Lanthanum chloride hexahydrate were applied to cover the respective endpoint.

The long term effect of Lanthanum chloride hexahydrate on carbon transformation activity of soil microorganisms was investigated according to OECD 217 under GLP-conditions (Schulz 2010). Glucose-induced respiration rates were measured after 0, 7, 14 and 28 days incubation for 12 consecutive hours. The test item caused a maximum inhibition of 19.6% at 1514.2 mg LaCl3*6H2O/kg soil dw (highest concentration tested) 28 days after application. Only for this concentration a significant difference compared to the control was stated. The EC50 could not be calculated, but it can be concluded that the EC50 is higher than 1514.2 mg test item/kg soil dry weight (according to 595 mg La/kg soil dw), the highest concentration tested. The NOEC of the test item was calculated to be 757.10 mg LaCl3*6H2O/kg soil dry weight (according to 297.7 mg La/kg soil dw) after 28 days of exposure.

Furthermore, the long term effect of Lanthanum chloride hexahydrate on nitrogen transformation activity of soil microorganisms was tested according to OECD 216 under GLP-conditions (Lemnitzer 2010). After 0, 7, 14 and 28 days of incubation of soil, which was amended with powdered plant meal at the beginning of the test, samples of treated and control soils are extracted and quantities of nitrate in the extracts is determined. After 28 days the treatment with 1441 mg LaCl3*6H20 /kg soil dry weight (according to 566.5 mg La/kg soil dw) showed an inhibition of 18.5 %. Only for this concentration a significant difference compared to the control was stated. The EC50 could not be calculated, but it can be concluded that the EC50 is higher than 1441 mg LaCl3*6H20/kg soil dw (according to 566.5 mg La/kg soil dw), the highest concentration tested. The NOEC of the test item derived from the variance analysis was 720 mg LaCl3*6H2O/kg soil dw (according to 283.2 mg La/kg soil dw) after 28 days of exposure.

Since Lanthanum chloride has a high water solubility (861 g/L) compared to the water solubility of Lanthanum carbonate (1.24 mg/L), the test conditions has to be evaluated as a worst case scenario. It is to be expected, that the same study perfomed with Lanthanum carbonate will show no effects in this concentration range, since the Lanthanum ion of this test item is considerable lower bioavailable for the microorganisms.

 

Taken into account all available data and the general fact, that all data shown here were derived with highly soluble substances, the most sensitive data for terrestrial toxicity were available for earthworms with EC0 greater than 162 mg REE/kg dw and for plants with a NOEC of 250 mg La/kg dw.