Lanthanum(3+) acetate

Toxicity to terrestrial plants

Description of key information

The endpoint is covered using two studies in a weight of evidence approach. The study of Hu et al. (2006) exposed maize seedlings (Zea mays) to La(NO3)3 in a natural Chinese soil and yielded a 14-d NOEC of 250 mg La/kg soil dw (added lanthanum) for root elongation and root dry weight and a 14-d NOEC of 500 mg La/kg soil dw (added lanthanum) for shoot dry weight. The study of Zeng et al. (2006) exposed rice seedlings (Oryza sativa) to LaCl3 in red soil and paddy soil and reported a 68-d NOEC and EC50 of 46.3 and 323.02 mg La/kg soil dw, respectively, in red soil, and a 68-d NOEC and EC50 of 56.1 and 646.6 mg La/kg soil dw, respectively, in paddy soil. The NOEC and EC50 obtained in red soil were selected as key values for this endpoint. They correspond to 105 and 735 mg lanthanum acetate/kg soil dw.

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for terrestrial plants:

46.3 mg/kg soil dw

Additional information

Three studies were identified as containing relevant and reliable information on toxicity of lanthanum to terrestrial plants.

Two studies can cover the endpoint in a weight of evidence approach. In the study of Hu et al. (2006), maize seedlings (Zea mays) were exposed for 14 days to a lanthanum concentration series (added as La(NO3)3) in a natural Chinese soil. The 14-d NOEC for root elongation and root dry weight was 250 mg La/kg soil dw (added lanthanum), whereas for shoot dry weight it was 500 mg La/kg soil dw (added lanthanum).

In the study of Zeng et al. (2006), Oryza sativa (rice) seedlings were exposed for up to 120 days to a concentration series of lanthanum (added as LaCl3) in two different natural soils. In red soil, a 68-d NOEC and EC50 of 46.3 and 323.02 mg La/kg soil dw were obtained, respectively. In paddy soil, the 68-d NOEC and EC50 were 56.1 and 646.6 mg La/kg soil dw, respectively. The NOEC and EC50 obtained in red soil were selected as key values for this endpoint. They correspond to 105 and 735 mg lanthanum acetate/kg soil dw.

In the last study (Zhang et al., 2001), ReCl3.6H2O (containing mainly light rare earth elements) was added to three different soils for investigation of the effects of rare earths on growth and seedling emergence of Brassica napus, Glycine max and Oryza sativa. Test duration was 14 days. The overall range of EC50 values was 603 to 4152 mg/kg soil dw, when expressed as total rare earth elements (light, average molecular weight assumed to be 146.1 g/mol). Because no individual concentrations of rare earth elements were available, this study can only be considered as supporting study and indicative of which lanthanum concentrations elicit toxicity to terrestrial plants. The results were consistent with those of the other studies.