Lanthanum oxide

Endpoint summary

Additional information

No classical bioaccumulation study according to OECD guideline 305 is available for Lanthanum oxide.

According to “Guidance on information requirements and chemical safety assessment Appendix R.7.13-2: Environmental risk assessment for metals and metal compounds” the determination for bioaccumulation potential for naturally occurring substances such as metals, is more complex and most concepts and tools to assess the bioaccumulation were inadequate for the assessment of metals since the methods were originally developed on limited results obtained for neutral lipophilic organic substances that have shown that their potential to bioaccumulate and/or to biomagnify is directly related to the inherent properties of the substance.

A number of laboratory studies with soluble lanthanum compounds and field studies have investigated bioconcentration of lanthanum in different aquatic species and possible biomagnification in food chains.

Overall it can be concluded that lanthanum does not biomagnify in the aquatic food chain and does not lead to a concern with regard to secondary poisoning. Lanthanum oxide, because of its low water solubility, in particular is assumed to have a low bioavailability even for algae and zooplankton that were shown to accumulate soluble lanthanum to a certain extend. Thus a bioaccumulation is not to be expected.

Rikken (1995) summarized literature data on the accumulation of rare earth metals (RE) in plants, as a part of the investigation of data on the transfer of RE in the chain artificial fertilizers - soil - crops - livestock and man. The data for concentration of Lanthanum in different vegetables and feeding stuffs and the soil were collected and bioconcentration factors (according to mg/kg dw in plant and soil) were calculated.

The concentration and accumulation of rare earth metals (RE) in plants differed as a consequence of plant and soil factors (e.g. species, Ca-content).The concentrations in plants (dry weight) of REs were in general low: < 0.2 mg/kg for root - and leaf vegetables, < 0.05 mg/kg in most fruits and < 1 mg/kg in herbs/grasses. Bioconcentrationfactors (BCF) for RE are usually within a range of 0.0001 to 0.001 for feed crops and 0.0001 to 0.01 for food crops. For Lanthanum BCFs were in a range of < 0.00017 - 0.0052 for food crops and 0.00002 - 0.094 for feed crops.

Also Redling (2006) reviewed, that according to extremely small concentration ratios, the transfer of rare earth elements from soil into plants is very low. Concentration ratios of rare earths (mass of rare earths in dry weight of plant per mass in dry weight of soil) were reported to be generally in a range of 0.8 to 0.001. Furthermore, the very low concentrations of REs in cereal grains were confirmed and no significant accumulation was stated.

Furthermore, Tyler (2004) reviewed the information about rare earth elements in soil and plant systems and arrived at the conclusion that concentrations of REs in plants are usually very low compared to their total concentration in soils. For example, BCFs (calculated on dry weight) in forest plants of NW Germany were given, they were as low as 0.04 - 0.09.

So generally, the reviewed data indicated a low accumulation potential of Lanthanum in plants. Furthermore,it can be assumed that there is no risk for accumulation in the food chain.