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Short-term toxicity to aquatic invertebrates

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Description of key information

The endpoint was covered using a weight of evidence approach including two studies. The study of Hefner (2014b) (using lanthanum trinitrate as test substance) reported a 48-h EC50 value of 3.0 mg La/L for Daphnia magna at a water hardness of 250 mg CaCO3/L, whereas the study of Barry and Meehan (2000) (using lanthanum trichloride as test substance) reported 48-h EC50 values of 0.0432, 0.049 and 1.180 mg La/L for Daphnia carinata at three different water hardnesses (22, 98 and 160 mg CaCO3/L, respectively). Water hardness clearly has a protective effect against lanthanum toxicity to cladocerans. Data from these two studies were lumped as justified by the read-across approach. However, instead of selecting the lowest EC50 (obtained at the lowest water hardness tested) as key value, the second lowest EC50 of 0.049 mg La/L (obtained at a water hardness of 98 mg CaCO3/L) was selected as key value for this endpoint. This value was obtained at a water hardness which is more representative for European surface waters than the lowest water hardness value tested. Because standard test media usually have much higher water hardness (e.g., 250 mg CaCO3/L, such as in the study of Hefner, 2014b), the selected key value can be considered as a worst case value. This value corresponds to 0.111 mg/L when expressed as La(CH3COO)3, indicating that lanthanum triacetate is very toxic to aquatic invertebrates.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
0.049 mg/L

Additional information

For acute toxicity of lanthanum to aquatic invertebrates, six studies were included in this dossier. As lanthanum toxicity does not appear to be significantly different after addition of various 'water soluble' lanthanum compounds, all available information were lumped for selection of a key value.

Two reliable studies were identified, one in which La(NO3)3 was used (Hefner, 2014b), and another in which LaCl3 was used (Barry and Meehan, 2000). The first study was conducted with Daphnia magna and yielded a 48-h EC50 value of 3.0 mg La/L (at a water hardness of 250 mg CaCO3/L). Barry and Meehan (2000) exposed Daphnia carinata for 48 h to LaCl3 in three different test media with increasing water hardness. The 48-h EC50 values were 0.0432 mg La/L in tap water (hardness 22 mg CaCO3/L), 0.049 mg La/L in Daphnia medium (hardness 98 mg CaCO3/L) and 1.180 mg La/L in ASTM hard water (hardness 160 mg CaCO3/L). There is clearly a protective effect of water hardness, which may be due to competition for uptake of Ca2+ (and/or Mg2+) and La3+ at the respective ion channels. The study with La(NO3)3 was performed in a test medium with a water hardness of 250 mg CaCO3/L and therefore it is not surprising that the 48-h EC50 value was higher than the highest one obtained by Barry and Meehan (2000). Inter-species sensitivity differences may however also be responsible for the observed differences. Both studies are used in a weight of evidence approach to cover this endpoint. The lowest value of 0.0432 mg La/L from Barry and Meehan (2000) was not taken forward as this was obtained in a soft water (22 mg CaCO3/L), being representative for only a very small part of the European surface waters. Therefore the value of 0.049 mg La/L, which was tested at a water hardness of 98 mg CaCO3/L is being considered as the key value that will be taken forward for PNEC derivation and classification. For classification purposes, it is important to note that this key value corresponds to a 48-h EC50 of 0.111 mg/L when expressed as La(CH3COO)3, meaning that lanthanum acetate is very toxic to aquatic invertebrates.

Further, there are four Klimisch 3 studies (not reliable) included in the dossier, two of which were assigned as supporting studies and the others as disregarded studies. Peterson et al. (1974) reported 48-h, 72-h and 96-h LC50 values of > 1.175, 0.66 and 0.38 mg La/L, respectively, for Daphnia magna exposed to lanthanum trichloride. These values are within the range of the values from the reliable studies, however, they were not considered reliable because no analytical monitoring was performed during the test. Oral et al. (2010) exposed sea urchin embryos (Paracentrotus lividus) for 72 h to lanthanum trinitrate and investigated developmental defects as well as mortality. An EC50 for developmental defects of 0.83 mg La/L was reported. This value is also within the range of the values from the reliable studies, however, it was not considered reliable either because lanthanum was not monitored during the experiments. The study of Bazin (1995) is the first disregarded study. This study reported a 48-h EC50 of > 100 mg/L (test substance La(NO3)3) for Daphnia magna in a limit test. Dissolved lanthanum analysis however indicated that lanthanum had precipitated and disappeared from the solution. Therefore the results of the study cannot be considered reliable because lanthanum toxicity may have been underestimated. The second disregarded study is the one from Bringmann and Kühn (1959), in which daphnids were exposed to lanthanum acetate for 48 h and 50% or more of the test organisms were found immobile at a (nominal) concentration of 160 mg La/L. The EC50 was reported to be <= 160 mg La/L, however, since no lanthanum measurements were performed in the test medium, this study did not yield useful results and was therefore disregarded.