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Sediment toxicity

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Description of key information

The NOEC for fresh water sediment organisms (first instar larvae of Chironomus riparius)  was > 1317 mg La/kg dw or > 1545 mg lanthanum oxide/ kg dw based on a guidline study with Lanthanum trichloride hexahydrate

Key value for chemical safety assessment

EC10, LC10 or NOEC for marine water sediment:
1 545 mg/kg sediment dw

Additional information

The sediment toxicity of Lanthanum trichloride hexahydrate was investigated according to OECD 218 under GLP conditions (Dietzmann, 2010). First instar larvae of Chironomus riparius were exposed to a concentration range in a sediment water system, in which the test item Lanthanum trichloride hexahydrate was spiked into the sediment. Nominal concentrations were 673 - 3407 mg Lanthanum trichloride hexahydrate/kg dw, according to 460 - 2327 mg Lanthanum trichloride, anhydrous/kg dw or 260 to 1317 mg La/ kg dw, calculated from the measured La concentration of the stock solution. Chironomid emergence and development rate were measured at the end of the exposure period of 28 days. The EC50 could not be calculated because none of the concentrations tested had shown toxic effects to the chironomids. The NOEC could be stated as ≥ 2327 mg Lanthanum chloride, anhydrous/kg dw and corresponds to 1317 mg La/kg dry weight or 1545 mg Lanthanum oxide per kg dw.

The toxicity to sediment organisms of Lanthanum chloride is used for the assessment of lanthanum oxide sediment toxicity as well. As lanthanum chloride has a much higher water solubility, it is likely to have a higher bioavailability to sediment organisms and can be regarded as a worst case surrogate. The speciation in sediment will in any case also be dependent on the environmental or experimental conditions.