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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

The endpoint was covered using a weight of evidence approach including ten publications that were assigned a K2 score (reliable with restrictions). Overall, bioconcentration/bioaccumulation was only observed to be high in organisms from lower trophic levels in the foodchain. Lanthanum does not seem to accumulate further in the aquatic foodchain, as was clear from the results of three studies with fish. A key BCF/BAF value of 4.29 L/kg ww  was calculated for fish as a worst case key value for use in case exposure calculations are needed for secondary poisoning (aquatic foodchain) or man via the environment.

Key value for chemical safety assessment

BCF (aquatic species):
4.29 L/kg ww

Additional information

Overall, ten publications (of which one review) were identified as useful in a weight of evidence approach for aquatic bioaccumulation. Data are available for fish, aquatic invertebrates, aquatic plants, and a blue-green alga. The available data were both from field studies and laboratory experiments and for both freshwater and marine organisms. In all studies, lanthanum concentration in (parts of) the exposed organisms was analytically determined, as well as lanthanum concentration in the water column (the latter was not the case in all studies). In the laboratory studies, soluble lanthanum compounds such as lanthanum trinitrate and lanthanum trichloride were used or sometimes also mixtures of salts of different rare earth elements were used (i.e., mixed exposure).

For aquatic plants (algae as well as higher plants) and blue-green algae, five studies were identified as containing useful information on bioconcentration of lanthanum. Weltje et al. (2002a,b) reported BCF values between 10000 and 19000 L/kg dw for Lemna minor sampled along the Rhine-Meuse estuary (corresponding to 2000 and 3800 L/kg ww, assuming 20% dw, which is a very conservative value for aquatic plants), whereas in a laboratory study with the same species, BCF values of 17175 to 32970 L/kg dw were obtained (also reported as 1145 to 2198 L/kg ww). Sakamoto et al. (2008) reported BCF values of 1800 and 2400 L/kg dw for two species of brown algae sampled along coasts in Niigata Prefecture, Japan (corresponding to 360 and 480 L/kg ww, assuming 20% dw). In a microcosm study in which goldfish, shellfish, Daphnia and duckweed were exposed for up to 16 days to lanthanum, a BCF value of 138.1 L/kg ww (corresponding to 690.5 L/kg dw, assuming 20% dw) was calculated for duckweed for the 16 -d sampling point (Yang et al., 1999). And finally, Zhou et al. (2004) performed a laboratory study with the blue-green alga Microcystis aeruginosa and obtained BCF values of 18760 to 24700 L/kg dw (corresponding to a range of 3752 to 4940 L/kg ww, assuming 20% dw). The overall range of BCF values obtained in these studies was 690.5 to 32970 L/kg dw (corresponding to a range of 138.1-4940 L/kg ww), indicating that lanthanum is bioconcentrated in aquatic plants and blue-green algae.

Five studies contained useful information on bioconcentration/bioaccumulation of lanthanum in aquatic invertebrates. Sneller et al. (2000) discussed the results of Tijink and Yland (1998) and Stronkhorst and Yland (1998). The first study calculated BAF values for worms, crustaceans and bivalves taken from the Dutch Rhine estuary. The latter study calculated BAF values for amphipods (Corophium volutator) taken from a harbour in the Netherlands and also investigated bioconcentration of lanthanum in this species in the laboratory (using field sediment). The values from these studies ranged from 8000 to 120000 L/kg dw (corresponding to 1600 to 24000 L/kg ww, assuming 20% dw). Moermond et al. (2001) reported BAF/BCF values for Corophium volutator taken from the field (Dutch locations) as well as for a laboratory study with the species. The values ranged from 2340 to 12000 L/kg dw (corresponding to 468 to 2400 L/kg ww, assuming 20% dw). For snails and molluscs sampled along the Rhine-Meuse estuary, Weltje et al. (2002a) reported BAF values of 9000 to 200000 and 10000 to 30000 L/kg dw, respectively (corresponding to an overall range of 1800 to 40000 L/kg ww, assuming 20% dw). And finally, in the microcosm study of Yang et al. (1999) the BAF values after 16 days of exposure were 2.11 and 700 L/kg ww for shellfish and Daphnia, respectively (corresponding to 10.55 and 3500 L/kg dw, assuming 20% dw). Overall, the BCF/BAF values ranged from 10.55 to 200000 L/kg dw (corresponding to a range of 2.11 to 40000 L/kg ww), indicating that lanthanum is also bioconcentrated in aquatic invertebrates.

For bioconcentration/bioaccumulation in fish, three studies were identified. Two laboratory studies (Sun et al., 1996; Tu et al., 1994) reported BCF values for muscle, skeleton, gills, and internal organs of carp (Cyprinus carpio) after around 45 days of exposure to a mixture of rare earth elements, among which lanthanum. Maximum BCF values for muscle tissue, skeleton, gills, and internal organs were 3.2, 6.1, 18 and 828 L/kg ww, respectively. The BCF values for internal organs were highest but are not considered as a good indication of the bioconcentration potential of lanthanum, since the alimentary tract reflects the normal transit of the substance. The third study (Yang et al., 1999) was a microcosm study in which goldfish, shellfish, Daphnia and duckweed were exposed for up to 16 days to lanthanum. The BAF value for goldfish (Carassius auratus) appeared to be < 1 L/kg ww, based on whole body analysis. This is in agreement with the low values for muscle and skeleton observed in the other studies. Therefore, it can be concluded that the bioaccumulation potential of lanthanum in fish is very limited.

Overall, bioconcentration/bioaccumulation in fish seemed to be substantially lower than in organisms at a lower level in the food chain. The fact that goldfish in a microcosm study (in which they could feed on other organisms present in the microcosm) did not bioaccumulate lanthanum (BAF < 1 L/kg ww) indicates that the high bioconcentration/bioaccumulation is leveled out when ascending along the foodchain. Clearly, lanthanum has a very limited potential to bioaccumulate through the foodchain and it definitely does not biomagnify. Similar differences in bioconcentration/bioaccumulation between different trophic levels have been observed for other metals. In case exposure assessments need to be performed, a value is needed that can be used for calculating exposure levels in prey via the generic scenario for secondary poisoning starting in the aquatic foodchain, as well as for calculating exposure levels for exposure of man via the environment. An average (geometric mean) BAF of 4.29 L/kg ww for fish was therefore calculated based on the results of the three available studies. Before calculating the overall mean, a study-specific mean (geometric mean) was calculated for each study. All data were included, i.e. also data for internal organs. Therefore, the average BAF of 4.29 L/kg ww can be considered as a worst case value.

Finally, on the relatively high values observed for aquatic plants, blue-green algae, and aquatic invertebrates, it should be noticed that many of the studies investigated bioconcentration/bioaccumulation at a very low environmental concentration of lanthanum (e.g., 1 µg La/L or lower). What is often observed for metals is that bioconcentration/bioaccumulation is concentration dependent, showing increasing BCF/BAF values with decreasing (almost background) environmental concentrations. This may also have shifted the upper boundaries of the ranges for these trophic levels up. Overall, the results for fish clearly indicate that bioconcentration/bioaccumulation is typically high only for lower trophic levels and lanthanum does not further accumulate through the foodchain. Metals are typically well regulated by living organisms, especially when they are essential for their vital functions. For lanthanum, there is evidence available that it is an essential element that is needed at extremely low concentrations. The concentration dependency of the BCF/BAF values in organisms from lower trophic levels may be explained to a certain extent by this essentiality.