Lanthanides
377
LA amounts contain mushrooms, which may suggest their aerial sources (Falandysz
et al. 2012).
Plants sampled in 1999 along the highways in Germany contained the following amounts of some LAs (in μg/kg): La, 38; Ce, 820; and Nd, 330. The highest
concentrations were always in dandelion (Djingova et al. 2003). Variable absorption
of LAs from a forest ecosystem is affected by their organic complexes and changes
in the oxidation state. The plant-to-soil ratio for almost all LAs in the needles of
Norway spruce was about 5 × 10 –3 , but revealed great variation among various trees
(Wyttenbach vide Kabata-Pendias 2011).
The main soil parameters controlling LA bioavailability are pH, SOM, and amorphous Fe oxides. There are also evidences that both microorganisms and earthworms increase their bioavailability (Aouad et al. 2006). Also micorrhizal fungi
may influence the translocation of some LAs from roots to shoots (Boulois de et al.
2008). Soybean roots reveal an ability to enhance mobility of LAs and to increase
their uptake by plants (Nakamaru et al. 2006).
There is no clear evidence on the toxic effects of LAs on plants; however, they have
impaired impact on cell membranes of vascular plants and on Ca metabolism in microorganisms. Although LAs may regulate some biological functions, their overdose has
inhibitory effects on all organisms. Although LAs are toxic to cell metabolism, there are
some elements (e.g., La, Pr, Nd, Eu, Tb) that regulate Ca accumulation by mitochondria
of microorganism cells. There are observations that La increases the accumulation of
several elements (e.g., Se, Co, Rb, V) in chloroplast of cucumber (Shi et al. 2006).
Although there are reports on the stimulating effect of LAs on several processes
in some plants, such as seed germination, root growth, nodulation, and chlorophyll
production, these elements have not yet been proved to be essential to plants.
57.6 HUMANS
The contents of some LAs in the human body (70 kg) are as follows (in mg): La,
<1.0; Ce, 40; and Sm, 0.05 (Emsley 2011). Their concentrations in the rib bones are
as follows (in mg/kg): La, 0.02; Ce, 0.029; Pr, 0.0032; Sm, 0.0014; Gd, 0.0015; Tb,
0.00041; Dy, 0.002; Er, 0.0011; Tm, ≤0.00006; Yb, 0.00072; and Lu, ≤0.00024.
The concentrations of Nd, Eu, and Ho are under the detection limit. In humans, the
amounts of Ce, Dy, Er, Gd, La, Nd, Pr, Sm, Tb, and Yb increase with age (Zaichik
et al. 2011).
LAs have no known biological role in living organisms, but they are present in
human bones, and to a lesser extent, in the liver and kidneys. Compared with other
metals, their toxicity is relatively low, especially when they are complexed by ligands.
LA ions are very close to Ca 2+ in properties and their pharmacological effects.
In general, their toxicity decreases with increasing atomic number, probably due to
greater solubility, ionic stability, and smaller radius.
The chemical forms of LA compounds determine deposition and retention of
LAs, following different ways of exposure. The clearance of chelated LAs from the
body depends on the stability of the complexes. The chelated LAs are excreted rapidly via urine, whereas unchelated ionic LAs easily form colloids in blood, which are
377
LA amounts contain mushrooms, which may suggest their aerial sources (Falandysz
et al. 2012).
Plants sampled in 1999 along the highways in Germany contained the following amounts of some LAs (in μg/kg): La, 38; Ce, 820; and Nd, 330. The highest
concentrations were always in dandelion (Djingova et al. 2003). Variable absorption
of LAs from a forest ecosystem is affected by their organic complexes and changes
in the oxidation state. The plant-to-soil ratio for almost all LAs in the needles of
Norway spruce was about 5 × 10 –3 , but revealed great variation among various trees
(Wyttenbach vide Kabata-Pendias 2011).
The main soil parameters controlling LA bioavailability are pH, SOM, and amorphous Fe oxides. There are also evidences that both microorganisms and earthworms increase their bioavailability (Aouad et al. 2006). Also micorrhizal fungi
may influence the translocation of some LAs from roots to shoots (Boulois de et al.
2008). Soybean roots reveal an ability to enhance mobility of LAs and to increase
their uptake by plants (Nakamaru et al. 2006).
There is no clear evidence on the toxic effects of LAs on plants; however, they have
impaired impact on cell membranes of vascular plants and on Ca metabolism in microorganisms. Although LAs may regulate some biological functions, their overdose has
inhibitory effects on all organisms. Although LAs are toxic to cell metabolism, there are
some elements (e.g., La, Pr, Nd, Eu, Tb) that regulate Ca accumulation by mitochondria
of microorganism cells. There are observations that La increases the accumulation of
several elements (e.g., Se, Co, Rb, V) in chloroplast of cucumber (Shi et al. 2006).
Although there are reports on the stimulating effect of LAs on several processes
in some plants, such as seed germination, root growth, nodulation, and chlorophyll
production, these elements have not yet been proved to be essential to plants.
57.6 HUMANS
The contents of some LAs in the human body (70 kg) are as follows (in mg): La,
<1.0; Ce, 40; and Sm, 0.05 (Emsley 2011). Their concentrations in the rib bones are
as follows (in mg/kg): La, 0.02; Ce, 0.029; Pr, 0.0032; Sm, 0.0014; Gd, 0.0015; Tb,
0.00041; Dy, 0.002; Er, 0.0011; Tm, ≤0.00006; Yb, 0.00072; and Lu, ≤0.00024.
The concentrations of Nd, Eu, and Ho are under the detection limit. In humans, the
amounts of Ce, Dy, Er, Gd, La, Nd, Pr, Sm, Tb, and Yb increase with age (Zaichik
et al. 2011).
LAs have no known biological role in living organisms, but they are present in
human bones, and to a lesser extent, in the liver and kidneys. Compared with other
metals, their toxicity is relatively low, especially when they are complexed by ligands.
LA ions are very close to Ca 2+ in properties and their pharmacological effects.
In general, their toxicity decreases with increasing atomic number, probably due to
greater solubility, ionic stability, and smaller radius.
The chemical forms of LA compounds determine deposition and retention of
LAs, following different ways of exposure. The clearance of chelated LAs from the
body depends on the stability of the complexes. The chelated LAs are excreted rapidly via urine, whereas unchelated ionic LAs easily form colloids in blood, which are