Table 1.
Summary of toxicological information about the REEs
| Element (abbreviation) | Acute toxicity (LD50) |
Repeated toxicity (NOEL, NOAEL, LOAEL) |
Reference dose or concentration (RfD, RfC) |
Remarks | ||||
|---|---|---|---|---|---|---|---|---|
| Oral (mg/kg) | Inhalation (mg/L, 4h) | Oral (mg/kg/day) | Inhalation (mg/m3) | Oral (mg/kg/day) | Inhalation (mg/m3) | |||
| Scandium (Sc) | ScCl3 | 755 (rats) | Sc is regarded as nontoxic, but toxic information is insufficient. | |||||
| Yttrium (Y) | Y | >2,000 (♀, rats) |
Inhalation of Y citrate (C6H5O7Y) induced dyspnea and pulmonary edema, and inhalation of Y chloride (YCl3) induced pleural effusions, pulmonary hyperemia, and liver edema in rats. Water-soluble Y compounds have mild toxicity. The data of carcinogenicity are available. | |||||
| Y2O3 | >5,000 (rats) | >5.09 (rats) | 1,000† (28∼54-day, rats) |
>20.63∗ (30-day, dogs) |
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| Y(NO3)3 | 1650 (rats) | ≥1,000† (32∼44-day, rats) |
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| YCl3 | 0.004 | |||||||
| YF3 | >2,000 (♀, rats) |
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| Lanthanum (La) | La2O3 | >10,000 (rats) | ≥5.3 (rats) | ≥525† (♂), ≥799† (♀) (90-day, rats) |
0.5‡ (28-day, ♂, rats) |
0.02 | Injection of La induced reduced blood pressure, hyperglycemia, hepatic alterations, and spleen degeneration in in vivo experiments. | |
| La(NO3)3 | 4,500 (rats) | ≥1,000† (46∼49-day, rats) |
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| La3 | 2,621 (rats) | ≥738† (♂), ≥1,122† (♀) (90-day, rats) |
0.005 | |||||
| La2(CO3)3 | >5.928 (rats) | 974† (♂), 1,480† (♀) (90-day, rats) |
0.5 | |||||
| La(OH)3 | >2,000 (♀, rats) |
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| LaF3 | >2,000 (♀, rats) |
>5.1 (rats) | 1,000† (4∼6-week, rats) |
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| Cerium (Ce) | CeO2 | >5,000 (rats) | >5.05 (rats) | 1,000∗ (28∼54-day, rats) |
50.5‡ (13-week, rats) |
0.0009 | Injection of large doses of Ce induced cardiovascular collapse, resulting in death in experimental animals. Ce nitrate was reported to cause chromosomal aberrations. Ce fires produce toxic fumes. | |
| Ce(NO3)3 | 4,200 (♀, rats) | 110∗, 330† (47-day, rats) |
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| Ce(NO3)4 | >2,000 (♀, rats) |
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| CeCl3 | 2,800 (rats) | |||||||
| Ce2(CO3)3 | >5,000 (rats) | 150∗, 450† (28∼54-day, rats) |
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| CeF3 | ≥2,000 (rats) | >5.53 (rats) | 1,000∗ (4∼6-week, rats) |
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| Neodymium (Nd) | Nd2O3 | >5,000 (rats) | >4.98 (rats) | 300∗, 1,000† (♂) 300† (♀) (4∼6-week, rats) |
0.5‡ (28-day, ♂, rats) |
Nd compounds have low to moderate toxicities, but their toxic information is limited. Nd dust and salts irritate the eyes and mucous membranes highly and the skin moderately. Nd oxide (Nd2O3) was reported as mutagen. | ||
| Nd(NO3)3 | 2,750 (♀, rats) | |||||||
| NdCl3 | 5,068 (rats), 5,250 (mice) |
840† (♂), 950† (♀) (90-day, rats) |
0.8§ | |||||
| Nd2(CO3)3 | >2,000 (♀, rats) |
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| Nd(OH)3 | >2,000 (♀, rats) |
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| NdF3 | >5,000 (rats) | |||||||
| Promethium (Pm) | Pm may affect the human bone tissue. | |||||||
| Samarium (Sm) | Sm(NO3)3 | 2,900 (♀, rats) | 0.00004§ | Water-soluble Sm compounds are slightly toxic. | ||||
| SmCl3 | 3,200 (rats) | 0.9§ | ||||||
| Europium (Eu) | Eu2O3 | 0.002 | Eu was reported to be relatively nontoxic compared to other heavy metals. | |||||
| Eu(NO3)3 | >5,000 (♀, rats) |
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| EuCl3 | 5,000 (mice) | 200∗ (28-day, rats) |
0.03 | |||||
| Gadolinium (Gd) | Gd | >2,000 (♀, rats) |
Free Gd ions are highly toxic, and mutagenicity data (micronucleus, chromosomal effects) is available. About 0.03∼0.1% of anaphylactoid reactions were reported. | |||||
| Gd2O3 | >1,000 (♀, rats) |
>5.04 (rats) | 1,000† (11∼12-week, rats) |
0.002 | ||||
| Gd(NO3)3 | >5,000 (♀, rats) |
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| Thulium (Tm) | TmCl3 | 6,250 (mice) | Water-soluble Tm compounds are slightly toxic. | |||||
| Dysprosium (Dy) | Dy2O3 | >5,000 (rats) | Water-soluble Dy compounds such as Dy chloride and Dy nitrate are mildly toxic. | |||||
| Dy(NO3)3 | 3,100 (♀, rats) | |||||||
| DyCl3 | 7,650 (mice) | |||||||
| Ytterbium (Yb) | Yb2O3 | >2,000 (♀, rats) |
>1.31 (rats) | 1,000† (15∼16-week, rats) |
All Yb compounds are regarded as highly toxic due to their irritation for the skin and eye and the possibility of teratogenic effects. | |||
| Yb(NO3)3 | 3,100 (♀, rats) | |||||||
| YbCl3 | 6,700 (mice) | |||||||
| YbF3 | >2,000 (♀, rats) | |||||||
| Lutetium (Lu) | Lu2O3 | >2,000 (♀, rats) |
≥1,000† (12∼13-week, rats) |
Inhalation of Lu fluoride and oxide powders is dangerous. Water-soluble Lu compounds are mildly toxic. | ||||
| Lu(NO3)3 | >300, ≤2,000 (♀, rats) |
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| LuCl3 | 7,100 (mice) | 0.5§ | ||||||
| Praseodymium (Pr) | Pr2O3 | >2,000 (rats) | >5.21 (rats) | 1,000† (4∼6-week, rats) |
Pr compounds have low to moderate toxicities. | |||
| Pr(NO3)3 | 3,500 (♀, rats) | |||||||
| PrCl3 | 4,500 (♂, mice) | ≥10,000† mg/kg diet (90-day, rats) | 0.8§ | |||||
| Pr2(CO3)3 | >2,000 (♀, rats) | >5.25 (rats) | ||||||
| Terbium (Tb) | Tb(NO3)3 | >5,000 (♀, rats) |
Tb compounds have low to moderate toxicities, but their toxicity information is limited. | |||||
| TbCl3 | 5,100 (mice) | |||||||
| Holmium (Ho) | Ho(NO3)3 | 3,000 (rats) | Ho compounds have low acute toxicity. | |||||
| HoCl3 | 7,200 (mice) | |||||||
| Erbium (Er) | Er2O3 | >2,000 (rats) | >5.09 (rats) | 1,000† (♂), 300∗ (♀) (4∼6-week, rats) |
Er compounds have low to moderate toxicities, but their toxicity information is limited. | |||
| ErCl3 | 6,200 (mice) | |||||||
LD50, lethal dose 50; NOEL, no-observed-effect level or concentration; NOAEL, no-observed-adverse-effect level or concentration; LOAEL, lowest observed adverse effect level or concentration.
∗
NOEL value.
†
NOAEL value.
‡
LOAEL value.
§
Provisional subchronic RfD.