Europium can be used to detect
chrome in contaminated water
Uses in Medicine :
Many rare earths were and/or are used as diagnostic
and therapeutic tools.
Rare Earth Analysis :
With the exception of cerium, atomic absorption spectrophotometry
is the method of choice for rare earth quantitative determination.
Biologic effects :
I-Absorption :
The rare earth metals are not absorbed from the skin,
are poorly absorbed from the gastrointestinal tract, and are
slowly absorbed from the lungs or on injection.
On absorption, scandium and the rare earth metals tend
to collect in the liver and the skeleton. There is a transition
to more bone with the rare earths of higher atomic number.
After deposition in the skeleton it may take years before
removal is completed.
Starvation lessened the excretion.
II-Clinical Findings :
A-General :
Headache and nausea from dust and fumes from using
cored light carbons containing lanthanum has been reported.
B-Lungs :
1-Acute exposure :
If in great enough quantity, the rare earth compounds
can produce, on inhalation, acute chemical irritation pneumonitis,
and bronchitis.
2-Chronic exposure :
More than 20 cases of occupational pneumoconiosis have
been reported, mainly in photoengravers and projectionists,
from chronic inhalation of rare earth oxide fumes from carbon
arc lamps.
Cerium, lanthanum, and neodymium are the major oxides
in the fumes; but samarium, terbium, ytterbium,and lutenium
have also been removed from fibrotic pneumoconiosis nodules.
In some of these cases abnormal levels of rare earths were
demonstrated in the nails suggesting absorption from the lungs.
C-Skin :
Terbium chloride has been noted to be an irritant to
the intact skin.
Gadolinium and samarium chlorides produced ulcers on
abraded skin.
Lutetium and europium chlorides caused extensive scarring
on abraded skin, and, along with dysprosium, holmium, and
erbium, produced nodules from intradermal injections.
D-Eyes :
The chloride of each of the rare earths caused ocular
irritation in the form of transient conjunctivitis. In addition,
terbium chloride produced corneal damage.
The lanthanons can produce opacity to the abraded cornea.
Diagnostic Methods :
There are no signs or symptoms pathognomonic of toxicity
from lanthanons.A history of exposure would be necessary in
making the diagnosis.
A-Chest X-Ray :
1-Acute Exposure :
A chest x-ray after massive acute inhalation might
show signs of oedema or pneumonitis.
2-Chronic Exposure :
Chronic inhalation can produce a diffuse nodular pattern
on chest x-ray from the birotic nodules composed of rare earths.
The pulmonary function test might show a restrictive pattern.
Energy dispersive x-ray fluorescence of bronchoalveolar
lavage fluids can establish or confirm occupational exposure
of workers to rare earths.
B-Urinary Excretion :
Excretion of the rare earth metals in the urine is
a small part of the total excretion by the body but could
be measured accurately. No standards of urinary level have
been established, because it is not yet known if there is
a correlation between the urinary level and either the exposure
or the fecal excretion.
C-Fecal Excretion :
Ingestion estimates have usually been based on measurements
of the rare earths in the feces.
Fecal excretion of lanthanons is measurable. The level
of excretion varies greatly with the route of exposure and
the solubility of the lanthanon.
No indices of toxicity based on fecal excretion have
been established, but fecal levels do afford an inconvenient
method of monitoring exposure.
Treatment :
Some lanthanons delay healing, cause irritation and
ulcers on abraded skin, and form nodules intradermally. Extra
care should be used in cleaning wounds contaminated with a
lanthanon.
If lanthanon toxicity is suspected, the patient should
be removed from further exposure.
There is no specific therapy, and treatment of any
findings that are believed to be related to the lanthanon
exposure, such as acute chemical pneumonitis, hematuria or
leukopenia, are treated in the usual manner.
Exposure Limit :
The VEMP in Quebec for yttrium is 1mg/m3.
Exposure Control :
Incidental ingestion is considered harmless.
Skin contact should be avoided, especially with rare
earths of the terbium and ytterbium groups.
Employees with skin cuts, abrasion, dermatitis, conjunctivitis,
corneal injuries, or keratoconus need protection that will
prevent contamination of the skin lesion or the eye by any
rare earth.
Employees with lung disease, decreased pulmonary function,
or x-ray evidence of fine lung opacities (pneumoconiosis)
need special consideration to avoid rare earth dusts or fumes.
Consideration should be given to avoiding exposure
to rare earths for employees with increased blood coagulation
time or leukopenia.
Heated rare earths give off toxic fumes that should
be controlled.
Edouard Bastarache M.D. (Occupational & Environmental
Medicine)
Author of « Substitutions for Raw Ceramic
Materials »
edouardb@sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/~edouardb/
Sorel-Tracy
Québec
Canada
References :
1-Occupational Medicine, Carl Zenz, last edition.
2-Sax’s Dangerous Properties of Industrial Materials,
Lewis C., last edition.
3-Toxicologie Industrielle et Intoxications Professionnelles,
Lauwerys R.R.,last edition.
4-INRS, Exposition aux poussières de terres rares,
Peltier A., 1986
