Chemistry Reference
In-Depth Information
CHAPTER
40
Tellurium
LARS GERHARDSSON
ABSTRACT
and hind leg paralysis. Long-term studies of chronic
effects are sparse. Dominant and critical effects have
been reported from the nervous system, including
peripheral neuropathy characterized by segmental
demyelination and minor axonal degeneration. In the
brain, black changes caused by dark tellurium parti-
cles that were localized in lipofuscin granules in neu-
ron cytoplasm have been observed. Other effects have
been reported from the liver (fatty degeneration and
necrosis), kidney (proximal tubular lesions, oliguria,
or anuria), and heart (cell necrosis, edema, and con-
gestion).
Reproductive effects including, for example, hydro-
cephalus, edema, exophthalmia, and ocular hemorrhage
have been described.
Acute exposure to tellurium in occupational settings
may cause acute respiratory irritation followed by
the development of garlicky odor of the breath and
sweat, drowsiness, headache, malaise, lassitude,
weakness, and dizziness. Gastrointestinal symptoms
such as anorexia, nausea, vomiting, metallic taste, dry
mouth, and constipation may appear. Dermatitis and
blue-black discoloration of the skin may follow from
exposure to tellurium hexafl uoride. Severe intoxica-
tion may lead to depression of the respiratory system
and circulatory collapse. No specifi c antidote for tel-
lurium poisoning has been found. After inhalational
exposure, treatment with fresh air, oxygen supply, as-
sisted ventilation, beta
2
agonists, and oral or parenter-
al corticosteroids can be tried. Reviews of tellurium
toxicology have been published by Browning (1969),
Izrael'son (1973), Fishbein (1977), Alexander
et al
.,
(1988) and Kobayashi (2004).
The main source of exposure in the general population
is food (e.g., meat, dairy products, and cereals). In the
working environment, inhalational exposure predomi-
nates. Small amounts of organic tellurium compounds
can also be absorbed through the skin. No quantitative
data have been published regarding the inhalational
or gastrointestinal absorption of tellurium or tellu-
rium compounds in humans. In animal experiments,
the intestinal absorption has been estimated to range
between 10 and 25%.
The highest tissue concentrations have been observed
in the kidneys. Increased levels have also been noted
in blood, heart, lungs, liver, spleen, muscle, and bone.
The main accumulation is in bone, which harbors >90%
of the total body burden. Tellurium can pass both the
placenta and the blood-brain barriers. Parenterally
administered tellurium is predominantly excreted in the
urine, whereas orally ingested tellurium salts through
biliary secretion are mainly excreted in the feces. Small
amounts, probably approximately 0.1%, of absorbed
tellurium are exhaled, presumably as dimethyltelluride.
In rat experiments, biological half-times ranging from 9
days in blood to 23 days in kidney have been reported.
The whole-body retention model for man estimates
a biological half-time of approximately 3 weeks. The
elimination from bone is slow, with an estimated half-
time of approximately 600 days.
Acute systemic effects of tellurium toxicity in rats
include listlessness, decreased locomotor activity,
somnolence, anorexia, weight loss, gastrointestinal
disturbances, changes in fur, and occasionally epilation
