Chemistry Reference
In-Depth Information
tellurium and tellurium dioxide) is absorbed in the
gut (Hollins, 1969; Taylor, 1996). The gastrointestinal
absorption of tellurium is completed within 2 hours
after the intake. In rats, the main part of the absorp-
tion takes place in the duodenum and jejunum, and
the total absorption was estimated to be in the range
10-25% (Slouka and Hradil, 1970). In sheep and pigs,
these compounds are mainly absorbed further down
in the colon (Wright and Bell, 1966).
(Durbin, 1960). After oral intake in rats, approximately
60-80% of ingested tellurium is rapidly excreted in the
feces. Tellurium is transferred to the intestine by biliary
excretion (Hollins, 1969; Slouka, 1970). Small amounts
may also be excreted in milk and sweat.
Small amounts, probably approximately 0.1%, of
absorbed elemental tellurium and tellurite are exhaled,
presumably as dimethyltelluride, causing a character-
istic garlic-like odor of breath and sweat (Cooper, 1971;
DeMeio, 1946).
5.1.3 Skin Absorption
5.4 Biological Half-Time
The whole-body excretion of tellurium and tel-
lurium compounds followed a two-phase pattern in
experiments on rats (Hollins, 1969; Slouka, 1970). The
fast phase had a biological half-time of approximately
19 hours (42-49% of the dose), and the fi gures for the
slow phase were 13-15 days (51-58%). The whole-
body retention model for man (ICRP, 1968) estimates
a biological half-time of approximately 3 weeks. In
rat experiments, biological half-times of 9.2 days were
found in blood, 10.2 days in liver, 17.7 days in muscle,
and 23 days in kidney (Hollins, 1969). The elimination
from bone seems to be very slow, with an estimated
half-time of approximately 600 days (Hollins, 1969).
The handling of tellurium compounds may cause
skin burns or rashes, followed by a garlic odor in the
breath indicating skin absorption. Blackadder and
Manderson (1975) reported two cases of chemists who
were accidentally exposed to tellurium hexafl uoride
gas when approximately 50 g leaked from a cylinder
in the laboratory. They both showed the character-
istic garlic odor of the breath, and one of them also
developed an intradermal bluish black pigmentation
in the skin of the fi ngers, face, and neck that took sev-
eral weeks to disappear. The authors suspected that
the skin absorption was caused by volatile tellurium
esters.
5.2 Distribution
In rat experiments, approximately 90% of tellurium
in blood enters the erythrocytes, probably bound to
hemoglobin (Agnew and Cheng, 1971; Slouka, 1970).
The main part of the remainder is bound to plasma
proteins. Tellurium can pass both the placenta and the
blood-brain barriers (Agnew, 1972; Agnew
et al
., 1968).
The highest tissue concentrations have been found in
the kidney. The levels observed in heart, lung, and
spleen have been approximately 10-30% of the kid-
ney concentrations. Levels in liver have been approxi-
mately 50% of those in the lungs, heart, and spleen.
Measured concentrations in cardiac muscle have been
approximately 20 times higher than in skeletal muscle.
In the nervous system, when injected intracerebrally,
tellurium accumulates in the gray matter. Tellurium
also accumulates with time in bone (Browning, 1969),
which harbors more than 90% of the total body burden
(Schroeder
et al
., 1967).
6 BIOLOGICAL MONITORING
6.1 Levels in Tissues and Biological Fluids
Tellurium concentrations in whole blood in normal
subjects may range from 0.15-0.3
g/L (van Montfort
et al
., 1979). Tellurium levels in urine in normal sub-
jects ranged from <0.1-10
µ
g/L (Fodor and Barnes,
1983; Kobayashi and Imaizumi, 1991). Observed con-
centrations in liver, lung, and kidney were 4-21 ppm,
0.04-1 ppm, and 0.6-16 ppm (
µ
g/g wet weight), respec-
tively (Iyengar
et al
., 1978). In a study of tellurium
concentrations in hair and nails of normal Japanese
adults, the levels as measured by hydride generation
atomic absorption spectrometry were lower than the
detection limit of the instrument (<1 ng/g; Fukabori
and Nakaaki, 1990; Nakaaki and Fukabori, 1990).
The estimated whole-body content in normal sub-
jects, as determined by neutron activation analysis, is
approximately 500 mg (Nason and Schroeder, 1967a).
µ
5.3 Excretion
The excretion pattern depends on the chemical forms
and mode of administration of tellurium and tellurium
compounds. Parenterally administered tellurium is
predominantly excreted in the urine, whereas orally
ingested tellurium salts are mainly excreted in the feces
6.2 Biomarkers of Exposure
Blood and urinary analyses may be used for bio-
logical monitoring, but data are very scanty. Tellu-
rium values for normal subjects have been reported
