Chemistry Reference
In-Depth Information
average 0.88 mg Ge/kg wet weight. The daily intake of
germanium may vary from 0.4-3.5 mg (Schroeder and
Balassa, 1967a). Hamilton and Minski (1972, 1973) esti-
mated that the mean daily intake in the United King-
dom to be 0.367 ± 0.159 mg by SSMS. The estimated
dietary intake for a “reference man” is approximately
1.5 mg Ge/day of which 96% or more is absorbed (Sny-
der
et al
., 1975). Estimation of the mean of human daily
intake of Ge from food is 1.5 mg/day (with a range of
0.40-3.40) (Okada
et al
., 1991; Shauss, 1991).
concentrations (2-9 ppm) of Ge may be found in beans,
tomato juice, oysters, tuna, garlic, aloe vera, ginseng,
shelf fungus, and green tea. Tissue levels higher than
5 ppm are toxic to most plants.
4.2 Working Environment
Exposure to Ge tetrachloride and its hydrolysis
products (GeO
2
and HCI) may occur in the produc-
tion process of germanium and its compounds. Dust
concentrations ranging from 5-70 mg/m
3
(correspond-
ing to germanium concentrations up to approximately
7 mg/m
3
) have been reported to occur in the produc-
tion of germanium monocrystals. In some cases, the
samples contained up to 30% of free silica (Goldman,
1960; Mogilevskaja, 1973). Swennen and coworkers
observed, for exposed and control workers, no signifi -
cant differences in the germanium urine levels taken
at the beginning and the end of the workweek. These
authors also reported no overt clinical health effects for
the two groups of workers; however, slightly higher
than control levels of albumin and transferrin and
some low-molecular-weight proteins were reported
in exposed workers as discussed later. The geomet-
ric mean of the cumulative frequency of germanium
levels in the air during 5 working days ranged from
1.07-5.11
4.1.1 Water, Soil, and Ambient Air
Braman and Tompkins (1978) used emission spec-
trometry to measure Ge concentrations in U.S. freshwa-
ter and saline samples. They reported a concentration
range from less than 4- 600 ng/L (Oregon well waters)
and in some saline waters, the concentration range was
from less than 4 ng/L to approximately 200 ng/L. Rei-
mann
et al
. (1978) analyzed 145 hard rock ground water
and surface water samples from Norway and Finland
and found the median content of germanium to range
between 0.015 and 0.44
g/L.
Samples of soils in the United States contained
0.6-1.3 mg Ge/kg (Schroeder and Balassa, 1967a),
which is of the same order of magnitude as the abun-
dance of germanium found in the earth's crust (1.5 mg/
kg) (Fyfe, 1974).
Considerable amounts of Ge are discharged into
the atmosphere by coal combustion. Paone (1970) esti-
mated 2000 tons per year to be discharged in stack
gases, fl ue dusts, and ashes from coal-burning plants in
the United Kingdom. Coal ash may contain 20-280 mg
Ge/kg (Coal Research Section, 1972). Concentrations
of germanium in air particulates may range from less
than 0.01 ng/m
3
to approximately 1700 ng/m
3
(Braman
and Tompkins, 1978). Lifetime consumption of 5 ppm
Ge in drinking water resulted in liver and kidney dys-
functions of the experimental animals.
µ
µ
g/m
3
(Swennen
et al
., 2000).
5 TOXICOKINETICS
5.1 Absorption
5.1.1 Inhalation
The rate of clearance of deposited elemental germa-
nium particles (mean size, 1.4
m) from the lungs of
rats was found to be exponential (52% in 24 hours, 18%
remaining 7 days after exposure). Radiochemical exam-
ination of the tissues showed that part of the material
entered the circulation and reappeared in the kidney
and liver 1 hour after exposure. The clearance of ger-
manium dioxide particles (mean size, 0.4
µ
4.1.2 Plants, Fishery Products, and Microbial
Organisms
m) was more
rapid than that of elemental Ge particles (79% within
24 hours) (Dudley, 1953).
µ
Germanium is a constituent of various medicinal
plants and microorganisms (Park and Han, 1979; Slaw-
son
et al
., 1992; Staufer, 1980). Ge has been reported in
sargassum and its epiphytes at concentrations of up
to 4.2
5.1.2 Ingestion
Neutralized Ge dioxide was rapidly absorbed in
rats after gavage (73.4% in 4 hours; 964% in 8 hours)
(Rosenfeld, 1954). Equally rapid absorption of tetra-
ethylgermanium from the gastrointestinal tract of mice
was found by Caujolle
et al
. (1963). Schroeder and
Balassa (1967a) reported that the concentrations of ger-
manium in human urine were approximately the same
g/kg (Johnson and Braman, 1975). Also, ger-
manium has been found to accumulate in a variety of
microorganisms. The accumulation rate of germanium
depends on environmental pH, temperature, and sil-
icic acid concentration within the cell. The growth
inhibition by GeO
2
was more pronounced in yeast
than bacteria (Lee
et al
., 1990). Traces of Ge usually
exist in soil, plants, and animal tissues; however, high
µ
