Chemistry Reference
In-Depth Information
origin. A study of male workers moderately exposed
to manganese dust (Lauwerys
et al
., 1985) showed a
signifi cantly reduced rate of live births compared with
a control group (39 births observed vs. 70.5 expected);
in a similar study, no effect of manganese was found
( Gennart
et al
., 1992b). This may be due to higher levels
of manganese in the former study (12.0 vs 8.2
the antioxidants, vitamin E and especially vitamin C
(Acharya
et al
., 2004).
2.6 Nickel
In a study of male welders, whose blood nickel levels
were 123.3 ± 35.2
µ
g/L mean
g/L, a signifi cant positive correlation
was found between the percentage of morphologically
abnormal sperm with sperm tail defects and the blood
nickel levels (Dandevi
et al.,
2003).
Experiments in animals have shown testicular toxic-
ity involving oxidative stress after high doses of nickel.
This is evidenced by increased lipid peroxidation, DNA
damage, and apoptosis in the testes, morphological
sperm head abnormalities, and decreased fertility in mice
(Doreswamy
et al
., 2004); decreased DNA, RNA, and total
protein in testes, and decreased sperm count and motility
in rats (Das and Dasgupta, 2000); and decreased absolute
and relative weights of testes, epididymides, seminal vesi-
cles and prostate gland, decreased sperm count and motil-
ity, and increased abnormal sperm morphology in mice
(Pandey
et al
., 1999). Other reports provide some evidence
that nickel may be essential for male reproduction in rats
(Nielsen
et al
., 2002; Yokoi
et al
., 2003).
µ
blood levels; 1.50 vs. 0.84
g/g creatinine in urine).
A high single dose of manganese (160 mg MnO
2
/kg
by intratracheal instillation) caused degenerative testicu-
lar changes and sterility in rabbits (Chandra
et al
., 1973;
Seth
et al.,
1973). Chronic dietary exposure of young rats
to manganese Mn
3
O
4
for 224 days resulted in no effect on
male fertility at manganese doses <1100 ppm, whereas at
a dose of 3500 ppm decreased testicular weight, sperm
count, and serum levels of FSH and testosterone were
noted together with general toxic effects (Laskey
et al
.,
1982). In mice orally exposed to manganese acetate for
43 days, a signifi cant decrease in sperm count and motil-
ity was observed at doses of 15.0 and 30.0 mg/kg/day,
whereas there was no effect on fertility and testicular
pathology (Ponnapakkam
et al
., 2003).
µ
2.5 Chromium
In male workers exposed to chromium (VI) for 1-15
years in an electroplating factory, compared with unex-
posed workers (Li
et al
., 2001), signifi cantly decreased
sperm concentration (by 47%), sperm motility, and semi-
nal plasma levels of zinc, lactate dehydrogenase, and
the lactate dehydrogenase isoenzyme LDH-C
4
were
found, whereas serum FSH was signifi cantly increased;
serum chromium levels in exposed workers were
1.40 ± 0.01
2.7 Arsenic
No relevant evidence with regard to dose-response
relationship for the human male is available because of
a small number of studies performed and insuffi cient
control for potentially confounding variables. Exposure
of mice and rats to high doses of inorganic arsenic can
adversely affect spermatogenesis and can decrease tes-
ticular and accessory sex organ weights and serum lev-
els of LH, FSH, and testosterone (Pant
et al
., 2001; Sarkar
et al
., 2003). Long-term oral exposure of mice to sodium
arsenite in drinking water at 4 ppm arsenic for 365 days,
which is a dose level similar to human exposure through
drinking water, resulted in signifi cant accumulation of
arsenic in the mouse testis, epididymis, seminal vesicles,
and prostate gland, a decrease in the absolute and rela-
tive testicular weight but not of epididymal and accessory
sex organ weights, a decrease in sperm count and motility,
increase in abnormal sperm morphology, and changes in
the activities of testicular enzymes (Pant
et al.,
2004). Expo-
sure of mice to the same dose of sodium arsenite in the
drinking water (4 ppm arsenic) for only 35 days produced
no signifi cant effects (Pant
et al
., 2001).
mol/L. A study of male welders, whose
chromium levels in postshift spot urine samples ranged
from 0.17-4.74 nmol/mmol creatinine and those in blood
ranged from 6.0-46.4 nmol/L, showed no signifi cant dif-
ference in parameters of semen quality compared with
nonwelding workers (Bonde and Ernst, 1992). Another
study of male welders, whose blood chromium levels
were 131.0 ± 52.6
µ
g/L, showed signifi cantly decreased
sperm concentration (by 67%) in exposed workers com-
pared with controls and an inverse correlation between
sperm concentration and blood chromium levels in the
exposed workers (Dandevi
et al
., 2003).
Animal exposure to high doses of chromium (III
or VI) has been shown to adversely affect sperma-
togenesis. Chromium (VI) is considerably more toxic
(Ernst, 1990; Ernst and Bonde, 1992; Li
et al
., 2001) and
may involve oxidative stress. This is evidenced by
increased lipid peroxidation in the testes, decreased
sperm count, and increased abnormal sperm morphol-
ogy of mice exposed to chromium (VI), each of which
was partially preventable by the supplementation with
µ
3
FEMALE REPRODUCTIVE EFFECT
S
Effects of metals on female reproduction may arise
from their action on several stages beginning in fetal
life, during early development or maturity, and include
