Chemistry Reference
In-Depth Information
controls (OR, 0.78; 95% CI, 0.55-1.1). At present, the
effects of chromium on female reproductive function
in humans remains unclear.
Reproductive effects have been observed in the off-
spring of mice exposed to chromium (III) after oral
maternal exposure. Signifi cant decreases in the relative
weights of reproductive tissues (ovaries and uterus)
were observed in the offspring of exposed BALB/c mice.
A signifi cant delay in timing of vaginal opening was
also noted (Al-Hamood
et al
., 1998). Cultured mouse
embryos were sensitive to chromium (VI) exposure
in
vitro
; incubation of blastocysts with potassium dichro-
mate inhibited edinner cell mass growth and differen-
tiation, whereas hatching, attachment, and trophoblast
outgrowth were not affected (Iijima
et al
., 1983).
Murthy
et al
. (1996) reported a number of reproduc-
tive effects (reduced number of follicles at different
stages of maturation, reduced number of ova/mice,
increased estrous cycle duration and histological
alterations) in the ovaries of female mice exposed to
potassium dichromate in drinking water for 20 days.
The severity of the reproductive effects seemed to be
dose related. Other experimental studies reported
increased preimplantation losses and resorptions
in rats and mice exposed to chromium (VI) (Kanojai
et al
., 1998; Trivedi
et al
., 1989). A decrease in the number
of pregnant females was observed after the mating of
unexposed females with male mice exposed to chro-
mium chloride, whereas an increase in relative ovarian
weight was observed in female mice exposed to potas-
sium dichromate. Impaired fertility was observed in
females exposed to chromium (III) mated with unex-
posed males. In females of different species fed with
potassium dichromate (VI), microscopic examination
of the ovaries revealed no treatment-related effects
(Elbetieha and Al-Hamood, 1997).
Additional studies were carried out in rats to assess
reproductive effects from exposure to potassium dichro-
mate in drinking water. At the highest level of exposure,
there were a decreased number of implantation sites,
number of live fetuses, and fetal weight. There were also
increases in the number of resorptions and the number
of preimplantation and postimplantation losses. There
was also a signifi cant reduction in ossifi cation of fetal
bones (Junaid
et al
., 1996a). In a second study (Kano-
jia
et al
., 1996), female rats were exposed to potassium
dichromate for 20 days before mating. Similar effects
were observed on gestational weight, postimplanta-
tion loss, number of live fetuses, and fetal ossifi cation
(in fetal caudal bones). In a third study, female rats
were exposed to potassium dichromate for 3 months
premating (Kanojia
et al
., 1998). Reduced maternal ges-
tational weight gain, increased preimplantation and
postimplantation loss, reduced fetal weight, fetal sub-
dermal hemorrhagic thoracic and abdominal patches,
and increased incidences of reduced ossifi cation in fetal
caudal bones were observed in all treatment groups. In
addition, the highest dose group exhibited increased
resorptions, reduced numbers of corpora lutea and
fetuses per litter, reduced implantations, reduced pla-
cental weight, and reduced fetal length. No treatment-
related gross visceral abnormalities were seen in these
studies.
3.6 Nickel
The effects of nickel exposure on female reproduc-
tive function remain unclear, and available informa-
tion is sparse in both human and experimental studies.
An investigation carried out in the arctic region of Rus-
sia, showed a spontaneous abortion rate of 15.9% in
356 women from a nickel refi ning plant compared with
8.5% in a control group of 352 females working in con-
struction industry. Exposure concentrations were 0.08-
0.196 mg Ni/m
3
, primarily as nickel sulfate, and nickel
concentrations in the urine ranged from 3.2-22.6
ยต
g/L
(Chashschin
et al
., 1994).
Nickel exposure is reported to affect early embry-
onic events in mice. Injection of nickel chloride on
the fi rst day of pregnancy led to decreased implanta-
tion frequency and reduced litter size, whereas the
administration on days 2-6 signifi cantly reduced litter
sizes but did not modify implantation.
In vitro
incuba-
tion inhibited growth of two-cell-stage embryos and
development to blastocysts (Storeng and Jonsen, 1980;
1981).
In more recent animal studies, no effect was dem-
onstrated on the length of the estrous cycle or micro-
scopic changes in the reproductive organs in mice or
rats exposed to air concentrations of nickel sulfate,
nickel oxide, or nickel subsulfi de, ranging from 3-
0.11 mg Ni/m
3
, respectively (NTP, 1996a,b,c). Fertility
was not adversely affected in female rats exposure to
nickel chloride in drinking water (Kakela
et al.,
1999).
Other studies on histological alterations in reproduc-
tive tissues of rats exposed to nickel or to nickel sul-
fate in drinking water failed to show relevant effects
(Obone
et al.,
1999).
3.7 Arsenic
The effect of arsenic on female reproductive function
has not been studied suffi ciently and is not clear. The
effect on human reproduction of arsenic was investi-
gated in females exposed by means of air or drinking
water. Tabacova
et al
. (1994) examined the relationship
between arsenic exposure from a copper smelter area
in Bulgaria and oxidative damage during pregnancy.
