Manganese - Toxicology of Metals - page 650

effect did not occur immediately but developed slowly
over the course of 4-8 months after the exposure.
Direct damage to the testes has not been reported in
humans occupationally exposed for longer periods.
Reported data reveal confl icting evidence for whether
occupational exposure to manganese causes adverse
reproductive effects. Noted effects may occur as a sec-
ondary result of neurotoxicity to manganese (ATSDR,
2000).

adverse cardiac effects were observed. In a case report
by Koizumi et al . (1979), ECG analysis of heart func-
tion suggested myocardial ischemia. The affected man
underwent hemodialysis after developing renal failure
from exposure to the fungicide. ECG analysis made
2 months later showed no abnormalities.

6.5.3 Hematological Effects

In subjects chronically exposed to high levels of
manganese in the workplace, as a rule, no signifi -
cant hematological effects had been observed. In a
study by Flinn et al . (1941), a low white cell count
was found in a number of workers affected by man-
ganese. Paterni (1954) claimed that small amounts of
manganese had a stimulatory effect on erythropoi-
esis. Similar fi ndings were also reported by Kesic
and Häusler (1954). From some fi ndings referring
to chronic manganese poisoning, it was presumed
that large amounts of manganese caused depres-
sion of both erythropoiesis and granulocyte forma-
tion (Cotzias, 1958; Rodier, 1955). Yiin et al . (1996)
observed increased erythrocyte superdioxide dis-
mutase and plasma malondialdehyde in men who
worked in manganese smelters.

6.5.2 Cardiovascular Effects

During an epidemiological study performed in fer-
roalloy workers, a decrease in systolic blood pressure
was found (Šaric and Hrustic, 1975). Arterial blood
pressure was measured and compared in three groups
of male workers aged 20-59 years at different exposure
levels to the airborne manganese. The lowest mean
values of the systolic blood pressure were found in
workers with the highest occupational exposure (0.39-
20.44 mg/m 3 ), although this group was comparatively
the oldest. The lowest mean diastolic pressure val-
ues were found in control workers. Age, body bulk,
and smoking habits, as factors, which might have
an impact on the obtained results, were considered.
Jiang et al . (1996b) studied the potential cardiotoxic-
ity of MnO 2 exposure in 656 workers (547 males and
109 females) engaged in manganese milling, smelt-
ing, and sintering. The geometric mean of manganese
in air was 0.13 mg/m 3 . Length of exposure varied
from 0-35 years. There was no increase of abnormal
electrocardiograms between manganese workers and
their matched controls. Arterial blood pressure values
showed a greater frequency of low diastolic pressure,
but this effect was highest in young workers with the
lowest tenure in the plant.
A manganese-induced decrease of blood pressure
was also noted in animal experiments by Schroeder
and Perry (1955) and Kostial et al . (1974).
In 1974, Kamiyama and Sacki carried out a study
on myocardial action potentials in the canine ventricle
and effects of manganese ions. The results showed that
Mn 2+ decreased the contractile tension of the muscle.
In 1978, Kimura et al . reported that dietary exposure
to 564 mg/kg of manganese in rats produced a sig-
nifi cant increase in the serotonin concentrations and
a decrease in blood pressure. The authors attributed
the fi nal marked decrease of blood pressure to the ele-
vated blood serotonin concentrations, most probably
released from different tissues.
There are three case reports concerning possi-
ble cardiac effects after acute exposure to fungicide
maneb without taking protective measures. In two
cases (De Carvalho et al ., 1989; Israeli et al ., 1983) no

6.5.4 Endocrine Effects

In a study by Alessio et al . (1989) performed in foun-
dry workers exposed to manganese levels of 0.04-
1.1 mg/m 3 (particulate matter) and 0.5-0.9 mg/m 3 as
fumes for approximately 10 years, elevated prolactin
(PRL) levels and cortisol levels were reported. No
changes in the levels of follicle-stimulating hormone
(FSH) and luteinizing hormone (LH) were noted.
Smargiassi and Mutti (1999) also reported an increase
of serum prolactin levels in a group of workers from
a ferroalloy plant. Measurements were made twice in
the same workers (in 1992 and 1997). Serum PRL levels
that were signifi cantly elevated in the earlier analysis
(1992) had also increased signifi cantly over the ear-
lier measurement in 1997. During the 5-year period
between studies, exposure levels were consistent.

6.5.5 Immunological Effects

In a study performed in male welders exposed to
manganese (0.29-0.64 mg/m 3 ) for an unspecifi ed dura-
tion, suppression of T and B lymphocytes characterized
by reductions in serum immunoglobulin G (IgG) and
total E-rosette-forming cells was observed (Boshna-
kova et al ., 1989). However, the welders in this study
were exposed to other compounds, including cobalt,
carbon dioxide, and nitric acid, as well as to noise
and vibration. Also, it is not known whether any of