Manganese (IRIS) Integrated Risk Information System
Iris Risks
Among
the primary effects associated with Mn toxicity from inhalation
exposure in humans are signs and symptoms of CNS toxicity. The first
medical description of chronic Mn neurotoxicity (manganism) in
workers is generally credited to Couper in the 1830s (NAS, 1973).
Although the course and degree of Mn intoxication can vary greatly
among individuals, manganism is generally considered to consist of
two or three phases (Rodier, 1955). The first is the psychiatric
aspect, which includes disturbances such as excessive weeping and
laughing, sleep
disturbance, irritability, apathy, and anorexia. These symptoms can
occur independently of the second phase, neurological signs. The
latter may include gait disturbances, dysarthria, clumsiness, muscle
cramps, tremor, and mask-like facial expression. In addition, there
may be a final stage of Mn intoxication involving symptoms of
irreversible dystonia and hyperflexion of muscles that may not appear
until many years after the onset of exposure (Cotzias et al., 1968).
Cotzias et al. (1976) noted a parallel between these stages of
symptoms and the biphasic pattern of dopamine levels over time in the
Mn-exposed individuals noted above. Indeed, various specific features
of Mn toxicity show biphasic patterns in which there is generally
first an increase then a decrease in performance (e.g., a notable
increase in libido followed by impotence, or excitement followed by
somnolence) (Rodier, 1955).
Pg
25
Nogawa
et al. (1973) investigated an association between atmospheric Mn
levels and respiratory endpoints in junior high school students. A
questionnaire focusing on eye, nose, and throat symptoms and
pulmonary function tests were given to students attending junior high
schools that were 100 m (enrollment = 1258) and 7 km (enrollment =
648) from a ferromanganese plant. Approximately 97-99% of the
students participated. Based on measurements obtained at another time
by a government agency, the 5-day average atmospheric Mn level 300 m
from the plant was reported to be 0.0067 mg/cu.m.
Significant
increases in past history of pneumonia, eye problems, clogged nose,
nose colds, throat swelling and soreness, and other symptoms were
noted among the students in the school 100 m from the plant.
Those living closest to the plant reported more throat symptoms and
past history of pneumonia than did students living farther away.
Pulmonary function tests revealed statistically significant decreases
in maximum expiratory flow, forced vital capacity (FVC), forced
expiratory volume at 1 second (FEV-1), and the FVC:FEV- 1 ratio in
the students attending the school closer to the plant, with some
measures suggesting a relationship between performance and distance
of residence from the plant.
Evidence for
Human Carcinogenicity
__II.A.1.
Weight-of-Evidence Characterization
Classification
— D; not classifiable as to human carcinogenicity
Basis
— Existing studies are inadequate to assess the carcinogenicity of
manganese.
__II.A.2. Human
Carcinogenicity Data
None.
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