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Absorption - Inhalation Nickel (Ni)
Oral
Dermal
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Nickel and its inorganic
compounds can be absorbed from the respiratory tract. The quantity of Ni
absorbed is dependent on the quantity, physical and chemical properties
of the Ni compounds. Smaller particles (1-5 μm) enter the trachea and
bronchiolar region. The smallest particles (< 1 μm) enter the alveolar
region, where less intense airflow and system geometry enhance
sedimentation, diffusion, and electrostatic particle precipitation
(Czerczak
and Gromiec, 2001).
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Solubility is also an
important factor. Soluble Ni salts readily dissociate in aqueous medium
releasing Ni ions that can penetrate cellular membranes. The solubility
of Ni compounds appears to be the most reliable indicator of the rate
that Ni-containing dust in the alveoli is absorbed into the blood. This
rate is higher for soluble Ni salts, such as Ni chloride and sulfate,
and lower for less soluble species, such as Ni sulfide and forms
generally considered insoluble, such as the subsulfide, Ni oxide dusts
and metallic Ni. Nickel carbonyl is absorbed to a high degree; 26% of
the inhaled amount had been excreted in urine in 4 days
(Sunderman
and Selin, 1968). Since exhalation may have cleared the same
amount or more, at least 50% of the inhaled dose is estimated to have
been absorbed. A least 75% of intratracheally deposited Ni chloride was
absorbed within 72 hours in rats
(Clary, 1975)
whereas 80% of inhaled Ni oxide aerosol remained in hamster lung 10 days
later
(Wehner et al., 1972). There was evidence of Ni subsulfide,
but not Ni oxide, absorption. The half-lives of Ni in rat lung following
inhalation of Ni sulfate, Ni subsulfide and nickelous oxide were ~ 30
hours, 4 to 6 days and 120 days, respectively
(Hirano et al., 1994;
Czerczak and Gromiec, 2001). Ni solubility relates to its
carcinogenicity; insoluble forms are carcinogenic, soluble forms are
much less so or not.
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Nickel detected in the urine
of workers exposed to soluble Ni compounds (Ni chloride and Ni sulfate)
was higher than in workers exposed to insoluble species (Ni oxide, Ni
subsulfide), indicating soluble Ni species were more quickly absorbed
from the respiratory system
(Angerer and Lehnert, 1990;
Baranowska-Dutkiewicz et al., 1992).
Link to Absorption
Periodic Table
Link to Nickel (Ni) Index
Link to Database Index |