2. PRODUCTION AND USE
2. PRODUCTION AND USE
Apart from unusual sources,
such as massive nickel in meteorites, nickel from natural sources is
usually found at modest concentrations and occurs in conjunction with a
wide variety of other metals and non-metals. Although nickel is a
ubiquitous metal in the natural environment, industrialization has
resulted in increased concentrations of nickel in both rural and urban
environments.
Nickel-bearing particles are
present in the atmosphere as constituents of suspended particulate
matter and, occasionally, of mist aerosols. The primary anthropogenic
stationary source categories that emit nickel into ambient air are: (1)
combustion and incineration sources (heavy residual oil and coal
burning units in utility, industrial, and residential use sectors, and
municipal and sewage sludge incinerators), (2) high temperature
metallurgical operations (steel and nickel alloy manufacturing,
secondary metals smelting, and co-product nickel recovery), (3) primary
production operations (mining, milling, smelting, and refining), and
(4) chemical and catalyst sources (nickel chemical manufacturing,
electroplating, nickel-cadmium battery manufacturing, and catalyst
production, use, and reclamation). Typical ambient air concentrations
of nickel range from 6 to 25 ng Ni/m3 (Tsalev and Zapriano, 1984; Sunderman, 1988).
In aquatic systems, such as in ambient or drinking water, nickel is usually present as the nickel cation (Ni2+), together with other anions such as hydroxyl (OH-), sulfate (SO42-), chloride (Cl-), carbonate (CO32-), or nitrate (NO3-).
Sources of nickel in ambient waters include chemical and physical
degradation of rocks and soils, deposition of atmospheric
nickel-containing particulate matter, and discharges from industrial
processes. In unpolluted water supplies, a range of 1 to 50 µg Ni/l has
been reported (Stoeppler, 1980). Nickel levels in soil vary between 5
and 500 µg Ni/g depending on geological factors.
For purposes of this
document, however, the main concern is nickel presence in occupational
settings. It is evident that industrial processes present potential for
exposure of workers to higher concentrations of nickel and/or its
compounds than those generally found in the natural environment.
Occasionally, these exposures may be to a refined form of nickel, but
usually they are mixed, containing several nickel compounds and/or
contaminants. These "mixed exposures" often complicate the
interpretation of health effects of specific nickel species.