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ehp: Reflections on Hexavalent Chromium: Health Hazards of an Industrial Heavyweight
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Reflections on Hexavalent Chromium: Health Hazards of an Industrial Heavyweight
It's been 80 years since it was first noticed that workers in the
German chrome ore industry developed lung cancer more often than the
rest of the population. Study after study since the 1920s has shown
that people who work around industrial processes using chromium have
higher-than-normal rates of lung and nasal cancers. U.S. industry has
used chromium commercially for more than 100 years, and today chromium
is a primary contaminant at over half of all Superfund hazardous waste
sites. But despite a century of industrial use, there are still holes
in the basic knowledge about how chromium affects major organ systems
in animals and humans, as well as the risks associated with various
pathways of exposure.
Chromium occurs mainly in three forms. Metallic chromium (Cr[0]) is
a steel-gray solid with a high melting point that's used to make steel
and other alloys. Chromium metal does not occur naturally; it is
produced from chrome ore. Trivalent chromium (Cr[III]) occurs naturally
in rocks, soil, plants, animals, and volcanic emissions. This form is
believed by many to play a nutritional or pharmaceutical role in the
body, but its mechanism of action is unknown. Cr(III) is used
industrially as a brick lining for high-temperature industrial furnaces
and to make metals, metal alloys, and chemical compounds. Hexavalent
chromium (Cr[VI]) is produced industrially when Cr(III) is heated in
the presence of mineral bases and atmospheric oxygen (for instance,
during metal finishing processes). It is this third form of chromium
that has proven to be of the greatest occupational and environmental
health concern.
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