Chromium metal and chromium(III) compounds are not usually
considered health hazards, but hexavalent chromium (chromium VI)
compounds can be toxic if orally ingested or inhaled. The lethal
dose of poisonous chromium (VI) compounds is about one half
teaspoon of material. Most chromium (VI) compounds are irritating
to eyes, skin and mucous membranes. Chronic exposure to chromium
(VI) compounds can cause permanent eye injury, unless properly
treated. Chromium(VI) is an established human carcinogen. Exposure
to the poisonous chemical hexavalent chromium in drinking water
formed the plot of the motion picture Erin Brockovich.
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Hexavalent chromium compounds are carcinogens. Chronic inhalation
of such compounds increases risk of lung cancer. Zinc chromate is
the strongest carcinogen of the chromates used in industry. Soluble
compounds, like chromic acid, are much weaker carcinogens.
from wikipedia
