Chromium VI (Chromium Hexavalent, chromium VI ion, Cr6+) Cas No. 7440-47-3

Chromium VI

(Chromium Hexavalent, chromium VI ion, Cr6+)

Cas No. 7440-47-3

Potential sources and exposure

Hexavalent chromium rarely occurs naturally because it is readily reduced to

trivalent form in the presence of organic matter. Chromium (VI) is generally

produced by industrial processes. Chromium (III) and (VI) compounds are

produced by the chemical industry and are used for chrome plating, dye and

pigment manufacturing, leather tanning, wood preservatives, and cooling water

treatment. Chromium metal is found in asbestos and automotive catalytic

converters. Untreated wastewater discharges from electroplating, leather tanning,

and textile plants typically contain chromium. For the general population, the

common routes of exposure to chromium are inhalation and ingestion of drinking

water and food. The wearing down of asbestos brake linings and the exhaust

vapors from automobiles, incineration of municipal and sewage sludge, and

emissions from cooling towers that use chromium as rust inhibitors contribute to

the inhalation exposure pathway.

Physical and chemical properties

Property

Value

Molecular weight

52 g/mol

Toxicity

Unlike chromium III, chromium (VI) is not an essential element. Chronic oral

exposures to chromium (Vl) typically do not result in toxicity, since the

chromium is efficiently reduced to chromium (III) in the gastrointestinal tract.

Dermal exposure to chromium (VI) has been demonstrated to produce irritant

and allergic contact dermatitis (IRIS 1998). Primary irritant dermatitis is due to

the cytotoxic effect of chromium VI, while the allergic contact dermatitis is due

to a two-step cell-mediated immune response. In the first step, chromium is

absorbed and triggers an immune response called sensitization. In sensitized

individuals, subsequent exposures to threshold levels of chromium will result in

allergic contact dermatitis characterized by swelling, papules, redness, dryness,

scaling, and cracking of skin. Sensitization may lead to asthmatic attacks

following subsequent exposure.

Epidemiological studies have shown that workers employed in chromate

production facilities have increased incidences of lung cancer, nasal irritation,

atrophy, and nasal septum perforation as well as upper and lower respiratory

effects. Chromium-exposed workers are exposed to both the chromium (III) and

(VI) compound, but only chromium (VI) has been found to be carcinogenic

D25

Appendix D Toxicological Profiles