Chromium

Chromium occurs in the environment primarily in two valence
states, trivalent chromium (Cr III) and hexavalent chromium (Cr
VI). Exposure may occur from natural or industrial sources of
chromium. Chromium III is much less toxic than chromium (VI).
The respiratory tract is also the major target organ for chromium
(III) toxicity, similar to chromium (VI). Chromium (III) is an
essential element in humans. The body can detoxify some amount
of chromium (VI) to chromium (III).
The respiratory tract is the major target organ for chromium (VI)
toxicity, for acute (short-term) and chronic (long-term)
inhalation exposures. Shortness of breath, coughing, and wheezing
were reported from a case of acute exposure to chromium (VI),
while perforations and ulcerations of the septum, bronchitis,
decreased pulmonary function, pneumonia, and other respiratory
effects have been noted from chronic exposure. Human studies
have clearly established that inhaled chromium (VI) is a human
carcinogen, resulting in an increased risk of lung cancer.
Animal studies have shown chromium (VI) to cause lung tumors via
inhalation exposure.