(Cr) Toxicity | ATSDR - CSEM - Agency for Toxic Substances and ...

Agency for Toxic Substances and Disease Registry Chromium Toxicity
Case Studies in Environmental Medicine (CSEM)
What Are the Routes of Exposure for Chromium?
Learning
Objectives
Upon completion of this section, you will be able to
• identify the routes of exposure to chromium.
Introduction The entry routes of chromium into the human body are inhalation, ingestion,
and dermal absorption. Occupational exposure generally occurs through
inhalation and dermal contact, whereas the general population is exposed
most often by ingestion through chromium content in soil, food, and water.
Inhalation After human exposure to Cr(III) by inhalation, urinary concentrations of
chromium were found to be increased indicating respiratory absorption
[Aitio, Jarvisalo et al. 1984; Foa, Riboldi et al. 1988; Dayan and Paine 2001].
Data from a few animal experiments indicate that with equal solubility,
Cr(VI) compounds are absorbed more readily than Cr(III) compounds,
probably because Cr(VI) readily penetrates cell membranes [Mertz 1969;
Wiegand, Ottenwalder et al. 1984].
Ingestion
Cr(VI) is reduced to Cr(III) in the lower respiratory tract by the
epithelial lining fluid and by pulmonary alveolar macrophages [Dayan
and Paine 2001]. One study showed that at equivalent numbers of cells,
the reducing efficiency of alveolar macrophages by biochemical
mechanisms was significantly greater in tobacco smokers than in
nonsmokers [Petrilli, Rossi et al. 1986].
In general, Cr(VI) compounds are better absorbed through the intestinal
mucosa than the Cr(III) compounds. However, due to the actions of stomach
acid and other components within the gastrointestinal tract, most of an
ingested Cr(VI) dosage is converted to Cr(III) [Cohen, Kargacin et al. 1993].
In humans and animals, less than 1% of inorganic Cr(III) and about 10% of
inorganic Cr(VI) are absorbed from the gut; the latter amount is slightly
higher in a fasting state [Donaldson and Barreras 1966; Dayan and Paine
2001].
Skin Data from volunteers and indirect evidence from occupational studies
indicate that absorption of Cr(VI) compounds can occur through intact skin
[Baranowska-Dutkiewicz 1981]. Studies in experimental animals showed
poor absorption of Cr(III) compounds following dermal route [Dayan and
Paine 2001].
Key Points
• Occupational exposure generally occurs through inhalation and dermal
contact, whereas the general population is exposed most often by
ingestion through chromium content in soil, food, and water.
• The majority of Cr(VI) that enters the body via inhalation or ingestion
is quickly reduced to Cr(III).
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