Chromium(V)-sialic (neuraminic) acid species are formed from mixtures of chromium(VI) and saliva.

The use of Cr(VI) compounds in leather tanning, pigment production and stainless steel welding can pose serious hazards to workers in these industries, since Cr(VI) is a documented human carcinogen.1 Epidemiological studies have shown that occupational exposure to Cr(VI) increases the risk of workers developing cancer of the lung and the sinonasal cavity and many countries limit both water soluble and insoluble Cr concentrations in the workplace.2 The primary pathways for human uptake of Cr(VI) are inhalation, ingestion, and skin permeation; inhalation of Cr can cause irritation of the nasal mucosa, nasal ulcers, perforation of the nasal septum, and cancer.2 While the exact mechanisms of Cr(VI)-induced carcinogenicity are not fully understood, there is strong evidence that Cr(V) species, produced from the intracellular reduction of water-soluble (cell-permeable) or insoluble (phagocytosed) Cr(VI) complexes, play a role in damage to DNA and other biomolecules that could initiate cancer if left unrepaired.3