Table 5.

Human, animal bioassay and in vitro investigations characterizing the carcinogenicity of Cr (VI).

Study Type	Ref.	Exposure	Cell Type or Animal Model	Results
Human	(Koh et al., 2011)	inhalation	____	Workers exposed to Cr (VI)-containing cement dust had increased incidence of stomach cancer.
Human	(Halasova et al., 2009)	inhalation	____	Cr (VI) exposed workers developed lung cancer at an early age and have a higher incidence of small cell lung carcinoma than unexposed lung cancer patients.
Human	(Birk et al., 2006)	inhalation	____	Cr (VI) exposed workers with chromium urine levels of > 200 μg/l had an increased lung cancer risk.
Human	(Linos et al., 2011)	oral (drinking-water)	_____	Subjects orally exposed to Cr (VI) displayed elevated cancer mortality. The exposed population experienced high standard mortality rates for liver, lung, and kidney cancers.
Animal Bioassay	(Stout et al., 2009)	oral (drinking-water)	F344/N rats and B6C3F1 mice	Rats exposed to 516 mg/l SDD for 2 years developed oral neoplasms. Mice exposed to 257 mg/l SDD for 2years developed small intestinal neoplasms.
Animal Bioassay	(Davidson et al., 2004)	oral (drinking-water)	CRL: SK1-hrBR hairless mice	Mice co-exposed to potassium chromate (2.5 and 5 mg/l) and UV formed more skin tumors than mice exposed to either potassium chromate alone or UV alone.
In Vitro	(Sun et al., 2011)	chemical injected in media	human bronchial epithelial cells (BEAS-2b)	Cr (VI) transformed cells displayed altered gene expressions of cancer-related genes such as desmocollins, cyclin D1, and TGFβ2.
In Vitro	(Kim A. Biedermann, 1987)	chemical injected in media	human fibroblasts	Cr (VI) compounds induce a mutation that confers resistance to 6-thioguanine and causes anchorage independent growth.