New views on the hypothesis of respiratory cancer risk from soluble nickel exposure; and reconsideration of this risk's historical sources in nickel refineries

Table 12 Conclusions on carcinogenic activity of 2-year inhalation studies of male and female F344/N rats and B6C3F₁ mice exposed to nickel subsulphide, nickel oxide and nickel sulphate hexahydrate [30–32]; and Wistar rats exposed to nickel metal powder [35]

		Evidence of carcinogenic activity
		F344/N rats		B6C3F ₁ mice
Nickel compound	Ni Solubility	Male	Female	Male	Female
Nickel subsulfide	Insoluble	Clear evidence	Clear evidence	No evidence	No evidence
Nickel oxide	Insoluble	Some evidence	Some evidence	No evidence	Equivocal evidence
Nickel sulfate hexahydrate	Soluble	No evidence	No evidence	No evidence	No evidence
		Wistar rats
Nickel metal powder	Insoluble	No evidence	No evidence	-	-