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 5 Risk of lung cancer mortality among KNR workers with at least 15 years since first exposure by category of work, date of first exposure (for electrolysis & RSC departments) and duration of employment; ICNCM (1990) [3]

	Duration of employment
Category of Work	< 5 years			≥ 5 years				Total
	Obs	SMR		Obs	SMR		Obs	SMR
Electrolysis:¹
First exposure: 1946–1955	10	318	*	16	482	***	26	402	***
First exposure: 1956–1969	1	152		3	448		4	300
Electrolysis: Total	11	289	*	19	476	***	30	385	***
Roasting, Smelting and Calcining:²
First exposure: 1946–1955	5	211		7	298		12	254	**
First exposure: 1956–1969	1	139		1	128		2	133
RSC: Total	6	194		8	254	*	14	225	**
Other KNR Departments:³
Low level exposure⁴	1	73		5	267		6	187
Unexposed⁴	4	349		2	93		6	183
Other departments: Total⁵	5	250		18	275	**	23	283	**
Refinery: Total⁶	22	247	**	45	334	***	67	299	***

¹ From Table forty three, ICNCM (1990) [3]. ² From Table forty four, ICNCM (1990) [3]. ³ Labelled in previous KNR studies as 'other specified processes' and 'administrative, service and unspecified'. ⁴ From Table forty five, ICNCM (1990) [3]. ⁵ Calculated by equating time since first exposure in electrolysis or RSC departments with time since first employment in the refinery; and subtracting Electrolysis Total and RSC Total from Refinery Total. ⁶ From Table forty one, ICNCM (1990) [3]. * p < 0.05. ** p < 0.01. *** p < 0.001.