Table 4

Hazard ratio estimates of nasopharyngeal carcinoma in relation to the duration of occupational exposures classified by job exposure matrix

Exposure	Cases	Non-cases	HR*	95% CI	p for trend
*Adjusted for age at baseline only.
Cotton dust
Never	19	1232	1.0	Reference
<10 years	12	292	2.7	(1.3 to 5.7)
⩾10 years	36	1663	1.6	(0.9 to 2.9)	0.33
Wool dust
Never	61	2737	1.0	Reference
<10 years	1	94	0.5	(0.1 to 3.8)
⩾10 years	5	356	0.7	(0.3 to 1.7)	0.29
Synthetic fibre dust
Never	42	1922	1.0	Reference
<10 years	6	238	1.1	(0.5 to 2.6)
⩾10 years	19	1027	0.8	(0.5 to 1.4)	0.52
Solvents
Never	52	2729	1.0	Reference
<10 years	6	169	1.5	(0.6 to 3.6)
⩾10 years	9	289	1.4	(0.7 to 2.8)	0.30
Bleaching agents
Never	64	3141	1.0	Reference
<10 years	1	16	2.0	(0.3 to 15.7)
⩾10 years	2	30	2.6	(0.6 to 11.4)	0.20
Acids, bases, and caustics
Never	55	2924	1.0	Reference
<10 years	4	90	1.7	(0.6, 5.0)
⩾10 years	8	173	2.1	(1.0, 4.6)	0.05
Dyes
Never	62	3091	1.0	Reference
<10 years	3	30	3.3	(1.0 to 11.5)
⩾10 years	2	66	1.3	(0.3, 5.6)	0.32
Inks
Never	63	3158	1.0	Reference
<10 years	2	7	14.0	(2.6 to 74.0)
⩾10 years	2	22	3.0	(0.7 to 14.0)	0.05
Endotoxin
Never	41	2303	1.0	Reference
<10 years	5	170	1.6	(0.6 to 4.1)
⩾10 years	21	714	1.7	(1.0 to 2.9)	0.05