Table 4

Risk of cancer of the larynx and hypopharynx, associated with occupational exposure to formaldehyde and coal dust after excluding subjects with a probability of exposure <10%

		Larynx			Hypopharynx
		Cases/ controls	Adjusted OR		95% CI	Cases/ controls	Adjusted OR	95% CI
Formaldehyde:
Never exposed	194/211	1.00	—	118/211	1.00	—
Ever exposed	44/35	1.17	0.63–2.17	41/35	1.74	0.91–3.34
Duration of exposure (y):
⩽7	15/7	1.68	0.60–4.72	6/7	0.74	0.20–2.68
7–20	14/12	0.86	0.33–2.24	19/12	1.65	0.67–4.08
>20	15/16	1.14	0.47–2.74	16/16	2.70	1.08–6.73
Cumulative level:
Low	4/2	0.68	0.12–3.90	3/2	0.78	0.11–5.45
Medium	17/11	1.86	0.76–4.55	13/11	1.77	0.65–4.78
High	23/22	0.91	0.42–1.99	25/22	1.92	0.86–4.32
Coal dust:
Never exposed	254/270	1.00	—	163/270	1.00	—
Ever exposed	27/16	1.70	0.80–3.59	23/16	2.71	1.18–6.23
Duration of exposure (y):
<6	8/3	2.25	0.53–9.51	6/3	3.45	0.77–15.5
6–20	6/4	1.28	0.28–5.38	7/4	1.34	0.29–6.06
>20	13/9	1.65	0.61–4.48	10/9	3.31	1.05–10.3
Cumulative level:
Low	1/0	—	—	0/0	—	—
Medium	11/7	1.51	0.52–4.44	9/7	2.07	0.66–6.55
High	15/9	1.78	0.66–4.82	14/9	3.44	1.13–10.4

4-150 For each substance, adjustments used in table 3 were kept in the present analysis.