Table 6. Associations of Selected Cancers with Exposure to Formaldehyde in Nested Case-control Analyses: Study of British Chemical Workers Exposed to Formaldehyde 1941-2012.

Cancer	Highest Level of Exposure	Cases	Controls	ORa	95% CI
Upper airways	Background	37	349
	Low/Moderate	33	384	0.84	0.49, 1.42
	High <1 year	25	204	1.28	0.61, 2.67
	High ≥1 year	20	201	1.03	0.48, 2.18
Cancer of the Larynx	Background	14	156
	Low/Moderate	17	177	1.20	0.53, 2.73
	High <1 year	14	104	2.02	0.65, 6.27
	High ≥1 year	8	93	1.30	0.39, 4.38
Cancer of the Mouth	Background	5	44
	Low/Moderate	3	44	0.59	0.12, 2.98
	High <1 year	3	30	0.97	0.13, 7.47
	High ≥1 year	3	22	1.38	0.17, 11.1
Cancer of the Pharynx	Background	10	89
	Low/Moderate	9	95	0.81	0.30, 2.22
	High <1 year	3	35	0.63	0.13, 3.03
	High ≥1 year	6	53	0.81	0.22, 3.05
Cancer of the Tongue	Background	5	34
	Low/Moderate	2	26	0.41	0.06, 2.58
	High <1 year	1	19	0.19	0.01, 2.58
	High ≥1 year	1	11	0.34	0.03, 4.35
All Leukaemia	Background	35	349
	Low/Moderate	39	350	1.08	0.64, 1.84
	High <1 year	9	87	0.84	0.32, 2.20
	High ≥1 year	9	128	0.59	0.23, 1.50
Myeloid leukaemia	Background	17	180
	Low/Moderate	19	186	1.10	0.51, 2.38
	High <1 year	5	34	1.77	0.45, 7.03
	High ≥1 year	4	50	0.96	0.24, 3.82

^aAll risk estimates are relative to background exposure, and relate to exposure status five years before the case (for controls, the matched case) was first known to have been diagnosed.

CI = confidence interval OR = odds ratio