Issues of methods and interpretation in the National Cancer Institute formaldehyde cohort study

Table 3 Rate ratios and numbers of deaths for NPC by NCI update and FA exposure metric ^f

NCI update	RR 95% CI	No. deaths	RR 95% CI	No. deaths	RR 95% CI	No. deaths	RR 95% CI	No. deaths	p-value trend^d.	p-value trend^e.
Peak exposure (ppm)
	0		> 0 - < 2.0		2.0 - < 4.0		4.0
NCI 1994 update^a.	1.00 Baseline	2	NA	0	NA	0	1.83	7	0.044	<0.001
NCI 1994 update (corrected)^b.	1.00 Baseline	2	NA	0	NA	0	1.82 0.32-10.46	7	<0.001	0.05
NCI 2004 update^c.	4.39 0.36-54.05	2	1.00 Baseline	1	NA	0	7.66 0.94-62.34	7	0.005	0.10
Average intensity of exposure (ppm)
	0		0.1-0.4		0.5-0.9		≥ 1.0
NCI 1994 update^a.	1.00 Baseline	2	NA	0	1.38	1	1.67	6	0.126	0.066
NCI 1994 update (corrected)^b.	1.00 Baseline	2	NA	0	0.37 0.03-4.63	1	1.66 0.29-9.48	6	0.07	0.14
NCI 2004 update^c.	6.79 0.55-83.64	2	1.00 Baseline	1	2.44 0.15-39.07	1	11.54* 1.38-96.81	6	0.09	0.16
Cumulative exposure (ppm-years)
	0		> 0 - < 1.5		1.5 - < 5.5		≥ 5.5
NCI 1994 update^a.	2.40	2	1.00 Baseline	3	1.19	1	4.14	3	0.029	0.025
NCI 1994 update (corrected)^b.	2.41 0.35-16.70	2	1.00 Baseline	3	1.20 0.12-11.56	1	4.15 0.83-20.78	3	0.04	0.05
NCI 2004 update^c.	1.87 0.30-11.67	2	1.00 Baseline	4	0.86 0.10-7.70	1	2.94 0.65-13.28	3	0.06	0.07

^a.Hauptmann et al.[3].
^b.Beane-Freeman et al.[8].
^c.Beane-Freeman et al.[6].
^d.Two-sided likelihood ratio test (1df) of zero slope for continuous formaldehyde exposure among exposed person-years only.
^e.Two-sided likelihood ratio test (1df) of zero slope for continuous formaldehyde exposure among unexposed and exposed person-years.
^f.All FA exposure metrics calculated using 15-year time lag.
*95% CI does not include 1.00.

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