Update: cohort mortality study of workers highly exposed to polychlorinated biphenyls (PCBs) during the manufacture of electrical capacitors, 1940-1998

Table 3 Observed deaths and SMRs for selected causes of death^a, stratified by duration of employment^b

Cause of death	Duration of employment									Trend p-value^c
	< 5 years			5 – 9 years			≥10 years
	O	SMR	95% CI	O	SMR	95% CI	O	SMR	95% CI
All deaths	279	1.07	0.95 – 1.21	148	1.07	0.90 – 1.25	371	0.90	0.81 – 1.00	0.018
All cancers	73	1.08	0.84 – 1.35	41	1.06	0.76 – 1.44	104	0.95	0.78 – 1.15	0.38
MN of intestine, excluding rectum	7	1.16	0.47 – 2.39	6	1.69	0.62 – 3.67	14	1.30	0.71 – 2.17	0.97
Among women	7	1.94	0.78 – 4.00	6	2.46	0.90 – 5.36	11	1.66	0.83 – 2.97	0.61
MN of rectum	0			2	2.75	0.33 – 9.93	4	1.91	0.52 – 4.89	---
MN of biliary passages, liver and gall bladder	4	2.49	0.68 – 6.38	2	2.16	0.26 – 7.80	5	1.86	0.60 – 4.34	0.66
MN of breast	5	0.61	0.20 – 1.43	2	0.39	0.05 – 1.40	8	0.67	0.29 – 1.32	0.74
MN of prostate	1	0.64	0.02 – 3.55	0			6	1.58	0.58 – 3.44	---
Neoplasms of lymphatic and hematopoietic tissue	9	1.33	0.61 – 2.52	3	0.84	0.17 – 2.47	10	1.02	0.49 – 1.88	0.65
Non-Hodgkin's lymphoma^d	4	1.63	0.44 – 4.16	3	2.32	0.48 – 6.78	3	0.78	0.16 – 2.27	0.25
Myeloma^d	2	2.08	0.25 – 7.50	0			5	2.80	0.91 – 6.54	---
Other diseases of the nervous system and sense organs
Underlying cause of death	1	0.27	0.01 – 1.48	3	1.56	0.32 – 4.56	12	1.95	1.01–3.40	0.039
Multiple cause of death^d	6	0.51	0.19 – 1.10	4	0.65	0.18 – 1.66	28	1.37	0.91–1.98	0.011
Ischemic heart disease	69	1.22	0.95 – 1.54	47	1.44	1.06 – 1.91	108	0.97	0.80 – 1.18	0.057

Abbreviations: O: observed number of deaths; SMR: standardized mortality ratio; CI: confidence interval; MN: malignant neoplasm.
^a A priori causes of death with sufficient numbers to stratify plus significant new findings.
^b Person-years at risk and observed deaths among 2572 workers in jobs with potential for the highest, most direct exposure to PCBs began accruing in 1940.
^c Trend test performed for causes of death with 10 or more observed deaths.
^d Person-years at risk and observed deaths began accruing in 1960 for non-Hodgkin's lymphoma, myeloma, and multiple cause of death from other diseases of the nervous system and sense organs due to rate file restrictions.

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