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On the 30th anniversary of the U.S. Surgeon General's report Smoking and Health, we present updated results from one of the original cohort studies that comprised the groundbreaking document. A 26-year follow-up of 248,046 U.S. veterans evaluating the risks of cigarette smoking revealed strong dose-response effects between smoking and total cancer and a large number of cancer sites. Over 50% of cancer deaths among current smokers and 23% of cancer deaths among former smokers were attributable to cigarette smoking. These findings further demonstrate the large and unique role cigarette smoking plays in cancer etiology and the importance of smoking cessation to reduce this enormous public health burden.

The association between X-ray exposure in utero and childhood cancer was studied in a case-control study, nested in a national cohort of Swedish twin births. Records of the Swedish Twin Register for those born 1936-1967 (n = 83,316) were linked to the Swedish Cancer Register (1958-1983) and the Swedish Cause-of-Death Register (1952-1983). Ninety-five cases of childhood cancer before the age of 16 were identified. Two controls from the Twin Register were matched to each case by sex and year of birth. Maternal X-rays during pregnancy were documented for 41% of the cases and 36% of the controls. The crude relative risk of any childhood cancer associated with any prenatal X-ray was 1.2 (95% CI; 0.7-2.1). For the cases 64% of the X-rayed women had had abdominal X-rays, the numbers for the controls were 57%. Fifty-nine per cent of the X-rayed women had had abdominal X-rays, which were associated with a relative risk for all cancers of 1.4 (Cl; 0.8-2.5), leukemias 1.7 (Cl; 0.7-4.1) and tumors of the central nervous system 1.5 (Cl; 0.5-4.2). There was no apparent confounding by mother's age, drug use, obstetric complications, previous miscarriages, social class or length of pregnancy. The observed relative risks of cancer following prenatal X-ray exposure are consistent with previous studies, suggesting that the developing fetus may be more sensitive to the carcinogenic effects of ionizing radiation than are children irradiated post-natally.