Lung cancer hormesis in high impact states where nuclear testing occurred

Background: Hormesis is a favorable biological response to low toxin exposure. In the case of radiation, large doses are carcinogenic, but low doses might be protective. In the current study, we analyzed lung cancer incidence in high-impact radiation states where nuclear testing occurred and compared it with lung cancer incidence in the remaining normal-impact radiation states and the District of Columbia.

Materials and methods: Lung cancer incidence data were from the American Cancer Society. Tobacco use 2012 data were from the Centers for Disease Control and Prevention. The distribution of states grouped according to lung cancer incidence interval was from the Centers for Disease Control and Prevention. Total background radiation measurements (terrestrial + cosmic + radon) were from Assessment of Variations in Radiation Exposure in the United States (2005). Data on high- and normal-impact states were from the National Radiation Exposure Screening & Education Program (RESEP). Congress passed the Radiation Exposure Compensation Act Amendments of 2000, creating RESEP, to help thousands of people diagnosed with cancer and other diseases caused by exposure to nuclear fallout or radioactive materials such as uranium. These people live in 12 high-impact states where nuclear testing had occurred. High-impact states were not designated according to measurements of background radiation.

Results: Lung cancer incidence is significantly lower in high-impact states in men (t = 5.4 for unequal variance; P < .001) and women (t = 3.0; P < .001). The clustering of the 12 high-impact states in the 2 lowest lung cancer incidence intervals (26.8-56.9 and 57.0-63.2) is statistically significant (P < .001, Fisher exact test, 2-tailed). Because cigarette smoking is ordinarily the most powerful risk factor for lung cancer, multivariate linear regression analysis of the effect of U.S. state group (normal-impact, high-impact, or extra high-impact for Nevada, Utah, and Arizona) on lung cancer incidence in men and women was performed. (In Nevada, Utah, and Arizona, men and women would have been downwind.) The U.S. state group impact was significant (P < .001 for men; P = .015 for women). The effect of percentage of smokers in the population was significant (P < .001 for men; P < .001 for women). The effect of total background radiation was significant (P = .029 for men; P < .029 for women); like the state group impact, more background radiation exposure was associated with less lung cancer.

Conclusion: Hormesis is still mired in controversy. Yet, it is of vital medical importance because of the continuing debate over whether the low-level radiation doses from diagnostic x-ray procedures, such as computed tomography scans, are harmful. Our analysis adds to the body of evidence suggesting that the linear no threshold model of radiation carcinogenicity in lung cancer might not be correct. Low-level radiation exposure might protect against lung cancer rather than cause it.