Reasons why the idea that radiation exposures induce cancer needs to be revisited

Figures & data

Figure 1. (A) Tumor mortality starts to increase earlier in the exposed group. Thus, premature termination of the follow up shows nothing except an increase in the frequency which is a false interpretation. (B) Liver tumor incidence in male B6C3F1 mice sacrificed at 13 months of age (Takahashi et al. 1992). (C) Incidence of mammary neoplasms in rats at 11 months of age (Bond et al. 1960).

Figure 2. (A) Age-adjusted incidence of lung adenocarcinomas in female BALB/c mice (Ullrich and Storer 1979). (B) the first step of age adjustment is to increase the number of individuals at age A (upward arrow). (C) the second step is to multiply the adjusted number by the observed mortality rate, which is equal to the mortality of the control group, but the age was advanced by X days here.

Table 1. Age-adjusted tumor mortality in the exposed group when deaths occurred 100 days earlier than control.

	Control group		Irradiated group
Age stratum (days)	No. of tumor death (A)	No. of mice alive* (B)	No. of tumor death (C)	No. of mice alive* (D)	Proportion of tumor death(C/D)	Adjusted no. of mice* (B)	Adjusted no. of mice × Observed tumor mortality (B × C/D)
100–200	0	130	10	130	(10/130)	130	130 × (10/130) = 10
200–300	10	130	30	120	(30/120)	130	130 × (30/120) = 32.5
300–400	30	120	50	90	(50/90)	120	120 × (50/90) = 66.7
400–500	50	90	30	40	(30/40)	90	90 × (30/40) = 67.5
500–600	30	40	10	10	(10/10)	40	40 × (10/10) = 40
600–700	10	10	0	0	(0/0)	10	10 × (0/0) = 0
Total	130	520	130	390		520	216.7
	Overall proportion of tumor death 130/520 = 0.25		Overall proportion of tumor death 130/390 = 0.33				Age adjusted over all fraction of tumor death 216.7/520 = 0.42

*No. of mice that were alive on the first day of each observation window of 100 days.

Figure 3. (A) Neither an increased proportion in tumor deaths nor a decreased proportion of non-tumor deaths were observed following radiation exposures of up to 500 R (Storer 1965). (B) in the same study, life span was reduced in a dose dependent manner.

Figure 4. Proportion of fatal tumors (A) and incidence of tumors (B) in B6C3F1 mice that were exposed chronically to 8 Gy and observed until natural deaths (Tanaka et al. 2007). The two symbols connected by each line are the control group (left) and the exposed group (right). Open symbols indicate statistically significant cases when compared to the control values. In this study, the mean life span was shortened by about 100 days (Tanaka et al. 2003).

Figure 5. (A) Temporal changes in solid tumor mortality in mice after acute exposures to 1.9 Gy (Sasaki and Fukuda 2005; Nakamura 2023). B) Temporal changes in cancer mortality in A-bomb survivors who were exposed to 1 Gy at age 10 (Nakamura 2023). C) RR for solid tumor mortality in mice (Nakamura 2023).

Figure 6. Cancer mortality in A-bomb survivors who were exposed to radiation at the age of 10 (Nakamura 2023). The thick dotted line represents a control curve shifted toward younger ages which agreed closely with the epidemiological estimates (■). Because the two curves are essentially parallel, there would be no excess number of cancers in the exposed group if the risks are compared over the entire life span.

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