Committee Examining Radiation Risks of Internal Emitters
(CERRIE)
________________________________________________________________________
7th Meeting, December 11, 2002 INFO 7B
Local Meeting Room 4 ABC
Eland House
Bressenden Place
London SW1E 5DU
Low dose rate radiation increases longevity in humans:
Paper by J Cameron
1. Attached for the Committee’s information is a copy of a paper by J Cameron on hormetic
effects of low dose/low dose rate radiation.
IF Nov 19
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INFO Paper for CERRIE November 2002
Low dose rate radiation increases longevity in humans
by John R. Cameron
Introduction
1. Low dose rate radiation has long been assumed to have no health benefits despite excellent
contrary evidence at background dose levels. It has been known since 1973 (Frigerio et al) that the
six U.S. states with the highest levels of background radiation had cancer mortality rates 15% lower
than the cancer mortality for all 48 states. Jagger (1998) showed that the cancer death rate in three
U.S. mountain states was 25% lower than that of three U.S. Gulf States even though the background
in the mountain states is about three times greater than in the Gulf States.
2. This article presents data from two excellent epidemiological studies of radiation workers that
show significant increases in longevity. These studies are consistent with the hypothesis that
moderate dose rates stimulate the immune system and significantly increase longevity. The increased
longevity is due primarily to reduction of deaths from non-cancer although one study demonstrated a
significant reduction in cancer deaths as well. The data do not contradict the well-documented fact
that high doses increase risk of cancer.
3. There is very likely an optimum dose rate of radiation for good health, just as there are optimum
levels for essential trace elements and vitamins in our diet. I believe that most people are suffering
from radiation deficiency and that the recommended annual dose (RAD) of radiation will be
significantly higher than the annual dose most humans receive from background.
4. Because of the current belief that even the smallest radiation dose increases the risk of cancer, it
is considered unethical to do a double blind human radiation study, even at background levels. The
reduced cancer in areas of high background plus the results of the two studies described below are
evidence that it is ethical and desirable to do a double blind human radiation study of senior citizens
in the Gulf States at dose rates comparable to those found in the U.S. mountain states (Cameron
2001). Such research is urgently needed to determine the health effects of low dose rate radiation.
Epidemiological evidence
5. The 100-year study of British radiologists (Berrington et al 2001) is perhaps the most important
article about health effects of radiation on humans ever published. The continuity of follow-up in the
study is the longest for any study of exposure to chronic radiation. The dose range over the 100-year
study period from 1897-1997 is very large. Exposures before 1920 were estimated to be over 100
cSv/y (100 R/y).
6. The British radiologists study gave the standard mortality ratio (SMR) for deaths from all causes,
all cancers and all non-cancers of British radiologists compared to the SMR of three groups: (i) all
men in England and Wales, (ii) all social class I males and (iii) all male medical practitioners.
Radiologists were divided into four groups depending on when they joined one of the two British
radiological societies: 1897-1920; 1921-1935; 1936-1954 and 1955-1979. The British X-ray safety
committee, formed in 1920, played an important role in reducing occupational doses to radiologists
in later decades.
7. Early British radiologists (1897-1920) had a SMR for cancer 75% higher than the SMR for
cancer of all male English physicians. The increased cancer mortality was clearly a result of their
large radiation dose. However, even these heavily exposed pre-1921 radiologists had a SMR for non-
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cancer 14% lower (p < 0.05) than the SMR for non-cancer of all male medical practitioners. Since
80% of the radiologists died from non-cancer causes, the decreased SMR for non-cancer completely
canceled their 75% excess cancer mortality. In other words even the earliest radiologists did not
suffer any loss in longevity due to their large exposures. Their radiation risk netted to zero.
8. British radiologists' exposures were reduced starting in 1920 due to the activities of the British x-
ray safety committee. After 1920, radiologists' overall health improved. Considered as a group, all
radiologists registered after 1920 (1921-1979) showed no significant difference in cancer SMR
compared to other physicians. However, these radiologists had a significantly lower cancer SMR
than all English men (SMR = 0.63, p < 0.001) or their social class I peers (SMR = 0.82, p < 0.01). In
addition, the post-1920 radiologists had a lower SMR for deaths from all causes than other male
physicians (SMR =0.91, p < 0.01), social class I males (SMR = 0.91, p < 0.01), or all men in
England (SMR = 0.72, p < 0.001).
9. Cancer rates among radiologists dropped significantly below those for all English men starting in
1936 (SMR for 1936-1954 = 0.66, p < 0.001). This was at a time when the only dose limit in effect
was the "tolerance dose" of 0.2 R/day (approximately 35 cGy/y) - much higher than present
recommended limits.The most dramatic health results are seen in radiologists registered after 1955.
They experienced a SMR for non-cancer deaths 36% lower (p < 0.001) than that of other male
English physicians. Their SMR for deaths from all causes was 32% lower (p < 0.001) than that of all
English physicians. This is equivalent to an increase of longevity of over three years-a highly
significant beneficial effect at a moderate occupational dose rate. The dose rates were considerably
higher than the background dose in most of the world, as occupational exposure limits for most of
this period were 5 cSv/y, although the doses received by the radiologists are not known.
10. For the entire 100-year evaluation period, radiologists never had an elevated all-cause mortality
rate compared to male physicians, or the other two comparison groups. All radiologists registered
from 1897 to 1979 had a non-cancer SMR 14% lower (p < 0.001) than that of other physicians, while
their SMR for all causes was 8% lower (p < 0.01) than that of their male medical colleagues. During
no time period was the mortality rate of radiologists from all causes higher than that of their medical
colleagues. The radiologists' all-cause mortality rates decreased significantly below those of all male
physicians after 1955. This supports the hypothesis that the improved health of post-1955
radiologists was due to radiation stimulation to the immune system.
11. The concluding sentence of the Berrington et al article omits any mention of health benefits. It
states: "For non-cancer causes of death there was no evidence of an increased risk in any group, even
among those registering before 1921." This statement neglects to mention the significantly decreased
SMR for non-cancer deaths of radiologists compared to other English male medical practitioners.
This oversight by the authors was pointed out in Cameron (2002).
12. The nuclear shipyard worker study (NSWS), supported by the U.S. Department of Energy (DOE)
from 1980-1988, compared the health of 28,000 nuclear shipyard workers with the greatest
cumulative doses to the health of 32,500 unexposed shipyard workers with the same ages and same
jobs. The DOE contract with Johns Hopkins University provided that the NSWS must have a
Technical Advisory Panel of 8 outside scientists to review the progress of the research twice a year. I
was a member of this Panel. The purpose of the research was to show radiation risks. The final report
of the NSWS (Matanoski 1991) makes clear that there was no radiation risk to the nuclear workers'
health. The written portion of the final report does not mention that the cancer death rate of the
nuclear workers was about 15% lower than the unexposed controls (p < 0.01) or that the death rate
from all causes of the nuclear workers was 24% less than that of the unexposed controls (p < 10-16 ).
This lower death rate from all causes results in an increase in longevity of nearly three years.
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13. This important finding from the NSWS supports the hypothesis that a moderate dose rate of
radiation stimulates the immune system. If the study aim had been to look for health benefits of
ionizing radiation, it would have been a huge success. As a study to find radiation risks, it was an
abysmal failure. This may explain why details of the NSWS have yet to be published. I published a
brief summary of the results shortly after the final report was submitted (Cameron 1992).
Conclusions
14. It appears that the recommended limit for radiation workers set in 1934 did not need to be
lowered. Lauriston Taylor, one of the founders of the ICRP in 1928 and the founder of the NCRP in
1929, wrote "No one has been identifiably injured by radiation while working within the first
numerical standards set first by the NCRP and then the ICRP in 1934. Š. The theories about people
being injured have still not led to the demonstration of injury and, if considered as facts by some,
must only be looked upon as figments of the imagination." (Taylor 1980). The present very low
recommended dose limit for radiation workers (2 cSv/y) is not based on any human data. The present
limit is so low that it probably is reducing health benefits seen in post-1935 radiologists and in the
shipyard workers who worked from the mid-1950s through 1980.
15. Neither the British radiologists study nor the NSWS will resolve the controversy concerning the
validity of the linear non-threshold (LNT) model of radiation risk, but both studies cast doubt on the
unwritten assumption that low levels of radiation have no beneficial effect on humans. The nuclear
shipyard worker study and the British radiologists data show with good statistical strength that
moderate dose rates of radiation are beneficial to the health. The reduced mortality from all causes
among exposed workers, compared to occupationally similar control groups, shown in both of these
studies contradict the present radiation protection dogma that radiation is a risk down to the lowest
doses. In view of the results of these two studies it is appropriate for the ICRP and NCRP to
reconsider their decision to base radiation risk on the linear no-threshold (LNT) model. Both studies
give evidence that humans probably need more radiation for good health than is provided by natural
background in most areas of the world. There may be such a thing as radiation deficiency (Cameron
2001). The optimal dose rate for the general population may be similar to that received
occupationally by post-1955 radiologists and by nuclear shipyard workers. Because of the increased
longevity seen among the British radiologists and the U.S. shipyard workers, and the reduced cancer
mortality in high background areas it would be ethical to conduct a double blind radiation study on
humans to resolve the important issue of health effects of low dose rate radiation as suggested in
Cameron (2001).
References
1. Berrington, A, Darby, SC, Weiss, HA, Doll, R. 100 years of observation on British radiologists:
mortality from cancer and other causes 1897-1997. Br J Radiol 74, 507-519 (2001).
2. Cameron, JR. The Good News About Low Level Radiation Exposure Health Physics Society
Newsletter 1992 Feb pp. 9-11
3. Cameron, J.R. Is radiation an essential trace energy? Physics and Society October 2001 http://
www.aps.org/units/fps/oct01/a5oct01.html
4. Cameron, JR. Radiation increased the longevity of British radiologists Br J Radiol 2002;75:637-8.
5. Frigerio, N.A., Eckerman, K.F. and Stowe, R.S. (1973) Carcinogenic Hazard from Low-Level,
Low-Rate Radiation, Part I, Rep. ANL/ES-26. Argonne Nat. Lab
6. Jagger, J. (1998) Natural Background Radiation and Cancer Death in Rocky Mountain and Gulf
Coast States Health Physics Oct. pp 428-434
7. Matanoski, GM. Health effects of low-level radiation in shipyard workers final report. 471 pages
Baltimore, MD, DOE DE-AC02-79 EV10095, (1991).
8. Taylor, LS. Some non-scientific influences on radiation protection standards and practice Health
Physics 32, 851-874 (1980).
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