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Low-Dose Radiation Exposure |
I am honored to have the opportunity to learn more about the efforts of citizens and workers in Australia who are trying to ensure their own safety and the health of people living in their communities, and to protect those who will inherit the waste and contamination of this generations flirtation with nuclear technologies.
As I am talking, please feel free to stop me if you need me to clarify anything- or to ask me to speak up.
I am going to be talking about the effects of low level exposure to radiation.
In particular, I’ll talk about how the effects of low level radiation have been studied, and about reasons to question what most of use have been told repeatedly - that the effects of low level radiation are negligible.
I’ll say upfront that the radiation protection community has consistently understated the potential adverse effects of exposure to low level radiation. Few researchers have been forthright in acknowledging the limitations of what is understood about the effects of low level radiation. And, by downplaying the potential hazards of radiation exposure, researchers have acted more often in the interests of nuclear industry than in the interests of workers and the public who suffer these exposures.
To understand what is going on in the current debate about the health effects of exposure to low level radiation, it is helpful to look back to the history of the nuclear industry - as a way to learn about the people who have been studied (the research subjects) and about the people who have dose these studies (the researchers).
The United States’ initiated a large program of research into the health effects of exposure to low level radiation during the start of Manhattan Project, which was the US nuclear weapons program. By the end of World War II, the Manhattan project was costing $2.2 billion a year; this huge program came under the control of the Atomic Energy commission in 1946, and later the Department of Energy.
The AEC program of radiation research should give us reason to pause - and to question what we have been told about the effects of low level radiation. There has been a frightening lack of direction in research program and almost lackadaisical approach by the agency to studying the health effects of low level radiation. Within the AEC, researchers were largely exempt from external review. What this means is that unlike most health research - in which proposals for research projects are evaluated by an outside panel and competitively funded - within the AEC/DOE a group of scientists proceeded for decades without substantial outside evaluation or suggestions.
These problems can described succinctly by the reply in 1989, of the head of DOE’s epidemiology program to the question ‘what drives the DOE’s research agenda?’ His anwser was well, "it kind of drives itself really."
Another question that has been raised about the AEC/DOE resaerch program was the potential conflict of interest within the agency. The potential for conflict of interest was inevitable - the AEC and DOE were responsible for largescale environmental and occupational radiation exposures, and the agency was almost solely responsible for conducting research on the effects of these exposures.
For example, the AEC stalled, for decades, any study of the effects of radiation exposure among its workers. The directors of the AEC’s health research program decided that the disadvantages of such a study would include "insurance problems and labor relations" problems. Similarly, in describing the AEC research on nuclear fallout, the US Presidents advisory panel noted that, "By the mid-1960s the possibility that data gathering could only get the AEC into more trouble became an incentive to ‘not study at all.’"
Remember, it was researchers within these agencies who, historically, shaped the ‘expert opinion’ about the effects of radiation.
A traditional model of science is that prevailing opinions can be challenged, and opposing positions can be voiced and evaluated. The practice of censorship and restricting information is contrary to that model of science. However, for the last five decades the AEC/DOE determined what information would be available to scientific community by classifying and censoring documents. It is interesting to review their reasons for censoring information.
The AEC policy was to classify information as Confidential if, "while not endangering the National security, would be prejudicial to the interests or prestige of the Nation or any Governmental activity, or individual, or would cause administrative embarrassment."
Again, ‘while not endangering national security’ information was made Confidential if it was ‘prejudicial to the interests of any governmental individual’ or ‘cause for administrative embarrassment.’
The AEC also had its own Insurance Branch, which was involved in evaluating the AEC’s liability if specific documents were declassified. A memo from the AEC insurance branch to the Declassification Branch read, "We can see the possibility of a shattering effect on the morale of the employees if they became aware that there was substantial reason to question the standards of safety under which they are working." The memo continues, "We can also see the possibility that ... The results of this study might increase the number of claims of occupational injury due to radiation and place a powerful weapon in the hands of a plaintiff’s attorney."
Similar to the classification of research findings, scientific data collected by the AEC/DOE were almost universally restricted - so there could be no independent review of findings. This remains an important reason for concern about what we know about the effects of low level radiation. And, more importantly, restricting data to the hands of a few sanctioned individuals has been an obstacle to the progress of our understanding of low level radiation effects. The types of information which have been restricted included: data about atomic bomb survivors in Japan, information about exposures received by workers at government facilities, information about environmental releases of radionuclides in the US, and findings of laboratory and experimental research.
For people who suffered measurable doses of radiation on the job, it is important to recognize that concerns about production levels, and insurance liability influenced decisions, and even the information available, about work and environmental radiation exposure limits.
In 1964 the AEC finally did fund a study of workers. According to a DOE researcher the study was undertaken, "not to confirm or refute any important hypothesis but to permit a statement to the effect that a careful study of workers in the industry has disclosed no harmful effects of radiation." Such statements are remarkable to me because they read more like science as a public relations tool than as research conducted within an aggressive scientific program to protect the public’s health.
Earlier I noted that AEC health research was run by a relatively small group of scientists. But even among this small group of leading AEC/DOE scientists, there were dissenting opinions. Karl Z. Morgan, who directed the radiation protection program at the Oak Ridge National Laboratory, described the pressures on scientists for their opinions not to conflict with AEC goals: quote "there were times when some of my associates were demoted or lost their jobs because they refused to yield to pressures to lower our standards or compromise for unsafe conditions."
Drs. Alice Stewart and Thomas Mancuso conducted the AEC’s first major study of the health of workers at its nuclear facilities. After reporting a positive association between cancer deaths and low level exposure to ionizing radiation among workers at Hanford, the AEC terminated funding for their research. As some of you may know, Dr. Alice Stewart was already an important figure in radiation research - having demonstrated in the 1950s that extremely low levels of ionizing radiation exposure received by a fetus led to increased rates of childhood cancer.
Dr. John Gofman, who was head of the health research program at Lawrence Livermore National Laboratory, first had his work subject to AEC censorship and then had his funding cut after publicly questioning the assumption of a safe threshold for exposure to radiation.
Similarly, the director of epidemiology at Los Alamos National Laboratory - Dr. Greg Wilkinson - was pressed to censor his work and was then subject to demotion after he reported an association between radiation and cancer deaths among workers at the Rocky Flats nuclear facility. Wilkinson testified that he was "called to the Director’s office at Los Alamos and berated," and told that, "we should not be publishing to please peer reviewers, but rather we should be publishing to please the Department of Energy."
The largest research effort by the AEC was to fund a study of the survivors of the nuclear attack on Hiroshima and Nagasaki. In 1990, the head of DOE’s epidemiology program characterized the study as "the source of just about everything we know on the effects of ionizing radiation on humans." This study remains the basis for current risk estimates used to set environmental and occupational exposure limits: this is true in Australia just as it is in the United States.
Scientists outside the AEC repeatedly cautioned about the problems of a study of atomic bomb survivors, and argued that the AEC could better use the money for carefully designed research; nonetheless, this study has become the foundation of radiation protection standards.
Imagine the setting for this study: Atomic bombs are dropped on two cities. In Hiroshima, the infrastructure of the city was destroyed. There were no hospitals left standing, and only a handful of doctors survived to serve the tens of thousands of burned and injured residents. In the first year after the bombing over one hundred thousand people died. Five years after the bombing, the AEC formally started its study of cancer deaths among bomb survivors. Their assumption was that those who survived the attack were a normal population. Certainly, however, you can imagine the differences between those who lived and those who died from the atomic blast. People who were more feeble, more vulnerable, less fit, died. The very old and very young died in greater numbers. And yet today, we take this select group - the healthiest members of the Japanese population (since the less healthy were killed off), and study them as "the source of just about everything we know about the effects of ionizing radiation on humans."
A second issue raised by researchers since the very start of the project, is that we have very poor information about how much radiation these people were exposed to. We want to understand the risks associated with small increases in radiation exposure. To make accurate estimates of the increase in disease with exposure you need accurate estimates of how much exposure people received. No one in Hiroshima or Nagasaki was measured for radiation exposure; several years after the bombing, AEC officials canvassed the city and asked people to try and remember where they were when the bomb exploded. Based on their location, the AEC made rough estimates of peoples’ exposure - these estimates which don’t reflect the complex, and unknown factors which affected exposure: radiation from the bomb, for example was blocked by objects along path - a tree partially in front of you would reduce your exposure. Similarly, the areas around ground zero were radioactive in the days and weeks after bombing. So, for each individual, doses were affected by where they traveled, as well as by exposure from fallout.
The recent change in International recommendations for occupational radiation exposures (from 50 mSv year to 20 mSv) was a consequence of revisions in dose estimates for the A-bomb survivors. While the changes are a move in the right direction, questions about selection and exposure estimates continue to plague any study of survivors of an atomic bomb attack.
In recent years, been a shift in epidemiolgic research in the United States, which holds out the promise for positive change in both the public and scientific understanding of effects of radiation.
In 1989, the DOE was facing problems related to the loss of credibility of the agency’s health research program. In response to criticism, the Secretary of the DOE convened what was known as the SPEERA hearings - the secretarial panel for the evaluation of epidemiologic research activities. The SPEERA hearings were an attempt by the DOE to address many of the problems in their research program which I have reviewed. The panel included experts on radiation research, environmental health and law, who reviewed the DOE’s history of research on radiation health effects. At the hearings, researchers such as Dr. Alice Stewart and Dr. Gregg Wilkinson testified about their experience working for the DOE.
At the end of the hearings, the SPEERA panel concluded that the DOE research program ‘lacked central coordination, suffered from lack of peer review and competition for funding. The panel recommended that research on US nuclear workers be transferred from the DOE to the Department for Health and Human Services, where research projects would be opened up to independent scientists.
In 1991 congress’ office of technology assessment evaluated public health problems at DOE’s nuclear weapons facilities. The report reinforced the conclusions of the SPEERA panel. The evaluation of the Congressional Office was that the DOE’s program of research on the health effects of radiation suffered substantial problems which stemmed from the lack of peer review, and the DOE’s often complacent research program. In 1992, an independent panel of physicians and scientists reviewed the DOE research program, concluding that the "findings of DOE sponsored epidemiologic studies offer no firm basis for the repeatedly expressed official position that the health of workers and the public has been fully protected."
In 1995 a special panel was appointed by the President Clinton to review the DOE’s research on the effects of radiation which involved human experimentation; this panel revealed further information about the DOE’s history of suppression of information from the public and from the scientific community.
The consequence of these investigations, particularly the SPEERA hearings, was the decision that the DOE would turn over its data, as well as its funding, for epidemiologic studies of radiation health effects. My research into radiation health effects among workers at ORNL, and ongoing research into workers at Hanford Nuclear facility is part of this recent initiative to turn over responsibility for evaluation of these data to researchers not associated with the DOE.
The United States National Institute for Occupational Safety and Health, has taken charge of allocating funds for studies of workers, who received long term low level radiation exposure at US nuclear weapons facilities. These workers were employed by the US government to work on the atom bomb. At some of the facilities these workers had the advantage of being monitored for exposure.
The work I will talk about examined workers at Oak Ridge National Laboratory, which was a secret facility of the Manhattan project constructed in rural Tennessee. One of the world’s first nuclear reactors was built at ORNL; the facility has continued to be used since the 1940s for energy related research.
Our analyses examined 14,095 workers. Hired between 1943-1972, and followed until 1990.
Workers at Oak Ridge were individually monitored for exposure to external radiation, primarily by using film badges. Using government records we have been able to follow these workers to determine their causes of death.
So, in terms of epidemiologic research, we have a relatively good source of information about the long term effects of low level radiation exposure on workers death rates. We have a good idea of the differences in radiation exposure between people, and we have been able to follow workers for over forty years. You might contrast this information to the study of atomic bomb survivors, where there is no individual measurement of exposure and the study follows a select group of survivors after the attack.
As of 1990, of the 14,095 workers - - 3,269 had died. 879 of these deaths (26.9%) were due to cancer.
Using the workers film badge data, we examined the difference in cancer mortality rates among workers with different levels of radiation exposure. These estimates are described as the percent increase in cancer rates per 10 mSv radiation dose.
The current occupational exposure limits for Australian workers is no more than 50 mSv in any one year; and, a limit of 100 mSv for any 5 year period.
So, as we review findings for change in death rates per 10 mSv dose, remember that workers in Australia are permitted to receive 10-fold this dose every 5 years.
We compared cancer death rates among workers with different levels of cumulative radiation exposure.
Among the workers at ORNL, the effects of radiation ten years after the exposure, was a small increase in cancer death rates; 1.2% increase for every 10 mSv received on the job( se =0.46; change in dev=3.2).
Even more striking however was that exposures received at older ages, were very strongly associated with cancer mortality (se=1.48 , change in dev.=9.4).
In these graphs, you can see that with larger radiation doses, workers suffered higher rates of cancer mortality. On the left is a graph of the increase in cancer death rates with increasing lifetime cumulative dose. On the right is the increase in cancer death rates per unit dose received after age 45.
Given the uncertainties in epidemiologic studies, I would stress that while we can calculate precise estimates of the percent change in cancer mortality per unit dose, more generally the important observation is that among these workers there was increased cancer mortality following low level radiation exposures.
We investigated whether the increase in mortality with radiation was specific to cancer deaths. We divided up workers into those who died of cancer, and those who died of other causes. We found that the association between radiation and mortality is specific to cancer. That is, radiation was not associated with increases in deaths due to cardiovascular disease, infections, injuries etc. (in fact the association is slightly negative - which might suggest that in general the healthiest workers are selected to do jobs involving radiation exposure).
What you do see strongly, however, is that cancer deaths increase with increasing radiation exposure.
We considered whether the increase in cancer mortality among exposed workers could be due to a factor such as cigarette smoking. One way to investigate this question was to divide workers up by those who died of lung cancer and those who died of other cancers. Cigarette smoking would be expected to be very strongly associated with lung cancer, and much less associated with other cancers. However we found that radiation was strongly associated with both lung cancer and other cancers.
We have found that adult workers experience substantial measurable increases in cancer mortality following even low level exposure to external radiation; and that sensitivity to the effects of radiation increases as adults age. One explanation for changes, as we age, sensitivity to radiation is that as people age, their immune system slows down, and body is less able to repair the damage caused by radiation. The picture Dr. Stewart has described is that sensitivity to radiation, like sensitivity to most all forms of injury, is at its peak for the very youngest - fetuses and infants are the most vulnerable to radiation and other injuries - sensitivity declines after childhood and is lowest when we are young adults, and then progressively increases again as we age and our body’s ability to heal and repair itself declines. Radiation, it seems, is no exception to this general rule followed by most all causes of death and disease.
As I described at the start of this discussion: there are important reasons to be skeptical about the current radiation protection guidelines. The potential risks associated with radiation exposure tend to be understated by agencies and industries that have a lot to profit by having workers face hazards to their health; research often lacked independent review, or independent analysis; there are technical and methodological reasons to question findings from many of the studies on the effects of low level radiation - particularly studies of atomic bomb survivors; and, probably most troubling of all, radiation experts have seldom been forthcoming in acknowledging the limitations of their research and uncertainties about what we know.
Our ongoing research of the effects of radiation among DOE workers provides important evidence that low levels of radiation leads to increases in cancer mortality. Take these findings as a cautionary observation - substantial changes in mortality rates are seen among workers with low levels of exposure after a limited period of followup.
In conclusion, our findings challenge the claim that there are safe, or even negligible levels of radiation exposure. We have reported changes in mortality among otherwise health adult workers following low level radiation exposure. This is the most extreme effect of an exposure - that it kills you. This would be expected to be the tip of the iceberg; our study, like most every other study of workers or a-bomb survivors has not examined non-fatal effects of low level radiation - such as increases in cancer that don’t lead to death but do cause immense suffering. Nor do we know about the effects of radiation on human reproductive health. Dr. Stewart demonstrated that pregnant mothers are extremely sensitive to low levels of radiation, and studies with animals suggest that radiation exposure may lead to damage to offspring several generations down the line. But, information about risks of inherited problems following low level exposure remain minimal. The adult workers we studied, who experience changes in cancer rates following low level exposures, are likely to be some of the healthiest, most resiliant members of the population. We need to remember that the effects of exposures caused by an expansion of the nuclear industry will be experienced most dramatically by the weakest among us - infants, children, the elderly, the infirmed.
Finally, we have been talking about the effects of external radiation exposure, which passes through you like x-rays. However, in mines workers are also exposed to doses from internally deposited radionuclides - these exposures are not easily measured, not recorded on simple film badge like external radiation, and consequently research on the effects of internal exposures is even more questionable than research on external radiation exposure. Uranium miners should recognize that inhalation of radionuclides very different from external gamma, and the studies of exposures all suffer from the poor ability to measure workers exposures.
Copyright © Roxby Action Collective 1997