Statement to the Subcommittee on Energy and Environment of the Committee on
 Science, United States House of Representatives, July 18, 2000

 Steve Wing, Associate Professor, Department of Epidemiology, School of
 Public Health, University of North Carolina>
 Mr. Chairman and Members of the Committee, thank you for inviting me to
 testify about health effects of low level radiation. I am an epidemiologist
 on the faculty at the University of North Carolina where I have studied
 radiation health effects among workers at Oak Ridge, Los Alamos, Hanford and
 Savannah River under funding from the Departments of Energy and Health and
 Human Services. Epidemiology, the study of disease in human populations, is
 especially important in risk estimation and standard setting because animal
 and laboratory studies necessitate extrapolation from high to low doses,
 from molecules and cells to organisms, and from other species to humans
 (1-3).

 We know that ionizing radiation can cause cancer and inherited mutations by
 damaging DNA. Although epidemiologists have studied populations exposed to
 both high and low levels of radiation, extrapolation of risks from high to
 low doses has led to a debate over whether a straight line extrapolation, the
 linear no-threshold model, is appropriate. My testimony will make three
 points: current cancer risk estimates are too low by a factor of ten or more;
 current standards do not adequately protect workers and the public; and, a
 large and
 growing body of scientific evidence shows that there is no basis for further
 relaxation of radiation protection standards.

 Extrapolation from high dose studies: High dose studies examine special
 populations including patients receiving
 radiation treatments. By far the most influential are studies of survivors
 of the bombings of Hiroshima and Nagasaki that are currently the primary
 basis for cancer risk estimates. However, the A-bomb studies are flawed due
 to selective survival, poor dose measurement and confounding exposures (4-7).

 The atomic bombings produced massive immediate casualties as well as delayed
 deaths due to lingering effects of radiation, infectious epidemics, and the
 destruction of food, housing, and medical services (8). Only the
 healthiest survived these conditions, especially among those who are most
 vulnerable, the young and the old. By 1950, when a list of survivors was
 assembled for long-term study, persons most susceptible to radiation had
 already died. The healthy survivor effect leads to underestimation of risks,
 particularly for exposures in utero, during childhood, and at older adult
 ages (6).

 Detection of radiation risks depends upon the ability of an epidemiological
 study to classify persons according to their exposure levels. A-bomb
 survivors were not wearing radiation badges, therefore their exposures had to
 be
 estimated by asking survivors about their locations and shielding at the time
 of detonation. In addition to the typical types of recall bias that occur
 in surveys, stigmatization of survivors made some reluctant to admit their
 proximity (9). Acute radiation injuries such as hair loss and burns among
 survivors who reported they were at great distances from the blasts (10, 11)
 suggests the magnitude of these errors, which would lead to under
 estimation of radiation risks.

 Another bias occurs because of the higher exposures of distant survivors to
 residual radiation. Fallout affected distant survivors in both cities (8,
 12). In addition, survivors who were shielded or exposed at greater distances

 were strong enough to enter the areas near the hypocenters of the blasts
 within hours of detonation, exposing themselves to residual radiation created
 by the atomic weapons (8, 12-14). Residual radiation exposures of lower dose
 survivors leads to an underestimate of radiation risks.

 Direct observation from low dose studies: In 1956 Dr. Alice Stewart and
 colleagues reported in The Lancet that fetal exposures during obstetric x-ray
 examinations are associated with elevated childhood cancer rates (15). The
 fetus is especially sensitive to radiation due to rapid cell division.
 Stewart's findings have been replicated in
 numerous other low dose studies (6, 16-18), and standards for medical
 practice now dictate that small doses of radiation associated with a single
 x-ray should be avoided during pregnancy.

 Long-term studies of cancer among nuclear workers began to appear in the
 1970s when Mancuso, Stewart and Kneale reported that small doses of radiation
 received at older ages raised cancer rates among workers at the plutonium
 production facility in Hanford, Washington (19). Manhattan Project
 scientists realized in the early 1940s that workers in the weapons plants
 faced special hazards, and they created a unique resource for health studies
 at some facilities by issuing each employee a radiation monitor that was
 incorporated into the security
 badge required at work. Although dose records are poor for many workers and
 veterans, long-term studies of well-monitored workers have now been reported
 from nuclear facilities in the U.S., the United Kingdom and Canada. Despite
 the fact that workers are generally healthy adults, many of these studies
 have demonstrated
 relationships between low level radiation and cancer death, particularly
 among older workers. The greater sensitivity of older adults to ionizing
 radiation was not recognized in A-bomb studies due to selective survival,
 however this observation is consistent with studies that show reductions in
 immune function and efficiency of DNA repair with aging (6, 20). Risk
 estimates from many occupational studies are approximately 10 times higher
 than estimates based on follow-up of A-bomb survivors (21-33), showing that
 current protection standards
 are too lax. In our recent study of multiple myeloma among Oak Ridge,
 Hanford, Los Alamos and Savannah River workers, doses between 5 and 10 rems
 were associated with a threefold elevated risk, and doses over 10 rems were
 associated with a fivefold elevated risk (33). None of the multiple myeloma
 cases had recorded doses over the current U.S. occupational limit of five
 rems per year.

 From the United Kingdom comes evidence that paternal preconception exposures
 are associated with risk of childhood cancer, stillbirth and an excess of
 male compared to female births (34-36). The ability of radiation to induce
 heritable genetic mutations in experimental animals has been recognized since
 the 1920s (37). This recent evidence suggests that small doses of radiation
 delivered in the period prior to conception can lead to genetic effects in
 human offspring. Evidence on genomic instability following exposure to alpha
 radiation
 raises concerns for both carcinogenic and inherited genetic effects (38-40).

 The belief that radiation risks at low doses could be extrapolated from high
 dose studies led some to predict that cancer risks of radiation could not be
 detected among nuclear workers. Although this has turned out to be false,
 some researchers have pooled data from different worker populations in order
 to increase sample size, believing that this would increase power to detect
 radiation risks (41-43). Unfortunately, pooling populations with different
 types of radiation, exposure conditions, measurement qualities and worker
 selection factors, achieves statistical precision at the cost of accuracy,
 diluting radiation effects (43).

 Diseases and genetic mutations caused by radiation do not carry a marker
 showing their origins, therefore epidemiologists look for excess rates of
 disease in populations with higher radiation exposures. However, it is easy
 to design an epidemiological study of environmental or occupational radiation
 exposure that is unable to detect low level effects. Only in special
 circumstances, such as the cases of well-monitored workers and certain
 medical exposures (44), is it possible to quantify low doses and subsequent
 risk. The sensitivity of epidemiological studies is compromised because
 people generally cannot be traced between the time they are exposed and the
 time disease develops, and because medical information (other than cause of
 death) is not routinely available for populations without universal medical
 care. It is incorrect to conclude that low level radiation is safe on the
 basis of studies that lack careful radiation measurements and follow-up of
 medical outcomes. Unfortunately such conclusions have been made based on
 studies of geographic variation in average
 background radiation (45).

 Furthermore, some scientists have mistakenly claimed that there is no
 evidence of radiation health effects below some arbitrary level. Not only do
 such statements ignore an extensive medical literature on in utero and
 occupational radiation; they reflect a basic misunderstanding of how
 epidemiology works. In order to detect the risks from a hazardous agent,
 epidemiologists study a range of exposure levels. For example, we compare
 lung cancer rates of never-smokers to rates among people who smoke less than
 a pack a day, one pack a day, two packs a day, and three or more packs a
 day. It would be incorrect to separate the data for people who smoke one
 cigarette a day and declare that low levels of smoking are safe. Conclusions
 about health effects of agents such as radiation and cigarettes should be
 derived from data on a range of exposures.

 The current state of knowledge: As knowledge about ionizing radiation has
 grown, health effects have been
 recognized from activities that until recently were thought to be safe.
 Despite past assurances about the safety of nuclear weapons tests, the
 National Cancer Institute's recent study indicates that tens of thousands of
 Americans can expect to get thyroid cancer from just one of the radionuclides
 released by atmospheric testing (46). The fact that radiation protection
 standards have been reduced as scientific study of low doses increases is
 another measure of concern (7). Although the International Commission on
 Radiation Protection recommended in 1990 that the 5 rem per year limit for
 nuclear workers be reduced to 2, the U.S. continues to permit workers to be
 exposed to more than twice the radiation dose allowed by countries that
 adopted the international standard,
 including Canada and the European Union.

 The nuclear age is little more than a half-century old. Although much has
 been learned about radiation during this time, there is much more that
 remains to be understood about human health effects. It is increasingly
 clear that there is great variability in the sensitivity of humans to low
 level radiation due to factors such as age, genetic susceptibility and
 exposures to chemical agents, infection or nutritional factors. Decisions
 about exposure standards should take account of the special risks faced by
 the young, the old and the genetically susceptible. Public health and moral
 principles demand that we protect the most vulnerable.

 As amply documented by the Secretarial Panel for the Evaluation of
 Epidemiologic Research appointed by Admiral Watkins (47), President Clinton's
 Advisory Committee on Human Radiation Experiments (48), a taskforce of the
 Physicians for Social Responsibility (49), and numerous publications in the
 scientific
 literature (50-54), the body of scientific knowledge about the health effects
 of ionizing radiation has been compromised by concerns about secrecy and
 public relations. In its 1995 report, the President's Advisory Committee on
 Human Radiation noted that, "By the mid-1960s the possibility that data
 gathering could only get the AEC (Atomic Energy Commission) into more trouble
 became an incentive to 'not study at all'" (48). These attitudes have
 continued to affect research in recent decades (51, 52). In the case of
 regulatory standards
 that are intended to protect the health of workers and the public, policy
 makers should consider scientific evidence and testimony with the
 understanding that scientists have been restrained from fully investigating
 the effects of low level ionizing radiation.

 Current radiation standards already fail to adequately protect workers and
 the public, even if flawed risk estimates from A-bomb studies are used: The
 1994 GAO report on Nuclear Health and Safety notes that exposures permitted
 by current Nuclear Regulatory Commission and Department of Energy guidelines,

 according to those agencies, would lead to 1 in 300 premature cancer deaths
 in the general public and 1 in 8 among workers (55). No other carcinogens
 are permitted such lax standards. I strongly urge members of Congress and
 the regulatory agencies to exercise precaution and prudence in order to
 protect the health and lives of the public and of future generations who will
 be affected by decisions on production and disposition of nuclear materials.