Collision of Evidence and Assumptions: TMI Deja View.
Evidence of health effects from radiation released during the 1979 accident at the Three Mile Island (TMI TMI Too Much Information
TMI Three Mile Island
TMI TRMM Microwave Imager
TMI Transactions on Medical Imaging
TMI Texas Military Institute
TMI Teen Missions International
TMI Tauber Manufacturing Institute ) nuclear generating station continues to be of interest, especially following the U.S. Supreme Court's recent reinstatement of claims of approximately 2,000 plaintiffs. Unfortunately, Talbott et al.'s analysis of mortality of nearby residents (1) does little to increase our understanding of the accident's health impact.
Talbott et al.'s paper (1) suffers from the same logical mistake that we identified previously (2). Specifically, the authors undertook a study in which empirical findings cannot lead to rejection of the study's null hypothesis null hypothesis,
n theoretical assumption that a given therapy will have results not statistically different from another treatment.
n . Both Talbott et al. (1) and Hatch et al. (3,4), who reported on the Columbia University Columbia University, mainly in New York City; founded 1754 as King's College by grant of King George II; first college in New York City, fifth oldest in the United States; one of the eight Ivy League institutions. studies of cancer incidence, began with the assumption that the maximum possible radiation doses from the accident were well below average annual background radiation levels. Even if standard radiation risk estimates are underestimated by an order of magnitude A change in quantity or volume as measured by the decimal point. For example, from tens to hundreds is one order of magnitude. Tens to thousands is two orders of magnitude; tens to millions is three orders of magnitude, etc. or more, such doses would be associated with very small increases in cancer in a general population with heterogeneous susceptibility (2). Given the measurement constraints of epidemiologic studies, it would not be possible to detect an accident-related increase in cancer at the dose levels assumed by these authors. Thus, when they find increased cancer rates among residents assumed to have received relatively higher radiation doses from the accident, such as the significant linear trend in female breast cancer (1), the authors must conclude that the association is not due to the exposure they are studying. There is no scientific reason to conduct a study in which the null hypothesis cannot be rejected due to a priori assumptions a priori assumption (ah pree ory) n. from Latin, an assumption that is true without further proof or need to prove it. It is assumed the sun will come up tomorrow. . This logical problem was further discussed in letters to EHP EHP
1. effective horsepower
2. electric horsepower (5-8). Interestingly, Talbott et al. (1) did not cite our paper, which introduced this logical problem (2), or the subsequent letters (5-8).
Talbott et al. (1) did not consider the possibility that some people received radiation doses from the TMI accident that were substantially higher than background. Such a possibility is supported by residents' reports of acute symptoms following the accident (9,10) and by evidence of elevated chromosomal aberration Noun 1. chromosomal aberration - any change in the normal structure or number of chromosomes; often results in physical or mental abnormalities
chromosomal anomaly, chromosonal disorder, chrosomal abnormality rates among persons reporting symptoms (11,12). The radiation dose estimates used by Talbott et al. depended on extensive assumptions about releases and dispersion because no measurements were available for individuals in the study (13). Simplistic sim·plism
The tendency to oversimplify an issue or a problem by ignoring complexities or complications.
[French simplisme, from simple, simple, from Old French; see simple assumptions were made about exponential decline of emissions and dispersion over the first 10 days of the accident (13). Further misclassification should be expected from errors in responses to survey questions about locations and movements of persons during this time period. Inability to accurately classify doses in an epidemiologic study threatens its ability to detect effects. Neither Talbott et al. (1) nor the authors of the Columbia studies (3,4) discussed exposure measurement error in interpreting their findings.
Gur et al. (13), the authors of the dosimetry dosimetry /do·sim·e·try/ (do-sim´e-tre) scientific determination of amount, rate, and distribution of radiation emitted from a source of ionizing radiation, in biological d. report, state that their methodology was developed "for educational, public relations public relations, activities and policies used to create public interest in a person, idea, product, institution, or business establishment. By its nature, public relations is devoted to serving particular interests by presenting them to the public in the most and defensive epidemiology purposes." This description of the rationale for dosimetry reminds us of the constraints on TMI dosimetry imposed upon other investigators by court order (2,6). That order (14) prohibited the investigators from making
upper limit or worst case estimates of releases of radioactivity or population doses ... [unless] such estimates would lead to a mathematical projection of less than 0.01 health effects and specified that a technical analyst ... designated by counsel for the Pools [nuclear industry insurers] concur on the nature and scope of the [dosimetry] projects.
We were disappointed in the lack of detail provided by Talbott et al. (1) regarding epidemiologic methods typically used in cohort studies. An advantage of their study compared to the Columbia University study (3,4) is that exposed persons could be followed as they left the area; however, there is no information given regarding methods of vital status follow-up, death certificate retrieval, or determination of loss to follow-up. Talbott et al.'s (1) Table 1 presents information for a "1992 cohort," including the number of households, implying that a 'second survey of households might have been done. However, no information is given to explain the 1992 cohort or its relationship to the 1979 cohort.
Because exposed persons were followed, Talbott et al. (1) could also have addressed the problem of tracing birth cohorts through time, a method that could not be employed in the Columbia study (2). Fetal and childhood exposures appear to be particularly effective in producing cancer (15,16); therefore, analyses of cancer mortality among persons exposed at those ages would be of special interest. Talbott et al. (1), however, excluded persons younger than 18 years of age from their dose--response analyses.
The number of persons and cancer deaths included in relative risk regression analyses of dose response were not given (1). These numbers may differ from those presented in Tables 1-4 not only because of the exclusion of persons under 18 years of age but also because of Talbott et al.'s requirement that members of the cohort be born within 1 month of the case in order to be included in the risk set for the case. The authors gave no rationale for using such a narrow restriction, which could limit the size of risk sets, especially at older ages (the median age for the cohort was reported as 29 years), leading to a possible loss of precision because of small risk sets or even loss of cases for which there were no eligible controls.
Studies of relationships between cancer and environmental exposures typically take into account latency periods known to occur between exposure and disease. Failure to consider exposure lag times reduces sensitivity to detect the effects under investigation. Talbott et al. (1) presented no latency analyses.
Although the data collected by Talbott et al. (1) appear to have the potential to advance our understanding of mortality in the TMI area, lack of information about the materials and methods limits our ability to evaluate their report. Furthermore, the statistical issues raised above lead us to question the sensitivity of their analysis to effects under investigation. We hope that more information about this study will be presented in the future, that further analyses will be conducted using methods which increase the study's sensitivity and precision, and that interpretations will be offered that are not inhibited by the a priori assumption that positive results cannot be interpreted as evidence in support of the hypothesis being investigated.
REFERENCES AND NOTES
(1.) Talbott EO, Youk AO, McHugh KP, Shire JD, Zhang A, Murphy BP, Engberg RA. Mortality among the residents of the Three Mile Island accident For details on this station, see .
The Three Mile Island accident was the most significant in the history of the American commercial nuclear power generating industry. It resulted, however, in no deaths or injuries to plant workers or members of the nearby community. area: 1979-1992. Environ Health Perspect 108:545-552 (2000).
(2.) Wing S, Richardson D, Armstrong D, Crawford-Brown D. A reevaluation of cancer incidence near the Three Mile Island nuclear plant: the collision of evidence and assumptions. Environ Health Perspect 105:52-57 (1997).
(3.) Hatch MC, Beyea J, Nieves JW, Susser M. Cancer near the Three Mile Island nuclear plant: radiation emissions. Am J Epidemiol 132:397-417 (1990).
(4.) Hatch MC, Wallenstein S, Beyea J, Nieves JW, Susser M. Cancer rates after the Three Mile Island nuclear accident and proximity of residence to the plant. Am J Public Health 81:719-24 (1991).
(5.) Susser M. Consequences of the 1979 Three Mile Island accident continued: further comment [Letter]. Environ Health Perspect 105:566-567 (1997).
(6.) Wing S, Richardson D, Armstrong D. Response: Science, public health and objectivity: research into the accident at Three Mile Island [Letter]. Environ Health Perspect 105:567-570 (1997).
(7.) Mangano J. Low-level radiation harmed humans near Three Mile Island [Letter]. Environ Health Perspect 105:786 (1997).
(8.) Wing S, Richardson D, Armstrong D. Response [Letter]. Environ Health Perspect 105:787 (1997).
(9.) Moholdt B. Summary of acute symptoms by TMI area residents during accident. In: Proceedings of the Workshop on Three Mile Island Dosimetry. Philadelphia, PA:Academy of Natural Sciences, 1985;A109-111.
(10.) Aamodt M, Aamodt N v. United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. Nuclear Regulatory Commission Nuclear Regulatory Commission (NRC), an independent U.S. government commission, created by the Energy Reorganization Act of 1974 and charged with licensing and regulating civilian use of nuclear energy to protect the public and the environment. . Docket A written list of judicial proceedings set down for trial in a court.
To enter the dates of judicial proceedings scheduled for trial in a book kept by a court. No. 50-289. Administrative Court, Washington, DC, 1984.
(11.) Shevchenko V, Snigiryova G. Cytogenetic cytogenetic /cy·to·ge·net·ic/ (-je-net´ik)
1. pertaining to chromosomes.
2. pertaining to cytogenetics.
pertaining to or originating from the origin and development of the cell. effects of the action of ionizing radiation i·on·i·zing radiation
High-energy radiation capable of producing ionization in substances through which it passes.
Ionizing radiation on human populations. In: Consequences of the Chernobyl Catastrophe: Human Health (Burlakova E, ed). Moscow:Center for Russian Environmental Policy, Scientific Council on Radiobiology radiobiology /ra·dio·bi·ol·o·gy/ (-bi-ol´ah-je) the branch of science concerned with effects of light and of ultraviolet and ionizing radiations on living tissue or organisms. , Russian Academy of Sciences Russian Academy of Sciences (Russian: Росси́йская Акаде́мия Нау́к, , 1996;23--45.
(12.) Shevchenko V. Assessment of genetic risk from exposure of human populations to radiation. In: Consequences of the Chernobyl Catastrophe: Human Health (Burlakova E, ed), Moscow:Center for Russian Environmental Policy, Scientific Council on Radiobiology, Russian Academy of Sciences, 1996;46-61.
(13.) Gur D, Good W, Tokuhata G, Goldhaber M, Rosen J, Rao G, Herron J, Miller D, Hollis R. Radiation dose assignment to individuals residing near the Three Mile Island nuclear station. Proc PA Acad Sci 57:99-102 (1983).
(14.) Rambo S. Three Mile Island Litigation An action brought in court to enforce a particular right. The act or process of bringing a lawsuit in and of itself; a judicial contest; any dispute.
When a person begins a civil lawsuit, the person enters into a process called litigation. . Civil Action 79-0432. Middle District of Pennsylvania, U.S. District Court, 1986.
(15.) Stewart AM, Webb J, Giles D, Hewitt D. Malignant diseases in childhood and diagnostic irradiation in utero in utero (in u´ter-o) [L.] within the uterus.
In the uterus.
in utero adv. . Lancet 2:447 (1956).
(16.) Stewart A. The role of epidemiology in the detection of harmful effects of radiation. Environ Health Perspect 108:93-96 (2000).
Steve Wing Department of Epidemiology School of Public Health University of North Carolina North Carolina, state in the SE United States. It is bordered by the Atlantic Ocean (E), South Carolina and Georgia (S), Tennessee (W), and Virginia (N). Facts and Figures
Area, 52,586 sq mi (136,198 sq km). Pop. Chapel Hill, North Carolina Chapel Hill is a town in North Carolina and the home of the University of North Carolina at Chapel Hill (UNC-CH), the oldest state-supported university in the United States. As of the 2000 census, it had a population of 48,715. As of 2004 its estimated population was 52,440. E-mail: email@example.com David Richardson International Agency for Research on Cancer The International Agency for Research on Cancer (IARC, or CIRC in its French acronym) is an intergovernmental agency forming part of the World Health Organisation of the United Nations.
Its main offices are in Lyon, France. Lyon, France