Inconsistencies and open questions regarding low-dose health effects of ionizing radiation.

Abstract

The effects on human health of exposures to ionizing radiation at low doses have long been the subject of dispute. In this paper we focus on open questions regarding the health effects of low-dose exposures that require further investigations. Seemingly contradictory findings of radiation health effects have been reported for the same exposed populations, or inconsistent estimates of radiation risks were found when different populations and exposure conditions were compared. Such discrepancies may be indicative of differences in sensitivities among the applied methods of epidemiological analysis or indicative of significant discrepancies in health consequences after comparable total exposures of different populations under varying conditions. We focus first on inconsistencies and contradictions in presentations of the state of knowledge by different authoritative experts. We then review studies that found positive associations between exposure and risks in dose ranges where traditional notions (generalized primarily from high-dose studies of A-bomb survivors or exposed animals) would have predicted negligible effects. One persistent notion in many reviews of low-dose effects is the hypothesis of reduced biological effectiveness of fractionated low-dose exposures, compared to that of the same acute dose. This assumption is not supported by data on human populations. From studies of populations that live in contaminated areas, more and more evidence is accumulating on unusual rates of various diseases other than radiation-induced malignancies, health effects that are suspected to be associated with relatively low levels of internal exposures originating from radioactive fallout. Such effects include congenital defects, neonatal mortality, stillbirths, and possibly genetically transmitted disease. A range of open questions challenges scientists to test imaginative hypotheses about induction of disease by radiation with novel research strategies.ImagesFigure 1.

Childhood Leukemia and Cancers Near German Nuclear Reactors: Significance, Context, and Ramifications of Recent Studies

“…36 The additional dose due to fallout was never included in the survivor study. 35,36 Contrary to official assumptions, health effects from reactor emissions, like those in the KiKK study, are likely the result of internal exposures, inducing radiobiological mechanisms quite different from those induced by external exposures. 3.…”

“…8 However, numerous "authoritative" reports on the health legacy of the Chernobyl catastrophe have ignored evidence of serious flaws and gaps in knowledge on which the currently accepted models for population exposure and radiation risk estimates are based. 35 A number of radiobiological and dosimetric effects are ignored in the most widely-accepted version of the "current state of radiobiological knowledge:" It does not take into account:…”

“…Thus the A-bomb survivors are a selected population, hardly an appropriate cohort to use as a standard for determining radiation risks in normal populations. 35 2. Internal exposures that are not adequately modeled in current low-dose risk estimates.…”

Health Effects in a Casual Sample of Immigrants to Israel from Areas Contaminated by the Chernobyl Explosion

“…A detailed review of these effects is presented by Upton et al. (20) and, Nussbaum and Kohnlein (21). Under the auspices of the World Health Organization, Prilipko et al (22) are following several thousand children exposed to radiation in utero to evaluate evidence of Environmental Health Perspectives * Volume 103, Number 10, October 1995 Articles * Kordysh et al mental retardation.…”

Response: Science, Public Health, and Objectivity: Research into the Accident at Three Mile Island

“…Despite a century of research since Roentgen's discovery of X rays, fundamental disagreements exist over biophysical mechanisms, dose-response assumptions, analytical strategies, interspecies extrapolations, and the representativeness of studies of select human populations (1)(2)(3)(4)(5)(6)(7). In the United States, the last decade has seen revelations about human radiation experimentation (8) and a shift in responsibility for radiation health effects research from the Department of Energy to the Department of Health and Human Services, stimulated by concerns over secrecy and conflict of interest (9,10).…”