Utilization of developmental basic science principles in the evaluation ofreproductive risks from pre- and postconception environmental radiation exposures

The subject of the reproductive toxicity of various forms of radiation can be anxiety provoking to the public on two accounts, since reproductive fail ure engenders an unusual level of guilt and anger in the affected families, and radiation effects are misunderstood and feared by the public. Reproduc tive problems include an array of genetic and acquired diseases affecting p arents and their offspring. Many of these problems are associated with the risk of being induced by preconception and/or postconception exposures to e nvironmental agents. For the various forms of radiation, namely, ionizing r adiation, ultrasound, low-frequency electromagnetic fields (EMF), and micro waves, the potential for producing reproductive effects varies considerably with the form of "radiation" and, of course, the dose. Whether the exposur e occurs preconceptionally or postconceptionally is another major considera tion. In evaluating the actual reproductive risks, we rely on accurate dosi metry and information obtained in epidemiological studies and animal studie s. Epidemiological studies must demonstrate consistency of the reproductive finding, and animal studies should be designed to add to the findings of t he epidemiological studies, Most importantly, the conclusions must not cont radict the basic principles of teratology, genetics, and reproductive biolo gy, and they should be biologically plausible. But frequently important bas ic science principles are ignored in the evaluation process. Yet developmen tal basic science principles can be instrumental in refuting or supporting the concern about possible risks. Although there is some overlap with regar d to the preconception and intrauterine effects of ionizing radiation, ther e are significant differences. Preconception effects are mainly stochastic effects, while intrauterine effects are mainly deterministic effects. The s tochastic genetic risks are lower than the deterministic risks at equivalen t exposures. Thus, it is frequently difficult to demonstrate the occurrence of stochastic effects in populations that have received low preconception exposures to ionizing radiation. The reproductive effects from preconceptio n and intrauterine exposures to electromagnetic fields (low-frequency EMF, video display terminals, microwaves) and ultrasound represent much differen t problems, since the main effects of microwaves and ultrasound occur becau se of their hyperthermic effects at high exposures, low-frequency EMF does not have the capacity to produce hyperthermia, and none of these forms of n onionizing radiation has the specificity to damage the DNA comparable to th e specificity of ionizing radiation. Not only do they not have targeted mut agenic effects at the usual exposures that populations receive, they are no t cytotoxic at these exposure levels as well. From the viewpoint of biologi cal plausibility, these other forms of radiation are much less likely to ha ve the potential for producing reproductive toxicity at the usual populatio n exposures. (C) 1999 Wiley-Liss, Inc.