Biological effects due to weak electric and magnetic fields: The temperature variation threshold

A large number of epidemiological and experimental studies suggest that pro longed (>100 s) weak 50-60-Hz electric and magnetic field (EMF) exposures m ay cause biological effects (NIEHS Working Group, NIH, 1998; Bersani, 1999) . We show, however, that for typical temperature sensitivities of biochemic al processes, realistic temperature variations during long exposures raise the threshold exposure by two to three orders of magnitude over a fundament al value, independent of the biophysical coupling mechanism. Temperature va riations have been omitted in previous theoretical analyses of possible wea k field effects, particularly stochastic resonance (Bezrukov and Vodyanoy 1 997a. Nature. 385:319-321; Astumian et al., 1997 Nature. 338:632-633; Bezru kov and Vodyanoy, 1997b. Nature. 338:663; Dykman and McClintock, 1998. Natu re. 391:344; McClintock, 1998; Gammaitoni et al,, 1998, Rev. Mod. Phys. 70: 223-287). Although sensory systems usually respond to much shorter(similar to 1 s) exposures and can approach fundamental limits (Bialek, 1987 Annu. R ev. Biophys. Biophys. Chem. 16:455-468; Adair et al,, 1998. Chaos. 8:576-58 7), our results significantly decrease the plausibility of effects for nons ensory biological systems due to prolonged, weak-field exposures.