A SCHEME FOR INCORPORATING DC MAGNETIC-FIELDS INTO EPIDEMIOLOGIC STUDIES OF EMF EXPOSURE

Experimental data on calcium-ion release in chicken brain tissue sugge st that biological effects of electric and magnetic fields (EMFs) are concentrated near certain ''active combinations'' of DC magnetic field strength and ''effective'' AC magnetic field frequencies. We hypothes ize that active AC/DC combinations may exist and suggest that epidemio logic data, coupled with DC magnetic field measurements, may be used t o identify critical exposure conditions. An empirical model is used to calculate these multiple active combinations at any given DC magnetic field strength and to define a rating system that incorporates the pr oximity of AC magnetic field frequencies generated by electric power l ines to the new, computed effective frequencies. Such an exposure scor e may be useful in investigating correlations of EMF exposure with dis ease incidence. For 60 Hz and 50 Hz, the highest EMF exposure scores o ccurred at DC field strengths of 506 mG and 422 mG, respectively. The exposure score contains a factor which may be adjusted to reflect the importance of harmonics of the AC magnetic field as well as of the fun damental frequency. Using this factor, we consider two important speci al cases consistent with chick brain data: 1) we consider active pairs associated with all detectable harmonics (up to 660 Hz) without regar d to relative intensity of the harmonics, and 2) we use the relative i ntensities of the AC field frequencies to adjust their contribution to the exposure score. (C) 1993 Wiley-Liss, Inc.