Evaluation of residential exposure to intermediate frequency magnetic fields.

The authors measured the exposure to intermediate-frequency (IF: 10 kHz to 30 MHz) electromagnetic fields (EMF) in residential environments. They developed a system to acquire and record waveforms of IF magnetic fields (MFs) and set 5 nanotesla (nT) for the trigger level of acquisition. They operated the system near power lines, railroads, and electrical appliances as possible sources of IF-MFs. Most of the maximum values of magnetic flux density and the time derivative for each wave were below the upper limit of the measurable range of our system (i.e., 53 nT and 10 T/s); these values were much lower than the minimum amplitudes that can theoretically induce heating or membrane excitation within biological systems. Moreover, the amplitudes of the IF-MFs were not related to those of extremely low frequency (ELF) MF measured simultaneously, indicating that IF-MFs do not underlie the associations, observed in several epidemiological studies, between residential exposure to ELF-EMF and childhood cancer.