Recent epidemiological studies have focused attention on the measurement of ambient-level power frequency magnetic fields in residential and industrial settings. Because the existing IEEE standard for characterizing power frequency magnetic fields is intended for measurements near power lines, it have a number of residential fields. The authors describe the instrumentation and calibration procedures and outline measurement strategies which can overcome some of the shortcomings of the existing standard. Examples of ambient-level magnetic field measurements are also provided. It is concluded that instrumentation which can determine the magnitude, temporal variation, and harmonic content of magnetic fields is available for characterizing fields in residential and occupational settings. Miniaturized exposure meters that permit the recording of personal exposure to ambient-level magnetic fields during the course of daily activities have been developed and provide for more realistic exposure estimates. Procedures for instrument calibration exist over the dynamic range of interest, i.e., 0.1*10/sup -7/ T to greater than 1*10/sup -4/ T (0.1 mG to 1G).
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