The U.S. Environmental Protection Agency has been collecting broadcast signal field intensity data for over 2 years to estimate population exposure to this form of nonionizing radiation. Measurement data have been obtained at 373 locations distributed throughout 12 large cities and collectively represent approximately 11,000 measurements of VHF and UHF signal field intensities. The VHF and UHF broadcast service is the main source of ambient radio frequency exposure in the United States. A computer algorithm has been developed which uses these measurement data to estimate the broadcast exposure at some 39,000 census enumeration districts within the metropolitan boundaries of these 12 cities. The results of the computations provide information on the fraction of the population that is potentially exposed to various intensities of radio frequency radiation. Special emphasis has been placed on determining the uncertainty inherent to the exposure estimation procedure, and details are provided on these techniques. A median exposure level (half of the population is exposed to greater than the median level) of 0.005-μ W/cm2 time-averaged power density has been determined for the population of the 12 cities studied, the cumulative population of which represents 18% of the total United States population. The data also suggest that approximately 1% of the population studied, or about 380,000, is potentially exposed to levels greater than 1 μ W/cm2, the suggested safety guide for the population in the USSR. Alternative techniques of using the measurement data to estimate population exposure are examined, and future extensions of this work are discussed.
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