Recent Results on Determining Population Exposure to VHF and UHF Broadcast Radiation in the United States

The U.S. Environmental Protection Agency has been collecting broadcast signal field intensity data for over three years to estimate population exposure to this form of nonionizing radiation. Measurement data have been obtained at 486 locations distributed throughout 15 large cities and collectively represent approximately 14,000 measurements of VHF and UHF signal field intensities. The VHF and UHF broadcast service is the main source of ambient radiofrequency exposure in the United States. A computer algorithm has been developed which uses these measurement data to estimate the broadcast exposure at some 47,000 census enumeration districts within the metropolitan boundaries of these 15 cities. The results of the computations provide information on the fraction of the population that is potentially exposed to various intensities of radiofrequency 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 (that level to which half of the population is exposed greater than) of 0.005 uW/cm2 time averaged power density has been determined for the population of the 15 cities studied, the cumulative population of which represents 20 percent of the total United States population. The data also suggest that approximately 1 percent of the population studied, or about 441,000 are potentially exposed to levels greater than 1 uW/cm2, the suggested safety guide for the population in the USSR.