Tuesday, 18 June 2019

US study shows changes in radio signal exposures since 1980

  US antenna
  Image: Flickr/Steve Bozak

FM radio signals are still the greatest contributor to public radio frequency (RF) exposure in the US, a comparison of outdoor exposure to wireless signals across 15 major metropolitan areas from 1980 has found.

While cellular networks weren’t in widespread use in 1980, the 2014 study published in Radiation Protection Dosimetry found FM radio remained the highest source of RF signals compared to cellular frequencies or the VHF and UHF frequencies used for television, emergency radio, cordless phones and public radio.
“The fields in the FM band were greater than the average fields from the other bands across the entire power density range, with the low/high VHF values clearly much lower than the others,” the study said.
“In both the 1980 and the present study, the power density in the FM band was a major contributor to overall power density, but over time, power densities in the VHF and UHF band decreased and increased, respectively.”
The researchers found exposure levels in all the frequency ranges were well below the US national safety standard limits.
“Not unexpectedly, the relative power densities were orders of magnitude lower than the Federal Communications Commission's (FCC) maximum permissible exposure (MPE) for the general public, with a maximum time-averaged value across the VHF–FM–UHF–cellular bands of 0.12 % of the MPE (AM's contribution was negligible).”
The authors also compared their results with those of surveys done in several European countries and found FM exposures were greater in the US due radio stations broadcasting at higher power.
“Despite differences in source attribution among countries, commonly observed ambient RF power densities remain far below the exposure limits published by the FCC, ICNIRP, and the IEEE,” they said.


Published 29/05/2014

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