Paniagua JM, Rufo M, Jiménez A, Antolín A, Pinar I. Medium wave exposure characterization using exposure quotients. Radiat Prot Dosimetry. Feb 16, 2010. Ahead of print.
The guidelines for the International Commission on Non-Ionizing Radiation Protection (ICNIRP) state that, in situations of simultaneous exposure to fields of different frequencies, exposure quotients for thermal and electrical stimulation effects should be examined. An aspect that is common to many of these epidemiological studies is the absence of a real measure of exposure. Instead, the distance from the contaminating source is used as surrogate. Distance, however, can be a poor indicator of exposure, since it does not take into account such key elements as the radiation’s frequency and polarization, the antennas’ radiation pattern and the barriers to exposure represented by such interposed physical elements such as mountains or large buildings.
The aim of the present work was to analyze the electromagnetic radiation levels and exposure quotients for exposure to multiple-frequency sources in the vicinity of medium wave radio broadcasting antennas.
Data collection was performed systematically, dividing the area into a grid of 5-km squares, and making one serie of measurements in each grid square for which there existed access by road or track. In this way, electric field spectra were collected at 45 points.
The results showed that the exposure quotient criterion based on electrical stimulation effects was found to be more stringent than those based on thermal effects or power density levels. The characterization of exposure for frequencies up to 10 MHz presents varying degrees of compliance with the International guidelines depending on whether one uses the radiation level (characterized by the power density) or the exposure quotients for multiple-frequency sources to avoid thermal and electrical stimulation effects.
Even though current guidelines have often been criticized, ecological or epidemiological studies have not applied them in their entirety. A correct dosimetry evaluation has to include the calculation of the aforementioned coefficients. This implies conducting spectral analyses, quantifying the electric field components and applying the criteria for exposure to multiple-frequency sources.