Radiofrequency (RF) exposure standards may require more clarity, as well as further studies to identify possible thermal hazards to different types of tissues, according to a review article in a special issue of the International Journal of Hyperthermia.
The journal issue was based on an international workshop, entitled “Thermal Aspects of Radiofrequency Exposure” held Jan. 11-12, 2010, in Gaithersburg, Md., which focused on thermal hazards and the health and safety implications of RF exposure. Goals of the workshop included identifying the health endpoints for a given tissue, the most appropriate time periods for acute and chronic exposure, time-temperature thresholds for adverse effects, and cost effective-targeted research to better define thresholds.
Summarizing the workshop, authors Kenneth R. Foster, PhD, department of bioengineering, University of Pennsylvania in Philadelphia, and Joseph J. Morrissey, PhD, department of pharmaceutical sciences, Nova Southeastern University in Boston, stated that no major changes in the understanding of time-temperature thresholds have emerged since a 2003 World Health Organization workshop on the same topic. They also concluded that nothing from the workshop “suggested that exposure to RF energy within present exposure limits will lead to thermal injury.”
There are currently two major exposure standards for RF energy set by the IEEE (formerly the Institute of Electrical and Electronics Engineers) and the International Commission on Non-Ionizing Radiation Protection (ICNIRP). Both the IEEE and the ICNIRP standards have a number of limitations, according to findings of the workshop.
Exposure guidelines were based on power absorbed by tissues, however the “biological significant quantity is the thermal exposure,” wrote the authors. Additionally, some standards are based on experimental data of RF on a specific type of tissue, as opposed to tests on multiple different tissues and, according to the writers, the standards lack clarity.
“One speaker at the workshop … suggested that the rationale for choosing these limits for partial body exposures needs to be explained more clearly in the standards. Temperature increase or total thermal burden to the body would arguably be easier for the public to understand than [Specific Absorption Rate]," the review stated.
Workshop attendees presented information on the effects of RF exposure on testicular function, reproduction, the eyes, the nervous system, brain temperature, the cardiovascular system and several other tissues and systems. The authors stated that present limits are highly protective against thermal hazards, “perhaps excessively so,” and that standards for the general public are more protective against RF thermal hazards than recommended limits for the temperature of hot water in the home.
The full review can be found here.