Section 4A: Safety Guidelines 167What levels of RF energy are considered safe?Various organizations and countries have developed standards for exposure toradiofrequency energy. These standards recommend safe levels of exposure forboth the general public and for workers. In the United States, the FCC has usedsafety guidelines for RF environmental exposure since 1985.The FCC guidelines for human exposure to RF electromagnetic fields arederived from the recommendations of two expert organizations, the NationalCouncil on Radiation Protection and Measurements (NCRP) and the Institute ofElectrical and Electronics Engineers (IEEE). In both cases, therecommendations were developed by scientific and engineering experts drawnfrom industry, government, and academia after extensive reviews of thescientific literature related to the biological effects of RF energy.Many countries in Europe and elsewhere use exposure guidelines developed bythe International Commission on Non-Ionizing Radiation Protection (ICNIRP).The ICNIRP safety limits are generally similar to those of the NCRP and IEEE,with a few exceptions. For example, ICNIRP recommends different exposurelevels in the lower and upper frequency ranges and for localized exposure fromcertain products such as hand-held wireless telephones. Currently, the WorldHealth Organization is working to provide a framework for internationalharmonization of RF safety standards.The NCRP, IEEE, and ICNIRP all have identified a whole-body SpecificAbsorption Rate (SAR) value of 4 watts per kilogram (4 W/kg) as a thresholdlevel of exposure at which harmful biological effects may occur. Exposureguidelines in terms of field strength, power density and localized SAR werethen derived from this threshold value. In addition, the NCRP, IEEE, and ICNIRPguidelines vary depending on the frequency of the RF exposure. This is due tothe finding that whole-body human absorption of RF energy varies with thefrequency of the RF signal. The most restrictive limits on whole-body exposureare in the frequency range of 30-300 MHz where the human body absorbs RFenergy most efficiently. For products that only expose part of the body, such aswireless phones, exposure limits in terms of SAR only are specified.The exposure limits used by the FCC are expressed in terms of SAR, electricand magnetic field strength, and power density for transmitters operating atfrequencies from 300 kHz to 100 GHz. The specific values can be found in twoFCC bulletins, OET Bulletins 56 and 65: http://www.fcc.gov/oet/info/documents/bulletins/#56; http://www.fcc.gov/oet/info/documents/bulletins/#65.Why has the FCC adopted guidelines for RF exposure?The FCC authorizes and licenses products, transmitters, and facilities thatgenerate RF and microwave radiation. It has jurisdiction over all transmittingservices in the U.S. except those specifically operated by the FederalGovernment. While the FCC does not have the expertise to determine radiationexposure guidelines on its own, it does have the expertise and authority torecognize and adopt technically sound standards promulgated by other expertagencies and organizations, and has done so. (Our joint efforts with the FDA indeveloping this website is illustrative of the kind of inter-agency efforts andconsultation we engage in regarding this health and safety issue.)
