Radiofrequency and Microwave Radiation

Evaluating RF and Microwave Exposure

RF energy includes frequencies ranging from about 3000 cycles per second (3 kHz) to 300 billion cycles per second (300 GHz). Microwaves are a subset of radio waves and includes frequencies ranging from around 300 million cycles per second (300 MHz) to 3 GHz. RF exposures are directly linked to absorption and distribution of RF energy in the body, and the absorption and distribution are strongly dependent on body size and orientation and on frequency and polarization of the incident radiation. A common measure of exposure is the Specific Absorption Rate (SAR), the rate of energy absorption in tissue, measured in watts per kilogram of tissue.

  • C95.3, Recommended Practice for Measurements and Computations of Radio Frequency Electromagnetic Fields With Respect to Human Exposure to Such Fields, 100 kHz-300 GHz. Revises and develops specifications for preferred methods for measuring and computing external radiofrequency electromagnetic fields to which persons may be exposed.
  • 2345, Evaluation and Control of Personnel Exposure to Radio Frequency Fields — 3 kHz to 300 GHz. North Atlantic Treaty Organization (NATO) Standardization Agreement (STANAG).
  • Field Service Memo - Electromagnetic Radiation and How It Affects Your Instruments. OSHA, (May 20, 1990). Provides OSHA compliance officers with basic principles of electromagnetic (EM) radiation. Discusses the effects of radio frequency interference (RFI) on the operation of industrial hygiene instruments, explains why special isotropic probes are used for making non-ionizing radiation surveys, and emphasizes the need for special attention in measuring radio frequency fields.
Radio and Television Broadcast Stations
Amateur Radio
  • Radiofrequency Safety FAQs. Federal Communications Commission (FCC).
  • American Radio Relay League (ARRL)
    • The FCC's New RF-Exposure Regulations. Describes the FCC regulations which identify Maximum Permissible Exposure (MPE) derived from the Specific Absorption Rate (SAR) at which tissue absorbs RF energy, expressed in watts per kilogram (W/kg). From a safe SAR, the Standards and regulations set MPEs that vary with frequency. Human-body resonances fall in the frequency range from 30 to 300 MHz and are the most strictly controlled. The regulations define two primary RF-exposure environments "controlled/occupational" and "uncontrolled/general public." In a "controlled" RF environment people know that RF is present and can take steps to control their exposure. This applies to areas where you control access. The limits for controlled environments are evaluated differently (less stringent) than those for uncontrolled environments.
    • FCC RF-Exposure Regulations -- the Station Evaluation. Provides the power-density and field-strength formulas and tables which give the compliance distance in the main beam of the antenna, at any angle. The tables based on antenna modeling have calculated the horizontal compliance distances at ground level, and at first and second story exposure levels.
    • Measurements of Electromagnetic Fields at Amateur Radio Stations (PDF). FCC/OET Report ASD-9601, (January 1996). Describes a joint measurement study of environmental radiofrequency (RF) fields in the vicinity of nine amateur radio stations that was conducted by the FCC and the U.S. Environmental Protection Agency (EPA) in southern California. Measurements of electric and magnetic field strength were made in areas near amateur antennas and equipment in order to determine typical and "worst case" exposure levels.
Cell Phones Stations