LIMITING RF OVEREXPOSURE
The transmission of RF energy is currently a critical component in providing telecommunications services such as radio and television broadcasting, cellular telephones, radio communications for law enforcement, microwave point-to-point links, and satellite communications. For many years, the public, policymakers, and health researchers have been concerned about the potential risks of overexposure to radio frequency (RF) radiation. Studies have, however, indicated that generally, the environmental levels of RF radiation normally encountered by the general public are far below the levels required to produce heat transfer and increased body temperature.
Still, there are situations, particularly workplace environments near high-powered sources of RF radiation, such as those of tower climbers, roof-top technicians, and bucket truck workers, where the limits for safe RF exposure could be exceeded. In these cases, preventive measures or actions may be necessary to ensure the safe working around RF radiation. In this article, we discuss the limits of RF radiation exposure and the scenarios where such limits are likely to be exceeded.
What are the limits of RF radiation exposure?
RF radiation comprises electric (E) and magnetic (H) fields and exposure guidelines require compliance with both of these. When the human body is exposed to RF fields, the frequency of the RF itself determines the absorption thereof in the body. This is why exposure guidelines have a shaped response over frequency, that is, the maximum radio frequency energy (or Specific Absorption Rate (SAR)) in watts per kilogram (W/kg) that can be safely absorbed by people. Compliance becomes even more important when working in close proximity to transmitting antennas – known as the near-field. Most of the national standards are based on the well-established International Commission on Non‐Ionizing Radiation Protection guidelines or the protection of humans exposed to RF fields in the range 100 kHz to 300 GHz. These guidelines include “upcoming 5G technologies, as well as AM and DAB radio, WiFi, Bluetooth and the currently used 3G/4G mobile phones.”
Where are limits likely to be exceeded?In telecommunications systems antennas are used to transmit and receive RF, with the highest intensity being closest to a transmitting antenna. The intensity of RF is the highest nearest to the source and drops off rapidly with distance. This combined with the actual amount of power transmitted by the antenna will determine the area around the transmitting antenna that may exceed the safety limits.
New technologies continue to develop at a rapid pace which will undoubtedly lead to new sources of RF energy in the environment. Even though the majority of people are not exposed to high RF fields, it is important to continue evaluating the potential for human exposure to ensure that exposure levels remain acceptable and safe.
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