These higher frequencies are in the millimeter wave (MMW) portion of the spectrum (30–300 GHz) and have been used for years in devices like airport scanners and security perimeter surveillance systems. One of the characteristics of MMW frequencies is that they do not penetrate past the skin (useful for detecting the outline of the human body, as in an airport scanner), but this characteristic means that MMW does not travel through foliage or buildings very well. Due to this limited penetration, communication with end users requires more base stations and the use of targeted beams.

Higher microwave frequencies and the increase of home (rather than just mobile) connections means that more sites are needed to connect all possible users. Most of these new sites will be like the one shown in Figure 2. In the United States, the Federal Communications Commission (FCC) has designated these sites as “Small Wireless Facilities” or SWFs. They qualify for SWF status because they are less than 50 feet in height and small in size.

For the general public, many people may assume that increasing the density of base stations would result in increased radiofrequency exposure in the ambient environment. However, as with older generations of cellular systems, one’s personal exposure is dominated by one’s own use of personal devices. Having more base stations in an area and more targeted beams for users is unlikely to substantially increase the “ambient” exposures, if at all. In fact, in areas with few base stations (a remote countryside, for example), more power is needed to continue communication between a cell phone and a base station. Closer and more densely placed base stations have the opposite effect: less power is needed to communicate, thus lowering exposure (both ambient and personal). With the use of MMW frequencies, the energy would also not penetrate as deeply into the body, decreasing dose.

Figure 3 depicts the exposures that the general public receives from common wireless sources. Exposures received are orders of magnitude lower than the standards allow, meaning there is little chance that the general public will be overexposed from these sources.

Power levels from these SWFs will be much lower than from larger sites so that they don’t interfere with each other. Still, exposures to people working near them may exceed standards. SWF sites will likely lead to a new group of people who may be exposed to significant amounts of NIR: municipal and utility workers who work close to these new types of sites.

EXPOSURE STANDARDS In the U.S., the FCC regulation “Human Exposure to Radiofrequency Electromagnetic Fields” (47 CFR 1.1310) is mandatory for all license holders, including wireless companies. ACGIH publishes limits that are partially based on IEEE C95.1-2005, IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz. The 2019 version of the IEEE standard is harmonized with guidelines from the International Commission on Non-Ionizing Radiation Protection (ICNIRP). It is likely that the ACGIH limits will be updated in the future to be consistent with the 2019 update to the IEEE standard. Canada uses similar limits from Safety Code 6, published in 2015. These standards and the FCC regulation are “two-tiered” and limit exposures of untrained persons to about one-fifth of those for trained persons.

Research conducted over past decades at many different frequencies has shown no reproducible health effects without a measurable increase in tissue temperature. Nonetheless, occupational limits are based on a factor of 10 below levels where health effects have been demonstrated, and limits for untrained workers and the general public are even lower (by a factor of 50).

From about 100 kilohertz (kHz) to 6 GHz, exposure limits are based on Specific Absorption Rate, or SAR, which represents RF exposure within tissues. Therefore, for most of the frequencies used by 5G (and 1G through 4G) mobile services, absorbed energy is the basis for limits. According to the Radiofrequency Radiation Dosimetry Handbook of the U.S. Air Force, the amount of energy found to negatively affect the mental acuity of animals after an extended period is 4 watts/kilogram (W/kg). This level is the basis for all standards and regulations governing RF exposure. A factor of 10 was used to set limits for humans at 0.4 W/kg; later, an additional factor of 5 was added (0.08 W/kg) for untrained workers and the general public. The frequency of emission will directly affect absorption, and frequencies that are close to whole-body resonance—that is, wavelengths that are approximately the size of a human body—create some of the highest absorptions. There have been no replicated studies that show any adverse health effects due to various types of modulation.

CONTROVERSY ABOUT EXPOSURE EFFECTS Most new technologies encounter some skepticism about their safety. Years ago, there were safety concerns about the exposure from the phones themselves, while today most people accept that risk (if any) because they have experienced the benefits of cell phones. It is difficult, if not impossible, for science to guarantee something like NIR is safe due to endless variables and permutations. Even though we have all lived with NIR (broadcast radio and television, two-way radio, and so on) throughout our lives, some individuals still believe the risks outweigh the benefits.

In today’s world, some groups benefit from creating controversy. Certain outlets publish “scientific” papers for a fee, without proper peer review. This practice can lead to seemingly legitimate publication of research results that do not meet industry norms and that would not have otherwise been published. In addition, the media rarely reports on debunked theories.

Another factor that has contributed to the perceived controversy is that 5G uses different modulations than earlier generations of cellular communications, and there is some industry disagreement on how pulses should be evaluated. FCC is proposing shorter averaging times above 6 GHz than IEEE or ICNIRP. The industry will file comments both for and against this proposal; however, it will most likely make a small and inconsequential difference to most communication systems. (For more information, see the article “5G Waveforms in Dispute” in Mircowave News.)

WHAT NEXT? While the general public will not be affected by 5G transmitters, many municipal and utility workers will need to operate near 5G sources. Each employer should develop an exposure control plan or safety plan that outlines the types of controls required for those working near SWF structures.

As with everything else, utilizing the hierarchy of controls will help reduce occupational exposures to those working on or near 5G transmitters. Controls such as locking-out the SWF (that is, removing the RF while work is performed); proper training, procedures, and signage; and monitoring RF levels while working will be key.

For many workers, RF safety will be a new subject. In the U.S., the FCC is clear about the knowledge that workers need to possess to qualify for higher exposure levels (recall that the exposure limit for trained workers is 50 times higher than for untrained workers). These training requirements are not unlike the Canadian requirements.

This type of safety training is necessary to comply with the regulations and help ensure safety for exposed workers. Note that RF levels from SWFs cannot be expected to be constant. For example, an SWF from one cellular provider will emit more RF than an SWF from another. Emissions from SWF also depend on the number of connected devices, which can vary from one SWF to another.

It would be helpful for worker protection to require more transparency about changes to infrastructure or power levels. As part of the “Middle Class Tax Relief and Job Creation Act of 2012,” providers in the U.S. are not required to inform local governments when changes occur, and those changes include power levels. In Canada, providers are required to comply with Safety Code 6 at all times, and the public can look up the power levels of any given antenna in their neighborhood. Some countries like the United Kingdom are also tracking radiofrequency workers in a national register to examine the possible health effects of mobile phone telecommunication technologies. This type of registry may prove useful in North America for future epidemiologic research.

In conclusion, 5G will not substantially change the general public’s exposure to radiofrequency, but it will change workers’ work practices. However, with proper planning and procedures, worker exposures can be adequately controlled. This is good news, as 5G is with us to stay … until 6G comes along.

Acknowledgement: The authors thank the AIHA Non-Ionizing Radiation Committee for its support and for suggesting this timely topic.

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