RF Exposure Limits: Evolution and Current Issues

his talk will briefly review the evolution of three major RF safety limits (IEEE C95.1, ICNIRP, and FCC) and their biological basis, as well as the changes that were recently introduced in the IEEE C95.1-2019 and ICNIRP 2020 limits at frequencies above 6 GHz [1]. At frequencies > 6 GHz the limits are based exclusively on the goal of limiting exposure-produced increases in tissue temperature to levels below anticipated hazards (chiefly, thermal damage and burns, and cutaneous thermal pain, with an appropriate margin of safety. I briefly review the scientific basis of the limits as related to 5G New Radio (NR) wireless technologies, which presently utilize three major bands of the RF spectrum: < 1 GHz (low band), around 3 GHz (mid band), and around 26 GHz (high band). Few novel issues arise from exposures to 5G NR systems in the low and mid bands that are different from those associated with earlier “G’s” of cellular technologies. High band 5G NR operates at frequencies used by few consumer-facing devices, but close to those used by many radar, security, and other applications. The energy penetration depth in tissue at such frequencies is slight < 1 mm) and there are no data to indicate existence of safety issues apart from those resulting from excessive heating of tissue (e.g., skin and corneal burns, cutaneous thermal pain). However, the number of RF bioeffects studies in this frequency range is very limited, approximately 100 studies in recent years. These vary greatly in endpoint, quality, and relevance to health and safety. Extensive reviews by the French health agency ANSES [2] as well as by independent scientists [3] have failed to find clear evidence for adverse effects at exposure levels below current U.S. and international exposure limits (FCC, IEEE, ICNIRP). I conclude that, based on present knowledge, present exposure limits offer high levels of protection against known hazards of RF energy from 5G NR systems (as for earlier generations of cellular technologies), which are thermal in nature. However, in view of the widespread anticipated exposure of the public to RF energy above 6 GHz from a host of consumer-facing equipment to be introduced in coming years, additional well-done safety studies are needed. Reference: [1] K. R. Foster, C-K. Chou, R. C. Petersen, Radiofrequency exposure standards. In Bioengineering and Biophysical Aspects of Electromagnetic Fields, Greenebaum and Barnes, eds., CRC Press 2018, pp. 463-511. [2] Agence nationale de sécurité sanitaire de l’alimentation, de l’environnement et du travail (ANSES). (2019). Expositions aux champs électromagnétiques liées au déploiement de la technologie de communication « 5G » et effets sanitaires éventuels associés. Available on the Internet at https://www.vie-publique.fr/sites/default/files/rapport/pdf/279567.pdf. [3] Karipidis, K., Mate, R., Urban, D., Tinker, R., Wood, A. (2021). 5G mobile networks and health. A state-of-the-science review of the research into low-level RF fields above 6 GHz. J Exp Sci Environ Epidemiol. 31, 585-605. DOI.org/10.11038/s41370-021-00297-6.