Some considerations on the challenges related to the use of the new ICNIRP restrictions for human exposure to radiofrequency fields

Abstract

Some considerations on the challenges related to the use of the new ICNIRP restrictions for human exposure to radiofrequency fields Goiceanu C, Danulescu R, Danulescu E. Some considerations on the challenges related to the use of the new ICNIRP restrictions for human exposure to radiofrequency fields. Radiat Prot Dosimetry. 2023 May 24;199(8- 9):818-825. doi: 10.1093/rpd/ncad084. Abstract ICNIRP 2020 guidelines for limiting exposure to radiofrequency fields replace the radiofrequency part of the ICNIRP 1998 guidelines for limiting exposure to time-varying electric, magnetic and electromagnetic fields. Besides setting new restrictions that prevent thermal effect they also took over the 100 kHz to 10 MHz part of the ICNIRP 2010 guidelines for limiting exposure to low-frequency electromagnetic fields, which provides restrictions that prevent nerve stimulation effect. The latest guidelines brought many changes to the system of protection against exposure to radiofrequency fields starting with the physical quantities used to express restrictions and continuing with specific restrictions and new exposure metrics employed. For the first time, the case of brief local exposure to intense radiofrequency fields was accounted by ICNIRP for setting new types of exposure restrictions. All these changes led to more detailed and complex guidelines, but their provisions are more difficult to apply in practice. Our paper presents some of the challenges related to the use in practice of the new ICNIRP restrictions for human exposure to radiofrequency fields. Excerpts In the domain of radio frequencies, two established effects are taken into account for setting exposure restrictions: thermal effect and nerve stimulation effect. To protect against thermal effect, the 2020 guidelines set basic restrictions in terms of Specific Absorption Rate (SAR) assessed as whole-body average (WBA), as well as local SAR in head and torso or in limbs. At frequencies above 6 GHz, basic restrictions were set for local absorbed power density (Sab) to account for heating localized at the surface of the body. These exposure limits have the same values as those used in previous guidelines from 1998, except the local absorbed power density limit that restricts the superficial heating at high frequencies. The new values of basic restriction for power density of 100 W m−2 for occupational exposure and of 20 W m−2 for general public exposure are twice the limit values set by 1998 guidelines. However, the reader should keep in mind that the new restrictions refer to absorbed power density, which is a measure of exposure of the body, while the old restrictions from 1998 concern the incident power density (Sinc) which is a parameter of the external field. The different values of the new basic restrictions are due to the decreased averaging area from 20 to 4 cm2 to match the face of the averaging volume (10 g) of SAR, and, therefore, the new restrictions on power density provide a consistent transition at 6 GHz(8). In addition to previous guidelines, the latest guidelines also included new types of restrictions to protect against brief local exposure to intense fields. For exposures lasting < 6 minutes, basic restrictions in terms of local specific absorption (SA), and absorbed energy density (Uab) were set. Moreover, the new guidelines also take into account the nerve stimulation effect and therefore, restrictions have been taken over from the ICNIRP 2010 guidelines on low-frequency electric and magnetic fields. Basic restrictions for nerve stimulation are expressed in terms of induced electric field strength and limit values are provided for frequencies between 100 kHz and 10 MHz. Conclusions The new ICNIRP 2020 guidelines are more detailed than previous guidelines and cover a wider range of exposure scenarios. New physical quantities and new metrics are used for setting restrictions on different types of exposure. Besides the whole-body exposure, the new radiofrequency guidelines provide reference levels for local exposure and brief intense local exposure. Although the guidelines are more comprehensive, their provisions might confuse the reader due to the complexity of changes, as well as the introduction of some new concepts and quantities that represents a challenge for practitioners who need to perform compliance evaluation. Considering the complexity and novelty of the new guidelines, training of personnel involved in measurement of radiofrequency field levels and evaluating compliance with exposure restrictions is needed. Besides additional information and advice on exposure restrictions and quantities expressing them, aspects related to practical determination of the new quantities or the use of new metrics should be approached. Guidance is needed on different technical issues as measurement of incident power density, especially within the radiative near-field zone, as well as averaging over 4 and 1-cm2 areas. For the determination of the newly introduced quantity, the incident energy density, clarification is needed on methods and equipment to use and how to process the measurement data. Moreover, between 100 kHz and 10 MHz, two sets of reference levels for both, electric and magnetic field strength, one set for thermal effect and the other one for nerve stimulation effect are provided and, consequently, guidance is necessary on the way to apply them. As the authors emphasized, generally one of the two sets of reference levels is more relevant for each electric or magnetic field strength. Further clarification is needed on which of the two types of reference level prevails and should be used when evaluating compliance in real exposure scenarios. The exact manner of measuring or calculating the physical quantities expressing all reference levels needs to be provided by relevant technical bodies. Standardized procedures should also take into account the characteristics of different types of sources and possible exposure scenarios accounting for reasonable assumable intended use, as well as for worst case exposure scenario. Moreover, manufacturers of measuring equipment should develop appropriate equipment and probes for measuring all physical quantities and cover all exposure metrics with the aim of allowing evaluation of compliance with all reference levels provided by the new guidelines. To conclude, the amount and the complexity of changes, as well as the novelty related to concepts, quantities and specific provisions led to more detailed and precise guidelines, but more complex and more difficult to assimilate and to use in practice. Therefore, qualified advice for good practice in evaluating compliance with guidelines is needed, as well as guidance for adequate measurement methods and procedures, and appropriate selection of measuring equipment. Further advice on the entire process of exposure assessment will be required to facilitate the implementation of the new ICNIRP guidelines in practice when they are adopted as European or national regulations. pubmed.ncbi.nlm.nih.gov

AI evidence extraction

Main findings

The paper describes changes introduced in ICNIRP 2020 RF guidelines (new physical quantities/metrics, inclusion of brief intense local exposure limits, and incorporation of 100 kHz–10 MHz nerve stimulation restrictions) and argues these make compliance evaluation more complex and difficult to apply in practice. It highlights needs for training, guidance, standardized procedures, and appropriate measurement methods/equipment to implement the new restrictions and reference levels.

Outcomes measured

• Practical challenges in applying ICNIRP 2020 exposure restrictions/reference levels for radiofrequency fields
• Exposure assessment/compliance evaluation metrics and measurement considerations (SAR, absorbed power density, absorbed energy density, induced electric field)

Limitations

• This is a considerations/guidance-focused paper rather than an empirical health-effects study (no study design, participants, or quantitative outcome data reported in the abstract).

Suggested hubs

• who-icnirp (0.95)
  Focuses on ICNIRP 2020 guidelines/restrictions and implementation challenges.

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