The thermal sensation threshold and its reliability induced by the exposure to 28 GHz millimeter-wave

Abstract

The thermal sensation threshold and its reliability induced by the exposure to 28 GHz millimeter-wave Akiko Y, Shintaro U, Kazuki U, Sachiko K, Norika A, Akimasa H, Yohei O. The thermal sensation threshold and its reliability induced by the exposure to 28 GHz millimeter-wave. Frontiers in Neuroscience. 18. 2024. doi: 10.3389/fnins.2024.1331416. Abstract The application of 28 GHz millimeter-wave is prevalent owing to the global spread of fifth-generation wireless communication systems. Its thermal effect is a dominant factor which potentially causes pain and tissue damage to the body parts exposed to the millimeter waves. However, the threshold of this thermal sensation, that is, the degree of change in skin temperature from the baseline at which the first subjective response to the thermal effects of the millimeter waves occurs, remains unclear. Here, we investigated the thermal sensation threshold and assessed its reliability when exposed to millimeter waves. Twenty healthy adults were exposed to 28 GHz millimeter-wave on their left middle fingertip at five levels of antenna input power: 0.2, 1.1, 1.6, 2.1, and 3.4 W (incident power density: 27– 399 mW/cm<sup>2</sup>). This measurement session was repeated twice on the same day to evaluate the threshold reliability. The intraclass correlation coefficient (ICC) and Bland–Altman analysis were used as proxies for the relative and absolute reliability, respectively. The number of participants who perceived a sensation during the two sessions at each exposure level was also counted as the perception rate. Mean thermal sensation thresholds were within 0.9°C–1.0°C for the 126– 399 mW/cm<sup>2</sup> conditions, while that was 0.2°C for the 27 mW/cm<sup>2</sup> condition. The ICCs for the threshold at 27 and 126 mW/cm<sup>2</sup> were interpreted as poor and fair, respectively, while those at higher exposure levels were moderate to substantial. Apart from a proportional bias in the 191 mW/cm<sup>2</sup> condition, there was no fixed bias. All participants perceived a thermal sensation at 399 mW/cm<sup>2</sup> in both sessions, and the perception rate gradually decreased with lower exposure levels. Importantly, two-thirds of the participants answered that they felt a thermal sensation in both or one of the sessions at 27 mW/cm<sup>2</sup>, despite the low-temperature increase. These results suggest that the thermal sensation threshold is around 1.0°C, consistent across exposure levels, while its reliability increases with higher exposure levels. Furthermore, the perception of thermal sensation may be inherently ambiguous owing to the nature of human perception. Open access paper: frontiersin.org

AI evidence extraction

Main findings

Twenty healthy adults were exposed on the left middle fingertip to 28 GHz millimeter-wave at five antenna input powers (0.2, 1.1, 1.6, 2.1, 3.4 W; incident power density 27–399 mW/cm^2) in two sessions on the same day. Mean thermal sensation thresholds were 0.9–1.0°C for 126–399 mW/cm^2 and 0.2°C for 27 mW/cm^2; ICCs indicated poor (27 mW/cm^2), fair (126 mW/cm^2), and moderate-to-substantial reliability at higher exposure levels, with no fixed bias except proportional bias at 191 mW/cm^2. All participants perceived thermal sensation at 399 mW/cm^2 in both sessions, and perception rates decreased at lower exposure levels; two-thirds reported sensation in one or both sessions even at 27 mW/cm^2.

Outcomes measured

• Thermal sensation threshold (change in skin temperature from baseline at first subjective thermal sensation)
• Reliability of thermal sensation threshold (intraclass correlation coefficient; Bland–Altman analysis)
• Perception rate of thermal sensation at each exposure level

Suggested hubs

• 5g-policy (0.55)
  Study explicitly frames 28 GHz mmWave as prevalent due to 5G and examines human thermal sensation under 28 GHz exposure.

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    "population": "Twenty healthy adults",
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    "main_findings": "Twenty healthy adults were exposed on the left middle fingertip to 28 GHz millimeter-wave at five antenna input powers (0.2, 1.1, 1.6, 2.1, 3.4 W; incident power density 27–399 mW/cm^2) in two sessions on the same day. Mean thermal sensation thresholds were 0.9–1.0°C for 126–399 mW/cm^2 and 0.2°C for 27 mW/cm^2; ICCs indicated poor (27 mW/cm^2), fair (126 mW/cm^2), and moderate-to-substantial reliability at higher exposure levels, with no fixed bias except proportional bias at 191 mW/cm^2. All participants perceived thermal sensation at 399 mW/cm^2 in both sessions, and perception rates decreased at lower exposure levels; two-thirds reported sensation in one or both sessions even at 27 mW/cm^2.",
    "effect_direction": "unclear",
    "limitations": [],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
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    "keywords": [
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        "millimeter-wave",
        "mmWave",
        "thermal sensation threshold",
        "skin temperature",
        "incident power density",
        "fifth-generation (5G)",
        "reliability",
        "intraclass correlation coefficient",
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