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

Abstract

Overview

The growing use of 28 GHz millimeter-wave technology for fifth-generation (5G) wireless communication has raised concerns about its potential thermal effects, which can cause pain and tissue damage in exposed body parts. Despite the widespread adoption, the exact threshold at which thermal sensation is perceived by humans—defined by the change in skin temperature from baseline—remains not well established.

Methods

• Twenty healthy adults participated in the study.
• Participants' left middle fingertip was exposed to 28 GHz millimeter-waves at five different antenna input power levels: 0.2, 1.1, 1.6, 2.1, and 3.4 W (incident power density: 27–399 mW/cm²).
• The measurement session was repeated twice on the same day to assess reliability.
• Statistical reliability was evaluated using intraclass correlation coefficient (ICC) and Bland-Altman analysis.
• Perception rate—the number of participants who perceived a sensation at each exposure level—was also measured.

Findings

• Mean thermal sensation thresholds ranged from 0.9°C to 1.0°C for 126–399 mW/cm², and 0.2°C for 27 mW/cm².
• ICCs for the threshold were poor at 27 mW/cm² and fair at 126 mW/cm², while higher exposure levels yielded moderate to substantial reliability.
• No significant fixed bias was found except for a proportional bias at 191 mW/cm².
• All participants reported a sensation at the highest exposure (399 mW/cm²).
• The rate of perceived sensation decreased with lower exposure levels; notably, two-thirds noticed a sensation at the lowest tested power (27 mW/cm²).

Conclusion

Results indicate that the human thermal sensation threshold for 28 GHz millimeter-wave exposure is about 1.0°C, consistent across tested exposure levels, with reliability increasing as exposure increases. Nonetheless, even at lower exposure levels where the skin temperature increase is minimal, a significant proportion of participants perceived a sensation, indicating that thermal sensation from millimeter-wave exposure can occur at low power densities. The authors note that perception may be ambiguous due to the subjective nature of human sensation, underscoring the importance of continued assessment of potential health risks from EMF exposure, especially considering tissue safety and possible pain induction.