Testicular heat-shock protein expression in rats following 3.5 GHz and 24 GHz RF-EMF exposure.

The fifth generation of mobile technologies (5G) uses mid-band frequencies of 3.5 GHz and will use millimeter waves of 24 to 28 GHz in the future. Since testicular tissue is sensitive to environmental stressors and since previous studies have identified the harmful effects of radiofrequency electromagnetic fields, this study examines the impact of 5G mid-band and millimeter wave frequencies on molecular stress responses in the testes of rats. (The focus is on heat shock proteins, which, despite their name, are upregulated by a broad spectrum of cellular stressors, such as oxidative stress or toxins. These chaperones primarily assist other proteins in folding into their correct three-dimensional structures; editor’s note.)

Thirty-six male Sprague-Dawley rats were exposed to 3.5 GHz, 24 GHz, or a sham field for 1 or 7 hours daily over 60 days (n = 6). The 3.5 GHz signal was generated by a signal generator without frequency modulation. The 24 GHz signal, on the other hand, was generated by a commercial radar sensor designed for presence detection. This signal exhibits frequency modulation, but it does not correspond to that of typical cellular networks (neither time-pulsed nor focused). The sources were mounted 20 cm above the cages. The specific absorption rate (SAR) was simulated using a rat voxel model and extrapolated to a distance of 20 cm using a power law. Testicular tissue was examined histologically and immunohistochemically for heat shock proteins (HSP27, HSP70, and HSP90). Depending on the exposure duration, either a one-way ANOVA or a Tukey test was performed.

The whole-body SAR was 0.06 W/kg at 3.5 GHz and 1.8 × 10⁻⁷ W/kg at 24 GHz at a distance of 20 cm. Histologically, the seminiferous tubule structure remained largely intact, showing only slight, isolated changes with no widespread or advanced tissue damage. In contrast, heat shock protein expression was significantly altered in a frequency- and duration-specific manner. With 1-hour daily exposure, a significant reduction in HSP70 production was observed at both frequencies compared to the control group that was sham-exposed. This effect was not present with 7-hour exposure. However, the 7-hour exposure induced a significant increase in HSP90 at 3.5 GHz. HSP27, on the other hand, increased significantly after the 7-hour exposure, specifically at 24 GHz.

The authors conclude that low-level, 5G-relevant fields can alter stress signaling pathways in the testes while leaving the tissue structurally intact. The HSP70 response, which is considered atypical, involves downregulation after 1 hour per day of exposure and no difference after 7 hours per day. The absence of a sustained difference suggests that the initial response normalized or remained below the threshold for permanent induction. The increase in HSP90 after 7 hours of exposure per day at 3.5 GHz indicates proteostatic adaptation to low-threshold stress stimuli rather than direct cellular damage. This finding is consistent with the lack of histological evidence. Since millimeter waves are primarily absorbed at the surface and cannot penetrate deeper tissue layers, the significantly increased HSP27 production observed after 7 hours per day at 24 GHz indicates a distinct stress adaptation.

Editor’s note:

The safety of 5G exposure is called into question since the intensities used in the present study are below the limits for continuous exposure of the general population (SAR 0.08 W/kg). Heat shock proteins (HSPs), particularly HSP70 and HSP90, play a key role in normal spermatogenesis and not just the stress response. They are therefore of particular relevance to reproductive biology. Previous studies indicate that radiofrequency radiation can alter HSP expression in other tissues as well [1] (see ElektrosmogReport 03/2021). However, this publication may underestimate the biological effects of the 5G signal because it used unmodulated (3.5 GHz) and radar-modulated (24 GHz) signals. Recently published studies suggest that the biological effects of cellular network technologies are enhanced by their modulation patterns [2] (see ElektrosmogReport 02/2026). (RH)

1. Othman H, López-Furelos A, Leiro-Vidal JM, Ammari M, Sakly M, Abdelmelek H et al. (2021). Exposure to 2.45 GHz radiation triggers changes in HSP-70, glucocorticoid receptors and GFAP biomarkers in rat brain. International Journal of Molecular Sciences, 22(10), 5103. https://www.mdpi.com/1422-0067/22/10/5103

2. Panagopoulos DJ, Litovsky R, Chamberlin K (2026). Recording the extremely low frequency pulsations of wireless communication electromagnetic fields. Electromagnetic Biology and Medicine, 1–10. https://doi.org/10.1080/15368378.2026.2654072