Characterization of the Core Temperature Response of Free-Moving Rats to 1.95 GHz Electromagnetic Fields

The present study investigated the core body temperature (CBT) response of free-moving adult male and female Sprague Dawley rats, during and following a 3-h exposure to 1.95 GHz radiofrequency electromagnetic fields (RF-EMFs) within custom-built reverberation chambers, using temperature capsules implanted within the intraperitoneal cavity and data transmitted via radiotelemetry. Comparing RF-EMF exposures (at Whole-Body Average-Specific Absorption Rate [WBA-SAR] levels of 0.1, 0.4, and 4 W/kg) to the sham exposed condition, we identified a statistically significant peak increase in CBT after 26 min of RF-EMF exposure at 4 W/kg (+0.49°C), but not in the 0.1 or 0.4 W/kg conditions at the same timepoint. In the last 30 min of the RF-EMF exposure, temperature was significantly increased in both the 4 W/kg (0.62°C) and 0.4 W/kg (0.14°C) conditions, but not 0.1 W/kg, when compared to sham. After 20 min following cessation of exposure, post temperature was still significantly higher in the 4 W/kg condition when compared to the sham (0.37°C), but not in either 0.1 or 0.4 W/kg. Based on our findings, it is apparent that rats can effectively compensate for increased thermal loads of up to 4 W/kg as the maximum temperature rise was substantially lower than 1°C. In addition, the elevated CBT during exposure in the 4 W/kg condition was significantly reduced immediately after exposure cessation, indicating that measures of CBT following RF-EMF exposure cessation may not reflect maximum RF-EMF-mediated changes in the CBT of rats. Bioelectromagnetics. 00:00–00, 2025. © 2025 Bioelectromagnetics Society.