Experimental and clinical evidence on radiofrequency electromagnetic field effects on the blood–brain barrier: a scoping review

OBJECTIVE: This scoping review evaluates evidence on whether radiofrequency electromagnetic field (RF‑EMF) exposure influences blood-brain barrier (BBB) permeability. Given inconsistent findings across decades of research and expanding wireless technology use, we summarize results from in vivo, in vitro, and human studies with emphasis on exposure characterization and thermal control. Methods: Literature covering RF‑EMF exposures from ~900 MHz to frequencies relevant for emerging wireless systems was surveyed. Due to substantial heterogeneity in exposure conditions, i.e. specific absorption rates (SAR) from 0.01 to >10 W/kg, diverse modulation schemes, and varied biological endpoints, we performed a qualitative synthesis supported by a methodological audit focusing on dosimetric rigor, temperature monitoring, and sham‑control implementation. Results: Findings remain mixed: seventeen studies reported increased BBB permeability or molecular alterations, while eighteen observed no effects. Null‑result studies generally applied stricter dosimetry and thermal safeguards, though incomplete temperature documentation was common. Some in vitro studies suggest effects on tight-junction proteins or cellular stress pathways, but these outcomes show limited reproducibility in animal models. Human data are sparse and do not clearly differentiate thermal from non‑thermal influences. Conclusion: Current evidence does still not establish a causal link between RF‑EMF exposure and BBB disruption. Persistent methodological variability limits interpretability. Future work should employ rigorous exposure characterization, validated BBB biomarkers, and robust thermal and sham controls, and address gaps at higher frequencies and in vulnerable populations (prenatal, elderly).