Citation

Dagro AM, Wilkerson JW, Thomas TP, Kalinosky BT, Payne JA. Sci. Adv. 2021; 7(44): eabd8405.

Copyright

(Copyright © 2021, American Association for the Advancement of Science)

DOI

10.1126/sciadv.abd8405

PMID

34714682

Abstract

When considering safety standards for human exposure to radiofrequency (RF) and microwave energy, the dominant concerns pertain to a thermal effect. However, in the case of high-power pulsed RF/microwave energy, a rapid thermal expansion can lead to stress waves within the body. In this study, a computational model is used to estimate the temperature profile in the human brain resulting from exposure to various RF/microwave incident field parameters. The temperatures are subsequently used to simulate the resulting mechanical response of the brain. Our simulations show that, for certain extremely high-power microwave exposures (permissible by current safety standards), very high stresses may occur within the brain that may have implications for neuropathological effects. Although the required power densities are orders of magnitude larger than most real-world exposure conditions, they can be achieved with devices meant to emit high-power electromagnetic pulses in military and research applications.

The interactions between biological effects and electromagnetic (EM) fields (EMFs) are the subject of over a century of scientific research, motivated by innovations in biomedical applications and the development of safety standards. For EMFs in the frequency range of 0 Hz to 300 GHz, the most widely used guidelines for human exposure are designed to protect against adverse health effects associated with electrostimulation as well as local and whole-body heating. For frequencies in the radiofrequency (RF)/microwave range, it is well accepted that tissue heating is typically the main effect from interactions with EMFs.

The bulk of scientific literature uses continuous waves and moderate field strengths (typical of real-life scenarios), with less emphasis on pulsed fields of very high peak strength that may occur with ultrawideband pulse generators or EM pulse simulators. It is worth investigating whether extremely high peak power sources applied with a slow repetition frequency, or low duty cycle, can induce injurious effects without thermal buildup greater than a few degrees Celsius...

Language: en