Electrical Impedance of the Human Body
Herman P. Schwan · 1968
Schwan's 1968 electrical impedance measurements of human tissue became the foundation for all modern EMF safety calculations.
Plain English Summary
This 1968 technical report by Herman Schwan examined how the human body conducts and resists electrical current, establishing foundational measurements of electrical impedance across different body tissues. The research provided critical baseline data for understanding how electromagnetic fields interact with human biology. This work became essential for later safety standards and EMF exposure calculations.
Why This Matters
Herman Schwan's 1968 research on human body electrical impedance represents foundational work that still influences EMF safety standards today. Understanding how our bodies conduct electricity is crucial because it determines how deeply electromagnetic fields penetrate our tissues and where energy gets absorbed. This research helped establish the electrical properties that govern everything from how your cell phone's radiation interacts with your head to how power line fields affect your body.
What makes this work particularly significant is its timing. Published just as electronic devices were becoming commonplace, Schwan's measurements provided the scientific basis for calculating specific absorption rates (SAR) and other exposure metrics we still use today. The reality is that every EMF safety standard relies on these fundamental electrical properties of human tissue to determine what constitutes 'safe' exposure levels.
Figures from the Original Paper
Diagrams extracted from the original research document.
Exposure Information
Specific exposure levels were not quantified in this study.
Study Details
To summarize available specific impedance data, to define body impedance and to relate it to electrode impedance, skin impedance and specific body impedance data, and to predict likely values of total body impedance for various electrode sizes and locations from known specific tissue impedance data and skin impedances
The report uses theoretical analysis based on specific tissue impedance data, skin impedance data, a...
The report predicts body impedance values for large electrodes (band electrodes) and smaller electro...
The study establishes theoretical ranges of radio frequency impedance of the human body in the 1-30 MHz range. Body impedance is dependent on electrode configuration, skin impedance, subcutaneous fat layer properties, and deep tissue properties. The electrical properties of skin are not significantly different from muscle above 100 KHz, allowing simplification of calculations. The derived formulas give body impedance values accurate within a factor of two when compared with limited measured data.
Show BibTeX
@article{electrical_impedance_of_the_human_body_g7350,
author = {Herman P. Schwan},
title = {Electrical Impedance of the Human Body},
year = {1968},
}