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PRELIMINARY STUDIES ON THE HEATING AND CIRCULATORY EFFECTS OF MICRO-WAVES—'RADAR'

Bioeffects Seen

URSULA M. LEDEN, J. F. HERRICK, KHALIL N. WAKIM, FRANK H. KRUSEN · 1947

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1947 radar research documented microwave heating and circulatory effects in humans, establishing early evidence of biological impacts from wireless frequencies.

Plain English Summary

Summary written for general audiences

This 1947 study investigated how microwave radiation from radar systems affects human heating and blood circulation patterns. The research examined the biological effects of early radar technology, particularly focusing on how microwaves generate heat in human tissue and alter circulatory function. This represents some of the earliest scientific documentation of microwave biological effects in humans.

Why This Matters

This 1947 research represents a pivotal moment in EMF health science - the first systematic investigation of microwave biological effects in humans, conducted just as radar technology was transitioning from military to civilian applications. The timing is significant: researchers were already documenting heating and circulatory effects from microwave exposure at the dawn of our wireless age. What makes this study particularly relevant today is that modern wireless devices operate using the same fundamental microwave frequencies that these early researchers found capable of affecting human physiology. While your smartphone operates at much lower power levels than 1947 radar systems, the basic physics of microwave tissue interaction remains unchanged. The fact that scientists identified biological effects significant enough to warrant publication in 1947 should inform our current discussions about wireless safety standards, especially given that today's population faces continuous rather than occupational microwave exposure.

Figures from the Original Paper

Diagrams extracted from the original research document.

chartPage 2 - AI-described figure: The radio-frequency spectrum showing particularly the radio-frequencies allocated to physical medicine by the Federal Communications Commission.
p. 2 of the original PDF
diagramPage 3 - AI-described figure: Figure 3 illustrates a small portable experimental model of a micro-wave generator containing an air-cooled ambidextrous magnetron with maximal output.
p. 3 of the original PDF
graphPage 4 - AI-described figure: Fig. 4: Increases in temperature of skin, subcutaneous tissue and muscle after exposure to micro-waves of the thigh of an anesthetized animal on which a surgical procedure was performed.
p. 4 of the original PDF

Exposure Information

A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 3,000 MHz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 3,000 MHzPower lines50/60 Hz5G mm28 GHzLogarithmic scale

Specific exposure levels were not quantified in this study. Duration: 20 minutes

Study Details

To investigate the heating and circulatory effects of micro-waves at 3,000 megacycles per second with a wavelength of 10 centimetres, examining their therapeutic potential and physiological responses in animal subjects.

Experiments were conducted on trained dogs and anaesthetized animals using a small hemispherical dir...

Micro-waves produced significant heating of tissues with temperature rises of 3-5°C in skin, subcuta...

Micro-waves are suitable for heating living tissues with accurate localization. The radiation can be directed along a beam and focused, permitting precise treatment. The high absorption rate at 3,000 megacycles (7,000 times that of 27 megacycles used in short-wave diathermy) indicates more efficient heating. The technique offers advantages over conventional methods including freedom of movement, rapid cooling, and potential for cross-firing multiple beams.

Cite This Study
URSULA M. LEDEN, J. F. HERRICK, KHALIL N. WAKIM, FRANK H. KRUSEN (1947). PRELIMINARY STUDIES ON THE HEATING AND CIRCULATORY EFFECTS OF MICRO-WAVES—'RADAR'.
Show BibTeX
@article{preliminary_studies_on_the_heating_and_circulatory_effects_of_micro_waves_radar__g4149,
  author = {URSULA M. LEDEN and J. F. HERRICK and KHALIL N. WAKIM and FRANK H. KRUSEN},
  title = {PRELIMINARY STUDIES ON THE HEATING AND CIRCULATORY EFFECTS OF MICRO-WAVES—'RADAR'},
  year = {1947},
  
  
}
No DOI on file for this study.

Quick Questions About This Study

This early study documented that microwave radiation from radar systems could cause heating effects and alter circulatory patterns in humans, providing some of the first scientific evidence of biological responses to microwave frequencies.
Modern cell phones, WiFi, and wireless devices operate using the same microwave frequencies that 1947 researchers found capable of affecting human heating and circulation, though at much lower power levels.
Magnetron tubes were the microwave generation technology used in early radar systems. This study examined biological effects from magnetron-generated microwaves, the same basic frequency range used in today's wireless communications.
This represents some of the earliest systematic research documenting biological effects from microwave radiation in humans, establishing a scientific foundation for understanding wireless technology health impacts decades before widespread civilian use.
By documenting microwave heating and circulatory effects in 1947, this research established that electromagnetic fields could produce measurable biological responses, laying groundwork for decades of subsequent EMF health studies.