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ELECTROMAGNETIC POWER DEPOSITION IN MAN EXPOSED TO HIGH-FREQUENCY FIELDS AND THE ASSOCIATED THERMAL AND PHYSIOLOGICAL CONSEQUENCES

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Arthur W. Guy, Curtis E. Johnson, James C. Lin, Ashley F. Emery, Kenneth K. Kraning · 1973

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1973 thermal modeling showed RF safety limits could be much higher than microwaves, but ignored non-thermal biological effects.

Plain English Summary

Summary written for general audiences

This 1973 study used mathematical models to calculate how much radiofrequency energy a 70-kilogram human would absorb at 20 MHz and below frequencies. Researchers found that exposure to 590 mW/cm² at 20 MHz would raise core body temperature by 2.1°C after 100-120 minutes, requiring the body to work harder to maintain thermal balance.

Why This Matters

This foundational research reveals a critical gap in how we understand EMF exposure limits. The study found that HF frequencies (like those used in radio broadcasting) could theoretically allow exposure levels 'many orders of magnitude' higher than the 10 mW/cm² microwave limits without immediate thermal effects. However, the 2.1°C temperature rise at 590 mW/cm² came with significant physiological costs including increased heart rate, cardiac output, and diverted blood flow. What's particularly relevant today is that this thermal-only approach to safety standards ignores non-thermal biological effects that modern research demonstrates occur at much lower exposure levels. The reality is that our current safety standards still rely heavily on this 50-year-old thermal model, despite mounting evidence of biological effects from everyday devices operating at far lower power densities.

Exposure Information

Specific exposure levels were not quantified in this study.

Cite This Study
Arthur W. Guy, Curtis E. Johnson, James C. Lin, Ashley F. Emery, Kenneth K. Kraning (1973). ELECTROMAGNETIC POWER DEPOSITION IN MAN EXPOSED TO HIGH-FREQUENCY FIELDS AND THE ASSOCIATED THERMAL AND PHYSIOLOGICAL CONSEQUENCES.
Show BibTeX
@article{electromagnetic_power_deposition_in_man_exposed_to_high_frequency_fields_and_the_g7011,
  author = {Arthur W. Guy and Curtis E. Johnson and James C. Lin and Ashley F. Emery and Kenneth K. Kraning},
  title = {ELECTROMAGNETIC POWER DEPOSITION IN MAN EXPOSED TO HIGH-FREQUENCY FIELDS AND THE ASSOCIATED THERMAL AND PHYSIOLOGICAL CONSEQUENCES},
  year = {1973},
  
  
}

Quick Questions About This Study

The study calculated that 590 mW/cm² of incident 20 MHz radiofrequency power would raise core body temperature by 2.1°C in a 70-kilogram person after 100-120 minutes of continuous exposure in controlled environmental conditions.
For each mW/cm² of incident 20 MHz radiation, the spherical human model absorbed less than 2.5 x 10⁻³ mW per cubic centimeter of tissue, suggesting much lower absorption rates at HF frequencies compared to microwaves.
Even though temperature regulation remained stable, the body paid physiological costs including increased skin blood flow, elevated heart rate, higher cardiac output, and blood flow diverted away from internal organs to maintain thermal balance.
The mathematical model predicted that steady-state thermal conditions would be achieved within 100-120 minutes of continuous exposure to 100 watts total power deposition from radiofrequency radiation at these frequencies.
The study calculated that 3,540 mW/cm² would produce heat stress index of 100 for a person at rest, while 900 mW/cm² would cause the same heat stress during work activity.