8,700 Studies Reviewed. 87.0% Found Biological Effects. The Evidence is Clear.

Athermic and Thermic Absorption Processes with Microwaves from 1 mm to 30 cm

Bioeffects Seen

D. A. Copson · 1967

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This 1967 review established microwave safety limits based on heating effects that still influence today's standards.

Plain English Summary

Summary written for general audiences

This 1967 review examined microwave absorption in biological systems, covering wavelengths from 1 millimeter to 30 centimeters. The study focused on thermal effects like diathermy while acknowledging the growing need to understand biological hazards from microwave communications. It established early safety standards including a maximum exposure limit of 0.01 watts per square centimeter.

Why This Matters

This historical review represents one of the earliest comprehensive examinations of microwave biological effects, published during the dawn of our modern wireless age. What's striking is how the 0.01 watts per square centimeter exposure limit mentioned here translates to 10 milliwatts per square centimeter - a standard that remains influential in today's safety guidelines, despite being based primarily on thermal effects rather than the biological mechanisms we now understand. The study's focus on thermal absorption reflects the limited scientific understanding of that era, before research revealed non-thermal biological effects at much lower power levels. Today's smartphones, WiFi routers, and 5G networks operate within these decades-old thermal-based limits, yet we now have thousands of studies showing biological responses at exposure levels far below what causes measurable heating.

Exposure Information

Specific exposure levels were not quantified in this study.

Cite This Study
D. A. Copson (1967). Athermic and Thermic Absorption Processes with Microwaves from 1 mm to 30 cm.
Show BibTeX
@article{athermic_and_thermic_absorption_processes_with_microwaves_from_1_mm_to_30_cm_g5989,
  author = {D. A. Copson},
  title = {Athermic and Thermic Absorption Processes with Microwaves from 1 mm to 30 cm},
  year = {1967},
  
  
}

Quick Questions About This Study

The study examined microwaves ranging from 1 millimeter to 30 centimeters in wavelength, covering the spectrum used in diathermy applications and early communications systems of that era.
The study cited a maximum exposure standard of 0.01 watts per square centimeter of body surface, equivalent to 10 milliwatts per square centimeter in modern measurements.
The review concentrated on thermal absorption mechanisms because microwave applications at the time were primarily for diathermy (medical heating) and the non-thermal biological effects weren't yet understood or studied.
The review identified problems with microwave generation, transmission, distribution, impedance matching, and vacuum transitions at high power levels, including unwanted glow discharge from residual gases.
Masers provided distinctive illumination capabilities for biological studies, though they were limited by concentration limits of about one-half wavelength for the hot spot size they could create.