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An Analysis Of Radiofrequency And Microwave Absorption Data With Consideration Of Thermal Safety Standards

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Richard A. Tell · 1978

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This 1978 EPA analysis established thermal-only safety standards that ignore non-thermal biological effects from RF radiation.

Plain English Summary

Summary written for general audiences

This 1978 EPA technical report analyzed how radiofrequency and microwave radiation is absorbed by biological tissue, specifically examining thermal safety standards used to protect people from heating effects. The study represents early government efforts to establish exposure limits based on the assumption that heating is the primary health concern from RF radiation.

Why This Matters

This EPA technical note represents a pivotal moment in EMF regulation history. In 1978, federal agencies were grappling with how to protect the public from radiofrequency and microwave radiation as these technologies proliferated. The focus on 'thermal safety standards' reveals the fundamental assumption that guided decades of regulation: that heating effects are the primary concern from RF exposure. This thermal-only approach became the foundation for current safety standards, yet it completely ignores the mounting evidence of non-thermal biological effects at much lower power levels. What's particularly significant is that this EPA analysis occurred during the early days of widespread microwave technology adoption, when the agency had the opportunity to establish more comprehensive safety standards. Instead, the narrow focus on thermal effects set a regulatory precedent that persists today, even as thousands of studies demonstrate biological impacts well below heating thresholds.

Finding

A method of specifying safety standard limits based on the electromagnetic field energy density rather than the plane wave, free-space equivalent power density is presented. The analysis reveals a particularly important resonance frequency range, 10 MHz < f <1000 MHz, in which RF and MW absorption may lead to whole body thermal loads several times the whole body basal metabolic rate for exposures equal to the present safety standard in use in the United States.

In their words

“A method of specifying safety standard limits based on the electromagnetic field energy density rather than the plane wave, free-space equivalent power density is presented. The analysis reveals a particularly important resonance frequency range, 10 MHz < f <1000 MHz, in which RF and MW absorption may lead to whole body thermal loads several times the whole body basal metabolic rate for exposures equal to the present safety standard in use in the United States.”

Exposure Information

A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 10 MHz to 1000 MHz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 10 MHz to 1000 MHzPower lines50/60 HzCell phones~1 GHzWiFi2.4 GHz5G mm28 GHzLogarithmic scale

Specific exposure levels were not quantified in this study.

Study Details

To analyze existing radiofrequency and microwave absorption data to examine the frequency dependent phenomenon of biological tissue heating and determine exposure field intensities associated with various levels of RF and MW induced thermal loading

Cite This Study
Richard A. Tell (1978). An Analysis Of Radiofrequency And Microwave Absorption Data With Consideration Of Thermal Safety Standards.
Show BibTeX
@article{an_analysis_of_radiofrequency_and_microwave_absorption_data_with_consideration_o_g7286,
  author = {Richard A. Tell},
  title = {An Analysis Of Radiofrequency And Microwave Absorption Data With Consideration Of Thermal Safety Standards},
  year = {1978},
  
  
}
No DOI on file for this study.

Quick Questions About This Study

The EPA examined safety standards based on preventing tissue heating from radiofrequency and microwave absorption. These thermal-based limits became the foundation for current exposure guidelines that focus solely on preventing temperature increases in body tissue.
In 1978, heating was considered the primary mechanism of harm from radiofrequency radiation. The scientific understanding of non-thermal biological effects was limited, leading regulators to establish safety standards based exclusively on preventing tissue temperature increases.
Modern research shows biological effects from RF radiation occur at power levels far below those that cause heating. The 1978 thermal-only approach ignored these non-thermal mechanisms that current studies demonstrate can affect cellular function, DNA, and neurological processes.
The EPA analyzed how different radiofrequency and microwave frequencies are absorbed by biological tissue, focusing on absorption rates that could cause heating. This data formed the basis for specific absorption rate (SAR) limits still used today.
Current safety standards based on this 1978 thermal analysis may be inadequate for modern wireless devices. They don't account for non-thermal effects, pulsed signals, or chronic low-level exposures that characterize today's electromagnetic environment.