6,486 Studies Reviewed. 85.2% of Original Studies Found Biological Effects. The Evidence is Clear.
Shield Your Body

Note: This study found no significant biological effects under its experimental conditions. We include all studies for scientific completeness.

Whole Body / GeneralPart of the Glaser Archive

ON THE POSSIBILITY OF NONTHERMAL BIOLOGICAL EFFECTS OF PULSED ELECTROMAGNETIC RADIATION

No Effects Found

LAWRENCE D. SHER, EDWARD KRESCH, HERMAN P. SCHWAN · 1970

Share:

1970 study found pulsed EMF fields no more biologically active than continuous waves at equal power levels.

Plain English Summary

Summary written for general audiences

This 1970 study examined whether pulsed electromagnetic fields could cause biological effects through non-thermal mechanisms, specifically field-induced forces rather than heat generation. Researchers found that pulsed fields have no greater ability than continuous wave fields to produce these force effects, and that heating always occurs before any potential field-induced biological changes.

Why This Matters

This foundational research from 1970 established a key principle that still shapes EMF safety standards today. The study demonstrated that pulsed electromagnetic fields, which are used in modern wireless technologies, don't have special biological effects beyond what continuous wave fields produce at the same power levels. The researchers concluded that existing safety guidelines would prevent genetic effects if they exist. However, this analysis focused solely on field-induced force mechanisms and thermal effects, which represents just one piece of the biological interaction puzzle. What this means for you: while this study supported the thermal-only model of EMF effects that dominated regulatory thinking for decades, subsequent research has identified numerous non-thermal biological mechanisms that weren't considered in this early framework.

Figures from the Original Paper

Diagrams extracted from the original research document.

diagramPage 2 - Figure 1: Optical micrograph of pearl-chain formation with red blood cells in physiologic saline. Field strength is 50 V/cm (rms).
p. 2 of the original PDF
diagramPage 4 - AI-described figure: Figure 2: Exploded view of a cell assembly for experiments involving silicone globules in water.
p. 4 of the original PDF
graphPage 5 - Figure 3: Experimental determination of the time constant for pearl-chain formation vs. the applied rms electric field strength at 100 kHz.
p. 5 of the original PDF
graphPage 6 - AI-described figure: Figure 4 illustrates the enlistment, m, of available particles into pearl-chain formation over time in response to applied fields.
p. 6 of the original PDF
diagramPage 8 - Figure 5 (a) illustrates a diagram of electric field strength vs. time for a pulsed field with t1 and t2 as minimum and maximum values, respectively.
p. 8 of the original PDF
Cite This Study
LAWRENCE D. SHER, EDWARD KRESCH, HERMAN P. SCHWAN (1970). ON THE POSSIBILITY OF NONTHERMAL BIOLOGICAL EFFECTS OF PULSED ELECTROMAGNETIC RADIATION.
Show BibTeX
@article{on_the_possibility_of_nonthermal_biological_effects_of_pulsed_electromagnetic_ra_g4441,
  author = {LAWRENCE D. SHER and EDWARD KRESCH and HERMAN P. SCHWAN},
  title = {ON THE POSSIBILITY OF NONTHERMAL BIOLOGICAL EFFECTS OF PULSED ELECTROMAGNETIC RADIATION},
  year = {1970},
  
  
}
No DOI on file for this study.

Quick Questions About This Study

Pearl-chain formation refers to cells lining up in chains under electrical field exposure, used as a model to study field-induced force effects. This study showed the effect's time constant varies inversely with field strength squared.
No, this research demonstrated that pulsed fields have no greater ability to produce field-induced force effects compared to continuous wave fields of equal RMS (root mean square) field strength.
The study concluded that ANSI radiation protection guidelines would prevent genetic effects in humans via field-induced force mechanisms, if such effects exist, because thermal heating would always occur first.
In biological tissue with physiologic electrical conductivity, the study showed that heat development through electrical resistance losses occurs before field-induced forces can manifest, making thermal effects the primary concern.
The study identified heat development through electrical resistance losses and field-induced force effects caused by differences in passive electrical properties as the two primary interaction mechanisms between electromagnetic fields and tissue.