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The effects of radiofrequency (< 30 MHz) radiation in humans.

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Zhao Z, Zhang S, Zho H, Zhang S, Su J, Li L, · 1994

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Workers exposed to RF radiation above 100 V/m showed heart rhythm abnormalities, suggesting current safety limits may inadequately protect cardiovascular health.

Plain English Summary

Summary written for general audiences

Chinese researchers studied 121 workers exposed to radiofrequency radiation below 30 MHz for over a year, comparing those exposed to high levels (100 V/m or higher) versus low levels. While blood tests and nervous system function remained normal in both groups, workers exposed to higher radiation levels showed heart rhythm abnormalities on their electrocardiograms (ECGs). The researchers suggested 100 V/m as a safety limit for this type of radiation exposure.

Why This Matters

This occupational health study provides important evidence that radiofrequency radiation can affect heart function at levels well within current exposure guidelines. The finding of ECG abnormalities in workers exposed to 100 V/m or higher is particularly significant because these are the types of field strengths you might encounter near industrial RF equipment, broadcast transmitters, or even some medical devices. What makes this research compelling is its real-world approach, studying actual workers with chronic exposure rather than short-term laboratory conditions. The fact that researchers recommended 100 V/m as an exposure limit based on their cardiac findings suggests that current safety standards may not adequately protect against cardiovascular effects of RF radiation.

Exposure Details

Electric Field
<, > or = 100 V/m
Source/Device
< 30 MHz

Exposure Context

This study used <, > or = 100 V/m for electric fields:

Building Biology guidelines are practitioner-based limits from real-world assessments. BioInitiative Report recommendations are based on peer-reviewed science. Check Your Exposure to compare your own measurements.

A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 30 MHz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 30 MHzPower lines50/60 HzCell phones~1 GHzWiFi2.4 GHz5G mm28 GHzLogarithmic scale

Study Details

The Aim of this study is to investigate The effects of radiofrequency (< 30 MHz) radiation in humans.

121 workers who were exposed to RFR (< 30 MHz) over one year were examined. They were divided into t...

No significant changes in the functioning of the autonomic nervous system and blood parameters (Hb, ...

Cite This Study
Zhao Z, Zhang S, Zho H, Zhang S, Su J, Li L, (1994). The effects of radiofrequency (< 30 MHz) radiation in humans. Rev Environ Health 10(3-4):213-215, 1994.
Show BibTeX
@article{z_1994_the_effects_of_radiofrequency_1466,
  author = {Zhao Z and Zhang S and Zho H and Zhang S and Su J and Li L and},
  title = {The effects of radiofrequency (< 30 MHz) radiation in humans.},
  year = {1994},
  
  url = {https://pubmed.ncbi.nlm.nih.gov/7724880/},
}
PubMed: 7724880

Cited By (6 papers)

Quick Questions About This Study

A 1994 Chinese study found that workers exposed to radiofrequency radiation below 30 MHz at levels of 100 V/m or higher showed heart rhythm abnormalities on ECGs. Workers exposed to lower levels had normal heart rhythms, suggesting 100 V/m as a safety threshold.
Chinese researchers studying 121 workers exposed to radiofrequency radiation below 30 MHz for over a year found no significant changes in blood parameters including hemoglobin, white blood cells, or blood platelets in either high or low exposure groups.
Based on a 1994 workplace study, researchers suggested 100 V/m as an exposure limit for radiofrequency radiation below 30 MHz. Workers exposed above this level showed heart rhythm abnormalities, while those below remained unaffected.
A study of 121 workers exposed to radiofrequency radiation below 30 MHz found no significant changes in autonomic nervous system function, even in those exposed to high levels of 100 V/m or higher for over one year.
Chinese researchers found that workers exposed to radiofrequency radiation below 30 MHz at levels of 100 V/m or higher developed ST-T interval changes and abnormal heart rates on their electrocardiograms, while lower-exposed workers showed normal ECG patterns.