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Effects of microwave and radio frequency electromagnetic fields on lichens.

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Urech, M, Eicher, B, Siegenthaler, J · 1996

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Microwave radiation at 50 mW/cm² significantly reduced lichen growth by causing thermal damage and accelerated drying.

Plain English Summary

Summary written for general audiences

Swiss researchers exposed lichens (small organisms that grow on trees and rocks) to microwave radiation at 2.45 GHz for up to three years, using power levels similar to what you'd find near cell towers. They found that high-power microwave exposure (50 mW/cm²) significantly reduced the lichens' growth rate by causing them to heat up and dry out faster than normal.

Why This Matters

This study matters because lichens serve as biological indicators of environmental stress - they're like nature's canaries in the coal mine. The fact that microwave radiation at 50 mW/cm² caused measurable biological damage through heating effects demonstrates that even organisms we consider hardy can be affected by EMF exposure. While the researchers concluded the effects were primarily thermal, this doesn't diminish their significance. The 50 mW/cm² exposure level used in this study is well above typical environmental levels (which are usually measured in microwatts per square centimeter), but it's within the range you might encounter very close to high-powered transmitters. What this research reinforces is that biological systems respond to electromagnetic fields in measurable ways, and that thermal effects - often dismissed as 'safe' because they're understood - can still cause real biological harm.

Exposure Details

Power Density
0.2, 5, and 50 µW/m²
Source/Device
2.45 GHz

Exposure Context

This study used 0.2, 5, and 50 µW/m² for radio frequency:

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.

Where This Falls on the Concern Scale

Study Exposure Level in ContextStudy Exposure Level in ContextThis study: 0.2, 5, and 50 µW/m²Extreme Concern - 1,000 uW/m2FCC Limit - 10M uW/m2Effects observed in the Slight Concern rangeFCC limit is 50,000,000x higher than this level
A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 2.45 GHz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 2.45 GHzPower lines50/60 Hz5G mm28 GHzLogarithmic scale

Study Details

The effects of electromagnetic fields on lichens were investigated.

Field experiments of long duration (1-3 years) were combined with laboratory experiments and theoret...

Both species showed a substantially reduced growth rate at 50 mW/cm2. A differentiation between ther...

Theoretical estimates based on climatic data and literature showed that the growth reductions in the initial experiments could very likely have been caused by drying of the lichens from the heating with microwaves. The results of the other experiments support the hypothesis that the response of the lichens exposed to microwaves was mainly due to thermal effects and that there is a low probability of nonthermal effects.

Cite This Study
Urech, M, Eicher, B, Siegenthaler, J (1996). Effects of microwave and radio frequency electromagnetic fields on lichens. Bioelectromagnetics 17(4):327-334, 1996.
Show BibTeX
@article{urech_1996_effects_of_microwave_and_1393,
  author = {Urech and M and Eicher and B and Siegenthaler and J},
  title = {Effects of microwave and radio frequency electromagnetic fields on lichens.},
  year = {1996},
  
  url = {https://pubmed.ncbi.nlm.nih.gov/8891192/},
}
PubMed: 8891192

Cited By (13 papers)

Quick Questions About This Study

Swiss researchers found that 2.45 GHz microwave radiation at 50 mW/cm² significantly reduced lichen growth rates over three years. The microwaves heated the lichens' surface and accelerated their drying process, causing the growth reduction through thermal effects rather than non-thermal biological damage.
Yes, microwave radiation at cell tower frequencies (2.45 GHz) can damage lichens when power levels reach 50 mW/cm². A 1996 Swiss study showed this exposure substantially reduced lichen growth by heating their surfaces and causing accelerated drying over long-term exposure periods.
Research on lichens shows that 2.45 GHz microwave radiation causes biological effects at 50 mW/cm² power density. At this level, the radiation significantly reduced growth rates by heating the organisms' surfaces and accelerating moisture loss, demonstrating clear thermal biological impacts.
Yes, thermal effects likely explain most microwave radiation damage to living organisms. Swiss researchers found that 2.45 GHz exposure at 50 mW/cm² damaged lichens primarily through heating and drying, with low probability of non-thermal effects contributing to the biological damage.
No, 9.5 MHz radio frequency radiation at 235 V/m field strength showed no visible effects on lichen growth in Swiss research. Unlike 2.45 GHz microwaves, this lower frequency produced no thermal effects and caused no detectable biological damage to the organisms.