Medical/biological study (experimental study)

A study on biological effects of low-intensity millimeter waves med./bio.

By: Yu G, Coln EA, Schoenbach KH, Gellermann M, Fox P, Rec L, Beebe SJ, Liu S

Published in: IEEE Trans Plasma Sci 2002; 30 (4): 1489-1496

Aim of study (acc. to author)

To study the non-thermal effects of millimeter waves in the frequency range from 41-43 GHz on the growth rate and the absorption spectrum of Escherichia coli. In addition, the effect of this exposure on DNA was studied by measuring plasmid transformation efficiency.

Endpoint

different effects on Escherichia coli (growth rate, absorption spectrum, transformation efficiency)

Exposure

- 41–43 GHz
- millimeter waves

Exposure	Parameters
Exposure 1: 41–43 GHz Exposure duration: continuous for 40 min. growth rate experiment	power density: 32 mW/cm² (for the sample in the center) power density: 2.6 mW/cm² (for the second sample)
Exposure 2: 41.3–41.9 GHz Exposure duration: not given in the article relative absorption spectrum of millimeter waves	-
Exposure 3: 41–41.7 GHz Exposure duration: continuous for 15 min. transformation efficiency	power density: 12 mW/cm²

Exposure 1

Main characteristics

Frequency	41–43 GHz
Type	electromagnetic field
Exposure duration	continuous for 40 min.
Additional info	growth rate experiment

Exposure setup

Exposure source	horn antenna anechoic chamber
Setup	1 cm thick piece of Styrofoam placed on top of the pyramidal horn antenna in the anechoic chamber; samples positioned on top of the Styrofoam - one sample in a well in the center of the horn, the other in the adjacent well of a 12-well culture plate
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
power density	32 mW/cm²	-	calculated	-	for the sample in the center
power density	2.6 mW/cm²	-	calculated	-	for the second sample

Exposure 2

Main characteristics

Frequency	41.3–41.9 GHz
Type	electromagnetic field
Exposure duration	not given in the article
Additional info	relative absorption spectrum of millimeter waves

Exposure setup

Exposure source	millimeter wave generator
Setup	E. coli suspension distributed on a 6 mm x 3 mm rectangle of a 8 mm x 5 mm filter paper with a thickness of 0.17 mm; filter paper placed between two flanges in the path of the millimeter wave

Parameters

No parameters are specified for this exposure.

Exposure 3

Main characteristics

Frequency	41–41.7 GHz
Type	electromagnetic field
Exposure duration	continuous for 15 min.
Additional info	transformation efficiency
Additional info	frequency raised in 0.1 GHz steps

Exposure setup

Exposure source	same setup as exposure 1
Setup	a 25 µ l volume of the plasmid was added to one well of a 96-well microtitre plate
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
power density	12 mW/cm²	-	calculated	-	-

Exposed system:

bacterium
plasmid DNA (with an antibiotics resistance)
Escherichia coli/XL1-Blue

Methods Endpoint/measurement parameters/methodology

genotoxicity/mutation: transformation efficiency (entry of plasmid DNA into the bacteria; colony forming units in antibiotics containing agar plates)
cell function: absorption spectrum of millimeter waves
cell viability/cell division/proliferation: growth rate (spectrophotometry)

Investigated system:

bacterium

Time of investigation:

after exposure

Main outcome of study (acc. to author)

The data did not show any statistically significant frequency-dependent effects on the growth of bacteria, nor any frequency-dependent effects on the DNA plasmid transformation efficiency. The only indication for resonant effects was found in the absorption spectrum of Escherichia coli. However, in control experiments and by changing the length of the waveguides in the millimeter wave system, the resonant-like absorption was found to be caused by the millimeter wave system itself.
The findings indicate that resonance effects are unlikely in this particular frequency range.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Air Force Office of Scientific Research (AFOSR), USA

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Webb SJ et al. (1969): Absorption of microwaves by microorganisms
Webb SJ et al. (1968): Inhibition of bacterial cell growth by 136 gc microwaves

A study on biological effects of low-intensity millimeter waves med./bio.

Aim of study (acc. to author)

Endpoint

Exposure

Exposure 1

Main characteristics

Exposure setup

Parameters

Exposure 2

Main characteristics

Exposure setup

Parameters

Exposure 3

Main characteristics

Exposure setup

Parameters

Methods Endpoint/measurement parameters/methodology

Main outcome of study (acc. to author)

Study funded by

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