THE EFFECT OF MILLIMETER WAVES ON THE MICROFLORA IN ROOM AIR.

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• Document Number (FOIA) /ESDN (CREST): CIA-RDP96-00787R000500090008-2
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• Document Page Count: 7
• Document Creation Date: November 4, 2016
• Document Release Date: December 7, 1998
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• Content Type: PAPER

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ELECTRONIC ENGINEERING, SERIES 1, MICROWAVE ELECTRONICS, N0. 12, pp. 132-136,
1966
by
V. G. Adamenko, R. L. Dilenskaya, M. V. Golant, I. M. Kiryuhsina, A.
Abstract
Results are given of an experimental investigation of the possibility
of the sterilizing action of millimeter waves on microflora in the air of a
laboratory room. The dependence of the bactericidal effect of electromagnetic
fields in the millimeter range on wavelength and on irradiation time is demon-
strated.
The literature contains information on the bactericidal and bacterial
static action of the electromagnetic fields over a wide range of radiofrequencies--
from low frequencies to microwave frequencies [1-7]. The results are obtained
'r
mainly for eradiation of bacteria which are situated in a liquid medium (in the
farm of a microsuspension).
The effect of the electromagnetic fields iri the millimeter range on
air microflora began to be investigated comparatively recently. As a result
of the investigations, a reduction in the number of bacteria in air was de-
tected when a millimeter-wave oscillator was in operation.
The present paper is devoted to investigating the effect of an elec-
tro magnetic field in the millimeter range of wavelengths on the microflora in
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the air of a laboratory room for the purpose of clarifying the possibilities
of the bactericidal action of millimeter waves.
2. THE EXPERIMENTAL PROCEDURE
In order to irradiate the microflora in the air of a laboratory room
i
having a volume of SO m3 a backward-wave tube of BOB-612 type operating in a
continuous-wave mode was used. The dispersion characteristic of the tube is
shown in Fig. 1. The wide range of electronic tuning of the tube (5.7 to 8.0 mm)
allows only an oscillator to be used to investigate the effect of various fre-
quencies on the microflora in the air.
At the required frequency the tube was tuned by varying the voltage
across the slow-wave system. The wavelength was measured by a tune wave meter
within 0.3%. The power was measured by means of a thermistor bridge connected
at the output of microwave path through a calibrated attenuator. The power was
monitored during the measurement process by means of an indicator connected
through a directional coupler. The magnitude of the power fluctuations during
the experiment did not exceed 10%.
A diagram of the unit is illustrated in Fig. 2. (Insert Figs. 1 and 2,
RP 133, Fig. 1 - Dependence of the Wavelength on the Voltage Across the Slow-
Wave System; Fig. 2 - Block Diagram of the Unit for Irradiating the Microflora
in the Air)
The irradiation of the microflora in the air of the room was carried
out at various wavelengths (5.7 to 7.1 mm) from the open end of a standard wave-
guide having a cross-section of 2.6 x 5.2 at an approximately identical power
level (a power of approximately 100 mW).
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The working ventilator (with a productivity of 40 m3/h) and convection
created a continuous change in the air entering the irradiation zone.
(Footnote bottom of RP 134)
* A Czech modification of the Krotov instrument was used--the Chirana type S
aeroscope.
*~ The figure shows the results of experiments with and without irradiation,
averaged aver five measurements. The investigations were performed at a wave-
length of 6 mm.
The over-all bacterial seeding of the air was studied. The investiga-
tions were carried out by two methods simultaneously--by the sedimentation method
(the Koch cup method) and the aspiration method (using a device of the Krotov*-
instrument type). The samples were taken at various points of the room at dis-
tances of from 2 to 5 m from the radiation source.. A 4% meat-peptone agar was
used as the nutrient medium. The exposure time of the cups in the sedimentation
method lasted 30 min, while in the aspiration method it lasted 1 min. During
this time approximately 45 to 50 liters of air passed through the instrument.
The collection of the samples (from several cups in each method) was
carried out before irradiation and then every 30 min after the oscillator had
been turned off for a period of 2 to 4 hr. In certain cases an additional
sample was taken 15 min after the beginning of irradiation. Petri cups with
the seeding were placed into a thermostat at a temperature of 37?C for 24 hr.
Then during the period of a day they were held at room temperature, after that
the number of colonies of microorganisms that had grown was counted. The
average results obtained from several parallel samples (separately according
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to the sedimentation and aspiration methods) were calculated. The data from
the aspiration method was used to calculate the number of bacteria 1 m3 of
air. The movement of people in the room was restricted during the experiment.
The temperature, humidity and atmospheric pressure were recorded.
The effect of millimeter wave on the microflora of the air in a room
was investigatedo
--as a function of the duration of irradiation for a constant wave-
length and constant power;
--as a function of the wavelength for constant power and the same
irradiation time.
? The experiment showed that when a room is. irradiated with millimeter
waves the number of bacteria in the air is reduced radically, especially dur-
ing the first hour (Fig. 3**, Curve 1). The number of bacteria after 1.5 hr
of irradiation is decreased significantly; it is difficult to determine the
further change in the number of bacteria reliably using the adopted method.
In order to compare the efficiency of the irradiation and to intro-
duce corrections for natural precipitation of bacterial aerosol, control ex-
periments were carried out without irradiation) under the same conditions. The
decrease in the number of microorganisms in the air of a closed room in the
control experiment is smoother (Fig. 3, Curve 2).
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During the experiments it was discovered that the bactericidal
action of millimeter waves is not identical in the interval of 5.7 to 7.1 mm.
Several maxima and minima were observed. (Insert Figs. 3 and 4, RP 135; Fig. 3.
Reduction of the Number of Microorganisms in the Air of a Laboratory Room as
a Function of Time (Sedimentation Method); (1) Experiment With Irradiation (a =
clst, P = const); (2) Control Experiment Without Irradiation; Sirr/So--ratio be-
tween the number of microorganisms after irradiation as the original number.
Fig. 4. Dependence of the Batericidal Action of Millimeter Radiation on Wave-
length: (1 and 2) Experiment With Irradiation (P = 100 mW, irrad.iation time
1 hr); (3 and 4) Control Experiment Without Irradiation; the Solid Curves Cor-
respond to the Aspiration Method, and the Dash Curves Correspond to the Sedimen-
tation Method.
(Footnote bottom of page RP 135)
* Curves 1 and 2 represent the results of several measurements at each point.
Curves 3 and 4 are the average data for five control experiments without ir-
radiation, which characterize the magnitude of. the reduction in the concentra-
tion of microorganisms in the air in 1 hr associated with the natural precipi-
tation of particles of bacterial aerosol.
Figure 4* shows the dependence of the bactericidal action of milli-
meter waves on wavelength in the 6.3 to 6.9 mm (the irradiation time was 1 hr,
and the power was approximately 100 mW). The intervals of shorter wavelengths
(5.7 to 6.3 mm) and longer wavelengths (6.9 to 7.1 mm) were not adequately
investigated. Here maxima and minima of the efficiency were likewise observed,
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but the individual points were obtained as a result of single measurements
and require further refinement. Therefore, the curves for this interval are
not shown in the figure.
As a result of the work which was carried out, the following has
been established:
(1) Millimeter waves exert a bactericidal action with regard to the
microflora in the air of a laboratory room;
(2) .The efficiency of the bactericidal action depends on wavelength
and irradiation time.
The results obtained register the main character of the effect of
which millimeter waves have on microorganisms, b"ut they also require refinement,
since many extraneous factors are superimposed on the characteristics of pain
in a room: the magnitude of the original bacterial background, the change in
the quantitative composition of the microorganisms due to natural precipitation
and reverse diffusion of bacterial aerosol, change in the qualitative composi-
tion of the microflora, fluctuations of the humidity and temperature of the air,
movement of people in the room, and others. Many questions. may be refined by
performing work on pure bacterial cultures. From this point of view, work which
has been done may be treated as the first stage of a large cycle of investiga-
tions.
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[1] Pick up from the Russian.
[2] Pick up from the Russian.
[3] V. F. Glibin. Decontamination of Water by Means of Ultra- High-Frequency
Currents. Public Health, No. 11, p. 41 (1952).
[4] Pick up from the Russian.
[5] N. I. Schastnaya. The Effect of Super- High-Frequency Electromagnetic
Waves on Microorganisms. Transactions of the Kharkov Medical Institute,
Vol. 15, No. 30, p. 239 (1957).
[6] P. I. Schastnaya. The Effect of Microwave on Escherichia cola. Transac-
tion of the.Khar'kov Medical Institute, No. 46, p. 359 (1958).
[7] Pick up from the Russian.
Submitted for publication May 17, 1966.
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