Medical/biological study (experimental study)

Exposure to radiofrequency radiation induces oxidative stress in duckweed Lemna minor L med./bio.

By: Tkalec M, Malaric K, Pevalek-Kozlina B

Published in: Sci Total Environ 2007; 388 (1-3): 78-89

Aim of study (acc. to author)

To study the physiological responses of the duckweed after exposure to radiofrequency electromagnetic fields, and in particular, to clarify the possible role of oxidative stress.

Background/further details

Cadmium and heat (42°C, 2h) were used for positive controls.

Endpoint

oxidative stress in plants

Exposure

- RF field

Exposure	Parameters
Exposure 1: 400–900 MHz Modulation type: CW Exposure duration: continuous for 2 h	electric field strength: 10 V/m power density: 0.3 W/m² electric field strength: 23 V/m power density: 1.4 W/m² electric field strength: 41 V/m power density: 4.2 W/m² electric field strength: 120 V/m power density: 38.2 W/m²
Exposure 2: 400–900 MHz Modulation type: CW Exposure duration: continuous for 2 hr or 4 hr	electric field strength: 23 V/m power density: 1.4 W/m²

Exposure 1

Main characteristics

Frequency	400–900 MHz
Type	electromagnetic field
Charakteristic	guided field
Exposure duration	continuous for 2 h
Additional info	400 and 900 MHz were used

Modulation

Modulation type	CW

Exposure setup

Exposure source	GTEM cell [Tkalec et al., 2005 and Malaric et al., 2005]
Setup	Five plastic Petri dishes were placed in the GTEM cell in the same plane but perpendicular to the field. The area where plants were placed had the most uniform field distribution (±0.1 dB) as tested with an electric probe.
Sham exposure	A sham exposure was conducted.
Additional info	The temperature inside the GTEM cell and on the plant surface did not vary by more than ±0.1 °C.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
electric field strength	10 V/m	-	measured	-	-
power density	0.3 W/m²	-	-	-	-
electric field strength	23 V/m	-	measured	-	-
power density	1.4 W/m²	-	-	-	-
electric field strength	41 V/m	-	measured	-	-
power density	4.2 W/m²	-	-	-	-
electric field strength	120 V/m	-	measured	-	-
power density	38.2 W/m²	-	-	-	-

Exposure 2

Main characteristics

Frequency	400–900 MHz
Type	electromagnetic field
Charakteristic	guided field
Exposure duration	continuous for 2 hr or 4 hr
Additional info	400 and 900 MHz were used

Modulation

Modulation type	CW

Exposure setup

Exposure source	same setup as exposure 1

Parameters

Measurand	Value	Type	Method	Mass	Remarks
electric field strength	23 V/m	-	measured	-	-
power density	1.4 W/m²	-	-	-	-

Reference articles

Tkalec M et al. (2005): Influence of 400, 900, and 1900 MHz electromagnetic fields on Lemna minor growth and peroxidase activity
Malaric K et al. (2005): Immunity measurements of TV and FM/AM receiver in GTEM-cell

Exposed system:

plant
Lemna minor L. (duckweed)
whole body

Methods Endpoint/measurement parameters/methodology

oxidative stress (lipid peroxidation (MDA formation); hydrogen peroxide content; enzyme activities (catalase, pyrogallol, ascorbate peroxidase); isoenzyme pattern of antioxidative enzymes; HSP70 expression (Western blot))

Investigated system:

isolated bio./chem. substance
plant homogenates/supernatants

Time of investigation:

after exposure

Main outcome of study (acc. to author)

At 400 MHz, lipid peroxidation and hydrogen peroxide content were significantly enhanced in duckweed exposed to electromagnetic fields of 23 and 120 V/m, while other exposures did not have an effect.
Compared to the controls, catalase enzyme activity increased after most exposure treatments while pyrogallol and ascorbate peroxidase enzyme activities were not changed. Exceptions were reduced pyrogallol and ascorbate peroxidase enzyme activity after longer exposure at 23 V/m and increased pyrogallol enzyme activity after exposures at 10 and 120 V/m.
By contrast, at 900 MHz almost all exposure treatments significantly increased lipid peroxidation and hydrogen peroxide content but mostly decreased pyrogallol enzyme activity and did not affect catalase enzyme activity. Exceptions were exposures to a modulated electromagnetic field and to the electromagnetic field of 120 V/m which increased pyrogallol and catalase enzyme activity. At this frequency ascorbate peroxidase activity was significantly decreased after exposure at 10 V/m and longer exposure at 23 V/m but it increased after a shorter exposure at 23 V/m.
At both frequencies no differences in isoenzyme patterns of antioxidative enzymes or HSP70 level were found between control and exposed plants.
The data showed that non-thermal exposure under these experimental conditions induced oxidative stress in duckweed as well as unspecific stress responses, especially of antioxidative enzymes. However, the effects markedly depended on the electromagnetic field frequencies applied as well as on other exposure parameters (field strength, modulation and exposure time).

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Ministry of Science, Education and Sports, Republic of Croatia

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Exposure to radiofrequency radiation induces oxidative stress in duckweed Lemna minor L med./bio.

Aim of study (acc. to author)

Background/further details

Endpoint

Exposure

Exposure 1

Main characteristics

Modulation

Exposure setup

Parameters

Exposure 2

Main characteristics

Modulation

Exposure setup

Parameters

Reference articles

Methods Endpoint/measurement parameters/methodology

Main outcome of study (acc. to author)

Study funded by

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