Medical/biological study (experimental study)

Chronic exposure to a 1.439 GHz electromagnetic field used for cellular phones does not promote N-ethylnitrosourea induced central nervous system tumors in F344 rats med./bio.

By: Shirai T, Kawabe M, Ichihara T, Fujiwara O, Taki M, Watanabe S, Wake K, Yamanaka Y, Imaida K, Asamoto M, Tamano S

Published in: Bioelectromagnetics 2005; 26 (1): 59-68

Aim of study (acc. to author)

To evaluate whether a 2 year exposure to an electromagnetic field equivalent to that generated by cellular phones can accelerate tumor development in the central nervous system of rats (brain tumorigenesis was initiated by an intrauterine exposure to N-ethylnitrosourea on gestational day 18).

Endpoint

cancer: brain and spinal cord tumors

Exposure

- TDMA
- mobile communications
- PDC

Exposure	Parameters
Exposure 1: 1.439 GHz Modulation type: pulsed Exposure duration: repeated daily exposure, 90 min/day, 5 days/week for 104 weeks	SAR: 2 W/kg average over mass (brain) SAR: 6 W/kg peak value (brain) (time peak) SAR: 0.67 W/kg average over mass (brain) SAR: 2 W/kg peak value (brain) (time peak) SAR: 0.4 W/kg average over mass (whole body)

General information

A total of 500 pups were divided into five groups: untreated control, ENU alone, ENU + EMF (two exposure levels + sham). N.B.: ENU treatment was done to their mothers on gestational day 18!

Exposure 1

Main characteristics

Frequency	1.439 GHz
Type	electromagnetic field
Exposure duration	repeated daily exposure, 90 min/day, 5 days/week for 104 weeks

Modulation

Modulation type	pulsed
Additional info	TDMA signal for the Japanese PDC (Personal Digital Cellular) system

Exposure setup

Exposure source	monopole
Distance between exposed object and exposure source	30 mm
Chamber	The exposure box was 90 x 90 x 60 cm, the inside walls except for the ceiling being covered with electromagnetic absorber. Ten boxes were used simultaneously.
Setup	Ten rats, fixed individually in plastic tubes (four different sizes), were set on a disk-shaped plate (65 cm in diameter) with their nose towards the center. A quarter-wavelength monopole antenna on the ceiling of the exposure box fitted in the center of the disk-shaped plate. The distance between the antenna and each rat nose was 30 mm and the distance between the ceiling and the rat back was 5 mm.
Additional info	Plastic holders used were of four different sizes (inner diameter 4.0 cm, 4.7 cm, 5.5 cm, and 6.2 cm). If rats deceased, dummy rats were used to maintain symmetry and scheduled SAR in the exposure box.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
SAR	2 W/kg	average over mass	measured and calculated	brain	-
SAR	6 W/kg	peak value	measured and calculated	brain	time peak
SAR	0.67 W/kg	average over mass	measured and calculated	brain	-
SAR	2 W/kg	peak value	measured and calculated	brain	time peak
SAR	0.4 W/kg	average over mass	estimated	whole body	-

Measurement and calculation details

SAR distributions in rats were evaluated both by numerical dosimetry using the FDTD method and experimental dosimetry using a thermographic camera. Since rats grew from under 100 g to over 400 g during this experiment, three original rat models based on X-ray computed tomography data of 126, 263, and 359 g rats in plastic holders were made and then other sized models were created by numerical scaling.

Exposed system:

animal
rat/Fischer 344
partial body: head

Methods Endpoint/measurement parameters/methodology

cancer: brain and spinal cord tumors; leukemia
morphol./histopathol. changes: histological examination of all organs and observable lesions (hematoxylin-eosin stain)
endocrine changes: corticosterone, melatonin, and ACTH (adrenocorticotropic hormone) content
body and organ weights; food consumption; survival rate; hematology analysis

Investigated system:

tissue slices
blood samples
investigation on living organism

Investigated organ system:

CNS, heart, liver, kidney, spleen, pituitary gland, adrenal glands, testes, ovary

Time of investigation:

during exposure
after exposure

Main outcome of study (acc. to author)

There were no differences between the groups in body weights, food consumption, and survival rates. No increase in the incidences per group of brain and/or spinal cord tumors, either in the males or females, was revealed in the exposed rats. Additionally, no clear changes in tumor types were evident.
In conclusion, under the present experimental conditions, 1.439 GHz electromagnetic field exposure to the heads of rats for a 2 year period was not demonstrated to accelerate or affect N-ethylnitrosourea initiated brain tumorigenesis

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Ministry of Public Management, Home Affairs, Posts and Telecommunications, Japan

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