Study type: Medical/biological study (experimental study)

Tumor promotion by exposure to radiofrequency electromagnetic fields below exposure limits for humans. med./bio.

Published in: Biochem Biophys Res Commun 2015; 459 (4): 585-590

Aim of study (acc. to author)

To replicate the pilot study of Tillmann et al., 2010, which investigated the tumour susceptibility in mice exposed to a radiofrequency signal for up to 72 weeks commencing with embryo-fetal exposure.

Background/further details

The previous study indicated a cocarcinogenic effect of lifelong UMTS exposure (4.8 W/m²) in female B6C3F1 offspring subjected to pretreatment with ethylnitrosourea. Compared to the pilot study, higher numbers of animals per group were used and two additional exposure levels were included.
Already mated female mice were randomly divided into five groups: 1.) cage control, 2.) sham exposure, 3.) SAR of 0.04 W/kg ("low"), 4.) SAR of 0.4 W/kg ("moderate") and 5.) SAR of 2 W/kg ("high"). Exposure and sham exposure of the potentially pregnant females started on day 6 post conception. Each group consisted originally of up to 64 female mice. The females were weighted at day 13 post conception and only the ones with the highest weight gains remained in the study (i.e. 32 pregnant dams per group, resepctively). The maternal treatment with ethylnitrosourea (intraperitoneal injection of 40 mg ENU per kg body weight) was carried out on day 14 post conception (except for cage control). Six days after birth, a litter standardisation was performed and afterwards three female offspring per cage and their mothers were maintained up to the weaning time point. After weaning, maternal mice were removed from the cages and the study was conducted using the three remaining female offspring (n=91-96 per group).
Mice were sacrificed when signs of disease were noted or the body weight showed a sudden drop. After 72 weeks, survival rates of the ENU-treated mice were below 25% and all remaining mice were sacrificed.

Endpoint

Exposure

Exposure Parameters
Exposure 1:
  • unspecified
Exposure duration: continuous for 23.3 h per day, 7 days per week, starting in utero up to 72 weeks
  • SAR: 0.04 W/kg
Exposure 2:
  • unspecified
Exposure duration: continuous for 23.3 h per day, 7 days per week, starting in utero up to 72 weeks
  • SAR: 0.4 W/kg
Exposure 3:
  • unspecified
Exposure duration: continuous for 23.3 h per day, 7 days per week, starting in utero up to 72 weeks

General information

local maximum SAR values could be as much as 3-5 times higher than the whole body SAR due to variations in animals and their position; SAR values were calculated for a reference configuration of three mice per cage (body weight of 20 g each); exposure was comparably homogeneous (standard deviations of the whole body SAR within the cages between 30% (adult animals) and 91% (pups) due to spatial electric field variations and movement of the animals; according to the authors, similar conditions than in Tillmann et al., 2010 were used

Exposure 1

Main characteristics
Frequency
  • unspecified
Type
Exposure duration continuous for 23.3 h per day, 7 days per week, starting in utero up to 72 weeks
Exposure setup
Exposure source
Chamber three mice per cage, 32 cages per exposure group
Setup exposure devices consisted of eight radial waveguides with 16 cages each, arranged in stacks of two and connected to power amplifiers and RF-generators; two waveguides (diameter of 2.2 m) per exposure group; to equalize the exposure between the 16 cages of each waveguide (max. 12% variation of the cages' mean electric field strengths), the cages were permuted every second day by one exposure section; electric fields inside the waveguides as well as temperatures were measured automatically
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 0.04 W/kg - calculated whole body -

Exposure 2

Main characteristics
Frequency
  • unspecified
Type
Exposure duration continuous for 23.3 h per day, 7 days per week, starting in utero up to 72 weeks
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
SAR 0.4 W/kg - calculated whole body -

Exposure 3

Main characteristics
Frequency
  • unspecified
Type
Exposure duration continuous for 23.3 h per day, 7 days per week, starting in utero up to 72 weeks
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
SAR 2 W/kg - calculated whole body -

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

The numbers of bronchiolo-alveolar adenoma in the lungs were significantly increased in all exposure groups compared to the sham exposure and the numbers of bronchiolo-alveolar carcinoma were significantly elevated in the group with moderate exposure. Additionally, in all exposure groups, significantly higher rates of hepatocellular carcinoma were found when compared to the sham exposure. The numbers of animals bearing lymphomas were significantly elevated at moderate exposure compared to sham exposed mice. The numbers of multiple tumors (bronchiolo-alveolar adenomas) were found to be significantly elevated at low exposure in comparison to the sham exposure. No significant differences between exposed and sham exposed groups were found regarding tumor rates in the brains, kidneys and spleens.
Survival rate was significantly lower in all ENU-treated groups in comparison to the cage control, but was not affected by exposure. The body weights from exposed or sham exposed animals were only slightly different from the cage control.
The animals were not infected with Helicobacter ssp.
The study confirms and extends the results of the pilot study of Tillmann et al., 2010 which indicated a tumor-promoting effect of lifelong exposure to radiofrequency electromagnetic fields in mice subjected to pretreatment with ethylnitrosourea. However, no clear dose-response relationship was found.

Study character:

Study funded by

Replicated studies

Comments on this article

Related articles