Repeated exposure to nanosecond high power pulsed microwaves increases cancer incidence in rat.

René De Seze,Anthony Lecomte,Caroline Fonta,Emmanuelle Maillot-Maréchal,Franck Robidel,Carole Poutriquet,Christelle Gamez,Christophe Egles

doi:10.1371/journal.pone.0226858

Abstract

High-power microwaves are used to inhibit electronics of threatening military or civilian vehicles. This work aims to assess health hazards of high-power microwaves and helps to define hazard threshold levels of modulated radiofrequency exposures such as those emitted by the first generations of mobile phones. Rats were exposed to the highest possible field levels, under single acute or repetitive exposures for eight weeks. Intense microwave electric fields at 1 MV m-1 of nanoseconds duration were applied from two sources at different carrier frequencies of 10 and 3.7 GHz. The repetition rate was 100 pps, and the duration of train pulses lasted from 10 s to twice 8 min. The effects on the central nervous system were evaluated, by labelling brain inflammation marker GFAP and by performing different behavioural tests: rotarod, T-maze, beam-walking, open-field, and avoidance test. Long-time survival was measured in animals repeatedly exposed, and anatomopathological analysis was performed on animals sacrificed at two years of life or earlier in case of precocious death. Control groups were sham exposed. Few effects were observed on behaviour. With acute exposure, an avoidance reflex was shown at very high thermal level (22 W kg-1); GFAP was increased some days after exposure. Most importantly, with repeated exposures, survival time was 4-months shorter in the exposed group, with eleven animals exhibiting a large sub-cutaneous tumour, compared to two in the sham group. A residual X-ray exposure was also present in the beam (0.8 Gy), which is probably not a bias for the observed result. High power microwaves below thermal level in average, can increase cancer prevalence and decrease survival time in rats, without clear effects on behaviour. The parameters of this effect need to be further explored, and a more precise dosimetry to be performed.

Highlights

High power microwaves (HPM) are used to inhibit the electronic systems of threatening vehicles
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Concern has arisen as to whether HPM could lead to health hazards for operators of emitting systems and for staff members exposed in targeted vehicles

Summary

Introduction

High power microwaves (HPM) are used to inhibit the electronic systems of threatening vehicles. Concern has arisen as to whether HPM could lead to health hazards for operators of emitting systems and for staff members exposed in targeted vehicles. Studies performed with a whole-body specific absorption rate (SAR) above the thermal threshold of 4 W kg-1 have shown biological effects. Another paper by Dorsey et al [13] on carcinogenesis used ultrawideband (UWB) exposure. Concerning cancer, Zhang et al [14] and Devyatkov et al [10] reported protective effects at levels above thermal threshold, with smaller tumours and a 30% increase of survival rate in the exposed group. Focusing on UWB exposures, several years after Seaman’ article [15], a recent review by Schunck et al reported only one new paper in 2009, and no other effects on cancer were reported [16]. Durations of exposure in those studies were often short

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