Mayo 2000

RF radiation and brain function in humans.

Preece and colleagues previously reported that RF radiation in the cell phone range was associated with a decrease in choice reaction time, one of 15 tests they carried out on volunteers (see "What's New Archive" - February 2000). Now a new study by Koivisto and colleagues from Finland shows that exposure to RF fields speeded up response times in 3 out of 12 tasks performed by volunteers. Interestingly, the choice reaction time (i.e. the one Preece found to be affected for an analog signal) was not one of the tasks affected in this study. The authors state that the mechanism of the observed changes remains open to conjecture, but like Preece they postulate that "a slight temperature increase in brain tissue is one of the candidates".

This paper is discussed further in the Section on "Research - Clinical - cognitive function".

Reference: Koivisto M, Revonsuo A, et al. Effects of 902 MHz electromagnetic field emitted by cellular telephones on response times in humans. Neuroreport 1999; 11: 413-415.

Radiofrequency radiation and brain tumours in rats.

Dr. Roti Roti and his colleagues report that they found no effect of radiofrequency fields on the growth of brain tumours in rats. The animals were exposed to RF fields similar to those used in cellular telephones. The average specific absorption rates were 0.75 W/kg. The animals were exposed to the RF field for four hours a day, five days a week, starting four weeks prior to and up to 150 days after the implantation of tumour cells into the brain. There were no differences between exposed and non-exposed animals in median survival or mortality rates.

Reference: Higashikubo R, Culbreth VO, et al. Radiofrequency electromagnetic fields have no effect on the in vivo proliferation of the 9L brain tumor. Radiation Research 1999; 152: 665-671.

Radiofrequency radiation and spatial memory function in animals.

Two recent studies explore the effect of RF radiation on spatial memory in animals.

Drs. Wang and Lai from the University of Washington reported in a recent article that microwave radiation caused impairment of spatial memory in rats. They exposed the animals to 2,450 MHz pulsed radiofrequency radiation for 1 hour before each of six sessions, in which they were trained to locate a submerged platform in a circular water maze. The water was clouded by powdered milk, and the rats had to locate the platform by memory rather than visually. The exposed animals took significantly longer, by the final session, to find the platform, compared with non-exposed controls. In a probe session in which the platform was removed, the exposed animals spent less time in the quadrant of the maze where the platform had been located. The authors state that "a possibility is that the behavioral effect observed was caused by the auditory effect of the pulsed radiation" and mention that the specific absorption of the pulses was definitely above the hearing threshold. In addition, the average whole-body specific absorption rate was 1.2 W/kg, which is three times higher than the 0.4 W/kg allowed by Health Canada's Safety Code 6 for whole body exposure of the general population. It is reasonable to assume that the peak SAR might have been at a level high enough to induce a thermal effect.

Reference: Wang B, Lai H. Acute exposure to pulsed 2450 - MHz microwaves affects water-maze performance of rats. Biolectromagnetics 2000; 21: 52 - 56.

The second study, by Sienkiewicz and colleagues, failed to show deficits in the performance of a spatial learning task in mice exposed to RF radiation simulating a digital wireless phone (GSM) signal. The mice were exposed to a 900 MHz field pulsed at 217 HZ for 45 minutes each day for 10 days. The average whole-body SAR was 0.05 W/kg. The performance of the exposed mice in an 8-arm radial maze was compared with sham-exposed controls. In this experiment animals foraged for food at the end of arms of the maze. There were no differences in choice accuracy or in total times to complete the task. The average SAR was much lower than in the study by Wang and Lai. The authors plan other studies to examine the effects of other SARs.

Reference: Sienkiewicz Z, Blackwell RP, Haylock RGE, Saunders RD, et al. Low-level exposure to pulsed 900 MHz microwave radiation does not cause deficits in the performance of a spatial learning task in mice. Bioelectromagnetics 2000;21:151-158.

More on cell phones and EEGs

Freude and her colleagues report a new study on the effects of EMF from cellular phones on EEGs in humans.

In the latest study changes were found in the EEGs of volunteers while they performed one type of task, but not during two other tasks. The authors state that the results suggest "a selective EMF effect on particular aspects of human information processing, but did not indicate any influence on human performance, well-being and health."

More details of the study are given in the "Research - Clinical -EEG".

Reference: Freude G, Ullsperger P, Eggert S, Ruppe I. Microwaves emitted by cellular telephones affect human slow brain potentials. Eur J Appl Physiol 2000;81:18-27.

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