Bartsch H, et al. (2002)
This study used female Sprague-Dawley rats. When the animals were 51 days old they were given a single dose of dimethylbenz(a)anthracene (DMBA), which induces mammary tumours. They were then exposed to a GSM-like signal (900 MHz pulsed at 217 Hz), power flux density 100µW/cm² for 24 hours per day. The whole-body SAR was estimated to be 17.5-70 mW/kg for adult rats, and 32.5-130 mW/kg for young rats at the beginning of the study. Three experiments were done, and were started on the same day of three consecutive years. The only differences in the three experiments were in their ages at the time of purchase (38, 43, and 34 days respectively) and the number of days of acclimatization to the conditions of the facility (13, 8, and 17 days). The animals were unrestrained within their cages.
The animals were palpated weekly for the presence of mammary tumours. They were killed when tumours reached a diameter of 1-2 cm to allow for reliable histological diagnosis. In the third experiment an examiner blind to the exposure status of the animal did the palpation.
The overall results were that there was no statistically significant effect of RF-field exposure on tumour latency and that the cumulative tumour incidence was unaffected as well. In the first experiment, however, the median latency for the development of the first malignant tumour in each animal was significantly extended for RF-exposed animals compared to controls (278 days compared to 145 days). There were no such significant differences in latency in the other two experiments. The authors hypothesize that the length of the accommodation period may be related to the latency period, and that short accommodation periods may cause increased stress hormone secretion.
The authors state that the power flux density of 100 µW/cm² attained with the 13-15 W antennas in their experiment can be found at a distance of 6.3 m from a typical base station antenna of 200 w with 4 dB gain.
The incidence of malignant tumours in sham-exposed animals was high (79-91%) and one could argue that it would be difficult to demonstrate differences in the incidence rates in RF-exposed animals. There was, however, no trend to higher rates in the RF-exposed rats.