Annex 1: Study design and results of the first and second study phase

Phase 1 (five-day pilot study)

In the first phase, a five-day pilot study [1], the influence of different whole-body SARs on the body temperatures of young and adult B63F1 laboratory mice and young, adult, and pregnant Harlan Sprague-Dawley laboratory rats was investigated. To this end, five animals of each group were exposed to either GSM- or CDMA-modulated radio-frequency electromagnetic fields used by cell phones leading to whole-body SAR of 0, 4, 6, 8, 10, and 12 W/kg. The exposure was switched on and off every 10 minutes. In the exposure-free time, the temperature was measured using subcutaneously implanted temperature microchips.

Result

There was a significant increase in body temperature in pregnant rats and in adult male and female rats aged 5.5 (CDMA) or 9 months (GSM) starting from a SAR of 6 W/kg compared with sham-exposed control animals. At 6 W/kg, the average body temperature increase was below one degree Celsius. Higher SARs resulted in higher body temperature increases; these exceeded one degree Celsius at a SAR of 8 W/kg and led to death in adult male rats at a SAR of 12 W/kg within the first day. The smaller and lighter female rats showed a lower mean temperature increase. On the other hand, the smaller and lighter mice showed only sporadic increases in body temperature.

Phase 2 (28-day study)

Based on the results from the pilot study, young rats and mice were exposed at SAR values of 0, 3, 6, and 9 W/kg (rats) and 0, 5, 10, and 15 W/kg (mice) for 28 days in the second phase of the study. For rats and mice each, a shared control population (sham exposure, 0 W/kg) was used for GSM and UMTS modulation. The 28-day study was designed to determine the cumulative effects of repeated exposure to GSM- and CDMA-modulated radio-frequency fields at SAR values that did not result in increased mortality or excessively elevated animal body temperatures in the pilot study as well as to determine adequate SAR values for the two-year main study. In order to investigate a possible toxicity of radio-frequency fields in the case of in utero exposure as well as at an early postnatal time, pregnant female rats were exposed from the sixth day of gestation. The mice were between 5–6 weeks old at the beginning of the exposure. The effects of in utero or early postnatal exposure were not investigated in mice. The body weights and body temperatures of young rats and mice were measured on different days during the study. Body weights and temperatures were also measured in pregnant rats before birth and after birth during the lactation period.

Result

The investigations in the 28-day study at 6 and 9 W/kg showed an increased mortality of young rats between Day 1 and 4 after birth, a reduced body weight of the mothers and young male and female rats, and increased body temperatures in the mothers. In mice, no effects on mortality and body weight were observed. At some time points, significant body temperature increases in male mice and significant body temperature decreases in female mice were observed at 5, 10, and 15 W/kg.

At the end of the 28-day study, histopathological examinations were performed on the control animals as well as on the highest exposed animals on all relevant organs (approx. 40 organs).

Reference

[1] Wyde, M.E., et al., Effect of cell phone radiofrequency radiation on body temperature in rodents: Pilot studies of the National Toxicology Program's reverberation chamber exposure system. Bioelectromagnetics, 2018. 39(3): p. 190-199.