Heikkinen P, Kumlin T, Laitinen JT, Komulainen H, et al. (1999).
This study tested the effect of exposure to radiation on the production of melatonin from the pineal gland. There have been suggestions that suppression of melatonin secretion could promote the development of cancer. In this case the hormone production was measured by the urinary excretion of its main metabolic end product, 6-hydroxymelatonin sulfate (6-OHMS).
Female mice were randomized into six treatment groups, with 50 animals per group. Except for cage controls the mice were exposed at the start of the study to ionizing radiation, 4 Gy delivered as 3 subdoses at 1-week intervals. (The authors do not give an explanation for this exposure). In addition to cage controls, the other groups were those exposed to continuous RF radiation, pulsed RF, sham RF, ELF radiation and sham ELF. The ELF groups will not be discussed further in this summary.
The mice were exposed to the RF radiation for 1.5 hours per day, 5 days a week, for 17 months. In the continuous exposure, a NMT 900 hand-held mobile phone was used as a signal source. A modified GSM 900 phone produced the pulsed RF signal (1/8 duty cycle, 217 Hz repetition rate). The nominal SAR was 1.5 (1.0-1.8) W/kg for the continuous and 0.35 (0.20-0.45) W/kg for the pulsed signal. Urine was collected for 12 hours overnight from 24 animals per group at the end of the exposure period, and again one week later.
The nocturnal excretion of 6-OHMS per animal showed no significant differences between the groups exposed and sham-exposed to RF radiation.