The aim of this study was to investigate the effect of exposure to RF radiation on the excretion of 6-hydroxymelatonin (6-OHMS) in rats. This substance is the main metabolic end product of melatonin.

Seventy-two rats were used. Six independent experiments were done, three with 1800 MHz exposure and three with 900 MHz. In each experiment, 12 rats were randomly divided into 2 groups. Six were exposed in a gigahertz transverse electromagnetic mode (GTEM) cell for 2 hours daily for 14 days. Six other animals were sham exposed in the same cell for 2 hours daily, either just before or just after the RF-exposed rats. Urine was collected from 12.00AM to 08.00 AM, on even days for the exposed group and on odd days for the control group.

The exposure was 900 MHz, 100µW/cm², or 1800 MHz, 20µW/cm², GSM radiation. The whole-body SAR was 0.009-0.012 W/kg at 900 MHz and 0.022-0.045 W/kg at 1800 MHz.

The results of three experiments were combined at each frequency. The 6-OHMS excretion was not statistically different between exposed animals and sham controls at either 900 or 1800 MHz.

These results are in agreement with those of Vollrath et al. (1997) and Heikkinen et al. (1999) at 900 MHz exposure. The present study is the first at 1800 MHz frequency.