Does evening exposure to mobile phone radiation affect subsequent melatonin production?

Purpose: To test whether exposure to the emissions from a digital mobile phone handset prior to sleep alters the secretion of melatonin. Materials and methods: In a double-blind cross-over design, 55 adult volunteers were both actively exposed or sham-exposed ( in random order on successive Sunday nights) to mobile phone emissions for 30 min (0.25 W average power). Urine collection occurred immediately prior to retiring to bed and on rising the next morning. Melatonin output was estimated from principal metabolite concentrations (6-sulphatoxymelatonin (aMT6s) via radioimmunoassay), urine volumes and creatinine concentrations. Results: Total melatonin metabolite output (concentration x urine volume) was unchanged between the two exposure conditions ( active 14.1 +/- 1.1 mu g; sham 14.6 +/- 1.3 mu g). The pre- and post-bedtime outputs considered separately were also not significantly different, although the pre- bedtime value was less for active versus sham exposure. When melatonin metabolite output was estimated from the ratio of aMT6s to creatinine concentrations, the pre- bedtime value was significantly less ( p = 0.037) for active compared to sham. Examination of individual responses is suggestive of a small group of 'responders'. Conclusions: Total nighttime melatonin output is unchanged by mobile phone handset emissions, but there could be an effect on melatonin onset time.