Löscher et al53 studied the effects of a 24 h/day, 7 days/week, and 3-month exposure to magnetic fields on female rats bearing DMBA-induced mammary tumors; the field intensities were similar to the domestic exposures recorded close to electric power facilities. Whereas a significant decrease of blood melatonin concentrations was observed with 1 μT, no influence on the development of the mammary tumors could be put in evidence. Table lb presents data on different animal species reporting the

lack of effect of R428 ELF-EMF on the concentrations of pineal or blood melatonin and on the urinary concentration of 6-sulphatoxymelatonin, the main metabolite of Inhibitors,research,lifescience,medical the hormone. These reports were either inconsistent

or failed to show any effect of ELF-EMF in species as different as rats or mice,64-73 sheep,74,75 baboons,76 Djungarian hamsters,58,77 cows or heifers,78-80 and kestrels.81,82 The comparison Inhibitors,research,lifescience,medical of Table la (effects on melatonin) and Table lb (lack of effects on melatonin) clearly shows that a number of these studies resulted in inconsistent data, even when the data were replicated by the same team with the same protocol and characteristics of exposure.48,49,57,58,83,84 Last, some authors studying the effects of exposure to ELF-EMF of various biological Inhibitors,research,lifescience,medical systems such as isolated pineal glands85-90 or MCF-7 cells91-96 were unable to arrive at definite conclusions (Table II). Table II. Effects of magnetic fields on various biological systems in vitro. Inhibitors,research,lifescience,medical NE, norepinephrine; Mel: melatonin Human studies Much of the evidence for the melatonin hypothesis is based on data obtained in rodents with a 25% to 40% reduction in Inhibitors,research,lifescience,medical the hormonal concentration, though, as shown above, results on the effects of ELF-EMF in rodents and higher mammals provided controversial results. Since the 1990s several research papers have documented the effects of ELF-EMF on the secretion

of melatonin in humans. Most research published has involved an acute exposure (from 30 min to 4 days on average) of healthy volunteers to ELF-EMF with different exposure characteristics (Tables IIIa and IIIb). The data on humans are controversial, since of the papers published about one third reported a decrease in melatonin secretion97-107 with, however, Florfenicol some comments to be mentioned such as the lack of evidence for a dose-response,97 or a decrease not exclusively related to ELF-EMF and found in some particular subgroups98-107 (Table IIIa). In contrast to the previous ones, two thirds of the reports failed to find any effect of ELF-EMF on melatonin secretion in humans ( Table IIIb). 108-130Most work published on humans dealt with short-term exposure for evident ethical reasons.