Iridium exposure increases c-fos expression in the mouse brain only at levels which likely result in tissue heating

With the rapid development of wireless communication technology over the la st 20 years, there has been some public concern over possible health effect s of long-term, low-level radiofrequency exposure from cellular telephones. As an initial step in compiling a database for risk analysis by government agencies, the effects of l-h exposure of mice to a 1.6-GHz radiofrequency signal, given as either a continuous wave or pulse modulated at 11 Hz with a duty cycle of 4:1 and a pulse duration of 9.2 ms (IRIDIUM), on c-fos gene expression in the brain was investigated. The IRIDIUM signal is the operat ing frequency for a ground-to-satellite-to-ground cellular communications w eb which has recently become fully operational, and was named as such due t o the original designed employment of the same number of low orbiting satel lites as there are electrons orbiting the nucleus of an iridium atom. The e xpression of c-fos was not significantly elevated in the brains of mice unt il exposure levels exceeded six times the peak dose and 30 times the whole body average dose as maximal cellular telephone exposure limits in humans. Higher level exposure using either continuous wave (analog) or IRIDIUM sign als elevated c-fos to a similar extent, suggesting no obvious pulsed modula tion-specific effects. The pattern of c-fos elevation in limbic cortex and subcortex areas at high er exposure levels is most consistent with a stress response due to thermal perception coupled with restraint and/or neuron activity near thermoregula tory regions, and not consistent with any direct interaction of IRIDIUM ene rgy with brain tissue. (C) 1999 IBRO. Published by Elsevier Science Ltd.