Temperature changes in chicken embryos exposed to a continuous-wave 1.25 GHz radiofrequency electromagnetic field.

A total of 550 fertile chicken eggs (White Leghorn) were exposed to a radiofrequency (RF) electromagnetic field of 1.25 GHz (continuous wave) at six different power flux densities in the range of 9.0-0.75 mW/cm(2). The eggs were exposed either continuously throughout the whole 21 days of incubation (long-term exposure) or in a short-term exposure (1-2 h/day). The temperatures of the embryonic tissue and the amniotic fluid, respectively, were measured with inserted temperature probes. This study was designed to investigate the relationship between exposure and temperature changes in exposed tissues, without considering biological and medical effects. This knowledge is of general interest for studies of nonthermic teratological or embryo-lethal effects of exposure to electromagnetic fields (EMFs). Throughout the entire 21 days of embryonic development, the mean temperature increases in the eggs during the exposure were found to be up to 0.25 degrees C for a power flux density of 1.25 mW/cm(2) and increased to 2.3 degrees C for 9.0 mW/cm(2). The corresponding maximum whole-body SARs for the embryos over the 21 days of embryonic development were 1.45 and 10.44 W/kg, respectively. At 0.75 mW/cm(2) (0.87 W/kg) the extent of the RF-field induced hyperthermia was within the measurement accuracy (+/-0.1 degrees C) of the temperature probes used in the tests. The field-induced temperature increase was greatest in the first week of incubation and was less pronounced in the last (third) week before hatching. In both the short- and the long-term exposures, the temperature of the exposed tissue and the amniotic fluid, respectively, reached its maximum (asymptotic) approximately 40-50 min after the RF field was switched on. After the field was switched off, the temperature inside the exposed eggs returned to its initial value within 40-50 min.

Effects of light or different earth-strength magnetic fields on the nocturnal melatonin concentration in a migratory bird.

The effects of light or artificial earth-strength magnetic fields (MFs) on pineal melatonin synthesis were studied in the Pied Flycatcher, a migratory bird. Serum melatonin levels exhibited a circadian rhythm with the highest values during the night and lowest during the day. Nocturnal melatonin synthesis was significantly diminished following exposure to light during the night. It was reduced by a similar extend after exposure to an artificial MF that simultaneously reversed the horizontal component of the field and altered its intensity. In contrast, melatonin levels were not significantly changed when the bird was exposed to a MF that changed only in intensity or direction.