Exposure of domestic quail embryos to extremely low frequency magnetic fields

Four hundred domestic quail eggs (Coturnix coturnix japonica) were used to study the possible teratogenic effects of extremely low frequency magnetic fields (ELF-MFs) on early embryonic development. Ten females were selected from a flock on the basis of their high fertility rate and low number of spontaneous abnormalities and they were selectivity maintained in nesting-boxes in a room where feeding and environmental conditions were carefully controlled. All the eggs used in the experiments were filiated by their progemtor, and were handled in the same way from the time they were laid until the point at which they were placed in a specially designed incubator, which dramatically reduces the stray magnetic fields produced by the heating system. Twenty eggs per experiment (10 control and 10 exposure) were placed in two different areas within the incubator. For each experiment two eggs from each of the 10 females were used. These were placed pairwise in the same position in the incubation areas (one in the control area and one in the exposure area). The first 12 experiments (240 eggs in total) were sham (ELF-MFs source turned off) in order to identify the variability of test quantities. The last eight experiments (160 eggs in total) involved magnetic fields (continuous bipolar square signal, rise and fall time 4 microseconds, in Helmholtz' coils) and they were divided into two exposure groups: the first four experiments at 50-Hz frequency and the last four at 100-Hz frequency. The magnetic flux density was different for each experiment within each frequency group, but the same sequence was always used: 0.2, 1.2, 2.2, 3.2 microtesla. The number of abnormal embryos found in the area exposed to 100 Hz was significantly higher than for their controls (Chi-square test, p = 0.048) but this difference was not significant for the 50-Hz group (p = 0.232). An ANOVA test was significant for the magnetic field variable (p < 0.05). A higher number of dead embryos was observed in the two groups of exposed eggs. Finally, a gross examination of the external morphology of the abnormal exposed embryos showed a high percentage of abnormalities of the nervous system, particularly at the cephalic level.