CHICK-EMBRYO DEVELOPMENT CAN BE IRREVERSIBLY ALTERED BY EARLY EXPOSURE TO WEAK EXTREMELY-LOW-FREQUENCY MAGNETIC-FIELDS

Several reports have shown that weak, extremely-low-frequency (ELF), p ulsed magnetic fields (PMFs) can adversely affect the early embryonic development of the chick. In this study, freshly fertilized chicken eg gs were exposed during the first 48 h of postlaying incubation to PMFs with 100 Hz repetition rate, 1.0 mu T peak-to-peak amplitude, and 500 mu s pulse duration. Two different pulse waveforms were used, having rise and fall times of 85 mu s (PMF-A) or 2.1 mu s (PMF-B). It has bee n reported that, with 2 day exposure, these fields significantly incre ase the proportion of developmental abnormalities. In the present stud y, following exposure, the eggs were allowed to incubate for an additi onal 9 days in the absence of the PMFs. The embryos were taken out of the eggs and studied blind. Each of the two PMF-exposed groups showed an excess in the percentage of developmental anomalies compared with t he respective sham-exposed samples. This excess of anomalies was not s ignificant for the PMF-A-treated embryos (P = 0.173), whereas it was s ignificant for the PMF-B-exposed group (P = 0.007), which showed a par ticularly high rate of early embryonic death. These results reveal tha t PMFs can induce irreversible developmental alterations and confirm t hat the pulse waveform can be a determinant factor in the embryonic re sponse to ELF magnetic fields. The data also validate previous work ba sed on the study of PMFs' effects at day 2 of embryonic development un der field exposure. (C) 1994 Wiley-Liss, Inc.