THE EFFECT OF PULSED AND SINUSOIDAL MAGNETIC-FIELDS ON THE MORPHOLOGYOF DEVELOPING CHICK-EMBRYOS

Several investigators have reported robust, statistically significant results that indicate that weak (similar to 1 mu T) magnetic fields (M Fs) increase the rate of morphological abnormalities in chick embryos. However. other investigators have reported that weak MFs do not appea r to affect embryo morphology at all. We present the results of experi ments conducted over five years in live distinct campaigns spanning se veral months each. In four of the campaigns, exposure was to a pulsed magnetic field (PMF); and in the final campaign, exposure was to a 60 Hz sinusoidal magnetic field (MF). A total of over 2500 White Leghorn chick embryos were examined. When the results of the campaigns were an alyzed separately, a range of responses was observed. Four campaigns ( three PMF campaigns and one 60 Hz campaign) exhibited statistically si gnificant increases (P greater than or equal to 0.01), ranging from 2- fold to 7-fold, in the abnormality rate in MF-exposed embryos. In the remaining PMF campaign, there was only a slight (roughly 50%), statist ically insignificant (P = 0.2) increase in the abnormality rate due to MF exposure. When the morphological abnormality rate of all of the PM F-exposed embryos was compared to that of all of the corresponding con trol embryos, a statistically significant (P greater than or equal to. 001) result was obtained, indicating that PMF exposure approximately d oubled the abnormality rate. Likewise, when the abnormality rate of th e sinusoid-exposed embryos was compared to the corresponding control e mbryos, the abnormality rate was increased (approximately tripled). Th is robust result indicates that weak EMFs can induce morphological abn ormalities in developing chick embryos. We have attempted to analyze s ome of the confounding factors that may have contributed to the lack o f response in one of the campaigns. The genetic composition of the bre eding stock was altered by the breeder before the start of the nonresp onding campaign. We hypothesize that the genetic composition of the br eeding stock determines the susceptibility of any given hock to EMF-in duced abnormalities and therefore could represent a confounding factor in studies of EMF-induced bioeffects in chick embryos. (C) 1997 Wiley -Liss, Inc.