Studies of 50 Hz circularly polarized magnetic fields of up to 350 μT on reproduction and embryo‐fetal development in rats: Exposure during organogenesis or during preimplantation

Abstract

Groups of mated female Sprague-Dawley rats were simultaneously exposed to 0 (sham exposed), 7, 70, or 350 microT (rms) circularly polarized 50 Hz magnetic fields (MF) for 22 h/day on gestational day 8-15, the period of rat fetal organogenesis (organogenesis study) or from day 0 to day 7 of gestation, the rat preimplantation period (preimplantation study). Developmental toxicity was assessed on gestational day 20. Identical experiments were repeated to confirm reproducibility of both studies. In both studies, statistically significant differences between exposed and sham exposed animals were observed in several measured parameters; however, these differences only appeared in one, but not both replicate experiments and generally at only an isolated exposure level. Because these differences were not reproducible and did not show a dose response relationship, they were not considered related to MF exposure. In the organogenesis study, lower kidney weights of dams were seen at 70 and 350 microT in Experiment 1. Lower dam liver weights and lower mean body weights of viable female and male fetuses were seen at 70 microT in Experiment 2. Otherwise, there were no differences in these parameters or in group means for fetal loss after implantation, number of viable fetuses, fetal body weight and sex ratio, incidences of external, visceral, and skeletal abnormalities or variations, or tissue abnormalities after histopathological examination. In the preimplantation study, dam health and indices for reproduction and embryo-fetal development, including pre or postimplantation loss, number and body weight of live fetuses, and sex ratio, external, skeletal abnormalities and variations, and skeletal ossification did not differ. Dam inorganic phosphorous concentration at 350 microT was elevated in one experiment and depressed in another. In one experiment, visceral abnormalities, primarily thymic remnant in neck and accessory liver lobe, were increased in the 7 microT group. Based on these results from two studies, we conclude that circularly polarized 50 Hz MF exposure of up to 350 microT during the fetal organogenesis or during the preimplantation period does not affect reproduction and embryo-fetal development in Sprague-Dawley rats.

Low dose magnetic fields do not cause oxidative DNA damage in human placental cotyledons in vitro

“…Similar negative results were described by Negishi et al [28] in rats following exposure to dose levels between 0.007 mT to 0.35 mT during days 8-15 of gestation. On the contrary, the exposure of rats of both sexes to 0.25 mT (50 Hz) for 90 days before mating showed some adverse effects on fertility, comprising an increased number of resorptions as well as a significantly decreased number of implantations and living fetuses per litter.…”

Developmental toxicity evaluation of ELF magnetic fields in Sprague–Dawley rats

“…The results suggested by others [Rommereim et al, 1996;Ryan et al, 1996], in which dams were exposed at the field strengths of 0.2 or 1 mT (2 or 10 G), showed consistency with our results. The recent report publi-shed by Negishi et al [2002] also showed that circularly polarized 50 Hz MF exposure of up to 350 mT during pregnancy did not affect reproduction and embryo-fetal development in rats. In contrast, others reported that the incidence of fetuses with minor skeletal anomalies was increased in 30, 35.6, or 66 mT (300, 356, or 660 mG) MF exposed groups [Stuchly et al, 1988;Huuskonen et al, 1993;Mevissen et al, 1994].…”

Testicular development evaluation in rats exposed to 60 Hz and 1 mT electromagnetic field

“…Nevertheless studies by Negishi et al . (2002) using low EMF intensity showed that rats exposed to 50 Hz magnetic field of 7, 70 or 350 µT for 22 h per day, during the preimplatation period (gestational day 0–7) or fetal organogenesis (gestational day 8–15) did not show effects on reproduction and embryo–fetal development. The exposure of rats to 60 Hz and 5, 83.3 or 500 µT magnetic field between the 6th and 20th day of gestation did not produce any biological significant effects on either dams or fetuses (Chung et al ., 2003).…”