Biologic effects of prolonged exposure to ELF electromagnetic fields in rats. I. 50 Hz electric fields.

A three-year investigation was conducted on the biological effects of high-intensity electric field exposures of rats for up to 18% of their life span. Two hundred and forty adult male rats, divided into groups of 20 animals each, were exposed at ground potential for 8 h/day at 25-kV/m and 100-kV/m 50-Hz electric fields or were sham exposed for 280, 440, and 1240 h. The corresponding ages at sacrifice were 140, 164, and 315 days. An additional group of 40 rats was investigated under similar experimental conditions after 440 h of exposure at floating potential. Independent of exposure duration, mode of grounding, and field strength, no statistical differences in body weight, morphology, and histology of the liver, heart, mesenteric lymph nodes, and blood variables (hematology and serum chemistry) were found in comparison with sham-exposed animals. Plasma levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone (TS) at sacrifice varied widely among experimental animals in the same group but did not differ in exposed compared with sham-exposed rats. A nonsignificant tendency toward a decrease in the testes/body weight ratio was found after 1240 h of exposure. Microscopic examination of a large number of specimens showed no quantitative or qualitative statistical differences in testes alterations either among exposed animals or between exposed and their corresponding sham-exposed groups. We conclude that 50-Hz electric field exposure, even of long duration at very high field strengths, does not induce harmful effects on tissues with high cellular turnover rates and does not impair the reproductive function of rats. Moreover, after exposure, all variables investigated were well within the normal physiological range.