Multigeneration reproductive toxicity assessment of 60-Hz magnetic fields using a continuous breeding protocol in rats

Male and female reproductive functions have been proposed as possibly sensi tive targets for the biological effects of 60-Hz (power frequency) magnetic fields (MF). However, experimental data relevant to this hypothesized asso ciation are very limited. in the present study, the "reproductive assessmen t by continuous breeding" design was used to identify possible effects of N IF exposure on reproductive performance, fetal development, and early postn atal growth in rats. Groups of age-matched Sprague-Dawley rats(40 breeding pairs/group) were exposed continuously (18.5 hr per day) to linearly polari zed, transient-free 60-Hz MF at field strengths of a Gauss (G; sham control ), 0.02 G, 2.0 G,or 10.0 G. An additional group of 40 breeding pairs receiv ed intermittent (1 hr on/1 hr off) exposure to 10.0 G fields. F-0 breeding pairs were exposed to MF or sham fields for 1 week prior to mating, during a 14-week period of cohabitation, and during a 3-week holding period after cohabitation. The duration of the cohabitation period was selected to be su fficient for the delivery of five litters in the sham control group. Pups f rom the final Fr litter from each breeding pair were exposed to NIF or sham fields until sexual maturity were cohabitated in NIF or sham fields for 7 days with nonsiblings from the same exposure group, and were held in the MF or sham fields for 22 days to permit delivery of F-2 pups for evaluation. No evidence of exposure-related toxicity was identified in any rat in the F -0, F-1, or F-2 generations. Fetal viability and body weights in all litter s of groups exposed to NIF were comparable to those of sham controls. No si gnificant differences between sham controls and MF-exposed groups were seen in any measure of reproductive performance (litters/breeding pair, percent fertile pairs, latency to parturition, litter size, or sex ratio) in eithe r the F-0 or F-1 generation. Exposure of Sprague-Dawley rats to 60-Hz MF st rengths of up to 10.0 G either during their peak reproductive period (F-0) or during gestation and throughout their life span (F-1) has no biologicall y significant effects on reproductive performance. These results do not sup port the hypothesis that exposure to pure, linearly polarized 60-Hz MF is a significant reproductive or developmental toxicant. (C) 1999 Wiley-Liss, I nc.