Teratological assessment of exposure to time-varying magnetic field.

A teratological assessment was performed using rats that were exposed to an alternating magnetic field. The magnetic field had a sawtooth waveform similar to that produced by video display terminals (VDTs). Female rats were exposed 2 weeks prior to and throughout pregnancy at a rate of 7 h/day. Three intensities of magnetic field (5.7, 23 or 66 microT) were used. All of these field intensities were much greater than those to which VDT users are exposed. A slight but statistically significant decrease in maternal lymphocyte count for the highest intensity field was found as compared with the control group. However, the lymphocyte count was within the normal range, and the observed changes in hematological parameters were considered mild. No other maternal or fetal parameters that were examined showed a significant difference for any of the three field intensities. Where minor variations in skeleton development were observed they were known to be the common "noise" that appears in every teratological evaluation.