Rats were exposed for 7 hours/day to 50 and 500 µW/cm2, 2.4 GHz (total exposure of 1 and 10 days at the higher and lower intensities respectively) (41). At 50 µW/cm2, the number of chromosomal abnormalities increased by 55 % compared to the controls when assayed 18 hours after the end of the exposure period; 2 weeks after exposure the increase was 150% . Eighteen hours following exposure at 500 µW/cm2, the number of chromosomal abnormalities was more than 5 times that of the controls, and it remained elevated (340%) even after z weeks. In a comparable study (42) (3 GHz, 3 500 µW/cm2, 3 hr./day for 3 mo.) mitotic disorders were seen in guinea-pig and rabbit Iymphocytes.
We studied the mutagenetic effect of 60 Hz electric fields on the cells of a free-floating peritoneal-cavity tumor implanted in mature female mice (43, 44). The tumor was propagated in control mice by injecting the host intraperitoneally with tumor-containing fluid that had been freshly removed from an unexposed animal. After 14 days, a few drops of tumor were removed and the tumor cells were processed for chromosomal analysis. Tumor propagation in the 2-week exposed groups was identical except that the mice were exposed to DC electric fields of 8-16 kv/m. The tumor cells were ordinarily lethal to the host about 3 weeks after injection. To propagate the tumor for longer periods it was therefore necessary to transplant it to a new host every 7-14 days. Consequently, tumor cells exposed for 4-15 weeks required serial inoculations into 2-9 continuously exposed mice. On the day the chromosomal analysis was to be performed, the host was injected with colcemid to arrest cell division in metaphase and allow direct visualization of the chromosomes. Cells exposed to horizontal EMFs for 2 weeks exhibited almost a threefold increase in the percentage of abnormal chromosomes when compared to control cells (Table 8.9); cells exposed to vertical EMFs for the same period, however, had a percentage of abnormal chromosomes comparable to that of the control cells. Extended exposure to both EMFs appeared to produce opposite results. The percentage of cells with abnormal chromosomes tended to decrease systematically in the horizontal EMF but increase systematically in the vertical EMF. The number of mice analyzed prohibited a precise determination of the dependence on exposure time, and in both cases, when the results were averaged over the entire extended exposure period (4-15 weeks for the horizontal EMFs, and 6-15 weeks for the vertical EMFs), no statistically significant results were seen (Table 8.9).
Table 8 .9. EFFECT OF DC ELECTRIC FIELDS IN THE RANGE 8-1 6 kv/m ON THE INCIDENCE OF CHROMOSOMAL ABERRATIONS IN EHRLICH ASCITES TUMOR CELLS EXPOSED IN VIVO
EMFs have also been reported to produce chromosomal aberrations in nonsomatic cells (45). Adult male mice were exposed 1 hour/day for 2 weeks to 9.4 GHz, 100-10,000 µW/cm2. After exposure, the animals were sacrificed and the sperm-cell chromosomes were analyzed. At each intensity, there was an increase in both translocations and univalent chromosome pairs.
Mutagenetic effects of EMFs have been reported in in vitro studies, and in studies involving insects and plants (46-51). Rat kangaroo cells exposed in vitro to 2.4 GHz for 10-30 minutes exhibited chromosomal aberrations similar to those induced by X-rays (46). The results also that the EMF disrupted RNA synthesis and reduced protein production and cell proliferation. EMFs in the 15-40 MHz range and at K band (23 GHz) caused chromosomal abnormalities in Chinese hamster lung cells in culture (47). When cells of the same type were exposed as a monolayer for 15 minutes to a DC magnetic field of 15,000 gauss, it was found that of the 400 metaphase cells examined in the 24-hour period after exposure, approximately 3% exhibited a chromosomal aberration; this rate was 6 times higher than that seen in the controls (48). Exposure of monkey epithelial cells to 7000 µW/cm2, 2.9 GHz also caused chromosomal abnormalities (49).
Radiowave pulses (20-30 MHz) applied to male Drosophila for 5-6 minutes resulted in the production of numerous mutations in the off-spring, including singed bristle, white eye, spotted eye, yellow body, and blister wing (50). The genetic effect exerted on the male germ cells was similar to that seen from the application of ionizing radiation (50). An EMFs has also been reported in plants (51).