v/m, the heart-rate decreased by about 9% after 30-60 days. The field also brought about a reduction in
the amplitude of the ECG: the P, R, and T waves were each reduced by 40-50%. Another effect
induced by the 1000-v/m field was a reduction in the physiological reserve capacity of the rabbits.
When the control animals were forced to remain in an erect position the heart-rate increased by 22-
32%, but among the animals exposed to the field the range was 34-46%. No effects on heart action
were seen at 500 or 100 v/m.
Microwave EMFs have produced alterations in heart function that are remarkably similar to the
changes observed at 50 Hz (4). Bradycardia was observed in rabbits after 2 weeks', but not after 2
months', exposure to 0.5 and 3 v/m. The amplitudes of the P, R, and T waves in the exposed animals
were decreased by about 50% following 2 weeks' and 2 months' exposure. When pituitrin was injected
intravenously into control and exposed (1.5 mo.) rabbits, the resulting coronary insufficiency was
stronger, and disappeared more slowly, in the exposed animals.
In preliminary studies, dogs were exposed to 15 kv/m, 60 Hz, for 5 hours to determine whether
such exposure altered the physiological response to a controlled hemorrhage (10 ml/kg, over a 3-
minute period) (5). The cardiovascular changes (p < 0.05) at the end of the hemorrhage were mean
arterial pressure fell an average of 5.9 mmHg in the control group and 16 mmHg in the exposed group;
arterial pulse pressure fell 0.9 mmHg in the control group and 10.9 mmHg in the exposed group;
average heart-rate decreased 9.3 beats per minute in the control group, but increased 57. 5 beats per
minute in the exposed group.
Heart action is one of several factors that influence arterial blood pressure. In studies involving
the exposure of rats to 153 µW/cm2, 3 GHz both a short-term hypertensive effect and a long-term
hypotensive effect were reported (6). During the first month of the 1 hour/day exposure regimen an
increased arterial pressure was seen: beginning with the second month's exposure, the arterial pressure
of the exposed animals was consistently lower than that of the controls for the next 5 months. When the
exposure was terminated the arterial-pressure difference disappeared within about 1 month.
Changes have been reported in the cellular composition of the blood of rats, mice, dogs, guinea
pigs, and rabbits following exposure to both high and low frequency EMFs (7-15).
Graves (7) exposed mice continuously to 25 and 50 kv/m for 6 weeks and found that the white
blood cell count (WBC) was increased by 20% and 66% respectively. The red blood cell count (RBC)
decreased by 6% and 12% at the respective fields, but these changes were not reported statistically
significant.
Rats exposed intermittently (30 min/day) to 100 kv/m, 50° Hz, for 8 weeks, exhibited elevated
neutrophil levels and depressed Iymphocyte levels (8). The same results were found following 2, 5, and
7 weeks' exposure at 5 hours/day. In dogs, alteration of the blood profile was seen following exposure
at 10-25 kv/m (8).
Meda (9) found a Iymphocyte decrease and a neutrophil and eosinophil increase in rats after a
single 6-hour exposure to 100 kv/m, 50 Hz. A similar blood picture was found in mice after 500- and
1000-hour exposures to 100 kv/m (9). A significant increase in WBC was found in rabbits that had
been exposed to 50 kv/m, 50 Hz, for 3 months (14).
As has been the case with almost all biological indicators, the time course of the changes in
blood parameters following EMF exposure was not the same in each test animal (11). Guinea pigs were
exposed to 3GHz, 10 min/day, for 30 days (11), and both the irradiated and the sham-exposed animals
were sampled before and after each daily exposure bout. The sham-exposed group revealed no
ELECTROMAGNETISM & LIFE - 93