foreign proteins, are intimately involved in local inflammation and tissue-repair processes. Both cell
types are produced in the hematopoietic tissues (located primarily in the bone marrow), and they have a
finite lifetime in the circulation before being replaced by new cells. The fluid portion of the blood is a
mixture of many chemicals with diverse metabolic functions-chemical transport, blood clotting, and
immune response are three examples.
Feedback systems that are only partially understood regulate both the cellular and non-cellular
composition of blood. For example, when an organism suffers a hemorrhage or an infection, the
hematopoietic tissues are mobilized to produce the required types of cells in the required numbers. As
we have seen in other areas, an EMF impact on the blood could arise from a primary effect on the
tissue itself, or from a secondary effect, with the field affecting the systems that regulate blood
composition.
The Cardiovascular System
An electrocardiogram (ECG) is a recording of the electrical changes that accompany the cardiac cycle;
a typical ECG is shown in Figure 7.1.
Fig. 7.1. The structure and origin of the electrocardiogram. A lengthened PR interval may indicate
impairment of conduction of impulses from the atrium to the ventricle; the QRS complex is associated
with interventricular conduction.
When mice were exposed for 1000 hours to 100 kv/m, 50 Hz, the PR interval and the QRS
duration were each lengthened by 19.5% (1). Guinea pigs exposed acutely (30 min.) to the same field
exhibited sinusal arrhythmia that began 10-20 minutes after removal from the field, and lasted 10
minutes (1).
Fischer et al. exposed rats to 50 and 5300 v/m, 50 Hz, and observed bradycardia (decreased
heart rate) at both field strengths as soon as 15 minutes after commencement of exposure (2). At the
lower field strength the effect was about 8%, and this decrease remained statistically significant (p <
0.01) after 2, 10, 21, and 50 days of continuous exposure. At 5 300 v/m the decrease in heart-rate after
15 minutes' exposure was about 16%: it was not seen following 2, 10, or 21 days exposure, but it was
present (about a 5% decrease) after 50 days.
Bradycardia was also reported in rabbits following exposure to 50 Hz electric fields (3); at 1000
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