Marconi's vision-radar-became a reality in the 1930's, and following World War II many other
practical uses for electromagnetic waves were developed.
Paralleling these developments was the birth and growth of the electrical power industry. From
a modest beginning in New York City in 1882. under the guidance of Thomas Edison, the industry
began the systematic electrification that resulted in a steady increase in power-line construction and in
the proliferation of the devices and appliances which they served.
The passage of electricity from a scientific curiosity to a role of major importance in society
(Table 10.1) resulted in a profound alteration in the earth's electromagnetic environment. From the
origin of life on earth to the beginning of the twentieth century this environment was determined by the
sun and other cosmic sources, and by the geomagnetic properties of the earth itself; the intensity was
extremely small even by the standards of today's ultrasensitive instrumentation. But by the beginning of
the last half of the twentieth century, man-made EMFs were the overwhelmingly dominant constituent
of the earth's electromagnetic environment. With the benefit of hindsight, we can now see that it was
dangerous to have made such a drastic alteration in our environment without first studying its potential
biological impact. But the fact is that the only immediately obvious effects of electricity are shock and
heating, and no experimental study before about 1960 and no theoretical study before about 1970
seriously suggested otherwise. It is therefore not surprising that, from a public health standpoint, the
best that can be said of the present artificial EMF levels in the environment in the U.S. is that they do
not cause shock or heating. Unfortunately, there may be public health consequences of environmental
EMFs that are not obvious and which, therefore, are not protected against by the unofficial U.S. EMF
exposure limit of 10,000 µW/cm2.
Table 10.1 SOME USES OF EMFs
Typical levels of artificial EMFs in the environment, their consequences, and the basis for our
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