Epidemiological principles for EMF and EMR studies - Lincoln ...

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for a given external field intensity the induced internal currents are much higher
from the higher carrier frequencies.
Melatonin, produced by our body’s pineal gland, especially at night, is a very highly
potent antioxidant substance. Because of the EMF reduced melatonin mechanism,
Reiter and Robinson (1995), and with young children’s melatonin levels being low,
additional reduction by ELF fields at night could create a large impact on cancer
risk associated with the mean bedroom exposure. For some children the proximity
to power lines will dominate this magnetic field exposure. Other children live further
away from power lines but sleep in higher fields because of the configuration of the
household wiring. For example, the child’s bed is on the outside wall of the house,
near to where the power cable enters the house or is joined to the power switch
and fuse board, with fields in the range 4 to 12mG.
Power frequency (ELF) fields:
Power frequency (50/60 Hz, 1 Hz = 1 cycle per second) electric and magnetic fields
are produced around wires, appliances and equipment powered by electricity. The
electric field (E, V/m) is proportional to the voltage (V, volts) and the magnetic field
(B) is proportional to the current (i, Amperes). B, in milliGauss [mG] or microTesla
[µT]; 10 mG = 1 µT. In Figure 1 this is illustrated by showing the electric fields
produced when devices are plugged in and the voltage is applied. The magnetic
fields are added when the switch is turned on and the current flows to operate the
appliances, Figure 9.
Figure 9: The electric field results from being plugged in and a voltage is applied
between the plug and the "end" of the supplied device, left. When the
device is turned on the oscillating at 50/60 Hz current flows, creating an
electromagnetic field, Levitt (1995).
For power supplies these fields carry their energy in an oscillating current that
produces oscillating fields of 50 Hz or 60 Hz. Some European electric train and
tram systems use 16.7 Hz. In North America household supplies are 60 Hz and 120
V, whereas in the U.K., Europe, Australia and New Zealand, 50 Hz and 240 V
power supplies are used. This shows that the North American supplies are
associated with higher currents and higher magnetic fields for a given power
requirement.