Childhood cancer and power lines: Study had important omissions
BMJ 2005; 331 doi: https://doi.org/10.1136/bmj.331.7517.635-a (Published 15 September 2005) Cite this as: BMJ 2005;331:635All rapid responses
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Mr. Coghill writes,
"Magnetic fields from power lines will attenuate at 1/r3, whereas
electric fields may attenuate only at the simple reciprocal . . .".
It is unclear what this is supposed to mean. The electric field from
a point charge (or small electromagnetic-field source) diminishes linearly
with distance (1/r); therefore, the intensity of the field decreases as
1/r^2 (1/r-squared). The intensity governs energy transfer.
The magnetic field from a relatively short dipole diminishes as
1/r^2, implying intensity loss as 1/r^3.
However, the geometry of the source determines the energy transfer
much more strongly than point estimates would imply: The electric field
from long LINE of charge (for example, a powerline oscillating as slowly
as 50 Hz) may have a field which is almost constant with distance and an
intensity which falls off only as 1/r or less.
Only if the angle subtended by the source is small as measured at the
absorber can a point-source estimate of field or intensity be used
accurately.
In addition, the geometry of the absorber is important, too: The
body can act as a VERY effective 3-dimensional antenna for wavelengths
near the body size. This doesn't apply for the power frequencies, but it
does become relevant when considering microwave frequencies (from cell
phones and other communicators) using the power lines as transmission
conduits and radiators.
I'd like to add that I am trying to make a technical point here; I do
not understand how an electric field or electromagnetic irradiation could
be oncogenic. I think that a good explanation of the proposed mechanism
would be far more useful than a lot of poorly controlled and arbitrarily
selected epidemiological data.
Competing interests:
None declared
Competing interests: No competing interests
Coghill's Challenge
Dear Sirs,
Your readers may wish to be aware that Roger Coghill, since 1993 has
been issuing what he refers to as Coghill's challenge on his website
(http://www.cogreslab.co.uk/cog_chall.asp)
This states:
"Place any human infant of less than three months age to sleep each
night for at least eight hours in an ELF electric field of 100 Volts per
metre for thirty days. My studies predict that child will die, or become
so seriously ill that the test will have to be called off. The NRPB and
the power utilities' investigation levels by contrast predict there will
be no adverse effect.
I will personally bet any NRPB member of staff or any any electric
power utility worker around the world £2000 (or US$3000) willing to do
this experiment, that my prediction will prove correct."
How can anyone offer a financial inducement to carry out an
action which he predicts will lead to the death or serious harm of an
infant?
Yours sincerely,
Kenneth Campbell
MSc (Clinical Oncology)
Competing interests:
None declared
Competing interests: No competing interests