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LETTERS: Roger W Coghill Childhood cancer and power lines: Study had important omissions BMJ 2005; 331: 635-a [Full text]

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Apparent Error in Physics

John M. Williams   (17 September 2005)

Coghill's Challenge

Kenneth Campbell   (30 October 2005)

Apparent Error in Physics 17 September 2005
John M. Williams, Business Owner P. O. Box 2697, Redwood City, CA 94064 Send response to journal: Re: Apparent Error in Physics	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
Coghill's Challenge 30 October 2005
Kenneth Campbell, Clinical Information Officer, Leukaemia Research Fund 43 Great Ormond Street, London, WC1N 3JJ Send response to journal: Re: 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